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Biomedical subjects

G Carballal

Publications and source records attributed to G Carballal.

At least 37 records · Page 2Linked to original sources

Circulating interferon in the guinea pig infected with the XJ, prototype Junin virus strain.

The interferon (IFN) induction capacity of the XJ prototype strain of Junín virus (JV) was investigated in the guinea pig model. Circulating alpha IFN was detected in 50% of the animals from days 2 to 9 postinfection (pi) and in 100% at day 11 pi, when all animals were in the premortem stage. Individual levels ranged from 20 to 1,280 guinea pig IFN units (GPIFNU)/ml. A correlation between XJ strain virulence and IFN titers was recorded. A possible role of IFN as a pathogenic factor in the outcome of the disease is discussed.

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Epidemiology of Argentine hemorrhagic fever.

Present knowledge points to horizontal transmission as the most significant mechanism for Junín virus maintenance in the main natural reservoirs, namely Calomys musculinus and Calomys laucha. The existence of naturally infected Akodon azarae, both within and outside the endemic area, as well as the finding that other species, ecologically and phylogenetically related to the main reservoirs, such as Akodon molinae and Calomys callidus, can experimentally develop persistent infections with virus shedding through fauces, suggest a potential role for these cricetids as alternative reservoirs. Furthermore, since those rodents inhabit the borders of the area in which Argentine Hemorrhagic fever is endemic, the risk of spread of this area is to be expected. Whether the establishment of Junín virus persistence in Calomys musculinus and other reservoirs depends on viral or host factors, such as a selective defect in L3T4+ lymphocytes as recently shown for mice, remains to be explored.

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Mortality induced by adoptive immunity in Junin virus-infected athymic mice.

The effect of normal or sensitized spleen cell transfer from syngeneic euthymic mice to Junin virus-infected suckling athymic mice was studied. Transfer was performed 1 or 7 days after infection. In both cases, an acute lethal disease developed 6-11 days after transfer. The mortality reached 100% in all infected groups receiving normal or sensitized splenocytes, while it was negligible for different control groups of athymic mice. Transfer of normal or sensitized splenocytes was unable to significantly modify brain viral titers, as compared with infected nontransferred athymic mice killed after a 25-day observation period. Brain lesions were demonstrated in about half of the infected athymic mice transferred with sensitized splenocytes and in all euthymic infected mice. These results show that splenocyte transfer from immunocompetent donors is able to change the normal course of persistent Junin virus infection in nude mice to a lethal acute disease, thus pointing to a main role for T cells in its pathogenesis.

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Intracerebral infection of Cebus apella with the XJ-Clone 3 strain of Junín virus.

To assess the usefulness of the South American primate Cebus apella as a model for neurovirulence of Junín virus, eight monkeys were inoculated with 10(5) LD50 of the attenuated XJ-Clone 3 Junín virus strain by the intrathalamic route. After the second week, weight loss and polyadenopathies were observed in most animals, one-half of which had a transient leukothrombocytopenia. Moderate clinical central nervous system (CNS) involvement was present in four of eight monkeys, while the rest had only mild neurologic signs. All recovered except one, which developed a deep coma and was killed in a pre-mortem stage at 18 days post-infection (pi). Junín virus was isolated from the throat from five, from the blood from three, and from the brain from two monkeys. In the most severely ill animal, virus titers higher than viremia were detected in both inoculated and contralateral brain hemispheres, as well as in lung, lymph node, and small intestine. Junín antigens and "in vivo" bound immunoglobulins were detected by immunofluorescence (IF) in the brain of four animals at 18, 21, 40, and 155 days pi. Moderate lymphocytic parenchymal and meningeal infiltration were observed in the brain of four animals, and gliosis was also present in the most affected monkey. Although the clinical response to infection was not uniform, all infected monkeys developed high IF antibodies. Cebus apella cannot be used as a highly sensitive model for Argentine hemorrhagic fever (AHF). However, the results obtained show that the XJ-Clone 3 strain can replicate in the primate CNS and to induce lesions and immunoglobulin deposition. In addition, viral persistence is suggested by the late detection of viral antigens in brain at 40 and 155 days pi.

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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.

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Experimental infection of Akodon molinae (Rodentia, Cricetidae) with Junín virus.

Experimental infection with the XJ-Clone 3 strain of Junín virus in laboratory bred Akodon molinae, a cricetid rodent inhabiting the borders of endemic Argentine hemorrhagic fever areas, was studied. Suckling animals inoculated intracerebrally proved sensitive and became chronically infected. Sixty percent of the rodents showed neurologic involvement, with mortality reaching 60%. Virus was recovered from the brain at 7, 15, 21, 37, and 57 days postinfection (pi). By immunofluorescence (IF), viral antigens were observed up to 182 days pi in cells of the central nervous system (CNS). Concurrently, immunoglobulin deposits were detected in infected CNS cells from 21 up to 182 days pi. These deposits increased with the progression of the immune response as measured by IF antibodies. The detection of immune complexes in brain cells of apparently healthy animals suggests that neither viral replication nor the development of a humoral immune response are necessary requisites for neurovirulence in this host. Infection of adult rodents by different routes failed to induce disease or mortality and virus could not be recovered from oral swabs, blood, or organs. Our data suggest that Akodon molinae could play a role in nature as an alternative reservoir of Junín virus in addition to the main reservoir, Calomys musculinus.

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Junin virus access to CNS by extraneural rat inoculation.

