Rare variants of HIV are thought to be involved in the transmission of HIV between an HIV-positive mother and her newborn, reveals a new study. This discovery paves the way for possible treatments to eliminate HIV infections in infants.
- By analyzing the blood of mothers and their infants infected with HIV, the researchers discovered that certain variants of the virus were able to evade maternal antibodies, which explains this mother-to-child transmission.
- Moreover, these variants have key genetic signatures, associated with the ability to escape total or partial neutralization of bnAbs antibodies.
Although rare, transmission of the HIV virus from an HIV-positive mother to her child is not impossible and affects more than 150,000 infants worldwide each year. These transmissions, which take place in utero, during childbirth or during breastfeeding, have long remained a mystery to the scientific community.
A new study, led by researchers from Weill Cornell Medicine and Duke University (USA) sheds light on new data that could lead to treatment to eliminate HIV infections in newborns. Published in the journal PLoS Pathogensthis new work provides evidence that this transmission of HIV from mother to child is linked to rare variants of the virus in the mother’s blood which, in addition to containing key genetic signatures, are also able to escape neutralizing antibodies (bnAbs).
Variants escaping maternal antibodies
The transmission of HIV from mother to newborn has raised questions. Indeed, even when the mother does not receive treatment to reduce her viral load, the risk of transmission is lower for the child. Scientists have therefore hypothesized that the factors determining transmission lie in the mother’s immune system and/or in the HIV variants circulating in her blood. However, it was not easy to determine the source of the risk of transmission, in particular because the antiretroviral treatment mainly used today risked distorting the results of any study relating to current patients.
The team of pediatrician Sallie Permar, who carried out the study, therefore circumvented this problem by analyzing blood samples from a study of HIV-infected mothers and their infants conducted thirty years ago.
Dr. Permar’s team isolated HIV variants that had been passed from mothers to their children, and found that these transmitted HIV variants were about 30% less sensitive to the mothers’ plasma – the component of blood containing antibodies . This means that the difference between transmission and non-transmission seemed to be due, at least in part, to HIV variants that allow maternal antibodies to escape.
Moreover, the researchers found by analyzing the genetic sequences of these transmitted variants that they contain key genetic signatures. Most of these signatures are associated with the rare ability to escape total or partial neutralization of bnAbs antibodies. “This finding suggests that the presence of broadly neutralizing antibody variants in the blood of HIV-infected mothers is a predictor of a higher risk of transmission to newborns,” says Dr. Permar.
Reduce the risk of mother-to-child transmission
This means that any vaccine or treatment given to HIV-infected pregnant or breastfeeding women, alongside antiretroviral therapy to reduce the risk of transmission, must be effective against HIV variants that can evade these special antibodies.
According to the researchers, these results help predict whether HIV is transmitted from mother to infant and point the way to approaches that can help prevent this transmission. At the same time, the results indicate that treatment of HIV-positive pregnant women or new mothers with bnAb therapies might have the unintended effect of promoting the evolution of variants capable of resisting these therapies and thus increasing the risk of mother-to-child transmission.
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