The p15^gag and p12^gag regions are both necessary for the pathogenicity of the murine AIDS virus

The defective marine AIDS (MAIDS) virus has unique sequences in its p15^gag and p12^gag regions. To clarify whether these sequences are responsible for the development of MAIDS, we constructed recombinant viruses by replacing various regions of the gag gene of the nonpathogenic replication-competent LP-BM5 ecotropic virus with those of the MAIDS virus. Recombinants containing both unique sequences of the MAIDS virus were replication defective and induced MAIDS. However, a recombinant containing either the p15^gag or p12^gag region of the MAIDS virus was also replication defective but nonpathogenic in mice. A recombinant virus containing only the p30^gag region of the MAIDS virus was replication competent and nonpathogenic. These results indicate that the p15^gag and p12^gag regions of the MAIDS virus do not function like those of replication-competent viruses and that both of the unique sequences in the p15^gag and p12^gag regions are required to develop MAIDS.