The MN strain of HIV-1 is known to be more prevalent in Brazil, the BRU strain is more prevalent in Europe, and the NDK strain in Africa. It has been suggested in the literature to include different strains in the same vaccine against HIV-1. To contribute to the studies for the development of a universal vaccine, the occurrence of antibodies (Ab) against three HIV-1 strains (MN, BRU and NDK) was determined in serum samples from 85 HIV-1-positive patients, adult volunteers seen at the University Hospital of the Faculty of Medicine of Ribeirão Preto-USP. One-hundred tissue culture infective unit (TCIU) of the viruses reacted with serial dilutions of the sera (2x) and with MT4 cells added at a final concentration of 0.3 × 106 cells/ml, and a cytopathic effect was observed on the 7th and 11th days of incubation. Titres of less than 1/50 were considered to be negative. In 129 tests, the sera were negative for one of the three strains: 40 for MN, 29 for BRU and 60 for NDK. There was a predominance of strains MN and BRU, most of them presenting titres from 1/50 to 1/200. Titres for NDK were detected in 25 sera. We conclude that there seems to be a predominance of strains MN and BRU among the individuals from the region tested; however, the detection of sera with positive NKD titres indicates the need for further studies of this strain in other populations and regions of Brazil
AIDS; HIV-1 MN; HIV-1 BRU; HIV-1 NDK; Neutralizing antibodies
