Scientists report the discovery of a particularly virulent strain of the human immunodeficiency virus (HIV) in the Netherlands. This particular variant of the virus leads to high viral loads, increased immune cells decline, and higher infectivity. Thanks to the country's excellent HIV care and monitoring program, the variant has been in decline for the last decade.
As reported in Science, and part of the ongoing “Bridging the Epidemiology and Evolution of HIV in Europe” (or BEEHIVE project), researchers identified more than 100 individuals with a distinct strain of the subtype B HIV-1 — the most common subtype of HIV-1 in Europe — which has been called VB.
The VB variant leads to a viral load in the blood between 3.5 and 5.5 times higher than the average HIV infection. It also leads to twice as fast CD4 T cell decline, placing individuals at risk of more rapidly developing AIDS, and higher infectivity, making it more likely to infect other people. Despite its more dangerous characteristics, the researchers say the variant can be managed with current treatments with no problem.
Transmissibility was estimated using phylogenetic methods. In a way, this is a construction of family trees. HIV tends to mutate quickly so each individual has a virus that is unique from everyone else, but the vast majority of these mutations make no difference. Just like members of a family, scientists can group viruses by their genetic code and see how they are related. This allowed them to reconstruct the history of this variant.
“The evolution that resulted in the VB variant took place during the late 1980s and 1990s in the Netherlands. It spread more quickly than other HIV variants during the 2000s, but its spread has been declining since around 2010,” lead author Dr Chris Wymant from the University of Oxford told IFLScience. "This is an example of something that thankfully seems to be rare: viruses or bacteria evolving into a form that's more damaging to our health."
It remains paramount that people are educated (and stigma removed) about HIV and have access to drugs, both preventative such as PrEP (Pre-Exposure Prophylaxis), and treatments like antiretroviral therapy, which is crucial. When people living with HIV are on effective treatment, they can live perfectly healthy lives, and once their viral load becomes undetectable it is impossible for them to pass the virus on. The phrase undetectable equals untransmittable, or U=U, has become a slogan of this great achievement by both scientists and activists.
“if I take actions to avoid getting an infectious disease, to prevent passing it on once I've got it, I've improved the health of people who otherwise would have become ill,” Dr Wymant explained to IFLScience. “However, prevention is also better than cure when we think about evolutionary epidemiology: each infection that we prevent denies the pathogen an opportunity to evolve into something worse. As we quote in our article: “viruses cannot mutate if they cannot replicate” (anonymous), and “the best way to stop it changing is to stop it” (Marc Lipsitch).”
When asked if current therapies are still effective against this more virulent variant, Dr Wymant confirmed that the VB variant “does not have mutations that prevent current treatment from working."
The team notes the study's main limitation is that they did not investigate why VB has a higher virulence, but they anticipate that now that the variant is known other research groups will get involved to understand how it works in detail.
“We hope that experimental study of how this variant attacks immune system cells, and how this differs from normal, could tell us something we don’t know that applies to HIV generally and not just this variant," the authors said in a statement seen by IFLScience. "Better understanding of this process could lead to new ways to stop it or slow it down, i.e. to new treatment.”