HIV This Week

Sarker MS, Rahman M, Yirrell D, Campbell E, Rahman AS, Islam LN, Azim T. Molecular evidence for polyphyletic origin of human immunodeficiency virus type 1 subtype C in Bangladesh. Virus Res. 2008;135(1):89-94

HIV-1 positive blood samples were collected between 1999 and 2005 from population groups most at risk of HIV infection in Bangladesh through the national surveillance, from clients of the Voluntary Counselling and Testing (VCT) Unit for HIV at the International Centre for Diarrhoeal Diseases Research, Bangladesh, and a from survey of HIV in patients with tuberculosis. Partial sequences of the gag gene were used for subtyping the HIV strains by nested polymerase chain reaction using selective primers. Of the 198 HIV strains tested, subtype C (41.4%) was the commonest strain identified. Phylogenetic analysis of Bangladeshi subtype C strains showed that they clustered in polyphyletic branches representing HIV strains from different parts of the world. Most of the strains from injecting drug users clustered together and were similar to Indian strains. The VCT strains however were very heterogeneous and clustered with strains from India, Myanmar, Ethiopia and Zimbabwe. Data suggest that there have been few introductions into the injecting drug user population where the epidemic is driven by indigenous transmission. On the other hand there have been many and regular introductions of subtype C viruses through migrant workers in the VCT group. Very little overlap was observed in the strains obtained from injecting drug users and those from other population groups.

Editors´note: Injecting drug use transmission of subtype C virus in Bangladesh appears to be confined primarily to the community of people who inject drugs, with the strains being very similar. The majority of strains from the VCT clients were not subtype C and those that were subtype C were a very heterogeneous population, suggesting transmission from a variety of different geographical sources. None of the strains from the VCT clients clustered with isolates from the injecting drug users, suggesting little interaction between these two populations that could lead to HIV transmission. Studying HIV subtypes can provide a window on the dynamics of a country’s epidemic.