Publications

generation of reassortants between african arenaviruses.	lassa (las) and mopeia (mop) viruses are african arenaviruses which are carried by wild rodents and occasionally transferred to humans. in humans and nonhuman primates, lassa causes mortality in 60% of untreated cases, whereas mopeia does not cause mortality and has been known to protect monkeys from lethal challenge with lassa. these two african arenaviruses also differ in their lethality for suckling outbred mice and in their plaque sizes under agar overlay. mop virus induces small plaques and ...	1992	1585636
rats, fever and sudden deafness in sierra leone.		1992	1604723
baculovirus expression of the glycoprotein gene of lassa virus and characterization of the recombinant protein.	a recombinant baculovirus was constructed that expresses the glycoprotein gene of lassa virus (josiah strain) under the transcriptional control of the polyhedrin promoter. the expressed protein (b-lsgpc) comigrated with the authentic viral glycoprotein as observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page), was reactive with monoclonal antibodies (mabs) in western blots, and was glycosylated. although the recombinant protein was not processed into the mature glycopro ...	1992	1413995
the fusion of artificial lipid membranes induced by the synthetic arenavirus 'fusion peptide'.	the fusing activity of the synthetic 23 amino-acid fragment (fusion peptide, fp) of the fusion protein of the lassa arenavirus membrane was tested in a model liposomal system. the resonance energy transfer between two fluorescent phospholipid probes was monitored in order to detect dioleoylphosphatidylcholine liposome fusion induced by the peptide. fusion rates were compared at different ph values, ionic strength and calcium concentrations. fp demonstrated fusing activity at ph 4.5-5.5, indicati ...	1992	1390849
lassa fever encephalopathy: clinical and laboratory findings.	clinical and laboratory findings are reported in nine patients who developed acute encephalopathy during the course of lassa fever. the encephalopathy manifested 3-17 days after disease onset with confusion, followed rapidly by tremor (seven patients), grand mal convulsions (seven), abnormal posturing (three) and coma (eight); focal neurological signs and evidence of raised intracranial pressure were not seen. eight patients died, most commonly from respiratory arrest following a protracted fit. ...	1992	1597876
inactivated lassa virus elicits a non protective immune response in rhesus monkeys.	we attempted to protect three rhesus monkeys from lassa fever by vaccination with a preparation of purified whole lassa virus which had been inactivated by gamma irradiation. the vaccinated monkeys developed antibodies against the three major viral proteins of lassa virus demonstrated by radioimmunoprecipitation. when the three vaccinated monkeys and two unvaccinated control monkeys were challenged all five became severely ill and died. prior to death a secondary, high-titer antibody response to ...	1992	1619397
[fusion of artificial lipid membranes induced by synthetic "fusion peptide" of arenaviruses].	the fusing capacity of lipid membranes of a synthetic 23-member peptide was studied. this hydrophobic peptide represents an analog of a predicted functional site ("fusion peptide") of the gp2 envelope protein of the lassa virus (family arenaviridae). fusion of small monolayer liposomes was detected by the method of resonance energy transfer between the fluorescent derivatives of the lipid, nbd-pe (donor) and rd-pe (acceptor). using this peptide, the ph-dependent fusing activity was found in lipo ...	1991	1912065
sequence analysis of the s rna of the african arenavirus mopeia: an unusual secondary structure feature in the intergenic region.	mopeia virus is an apparently nonpathogenic african arenavirus which can protect animals from subsequent challenge by the closely related lassa virus. as a step toward understanding these differences in pathogenicity and the means by which mopeia virus infection can protect against subsequent lassa virus infection, cdna clones corresponding to 3419 nucleotides of mopeia virus s rna were isolated and sequenced. two open reading frames, encoding the glycoprotein precursor (gpc) and nucleocapsid (n ...	1991	1989384
antigenic relatedness between arenaviruses defined at the epitope level by monoclonal antibodies.	monoclonal antibodies (mabs) were produced against two african arenaviruses, lassa virus and mopeia virus. competitive binding analysis of mabs identified four antigenic sites on the nucleoprotein (np), two on glycoprotein 1 (gp1) and six on glycoprotein 2 (gp2) of the josiah strain of lassa virus. 64 virus isolates from western, central and southern africa were all consistently distinguishable by mabs to certain epitopic sites on gp1, gp2 and np viral proteins. furthermore, mabs to lassa virus ...	1991	1706408
[identification of a protective epitope--a fragment of lassa virus nucleoprotein].	several peptides from lassa virus glyco- and nucleoproteins were predicted as probable t-cell epitopes. their synthesis was performed by solid phase method. the study of possible protective effect in vivo with lassa-sensitive cba mice revealed protective epitope within the 277-303 nucleoprotein region. further studies reduced the protective epitope structure to the 287-300 nucleoprotein fragment.	1991	1716105
[the therapeutic efficacy of ribamidil and virazole in experimental lassa fever in monkeys].	the therapeutic efficacy of ribamydil and virasol was evaluated in experimental lassa fever in monkeys which received these drugs at various intervals after the onset of the clinical illness. ribamydil or virasol administered in the first day of fever protected from death 60% to 66% of the infected animals, but when the drugs were given 2 days after the onset of fever the number of survivors declined to 0.20%. when the treatment was started 4 days after the onset of fever none of the drugs preve ...	1991	1858356
