Impact of Gene Polymorphisms on Infection and Pathogenesis.

PE_PGRS33 is a surface-exposed protein of () which exerts its role in macrophages entry and immunomodulation. In this study, we aimed to investigate the polymorphisms in the gene of clinical isolates and evaluate their impact on protein functions. We sequenced in a collection of 135 clinical strains, genotyped by 15-loci MIRU-VNTR and spoligotyping and belonging to the complex (MTBC). Overall, an association between alleles and MTBC genotypes was observed and a dN/dS ratio of 0.64 was obtained, suggesting that a purifying selective pressure is acting on against deleterious SNPs. Among a total of 19 alleles identified in this study, 5 were cloned and used to complement the knock-out mutant strain of H37Rv (Δ33) to assess the functional impact of the respective polymorphisms in infections of primary macrophages. In human monocyte-derived macrophages (MDMs) infection, large in-frame and frameshift mutations were unable to restore the phenotype of H37Rv, impairing the cell entry capacity of , but neither its intracellular replication rate nor its immunomodulatory properties. studies performed in the murine model of tuberculosis (TB) demonstrated that the Δ33 mutant strain was not impaired in the ability to infect and replicate in the lung tissue compared to the parental strain. Interestingly, Δ33 showed an enhanced virulence during the chronic steps of infection compared to H37Rv. Similarly, the complementation of Δ33 with a frameshift allele also resulted in a strain capable of causing a surprisingly enhanced tissue damage in murine lungs, during the chronic steps of infection. Together, these results further support the role of PE_PGRS33 in the pathogenesis and virulence of .