Antígenos inactivados de virus Junín / Inactivated Junín virus antigens

El objetivo de este trabajo fue obtener un antígeno inactivado de virus Junín capaz de inducir protección en cobayos contra el desafío con la cepa XJ prototipo. Se utilizó como antígeno, la cepa XJ-Clon 3 replicada en cerebro de ratón y se ensayaron tres métodos de inactivación: formaldehido, acetona y calor. Con formaldehido se emplearon 3 dosis: concentración final de 0,05% durante 24 h, 0,2% durante 2 n y 0,05% durante 3 h. Las curvas de inactivación demostraron que en el primer caso, el virus se inactiva a la h de exposición mientras que en el segundo se logra ya a los 30 min. Aunque el formaldehido demostró ser un inactivante eficaz, ninguno de los antígenos preparados protegió a los cobayos contra el desafío XJ. No se observó retraso significativo en la fecha de muerte ni modificación en las curvas de peso con respecto a los controles desafiados y sin inmunizar. Todos los animales murieron con el cuadro hemorrágico típico de FHA, excepto el grupo que recibió la dosis máxima de antígeno inactivado con formaldehido en el que se observó mortalidad en ausencia de cuadro hemorrágico. Los antígenos inactivados con calor (37-C 48 h) o con acetona tampoco resultaron eficaces en la protección de cobayos. Solamente los antígenos inactivados con formaldehido desencadenaron una respuesta inmune no protectora, evidenciada por los bajos títulos de anticuerpos inmunofluorescentes y fijadores de complemento; por el contrario, no se detectaron anticuerpos neutralizantes. Se discuten las posibles causas de la no protección así como los riesgos de vacunas a virus vivos y atenuados versus vacunas a virus inactivados para Fiebre Hemorrágica Argentina

Antígenos inactivados de virus Junín / Inactivated Junín virus antigens

El objetivo de este trabajo fue obtener un antígeno inactivado de virus Junín capaz de inducir protección en cobayos contra el desafío con la cepa XJ prototipo. Se utilizó como antígeno, la cepa XJ-Clon 3 replicada en cerebro de ratón y se ensayaron tres métodos de inactivación: formaldehido, acetona y calor. Con formaldehido se emplearon 3 dosis: concentración final de 0,05% durante 24 h, 0,2% durante 2 n y 0,05% durante 3 h. Las curvas de inactivación demostraron que en el primer caso, el virus se inactiva a la h de exposición mientras que en el segundo se logra ya a los 30 min. Aunque el formaldehido demostró ser un inactivante eficaz, ninguno de los antígenos preparados protegió a los cobayos contra el desafío XJ. No se observó retraso significativo en la fecha de muerte ni modificación en las curvas de peso con respecto a los controles desafiados y sin inmunizar. Todos los animales murieron con el cuadro hemorrágico típico de FHA, excepto el grupo que recibió la dosis máxima de antígeno inactivado con formaldehido en el que se observó mortalidad en ausencia de cuadro hemorrágico. Los antígenos inactivados con calor (37-C 48 h) o con acetona tampoco resultaron eficaces en la protección de cobayos. Solamente los antígenos inactivados con formaldehido desencadenaron una respuesta inmune no protectora, evidenciada por los bajos títulos de anticuerpos inmunofluorescentes y fijadores de complemento; por el contrario, no se detectaron anticuerpos neutralizantes. Se discuten las posibles causas de la no protección así como los riesgos de vacunas a virus vivos y atenuados versus vacunas a virus inactivados para Fiebre Hemorrágica Argentina (AU)

Nasal and intrathalamic inoculations of primates with Tacaribe virus: protection against Argentine hemorrhagic fever and absence of neurovirulence.