[the production of antibody-producing hybridomas to the lassa virus].	the work deals with obtaining hybrid cell lines producing monoclonal antibodies to lassa arenavirus. to obtain preparations for the screening of hybridomas by indirect immunofluorescence techniques, the dynamics of the accumulation of lassa virus antigen in cell cultures vero and 4647 was studied. the maximum accumulation of the virus antigen in vero cells was shown to occur on day 3 after inoculation with a dose of 1.0 pfu/ml. the influence of different doses of gamma radiation on the infectiou ...	1991	1872102
[experimental lassa fever in hamadryas baboons].	intramuscular or aerogenic inoculation of baboons with lassa virus reproduced a severe form of the disease which clinically, pathoanatomically and virologically resembles the severe form of human lassa fever reported in the literature. the severity of monkey infection is demonstrated by rapid development of symptoms of general toxicity in the presence of fever, manifestations of hemorrhagic diathesis, high level of viremia and isolation of the causative agent from nasopharyngeal washings.	1991	1882523
[the isolation and characteristics of reassortants between the lassa and mopeia arenaviruses].	reassortants with a mixed phenotype were produced by combined inoculation of vero cells with lassa and mopeya viruses. these reassortants produced small plaques (mopeya virus phenotype) and were not pathogenic for newborn mice (lassa virus phenotype). the genotype of the reassortants was studied by dot hybridization experiments on filters using cdna-probes differentiating genome segments of these viruses. the reassortants were shown to have mopeya virus l-rna and lassa virus s-rna.	1991	1882522
exchange transfusion of a patient with fulminant lassa fever.	we report a patient with fulminant lassa fever who responded dramatically to a 2.5-litre exchange transfusion of whole blood. on admission he was semicomatose with facial oedema and oral haemorrhage; his platelets showed markedly depressed aggregation to adp; and his plasma inhibited the aggregation responses of normal platelets in vitro. exchange transfusion resulted in rapid clinical improvement, recovery of platelet function, and disappearance of platelet-inhibitory activity in plasma. the pa ...	1991	2041853
nucleotide sequence of the s rna of lassa virus (nigerian strain) and comparative analysis of arenavirus gene products.	the nucleotide sequence of the small (s) genomic rna of lassa virus (strain ga391, of nigerian origin) has been determined. the rna has features which conform to those seen in most other arenavirus s rnas which have been characterised, including conserved terminal sequences, an ambisense arrangement of the coding regions for the precursor glycoprotein (gpc) and nucleocapsid (n) proteins and an intergenic region capable of forming a base-paired "hairpin" structure. comparison of the nucleotide se ...	1991	2042397
simultaneous expression of the lassa virus n and gpc genes from a single recombinant vaccinia virus.	a new transfer vector was constructed that directs the insertion of two heterologous genes into the vaccinia virus thymidine kinase (tk) gene during a single recombination event. this vector, pdavac2, contains bidirectional vaccinia p7.5 early/late promoter elements and two unique cloning sites. cdna clones containing the complete coding sequences for the lassa virus (josiah strain) nucleoprotein (n) and glycoprotein (gpc) genes were inserted into the vaccinia tk gene using this transfer vector. ...	1991	2042398
[the cultivation and physicochemical properties of the josiah strain of the lassa virus].	data on the stability of lassa virus, josia strain, isolated from man to the effect of physicochemical factors (heating at 50 degrees c, solutions of urea and formalin of various concentrations, uv irradiation) as well as on the time course of this strain reproduction in cell lines of different origins are presented. recommendations for lowering of reactogenicity of the virus-containing material are given. the experimental results must be taken into consideration in the development and manufactu ...	1990	2256317
[experimental lassa infection in monkeys and its treatment with ribamidil].		1990	2082557
[immunization of rabbits with lassa virus].	the parameters of humoral and cell-mediated immunity after inoculation of the infectious and inactivated antigen of lassa virus to rabbits which are insusceptible to this infection were studied. lassa virus antigen was demonstrated to induce synthesis of specific antibodies in rabbits the level of which was proportional to the dose of inoculation and the time of immunization. the results of leukocyte blastogenesis test and delayed type hypersensitivity test confirm the development of sensitizati ...	1990	2363276
[lysosomotropic agents inhibit the penetration of arenaviruses into a culture of bhk-21 and vero cells].	lysosomotropic agents (nh4cl, amantadine, chloroquine, monensin) which prevent acidification of intracellular vacuoles, when introduced into the culture medium before or during inoculation of cells (bhk-21, vero) with arenaviruses inhibit reproduction of these viruses completely or significantly. mozambique virus proved to be 10 times more sensitive to the effect of lysosomotropic agents than pichinde and lassa viruses. thus, arenaviruses have a ph-dependent stage at the beginning of the reprodu ...	1990	2389568
[comparative evaluation of the antiviral efficacy of virazole and ribamidil in experimental lassa fever in monkeys].	lassa virus administered to monkeys aerogenically induced in these laboratory animals a fatal disease modelling the severe course of human lassa fever. it was demonstrated experimentally that ribamydil, a soviet analogue of virasol, as well as foreign commercial virasol was therapeutically effective in experimental lassa fever in aerogenically infected monkeys.	1990	2389569
