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Objectives: Trypanosoma cruzi reactivation in HIV patients is considered an opportunistic infection, usually with a fatal outcome. The aim of this study was to describe the epidemiological and clinical features of T. cruzi infection in HIV patients and to compare these findings between patients with and without Chagas disease reactivation. Methods: The medical records of T. cruzi–HIV co-infected patients treated at the Muñiz Infectious Diseases Hospital from January 2005 to December 2014 were reviewed retrospectively. Epidemiological and clinical features were assessed and compared between patients with and without Chagas disease reactivation. Results: The medical records of 80 T. cruzi–HIV co-infected patients were reviewed. The most likely route of T. cruzi infection was vector-borne (32/80 patients), followed by intravenous drug use (12/80). Nine of 80 patients had reactivation. Patients without reactivation had a significantly higher CD4 T-cell count at diagnosis of T. cruzi infection (144 cells/μl vs. 30 cells/μl, p = 0.026). Chagas disease serology was negative in two of nine patients with reactivation. Conclusions: Serological assays for T. cruzi infection may be negative in severely immunocompromised patients. Direct parasitological techniques should be performed in the diagnosis of patients for whom there is a suspicion of T. cruzi reactivation. HIV patients with a lower CD4 count are at higher risk of reactivation. Fil: Benchetrit, Andres Guillermo. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Fernández, Marisa. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Bava, Amadeo Javier. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Corti, Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Porteiro, Norma. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina Fil: Martinez Peralta, Liliana A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; Argentina

The aim is to estimate HBV prevalence and the associated risks among noninjecting cocaine users (NICUs). In 2002-2003, a total of 824 NICUs from Buenos Aires (Argentina) and Montevideo (Uruguay) were interviewed using a structured questionnaire. Serologic tests were carried out for Human Immunodeficiency Virus (HIV), hepatitis B (HBV), syphilis, and others. The population was divided into two serologic groups: HBV-infected and seronegative group. Univariate and binary logistic model were developed. The results seem to indicate that, among NICUs, HBV is transmitted through sexual contact. Prevention measures, including vaccine, are needed in order to control and minimize risks. The study's limitations are noted.

Mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) as described for women with an established infection is, in most cases, associated with the transmission of few maternal variants. This study analysed virus variability in four cases of maternal primary infection occurring during pregnancy and/or breastfeeding. Estimated time of seroconversion was at 4 months of pregnancy for one woman (early seroconversion) and during the last months of pregnancy and/or breastfeeding for the remaining three (late seroconversion). The C2V3 envelope region was analysed in samples of mother–child pairs by molecular cloning and sequencing. Comparisons of nucleotide and amino acid sequences as well as phylogenetic analysis were performed. The results showed low variability in the virus population of both mother and child. Maximum-likelihood analysis showed that, in the early pregnancy seroconversion case, a minor viral variant with further evolution in the child was transmitted, which could indicate a selection event in MTCT or a stochastic event, whereas in the late seroconversion cases, the mother's and child's sequences were intermingled, which is compatible with the transmission of multiple viral variants from the mother's major population. These results could be explained by the less pronounced selective pressure exerted by the immune system in the early stages of the mother's infection, which could play a role in MTCT of HIV-1.

The aim of this study was to estimate the seroprevalence rates of human immunodeficiency virus (HIV), hepatitis B virus (HBV, core antibody), hepatitis C virus (HCV), and syphilis infections and analyze associated risk factors among 504 non-injecting cocaine users (NICU) in Buenos Aires, Argentina. Participants were interviewed in face-to-face sessions through a short structured questionnaire. Using venipuncture, 10mL of blood was collected. Seroprevalence rates were: HIV (6.3%), HBV (9%), HCV (7.5%), and VDRL (4.2%). The risk of being infected with HIV, HBV, and HCV was significantly associated with having had a sex partner who was either a drug injector or who was known to be HIV positive. HIV and HCV infections were associated with former imprisonment, and HCV was associated with having been tattooed. Because of the rising number of NICU and the multiple infections detected, it is essential to implement prevention strategies focused on this population.El propósito de este estudio era estimar los índices de seroprevalencia del virus de inmunodeficiencia humano (VIH), virus de la hepatitis B (VHB, anticuerpo core), virus de la hepatitis C (VHC) e infecciones de sífilis y analizar factores de riesgo asociados entre 504 usuarios de cocaína no inyectable (UCNI) en la ciudad de Buenos Aires, Argentina. Se entrevistó a los participantes en sesiones cara a cara a través de un cuestionario estructurado corto. Usando el método de la venipunción se recogieron 10mL de sangre. Las tasas de seroprevalencia fueron: VIH (6,3%), VHB (9%), VHC (7,5%), y VDRL (4,2%). El riesgo de infección por VIH, VHB, y VHC se asoció significativamente a mantener relaciones sexuales con un compañero/a que era consumidor de la droga inyectada o que era conocido por ser VIH positivo. Las infecciones de VIH y de VHC se asociaron a haber estado encarcelado anteriormente, y la de VHC se asoció también a haber sido tatuado. Debido al número creciente de UCNI y a las infecciones múltiples detectadas, es esencial implementar estrategias de prevención centradas en esta población.

