C-165. Extensive Variation and Rapid Shift of the MG192 Sequence in Mycoplasma genitalium Strains from Patients with Chronic Infection

M. Mancuso1, L. Ma1, J. A. Williams2, B. J. Van Der Pol2, J. D. Fortenberry2, D. H. Martin1;
1Louisiana State Univ. Hlth. Sci. Ctr., New Orleans, LA, 2Indiana Univ. Sch. of Med., Indianapolis, IN.

Background: Mycoplasma genitalium (MG) causes persistent urogenital tract infection in humans. Antigenic variation of the protein encoded by the MG192 gene has been proposed as one of the mechanisms for persistence. Our specific aims were to determine MG192 sequence variation in patients with chronic MG infection and to analyze the sequence structural features of the MG192 gene and its encoded protein. Methods: Urogenital specimens were obtained from 13 patients who were followed for 10 days to 14 months. The variable region of the MG192 gene was PCR amplified, subcloned into plasmids and sequenced. Analysis of the nucleotide, deduced amino acid sequences and potential protein structure were performed.Results: Clones from 220 plasmids (5-18 clones/specimen) yielded 102 unique MG192 variant sequences. All variants when compared to the G37 type strain contained apparent base substitutions, insertions and/or deletions. Alignment analysis revealed 11 subvariable regions (V1 to V11) with different degrees of variability within and among MG strains. Subvariable region V9 was the least variable region (2 sequence types) and V4 and V6 the most variable region (48 and 43 sequence types respectively). MG192 sequences were more related within individual patients than between patients. Analysis of the V4 and V6 regions of sequential specimens obtained from one patient showed increased sequence diversity over time. Transmembrane topology analysis showed that MG192 consisted of a cleavable signal sequence at the N-terminus and a transmembrane domain at the C-terminus. Both regions V4 and V6 were topologically located in the outer membrane of the bacterium and contained potential antigenic epitopes. Conclusions: The MG192 gene is highly variable among and within MG clinical strains. The protein domains encoded by the MG192 variable regions are hypothesized to be exposed on the surface of the organism resulting in epitopes exposed to the host immune system. Rapid diversification of MG192 during genital tract mucosal infection may allow MG to evade the host immune response, thus facilitating persistent infection.