Genetic diversity needs further examination
More research required before developing vaccine
While continued research into the genetic diversity of HIV-1 in West and West Central Africa is necessary, the implications for a vaccine are clear in a preliminary study, researchers said at the XIII International AIDS Conference in Durban, South Africa.
Martine Peeters, PhD, of the Institute for Research and Development in Montpellier, France, says that research conducted in eight countries identified and characterized more than 1,500 HIV-1 viruses in West and West Central Africa and found that the predominant subtype is A.
Peeters presented a paper on behalf of five other members of the research team during the conference. For the purposes of the research, data were collected between 1997 and 1999 in Senegal, Mali, Niger, Nigeria, Chad, Cameroon, Gabon, and the Democratic Republic of the Congo.
Different subtypes occurring across Africa
Peeters said that the A subtype decreased in prevalence from the West, where it was found in about 85% of the cases studied, to less than 50% in West Central Africa. Subtype G was recorded in all the countries and represented more than 25% of the viruses in Nigeria. A higher diversity was found in countries situated in West Central Africa, such as the Democratic Republic of the Congo. In those countries, there were more subtypes, more recombinants, and a higher diversity within subtype A.
The majority of known HIV-1 subtypes and circulating recombinant forms were present in all the countries studied, but their prevalence varied, Peeters said. In addition, there were differences in the subtype of HIV-1 prevalent within the countries studied. For example, in Zaire, he said, one subtype was most prevalent in the North, while another was more prominent in the South.
Genetic subtype distribution is a dynamic process, a factor that is important for vaccine strategies, he emphasized. However, further analysis of the results is needed and other recent information must be analyzed when considering a vaccine.
In other research, a study of HIV-1 subtype C viruses has culminated in the selection, based on genotypic and phenotypic properties, for inclusion into HIV-1 candidate vaccine.
It is anticipated that the first phase of trials will start next year, said Carolyn Williamson, MD, of the department of medical microbiology at the University of Cape Town in South Africa.
Samples of HIV-1 subtype C, which is prevalent in about 90% of the HIV infections in Southern Africa, were collected from commercial sex workers in the KwaZulu-Natal province. The sex workers saw an average of about four clients a day, and most did not use condoms. They had seroconverted at least one year before the samples were collected.
Williamson said the phylogenetic analysis classified all 31 isolates as subtype C based on gag, pol, and env genes.
"Two isolates were selected for inclusion into vaccines based on phylogenetic analysis, amino acid similarity to the consensus sequence, R5 phenotype, and adequate replication capacity in tissue culture," she explained.
Research into HIV-1 diversity in South America has found that subtype B continues to be the most prevalent genotype of HIV-1 in most of the eight countries surveyed. However, a surprisingly high prevalence of subtype F was detected, said Kevin Russell, MD, head of the department of virology of the United States Navy Medical Research Center Detachment in Lima, Peru.
Virus starting to take hold of South America
Russell was the presenting author of a paper on research conducted by 12 individuals from Peru, Uruguay, Paraguay, Argentina, Ecuador, Bolivia, and the United States. The study was conducted in collaboration with the Pan American Health Organization, respective health departments in the various countries participating in the research, and nongovernmental organizations that could play a role.
Russell said the Navy Medical Research Center Detachment has been involved in HIV surveillance in South American countries since the early 1990s, but it dramatically increased its scope in 1998, when new aspects and attitudes relating to AIDS were detected.
Poverty and the lack of empowerment of women were important factors in this area, Russell noted, where an estimated 150,000 new infections occurred last year. "Now is the time for intervention and education to have an impact," he says.
Russell added that knowledge of circulating genotypes of HIV-1 is becoming increasingly important as vaccine trials become a reality.
From eight at-risk populations in five countries, the prevalence of HIV ranged from 0.3% to 21%. Genotype B was found to be predominant in five of the six countries from which 825 samples were collected for genotyping. Of the total samples processed, 77% were genotype B, 23% genotype F, and there was only one instance each of genotypes C and A.
One exception to the prevalence of subtype B, Russell says, was in Argentina. In that country, researchers found that the majority of maternity patients who were HIV positive were genotype F. A similar discrepancy was obtained in the data from Uruguay, where nearly half of the infections identified were genotype F.
Subtypes rapidly expanding in France
Russell said continued surveillance of HIV in South America is clearly warranted. "The epidemic in South America is in its early stages. Now is the time to target groups to ensure early intervention."
In France, the population infected by the subtype B has remained phylogenetically stable, but a fast introduction of new subtypes has been experienced. A 16% prevalence of non-B subtypes was recorded in 295 patients, but those were mainly from Africa or were people who had African partners.
Those were the findings of a study presented by Pierre Roques of the Centre for Experimental Atomique in France. The research was conducted by a team of eight and involved the testing of 2,168 HIV-1 positive patients.
In a subgroup, the year when HIV infection occurred was estimated. From that group of 552 HIV-1 positive patients, 483 were infected with subtype B, and 69 with a non-B subtype.
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