New subtype of HIV found, but don't panic

Scientists who announced the discovery of a new subtype of HIV earlier this month are telling people not to worry: The discovery, they say, is a good thing and shows that the technology used to make it will improve surveillance of the (admittedly, mutating) virus, but it doesn't mean that HIV will suddenly become untreatable.

The study, conducted by Abbott Laboratories and the University of Missouri, Kansas City, was published in the Journal of Acquired Immune Deficiency Syndromes. Researchers dubbed the new strain HIV-1 subtype L. It's in the same family of virus subtypes that exist in the global HIV pandemic, but the first new subtype of the virus to be identified since the development of guidelines for classifying subtypes in 2000.

You can think of HIV (and other viruses) as a tree. Consider HIV-1 and HIV-2 as major branches, groups as even smaller branches, and the subtypes as the smallest branches. The new subtype L comes from group M (a big branch), which is responsible for more than 90% of HIV infections worldwide. HIV-1 has three other groups, or main branches: N, O, and P. (Also, it's not technically correct to use subtype and strain interchangeably. A subtype is a subset of a strain -- a smaller branch, so to speak -- so for the case of the team's discovery, we'll continue to use subtype.)

Researchers say it's important to know what subtypes (and strains) of a virus are circulating in the world to make sure that tests used to detect the disease are effective. And here's where the "don't panic" part comes in: Finding a new subtype (small branch) doesn't mean that current meds will be rendered ineffective for it, according to Carole McArthur, Ph.D., M.D., professor in the Department of Oral and Craniofacial Sciences at the University of Missouri at Kansas City, and one of the study authors.

"HIV replicates fast and diverges a lot, and you have to be monitoring it constantly," McArthur told TheBody. "But this sequence is closely related to strains we've already seen, close enough that current drugs will be effective against it."

In determining whether a virus is in fact a new HIV subtype, three cases must be discovered independently. The first two samples of this subtype, L, had been discovered in Democratic Republic of the Congo (DRC) in the 1980s and the 1990s. McArthur's sample, which she collected in 2001 in the DRC and stored in a freezer, was too small for existing technology to sequence it.

But technology recently caught up. Next-generation sequencing, and an even newer process called xGen, allowed researchers to isolate HIV from the "clutter" in the sample. Next-generation sequencing technology allows researchers to build an entire genome at higher speeds and lower costs. Consider that the human genome project took 20 years and $10 million to complete. The new process can achieve the same results in one day for about a thousand dollars, researchers said.

"We actually used a magnet to pull out the subtype," said Mary Rodgers, Ph.D., head of the Abbott Laboratories' Global Viral Surveillance Program and one of the study authors.

McArthur and Rodgers said that because the technology was so effective here, more subtype discoveries could be made from tiny samples that have been collected for years. What the discovery also tells them is that subtype L is so closely related to other "branches" of Group M that it presents no risk for current treatment regimens.

Jeffrey Kirchner, D.O., AAHIVS, chief medical officer at the American Academy of HIV Medicine, agrees that there's no need for panic about the discovery. "It's clearly of scientific interest but without clinical implications. It freaks people out who think there's a mutating virus out there. It is encouraging to know people are continuing to do genetic analysis of HIV strains."

But when might there be a reason to freak out about a new strain? Kirchner said a cross-species transference leading to, theoretically, HIV-3 -- a new, really big branch -- would be cause for concern. "There is the theoretical risk of this, and if it were discovered, we would have to reassess the current antiviral drug regimen, which is effective against types one and two."

Kirchner said multiple subtypes do have implications for vaccine trials, however. If a virus shows variability, as both HIV-1 and HIV-2 do, finding a vaccine against all subtypes is challenging. "For example, would a vaccine that works in Kenya work in England? Maybe not."

But as for current clinical implications, Rodgers underscores the theme of don't panic, and she emphasizes that discoveries like subtype L, and others still to be discovered, can help prevent future pandemics. "We're not waiting around for new virus mutations to stump up. We're going to keep looking for tiny changes (to viruses). I hope that actually makes people feel safer."

Source:
TheBody
Tags:
HIV-1 subtype L, HIV subtypes