Human hookworm infection enhances mycobacterial growth inhibition and associates with reduced risk of tuberculosis infection.

Soil-transmitted helminths and Mycobacterium tuberculosis frequently coincide geographically and it is hypothesized that gastrointestinal helminth infection may exacerbate tuberculosis (TB) disease by suppression of Th1 and Th17 responses. However, few studies have focused on latent TB (LTBI) infection, which predominates globally. We performed a large observational study of healthy adults migrating from Nepal to the UK (n=645). Individuals were screened for LTBI and gastrointestinal parasite (GIP) infections. A significant negative association between hookworm (HW) and LTBI-positivity was seen (OR=0.221; p=0.039). HW treatment did not effect LTBI conversions. Blood from individuals with HW had a significantly greater ability to control virulent mycobacterial growth in vitro than from those without, which was lost following HW treatment. There was a significant negative relationship between mycobacterial growth and eosinophil counts. We also analysed differential gene expression among individuals with and without HW infection, pre- and post- anti-helminth treatment. Eosinophil-associated differential gene expression characterised the whole blood transcriptome of hookworm infection and correlated with improved mycobacterial control. These data provide a potential alternative explanation for the reduced prevalence of LTBI among individuals with HW infection, and possibly an anti-mycobacterial role for helminth-induced eosinophils. Transcriptomics was performed on unstimulated whole blood samples from uninfected controls (n=9) and individuals with hookworm infection (matched pre- and post-treatment, n=11). Peripheral blood was collected in PAXgene© tubes and stored at -80oC until required for whole blood transcriptomic studies. Samples were subsequently thawed at room temperature for two hours, total intracellular RNA was extracted using the Blood RNA Kit (Qiagen) and the purity and quantity of RNA was assessed prior to storage at -20°C. Globin mRNA was depleted using the GLOBINclear Kit (Ambion), amplified and biotin-labelled using the TotalPrep RNA Amplification Kit (Illumina). RNA was purified and the quality assessed using an Agilent bioanalyser. Biotinylated cRNA was hybridised to Illumina HumanHT-12 (v4.0) expression beadchips according to the manufacturer’s instructions. Beadchips were scanned with an Illumina iScan bead array reader confocal scanner and data extracted using GenomeStudio software.