Open Access Open Badges Research

Frequency of subtype B and F1 dual infection in HIV-1 positive, Brazilian men who have sex with men

Ana Carolina Soares de Oliveira12, Rodrigo Pessôa de Farias2, Antonio Charlys da Costa12, Mariana Melillo Sauer3, Katia Cristina Bassichetto4, Solange Maria Santos Oliveira4, Priscilla Ramos Costa3, Claudia Tomiyama3, Helena Tomoko Iwashita Tomiyama3, Ester Cerdeira Sabino5, Esper Georges Kallas3 and Sabri Saeed Sanabani67*

Author Affiliations

1 Department of Translational Medicine, Federal University of São Paulo, São Paulo, Brazil

2 São Paulo Institute of Tropical Medicine, University of São Paulo, São Paulo, Brazil

3 Division of Clinical Immunology and Allergy, School of Medicine, University of São Paulo, São Paulo, Brazil

4 Public Health Department of São Paulo, São Paulo, Brazil

5 Department of Infectious Diseases, School of Medicine, University of São Paulo, São Paulo, Brazil

6 Clinical Laboratory, Department of Pathology, LIM 03, Hospital das Clínicas (HC), School of Medicine, University of São Paulo, São Paulo, Brazil

7 Faculdade de Medicina, Instituto de Medicina Tropical de São Paulo, Universidade de São Paulo, LIM 52 - Av. Dr. Enéas Carvalho de Aguiar, 470 - 2 andar - Cerqueira Cesar, 05403-000, Sao Paulo, SP, Brasil

For all author emails, please log on.

Virology Journal 2012, 9:223  doi:10.1186/1743-422X-9-223

Published: 29 September 2012



Because various HIV vaccination studies are in progress, it is important to understand how often inter- and intra-subtype co/superinfection occurs in different HIV-infected high-risk groups. This knowledge would aid in the development of future prevention programs. In this cross-sectional study, we report the frequency of subtype B and F1 co-infection in a clinical group of 41 recently HIV-1 infected men who have sex with men (MSM) in São Paulo, Brazil.


Proviral HIV-1 DNA was isolated from subject's peripheral blood polymorphonuclear leukocytes that were obtained at the time of enrollment. Each subject was known to be infected with a subtype B virus as determined in a previous study. A small fragment of the integrase gene (nucleotide 4255–4478 of HXB2) was amplified by nested polymerase chain reaction (PCR) using subclade F1 specific primers. The PCR results were further confirmed by phylogenetic analysis. Viral load (VL) data were extrapolated from the medical records of each patient.


For the 41 samples from MSM who were recently infected with subtype B virus, it was possible to detect subclade F1 proviral DNA in five patients, which represents a co-infection rate of 12.2%. In subjects with dual infection, the median VL was 5.3 × 104 copies/ML, whereas in MSM that were infected with only subtype B virus the median VL was 3.8 × 104 copies/ML (p > 0.8).


This study indicated that subtype B and F1 co-infection occurs frequently within the HIV-positive MSM population as suggested by large number of BF1 recombinant viruses reported in Brazil. This finding will help us track the epidemic and provide support for the development of immunization strategies against the HIV.