482 The Two Predominant HIV-1 Variants in Africa, CRF02-AG and Subtype C, Have Different Biological Characteristics Anke Bourgeois1, Eitel Mpoudi2, Florian Liegeois2, Rose Mognoutou2, Christian Laurent1, Eric Delaporte*1, Martine Peeters1 1UR36, IRD and Univ of Montpellier, France and 2Projet Prevention du Sida au Cameroun, Yaounde, Cameroon
Background: Classification of virus isolates as syncytium-inducing (SI) or non-SI (NSI) is considered to be important for the prognosis of disease progression. The appearance of SI variants is related to enhanced CD4 cell depletion and disease progression to AIDS in subtype B infections. Few data exist on the biological characteristics of CRF02-AG strains which are predominant in the HIV epidemic from West and West Central Africa.
Methods: The SI capacity was studied on MT-2 cells for 108 HIV-1 positive patients (pts) infected with a CRF02-AG strain in Cameroon, West Central Africa. All patients attended PRESICA, a health structure providing counseling, voluntary testing and medical care for HIV infected pts in Yaounde , the capital city, between 1996 and 2001.The data were correlated to the disease stage of the pts as reflected by their CD4 counts.
Results: Similarly as observed in subtype B infected pts, more SI strains are observed in pts at a more advanced disease stage: 55.81% SI strains in pts with less than 200 CD4 cells/mm3, 19.56% SI strains when CD4 counts are between 200 and 500 cells/mm3, and 21.42% SI strains when CD4s are above 500 cells/mm3. In the same manner as was done for subtype B strains, we studied the prediction of the phenotype based on the sequence of the V3 loop, e.g., we examined whether positively charged amino-acids at positions 11 and/or 25 in the V3 loop were present, and calculated the global charge of the V3-loop. Based on amino-acids at positions 11 and 25, 67 (96,53%) of the NSI strains were predicted NSI and only 12 (33.3%) of SI strains were predicted SI. The global charge of the V3 loop was significantly lower for NSI strains, 4.16 (±0.91) for NSI versus 5.42 (±1.36) for SI strains (p < 10-4).
Conclusions: The SI capacity and MT-2 cell tropism of the CRF02-AG strains are similar as those seen in subtype B infected pts in Europe and the U.S. It is however important to note that the 2 predominant HIV-1 variants in Africa, CRF02-AG and subtype C, have different biological characteristics because multiple reports showed that CXCR4 usage as well as SI capacity or MT-2 cell tropism was rare among subtype C samples.