283 Are Broadly Neutralizing Epitopes Exposed Differently on the HIV-1 Envelope Glycoproteins at Different Stages of Infection? L Dacheux*1, Y Ataman2, B Verrier2, F Barin1 1Univ François Rabelais, Tours, France and 2Ecole Normale Supérieure, Lyon, France
Background: According to a commonly held hypothesis, HIV viruses present early in the infection course may mask important neutralizing epitopes of their envelope glycoproteins. In contrast, viruses present at late stages of infection may be better recognized by neutralizing antibodies. The aim of our studies is to evaluate this hypothesis by analyzing the antigenicity of the envelope glycoproteins of primary isolates present during primary infection and several years later in a same patient (pt).
Methods: Blood samples were taken at primary infection and 6 years later from a HIV-1 clade B infected pt. After DNA extraction from PBMCs, the entire env genes were amplified by PCR and then cloned. Using the Semliki Forest Virus eucaryote expression system, recombinant RNA corresponding to the different clones were produced in vitro and transfected into BHK-21 cells. Culture supernatants and cellular lysates containing the envelope glycoproteins were analyzed by ELISA using the 3 broadly neutralizing monoclonal antibodies (MoAbs) IgG1b12, 2G12, and 2F5 and a pool of sera from HIV-1 clade B infected pts as control.
Results: At least 15 env clones were studied to be representative of the major viral quasispecies present at each period. The antigenicity of the envelope glycoproteins at primary infection was highly homogeneous. All the clones (15/15) were not or only poorly bound by neutralizing MoAbs 2G12 and 2F5. In contrast, the antigenicity of the envelope glycoproteins was more heterogeneous in the late sample. Most of the late clones were strongly bound by 2F5 and particularly by 2G12 (9/15). No particular trend was observed with IgG1b12.
Conclusions: We demonstrated that the envelope glycoproteins of HIV-1 quasispecies present during primary infection do not expose (or only weakly) the 2G12 and 2F5 neutralizing epitopes in contrast to those collected 6 yrs later in the same individual. If confirmed in additional pts, this observation would contribute to explain, at least in part, both the viral escape at early stage and the late appearance of broadly neutralizing antibodies.
