Genetic Influence of Toll-Like Receptors on Non-HIV Cryptococcal Meningitis: An Observational Cohort Study

Abstract

Background Cryptococcal meningitis (CM) is a significant source of mortality, the pathogenesis of which has not been fully understood, especially in non-HIV infected populations. We aimed to compare single nucleotide polymorphisms (SNPs) of Toll-like receptor (TLR) in non-HIV CM patients with those of healthy controls, and to assess the links among TLR SNPs, cytokine concentrations in cerebrospinal fluid (CSF), and clinical severity. Methods This observational cohort study was done in 2 stages: a discovery stage and a validation stage. We conducted a case-control genetic association study between 159 non-HIV CM patients and 468 healthy controls. TLR SNPs significantly related to susceptibility were further validated in a second cohort of 583 subjects from a certain district. Cytokine concentrations in CSF were used to evaluate the in situ immune response of CNS after infection. Correlations among TLR SNPs, CSF cytokine concentrations, and clinical severity were validated in a third prospective cohort of 99 previously untreated non-HIV CM patients. Logistic regression model was used to determine the independent predictors for disease severity. Findings In the discovery stage, the genotype distributions of 8 TLR SNPs in non-HIV CM patients exhibited a significant difference in comparison with controls, of which 3 SNPs remained statistically significant in patients without predisposing factors. In the validation stage, 5 of the 8 nominated TLR SNPs were found to influence CSF cytokine expression. Eighteen cytokines were significantly up-regulated in severely ill patients, among which 12 were affected by TLR2 rs3804099. The rs3804099 was also found in relation to disease severity. High IL-10 levels in CSF (OR 2*97, 95% CI 1*49-5*90; p=0*002) was suggested as an independent predictor for severity after adjusted for possible confounders. Interpretation TLR participate in both the occurrence and the pathogenesis of non-HIV CM. The in situ immune responses of CM were under genetic influence of TLR and contributed to disease severity. Our findings inform of an opportunity for early evaluation and treatment of non-HIV CM. TLR might also become a potential target on which to base host-directed immunotherapy. Funding: National Natural Science Foundation of China and National Key Basic Research Program of China (973 Program). Declaration of Interest: We declare no competing interests. Ethical Approval: Ethical approval was obtained from the medical ethics committee of Huashan Hospital, Mengchao Hepatobiliary Hospital, Fujian HIV/AIDS Diagnosis and Treatment Center, and No. 476 Hospital of Fuzhou General Hospital.