[the interferon-inducing activity of the lassa virus in the body of inbred mice].	the level and the time course of accumulation of endogenous interferon were studied in the blood sera of mice experimentally infected with lassa virus by the intracerebral route. the level of interferon correlated with case-fatality rate of the animals which may be important for the understanding of the pathogenesis of arenavirus infections.	1990	1699360
[recombinant monoclonal antibodies to the lassa virus: the formation of reactive paratopes].	eighteen hybrid lines secreting recombinant monoclonal antibodies to lassa virus were produced by fusion of mouse splenocytes with antibody-secreting x-63 myeloma cells. interrelations between the structure and reactivity of the antibodies were studied by different serological and immunochemical methods. monoclonal antibodies were divided into different groups according to their serological properties and macromolecular structure. a comparative analysis of the structure and reactivity of the rec ...	1990	2082553
acute sensorineural deafness in lassa fever.	a prospective audiometric evaluation of 69 hospitalized febrile patients in sierra leone, west africa, revealed a sensorineural hearing deficit (snhd) in 14 (29%) of 49 confirmed cases of lassa fever and in 0 of 20 febrile controls. an snhd was present in nine (17.6%) of 51 people who had evidence of previous lassa virus infection. twenty-six of 32 local residents who had previously sustained a sudden deafness had antibody titers to lassa virus of 16 or greater, compared with six of 32 matched c ...	1990	2214077
[the comparative characteristics of the genetic traits of the lassa and mopeia viruses].		1990	2219860
[the isolation and characteristics of recombinant monoclonal antibodies to the lassa virus].	recombinant monoclonal antibodies to lassa virus were produced. the reactivity of the monoclonal antibodies was studied by indirect fluorescence antibody (ifa) technique, enzyme-linked immunosorbent assay (elisa), and radioimmunoprecipitation method. the observed reactivity did not correlate with igg isotyping groups.	1990	2267781
lassa virus glycoproteins: antigenic and immunogenic properties of synthetic peptides to gp1.	synthetic peptides corresponding to predicted lassa virus gp1 glycoprotein b-epitopes were used to study the antigenicity and immunogenicity of the protein. elisa results showed that guinea pig polyclonal anti-lassa virus serum bound effectively to peptides corresponding to amino acid residues 119-133 and 164-176 of the gp1 protein. essentially it did not react to a peptide corresponding to gp1 amino acid residues 234-256. sera obtained against peptides representing amino acid residues 119-133 a ...	1990	1701079
[the detection of a presumed fusion peptide comprising the surface glycoproteins of arenaviruses].		1990	2267784
prediction of arenavirus fusion peptides on the basis of computer analysis of envelope protein sequences.	theoretical search and selection criteria for putative fusion peptides of enveloped viruses are proposed. arenavirus fusion peptides are predicted on the basis of computer-assisted analysis of amino acid sequences of arenavirus envelope proteins and elements of their secondary and tertiary structure. accordingly, two regions of gp2 surface protein from 5 viruses of arenaviridae family have been detected with properties typical of fusion peptides of other enveloped viruses. one region, named pept ...	1990	2387394
expression of the lassa virus nucleocapsid protein in insect cells infected with a recombinant baculovirus: application to diagnostic assays for lassa virus infection.	the coding region of the gene for the nucleocapsid protein of lassa virus has been inserted into the genome of autographa californica nuclear polyhedrosis virus (acnpv) using the transfer vector pacym1, so that expression of the foreign dna is under the control of the promoter of the acnpv polyhedrin gene. infection of cultured spodoptera frugiperda cells with recombinant virus resulted in the synthesis of high levels of a protein that was indistinguishable from the authentic lassa virus protein ...	1990	2406367
detection of lassa virus rna in specimens from patients with lassa fever by using the polymerase chain reaction.	suitable oligonucleotide primers and probes were synthesized to amplify lassa virus (josiah strain)-specific nucleoprotein and glycoprotein gene fragments by using reverse transcription combined with the polymerase chain reaction (pcr). our primers did not amplify the related lymphocytic choriomeningitis virus. by using pcr, about 50 50% tissue culture infective doses could be detected in the supernatant of infected cells. furthermore, in all five serum specimens and four of five urine specimens ...	1990	2279999
early events in arenavirus replication are sensitive to lysosomotropic compounds.	lysosomotropic compounds (ammonium chloride, chloroquine, amantadine, monensin) effectively inhibited the replication of pichinde, mopeia, and lassa viruses in bhk-21 and vero cells. the inhibitory effect was dependent upon the time of drug addition and was most effective when the drugs were added 1 h before the viral adsorption. the drugs had no direct effect on the infectious viruses nor on adsorption of the arenaviruses. these results suggest that the arenaviruses enter cells by adsorptive en ...	1989	2923547
a plasma inhibitor of platelet aggregation in patients with lassa fever.	previous studies have shown that haemorrhage in lassa fever is associated with abnormal in vitro platelet aggregation and a high mortality. in sierra leone we studied platelet aggregation in healthy local subjects, patients with laboratory-confirmed lassa fever and febrile patients in whom lassa virus infection was excluded. there were no significant differences in the mean platelet counts of these groups. patients with fulminant lassa virus infection showed a gross depression of in-vitro platel ...	1989	2775659
