Early-life exposure to widespread environmental toxicants and children's health risks: A focus on the post-vaccination antibody potency or immunoglobulin levels

Highlights: • Altered antibody titers in post-vaccination children are related to toxicant exposure. • Prenatal exposure to environmental toxicants is related to adverse changes of Ig levels. • Exposure-altered immune components responses to antibody titers of the vaccine. • More evidences on association of air pollutants with post-vaccination are needed. Early-life exposure to widespread environmental toxicants including organic pollutants (OPs), heavy metals, and air pollutants is detrimental to human health. The immunotoxicity of these environmental toxicants are well acknowledged and a few studies have focused on the relationship between environmental toxicant exposure and vaccine antibody potency or immunoglobulin (Ig) levels in children. Altered antibody titers or Ig levels in post-vaccination children were correlated with these environmental exposures; however, the effects of environmental toxicants on post-vaccination antibody potency or Ig levels in children have not been summarized. The objectives of this systematic review are therefore 1) to summarize the current studies concerning the associations of early-life exposure to environmental toxicants with vaccine antibody potency or Ig levels in children; and 2) to analyze the possible mechanisms underlying exposure-related alterations of antibody titers or Ig levels against different vaccines. We searched the MEDLINE (PubMed) electronic database for relevant literature with the key terms and included articles up to September 30, 2020. Based on the eligibility criteria, 28 articles were selected. These studies investigated the associations of exposure to polychlorinated biphenyls (PCBs) (5 studies), perfluorinated compounds (PFCs) (6 studies), other OPs (4 studies), heavy metals (11 studies) and air pollutants, e.g. PM_2.5, (3 studies) with the serum-specific antibody concentrations or Ig levels against different vaccines, such as anti-Hib, tetanus, diphtheria toxoid, IgA, IgE, etc. These studies suggest that exposure to these toxicants is generally associated with decreased potency of antibodies produced from childhood immunizations and overall deficiency in vaccines' provided protection. This systematic review provides evidence that exposure-induced changes to humoral immune-related tissue/cells/molecules response to vaccines may play predominant roles in the inverse associations between antibody responsiveness to vaccines and environmental toxicants. This review could thus also help us to conduct better immunization policies for children under environmental toxicant burdens.