HIV-1 infection in children less than 15 years of age is mainly due to mother-to-child transmission. The aim of this work was to investigate molecular evidence to prove father-to-be horizontal transmission in two possible events of transmission. In the first event a boy was identified as HIV infected at 2-3 years of age. At the same time infection was confirmed in the father, while mother and siblings were negative. In the second event a girl was negative for HIV at age 1 and identified as HIV-1 infected at age 6. The father's HIV infection was diagnosed in the same period while the mother was repeatedly negative. No evidence of sexual assault or transfusion was recorded in any case. Peripheral blood mononuclear cells were obtained from both fathers and children. After PCR amplification, the C2V3 region of the envelope gene and the region coding for amino acid 132 of p24 up to amino acid 40 of p7 of the gag gene were sequenced. Genetic distance measurements and phylogenetic tree analysis showed that in both cases the father's and child's viral sequences were closely related. They were distinct when compared to Argentina sequences including sequences from the same geographic region. Epidemiological and molecular data strongly suggest that horizontal transmission had occurred, probably related to the close father-to-child contact.

The presence of recombinant intersubtypes of HIV-1 in Argentina has been reported since the mid-1990s. In this study sequences of a region of the gag pol and vpu genes of HIV-1 were analyzed in samples of 21 injection drug users (IDUs) residing in the suburbs of the city of Buenos Aires. Genomic characterization and identification of recombination sites were made comparing the 3 regions with reference isolation sequences of subtypes B F C A and B/F recombinants: CRF12_BF and non-CRF12_BF sequences. Subtype assignment of the analyzed segments was phylogenetically confirmed. All the samples turned out to be BF recombinants in at least 1 of the 3 studied genes. Twelve samples (57%) had the same pattern as the Argentinean CRF12_BF whereas in the rest the pattern differed in at least 1 of the 3 genes. The relation of these fragments to the CRF12_BF was phylogenetically verified. These results indicate the predominance of BF recombinants and the presence of a high percentage of sequences closely related to the CRF12_BF in the IDU population in Argentina and suggest a possible association between viral variants and the transmission route. (excerpt)

Objective: To determine human immunodeficiency virus (HIV) seroprevalence in a sample of men who have sex with men (MSM) in Buenos Aires City and to identify risk factors associated with HIV type 1 infection. Methods: Participants were invited to receive HIV counselling and testing at ‘NEXO’ (a gay non-governmental organization) by means of informative leaflets distributed in gay nightclubs porno cinemas gymnasiums and in the streets. During the encounter the study was explained by a trained social worker and individuals were invited to volunteer for the study. Diagnosis of HIV was performed using two screening tests and Western Blot assay was used as confirmatory. Results: Human immunodeficiency virus was detected in 96 (13.8%; 95% CI: 11.4–16.7) of 694 MSM. Fourteen (14.6%) of the 96 HIV-positive MSM were already aware of their HIV serostatus. In univariate analysis HIV-1 infection (odds ratio [OR] >1.5) was found to be associated with older age (30–39 years) being unemployed a previous sexually transmitted disease (STD) history and having an HIV-positive partner. Cocaine consumption and irregular use of condoms with occasional partners were also found to be risk factors. In multivariate logistic regression analysis being unemployed (OR = 3.42; 95% CI: 1.17–9.99) and having an HIV-positive partner (OR = 2.67; 95% CI: 1.09–6.52) remained significant risk factors. Discussion: The high HIV-1 prevalence observed suggests an urgent need for implementation of effective prevention campaigns. This represents the first cross-sectional epidemiological study of HIV among the high-risk group of MSM in Argentina. (authors)

