HIV-1 infection in intravenous drug abusers with clinical manifestations of hepatitis in the city of Buenos Aires.

A serologic study of hepatitis and HIV infections among 99 I.V. drug abusers with hepatitis was conducted between December 1986 and September 1987. The average age of the study subjects was 21 years. Eighty-nine (90%) of the subjects were male, including four whose sexual orientation was homosexual/bisexual. Serologic tests indicated that 87 of the 99 subjects had hepatitis B virus infections, 62 acute and 25 chronic. Nine (10%) of these 87 patients were coinfected with the delta agent. Two subjects had acute cases of hepatitis A, and the 10 remaining subjects had non-A non-B hepatitis. Forty-seven of the study subjects were also found to be infected with HIV-1. The prevalence of the delta marker was surprisingly high, because Argentina has been regarded as nonendemic for the delta virus. Given the trend of increasing I.V. drug abuse in Argentina, these results presage a significant increase in the delta agent's prevalence in the immediate future.

Long-term protection against Argentine hemorrhagic fever in Tacaribe virus infected marmosets: virologic and histopathologic findings.

Tacaribe virus may represent a better alternative than attenuated strains of Junin virus (JV) for immunization against Argentine hemorrhagic fever (AHF) because of possible risk of persistent infection of disease associated with live, attenuated strains. Callithrix jacchus marmosets, which suffer 100% mortality if inoculated with the pathogenic XJ strain of JV, were used to evaluate possible Tacaribe virus persistence, subclinical, or long-term disease and the duration of protection against challenge with JV. Histologic studies did not show pathogenic changes due to Tacaribe virus in primates sacrificed from 7 to 480 days postinoculation (pi). No virus was recovered in tissue samples after primary culture or cocultures with sensitive cells. The presence of anti-Tacaribe neutralizing serum antibodies and protection against pathogenic JV were detected up to 480 days after a single dose of Tacaribe virus. However, anti-Junin antibodies were detected only after challenge. In other experiments, protection against JV was evaluated histologically and virologically. Two primates were immunized with Tacaribe virus, challenged with JV, and sacrificed 18 or 21 days later. Subclinical histopathologic findings were associated with recovery of JV only by the sensitive primary culture-coculture techniques. The immunogenicity, degree of protection, and safety of Tacaribe virus indicate its potential as a vaccine against human AHF.

Mouse splenocyte transfer effect depends on donor's Junin virus infection stage.

Splenocytes from Junin-virus-persistently-infected euthymic mice taken at 45 days postinfection seemed unable to induce overt signs of disease, to cause death, or to modify brain viral levels when transferred to athymic Junin-virus-infected mice. Findings differed sharply when the same recipients were transferred with splenocytes taken at 6 or 30 days postinfection from immunocompetent mice infected in adult life, since mortality reached 80 or 50%, respectively, and brain viral titers were significantly lowered. Furthermore, splenocytes taken at 6 days postinfection from whole adult mice proved harmless to persistently infected euthymic mice. These findings strongly suggest the existence of an immune system alteration in the immunocompetent mouse, attributable to Junin virus persistence. This premise is based on the fact that splenocytes from persistently infected mice were unable to recognize viral antigen expressed on recipient-infected cells. The absence or impairment of a specific cytotoxic T cell population is hereby postulated.

Tacaribe virus: a new alternative for Argentine hemorrhagic fever vaccine.

Tacaribe virus is know to protect guinea pigs and primates against lethal challenge with Junín virus. A long-term study on the effect of Tacaribe virus infection in the guinea pig was carried out to determine the extent of cross-protection and whether antigen and/or viral persistence and tissue damage could be detected in immune animals. Viral titers, antigen expression in organs, and histologic lesions were sequentially searched for up to 540 days postinfection (pi). Neutralizing antibodies (Abs) and cross-protection to Junín virus were evaluated up to 660 days pi. Tacaribe virus titers and antigen peaked at 7-10 days pi to become undetectable after 30 days pi, except for a transient viral recovery from salivary gland. Virus was undetectable by coculture at 365 and 540 days pi. No immunoglobulins or C3 deposits were detected by immunofluorescence in brain or kidney at any stage, and histologic lesions were absent throughout. Anti-Tacaribe and anti-Junín neutralizing Abs were detected up to 660 days and full protection against challenge was achieved at 365 and 540 days, declining to 33% at 660 days pi. The results warrant consideration of Tacaribe virus as potential heterologous vaccine against Argentine hemorrhagic fever.

