February 9, 2011
Infants Exposed To HIV At Birth But Not Infected May Have Lower Antibody Levels
In a study that included infants from South Africa, those who were exposed to human immunodeficiency virus (HIV) at birth but did not become infected had lower levels of antibodies to diseases such as pertussis, tetanus and pneumococcus, compared to infants of non-HIV infected mothers, according to a study in the February 9 issue of JAMA.
Infectious diseases account for nearly 6 million deaths worldwide annually in children younger than 5 years. Immunization against vaccine-preventable infections is essential to reducing childhood mortality. "The high prevalence of maternal HIV in many parts of the resource-poor world, coupled with successful programs to reduce mother-to-child transmission of HIV, has led to increasing numbers of HIV-exposed infants who are not HIV-infected themselves (i.e., HIV-exposed infants). These infants and children represent a vulnerable group with increased rates of lower respiratory tract infection and meningitis and up to 4-fold higher mortality in the first year of life," the authors write. "Altered immune responses might contribute to the high morbidity and mortality observed in HIV-exposed uninfected infants."Christine E. Jones, B.M.B.S., M.R.C.P.C.H., of Imperial College London, and colleagues studied the association of maternal HIV infection with maternal- and infant-specific antibody levels to Haemophilus influenzae type b (Hib), pneumococcus, Bordetella pertussis antigens, tetanus toxoid, and hepatitis B surface antigen. The study was conducted in Khayelitsha, Western Cape Province, South Africa, between March 2009 and April 2010 and included 109 HIV-infected and uninfected women and their infants. Serum samples from 104 women and 100 infants were collected at birth and samples from 93 infants were collected at 16 weeks, with levels of specific antibodies measured.
The authors found that at birth, HIV-exposed uninfected infants (n = 46) had significantly lower specific antibody levels compared with unexposed infants (n = 54) to Hib, pertussis, pneumococcus and tetanus. Similarly, a smaller proportion of these infants had antibody levels deemed to be protective.
To investigate the mechanisms associated with infant response, the researchers measured specific maternal antibody levels: HIV-infected women (n=46) had lower specific antibody levels than uninfected women (n = 58) to Hib and pneumococcus, with no differences observed for pertussis or tetanus.
The researchers also found that HIV-exposed uninfected infants (n = 38) compared with HIV-unexposed infants (n = 55) had robust antibody responses following vaccination, with higher antibody responses to pertussis and pneumococcus.
"We were unable to correlate antibody levels with long-term vaccine responses or clinical outcomes in the women or infants. However, our data contribute to a potential explanation for the higher morbidity and mortality observed among African HIV-exposed infants," the authors write. "Our data highlight the need for larger prospective studies to determine whether the lower antibody levels in HIV-exposed infants at birth translate into increased morbidity from vaccine-preventable infections."
The researchers add that the results of their study support the evaluation of new maternal and neonatal immunization strategies to augment specific antibody responses and potentially prevent infections in infants in early life, particularly in HIV-exposed infants.
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