This study evaluated the success of a national program for the prevention of mother-to-child transmission (MTCT) of HIV-1 in 874 mother-infant pairs from Buenos Aires and surroundings. This population was referred to the National Reference Center for AIDS for diagnosis of neonatal infection during 1993-2000. The data revealed an increase in the use of antiretroviral therapy during pregnancy from 3.2% in 1993-1994 to 73.1% in 1999-2000 and in the use of cesarean delivery (reaching 54.8% in 1999-2000). However, the proportion of HIV-infected women who continued to breast-feed their children remained steady (around 12%). General improvement of the conditions for decreasing MTCT resulted in a significant decrease in the proportion of infected infants from 37.3% before 1995 to 10.7% in 1999-2000 and even 6.5% during 2001. Data on the time of diagnosis indicated that only 42.7% of the women knew about their HIV status before pregnancy, 44.8 knew during pregnancy, and 12.3% knew after the birth of their child. The main risk factor for HIV infection in the mothers was heterosexual contact (73%), and in the fathers, it was injection drug use (67%). These results point out the urgent need to develop additional strategies for prevention of MTCT of HIV-1 to generalize education, counseling, and testing of young women.

This study determined the risk behaviors and viral subtypes of HIV-1 found in 134 heterosexual HIV-seroprevalent maternity patients, 41 of their sexual partners (men who have sex with women [MSW]), and 95 homosexual men (men who have sex with men [MSM]) from Buenos Aires, Argentina. Peripheral blood mononuclear cells (PBMCs) were purified from blood and used for DNA extraction, amplification, and genotyping by the envelope heteroduplex mobility assay (env HMA). Most of the women had been infected by having sex with an already infected partner (84%), whereas most of the male partners had been infected via drug use (76%). Both the patients and their sexual partners were poorly educated, only 30% having completed secondary school. The MSM study subjects, however, were significantly better educated and had a lower prevalence of injecting drug use.Env HMA subtype F was found in 77% (103 of 134) of the maternity patients, with similar rates in their partners (73%). Most of the remaining samples were env subtype B. All but one of the couples was concordant in subtype. In the MSM risk group, however, only 10% were env HMA subtype F. Ninety percent of the MSM samples were subtype B. There are at least two independent epidemics of HIV-1 infection in Buenos Aires, Argentina. One, in heterosexual men and women, is dominated by env subtype F whereas the other, in homosexual men, is dominated by env subtype B, as determined by env HMA.

Continuous cultivation of murine L cells infected with lymphocytic choriomeningitis virus strain Armstrong leads to production of L(Arm) cells, which produce a predominantly cell-associated attenuated variant, the L(Arm) virus. The relatively few infectious particles that are released have lost the ability to form plaques on L cells and to cause illness in mice even if inoculated intracerebrally. Based on equal protein M(r)s, antigenicity and protein kinase activity, essentially identical results were obtained for the purified Armstrong and L(Arm) viruses. There was also no difference in production and release of particles with the potential to cause homologous interference. Such particles consisted of two types, one of which was highly susceptible to u.v.-irradiation, the other was highly resistant. In the case of the L(Arm) virus interfering particles, it appears that the u.v.-irradiation-susceptible forms represented infectious virus. Purified L(Arm) virus particles contained considerable quantities of subgenomic forms of (small) S- and (large) L-RNA and their complementary counterparts, which all appeared to be replicated autonomously in an unenriched manner.

Background Genetic characterization of HIV-1 in Argentina has shown that BF recombinants predominate among heterosexuals and injecting drug users, while in men who have sex with men the most prevalent form is subtype B. Objectives The aim of this work was to investigate the presence of HIV dual infections in HIV-infected individuals with high probability of reinfection Study design Blood samples were collected from 23 HIV positive patients with the risk of reinfection from Buenos Aires. A fragment of the HIV gene pol was amplified and phylogenetic analyses were performed. Antiretroviral drug resistance patterns of all the sequences were analyzed. Results Five dual infections were detected with four patients coinfected with subtype B and BF recombinants and one patient was coinfected with two BF recombinants presenting different recombination patterns. Prolonged infection with a stable clinical condition was observed in the five individuals. Resistance mutation patterns were different between the predominant and the minority strains. Conclusions Our results show that HIV dual infection can occur with closely related subtypes, and even with different variants of the same recombinant form in certain populations. Clinical observations showed neither aggressive disease progression nor impact on the resistance patterns in the dually-infected patients.

