Feline leukaemia virus: protective immunity is mediated by virus‐specific cytotoxic T lymphocytes

Abstract

Summary Feline leukaemia virus (FeLV) nucleic acid vaccination of domestic cats affords protection against viraemia and the development of latency without inducing antiviral antibodies. 1 To determine the contribution of cell‐mediated immunity to the control of virus replication and clearance from the host, FeLV‐specific cytotoxic T lymphocyte (CTL) responses were compared in vaccine‐protected, transiently viraemic, and persistently viraemic cats. Vaccinal immunity was associated with the detection of higher levels of virus‐specific effector CTL in the peripheral blood and lymphoid organs to FeLV Gag/Pro and Env antigens than those observed in unvaccinated control, persistently viraemic cats (P < 0·001). Likewise, higher levels of virus‐specific CTLs were also observed in transiently viraemic cats which recovered following exposure to FeLV. In cats that controlled their infection, recognition of Gag/Pro antigens was significantly higher than the recognition of Env antigens. This is the first report highlighting the very significant role that virus‐specific CTL have in determining the outcome of FeLV infection in either vaccinated cats or cats recovering naturally from FeLV exposure.

Feline Leukemia Virus DNA Vaccine Efficacy Is Enhanced by Coadministration with Interleukin-12 (IL-12) and IL-18 Expression Vectors

“…The induction of FeLV-specific cytotoxic T cells following vaccination and before challenge could not be investigated in this study. It may be significant, however, that very much higher levels of effector CTL were demonstrated in a selection of the vaccinated, protected cats than in viremic or naturally recovered cats that were tested subsequently (14).…”

“…Viremic cats are anergic to FeLV proteins, showing little evidence of an immune response to the virus, and are at very high risk of developing a fatal disease within 2 to 4 years. In contrast, recovered cats produce virus neutralizing antibodies (20) and FeLV-specific cytotoxic T cells (CTLs) (14), are resistant to reinfection, and do not develop FeLV-related diseases (20). A third possible outcome is the establishment of a "latent" infection, in which cats are not viremic but have a covert infection of bone marrow cells and, like fully recovered cats, have virus-neutralizing antibodies (43).…”

Longitudinal Analysis of Feline Leukemia Virus-Specific Cytotoxic T Lymphocytes: Correlation with Recovery from Infection

“…These persistently infected cell lines express all FeLV structural antigens, thereby enabling detection of CTL specificities that might be overlooked using recombinant vaccinia viruses to deliver FeLV antigens. Microcytotoxicity assays were performed as described previously (13).…”

“…High levels of FeLVspecific CTLs were detected in the blood and lymphoid tissues of FeLV DNA-vaccinated, protected cats, implicating this mechanism in the observed protection (13). However, there are no reports detailing the temporal coevolution of virusspecific cell-mediated immunity and the control of viremia in cats that recover following exposure to FeLV.…”

Vírus da leucemia felina: análise da classificação da infecção, das técnicas de diagnóstico e da eficácia da vacinação com o emprego de técnicas sensíveis de detecção viral

“…Se o animal não desenvolve imunidade adequada, o vírus é disseminado sistemicamente por linfócitos e monócitos. A antigenemia/viremia é transiente, pois é detectável por cerca de três a seis semanas, ocorrendo completa eliminação do vírus após esse período (LUTZ et al, 1980;FLYNN et al, 2000;FLYNN et al, 2002); infecção latente -O animal apresenta antigenemia/ viremia por mais de três semanas e ocorre infecção de células da medula óssea (ROJKO et al, 1979;HARTMANN, 2006). Dentro de meses, o animal desenvolve uma resposta imune capaz de eliminar a antigenemia/viremia, mas o DNA proviral está presente nas células precursoras da medula.…”