EVIDENCE OF SEROLOGICAL CROSS-REACTIVITIES WITH HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 AND TYPE-2 AND HUMAN T-LYMPHOTROPIC VIRUS TYPE-I AND TYPE-II IN SERA OF PREGNANT-WOMEN IN IBADAN, NIGERIA

Background. Our previous studies have indicated that the human immunod eficiency virus (HIV) and human T-lymphotropic virus (HTLV) groups of retroviruses are endemic among various populations in Nigeria. These v iruses are antigenically distinct and antibodies to HIV and HTLV do no t cross-react, so we studied the prevalence of HIV-1, HIV-2, HTLV-I an d HTLV-II antibodies in sera of pregnant women attending an antenatal clinic in Ibadan, Nigeria. Methods. In all, 364 sera were screened usi ng three different enzyme immunoassays, including those that distingui shed HIV-1 antibodies from HIV-2, and HTLV-I antibodies from HTLV-II. All repeatedly reactive sera were confirmed by Western blots and synth etic peptide assays for the respective viruses. Results. Overall, 71 s era (19.5%) had antibodies to HIV, HTLV or both groups of retroviruses . Most (95.8%) of the reactive samples were from women 20-29 years old , Two of five sera from individuals <20 years old reacted for HIV anti bodies while one serum from a 40 year old woman was reactive for HTLV- I antibodies. Of the 71 reactive sera, 29 (8%) had antibodies to HIV ( HIV-1 = 14, HIV-2 = 9, HIV-1/2 = 6) and 42 samples (11.5%) showed anti bodies to HTLV (HTLV-I = 20, HTLV-II = 14, HTLV-I/II = 8). Seven of 71 seropositive samples (9.8%) reacted for both HIV and HTLV antibodies in various combinations, including one serum that showed antibody reac tivities to all four retroviruses (i.e. HIV-1, HIV-2, HTLV-I and HTLV- II). Conclusions. The high prevalence of antibodies to subtypes of the two entirely distinct retrovirus groups in young women has important implications for defining epidemiological patterns of diseases associa ted with co-infections with two or more retroviruses.