Suggests Why HIV-Uninfected Babies of Mothers with HIV Might
Be More Prone to Infections
whose mothers have HIV, but who are not HIV-infected themselves,
are born with lower levels of specific proteins in their blood
called antibodies, which fight infection, compared with babies
not exposed to HIV, a new study has found. The finding, published
today in the Journal of the American Medical Association,
might explain in part why uninfected babies born to women
with HIV have a higher risk of illness and death early in
Major programs using antiretroviral drugs have successfully
reduced the rate of mother-to-child transmission of HIV from
20-30 percent to around five percent in some areas of South
Africa and to less than one percent in developed countries.
However, HIV-uninfected infants born to HIV-infected mothers
in Africa are more prone to infections such as pneumonia and
meningitis, and up to four times more likely to die before
their first birthday, compared with babies born to HIV-negative
women. Socioeconomic factors are thought to account partially
for this discrepancy but differences in the babies' immune
systems might also be important.
The new study, by scientists from Imperial College London
and Stellenbosch University in South Africa, found that babies
born to HIV-infected mothers had significantly lower levels
at birth of antibodies against a range of bacterial infections
(Hib, pertussis, pneumococcus and tetanus).
Antibodies, which bind to specific pathogens and direct immune
cells to attack them, are transferred from mother to child
through the placenta late in pregnancy. The study found lower
levels of some specific antibodies in mothers with HIV, but
also that less antibody is transferred from mother to child
across the placenta.
Despite their low antibody levels at birth, the babies in
the study responded well to vaccination: they produced similar
levels of antibody to some vaccines and higher levels to other
"It's likely that lower antibody levels in these babies
contributes to lower protection against infection before the
babies have received their vaccines," said Dr Christine
Jones from the Department of Pediatrics at Imperial College
London, the study's first author. "Although they appear
more vulnerable in the first few months of life, the good
news is that these babies respond well to vaccination. We
might be able to protect them even better against infections,
either by vaccinating them earlier or by vaccinating the mother
in pregnancy. More research will be needed to establish what
the best way of protecting these babies might be."
The study involved 109 HIV-infected and uninfected mothers
in a community health centre in Khayelitsha, a rapidly-growing
township in Cape Town, South Africa. The researchers measured
antibody levels in the mothers at delivery and the infants
at birth. They also assessed how the babies responded to routine
vaccination by measuring the babies' antibody levels at four
months, after they had received their routine vaccines.
Amongst the HIV-negative women in the study, a third also
had low antibody levels, showing that protection against infection
in their babies might also not be optimal in some women, who
are otherwise perfectly healthy.
Dr Beate Kampmann, Reader in Pediatric Infection and Immunity
at Imperial and the senior author of the study, said: "Around
six million children under five die every year from infectious
diseases, and a lot of these deaths are preventable by using
existing vaccines. Studies like ours are helping us understand
why certain infants might be especially susceptible to infections,
and how we might tailor vaccination policies to protect vulnerable
babies more effectively."
The Imperial team will soon begin a new project studying antibody
levels in babies and mothers with and without HIV, among patient
volunteers from Imperial College Healthcare NHS Trust. This
work is funded by Imperial's Biomedical Research Centre, which
was awarded by the National Institute of Health Research (NIHR).
Investigator affiliations: Academic Department of Pediatrics,
Imperial College London, London, UK; Institute of Infectious
Diseases and Molecular Medicine, University of Cape Town,
Cape Town, South Africa; Medical Research Council (UK) The
Gambia, Fajara, The Gambia; Department of Pathology, Stellenbosch
University, Cape Town, South Africa; National Health Laboratory
Services, Tygerberg Hospital, Cape Town, South Africa; Desmond
Tutu TB Center, Department of Pediatrics and Child Health,
Stellenbosch University, Cape Town, South Africa.
CE Jones, S Naidoo, C De Beer, and others. Maternal HIV Infection
and Antibody Responses Against Vaccine-Preventable Diseases
in Uninfected Infants. Journal of the American Medical
Association 305(6): 576-584 (Abstract).
February 9, 2011.
College London. Study suggests why HIV-uninfected babies of
mothers with HIV might be more prone to infections. Press
release. February 8, 2011.
of the American Medical Association. Infants Exposed to HIV
at Birth But Not Infected May Have Lower Antibody Levels Against
Certain Diseases. Media advisory. February 8, 2011.