Genetic diversity of HIV increasing in Britain due to migration from sub-Saharan Africa

Michael Carter:

Although HIV-1 subtype B remains the dominant strain of HIV in the UK, the investigators found that all the major HIV-1 subtypes are present in the UK, along with recombinant forms of the virus, which are hybrids of more than one subtype. The investigators also found that the genetic make up of 10% of HIV in the UK could not be defined.

Genetic studies have shown that there are three main groups of HIV-1 around the world – M, O, and N – and it is thought that each emerged independently as a consequence of separate transmissions of the virus from chimpanzees to humans.

Outside of western and central Africa, there are nine strains or subtypes of type M HIV-1 (A, B, C, D, F, G, H, J, and K). There are also 16 recombinant forms.

Certain subtypes and recombinant forms have historically been associated with particular geographical regions. For example, subtype B predominates in western Europe and north America. However, travel and migration between regions has contributed to a broader diversity of HIV subtypes in regions of the world.

Investigators wished to see if the genetic diversity of HIV was changing and therefore looked at the genetic structure of 10,500 HIV samples obtained from 1996.

As expected, subtypes B (69%) and C (12%) were the most prevalent forms of HIV in the UK. Nevertheless, six of the seven other subtypes of HIV-1 type M were also detected in the UK. In addition, the recombinant AE (1%) and AG (2%) forms of the virus were seen, as well as other recombinant forms of HIV. Pure subtype K was not found, although recombinant forms including genetic material from subtype K were seen.

In 10% of cases, the genetic diversity of HIV could not be assigned to a particular subtype or recombinant form.

The investigators then looked at trends in the prevalence of subtypes between 1996 and 2004. They found that there was a steady fall in the prevalence of subtype B over this period and an increase in the prevalence of subtype C and unassigned subtypes. This reflected the changing demographics of the UK HIV population due to migration from sub-Saharan Africa.

“Genetic and epidemiological relationships within HIV-1 are becoming increasingly complex” conclude the investigators, particularly in London.

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