Objective: To determine to what extent HIV-1 group O strains are present in different African countries.
Materials and methods: A total of 14,682 samples of sera from a range of patients from 12 different African countries were tested. All the sera were tested with an enzyme-linked immunosorbent assay (ELISA) using a combination of V3 peptides from ANT-70 and MVP-5180. Samples reactive in ELISA were retested in a line immunoassay (LIA-O). Samples reactive in ELISA were also retested with an in-house Western blot to determine the presence of antibodies to gp120 of HIV-1 ANT-70. Polymerase chain reaction was performed on HIV-1 group O and group O indeterminate sera.
Results: Of all the sera samples tested, only 19 sera had antibodies to group O V3 peptides exclusively and 46 were indeterminate for group O infection in LIA-O. The highest prevalence of HIV-1 group O infection among HIV-positive sera was observed in Cameroon (2.1%) and neighbouring countries, 1.1% in Nigeria and 0.9% in Gabon. The lowest rates were seen in west Africa: 0.07% in Senegal, 0.14% in Togo, 0.16% in Chad and 0.3% in Niger. Group O sera were observed in almost all the population categories tested. The ANT-70 V3 peptide in LIA-O was reactive with all of the sera considered to be HIV-1 group O antibody positive by LIA, versus 78.9% for the MVP-5180 peptide. Thirteen out of 19 group O samples of sera were tested in PCR. Eight samples were identified as group O by specific group O pol and/or V3 primers; in the remaining five samples no HIV RNA could be detected. Of the indeterminate sera samples, two were identified as group O.
Conclusion: In eight of the 12 countries tested, antibodies to group O viruses were identified. Numbers of HIV-1 group O viruses are low. Their presence is not restricted to Cameroon and neighbouring countries but can also be found in west and south-east Africa.
PIP: An enzyme-linked immunosorbent assay (ELISA), using a combination of V3 peptides and ANT-70 and MVP-5180, was used to test 14,682 sera samples from people living in Burkina Faso, Burundi, Cameroon, Chad, Congo, Gabon, Mali, Niger, Nigeria, Senegal, Togo, and Zambia to examine the geographic spread of HIV-1 group O viruses in Africa. An in-house Western blot and a line immunoassay (LIA-O) were used to detect the presence of antibodies to gp120 of HIV-1 ANT-70 of samples reactive in ELISA and then a polymerase chain reaction (PCR) on HIV-1 group O and group O indeterminant sera. HIV-1 group O antibodies were present in 8 countries (Cameroon, Chad, Gabon, Niger, Nigeria, Senegal, Togo, and Zambia). Among these 8 countries, the prevalence of HIV-1 group O sera ranged from 2.1% in Cameroon to 0.07% in Senegal. Cameroon and its neighboring countries had a higher prevalence than the West African countries (0.9-2.1% vs. 0.07-0.3%) and Zambia. HIV-1 group O virus was more or less evenly distributed among the population groups tested. The ANT-70 V3 peptide in LIA-O had a higher reactivity rate with HIV-1 group O sera than MVP-5180 V3 peptide in LIA-O (100% vs. 78.9%). 8 of the 13 samples tested in PCR were identified as group O by specific group O pol and/or V3 primers. Among the remaining 5 indeterminant sera samples, 2 were identified as group O. Prospective studies are needed to monitor the true prevalence of HIV-1 group O viruses in Cameroon, its neighboring countries, and West Africa. They are also needed to determine the risk factors associated with group O infection. Monitoring these viruses will allow adaptation of HIV testing strategies for blood screening and serodiagnosis if required.