This study was carried out to determine the pathways along which two strains of Junin virus (JV), the pathogenic XJV and the attenuated XJC13V, reach the CNS following IP inoculation of 2-day-old rats. A sequential study of infectivity and antigen distribution in peritoneal macrophages, spleen, and brain was performed. Mortality was 85% with the former strain, but only 15% with the latter. At 4-7 days PI, XJV-infected animals had viral antigen in 10% of peritoneal macrophages. Viremia and spleen virus lasted for 10-15 days. Low brain titers were detected at day 7, with a peak at day 15. Brain antigen correlated with virus titers. In contrast, XJC13V-infected rats, macrophage antigen appeared later and to a lesser degree (1% of cells). Viremia and spleen virus were transient, while both the titer of brain virus and the viral antigen proved lower. Antibody titers were over twofold higher for XJ-infected animals. It is suggested that the different replication rate at the inoculation site could account for the greater ability of the XJV strain to reach the CNS. A greater antigen mass and/or more numerous antigenic determinants presented by the macrophage could explain the higher antibody titers found in XJ-injected rats, which were unable, however, to prevent viral spread.

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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.

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Experimental Argentine hemorrhagic fever: myocardial involvement in Cebus monkey.

Four Cebus apella monkeys, to test a recently proposed model for testing neurovirulence of Junín virus (JV) strains, were intracerebrally infected with 10(5) LD50 of the XJ clone 3 strain of JV. There were no significant electrocardiographic abnormalities or gross lesions, but all infected monkeys exhibited a varying degree of histologic myocardial lesions including focal lymphoblastic infiltrates, vascular ruptures, and mild interstitial reactive change. One Cebus showed lymphocytic infiltrates in the caudal portion of the A-V node without specific cell involvement. These preliminary results demonstrate cardiac involvement in experimental infection of the Cebus monkey with Junín virus.

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Neurotropism of a high-passage XJ strain of Junín virus.

Guinea pig infection with a highly passaged XJ prototype strain of Junín virus by the intramuscular route (IM) was carried out in order to study viral tropism modification in this host. The neurotropism of this strain was demonstrated by viral isolation, meningitis, and by the presence of Junín antigens as shown by immunofluorescence. These events, not previously observed with the same lower-passaged strain, revealed the appearance of neurotropism after multiple passages in guinea pigs.

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Junin virus-induced chromosomal aberrations in the guinea pig. Synergism between the attenuated strain XJ-clone 3 and caffeine.

The frequency of chromosomal aberrations in bone marrow cells of guinea pigs inoculated with the pathogenic XJ strain of Junin virus increased significantly at 6, 9, and 11 days postinoculation (p.i.). Animals inoculated with the attenuated XJ-clone 3 strain only showed significant increments of achromatic lesions (gaps) at 9 days p.i. Guinea pigs inoculated with the XJ-clone 3 strain and then treated with two doses of caffeine 24 and 12 h before killing at 9 days p.i. exhibited a significant increase of chromatid breaks and a parallel decrease of gaps. Because caffeine acts as an inhibitor of repair mechanisms of genetic damage, these results suggest a mutagenic effect of the attenuated strain.

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The guinea pig model for Argentine hemorrhagic fever.

Guinea pigs infected by the peripheral route with the XJ pathogenic strain of Junin virus showed viscerotropism mainly in reticulo-phagocytic rich organs. By immunofluorescence, heavy infection of reticular-phagocytic cells was demonstrated, supporting the leading role of these cell types. Absence of neurotropism was demonstrated by the inability to recover infectious virus, as well as the absence of antigens, immunoglobulins, or 3rd component of complement deposits, in cells, vessels, or meninges. The correlation between infectivity and antigen expression observed in organs, and the absence of evidence of immunopathologic mechanisms, strongly suggest a direct viral effect in these experimental conditions. The results show that infection of guinea pigs by the peripheral route is an adequate model for human Argentine hemorrhagic fever with the exception of central nervous system involvement. Comparisons are made with infections produced in guinea pigs by attenuated strains, as well as with the disease in primates and humans.

Adrenal Glands↗

[Lack of viral persistence in 2 Cebus sp].

Two Cebus sp surviving acute Junin virus infection, one after intramuscular inoculation with pathogenic XJ and the other after intracerebral inoculation with XJ Clone 3, failed to exhibit persistent infection. Although treatment with immunosuppressive drugs was carried out, no Junin virus was detected in blood or organs in spite of blind passages in mice for the former as well as cocultivation with permissive Vero cells for the latter. Viremia was also ruled out by immunofluorescence on BHK/21 cell culture. These findings correlate with the lack of long-lasting virus in blood observed in humans following the acute phase of Argentine Hemorrhagic Fever.

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Cytogenetic effect of two strains of Junin virus in the guinea pig.

The cytogenetic effect of two strains of Junin virus on bone marrow chromosomes of the guinea pig was studied. Animals infected with the attenuated strain XJ-Cl3 showed no differences from control animals. Guinea pigs inoculated with the pathogenic strain XJ exhibited a significant increase of abnormal cells, chromatid breaks, and chromosome fragments. The clastogenic ability of the XJ strain is similar to the reported effect of other viruses, while the XJ-Cl3 strain does not appear to be clastogenic.

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Protection against a pathogenic strain of Junin virus by mucosal infection with an attenuated strain.

In order to determine the degree of mucosal infectivity of the attenuated XJCl3 strain of Junin virus, guinea pigs were orally or nasally inoculated. Infectivity was 85% for the oral and 100% for the nasal route, as detected by death or serum antibody development. The presence of serum antibodies was closely associated with resistance to challenge with the XJ pathogenic strain, which killed 100% of controls when inoculated by the parenteral or nasal route. However, mortality rates after mucosal infection were low, depending on the dose. Guinea pigs which survived nasal inoculation developed serum neutralizing antibodies, and were fully resistant to challenge with the XJ pathogenic strain.

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