Evaluation of human β‑defensins in the cerebrospinal fluid of suspected meningitis

Human β-defensins (HBDs) are an important class of antimicrobial peptides that have immunomodulatory functions; however, the role of HBDs have not been well explored in the pathogenesis of meningitis. A cross-sectional study was performed to explore the levels of HBD1, HBD2, HBD3, and HBD4 in the cerebrospinal fluid (CSF) of 176 suspected meningitis cases. CSF samples were first subjected to PCR analysis using a set of universal primers targeting a portion of the eubacteria 16S rRNA gene. The analysis demonstrated that 66 samples (37.5%) were PCR-positive, whilst 110 samples (62.5%) were PCR-negative. DNA sequence analysis of the PCR-positive products identified two broad categories of bacteria, Gram-negative (68.2%) and Gram-positive (31.8%). A total of 88 PCR-negative CSF samples showed abnormal leukocyte counts, glucose concentrations, and/or protein concentrations, and were considered abnormal (ABN). The remaining 22 CSF samples were considered normal (NOR). HBD1, HBD2, and HBD4 levels did not exhibit significant differences between PCR-positive, ABN, and NOR CSF samples. However, HBD3 levels were significantly higher in the ABN CSF samples than in the NOR CSF samples (P=0.005). HBD3 levels were also elevated in the PCR-positive CSF samples compared with the NOR CSF samples, but the difference was not significant (P=0.151). HBD2, HBD3, and HBD4 were correlated with leukocyte counts, glucose concentration, and protein concentration. In conclusion, HBD3 levels were significantly elevated in the CSF of suspected meningitis cases regardless of the cause of meningitis. The CSF levels of certain HBDs were affected by specific diagnostic laboratory parameters for meningitis, including leukocyte counts, glucose concentration, and protein concentration.