Treg Cells May Protect Infants from HIV Infections in the Womb

Research conducted by the Emory Vaccine Center indicates that Treg cells, a type of regulatory lymphocyte, could be vital in protecting infants in the womb from mother-to-child HIV transmission. The findings were presented at the 2018 ASM Microbe meeting and provide a possible answer to why many infants are born without HIV when their mothers are infected.

The researchers examined infants in Malawi, who participated alongside their mothers in a clinical study, funded by the Centers for Disease Control and Prevention (CDC). The purpose of the study was to analyze methods that could prevent the spread of HIV during birth and breastfeeding.

“Finding out what protects the majority of babies is important, as it can lead to ways to boost natural immune responses and make individuals resistant to HIV infection,” said Peter Kessler, a high school student and laboratory intern with the Emory University School of Medicine in a recent statement.

Blood samples taken from 64 infants born uninfected with HIV and 28 infants born infected with HIV were examined by the team using flow cytometry, a technique that differentiates between cell types by reading the markers expressed on the surface. The researchers found that levels of Treg lymphocytes were increased at the time of birth in the uninfected infants compared with the infants who were born infected with the virus.

Lymphocytes are cells found in the immune system that are known to fight bacteria and viruses. Treg cells, also referred to as regulatory T cells, control the cells in the immune system to prevent excessive action that could result in tissue damage. There are many different forms of Treg cells, with those most well-known expressing the markers CD4, CD25, and FOXP3.

The research team discovered that HIV-infected infants had lower levels of Treg cells, but other lymphocytes had been activated in high levels. Due to the fact that HIV only infects activated cells, this suggests that the ability of Treg cells to suppress the activation of other lymphocytes could be protecting infants from HIV infection.

“Even though the number of babies studied is relatively small, these findings indicate that Treg, by controlling immune activation, may lower the vulnerability of the babies to HIV or other chronic infections even before they are born," said Kessler.

Currently, there is no vaccination for HIV. With antiretroviral medication, pregnant women are able to reduce the risk of transmitting the virus on to their child. The results of this study could indicate a future opportunity to develop a vaccine or immune-based therapy to be used with medication to prevent the spread of HIV during pregnancy.