Epidemic Expansion of HIV Type 1 Subtype C and Recombinant Genotypes in Tanzania

Human immunodeficiency virus type 1 (HIV-1) subtypes are distributed unevenly across African nations.1 In East and Central African countries such as Uganda, Rwanda, Kenya, and Tanzania, the HIV-1 epidemic has involved two HIV-1 subtypes, A and D. In contrast, HIV-1 subtype C has dominated the rapidly expanding epidemic in Malawi and South Africa.1-3 The relative roles played by virological, behavioral, and host determinants in the epidemic expansion of any particular HIV- 1 subtype are unclear. Characterization of the transmissibility and pathogenic potential of distinct HIV-1 genetic subtypes is currently under investigation in many regions of the world. Careful surveillance of genetic subtypes prevalent in a given population is one particularly important approach to better understand the biological properties of different HIV-1 subtypes. The presence of HIV-1 subtypes A and D in asymptomatic carriers and AIDS patients from several geographical locales in Tanzania has been previously described.4-7 An analysis of samples collected in 1988 showed that 10 of 15 (67%) envelope V3 sequences from Tanzanian samples were found to belong to subtype D. The remaining five samples (33%) belonged to HIV-1 subtype A.4 In Dar es Salaam, vpu and env sequences from 8 of 10 AIDS patients (80%) clustered with subtype D viruses and the remaining 2 (20%) with subtype A.5 A study in northern Tanzania reported that the env-encoded gp41 regions from 12 samples also clustered with HIV-1 subtypes A and D.6 In another report from northern Tanzania, four of eight (50%) envelope sequences sampled encompassing the C2V3 region belonged to subtype A and the other half to subtype D.7 Envelope sequences from HIV-1-infected individuals of Tanzanian origin, but living in Sweden, showed that three of four samples were HIV-1 subtype C and the remaining sample was HIV-1 subtype A.