New HIV strain could pose public-health concerns
New HIV strain could pose public-health concerns
Can current blood bank tests detect new viruses?
A new strain of HIV detected in a woman in the central African country of Cameroon does not have immediate public-health consequences, experts say, but it does provide more information about the origins of HIV.1
The new HIV-1 isolate (called "YBF 30" as well as HIV-1, group N) was obtained in 1995 from a 40-year-old Cameroonian woman with AIDS. The isolate appeared to have characteristics of both SIV and HIV-1 group M, but because it is distinct from both SIV and HIV-1, it is considered a new strain.
"This strain is exactly between SIVcpz Gab, which was isolated from a chimp from Gabon seven years ago, and HIV-1 group M," says Francois Simon, MD, a virologist at Laboratoire de Virologie at Bichat-Claude Bernard Hospital in Paris, and lead author of the report on the new virus. (Gabon is a country immediately south of Cameroon.) "Some parts [of the new virus] are closer to the chimp [SIV] in the envelope" of the virus, he says.
Simon says Cameroon has many simian and prosimian primate species, which may have facilitated the spread of the virus to the Cameroonian woman.
"This may have increased the probability of cross-species transmission during casual contact — because there are a high number of [primate] pets — or by hunters," Simon explains. "Many people eat monkeys in central Africa. [Cross-transmission] is clear for HIV-2, which shares the same identity as SIV from mangabey monkeys. This could be true with HIV-1 and SIVcpz, which is not yet identified [in humans]."
Can blood banks detect virus?
The most common strain of HIV worldwide is called group M for major. Group O (for outlier) is far less common and occurs most often in Cameroon. Harold W. Jaffe, MD, associate director for HIV/AIDS in the National Center for Infectious Diseases at the Centers for Disease Control and Prevention in Atlanta, says the main public-health concern regarding the new HIV strain is similar to concerns about group O viruses: Will current tests used in blood-bank screening detect those viruses reliably?
"We have more experience looking at the group O viruses that were first found in Cameroon," he says. "We know that some but not all of the tests that are used to screen blood will detect group O. Manufacturers have been working to modify their tests to allow group O to be detected. It appears that with group N, there may also be a problem with reliable detection."
Simon says the "first evaluation" of the current blood test indicates that it "recognized this strain."
"Of course, further studies are needed on a large group N panel," he adds.
Jaffe says the U.S. Food and Drug Administra tion now requires that any newly licensed tests for blood-bank screening be able to detect group O reliably, even though only two group O infections have been detected in the United States to date. Those two cases occurred in people thought to have been infected in Africa, he adds.
"But on the group N, we just don’t have any information at all," Jaffe says. "It’s probably appropriate to be concerned to the extent of looking at how well our tests detect these variants. I don’t know whether the FDA would require that new tests detect group N."
Viral-load test reliability uncertain
Another unknown factor about the new strain is whether current viral-load tests are reliable for group N. "With group O, they are not reliable, and there have to be specific modifications with these tests to detect group O," Jaffe says.
"That’s less of a public-health question," he adds. "That’s more a question of individual patient management. If it turned out you were taking care of a person infected with one of these [new] strains and you wanted to be able to measure their viral load, you’d have a problem, because current tests don’t do that reliably."
Group O HIV strains appear not to be spreading as far as M strains. "It’s still concentrated largely in Cameroon and adjacent countries," Jaffe says. "It’s not common in other parts of Africa. Where it’s been looked for in Europe, it’s been seen mainly in people originally from Africa. So that strain has not spread rapidly. We don’t know yet about group N."
He adds that for now, at least, the new HIV strain does not appear to pose an immediate public-health threat.
"I think it’s important to separate the more academic issues from the more public-health issues," Jaffe adds. "Academically, I think this is very interesting, because it supports the idea that these viruses are probably originating from nonhuman primates, and that there may have been multiple introductions of these viruses into humans over time. And it may be continuing. In parts of the world where there is ongoing contact between humans and nonhuman primates, this may continue to go on. That’s an important academic concept. For public health, the issues are different, and so far at least, these other subtypes — subtype O and maybe subtype N — have not turned out to be really important public-health issues, but they certainly bear watching."
Reference
1. Simon F, Mauclere P, Roques P, et al. Identification of a new human immunodeficiency virus type 1 distinct from group M and group O. Nat Med 1998; 4:1,032-1,037.
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