FAILURE OF SIVMAC TO BE NEUTRALIZED IN MACROPHAGE CULTURES IS UNIQUE TO SIVMAC AND NOT OBSERVED WITH NEUTRALIZATION OF SHIV OR HIV-1

Except during acutely lethal infection, macaques infected with SIV(mac )251 produce antibodies that neutralize the virus in CEMx174 cells, ma caque PBMC and macrophage cultures. In a previous report, we had shown that whereas neutralization of the SIV(mac)251 was complete in lympho cyte cultures, ''protected'' macrophages had actually become latently infected, and remained viral DNA-positive, but the infection was nonpr oductive as long as antibodies were maintained in the medium. Removal of the antibodies as long as 1 week later, resulted in resurgence of v irus replication. In the present study, we compared neutralization of SIV(mac)239 with that of neutralization of SHIV and HIV-1, and sought to determine whether the failure to prevent infection in macrophages w as also typical of neutralization of SHIV and HIV-1 in macaque and hum an macrophage cultures, respectively. The results showed that similar to SIV(mac)251, neutralizing antibodies did not block SIV(mac)239 infe ction in macaque macrophages, although they blocked infection of the v irus in T cells. The data from neutralization of SHIV using anti-SHIV antibodies and for neutralization of HIV-1 (89.6 and Bal) using anti-H IV IgG in both T cells and macrophages, however, can be summarized wit h a single statement: neutralization of SHIV and HIV-1 was complete in all of the cultures, with no evidence of establishment of latent infe ction in or resurgence of virus replication after antibodies were remo ved from macrophage cultures. The non-neutralizability of SIVmac (251 and 239) in macrophages is therefore unique to the SIVmac and not rele vant to neutralization of HIV-1.