Ugandan HIV-1 strains with unusual antigenicity

ABSTRACT

Recent reports have documented that certain HIV-1 antibody tests may not reliably detect divergent variants of HIV-1; provisionally classified as HIV-1 group O. Although most known cases of group O infections are found in Cameroon; the prevalence and worldwide distribution of these unusual variants is unclear. In Uganda; where serveral HIV-1 subtypes have been identified; approaximately 15of confirmed HIV-1-positive specimens tested negative using an in-house peptide enzyme immunoassay (PLEA) based on the immuno-dominant region of gp41 (QQLLGIWGCSGKLICTT) of the prototypic HIV-1 strain LAI. This result prompted us to further investigate these specimens using PEIA's based on the representative V3-loops of each known serotype; including group O (ANT70 and MVP5180) sequences; and other immuno-dominant petides representing the genetic groups M (LAI and ELI) and O (MVP518 and ANT70). No group O infections were found among these samples. This was confirmed by genetic analysis of the C2V3 region of the envelope protein (gp 20) and/or the immuno-dominant region pf the gp41. Ouranalysis showed that a single amino-acid substitution (leuu to His) in position607 of gp41; was associated with the diminished sero-reactivity with the immuno-dominant gp41 peptide baserd on LAI. Since synthetic peptides with similar sequences are being used in many commercial third-generation assays for HIV-1; our findings indicate the need to evaluate the performance of these assays before they are used in Uganda. The results of these evaluations may be useful in developing improved diagnostic assays for HIV-1 in Uganda and other African countries