Viruses, including the Human Immunodeficiency Virus (HIV), naturally mutate over time, leading to new variants. This process can result in versions of a virus that differ from the original strain. Researchers have identified a specific variant of HIV that is more damaging to the immune system.
Identifying the Virulent HIV Variant
A more virulent version of HIV, named the virulent subtype-B (VB) variant, was identified by the BEEHIVE project, a research initiative analyzing HIV samples from Europe and Uganda. The project first found 17 individuals with this variant, 15 from the Netherlands. This prompted a deeper investigation into a Dutch cohort of over 6,700 people living with HIV, which uncovered an additional 92 cases.
Genetic analysis estimates that the VB variant has been in circulation since the late 1980s or early 1990s. It appears to have spread more quickly than other HIV variants during the 2000s, with its transmission rate declining since around 2010. This discovery is the recognition of a pre-existing, more potent form of the virus that had previously gone unnoticed.
The VB variant is characterized by numerous mutations across its genome, making it difficult to pinpoint a single genetic cause for its increased virulence. The individuals found to have this variant displayed typical characteristics for people with HIV in the Netherlands regarding age, sex, and suspected mode of transmission. This suggests that the variant’s characteristics are due to properties of the virus itself.
Understanding Increased Virulence
The term “highly virulent” in this context refers to two specific biological markers. The first is a significantly higher viral load, which is the amount of virus present in the blood. Individuals with the VB variant before treatment have viral loads that are between 3.5 and 5.5 times higher than people with other HIV variants.
The second distinguishing feature is a much faster deterioration of the immune system. This is measured by the decline in CD4 T-cells, which are a type of white blood cell that plays a central role in immune function. In individuals with the VB variant, the rate of CD4 cell decline occurs twice as fast, as these cells are the primary target of HIV.
This accelerated attack on the immune system directly impacts the progression of the illness. Without treatment, a person with the VB variant could advance to late-stage HIV, sometimes referred to as AIDS, in as little as two to three years after diagnosis. This is a much shorter timeframe compared to the six to seven years observed with other common HIV strains.
Transmission and Diagnosis
The VB variant is transmitted in the same ways as all other known strains of HIV. The virus is passed through specific bodily fluids, most commonly through unprotected sexual contact or the sharing of injection drug equipment. Established prevention methods remain unchanged.
A consequence of the higher viral load associated with the VB variant is an increased likelihood of transmission. When an individual has more virus particles in their blood, the chances of passing the virus to another person during a risk event are higher.
Standard HIV diagnostic tests that are currently in use are fully capable of identifying this variant. There is no separate or unique test needed to determine if an individual has this specific version of HIV.
Effectiveness of Antiretroviral Therapy
Current medical treatments for HIV are highly effective against the VB variant. Studies show that once individuals with this variant begin antiretroviral therapy (ART), their outcomes are comparable to those of people with other HIV strains.
After starting treatment, patients with the VB variant experience similar immune system recovery and survival rates. The therapy works to suppress the virus in the blood, often to undetectable levels. When the virus is suppressed, the immune system, measured by CD4 cell counts, can rebound and recover its strength.
The discovery of the VB variant highlights the importance of widespread and early HIV testing. Because this variant can cause faster immune system damage, prompt diagnosis and quick initiation of ART are especially important. Early intervention can halt the rapid decline of CD4 cells and prevent the progression to more advanced disease.