[characteristics of the immune response in mice immunized with the inactivated lassa virus].	the influence of humoral and cell-mediated immunity on the formation of resistance in mice immunized with inactivated lassa virus was evaluated. as a result of immunization, both nonspecific and specific immune response developed, the main rule in the formation of resistance belonging to specific immunity.	1989	2474905
replication of hemorrhagic fever viruses in monocytic cells.	monocytes play a central role in protection against many viruses. in some infections they are target cells for viral replication. there is increasing evidence that these cells may also be important in regulation of hemostasis. the part played by monocytic cells in the pathogenesis of hemorrhage in the viral hemorrhagic fevers is presently uncertain. monocytes and monocytic cell lines have been used to investigate the ability of viruses to infect these cells in vitro. several factors may affect t ...	1989	2665010
nucleotide sequence of the lassa virus (josiah strain) s genome rna and amino acid sequence comparison of the n and gpc proteins to other arenaviruses.	the complete nucleotide sequence of the s genome rna of the josiah strain of lassa virus was determined from cloned cdna. the s rna is 3402 nucleotides long with a calculated molecular weight of 1.09 x 10(6) da. the nucleotide base composition is 26.84% adenine, 21.40% guanine, 22.75% cytosine, and 29.01% uridine. the 5' and 3' terminal nucleotide sequences are conserved and complimentary for 19 nucleotides, the nucleoprotein and glycoprotein genes are arranged in ambisense coding strategy, and ...	1989	2916333
antibody prevalence against haemorrhagic fever viruses in randomized representative central african populations.	between 1985 and 1987, 5,070 randomly selected persons living in 6 central african countries (cameroon, central african republic, chad, congo, equatorial guinea and gabon) were checked for serological evidence of haemorrhagic fever. rural and urban areas were studied, including ecoclimatic zones ranging from dry savana to tropical rain forest. virus-reactive antibodies were found with all antigens tested, and the global prevalence of positive sera was distributed as follows: crimean-congo haemor ...	1989	2505350
antibodies to haemorrhagic fever viruses in madagascar populations.	sera of 381 adult people from 5 areas in madagascar were tested by the indirect immunofluorescence method for antibodies against congo-crimean haemorrhagic fever and rift valley fever viruses (bunyaviridae), ebola (strains zaire and sudan) and marburg viruses (filoviridae), and lassa virus (arenaviridae). the highest prevalence rate was that of ebola virus (4.5%). as no haemorrhagic syndrome has been found associated with this virus, the possible presence of a less pathogenic, antigenically rela ...	1989	2515626
[effect of immunosuppression on the development and outcome of an acute infection in mice caused by administration of the lassa virus].	in experimental infection of mice with lassa virus, the infectious virus could be detected in all the organs and brain tissues tested. histopathological lesions were demonstrated in cerebral and spinal cord tissues only. roentgen irradiation in a dose of 500 r and cyclophosphamide protected mice against a lethal lassa virus dose. cyclosporin a in various doses exerted no effect on the outcome of the acute infection. the adoptive transfer of splenocytes from mouse donors inoculated intraperitonea ...	1989	2763513
preparation and biochemical characterization of lassa virus subvirion fractions.	14c-labelled lassa virus was purified by isopycnic centrifugation and split to subvirion fractions. the purified virus was treated with nonionic detergents nonidet p-40 (np-40) and with octylglycoside. after ultracentrifugation in urographin density gradient, two subvirion fractions with buoyant density of 1.24-1.26 and 1.08-1.10 g/cm3 were obtained. the first fraction corresponded to the nucleocapsid of lassa virus: it contained a protein with molecular mass of 60 kda, the l and s segments of t ...	1989	2569820
identification of lassa fever virus infection with recombinant nucleocapsid protein antigen.		1989	2572935
[lassa and mozambique viruses: cross protection in experiments on mice and action of immunosuppressants on experimental infections].	the pathogenicity of mozambique virus for random-bred mice and cba mice was studied. in contrast to lassa virus, intracerebral inoculation of newborn zandom-bred mice with mozambique virus (1000 pfu/mouse) results in death of the animals. the pathogenic properties of both viruses for adult cba mice were found to be similar: intracerebral inoculation of the viruses caused death of the animals within 6-8 days, but not intraperitoneal inoculation. with the latter, they produced a population of immu ...	1989	2609647
[dynamics of antigen and antibody accumulation in adult mice, infected with lassa virus].		1989	2658319
[the first imported case of lassa fever in japan].		1989	2724572
protection of guinea pigs from lassa fever by vaccinia virus recombinants expressing the nucleoprotein or the envelope glycoproteins of lassa virus.	a recombinant vaccinia virus that expresses the nucleoprotein gene of lassa virus (josiah strain) under the control of the p7.5 promoter was constructed using the lacz coexpression transfer vector psc11. southern blot analysis demonstrated that recombination of the sequences inserted within the thymidine kinase gene of the transfer vector into the hindiii j fragment of vaccina virus genomic dna occurred properly. a 63-kda protein identical in electrophoretic mobility to authentic lassa nucleopro ...	1989	2741340
epitope mapping of the lassa virus nucleoprotein using monoclonal anti-nucleocapsid antibodies.	monoclonal antibodies with differing specificity were prepared against the josiah strain of the lassa virus. all monoclonal antibodies were characterized by subclass determination and the immunofluorescence test against lassa, lcm (we & arm strain), junin, machupo, and other arenavirus antigens. in radioimmune precipitation tests using purified lassa virus antigen all monoclonal antibodies precipitated a single band of 60 kd, specific for the viral nucleoprotein (p 60). three domains (a, b, c) w ...	1989	2476109
