Pathogenesis of a pichinde virus strain adapted to produce lethal infections in guinea pigs. (49/73)

A model for studying the pathogenesis of virulent arenavirus infection was developed by adapting Pichinde virus to produce lethal infections of inbred guinea pigs. This adapted Pichinde virus retained low virulence for primates, thus potentially reducing the biohazard to investigators. Whereas all inbred (strain 13) guinea pigs were infected and killed by 3 plaque-forming units or more of adapted Pichinde virus injected subcutaneously, outbred (Hartley strain) guinea pigs were relatively resistant. All infected, inbred guinea pigs died at 13 to 19 days after inoculation, with viremias in excess of 5 log(10) plaque-forming units/ml, severe lymphopenia (<1,000/mm(3)), and elevated serum glutamic oxaloacetic acid transaminase levels. Immunofluorescent antibody examination of tissues and infectivity titrations of tissue homogenates obtained at 3- to 4-day intervals demonstrated significant viral replication in all visceral tissues examined, but not in brain. Livers of all moribund guinea pigs contained moderate to severe hepatocellular necrosis and diffuse fatty change. Splenic red pulp and adrenal cortical tissues were engorged with blood and contained necrotic foci. Pancreatic acinar tissues were atrophied and vacuolated; lung sections typically contained areas of moderate to severe interstitial pneumonia. Inflammatory cells were conspicuously absent from all lesions. The virological and pathological features of adapted Pichinde infection in guinea pigs are remarkably similar to those described for Lassa virus infections in rhesus monkeys and humans, suggesting that this model might provide insight into the pathogenesis and treatment of Lassa fever in humans.  (+info)

Persistent infection of Vero cells with Tacaribe virus. (50/73)

Persistently infected cultures have been established from Vero cells surviving primary infection with Tacaribe virus (Vero-T). The growth rate and morphological characteristics of the persistently infected cells were indistinguishable from normal Vero cells. Virus release declined during the first 6 passages, a cyclical pattern was observed between passages 6 and 16, and subsequently no virus infectivity could be detected. Co-cultivation with normal RK-13 or Vero cells enhanced virus yield from virus-producing cultures of Vero-T cells (passage 15), but the addition of susceptible cells had no effect on non-producer Vero-T cultures (passage 19). Only a small proportion (less than 1%) of the persistently infected cells tested during the first 16 passages produced infectious virus. The virus released during the early stages of persistence was temperature-sensitive if grown at 40 degree C, more thermolabile at 50 degree C than parental virus, and unable to initiate a persistent infection in Vero cells. Vero-T cells consistently showed refractoriness to homotypic Tacaribe virus superinfection and a selective graded resistance to other arenavirus replication. The possible use of viral susceptibility of persistently infected cultures as marker of antigenic relationship among Tacaribe complex viruses if considered.  (+info)

In vitro infection of murine macrophages with Junin virus. (51/73)

Mouse peritoneal macrophages were successfully infected with two strains of Junin virus producing high titers with no apparent cell damage. Infected cultures survived longer than noninfected cultures. The pattern of virus release suggested a persistent infection. Virus replication was delayed in macrophages from mice previously immunized with Junin virus. These results support the opinion that macrophages are targets for virus replication in vivo infections.  (+info)

Cross-protection in nonhuman primates against Argentine hemorrhagic fever. (52/73)

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.  (+info)

Arenavirus defective interfering particles mask the cell-killing potential of standard virus. (53/73)

Lymphocytic choriomeningitis virus (LCM) and Pichinde virus grew readily and produced cytopathology in MDCK and PK-15 cells. It is known that in these cell lines, the synthesis or function of defective interfering (DI) virus particles is restricted. Survival curves of single MDCK cells infected with low multiplicities of LCM showed one-particle-to-kill kinetics. At high multiplicities of infection, there was a maximum degree of cell-killing, or even a reduction in the amount of cell-killing, depending on how much DI virus was present in a particular standard virus stock. DI LCM virus could completely prevent standard virus from producing c.p.e. in MDCK monolayers with one-particle-to-protect kinetics. It could still prevent killing of the cells when added within a short time after infection with standard virus, but was able to interfere with synthesis of standard virus when added even later, On passage of LCM or Pichinde virus without dilution in MDCK cells, there was no homologous auto-interference. Furthermore, there was only slight interference with the synthesis of standard virus when these cells were pre-treated with DI virus.  (+info)

Synthesis of virus-specific polypeptides and genomic RNA during the replicative cycle of Pichinde virus. (54/73)

A stock of plaque-purified Pichinde virus, prepared under conditions designed to limit the amounts of defective interfering virus, was used to infect BHK cells. At daily intervals after infection, cells were examined for infectious and radiolabeled virus particle production and for the synthesis of virus-specific polypeptides. Quantitative comparisons were also made of the concentrations of genomic Pichinde virus L and S RNAs in the cytoplasm of infected cells on different days after infection. Our results showed that virus particle production, rates of protein synthesis, and the intracellular levels of viral genomic RNAs all increased and decreased with similar kinetics, and that this regulation was independent of the cell growth cycle. We were unable to relate these changes in viral macromolecule and virus production to the appearance of readily identifiable defective interfering particles. Our findings suggest that regulation of virus replication early during the replicative cycle of Pichinde virus may not be dependent upon the generation of defective interfering virus.  (+info)

Gene mapping in Pichinde virus: assignment of viral polypeptides to genomic L and S RNAs. (55/73)

Previous studies have demonstrated that Pichinde virus encodes at least three primary translation products. Using wild-type Pichinde and Munchique viruses and a reassortant between the two, designated RE-2, we were able to assign polypeptides L, GPC, and NP to viral L and S RNAs. The RE-2 virus contains the L RNA of Pichinde virus and the S RNA of Munchique virus. Two-dimensional tryptic peptide mapping of L-[35S]methionine-containing peptides demonstrated that NP and GPC were identical in Munchique and RE-2 viruses, and both differed from the corresponding Pichinde virus tryptic profiles. On the basis of this, NP and GPC must be encoded by viral S RNA. Similar comparisons for L polypeptide demonstrated that L is a virus-specific polypeptide encoded by L RNA.  (+info)

In vivo replication of pathogenic and attenuated strains of Junin virus in different cell populations of lymphatic tissue. (56/73)

Lymphatic tissue is one of the main sites for replication of Junin virus. To characterize which cells are involved in that replication, the presence of Junin virus in purified populations of macrophages and dendritic cells from the spleens of guinea pigs infected with pathogenic and attenuated strains was investigated by immunofluorescence and intracerebral inoculation into newborn mice. The pathogenic strain was present both in macrophages and in dendritic cells, but the attenuated strain selectively infected dendritic cells. These observations suggest that the pathogenic behavior and replication efficiency of these two strains of Junin virus may be related to a difference in cell targets.  (+info)