Inhibiting Glycolysis Enhances T Follicular Helper Cell Differentiation and Survival upon Human Immunodeficiency Virus Infection

Abstract

Human immunodeficiency virus (HIV) primarily infects T helper (Th) cells. Decrease in the number of Th cells is the hallmark of HIV infection. Latent reservoirs of human immunodeficiency virus (HIV) are the leading barrier towards eradication of HIV infection. T Follicular helper (Tfh) cells are a subset of Th cells that function to provide aid to B cells for their maturation, affinity selection and antibody class switch. Several studies have shown that Tfh cells are a major reservoir of latent as well as productive hiv infection. But in contrast to the fate of other Th cell subsets, the frequency of Tfh cells was shown to have increased during HIV infection which could not be attributed to their reduced susceptibility to HIV infection. The hypothesis was that Tfh cells possess a unique metabolic phenotype that protects them from HIV induced cell death. Transcriptome analysis of Th subsets from human donors and showed that Tfh cells rely less on glycolysis for their energetic requirements and instead have increased transcription of fatty acid synthesis genes. This finding was corroborated by seahorse extracellular flux assay. The results shoId that glycolysis was not essential for Tfh cell differentiation in-vitro. The observed increase in Tfh cell frequency could not be attributed to increased Tfh differentiation upon HIV infection since HIV infection inhibited the differentiation of both non-Tfh and Tfh cells. The results found that bypassing the glycolytic pathway by providing Tfh cells with Galactose in the medium protected ex-vivo infected primary tonsillar cells from HIV induced cell death. This protection could be partly explained by the induction of Baculovirus IAP repeat containing 5 (BIRC5) when the cells utilized Galactose instead of Glucose. The studies together show that Tfh cells have an oxidative metabolic phenotype which protects them from HIV induced cell death in part by induction of BIRC5 expression.