Mother’s Immune System, HIV and Preterm Birth

While antiretroviral therapy (ART) has been very successful in preventing the transmission of HIV from mother to her unborn child, the fetus remains at risk of other ill effects. HIV-positive pregnant women are significantly more likely to give birth prematurely. Even if not born pre-term, babies are also underweight at birth (Small for Gestational Age) and these infants suffer considerably more health problems in their first year of life.

Dr. Nadia Chanzu believes that the connection between HIV/ART and adverse pregnancy outcomes has to do with the delicate balance of an expectant mother’s immune system with the developing baby. HIV infection and treatment of the HIV-positive mother with antiretroviral drugs, along with the poor health of the mother may be disrupting the immune equilibrium that exists between mother and unborn child. The placenta is where this balancing act takes place, which is known as a state of immunological tolerance. It is crucial that this process function correctly, as the placenta is the only physical connection between mother and child in the womb. The placenta protects the baby from infections, like HIV, and also from being rejected by the mother’s immune system. Since a fetus is “half-mom, half-dad”, without this system of tolerance, it would be detected as foreign by the mother’s body.

Pregnancy thus requires a high degree of immune regulation, the mechanisms of which Dr. Chanzu aims to work out through her current research in South Africa. Comparing HIV-positive and uninfected expectant mothers will help her better understand the normal structure and function of a growing placenta. Part of the fine-tuning of the pregnant immune system is the function of a population of regulatory cells, called Tregs. It is thought that these cells can stop the mother from rejecting her developing baby and ensure the state of tolerance. Dr. Chanzu suspects that the numbers of these very specialized cells are altered when the mother is HIV infected and being treated with antiretroviral drugs. Pregnancy is a fine balance between tolerance and inflammation and if the regulator cells go off-balance, it is suspected that inflammation wins the day and the baby is born prematurely.

Prematurity is linked to one million deaths each year and babies born to HIV-positive women are especially exposed. Dr. Chanzu hopes that her research will show that the HIV-infected mother taking antiretroviral drugs results in unregulated inflammation events in the placenta and an altered state of tolerance. This information lays the foundation for finding new therapies to help reduce these events and therefore mitigate the numbers of premature births that occur in these vulnerable populations.

Scientific title: Identification Of Immunological Risk Factors Associated With Adverse Birth Outcomes In A Setting Of In Utero HIV And Antiretroviral Drug Exposure

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Mother’s Immune System, HIV and Preterm Birth

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