Mercedes Weissenbacher

High Seroprevalence of Bloodborne Viruses among Street-Recruited Injection Drug Users from Buenos Aires, Argentina

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.

Cross-Protection between Tacaribe Complex Viruses. Presence of Neutralizing Antibodies against Junin Virus (Argentine Hemorrhagic Fever) in Guinea Pigs Infected with Tacaribe Virus

Cross-protection between Junin virus and five other Tacaribe complex viruses and the serological response of guinea pigs inoculated with Tacaribe virus are reported here. Previous infection with Tamiami or Pichinde viruses significantly delayed guinea pig deaths. A 58% survival rate was found among animals immunized with three doses of Amapari virus, while guinea pigs inoculated with one dose of Machupo or Tacaribe virus were fully protected against Junin virus. Neutralization tests performed in serum samples of guinea pigs immunized with five doses of Tacaribe virus showed that they developed monologous and heterologous neutralizing antibodies.

Buenos Aires cohort of men who have sex with men: prevalence, incidence, risk factors, and molecular genotyping of HIV type 1.

The prevalence, incidence, risk factors, and molecular genotyping of HIV-1 infection among men who have sex with men (MSM) were assessed through a prospective cohort study. The study was conducted in Buenos Aires from February 2003 to December 2004. Sociodemographic, sexual risk behavior data, and blood samples for HIV testing were collected at baseline and at 6 and 12 months. Cox regression analysis was applied to determine risk factors associated with HIV seroconversion. HIV-positive samples were analyzed by partial (pro/RT) and full-length genome sequencing. Of 811 HIV-negative participants evaluated at baseline, 327 volunteers that fulfilled the inclusion criteria were enrolled. Retention rates at 6 and 12 months were 97.2% and 91.5%, respectively. Twelve MSM seroconverted for HIV infection [incidence rate = 3.9 (95% CI = 2.0-6.7) per 100 person-years]. HIV seroconversion was associated with a greater number of different sexual contacts in the preceding 6 months (> or =10, hazard ratio = 3.3, 95% CI: 1.1-10.4). By partial pro/RT genotyping analysis, 83% HIV-positive samples were subtype B and 17% samples were BF recombinants, most of these being unique recombinant forms. This study describes for the first time the recruitment and follow-up of a cohort of MSM in Argentina. Retention rates and HIV incidence rate were high. These data should be considered as a promising potential population for HIV vaccine trials.

Argentine hemorrhagic fever: a primate model.

Experimental Junin virus infection of a New World primate, Callithrix jacchus, was evaluated. The virus produced anorexia, loss of weight, thrombocytopenia, leukopenia, and hemorrhagic and neurological symptoms and terminated in death. Virus was recovered from urine, blood samples and all tissues taken at autopsy. These preliminary observations show that several aspects of the experimental disease in C. jacchus are quite similar to severe natural Argentine hemorrhagic fever of man.

Intersubtype BF recombinants of HIV-1 in a population of injecting drug users in Argentina.

Summary: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.

Multiple infections and associated risk factors among non-injecting cocaine users in Argentina

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, 10 mL 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.

Hepatitis C virus among non-injecting cocaine users (NICUs) in South America: can injectors be a bridge?

AIM To investigate the factors associated with hepatitis C virus (HCV) infection among non-injecting cocaine users (NICUs) and to compare practices associated with HCV and HIV infection. DESIGN An intercountry cross-sectional study. Setting  Buenos Aires and Montevideo metropolitan areas. PARTICIPANTS A total of 871 NICUs. MEASUREMENTS NICUs were interviewed and their blood was drawn and used for HCV, HIV, HBV surface antigen (HbsAg), HB-anticore and Venereal Disease Research Laboratory (VRDL) antibody assays. Bivariate and multivariate logistic regression analyses included comparisons of HCV and HIV mono-infected participants with HCV-HIV seronegatives. FINDINGS Prevalence rates were 8.8 [95% confidence interval (CI): 6.9-10.8) for HCV and 7.9 (95% CI: 6.1-9.7) for HIV. HCV-infected NICUs were twice as likely as HCV-HIV seronegatives to have shared straws for cocaine snorting or sniffing, even when adjusted for other variables. HCV prevalence rates ranged from 3.6% among NICUs who denied sharing straws and having had an injection drug user (IDU) or an HIV-positive sexual partner to 12.6% among participants who reported ever having shared straws or having had either an IDU- or HIV-positive sexual partner (χ(2) (trend)  = 6.56, P = 0.01). CONCLUSIONS Non-injecting cocaine users from South America are vulnerable to multiple infections and HCV infection appears to occur through the sharing of straws. HCV infection is associated with intimate relationships with IDUs or HIV-seropositive partners, supporting the hypothesis that HCV risk may be due primarily to risk-taking behaviour associated with drugs in this population.