protection of rhesus monkeys from fatal lassa fever by vaccination with a recombinant vaccinia virus containing the lassa virus glycoprotein gene.	lassa fever is an acute febrile disease of west africa, where there are as many as 300,000 infections a year and an estimated 3000 deaths. as control of the rodent host is impracticable at present, the best immediate prospect is vaccination. we tested as potential vaccines in rhesus monkeys a closely related virus, mopeia virus (two monkeys), and a recombinant vaccinia virus containing the lassa virus glycoprotein gene, v-lsgpc (four monkeys). two monkeys vaccinated with the new york board of he ...	1989	2911575
viral hemorrhagic fever antibodies in nigerian populations.	using the immunofluorescence test, a serosurvey for antibodies to five viral agents associated with hemorrhagic febrile infections was conducted with 1,677 human sera from different parts of nigeria. three hundred fifty-seven (21.3%) were positive for lassa virus antibody, while antibodies to rift valley fever virus were detected in 42 (2.5%) of the sera. testing for rift valley fever virus antibody was confirmed by plaque reduction neutralization test. antibodies to ebola and marburg viruses we ...	1988	3128130
lassa fever: epidemiology, therapy and vaccine development.		1988	3138361
lassa fever virus in senegal.		1988	3343533
[the indirect hemagglutination reaction for the detection of the lassa virus].		1988	3195147
immune serum increases arenavirus replication in monocytes.	the u937 monocytic cell line was used to determine whether antibodies could facilitate infection and replication of the arenaviruses, pichinde virus (pv) and lassa fever virus (lfv). when high dilutions of pv-immune serum were added to cultures simultaneously with pv inoculum, virus replication was dramatically (1000-fold) increased. low dilutions of this antiserum neutralized the virus. lfv also replicated in u937 cells. the presence of lfv-specific immune serum in the growth medium increased t ...	1988	3292697
construction of a recombinant vaccinia virus expressing the lassa virus glycoprotein gene and protection of guinea pigs from a lethal lassa virus infection.	a cloned cdna (1.65 kb) containing the complete glycoprotein gene of the josiah strain of lassa virus was inserted into the thymidine kinase (tk) gene of the new york board of health (wyeth) strain of vaccinia virus. the lassa virus glycoprotein precursor, gpc, and the posttranslational cleavage products, g1 and g2, were shown by western blot analysis to be properly expressed in cells infected with the recombinant virus. northern blot hybridization of total cytoplasmic rna extracted from recombi ...	1988	3354260
identification of messenger rna for nucleocapsid protein of lassa virus in infected cells.	single-stranded rnas from lassa virus-infected cells were fractionated by affinity chromatography on an oligo(dt)-cellulose column as well as by sucrose gradient centrifugation. fractionated rnas were translated in rabbit reticulocyte lysates, and translation products were precipitated with monoclonal antibodies to the nucleocapsid protein of lassa virus. it has been shown that mrna for the nucleocapsid protein is 15-16s and the rna does not contain long if any poly(a) sequences.	1988	2900821
[template activity of poly(a+) and poly(a-) messenger rna of pathogenic arenaviruses].	the total rna from cells infected with machupo and lassa viruses as well as poly(a+) and poly(a-) fractions of the rna were translated in the cell-free protein synthesizing system from rabbit reticulocytes. the translated products were treated with specific antibodies and analyzed in polyacrylamide gel electrophoresis. only poly(a-) fraction of rna coded for the synthesis of np protein in vitro. the mrnas for np protein of machupo and lassa viruses are supposed to contain no poly(a) sequences at ...	1988	2848192
fine mapping of a peptide sequence containing an antigenic site conserved among arenaviruses.	the lymphocytic choriomeningitis virus (lcmv) structural glycoproteins gp-1 (mr 44k) and gp-2 (mr 35k) are encoded on a single intracellular proteolytic cleavage precursor glycoprotein, gp-c (mr 76k). we have used a series of synthetic peptides derived from the deduced amino acid sequence of lcmv gp-c to define an antigenic site containing two topographically overlapping epitopes. three mouse monoclonal antibodies directed against two epitopes on gp-2 were assayed for binding in solution phase b ...	1988	2452517
genetic variation among lassa and lassa-related arenaviruses analysed by t1-oligonucleotide mapping.	total rna and small rna species of several african arenavirus strains have been studied by t1-oligonucleotide mapping. genetic heterogeneity is observed and discussed on the basis of evolutionary biology of the lassa complex.	1988	3145759
[electron microscopic study of lassa virus].	ultrafiltration through hollow fibrous filters followed by purification in interrupted and linear urografin gradients yielded a lassa virus suspension of high concentration. the use of gamma-irradiation for inactivation of the frozen virus suspension (-70 degrees c) caused no apparent structural changes of virions and made it possible to examine lassa virus in electron microscope by negative staining. the observed virus particles in their morphology and sizes did not differ from previously descr ...	1988	3369149
