The human immunodeficiency virus, or HIV, infects and destroys CD4 cells (immune cells) and reduces the number of these cells. If left untreated, the infection will turn into AIDS.
In people infected with a new type of HIV called VB, the number of CD4 cells decreases twice as fast as in people close to HIV strains, that is, strains of the same genetic subtype (B).
Without treatment, VB infections are likely to turn into AIDS on average within two to three years after the initial diagnosis of HIV, researchers reported in the February issue of the journal Science. In the case of other versions of the virus, the same reduction occurs on average approximately six to seven years after diagnosis. “The study’s lead author, Chris Weiment, told LiveScience:”
On average, people infected with this species develop advanced HIV within 9 months if they do not start treatment and are diagnosed with an infection in the fourth decade of life. Progress will be faster in older people.
The researchers found that antiretroviral drugs, the standard treatment for HIV, were just as effective against VB strains as they were against other versions of the virus. “For a person who is successfully treated, the decline of the immune system to AIDS is stopped and the transmission of the virus to other people is inhibited,” Weiment said.
Katie Atkins, an associate professor at the London School of Tropical Health and Medicine who did not participate in the study, said:
The authors use a case study to emphasize the importance of global access to treatment. The reason for the importance of access to treatment is both the reduction in the number of people who die from AIDS and the reduction in the circulating virus, thus reducing the likelihood of new and more deadly species emerging.
How a new type of HIV was identified
Weiment and Christoph Fraser, an infectious disease epidemiologist and lead author of the study, are key members of the BEEHIVE project, which seeks to better understand the biology, evolution, and epidemiology of HIV. “The BEEHIVE project was launched in 2014 to understand how genetic changes in the virus make a difference in the disease,” Weiment said. The project collects data on seven HIV groups in Europe and one group in Uganda.
Analyzing data from an ongoing study, the researchers identified 17 distinctly infected people with HIV, all of whom had high concentrations of the virus in their blood early in the infection (between six months and two years after diagnosis). Fifteen infected people were from the Netherlands, one from Switzerland and one from Belgium.
The researchers found that the newly identified species belonged to genetic subtype B. This subgroup includes a group of HIV viruses that are closely related to each other and are found mainly in Europe and the United States.
To see if more specimens of the species could be found in the Netherlands, the researchers looked at data from the ATHENA group, which includes a large group of HIV-positive people in the Netherlands who were diagnosed with the disease between 1918 and 2015.
Viral genetic sequencing data were available to more than 8,000 of these individuals, of whom about 6,700 were infected with subtype B viruses. Within this group, 92 individuals with distinct VB species were identified, bringing the total to 109.
According to available clinical data, the viral load of these 109 people was about 3.5 to 5.5 times higher than that of those infected with other subgroups of B group. Also, at the time of diagnosis, VB-infected individuals had lower CD4 counts than those infected with other strains. Thus, in comparison with other newly diagnosed HIV-infected individuals, their CD4 counts started both lower and decreased faster.
The researchers examined the genome of the VB species to explain the sharp increase in pathogenicity. They found that it has many mutations that are scattered throughout its genome. Therefore, they can not currently identify a single genetic cause for the increased virulence of the virus. “It is unlikely that a mutation or even a gene would be responsible for this change,” said Joel Wertheim, an associate professor of medicine at the University of California, San Diego, who did not participate in the study.
The researchers created a diagram called the phylogenetic tree (progeny tree) based on available genetic data, which is similar to the typical family trees for humans, showing the degree to which individuals interact. Based on this tree, they estimated that the VB species probably first appeared in the Netherlands in the late 1980s or 1990s.
At about that time, the US Food and Drug Administration approved the first antiretroviral treatment for HIV, and treatments that use a combination of antiretroviral drugs were not yet available, according to a 2019 review in the journal Health Affairs. Atkins said:
During this decade, the number of HIV-infected people who were not treated was high in Western Europe, and their viral infections were not suppressed. The large number of people who were not virally repressed created a large viral population in which a new strain could emerge.
Weiment said the tree indicates that people infected with VB were carriers of viruses that were closely related. Accordingly, the evolution of a virus occurs shortly between the time a person became infected and the time it was transmitted to another person. In other words, the new strain, in addition to being highly pathogenic, is likely to be more transmissible than other versions of HIV. However, according to Weimant, this finding is less conclusive than the evidence for increased pathogenicity, as the progeny tree provides indirect evidence of virus transmissibility.
After the emergence of VB in the 1980s or 1990s, the number of people infected with the species increased steadily until around 2010. At the same time, the proportion of new VB cases among all new subgroup B cases began to increase. This increase peaked around 2008 and then gradually declined. The decline is likely the result of the Netherlands’s extensive efforts to curb the transmission of any type of HIV.
The authors note that the absolute number of VB and non-VB diagnoses was declining at this time, and there is some uncertainty about the exact ratio of VB to non-VB infections.
Wertheim said the discovery of a highly pathogenic HIV strain was not surprising. He said:
This finding is consistent with both evolutionary theory and the trend of increasing pathogenicity we have observed in the United States over the decades. I was amazed at how obvious and distinctive the newly identified cluster was.
Wertheim expects many groups around the world to start screening their data to see if the VB species has spread to other regions. “I am also curious to see if similar species have appeared in other parts of the world,” he said.
The researchers found no evidence of the species outside the Netherlands, other than those found in individuals from Switzerland and Belgium. Weiment said they searched for viral genetic sequences in the Valley and found no trace elsewhere, but there may be a small number of people infected with the species that have not yet been identified. “By making the VB species sequence available, we allow researchers in different countries to review their private data,” he said.
Future studies in the valley of the VB species could show how the species accumulates in the blood and rapidly destroys CD4 cells, as well as provide more details on how the species evolved.
Weiment said they found evidence that the VB species evolved over time, so they could not determine if it evolved in several people or in just one person.
But should the general public be concerned about the newly identified type of VB? “Weiment,” he said.
People should not worry. Finding this species underscores the importance of pre-existing guidelines: People at risk for HIV should have access to regular tests for initial diagnosis and immediate treatment. These principles apply equally to the case of the VB type.