The impact of Vitamin D supplementation on immune responses to respiratory pathogens in older children in Zambia with perinatally-acquired HIV-1

The purpose of this project is to assess whether vitamin D supplementation improves immune responses to respiratory pathogens in children living with HIV (CWH) in Sub-Saharan Africa. This study will be embedded in a larger ongoing vitamin D intervention trial in Zambia.

Sub-Saharan African children are disproportionately affected by the global HIV epidemic. Of the two million children living with HIV globally, 90% reside in Sub-Saharan Africa. Despite the roll-out of antiretroviral therapy (ART), HIV and its associated comorbidities remains one of the leading causes of death among children in Sub-Saharan Africa. While ART has greatly improved this cohort's survival into adolescence, these individuals continue to suffer from chronic comorbidities, principal among which are severe and recurrent respiratory infections. It is believed that a major contributor to this problem is vitamin D deficiency. CWH in Sub-Saharan Africa tend to have very low levels of vitamin D, and this has pleiotropic effects on health with major adverse effects on immune function. Additionally, in other settings, vitamin D deficiency has been established as a well-recognised contributor to poor outcomes in respiratory infections. It has therefore been hypothesised that vitamin D supplementation in CWH (alongside ART) will have wide-ranging health benefits, including a reduction in susceptibility to respiratory infection. This hypothesis is being tested in the EDCTP-funded VITALITY trial, a large ongoing study of weekly high-dose vitamin D3 supplementation in adolescents with perinatally acquired HIV-1 in Zambia and Zimbabwe.

The proposed project will form a sub-study within VITALITY, testing the hypothesis that vitamin D3 supplementation improves immune responses to respiratory pathogens. To do this, the following parameters will be measured:

1. Soluble and Cellular Markers of Immunity
Samples from the VITALITY trial will be evaluated for both cellular and soluble markers of immunity. Tests of T-cell immunity will include flow cytometric assessment of T-cell subsets such as TH1, TH2, TH17 and T-Regulatory cells, and evaluation of changes in CD8+ and CD4+ T-Cell activation. Soluble markers will be investigated using a multiplexed approach to identify proinflammatory markers in patient samples. In vitro stimulation assays will be conducted to test pathogen-specific responses to bacterial pathogens such as Streptococcus pneumoniae and Mycobacterium tuberculosis, and viral pathogens such as Influenza A, RSV and in selected cases SARS-CoV-2.

2. Allelic Variants in the Vitamin D Pathway
It has been shown that allelic variants in the vitamin D pathway are associated with increased risk to respiratory infection. As a result, patient samples (n=420) will be retroactively stratified by genotype to determine if response to treatment varies according to variants at vitamin D associated genes. This information will furthermore be used to determine the impact of genotype on clinical response to vitamin D therapy.

The findings of this work will demonstrate whether vitamin D supplementation improves protective immune responses to respiratory diseases in this at-risk population. Likely mechanisms will be elucidated leading to a better understanding of how mediators such as vitamin D modulate immunity. Given ongoing respiratory epidemics, and novel respiratory virus pandemics such as COVID-19, the findings of this study could address an unmet clinical need by providing an inexpensive and easily scalable treatment to improve health outcomes for CWH.

Through this project the student will develop a range of skills including lab-based skills, statistical skills and associated computational skills, experience in translational research, and the experience of working on-site at a large clinical trial in Lusaka, Zambia.