[clinico-epidemiologic and laboratory research on hemorrhagic fevers in guinea].	in 1982-1983, were reported the cases of haemorrhagic fevers among populations living in the madina-ula district of guinea. clinico-epidemiological and serological studies (experimental studies) reveal into presumption of ebola and lassa fever viruses significance in the etiology of the disease outbreaks. antibodies to ebola virus were recognized in 19% from total number of sweating reconvalescent patients with the same clinical features, in order to 8% in healthy local populations. antibodies t ...	1987	3440310
pediatric lassa fever: a review of 33 liberian cases.	thirty-three cases of pediatric lassa fever were identified at curran lutheran hospital and phebe hospital in liberia between january 1980 and march 1984. all 18 fetal cases died and the case-fatality rate for 15 childhood cases was 27%. we identified four clinical presentations according to age, including a case of congenital lassa fever, a condition not reported previously. two cases of lassa fever were found serologically during a one-month survey of all pediatric admissions at curran luthera ...	1987	3826501
expression of lassa virus nucleocapsid protein segments in bacteria: purification of high-level expression products and their application in antibody detection.	the lassa virus nucleocapsid protein gene and segments from it were expressed in escherichia coli under the control of the lac promoter in puc-based plasmids. expression of the near full-length protein [amino acid (aa) residues 12-570] fused to an n-terminal sequence of vector-derived 6 aa was not particularly efficient, and neither was that of a smaller n-terminal segment (aa 6-201) which was also fused at its c terminus to the remainder of the lacz gene product. by contrast, the c-terminal 370 ...	1987	3315857
molecular structure and early events in the replication of tacaribe arenavirus s rna.	tacaribe arenavirus s rna was cloned and analysis of its nucleotide sequence revealed two open reading frames of significant size, one in the virus-sense strand, the other in the virus-complementary strand. the predicted amino acid sequences of the two reading frames were compared with the predicted primary structures of the nucleoprotein (n) and glycoprotein precursor (gpc) of lcm, pichinde and lassa viruses. the results indicated a high degree of homology between the proteins of similar proper ...	1987	3617928
a prospective study of the epidemiology and ecology of lassa fever.	in studies of lassa fever in sierra leone, the prevalence of human antibody to lassa virus ranged from 8% to 52%. mastomys natalensis, the reservoir of lassa virus, constituted 50%-60% of the rodents captured in houses but only 10%-20% of those captured in surrounding agriculture and bush areas (chi 2 = 90.2, p less than 10(-6), df = 1), a finding suggesting that houses are the most-important location for transmission of lassa virus. viral infection of mastomys from houses ranged from 0% to 80%. ...	1987	3805771
standardization of a plaque assay for lassa virus.	the plaque reduction neutralization test (prnt) has been used routinely in serological studies with such arenaviruses as junin, machupo, and parana. however, difficulties have been encountered in using the prnt for lcm virus, while conflicting views have been expressed about the reliability and efficacy of the test with lassa virus. we have therefore investigated and evaluated the plaque assay for lassa virus. in addition, the suitability of the prnt for determining the potency of a serum and it ...	1987	3585290
[current serologic data on viral hemorrhagic fevers in the central african republic].	during the years 1984-1985, 1,528 serum samples were taken through out the car. of these sera, 319 (20.8%) contained anti-filoviridae antibodies (ebola, marburg). this figure is higher than those found in cameroon, sudan, gabon and zaïre. three zones of the country are particularly exposed, the north-east where the population is in the contact with sudan ebola, the south-east where it is in contact with zaïre ebola, and the south-west where it is in contact with sudan ebola. the authors believe ...	1987	3607998
[characteristics of monoclonal antibodies against lassa virus].	some properties of monoclonal antibodies to the lassa virus have been characterized. the competitive immunoenzyme analysis has revealed the presence of at least three antigens in the lassa virus nucleoprotein.	1987	2441254
physiological and immunologic disturbances associated with shock in a primate model of lassa fever.	the degree of cell and organ damage in clinical and histological studies of patients dying of lassa fever has been insufficient to explain the catastrophic shock characteristic of the fatal illness. to explore this issue further, we conducted a study of the evolution of shock in three lassa virus-infected rhesus monkeys. by the sixth day after infection, a marked, progressive reduction of in vitro platelet aggregation occurred despite normal numbers of circulating platelets and a normal platelet ...	1987	3543155
[identification of the mrna of the nucleocapsid proteins of pathogenic arenaviruses].	total rna from cells infected with machupo and lassa viruses as well as individual sedimentation classes of these rnas were translated in the cell-free protein-synthesizing system from rabbit reticulocytes. the translation products were precipitated either with anti-machupo immune gamma-globulin or monoclonal antibodies to nucleocapsid protein (np) of lassa virus. both total rna and rna fraction with the sedimentation coefficient 15-16s promoted the synthesis of protein which comigrated in gel w ...	1987	2829439
lassa fever--new issues raised by field studies in west africa.		1987	3805770
studies of the coagulation system in arenaviral hemorrhagic fever: experimental infection of strain 13 guinea pigs with pichinde virus.	significant coagulation abnormalities were associated with experimental infection of strain 13 guinea pigs with pichinde virus, an arenavirus related to the virulent human pathogens junin, machupo, and lassa viruses. infected animals developed decreased activity of multiple coagulation factors, decreased antithrombin iii levels, high levels of fibrin-fibrinogen degradation products, impaired platelet function, and thrombocytopenia. testing for the presence of a coagulation inhibitor revealed a p ...	1987	3030150
