Impact of nutritional status on vaccine-induced immunity in children living in South Africa: Investigating the B-cell repertoire and metabolic hormones.

• Underweight children had decreased antibody response after pneumococcal vaccination. • Specific B-cell subsets were associated with pneumococcal antibody decay. • B-cells, metabolic hormones and nutritional status correlated with vaccine response. We explored the role of metabolic hormones and the B-cell repertoire in the association between nutritional status and vaccine responses. In this prospective cohort study, nested within a larger randomized open-label trial, 211 South African children received two doses of measles vaccine and two or three doses of pneumococcal conjugate vaccine (PCV). Metabolic markers (leptin, ghrelin and adiponectin) and distribution of B-cell subsets (n = 106) were assessed at 18 months of age. Children with a weight-for-height z-score (WHZ) ≤ −1 standard deviation (SD) at booster vaccination had a decreased mean serotype-specific PCV IgG response compared with those with WHZ > −1 and <+1 SD or WHZ ≥ +1 SD at 9 months post-booster (18 months of age). (Naive) pre-germinal center B-cells were associated with pneumococcal antibody decay between one to nine months post-booster. Predictive performance of elastic net models for the combined effect of B-cell subsets, metabolic hormones and nutritional status (in addition to age, sex, and randomization group) on measles and PCV vaccine response had an average area under the receiver operating curve of 0.9 and 0.7, respectively. The combined effect of B-cell subsets, metabolic hormones and nutritional status correlated well with the vaccination response for measles and most PCV serotypes. ClinicalTrials.gov registration of parent studies: NCT02943902 and NCT03330171. [ABSTRACT FROM AUTHOR]