HIV seroincidence estimates among at-risk populations in Buenos Aires and Montevideo: use of the serologic testing algorithm for recent HIV seroconversion.

Summary: Using the serological testing algorithm for recent HIV seroconversion, we estimated annualized incidences (per 100 person-years) of HIV-1 infection in different at-risk groups in Buenos Aires and Montevideo, during a 5-year period between 1998 and 2003. HIV-positive serum samples from 9 serosurveys conducted among men who have sex with men, patients attending clinics for a sexually transmitted infections consult (STIs), female commercial sex workers, injecting drug users (IDUs), noninjecting cocaine users (NICUs), asymptomatic women screened for HIV infection, and patients with tuberculosis were used. HIV incidences were as follows: 6.7 for men who have sex with men, 2.0 for STIs, 1.3 for female commercial sex workers, 0.0 for Argentinean IDUs, 10.3 for Uruguayan IDUs, 3.1 for Argentinean NICUs, 4.4 for Uruguayan NICUs, and 2.4 for patients with tuberculosis. Among asymptomatic women screened for HIV infection, incidence rose from 0.4 in 1998 to 4.6 in 1999 and to a high of 10.2 in the year 2000. Unexpectedly, high HIV incidences were detected among at-risk groups in Buenos Aires and Montevideo. This pattern shows an emerging HIV epidemic among heterosexuals stemming from core HIV-infected at-risk groups. There is an urgent need for development and implementation of specific prevention strategies to address this burgeoning epidemic.

Epidemiology of Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome in Injection Drug Users in Argentina: High Seroprevalence of HIV Infection

The aim of this study was to compile published data and to describe the prevalences of human immunodeficiency virus (HIV) infection among injection drug users (IDUs) in different populations studied in Argentina from 1987 through 1999. Twenty-two studies of HIV infection in the IDU population were selected, and 6 subject groups were defined: outpatients, prisoners, children in rehabilitation institutes, hospitalized patients, IDUs receiving drug treatment, and female sex workers. The median prevalence of HIV infection among 1506 outpatients (5 studies) was 64.0%; among 175 prisoners (1 study), the prevalence was 35.4%; among 446 children in rehabilitation institutes (4 studies), the prevalence was 48.1%; among 136 hospitalized patients (2 studies), the prevalence was 49.5%; among 2708 IDUs receiving drug treatment (7 studies), the prevalence was 39.0%; and among 26 female sex workers (2 studies), the prevalence was 47.0%. Prevalence of HIV infection was high among IDUs in Argentina, ranging from 27% to 80%.

OPPORTUNISTIC INFECTIONS IN PEDIATRIC HIV INFECTION: A study of 74 Autopsy Cases from Latin America

A postmortem analysis of opportunistic infections in 74 pediatric AIDS cases from Argentina Brazil and Mexico was conducted to establish a baseline for future monitoring of HIV in children in Latin America. The collaborative study emerged from a 1992 meeting of Latin American pathologists organized by the Pan American Health Organization. The mean age of autopsied children was 2.7 years; 72% of cases were 12 months of age or under. Fungal infections--especially Candida (29 cases 39.18%) and Pneumocystis carinii (15 cases 20.27%)--were the most common opportunistic infections. Viral infections were found in 31 cases 25 (38.7%) of which were cytomegalovirus. Additional infections detected were cryptosporidiosis (6 cases) Mycobacterium avium intracellulare (4 cases) and tuberculosis (1 case). Nonspecific bacterial bronchopneumonia was present in 11 cases. 4 cases of toxoplasmosis 3 of which were localized in the central nervous system were found. Cytomegalovirus and P carinii was the most common combination of infections. Despite a slightly higher frequency of cases of histoplasmosis and brain toxoplasmosis these findings are generally comparable to those of pediatric AIDS autopsies conducted in North America.