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

OBJECTIVES

We explored the role of metabolic hormones and the B-cell repertoire in the association between nutritional status and vaccine responses.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Soluble HLA-G promotes Th1-type cytokine production by cytokine-activated uterine and peripheral natural killer cells

Soluble forms of HLA-G (sHLA-G) have been implicated in immune regulation. Fetal trophoblast cells are a prime source of HLA-G. Hence, an interaction between sHLA-G and uterine lymphocytes in the decidual tissues can easily be envisaged. These lymphocytes, when properly activated, are implicated in successful trophoblast invasion, placental maturation and maintenance of pregnancy. However, so far, no data are available on the effect of sHLA-G on the function and phenotype of these cells. Herein, we used a recombinant sHLA-G construct to determine the effect of sHLA-G on uterine lymphocyte cells present in endometrium at the time that it is optimally receptive to trophoblast invasion. In addition, we ascertained the effect of sHLA-G on peripheral lymphocytes. We found that upon co-culture with sHLA-G, proliferation of unfractionated IL-15-stimulated uterine mononuclear cells (UMCs) was inhibited. However, sHLA-G increased both interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha production by these cells. Vascular endothelial growth factor (VEGF) production was reduced. Notably, in contrast to membrane-bound HLA-G, sHLA-G did not affect the natural cytolytic activity of UMCs. Similarly, sHLA-G inhibited proliferation but stimulated pro-inflammatory cytokine production by cytokine-activated, unfractionated peripheral blood mononuclear cells (PBMCs). In addition, we showed that the overall inhibitory effect of sHLA-G on proliferation of the whole cell population could be ascribed to selective inhibition of CD4(+) T cells. In contrast, sHLA-G induced proliferation and IFN-gamma production by both uterine and peripheral natural killer (NK) cells. In conclusion, our data show that the sHLA-G modulates both UMC and PBMC function. sHLA-G, by promoting IFN-gamma production by uterine NK cells, may contribute to vascular remodelling of spiral arteries to allow for successful embryo implantation.

Hormonal stimulation for IVF treatment positively affects the CD56bright/CD56dim NK cell ratio of the endometrium during the window of implantation

The effects of hormone stimulation for IVF treatment on endometrial receptivity remain controversial. Since CD56(bright) natural killer (NK) cells in the endometrium positively contribute to implantation and decidualization whereas CD56(dim) NK cells are negatively associated with reproduction, shifts in the balance between those cells will affect receptivity. Therefore, we compared the leukocyte composition in the endometrium of IVF women (n=20) with non-pregnant women (n=18) in a natural cycle, as a parameter for endometrial quality. Biopsies were obtained 7 days after ovulation. Histological dating of the endometrium showed no increased endometrial advancement after IVF treatment as compared to the control group. Flow cytometric analysis of leukocyte subsets showed that hormonal stimulation positively affected the CD56(bright)/CD56(dim) ratio in the endometrium by a relative decrease in the cytotoxic CD56(dim)CD16(+) NK cell numbers. The relative number of T-cells remained unaffected, while the number of non-T and non-NK cells (i.e. B-cells and macrophages) was higher in the IVF group. These effects were restricted to the endometrium and not observed in peripheral blood. Within the CD56(bright) population we could identify a distinct subset of NK cells (CD56(superbright)) that was unique for the endometrium. We conclude that hormonal stimulation for IVF treatment positively affects the CD56(bright)/CD56(dim) ratio of the endometrium during the window of implantation and does not affect endometrial advancement.