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Similar to human immunodeficiency virus, feline immunodeficiency virus (FIV) induces immunodeficiency and enhanced susceptibility to secondary pathogens. To explore cytokine alterations in lentivirus immunodeficiency, constitutive mRNA expression was measured in lymph nodes of healthy and FIV-infected cats before and after challenge with Toxoplasma gondii. Cytokine mRNA expression was similar in control and FIV-infected cats during the first 10 weeks after infection. At 16 weeks, interferon (IFN)-gamma, tumor necrosis factor-alpha, and interleukin (IL)-10 mRNA were increased in FIV-infected cats. Challenge with T. gondii induced an increase in IL-2, IFN-gamma, and IL-12 in the lymph nodes of control cats, whereas IFN-gamma and IL-10 but not IL-2 or IL-12 increased in the lymph nodes of FIV-T. gondii coinfected cats. These results indicate that FIV immunodeficiency may derive from a failure to generate an IL-12-dependent type 1 response and that an elevated level of IL-10 mRNA expression is a predictor of lentivirus immunodeficiency.

To better define the relationship between ovine lentivirus (OvLV) infection and respiratory disease, pulmonary leukocytes and postmortem lung specimens from 42 sheep seropositive or at risk for OvLV infection were obtained. The lungs were examined for lesions of lymphoid interstitial pneumonia (LIP), and animals were categorized into five groups by severity of LIP and OvLV serologic status. The presence of OvLV in alveolar macrophages was established by proviral DNA amplification using the polymerase chain reaction (PCR), and the proportion of infected cells was determined by a quantitative focal immunoassay (FIA) and by immunohistochemistry. The concentration of OvLV p25 in serum was measured by capture ELISA. In contrast to animals with mild or no pulmonary lesions, sheep with moderate or severe LIP (17/42) were all seropositive, 71% had antigenemia (greater than 2 ng/mL), and 82% had proviral DNA in 1.5 x 10(5) alveolar macrophages. Of sheep positive by PCR, those with moderate or severe LIP (79%) had an average of 3 infected cells/10(3) alveolar macrophages by FIA. These results implicate alveolar macrophages as important target cells in the pathogenesis of OvLV-induced respiratory diseases.