Protecting HIV-exposed babies

Every year, approximately 1.5 million babies are born to HIV-infected mothers around the world. In South Africa, where as many as 30 per cent of women of childbearing age are HIV-positive, an estimated 300,000 HIV-Exposed but Uninfected (HEU) babies are born annually.

“This represents a large proportion of newborns in this region of Africa, but we know very little about how prenatal exposure to HIV impacts their immune system and overall health,” says UBC Pediatrics Professor David Speert.

A pilot study currently undertaken by Speert and his collaborators from Tygerberg Children’s Hospital and Stellenbosch University in South Africa confirms that HEU babies are subject to some of the same life-threatening infections typically seen in HIV-positive infants, possibly due to a combination of immunological, environmental and social factors.

“We found that the immune systems of HEU babies are in a hyper inflammatory state—this is consistent with early HIV infection and could, along with other factors, cause them to be more susceptible to diseases and infections,” says Speert, the Sauder Family Professor of Pediatrics in the UBC Faculty of Medicine.

Thanks to a $500,000 grant from  UBC’s Peter Wall Institute for Advanced Studies, Speert is embarking on a larger-scale study to further investigate the reasons why HEU babies suffer from impaired immune systems. The new study—the first of its kind—will involve 100 HEU babies and the same number of infants born to HIV-negative women, all delivered at Tyerberg Hospital in Cape Town.

Humans are protected from infection by both innate and adaptive immunity, explains Speert, who also heads the Centre for Understanding and Preventing Infection in Children at the Child & Family Research Institute. Innate immunity is present from birth and does not change very much throughout life, but defects in innate immunity are often manifested as increased infections early in life.

Adaptive immunity, or ‘learned’ immunity, develops through contact with infectious agents or vaccines  and begins with the transfer of immunoglobulin from the placenta to the fetus and through breast milk after birth.

“We believe HEU babies are compromised in both types of immunity,” says Speert. “What we want to find out is how exposure to HIV in the womb affects the development of the infant’s innate immune system, how the postnatal environment impacts the child’s adaptive immunological response and how the innate and adaptive systems interact.”

The unique project is urgently needed partly due to the growing number of HEU babies born each year, and partly due to a shortage of research that could directly inform the  establishment of clinical guidelines in  developing countries, according to Speert.

Effective prevention programs, including the use of anti-retroviral drugs during pregnancy and after childbirth, have all but eradicated mother-to-child infection of HIV and help keep HEU babies healthy after birth in North America. In B.C., the infection rate has remained zero for the past two years. But these strategies are difficult to implement in less privileged environments.

“For example, HIV-infected mothers are encouraged to use formula exclusively in North America to prevent mother-to-child infection,” says Speert. “In parts of Africa, where safe drinking water may not be easily accessible, breast feeding is still regarded as a safer practice.” The safety of breast feeding by HIV-infected mothers in Africa has lately been enhanced by providing anti-retroviral drugs to nursing mothers and/or their babies irrespective of the maternal immune status.

“In addition, the environment HEU babies are born into—poor nutrition, reduced parental-infant interaction and bonding, exposure to antiretroviral drugs, infectious agents in the household and other environmental contaminants—could play a role in the development of their adaptive immune system,” says Speert.

“Since the problems of HEU infants have only been appreciated for less than a decade, very little research has been conducted,” says Speert. “The knowledge we glean will help us find ways to protect this very vulnerable population.”