Clinical Mycobacterium tuberculosis isolates from the population of Łódź, Poland stimulated macrophages to the lower production of IL-12 and NO when compared to the virulent H37Rv strain

Abstract

The course of Mycobacterium tuberculosis (Mtb) infection and the outcome of clinically active tuberculosis depend on the complex interactions between the host immune system and M. tuberculosis properties. The objective of the study was to examine the virulence of local Mtb isolates from the population of Łódź in Poland. Thirty six local Mtb strains of total 234 with known transmission in the local community were randomly selected for the study. The production of IL-12 and NO by murine macrophages stimulated with Mtb isolates was assessed and compared to that of virulent H37Rv strain. It was found that only 3 strains generated significantly higher level of NO production comparing with H37Rv strain, while 21 clinical isolates (58% of total) stimulated murine macrophages to lower (p < 0.05) NO production. As many as ten Mtb isolates did not induced IL-12 production at all, and only four clinical strains induced significantly greater amounts of IL-12 than H37Rv strain. No correlation between IL-12 and NO production by Mtb isolates was found. There were no differences between clustered and non-clustered strains. Low macrophages activation by local Mtb isolates may indicate their high virulence.

Keywords: Clinical strains of M. tuberculosis; Interleukin-12; Macrophages; Nitric oxide; Virulence.