To analyze humoral cross-reactivity to V3 peptides from subtype B and BF recombinant forms, plasma samples from 50 HIV-1-infected patients were characterized by sequencing fragments of the env and pol genes. An in-house EIA was performed using peptides corresponding to the 15 central amino acids of the V3 loop of gp120 from subtypes B (MN, SF2) and F1 and a consensus peptide from Argentinean BF recombinants. No differences were found with respect to the infecting subtype, but significant differences were found among the peptides. Reactivity was higher against the MN and BF peptides in both groups infected with subtype B (n = 28) and BF (n = 22) recombinants than against subtype F1 and SF2 peptides. Fil: Ambrosioni, J.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina Fil: Andreani, Guadalupe. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Acuipil, Carolina Vanesa. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina Fil: Barral, R.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina Fil: Rabinovich, Roberto Daniel. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martinez Peralta, Liliana A.. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Microbiología. Centro Nacional de Referencia para el Sida; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Conclusion These results correlate with previous studies conducted among IDUs from New York city, Vietnam and Southern Europe where HTLV-IIb was more frequently found. In contrast, IIa is found among IDUs from other regions of the USA, Europe and Brazil. This is the first time in which subtype b is described in Argentina among IDUs. Its presence may be due to migrations of aborigines to big cities and the introduction of drugs in this population. Lately, there was also a high rate of migration and tourism to Argentina, especially from southern Europe and USA, possibly contributing to the spread of HTLV-IIb in our country. Interestingly, the IIa sample described here was found to be related with Brazilian aborigine sequences in contrast to the previous Argentinian IDU which was closer to African isolates. from 2006 International Meeting of The Institute of Human Virology Baltimore, USA. 17–21 November, 2006

Injection drug use is the main mechanism of human immunodeficiency virus (HIV) transmission in Argentina (40% of reported AIDS cases in Argentina). This study was conducted among street-recruited injection drug users (IDUs) from Buenos Aires, with the aim of estimating seroprevalence and coinfection of HIV, hepatitis B virus (HBV), hepatitis C virus (HCV), and human T-lymphotropic viruses (HTLVs). A total of 174 volunteers participated in this study; 137 were men (78.7% of volunteers). The average age of the participants was 30 years. Only 64 of participants (37%) had no viral infection, whereas 110 (63%) were infected with > or =1 viruses. Seroprevalences were 44.3% for HIV, 54.6% for HCV, 42.5% for HBV, 2.3% for HTLV-I, and 14.5% for HTLV-II. Among the 77 HIV-infected persons, only 6.5% (5 persons) were not coinfected with other viruses; 88.3% (68) were coinfected with HCV and 68.8% (53) were coinfected with HBV. We demonstrated the existence of multiple viral infections with a high rate of prevalence in IDUs in Buenos Aires, Argentina.