Therapeutic effect of the antiviral agent ribavirin in Junín virus infection of primates.

In order to assess the effect of the antiviral Ribavirin on the course of Junín virus infection in Callithrix jacchus, seven inoculated monkeys were treated with 15 mg of the drug, twice a day, starting 6 days after infection when all animals were viremic. The three untreated controls showed typical signs of Junín virus infection at 14 days pi and their mean time of death was 18 days. In contrast, no signs of illness were detected in Ribavirin-treated animals until 24 days pi, when marmosets showed signs of neurological involvement: 5 of these animals died (mean day of death: 36) but the two remaining treated monkeys improved and survived infection without sequelae. The comparison of survival rates (0% vs 28%) and the delay of the mean day of death observed indicates that the Ribavirin treatment used has therapeutic effect on Junín virus infection in vivo.

Induction of Junin virus persistence in adult athymic mice.

To determine the role of T lymphocytes in adult mice infected with Junin virus, 60-day-old athymic (nu/nu) mice and their immunocompetent (nu/+) littermates were inoculated intracerebrally with 10(3) TCD50 of the XJ strain. None of them exhibited neurologic illness during a 6-month observation period, and mortality was 3% for nu/nu and 7% for nu/+ animals. The main features in infected nu/nu mice were: high viral titers in brain, reaching a late peak (6.5 log/ml) 32 days postinoculation and persisting at least 6 months; low, late viremia appearing simultaneously with the viral peak in the central nervous system (CNS) and persisting up to 3 months after infection; absence of signs of neurologic disease or histologic lesions in brain and almost no mortality; and lack of detectable circulating antibodies either in IgM or in other immunoglobulins (Igs). Circulating anti-Junin antibodies were demonstrated in IgM and other Igs in immunocompetent mice, although no infectious virus or histologic lesions could be detected. These results show an important role for T lymphocytes in the clearance of Junin virus in the CNS, as demonstrated by viral persistence induced in adult athymic mice.

[Association of the infection of the thymus and bone marrow with the establishment of persistent infection with Junin virus in 2 genera of rodents]. / Asociación de la infección del timo y médula ósea con el establecimiento de la infección persistente con virus Junín en dos géneros de roedores.

Junin virus infection of immune system organs was correlated with persistence establishment in the mouse and rat. Rockland mice under 24 or at 72 and 120 h of age received 10(4) pfu of Junin virus XJ strain by ic route. Separately, two groups of mice under 24 h old were infected with the same dose of XJ or XJCl3 strain by the same route respectively. Results showed that higher thymus virus titer correlated with greater survival. In turn, the former also seemed to correlate with decreasing age at inoculation time, although there was considerable strain dependence. In order to correlate replication levels in thymus with clinical progress in mice, animals under 24 h of age were inoculated with XJ. At 14 days pi apparently healthy mice from this batch were separated from those presenting severe neurologic sings. In the asymptomatic mice, thymus titers ranged from 1.7 to 3.2 log, while no virus was found in thymus harvested from obviously ill animals. However brain virus titers in the two groups proved similar. To confirm these findings, 72 h old Wistar rats were inoculated in with 10(4) pfu of either Junin virus strain: with XJ strain (90% survival) virus could be readily isolated from thymus and bone marrow at day 7 pi, whereas with XJCl3 (5% survival) no virus could be rescued from any organ tested. Therefore, our results strongly suggest a close correlation between productive thymic infection and Junin virus persistence establishment in these rodents, depending on immune response regulation rather than on viral variation.