Callithrix jacchus marmosets were inoculated by different routes with two stocks of Tacaribe virus, one from suckling mouse brain and another from human diploid MRC5 cells. All 12 primates inoculated by nasal route developed neutralizing serum antibodies without any clinical signs. All 6 primates receiving the mouse brain-Tacaribe virus were protected against lethal challenge with pathogenic XJ strain of Junin virus, while protection was also conferred in 4 out of 6 primates receiving the diploid cell-Tacaribe virus stock. Intramuscular (i.m.) inoculation also elicited antibodies and conferred protection to 4 primates receiving the diploid cell-virus stock. Intrathalamic (i.t.) inoculation of mouse brain-virus stock caused no clinical signs or histopathologic changes in groups of 3 primates each examined on days 33 and 90 post-infection (p.i.). All primates developed antibody response, but no virus could be detected in their brain. Thus, Tacaribe virus proved harmless and immunogenic in Callithrix jacchus and protected most marmosets against challenge with the lethal XJ strain of Junin virus.

[Detection of laboratory infections caused by Junín virus using the neutralization and immunofluorescence technics comparatively]. / Detección de infecciones de laboratorio por virus Junín utilizando comparativamente las técnicas de neutralización e inmunofluorescencia.

To study Junin virus infection among laboratory workers and to compare immunofluorescence and neutralization tests, blood samples were taken from 48 individuals, of which 42 were considered high risk personnel. None of the 16 low risk workers exhibited antibodies. Neutralizing antibodies were detected in 15 high risk laboratory workers. Nine of the latter were already known to carry antibodies from a previous survey in 1978. Titers detected were either at previous levels or slightly higher. Of the remaining 6 out of the 15 positive cases, 3 showed mild clinical and subclinical infection, equivalent to a 12% incidence rate over the 1978-1980 period. An adequate correlation was observed between neutralization and immunofluorescence test: 66.6% for both positive tests and 97.1% for both negative tests. Although the immunofluorescence test ies easier to perform the neutralization test appears to be more reliable clinically. The overall prevalence rate of neutralizing antibodies among non-vaccinated personnel was almost 19%, which warns against the health hazard involved in Junin virus handling.

[Infection of New World primates with Junín virus. IV. Aotus trivirgatus]. / Infección de primates del nuevo mundo con virus Junín. IV. Aotus trivirgatus.

Owl monkeys (Aotus trivirgatus) were inoculated with XJ, a pathogenic strain of Junin virus, seeking new animal models for Argentine Hemorrhagic Fever. Nine monkeys were inoculated intramuscularly with 30 or 300,000 TCID50 of junin virus. Hematological and virological studies showed no alteration in blood elements such as red cell, reticular cell and platelets, up to 28 days after inoculation. Hemoglobin and hematocrit determinations also remained constant. However, significant neutropenia was seen at day 11 and minimal viremia was detected in some animals during the second and third week post-inoculation. No clinical or behavioral modifications were observed during the eighty-days observation period. Non-specific necropsy findings included pyelonephritis, pneumonitis, liver abscess and eosinophilic spleen infiltrate. All of these findings seem to be unrelated to Junin virus inoculation. No virus was present in organs of animals killed 29, 57 or 85 days post-inoculation. All nine owl monkeys developed serum neutralizing antibodies by day 22. It is concluded that the owl monkey suffers a subclinical infection when inoculated with Junin virus, similar to that seen in other primate species (Saimiri sciureus and Alouatta caraya).

Infección de primates del nuevo mundo con virus Junín. IV. Aotus trivirgatus / [Infection of New World primates with Junín virus. IV. Aotus trivirgatus]