To investigate GB virus C (GBV-C)/hepatitis G virus (HGV) mother-to-infant transmission when only 5′ noncoding region (NCR) sequences were available, a retrospective study was carried out. Although the 5′ NCR is widely used for GBV-C/HGV detection due to the high degree of sequence conservation among isolates (8), this fact clearly limits its potential use to trace chains of transmission, despite the presence of scattered subregions with higher heterogeneity. Nevertheless, since the 5′ NCR has been reported to be unmodified after 8.4 years of evolution (5), a mother-to-infant chain was expected to show (almost) identical sequences unless specific 5′ NCR variants were involved in selective transmission. Analyzed sequences were obtained from (i) a study group which encompassed plasma samples simultaneously obtained from 34 human immunodeficiency virus (HIV)-infected mothers (13 intravenous-drug users [IVDU] and 21 nonaddict women putatively infected by a heterosexual route [IHSR]) as well as from their respective infants (1 to 7 months old, without history of blood transfusion) born to either HIV-positive and GBV-C/HGV-infected mothers (n = 8) or to HIV-positive but GBV-C/HGV nonviremic mothers (n = 26) and (ii) a control group which comprised 31 5′ NCR sequences derived from contemporary isolates circulating in the city of Buenos Aires and 6 others from the rest of the world. Several precautions (3) as well as appropriate controls were included to minimize the possibility that sequence identity among samples was the mere result of PCR contamination: (i) samples from mothers and infants were analyzed separately (elapsed time, 2 months); (ii) each positive result was confirmed in duplicate; and (iii) one negative control (SDW) was included for every three samples. To estimate the potential influence of Taq-dependent misincorporated nucleotides during PCR amplification (4), three cDNAs from local isolates of GBV-C/HGV whose sequences (325 bp) had been previously established (6) were amplified in duplicate and bidirectionally sequenced. A total of 4 of 13 IVDU and 4 of 21 IHSR mothers (30.8 and 19.0%, respectively; P not significant) proved positive for GBV-C/HGV RNA ascribed to genogroup 2a (n = 4), 2b (n = 2), or 3 (n = 2). Only three of eight infants born from viremic mothers (and none from 26 nonviremic mothers) exhibited GBV-C/HGV RNA (37.5%; one born to an IVDU and two to IHSR GBV-C/HGV-positive mothers); their genogroups, as established by both restriction fragment length polymorphism and cDNA sequencing (8), were the same as those of their respective mothers. The phylogenetic analysis was based on both genetic distance (neighbor joining) (Fig. ​(Fig.1)1) and maximum parsimony (data available upon request) methodologies. Both procedures showed unambiguously a genetic relatedness (i.e., no mutation between them) in each GBV-C/HGV mother-infant pair. In contrast to such a lack of nucleotide differences among the three mother-infant pairs, a mean ± standard deviation of 11.56 ± 6.17 nucleotide (nt) replacements was found among unrelated chosen sequences (n = 155 pairs of sequences analyzed). These control sequences corresponded to simultaneously circulating strains in the city of Buenos Aires which were ascribed to the same genogroups putatively associated with transmission chains in this study (i.e., genogroups 2a [n = 17 isolates] and 3 [n = 9]). None of these 26 sequences were identical. When nucleotide replacements were analyzed separately among all included (sub)group 2a (n = 119) and group 3 (n = 36) pairs of sequences, means ± standard deviations of 10.13 ± 3.16 and 16.77 ± 9.77 changes, respectively, were recorded (P < 0.00001; Student t test [two-sided test]). However, one pair of epidemiologically unrelated sequences (Arg15/Arg25) exhibited only one nucleotide difference (a 1-nt gap), seemingly appearing genetically related by the neighbor-joining analysis (Fig. ​(Fig.1).1). When maximum parsimony was carried out, only the three pairs of mother-infant 5′ NCR sequences remained undoubtedly related, since the lengths of their respective tree segments (in units of expected nucleotide substitutions per site) were equal to 0 and those between the above-mentioned sequences exhibiting a 1-nt gap were equal to 0.1073. Such a discrepancy between the two phylogenetic methodologies might be attributable to the reported (7) known loss of information with neighbor joining compared with maximum parsimony (distance versus discrete methods, respectively). FIG. 1. Phylogenetic analysis of GBV-C/HGV sequences (nt positions 132 to 337) from mother A (MA) and infant A (IA), MB and IB, and MC and IC compared with those obtained from simultaneously circulating strains in Argentina (ARG) and the rest of the world (W). ... The use of one mutation as a cutoff to discriminate related versus unrelated 5′ NCR sequences has the inherent risk of being Taq dependent. However, sequencing of the three control cDNAs (2,150 nt) rendered uniformly conserved (and repeatedly obtained) results. Thus, considering one mutation as the best cutoff value to discriminate between the related and unrelated 5′ NCR sequences analyzed in this study, the Youden's Index (sensitivity + specificity − 1) was equal to 1, the maximum possible value (1). In agreement with this view, the probability that three pairs of 5′ NCR sequences were identical (between members of pairs) due to random events is less than 1/17,576 (1/26 × 1/26 × 1/26), or 0.000056895, since none of the 26 simultaneously circulating local isolates ascribed to the same genomic group or subgroup implicated in putative chains of transmission were identical. Such mathematical support is coincident with the epidemiological data, since the studied babies lacked any risk factor for GBV-C/HGV infection except the corresponding mother's ongoing infection. As a whole, results obtained provided strong support to suggest the occurrence of GBV-C/HGV mother-to-infant transmission. The 5′ NCR was recently studied in transmission chains among hemodialyzed patients (2). To our knowledge, this is the first report to use both mathematical and phylogeneticanalyses to examine the eventual use of 5′ NCR sequences—when they are the only available data—to evaluate putative transmission chains.