Asociación de la infección del timo y médula ósea con el establecimiento de la infección persistente con virus Junín en dos géneros de roedores. / [Association of the infection of the thymus and bone marrow with the establishment of persistent infection with Junin virus in 2 genera of rodents]

Junin virus infection of immune system organs was correlated with persistence establishment in the mouse and rat. Rockland mice under 24 or at 72 and 120 h of age received 10(4) pfu of Junin virus XJ strain by ic route. Separately, two groups of mice under 24 h old were infected with the same dose of XJ or XJCl3 strain by the same route respectively. Results showed that higher thymus virus titer correlated with greater survival. In turn, the former also seemed to correlate with decreasing age at inoculation time, although there was considerable strain dependence. In order to correlate replication levels in thymus with clinical progress in mice, animals under 24 h of age were inoculated with XJ. At 14 days pi apparently healthy mice from this batch were separated from those presenting severe neurologic sings. In the asymptomatic mice, thymus titers ranged from 1.7 to 3.2 log, while no virus was found in thymus harvested from obviously ill animals. However brain virus titers in the two groups proved similar. To confirm these findings, 72 h old Wistar rats were inoculated in with 10(4) pfu of either Junin virus strain: with XJ strain (90

survival) virus could be readily isolated from thymus and bone marrow at day 7 pi, whereas with XJCl3 (5

survival) no virus could be rescued from any organ tested. Therefore, our results strongly suggest a close correlation between productive thymic infection and Junin virus persistence establishment in these rodents, depending on immune response regulation rather than on viral variation.

Junin virus infection of Callithrix jacchus: pathologic features.

Infection of Callithrix jacchus, a New World primate, with the prototype strain of Junin virus produced a severe disease. The animals developed multifocal hemorrhages and characteristic microscopic lesions such as meningoencephalitis, interstitial pneumonia, lymphocytic depletion of lymphatic tissue, hepatocytic necrosis, and a variable decrease in bone marrow cellularity. High virus concentrations correlated with lesions, and with the presence of viral antigenic determinants as revealed by immunofluorescent methods. With the exception of central nervous system damage, the morphological features and immunohistochemical and viral findings were similar to those recorded in human Argentine hemorrhagic fever.

Alteration of blood coagulation and complement system in neotropical primates infected with Junin virus.

The neotropical primate Callithrix jacchus infected with Junin virus presented an acute disease with hematological and neurological manifestations and died 17 to 24 days after infection. This picture is similar to that of human Argentine hemorrhagic fever (AHF). Blood coagulation and complement studies were performed in ten C jacchus animals inoculated with 10(3) TCID50 of Junin virus, the prototype pathogenic XJ strain. Four monkeys were used as normal controls. Infected monkeys and normal controls were bled to death on days 7, 14, 17, and 21. A progressive decrease in the number of platelets was found after day 7 of infection. On day 21, the last monkey had a value of 24,000/microliters. The levels of blood clotting factors did not change until day 17, when a shortened partial thromboplastin time activated with Kaolin (PTTK) (36 sec) and increased factors VIII (192.2%) and VII-X (266.6%) were found. On day 21, the PTTK was prolonged (50.7 sec) and factors II, V, and VIII, were decreased. Thrombin time was found prolonged from day 14 onward. Fibrinogen and fibrin degradation products (FDPs) were increased on days 17 (754 mg/dl and 9.2 microliters/ml) and 21 (457 mg/dl and 29.4 micrograms/ml). No changes in the levels of alpha 2 macroglobulin were observed. Complement hemolytic levels were found to be low on day 7 (58.3 UCH50, increased on day 14 (165.1), and within normal range at the end of infection (107.2). C3 levels showed a similar pattern. The bone marrow was active and hypercellular, and the number and morphology of megakaryocytes were normal in all but one of infected animals. The results of blood clotting suggest a limited activation. The complement system presented a profile of activation followed by a rebound phenomenon. The activation of complement appeared ten days before the alteration of the clotting system was evident.

Junin virus infection in genetically athymic mice.

The progression of Junin virus infection was studied in congenitally athymic mice. Immunocompetent littermates were used as infected controls. As expected, the latter developed lethal encephalitis, with viremia and considerable viral replication in the brain. The mortality rate was almost 100%; the few surviving controls exhibited high serum neutralizing antibody levels and a total absence of virus in blood and brain. In contrast, nude mice did not contract the disease; all survived with persistent viremia and virus in brain, but no serum neutralizing antibodies were detected. These results confirm previous research on thymectomized mice and those treated with anti-lymphocyte serum and tend to support the important role of cellular immunity in the pathogenesis of this viral disease.