CROI: Haiti is the source of HIV subtype B

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Haiti has the oldest HIV epidemic outside Africa and provided the source for the strain of HIV seen in North America and Europe, according to viral research presented to the Fourteenth Conference on Retroviruses and Opportunistic Infections in Los Angeles.

An international team of researchers found that the type of HIV most prevalent in Haiti, the United States and Europe – HIV-1 group M, subtype B – moved from Africa to Haiti in around 1966. HIV spread around Haiti before a single migration of the virus took it out of Haiti to the US and then worldwide between 1969 and 1972. The research also suggests that HIV-1 group M originated comparatively recently, probably no earlier than the early 20th century.

The exact circumstances surrounding the emergence of the strain of HIV in the United States and Europe have long been the subject of debate. Investigators from the US, Denmark and the United Kingdom recovered complete HIV-1 env gene sequences from samples obtained from five Haitian AIDS patients between 1982 and 1983 who were recent migrants to the United States. To test the hypothesis that subtype B has a Haitian origin, they conducted phylogenetic analysis of samples obtained from these patients and on a further 117 samples obtained from patients in 19 different countries.

Glossary

subtype

In HIV, different strains which can be grouped according to their genes. HIV-1 is classified into three ‘groups,’ M, N, and O. Most HIV-1 is in group M which is further divided into subtypes, A, B, C and D etc. Subtype B is most common in Europe and North America, whilst A, C and D are most important worldwide.

strain

A variant characterised by a specific genotype.

 

hypothesis

A tentative explanation for an observation, phenomenon, or scientific problem. The purpose of a research study is to test whether the hypothesis is true or not.

opportunistic infection (OI)

An infection that occurs more frequently or is more severe in people with weakened immune systems, such as people with low CD4 counts, than in people with healthy immune systems. Opportunistic infections common in people with advanced HIV disease include Pneumocystis jiroveci pneumonia; Kaposi sarcoma; cryptosporidiosis; histoplasmosis; other parasitic, viral, and fungal infections; and some types of cancer. 

gene

A unit of heredity, that determines a specific feature of the shape of a living organism. This genetic element is a sequence of DNA (or RNA, for viruses), located in a very specific place (locus) of a chromosome.

A US or non-Haitian origin for subtype B was rejected by this analysis, strongly in favour of a Haitian origin.

This was confirmed by analysis of the gag sequence of the viral samples.

According to the investigators’ analysis, HIV-1 moved from Africa to Haiti in the mid-1960s – probably in or around 1966, a time when many Haitians professionals were returning home after working in the Congo.

Between 1969 and 1972, a single migration took subtype B out of Haiti. The investigators called this migration the “pandemic clade”, representing “a key turning point in the history of the AIDS pandemic”. HIV was transferred to the US by a single source in the early in the 1970s. This fits with subsequent epidemiology of HIV in the US. The first cases of AIDS were reported approximately ten years after HIV entered the US from Haiti - the interval between infection with HIV and progression to AIDS and death is in the region of ten years.

Interestingly, a single Haitian source was also identified for the subtype B epidemic in Trinidad and Tobago.

Haiti’s has had a long association with the origins of the AIDS epidemic. It was sometimes said – often disparagingly – that AIDS affected the three “H”’s – Haitians, homosexuals and haemophiliacs.

“Rare, single transmission events” provided the hinge for “major outbreaks” of HIV, the investigators conclude.

They also believe that their results suggest that the ancestor for M-group HIV did not emerge until the early 20th century, probably around 1930.

Dr Michael Worobey’s presentation was greeted with an angry response by a Haitian delegate to the conference, who pointed to earlier studies that failed to find evidence of HIV infection in stored samples in the country. In response, Dr Worobey stressed that his study was not intended to “blame” any country or individuals for the origin of the HIV epidemic, but he again emphasised that that phylogentic analysis clearly showed a Haitian origin for the subtype B epidemic.

References

Worobey M et al. Exodus and genesis: the emergence of HIV-1 group M subtype B. Fourteenth Conference on Retroviruses and Opportunistic Infections, abstract 149, Los Angeles, 2007.