Experimental infection of dogs with a feline endogenous retrovirus RD-114

<p>Abstract</p> <p>Background</p> <p>The feline endogenous retrovirus RD114 is contained in the genome of cats. The virus may contaminate live canine vaccines based on cultured feline cells. The <it>in vivo </it>infectivity, acute and subacute pathogenicity, and viral proliferation of the RD114 virus were evaluated by experimental infection of dogs.</p> <p>Methods</p> <p>Nine specific pathogen free dogs were divided into three groups, with each group consisting of one female and two male dogs. Dogs were subcutaneously inoculated in the neck with either 1 ml RD114 stock virus (group A), inactivated RD114 virus suspension (group B), or cell culture medium (group C) as a negative control. To assess blood cell counts and biochemical properties, blood samples from each group were collected 5 days before inoculation, just prior to inoculation, and 1, 3, 7 and 10 days post-inoculation.</p> <p>Result</p> <p>During the experimental period of 51 days, none of the dogs inoculated with RD114 virus showed any clinical signs, significant increases in rectal temperature or abnormal blood biochemical characteristics including C-reactive protein when compared with the negative controls. We were not able to re-isolate the RD114 virus from buffy coat cells of group A dogs. Additionally, we could not detect RD114 provirus in the genomic DNA isolated from peripheral blood leukocytes, lymph node, spleen and sternal bone marrow cells.</p> <p>Conclusions</p> <p>Signs of RD114 virus proliferation were not found after subcutaneous infection of dogs. Although the potential risk caused by infection with RD114 virus in dogs could not be assessed in this study, we suspect that RD114 virus has little or no virulence in dogs.</p

Spontaneous lymphomas in SJL/J-(v+) mice: ecotropic and dualtropic virus expression in normal and lymphomatous tissues.

Approximately 60% of inbred SJL/J-(v+) adult mice having high levels of ecotropic endogenous XC+ virus showed virus activation within the first month of life, while the others produced virus at comparable levels later on, in an attempt to correlate the time of virus activation with the incidence and latency of lymphomas, the tails of 57 1- and 2-month-old mice were tested for virus presence, and the mice were then observed for lymphoma appearance. While all 2-month-old mice expressed ecotropic virus, only 63% of the 1-month-old mice were virus-positive. However no relationship existed between early virus production (within 1 month) or late virus production and lymphoma latency, total lymphoma incidence, and histopathology. In contrast with high titers of XC+ virus in tail tissues of diseased mice, a markedly low virus content was found in lymphomatous organs. This difference was not due to selective growth of poor virus-producer cells or to inhibitory factors possibly released by the inflammatory cell component. Viral protein content and XC+ virus titer were not closely correlated in the neoplastic organs. Search for XC- viruses revealed that only 1 of 6 aged normal and 16 of 19 lymphomatous mice produced viruses that grew on mink lung cells. By use of a standard limiting dilution cloning procedure, four isolates were obtained that showed tropism for both murine and heterologous cells. Three of these isolates induced cytopathic changes similar to those induced by MCF viruses on mink lung cells but not on mouse cells. Interference and neutralization assays performed to better characterize the virus envelope properties further indicated that SJL/J isolates had features typical of MCF dualtropic viruses

Koala retroviruses: Characterization and impact on the life of koalas

Koala retroviruses (KoRV) have been isolated from wild and captive koalas in Australia as well as from koala populations held in zoos in other countries. They are members of the genus Gammaretrovirus, are most closely related to gibbon ape leukemia virus (GaLV), feline leukemia virus (FeLV) and porcine endogenous retrovirus (PERV) and are likely the result of a relatively recent trans-species transmission from rodents or bats. The first KoRV to be isolated, KoRV-A, is widely distributed in the koala population in both integrated endogenous and infectious exogenous forms with evidence from museum specimens older than 150 years, indicating a relatively long engagement with the koala population. More recently, additional subtypes of KoRV that are not endogenized have been identified based on sequence differences and host cell receptor specificity (KoRV-B and KoRV-J). A specific association with fatal lymphoma and leukemia has been recently suggested for KoRV-B. In addition, it has been proposed that the high viral loads found in many animals may lead to immunomodulation resulting in a higher incidence of diseases such as chlamydiosis. Although the molecular basis of this immunomodulation is still unclear, purified KoRV particles and a peptide corresponding to a highly conserved domain in the envelope protein have been shown to modulate cytokine expression in vitro, similar to that induced by other gammaretroviruses. While much is still to be learned, KoRV induced lymphoma/leukemia and opportunistic disease arising as a consequence of immunomodulation are likely to play an important role in the stability of koala populations both in the wild and in captivity