Evidence for HIV-1 group O infection in Nigeria [letter]

During 1992-1994 health workers collected 2083 serum samples from pregnant women commercial sex workers and patients with tuberculosis infectious diseases or sexually transmitted disease in Cross River state Nigeria. Virologists tested these samples to determine the HIV-1 group O infection rate. Most HIV-1 group O infections had been limited to Cameroon which borders Cross River state. 183 samples tested positive for HIV. The western blot only identified antibodies to gag and/or pol proteins in 87 samples thereby classifying their results as indeterminate. Virologists used an ELISA based on synthetic peptides derived from the V3 loop of the envelope proteins representing group O viruses (ANT70 and VMP5180) to test all positive samples for HIV-1 group O antibodies. The ELISA identified 12 reactive samples two of which had optical density (OD) value higher than the cut-off ratio of 3.5. The remaining 10 had an OD value around the cut-off. The virologists then applied different biotinylated V3 peptides to a line immunoassay (LIA) as a Streptavidin complex in parallel lines on nylon strips to retest the reactive samples. The 10 weakly reactive samples did not react with the group O V3 peptides in LIA. One of the two more reactive samples reacted with the ANT70 peptide as well as with the consensus and the MAL peptide. The other high OD value-serum reacted on LIA only with the V3 peptides from group O and reacted weakly with the VI686 and MVP5180 V3 peptides. The virologists then retested samples reactive to LIA using a specific western blot for the presence of antibodies to gp120 of HIV-1 ANT70. The sample which reacted with the ANT70 peptide and the consensus and the MAL peptide reacted with the specific HIV-1 ANT70 western blot. The two samples clearly showing HIV-1 group O infection were from Nigerian AIDS patients. These findings show that HIV-1 group O infection has reached Nigeria.