Detection of anti-HIV-1 IgA antibodies using a modified ELISA test for the early diagnosis of perinatally acquired HIV-1 infection in children treated with protocol ACTG 076 was evaluated. A total of 177 sera were obtained from 141 infants between 1 and 12 months of age (46 were treated and 95 were non-treated with protocol ACTG 076) and tested for HIV IgA antibodies by an ELISA test after removal of IgG with recombinant protein G. Infants were classified according to CDC's classification system after a follow-up until 20 months of age. Of the 46 treated children 22 turned out to be infected and in the group of 95 untreated children, 52 were infected. All 81 samples from uninfected children treated or untreated with protocol ACTG 076 were persistently IgA-negative. HIV IgA antibodies were detected in 14 of 25 plasma samples from infected children with treatment, and in 58 of 71 samples in infected children without treatment. Considering that the sensitivity of this test is lower in children younger than 6 months the population of children studied was divided into two groups; those under and those over 6 months of age. No significant differences were observed in the detection of IgA in treated or untreated children in both age groups. The overall specificity of the test was 100 per cent; sensitivity in children older than 6 months was 76.92 per cent in treated children and 93.10 per cent in untreated children. In spite of the small number of samples studied it could be demonstrated that treatment with zidovudine does not affect the detection of IgA antibodies. This is a simple and inexpensive method that could be used for diagnosis of treated and untreated children in developing countries.

The Tacaribe complex of Arenaviridae is comprised of a group of 10 serologically cross-related viruses that are transmitted by rodents living in different geographic locations of the Western hemisphere from Florida to Argentina. So far, members of the Tacaribe group, also referred to as the New World arenaviruses, include Junin (the agent of Argentine hemorrhagic fever), Machupo (the agent of Bolivian hemorrhagic fever), Guanarito (the agent of Venezuelan hemorrhagic fever), and Pichinde, Tacaribe, Tamiami, Latino, Amapari, Flexal, and Parana viruses, none of which are currently known to be naturally infectious or pathogenic for humans (Howard, 1986).

Address: 1National Reference Centre for AIDS, Microbiology Department, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina, 2Laboratory of Parasitology, Microbiology Department, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina and 3Endocrinology Service, Clinic Biochemistry Department, Jose de San Martin Hospital, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina * Corresponding author

Analysis of radioactively labelled and highly purified infectious lymphocytic choriomeningitis (LCM) virus by polyacrylamide gel electrophoresis (PAGE) revealed 12 components which, according to their apparent molecular weight and glycosylation status, were designated as p19, p25, p26, gp35, p38, gp44, gp60, p63, p77, gp85, gp130, and p200. As shown by immunoprecipitation, they all bound to rabbit anti-LCM virus antibodies. Three proteins, namely gp35 (= 'GP-2'), gp44 (= 'GP-1') and p63 (= 'NP'), had previously been described by others as major constituents of the virion. Our results confirm this and suggest that gp60, p77, gp85, and p200 are further distinct structural proteins. In contrast, p25 and p38 appear to be cleavage or degradation products of p63; p19 and p26 seem to belong to gp60, which could be the monomeric form of a dimer, gp130. Peptide mapping by limited proteolysis revealed considerable overlapping of amino acid sequences among the major glycoproteins with one peptide being common to all. From the results of PAGE performed after external labelling of intact virions, we conclude that gp44, gp60, and gp85 (but not gp35) form the surface of the virus envelope. Analytical isoelectric focusing under non-reducing conditions has shown that the major glycoproteins appeared to consist of several components with different isoelectric points.

Summary Lymphocytic choriomeningitis (LCM) virus interfering particles were enriched relative to infectious virions by ultracentrifugation in a shallow gradient made of Urografin. Electrophoretic analysis revealed that they lacked the small (‘S’) 23S RNA as well as GP-1 and GP-2 of the infectious virion and also lacked a newly characterized glycoprotein of apparent mol. wt. 85 × 103; instead, they contained a novel glycoprotein with mol. wt. 65 × 103.