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Regulatory T cells may help block mother-to-child HIV transmission
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ATLANTA — Infants born to mothers with HIV who were not infected at the time of birth had significantly higher levels of regulatory lymphocyte T cells than infants who were infected in utero, according to research presented at ASM Microbe.
Peter Kessler, laboratory intern at Emory University School of Medicine, and colleagues said the findings provide evidence that regulatory T cells, or Treg cells, offer protection against mother-to-child HIV transmission.
According to the researchers, only a minority of infants exposed to HIV during pregnancy are born with the infection, even in the absence of preventive interventions. However, the mechanisms of protection remain unknown.
“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,” Kessler said in a press release.
For their study, Kessler and colleagues examined blood samples from infants in Malawi who were exposed to HIV during pregnancy. Their analysis included 64 uninfected infants and 28 infants who were infected with HIV at birth. They performed flow cytometry to quantify inactivated Treg cells, as well as the frequency of T-cell activation that is necessary for HIV to infect cells.
Data showed that T-cell activation rapidly increased over the first 6 weeks of life, particularly among CD8+ T cells. An additional increase in activation was observed at 6 months, around the time when infants begin to wean off breast milk. In contrast, the prevalence of Treg cells was largely stable, decreasing slightly between 6 weeks and 6 months, then increasing slightly between 6 months and 12 months of age.
At birth, infants without HIV infection had lower levels of T-cell activation than infants with HIV (P < .01), which was expected, according to Kessler and colleagues. However, uninfected infants had a higher amount of Treg cells (P = .03), suggesting that these cells may be suppressing immune activation.
“Even though the number of babies studied is relatively small, these findings indicate that Treg, by controlling the immune activation, may lower the vulnerability of the babies to HIV or other chronic infections even before they are born,” Kessler said in the release.
Kessler, who is still in high school, said he is interested in further examining how suppression of immune activation can prevent HIV.
“We found a relationship, but the exact mechanisms are still not yet clear,” he told Infectious Disease News. “More investigation needs to be done into the mechanisms of infant exposure and what factors play into acquiring or not HIV from the mother.” – by Stephanie Viguers
Reference:
Kessler PA, et al. Abstract CIV05 712. Presented at: ASM Microbe; June 7-11, 2018; Atlanta.
Disclosure: Kessler reports no relevant financial disclosures.
Perspective
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Sallie R. Permar, MD, PhD
The protection of the majority of HIV-exposed infants against perinatal HIV transmission in the absence of antiretroviral prophylaxis remains an unsolved mystery. The finding of a potential role for infant Treg cells in protection against HIV indicates that the fetal environment and immune development is very important in defining the vertical transmission risk. These findings could help guide maternal and/or infant immunoprophylaxis strategies to eliminate pediatric HIV.
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