Nutrient Deficiencies and Potential Alteration in Plasma Levels of Naturally Acquired Malaria-Specific Antibody Responses in Tanzanian Children

Immunoglobulin G (IgG) subclasses have been suggested to confer naturally acquired immunity to Plasmodium falciparum malaria. Cytophilic IgG1 and IgG3 with their potential for opsonization, phagocytosis, and antibody-dependent cellular inhibition in association with monocytes have been suggested to have a critical role in malaria. The potential for production of antibodies is influenced by micronutrient status. This study aimed at exploring the effect of micronutrients, particularly zinc status, on the profiles of IgG subclasses in 304 Tanzanian children aged ≤ 5 years. An enzyme-linked immunosorbent assay was performed using whole asexual blood stage malaria antigens to determine plasma malaria-specific antibody titers. This baseline cross-sectional study was done from 2005 - 2010 prior to the larger randomized control trial of the Micronutrient and Child Health (MACH) Study. Plasma concentrations of zinc and magnesium were measured by inductively coupled plasma atomic emission spectrometry and results correlated with plasma IgG subclass levels. The findings reveal zinc deficiency to possibly influence the production of IgM, total IgG, and several IgG subclasses in a malaria status-dependent manner. Among IgG subclasses, IgG3 and partly IgG2 displayed a remarkable association with zinc deficiency, particularly IgG3 which was predominant in children with malaria. Nevertheless, zinc, magnesium, and malaria status did not influence the association between IgG3 and IgG4. The study leads to the conclusion that, under conditions of micronutrient deficiency and malaria status, an imbalance in IgG subclass production may occur leading to predominantly higher levels of IgG3 and IgG2 that may not confer sufficient protection from infection. The profile of both cytophilic and non-cytophilic IgG subclasses has been shown to be variably influenced by zinc status; the effects vary with age at least in under-fives. These results provide insight for inclusion of micronutrients, particularly precise amounts of zinc, in future malaria interventional programs in endemic areas.