Pathologic and serologic responses of isogeneic twin lambs to phenotypically distinct lentiviruses

Viral strain differences in the degree of lymphoid interstitial pneumonia (LIP) and in antibody responses to ovine lentivirus (OvLV) infection have been described in experimentally inoculated neonatal lambs. To rule out the possibility that these differences were due to differences in host genetic factors, one lamb from each of three sets of artificially produced identical twins was inoculated with a lytic strain of OvLV (85/34), and the corresponding twin was inoculated with a persistent strain (84/28). One lamb of a fourth set of twins was inoculated with the lytic strain of OvLV, and the corresponding twin was inoculated with a cell culture supernatant. The degree of LIP, as determined by histologic analysis of the lung sections collected at necropsy, was independent of the virus strain used for inoculation. The amount of OvLV proviral DNA in alveolar macrophages correlated with the degree of LIP. However, differences in the antibody response of genetically identical lambs to OvLV structural proteins indicated that the two strains have different in vivo immunogenic properties. The lack of difference in the degree of LIP between lambs with identical genetic backgrounds suggests that host genetic factors may be important in determining the degree of inflammatory response by the lung.