"Type III interferons are expressed in tuberculosis granulomas and can enhance anti-mycobacterial activity of macrophages"

Public Health/Infectious Diseases and Microbiology

Committee:
Joshua T. Mattila (advisor), Department of Infectious Diseases and Microbiology
JoAnne Flynn, MMG Department
Amy Hartman, Department of Infectious Diseases and Microbiology
Simon Barratt-Boyes, Department of Infectious Diseases and Microbiology

Abstract

Humans and non-human primates express four subtypes of type 3 interferons (IFNls; IFNl1-IFNl4). Unlike type I interferons (IFN1), which have been thoroughly investigated in tuberculosis (TB), the role of IFNls and their effects on immunity in TB remain unknown. Here we examined expression of IFNl1 and IFNl4 in Mycobacterium tuberculosis infected cynomolgus macaques granulomas and investigated the effects of IFNl1, IFNl4 and IFNα signaling on macaque macrophages. We identified differential IFNl1 and IFNl4 expression in granuloma macrophages and neutrophils, including IFNl4 localization in the nuclei of epithelioid and alveolar macrophages. Further, we found that granulomas from long-term TB infection have a higher burden of IFNl1 as compared to those from acute infections. To measure IFNl1 and IFNλ4’s effect on macrophage gene expression and compare these cytokines against IFN1, we performed transcriptional profiling and IPA analysis on cytokine-stimulated macrophages to identify differentially regulated pathways. We found that IFN1 upregulated the greatest number of ISGs, followed by IFNl1, whereas IFNl4 stimulation had minimal effect on gene expression. Interestingly, pro-inflammatory genes including IL-1β, IL-8, NFKB1, NFKB2, were upregulated by IFNl1 while they were downregulated by IFN1. To determine the effects of IFNl signaling on anti-mycobacterial macrophage responses, we used a reporter Mtb strain to determine how IFNl1 and IFNl4 affect the viability of M. tuberculosis. We observed a decrease in mycobacterial transcriptional activity, as indicated by reduced GFP expression, when macrophages were activated with IFNl1 prior to infection. Furthermore, we identified that macrophage pre-treatment with IFNl1 led to enhanced acidification of macrophage phagolysosomes. Our data suggest that IFNls have non-redundant properties with type 1 interferons that may promote macrophage activation, inflammation, and antibacterial activity in TB.