clinical virology of lassa fever in hospitalized patients.	we measured levels of virus in sequential specimens from 137 patients with lassa fever. the probability of fatal disease increased significantly with the level of viremia measured either on admission or during the course of illness. the odds ratio of death in patients with viremia greater than 10 tcid50/ml was 3.7 (90% confidence interval, 1.9-7.2). the same ratio in patients with viremia greater than 10 tcid50/ml and with levels of aspartate aminotransferase greater than or equal to 150 iu/lite ...	1987	3805773
differentiation between two african arenaviruses (lassa and mozambique) by plaque assay.	the biological characteristics of lassa and mozambique viruses were compared by plaque assay. both viruses produced plaques under the same conditions, however, lassa virus plaques measured on average 2 mm in diameter being twice as large as the mozambique virus plaques. by plaque reduction tests, cross protection was demonstrated between both viruses showing that lassa and mozambique viruses are distinct but related.	1987	2886023
vaccinia recombinant expressing lassa-virus internal nucleocapsid protein protects guineapigs against lassa fever.	the lister strain of vaccinia virus was used to construct a recombinant that expressed the nucleocapsid gene of lassa virus. guineapigs immunised with the recombinant virus were protected against challenge with lassa virus, whereas control animals showed the usual disease course, including pyrexia, anorexia, viraemia, and death. these data indicate not only that protective immunity to lassa fever can be evoked by an experimental vaccine, but also that this response can be mediated by an internal ...	1987	2885642
[pathogenic machupo and lassa arenaviruses: the biochemical properties of virion rna and proteins].	lassa virus purified in the isodensity sucrose concentration gradient had the following buoyant densities: 1.17 g/cm3 (sucrose), 1.19 g/cm3 (cesium chloride), 1.16 g/cm3 (urografin). similar parameters were obtained for machupo virus. virion rnas of these viruses contained 5 sedimentation classes of molecules: 30-31s, 28s, 22-24s, 18s, and 4-6s. experiments on hybridization of individual sedimentation classes of rna with an excess of poly(a)-containing rna from the infected cells as well as inhi ...	1987	2825435
nucleotide sequence of the glycoprotein gene and intergenic region of the lassa virus s genome rna.	two overlapping cdna clones corresponding to the 5' region of the lassa virus s genome rna were isolated and their nucleotide sequences determined. similar to pichinde and lymphocytic choriomeningitis viruses (lcmv), lassa virus has an ambisense s rna. the precursor to the viral glycoproteins (gpc) is encoded in viral rna sequence originating at position 56 and terminating at position 1529 from the 5' terminus of the s rna. a short, noncoding, intergenic region capable of forming a hairpin struc ...	1986	3750844
some biochemical properties of lassa virus rna and polypeptides.		1986	3724668
no evidence for increased risk of lassa fever infection in hospital staff.	a prospective serological study was undertaken in hospital personnel who care for lassa fever (lf) patients in an endemic region of sierra leone, west africa. among personnel from three hospitals where barrier nursing is practised, antibody prevalence and seroconversion by age and sex were consistently equal to or lower than those of persons in nearby village populations. no group among hospital personnel evaluated by age, sex, contact, or occupational exposure was at higher risk than another. h ...	1986	2877335
hemorrhagic fever virus infections in an isolated rainforest area of central liberia. limitations of the indirect immunofluorescence slide test for antibody screening in africa.	serum samples from 119 healthy individuals and 106 epilepsy patients inhabiting grand bassa county, liberia, were tested for antibodies to hemorrhagic fever viruses (hfv) by indirect immunofluorescence. e6 vero cells infected with lassa fever virus (las), rift valley fever virus (rvf), congo hemorrhagic fever virus (con), marburg virus (mbg) and the ebola (ebo) virus strains mayinga (may) and boniface (bon) were used as antigen. to obtain reproducible and specific test results sera had to be abs ...	1986	3092415
lassa virus hepatitis: a study of fatal lassa fever in humans.	in order to explore the significance of a previous observation that the most important pathologic changes in fatal lassa fever are hepatic, we have studied postmortem liver biopsies from 19 patients with fatal lassa fever. we observed a vigorous macrophage response to cellular damage, but we found no evidence of lymphocyte infiltration in infected hepatic tissues. using semi-quantitative estimates of liver cell damage, we found a wide range in the severity and progression of lassa virus hepatiti ...	1986	3953952
serological and biological evidence that lassa-complex arenaviruses are widely distributed in africa.		1986	3724663
serology and virulence diversity among old-world arenaviruses, and the relevance to vaccine development.		1986	3724664
use of monoclonal antibody for the detection of lassa virus antibody and antigen in patients with lassa fever.		1986	3523183
expression of lassa virus nucleocapsid gene fragments in bacteria.		1986	3523185
[indirect immunoenzyme method for the laboratory diagnosis of lassa and ebola hemorrhagic fevers].	conditions for performing solid-phase indirect enzyme-immunoassay (speia) for the detection of lassa and ebola virus antigens and antibodies to them using horseradish peroxidase-labeled antispecific globulins were developed. the method is highly sensitive, specific, and reproducible. by this method, antigens of lassa and ebola viruses could be detected in tissue culture fluid of the infected cell cultures and in animal organ suspensions. detection of antibodies to lassa and ebola viruses in huma ...	1986	3524001
