Evidence of serological cross-reactivities with human immunodeficiency virus types 1 and 2 and human T-lymphotropic virus types I and II in sera of pregnant women in Ibadan, Nigeria.

BACKGROUND: Our previous studies have indicated that the human immunodeficiency virus (HIV) and human T-lymphotropic virus (HTLV) groups of retroviruses are endemic among various populations in Nigeria. These viruses are antigenically distinct and antibodies to HIV and HTLV do not cross-react, so we studied the prevalence of HIV-1, HIV-2, HTLV-I and HTLV-II antibodies in sera of pregnant women attending an antenatal clinic in Ibadan, Nigeria.

METHODS: In all, 364 sera were screened using three different enzyme immunoassays, including those that distinguished HIV-1 antibodies from HIV-2, and HTLV-I antibodies from HTLV-II. All repeatedly reactive sera were confirmed by Western blots and synthetic peptide assays for the respective viruses.

RESULTS: Overall, 71 sera (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 antibodies 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 antibodies 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 reactivities 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 associated with co-infections with two or more retroviruses.