Serum reactivity to HIV-1 accessory gene products distinguishes East African from West African HIV strains as infecting agent.

The existence of dual infections with human immunodeficiency virus (HIV)-1 and 2 in West African countries has been controversial, although the current consensus is that dual infection is not the cause of the extensive cross-reactivity observed between these 2 viruses. To evaluate the role of antibody reactivity to the HIV-1 accessory gene products in type-specific HIV serology, proteins encoded for nef, tat, rev, vpr, and vpu were developed and used as an antigen. 5 of the 7 exclusively HIV-2 reactive sera were not reactive to the HIV-1 accessory gene products. Moreover, the 2 sera that showed reactivity to the HIV-1 envelope were the only ones reactive to HIV-1 accessory gene products. These findings indicate that type 2 viruses may be as diverse as type 1 viruses. A subsequent analysis of sera from 24 West Africans revealed reactivity with a simian immunodeficiency virus (SIV) peptide but not with an HIV-1 peptide previously shown to be discriminatory in a direct binding assay between HIV-1 and HIV-2. Compared to 29 control sera from East Africans, the West Africa sera had significantly lower reactivity to antibodies specific to nef, tat, and rev; there was not reactivity to vpr and vpu. 38% of the West African sera compared with 93% of the East African sera showed reactivity to HIV-1 accessory gene products. It is concluded that, while reactivity to the HIV-1 accessory gene products vpr and vpu indicate HIV-1 infection, reactivity to the other accessory gene products cannot be used to identify virus type given the documented cross-reactivity to HIV-1 accessory gene products of antibodies elicited by HIV-2 strains.