Correlation between anti-V3 peptide and neutralizing antibodies in plasma from HIV-1 infected individuals resident in Brazil

A study was conducted of the reactivity of 85 plasma samples from HIV-1 seropositive persons living in Brazil. Five HIV-1 plasma samples had synthetic peptides from the V3 region isolates (IIIB MN SC WMJ-2 and RF). There was a low reactivity (59%) with HIV-1 isolate MN derived PND peptides while most studies report a 90% or higher reactivity. Brazilian HIV-1 seropositive sera had lower reactivity with MN isolate PND peptides than sera from other countries. Researchers used 5 HIV-1 MN isolate PND peptides from other sources to analyze the same plasma to confirm the studys results. The HIV-1 MN isolate PND peptides had different amino acid sequences but all had the GPGR top of the V3 loop. 52% of the Brazilian plasma recognized V3 peptides 55% for 48 peptides 56% for C52 peptides and 49% for C53 pep tides. Only 27% of the Brazilian plasma recognized the C54 peptide. There was considerable overlapping reactivity however. For example 65% of the V3 MN reactive plasma also recognized the C52 MN peptide and the C53 MN peptide. The overlap between C52 MN and C53 MN was 69%. These findings suggest that in the Brazilian study population at least 2 different anti-MN-PND antibody specificities directed against amino acid sequences including the GPGR top of the V3 loop exist (an epitope including PNY[NKRKRIHIGPGR] and the epitope including [KRKRIHIGPGR]AFY). 86% of the plasma reacted with at least 20% of the MN PND peptides which equals reactivities in other studies. 96% of the Brazilian plasma were positive for neutralizing antibodies based on overlap of peptide recognition and HIV-1 MN isolate neutralization (titers = 1:100-1:52600). Recognition of the V3 loop of the HIV-1 MN isolate in sera from HIV-1 positive persons in Brazil has two different antibody specificities. Most of the Brazilian plasma recognize the N terminal arm which consists of the GPGR top of the V3 loop.