Morphological and immunological comparison of caprine arthritis encephalitis and ovine progressive pneumonia viruses

Caprine arthritis encephalitis virus (CAEV) causes a variety of pathological conditions ranging from mild to very severe and from acute to chronic, depending upon the age of initial infection and other variables. Although the virus has been reported to have properties of characteristic of retroviruses and to be related to maedi-visna virus (also called progressive pneumonia virus [PPV]), relatively little information about its morphological and immunological characteristics has been reported. We describe the morphological features of CAEV replicating in cultured caprine cells. Although the virus replicates slowly and very little virus is released from productively infected cells, it is apparent that the morphogenesis of CAEV is strikingly similar to that of maedi-visna. After the transmission of CAEV to a more permissive permanent cell line derived from Himalayan tahr ovary, it was possible to grow and purify enough virus to initiate biochemical characterization. The structural proteins of CAEV are generally very similar to those of PPV, suggesting that the two viruses are closely related but not identical. This was substantiated by showing that serum from a CAEV-infected goat immunoprecipitated both CAEV and PPV virion structural antigens from extracts of radiolabeled virus and also precipitated putative nonstructural viral antigens from extracts of both CAEV- and PPV-infected cells.