PROTECTION OF SIVMAC-INFECTED MACAQUE MONKEYS AGAINST SUPERINFECTION BY A SIMIAN IMMUNODEFICIENCY VIRUS EXPRESSING ENVELOPE GLYCOPROTEINS OF HIV TYPE-1

The infection of macaque monkeys by attenuated simian immunodeficiency virus can vaccinate against pathogenic molecular clones and isolates of the same virus, The correlates of this potent protective immunity a re not fully understood but may be the key to an effective AIDS vaccin e for humans, Aiming to determine whether host immune responses to env elope glycoprotein are an essential component of the immunity to prima te lentiviruses, we have tried to superinfect SIV mac-infected macaque monkeys with SHIVsbg, a chimeric primate lentivirus constructed from the SIVmac239 genome with the env, rev, tat, and vpu genes from HIV-1 Lai. After inoculation of a large dose of SHIVsbg, the chimeric virus was isolated by coculture of mononuclear blood cells from four of five SIV-infected monkeys, but three animals were protected from extracell ular SHIV viremia and did not seroconvert to HIV-1 glycoproteins, In t he two SIV-infected monkeys that did develop SHIV viremia, cell-associ ated viral load was reduced at least 100-fold, These data indicate tha t an antiviral response capable of effectively controlling primate len tivirus replication might not necessarily involve the envelope glycopr otein.