Owl monkeys (Aotus trivirgatus) were inoculated with XJ, a pathogenic strain of Junin virus, seeking new animal models for Argentine Hemorrhagic Fever. Nine monkeys were inoculated intramuscularly with 30 or 300,000 TCID50 of junin virus. Hematological and virological studies showed no alteration in blood elements such as red cell, reticular cell and platelets, up to 28 days after inoculation. Hemoglobin and hematocrit determinations also remained constant. However, significant neutropenia was seen at day 11 and minimal viremia was detected in some animals during the second and third week post-inoculation. No clinical or behavioral modifications were observed during the eighty-days observation period. Non-specific necropsy findings included pyelonephritis, pneumonitis, liver abscess and eosinophilic spleen infiltrate. All of these findings seem to be unrelated to Junin virus inoculation. No virus was present in organs of animals killed 29, 57 or 85 days post-inoculation. All nine owl monkeys developed serum neutralizing antibodies by day 22. It is concluded that the owl monkey suffers a subclinical infection when inoculated with Junin virus, similar to that seen in other primate species (Saimiri sciureus and Alouatta caraya).

Detección de infecciones de laboratorio por virus Junín utilizando comparativamente las técnicas de neutralización e inmunofluorescencia. / [Detection of laboratory infections caused by Junín virus using the neutralization and immunofluorescence technics comparatively]

To study Junin virus infection among laboratory workers and to compare immunofluorescence and neutralization tests, blood samples were taken from 48 individuals, of which 42 were considered high risk personnel. None of the 16 low risk workers exhibited antibodies. Neutralizing antibodies were detected in 15 high risk laboratory workers. Nine of the latter were already known to carry antibodies from a previous survey in 1978. Titers detected were either at previous levels or slightly higher. Of the remaining 6 out of the 15 positive cases, 3 showed mild clinical and subclinical infection, equivalent to a 12

incidence rate over the 1978-1980 period. An adequate correlation was observed between neutralization and immunofluorescence test: 66.6

for both positive tests and 97.1

for both negative tests. Although the immunofluorescence test ies easier to perform the neutralization test appears to be more reliable clinically. The overall prevalence rate of neutralizing antibodies among non-vaccinated personnel was almost 19

, which warns against the health hazard involved in Junin virus handling.

Infección de primates del nuevo mundo con virus Junín. IV. Aotus trivirgatus. / [Infection of New World primates with Junín virus. IV. Aotus trivirgatus]

Owl monkeys (Aotus trivirgatus) were inoculated with XJ, a pathogenic strain of Junin virus, seeking new animal models for Argentine Hemorrhagic Fever. Nine monkeys were inoculated intramuscularly with 30 or 300,000 TCID50 of junin virus. Hematological and virological studies showed no alteration in blood elements such as red cell, reticular cell and platelets, up to 28 days after inoculation. Hemoglobin and hematocrit determinations also remained constant. However, significant neutropenia was seen at day 11 and minimal viremia was detected in some animals during the second and third week post-inoculation. No clinical or behavioral modifications were observed during the eighty-days observation period. Non-specific necropsy findings included pyelonephritis, pneumonitis, liver abscess and eosinophilic spleen infiltrate. All of these findings seem to be unrelated to Junin virus inoculation. No virus was present in organs of animals killed 29, 57 or 85 days post-inoculation. All nine owl monkeys developed serum neutralizing antibodies by day 22. It is concluded that the owl monkey suffers a subclinical infection when inoculated with Junin virus, similar to that seen in other primate species (Saimiri sciureus and Alouatta caraya).

Cross-protection in nonhuman primates against Argentine hemorrhagic fever.

The susceptibility of the marmoset Callithrix jacchus to Tacaribe virus infection was investigated to perform cross-protection studies between Junin and Tacaribe viruses. Five marmosets inoculated with Tacaribe virus failed to show any signs of disease, any alterations in erythrocyte, leukocyte, reticulocyte, and platelet counts or any changes in hematocrit or hemoglobin values. No Tacaribe virus could be recovered from blood at any time postinfection. Anti-Tacaribe neutralizing antibodies appeared 3 weeks postinfection. The five Tacaribe-infected marmosets and four noninfected controls were challenged with the pathogenic strain of Junin virus on day 60 post-Tacaribe infection. The former group showed no signs of disease, no viremia, and no challenge virus replication, whereas the control group exhibited the typical symptoms of Argentine hemorrhagic fever, high viremia, and viral titers in organs. Soon after challenge, the Tacaribe-protected marmosets synthesized neutralizing antibodies against Junin virus. These results indicate that the marmoset C. jacchus can be considered an experimental model for protection studies with arenaviruses and that the Tacaribe virus could be considered as a potential vaccine against Junin virus.

