Neutralization Susceptibility of B Subtype Variant B' Primary HIV-1 Isolates

Susceptibility to autologous and heterologous neutralization of primary human immunodeficiency virus (HIV)-1 isolates belonging to subtype B, to the B'-variant of subtype B or to subtype F from infected individuals residing in Rio de Janeiro was assayed. A lower infectivity of the B'- and F isolates when compared to the classical B-subtype HIV-1 isolates was observed. Comparisons of neutralization susceptibilities were carried out for 19 B-subtype, 11 B'-variant and two F-subtype HIV-1 isolates with plasma from autologous and heterologous samples. Frequency of autologous neutralization was slightly lower for B-subtype isolates in comparison to B'-variant isolates. Heterologous intra-subtype neutralization was significantly lower for B-subtype than for the B'-variant or the F-subtype isolates. While B-subtype isolates were neutralized by most anti-F-subtype plasma, F-subtype isolates, although most susceptible to F-subtype antibodies, were highly susceptible to neutralization by anti-B-subtype antibodies. Cross-neutralization for B'-variant and B-subtype isolates was not as extensive as observed for B- and F-subtype isolates. However, the results presented indicate a quite extensive cross-neutralization between Brazilian HIV-1 isolates.