clinical, epidemiologic, and therapeutic aspects of lassa fever.		1986	3724661
lassa fever in children in sierra leone, west africa.	a systematic study of lassa fever in febrile children was undertaken over a four-year period, from august 1977 to august 1981, in the eastern province of sierra leone, west africa. 479 patients were studied; of these, 245 had adequate specimens to confirm or exclude the laboratory diagnosis of lassa fever. 51 cases of lassa fever were identified (21% of patients from whom diagnosis was possible). virus was isolated from 23 patients. all children had fever; cough and vomiting were present in over ...	1986	3810792
lassa fever. effective therapy with ribavirin.	in a study of lassa fever in sierra leone, west africa, we identified two variables associated with a high risk of death, and we evaluated the efficacy of ribavirin and lassa virus-convalescent plasma for the treatment of lassa fever. a serum aspartate aminotransferase level greater than or equal to 150 iu per liter at the time of hospital admission was associated with a case-fatality rate of 55 percent (33 of 60). patients with the same risk factor who were treated for 10 days with intravenous ...	1986	3940312
evolutionary biology of a lassa virus complex.		1986	3724662
molecular cloning of lassa virus rna: nucleotide sequence and expression of the nucleocapsid protein gene.	lassa virus rna isolated from purified virus particles was polyadenylated and reverse transcripts were cloned into the psti site of plasmid puc9. clones containing sequences of the smaller (s) segment of the lassa virus genome were identified by hybridization with purified s rna. they were characterized by their ability to hybridize with fragments of 3'-labeled lassa virus s rna and with each other, and by restriction mapping. the largest insert was 1830 bp long and began with the 3'-terminal 19 ...	1985	3840620
kinetic study of platelets and fibrinogen in lassa virus-infected monkeys and early pathologic events in mopeia virus-infected monkeys.	the rhesus monkey, an established model of lassa fever, was used to study hematologic and hemostatic aspects of lassa fever and whether mopeia (also known as mozambique) virus induces any cellular damage in this model. six days after subcutaneous injection of 10(3.48) plaque forming units (pfu) of lassa virus (josiah strain) one group of monkeys received an intravenous injection of 111in-labeled allogeneic platelets and another group received 125i-labeled alogeneic fibrinogen. lassa virus-infect ...	1985	4037187
endemic lassa fever in liberia. iv. selection of optimally effective plasma for treatment by passive immunization.	the efficacy of passive immunization for treatment of lassa fever (lf) is believed to depend on the titre of the neutralizing antibody infused. for the purpose of identifying optimal donors of lv-immune plasma, a population of lf-convalescent patients in liberia was tested for prevalence of neutralizing antibody. minimally protective titres, expressed as a log10 neutralization index, (lni), were established in animal models as lni greater than 2. lni titres for 26 donors, tested eight or more mo ...	1985	3898484
endemic lassa fever in liberia. iii. characterization of lassa virus isolates.	sixty-three virus isolates were obtained by inoculation of vero cells with sera from 50 hospital in-patients in liberia with acute febrile illnesses. 57 of the isolates were presumptively identified as lassa virus (lv) by direct fluorescent antibody (dfa) staining of inoculated vero cells. these, and six additional isolates obtained only by titration of supernatant fluids from inoculated vero cells, were definitively identified as lv in a neutralization test. two additional lv isolates were obta ...	1985	3898483
[method for the simultaneous detection of immunofluorescing antibodies to the causative agents of different hemorrhagic fevers].		1985	3907144
lassa virus lethality for inbred mice.		1985	4037900
[experimental evaluation of the pathogenicity of lassa virus variants].	pathogenicity for guinea pigs and white mice of various lassa virus variants: native, having had 1 passage in vero cell culture and 4 passages in newborn white mouse brain; a virus having gone through 10 passages in vero cells and 8 mouse brain passages (variant no. 10); a small-plaque clone derived from variant no. 10 by the method of plaque-to-plaque cloning (variant no. 11k), was studied. both the native virus and variant no. 10 were found to be similarly pathogenic for susceptible laboratory ...	1985	4060702
[pathogenicity of the lassa virus for laboratory mice].	pathogenicity for randombred and inbred mice of various age groups of the standard lassa virus and the virus enriched with defective interfering particles (dip) was studied. the standard lassa virus inoculated intracerebrally caused 100% death of c3h/sn mice aged up to 4 weeks and 60%-70% death of randombred white mice aged 3-4 weeks. balb/c mice were found to be nonsusceptible to the virus, and its lethality for c57bl/6 and akr mice varied within the range of 30%-60%. lassa virus enriched with ...	1985	4072162
effect of beta-propiolactone on routine biochemical investigations.		1985	4079681
identification of ippy as a lassa-fever-related virus.		1985	2857974
early diagnosis of human lassa fever by elisa detection of antigen and antibody.	sequential serum samples, beginning on the day of hospital admission, from three patients with lassa fever were tested for the presence of lassa-virus antigens and antibodies by means of an enzyme-linked immunosorbent assay. lassa-virus antigens were detected in the first serum sample from each patient, thus providing an early definitive diagnosis. in contrast, seroconversion was not detectable by elisa or indirect fluorescent antibody techniques until 3 days or more after admission. the antigen ...	1985	2857321