Researchers have reported that for the past few decades a highly virulent variant of HIV-1 has been circulating in the Netherlands.
Viral evolution and HIV-1
The ongoing COVID-19 pandemic has emphasised the risk posed by viruses evolving to greater virulence. For example, the emergence of the Delta variant of SARS-CoV-2 was found to increase transmissibility and probability of death. RNA viruses in particular have caused great concern as their error-prone replication leads to an increased rate of mutation and therefore, increased potential for adaptation. Nonetheless, a greater virulence must not come at a cost for reduced transmission. These antagonistic selection pressures result in an intermediate level of virulence.
The main (M) group of HIV-1 is responsible for the global pandemic. It first emerged in the Republic of Congo in 1920 and diversified into several subtypes by 1960. Differences in virulence between these subtypes has been reported. It is currently understood that the co-receptor for viral entry affects virulence.
HIV-1 virulence is most commonly characterised by viral loads and CD4 counts. These properties are heritable and therefore, are affected by viral genetics. It is expected that these properties could change with the emergence of a new viral variant.
Discovery of a virulent HIV variant
In a recent study, published in Science, researchers reported an exceptionally virulent subtype of HIV that has been circulating in the Netherlands for several years. The team specifically examined data from well-characterised European cohorts.
Within the ongoing BEEHIVE (Bridging the Epidemiology and Evolution of HIV in Europe) project, the researchers identified more than 100 individuals with a distinct strain of subtype-B HIV-1 – the ‘VB variant’. This variant was characterised by high viral loads (~3.5-fold to 5.5-fold increase) and nearly double the rate of CD4 cell decline compared to individuals with other subtype-B HIV strains. By the time these individuals were diagnosed, they were vulnerable to developing AIDS within 2-3 years.
Genetic sequencing analysis suggested that this variant arose in the 1990s from de novo mutation. It also revealed significant changes across the genome affecting almost 300 amino acids. The authors noted that this makes it hard to identify the mechanism for elevated virulence.
Joel Wertheim in an accompanying Perspective commented:
“Observing the emergence of more virulent and transmissible HIV is not a public health crisis.
Let us not forget the overreaction of the claim of ‘Super AIDS’ in 2005, when alarm was raised over a rapidly progressing, multidrug-resistant HIV infection found in New York that was ultimately restricted to a single individual.”
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