Detection and immune cell response of natural maedi visna virus (MVV) infection in Indian sheep and goats

Maedi is a lentiviral disease characterized by progressive interstitial pneumonia with humoural as well as cell mediated immune response. The present investigation was designed to detect the presence of MVV in different biological samples and to evaluate the immune response in naturally MVV infected sheep and goats. Total of 701 biological samples (289 lung tissues, 233 blood, 54 brain tissues, 74 mammary gland tissues and 51 joint tissues were screened for the MVV by nested PCR. MVV nucleic acid was detected in 10.41% of samples and it was observed that sheep samples showed positivity of 8.7% and goat samples 12.6%. Blood samples showed highest positivity (14.59%) followed by joint tissue (13.72), lungs (8.6%), mammary gland (8.1%) and brain (1.85%). MVV p28 antigen was detected in the cytoplasm of mononuclear cells, particularly in the macrophages of lungs and lymph nodes. Antibodies against SRLVs were detected by cELISA and seroprevalence of 19.58% was observed in both sheep and goats serum samples. The seropositivity was higher in sheep (22.9%) as compared to the goats (15.59%). IHC was done to identify the nature of the immune cells infiltrated in the MVV infected tissues and it was observed that B cells, CD8+ and macrophages were the predominant immune cells infiltrated in the lungs showing MVV infection. Expression of the cytokines was assessed by real time PCR and it was observed that expression of IL-10, IFN-γ, TNFα, IL-4, IL-2 and IL6 was down regulated in most of the cases but few samples showed upregulation. In conclusion, MVV is circulating in the sheep and goat population of the India and the disease causes altered immune response in the animal which may make the infected animals more prone to other infectious diseases.