Comparison of Proline-glutamate-proline-glutamate-polymorphic GC-rich Sequences Family Protein Wag22 (Rv1759c), PE_PGRS31 (Rv1768), PE_PGRS32 (Rv1803), and PE_PGRS33 gene (Rv1818c) in Exponential State and Under In vitro Model of Latency in Same Clinical Isolates of Mycobacterium tuberculosis: Frameshift Mutation in Extensively Drug-resistant and Totally Drug-resistant tuberculosis Bacilli
Authors: Farnia Parissa , Farnia Poopak , Ghanavi Jalaledin , Besharati Saeid , Velayati Ali Akbar 
Published: December 2023

Background:

Proline-glutamate (PE)/proline-PE (PPE) proteins play an important role in the development of mycobacterial pathogenicity by modulating the host immune system. In the present investigation, the structural changes in PE-polymorphic GC-rich sequences (PGRS) family protein Wag22 (Rv1759c), PE_PGRS31 (Rv1768), PE_PGRS32 (Rv1803), and PE_PGRS33 gene (Rv1818c) were compared and analyzed in exponential state and underin vitromodel of latency in same clinical isolates ofMycobacterium tuberculosis(MTB).

Methods:

MTB strains were isolated from clinically and laboratory-confirmed cases of tuberculosis (TB). The TB isolates were subjected to the Xpert MTB/rifampin test and then, further susceptibility testing using proportional methods was performed on them. The isolates were characterized using both 16S–23S RNA andhsp65 genes spacer polymerase chain reaction-restriction fragment length polymorphism. Selected isolates studied at two experimental set–up at exponential phase OD 600 = 0.05 (5 cfu/mL × 106 cfu/mL) and under zero oxygen and nutrition for 26 months to selected isolates studied at two experimental setup in exponential phase OD600 = 0.05 (5 cfu/mL × 106 cfu/mL) and under zero oxygen and nutrition after 26 months. Whole-genome sequencing was performed on studied isolates and the protein structures were analyzed using a bioinformatics web server.

Results:

No deletion, insertion, or substation occurred in susceptible, mono-drug and multidrug resistant-TB isolates were observed at PE-PGRS family protein Wag22 (Rv1759c) and PE_PGRS31 (Rv1768) at exponential phase. Although, a large deletion (at Rv1759c; Rv1768) was observed in extensively drug-resistant (XDR) and totally drug-resistant (TDR) TB isolates at the exponential phase. All studied TDR-TB isolates had a common deletion position from amino acid 1 (methionine) to amino acid 83 (glycine) and from amino acid 725 (proline) to amino acid 914 (threonine) at PE-PGRS family protein Wag22 (Rv1759c). At PE_PGRS32 (Rv1803), deletion occurred from amino acid 1 (methionine) to amino acid 212 (glycine) in latent TDR-TB bacilli. No changes in Rv1803 were observed in other studied isolates. In contrast, 66.6% of studied isolates had either insertion, deletion, substitution, or combination of changes at PE_PGRS33 (Rv1818c). However, the majority of changes at Rv1818c occurred in drug-resistant isolates. We also documented the region of deletion and insertion at PE_PGRS33 (Rv1818c) is different in active and latent TDR-TB isolates.

Conclusions:

Changes in these PE-PGRS family protein was associated with drug susceptibility patterns of individual isolates. Our result showed a total frameshift mutation of protein that had a different length in comparison to the original protein. These changes might disturb the interactions between XDR and TDR-TB isolates and immune responses, which needs further investigation.