Dysfunctional immunity in the comorbidity of vitamin A deficiency and tuberculosis identifies therapeutic potential of vitamin A supplementation

Introduction: Clinical tuberculosis (TB) is frequently associated with an acquired risk factor. Malnutrition is a major recognized risk factor for progression to active or clinical TB. Among the micronutrient deficiencies accompanying malnutrition, vitamin A deficiency carries up to a 10-fold risk of progression to active or clinical TB, but the impact of this deficiency on immunity is poorly understood in the context of TB. Methods: Using the guinea pig model of vitamin A deficiency and TB comorbidity, we evaluated immune parameters across multiple stages of TB disease progression. Guinea pigs with dietary-induced pre-existing vitamin A deficiency were exposed to a low dose aerosol of Mycobacterium tuberculosis (Mtb) and compared to Mtb exposed guinea pigs with sufficient dietary vitamin A. Immune response was evaluated at multiple endpoints post-infection by histopathology and flow cytometry, incorporating single cell RNAseq and spatial transcriptomics and in a subset of the guinea pigs. Results: Vitamin A deficient guinea pigs develop granuloma pathology devoid of necrosis, the hallmark feature of this model species. Flow cytometry revealed an inverted ratio of CD4:CD8 cells, where CD8 cells are increased in isolated granulomas of vitamin A deficient guinea pigs. Initial transcriptomic analysis identified 15 cell clusters based on UMAP dimensional reduction, among which multiple are enriched in either vitamin A deficient or vitamin A sufficient guinea pigs. Initial pathway analyses indicated enrichment among markers of cytotoxic cell activity in vitamin A deficiency, while neutrophil degranulation was enhanced among guinea pigs sufficient in vitamin A. Furthermore, vitamin A signaling and metabolism is highly enriched in infected lung of guinea pigs sufficient in vitamin A, indicating that vitamin A contributes to the typical pulmonary immune response to Mtb infection. Conclusion: Collectively, these data indicate a potential compensatory role for CD8 cytotoxic T cell function in the absence of vitamin A and provides a link between dysfunctional CD4 T cells and neutrophil pulmonary pathology. Discussion: The use of animal models of TB risk factors offers new insight into immune mechanisms that drive tuberculosis susceptibility and points for therapeutic intervention in the context of vitamin A deficiency.