Infeccion de primates del Nuevo Mundo con virus Junin: III Saimiri sciureus / Infection of New World primates with Junin virus. III Saimiri sciureus

Cuatro primates neotropicales de la especie S. sciureus fueron inoculados con la cepa patogena prototipo XJ del virus Junin a fin de determinar su susceptibilidad a la misma. Dos S. sciureus fueron inoculados por via intramuscular con 10(3) DL50 de dicha cepa, y las dos restantes con 10 (5) DL50. Independentemiente de las dosis de virus administrada, ninguno de los monos inoculados mostro signos clinicos de enfermedad hasta la fecha en que se los sacrifico (entre 82 y 178 dias despues de la infeccion), para realizar estudios histologicos y de persistencia viral. No se detectaron modificaciones significativas en el numero de hematies, reticulocitos, plaquetas y leucocitos. La busqueda de virus en sangre entre los 7 y 36 dias despues de la infeccion, dio resultados negativos. Tampoco se detecto la presencia de virus infeccioso, de antigeno viral o de modificaciones histologicas, en los organos de los animales sacrificados. Tres de los 4 monos infectados desarrollaron anticuerpos neutralizantes humorales antivirus Junin

Infeccion de primates del Nuevo Mundo con virus Junin: III Saimiri sciureus / Infection of New World primates with Junin virus. III Saimiri sciureus

Cuatro primates neotropicales de la especie S. sciureus fueron inoculados con la cepa patogena prototipo XJ del virus Junin a fin de determinar su susceptibilidad a la misma. Dos S. sciureus fueron inoculados por via intramuscular con 10(3) DL50 de dicha cepa, y las dos restantes con 10 (5) DL50. Independentemiente de las dosis de virus administrada, ninguno de los monos inoculados mostro signos clinicos de enfermedad hasta la fecha en que se los sacrifico (entre 82 y 178 dias despues de la infeccion), para realizar estudios histologicos y de persistencia viral. No se detectaron modificaciones significativas en el numero de hematies, reticulocitos, plaquetas y leucocitos. La busqueda de virus en sangre entre los 7 y 36 dias despues de la infeccion, dio resultados negativos. Tampoco se detecto la presencia de virus infeccioso, de antigeno viral o de modificaciones histologicas, en los organos de los animales sacrificados. Tres de los 4 monos infectados desarrollaron anticuerpos neutralizantes humorales antivirus Junin

Cell-mediated immunity and lymphocyte populations in experimental Argentine hemorrhagic fever (Junín Virus).

Guinea pigs infected with the XJ prototype strain of Junín virus reproduce the main features of Argentine hemorrhagic fever, showing hemorrhages, leukothrombocytopenia, and focal lymphoid tissue necrosis. Viral lymphotropism is shown by the presence of viral antigens, severe cytopathic effect, and high virus titers in lymphoid organs. A pronounced depression of humoral immune response to sheep erythrocytes as well as to the virus is described. This study was carried out to determine whether cellular immune response was also modified and which cell populations were affected. Delayed hypersensitivity skin reaction to purified protein derivative was found to be markedly depressed after infection. A noticeable decrease in both percentages and absolute T lymphocyte numbers, detected by E rosettes, in spleen and lymph nodes, together with a low absolute T cell number in peripheral blood, were observed. Total cell counts in spleen, lymph nodes, and peripheral blood were also reduced. On the contrary, no modification in percentages of B lymphocytes, as measured by EAC rosettes, was found. These results indicate that cell-mediated immunity is markedly impaired in guinea pigs infected with the XJ strain of Junín virus. Its relationship with the pathogenesis of the disease is discussed.