Changes in the evolution of the antigenic profiles and morphology during coccoid conversion of Helicobacter pylori.

Objectives: The significance of the coccoid forms of H. pylori is still controversial and the questions of whether these forms are viable and infective or degenerative are still open. We induced conversion from rod to coccoid forms and studied morphological changes and antigenic evolutions during this conversion and, thereby, elucidated the viability of coccoid forms.
Methods: The H. pylori strain (C001) used for Western blotting was isolated from the patient with gastric cancer. The antigenic evolution during coccoid conversion of H. pylori was studied by Western blotting, using different sera from thirty patients known to be culture positive. These sera were used to reveal the total antigens of the strain cultured for 2 days (100% rod) and 15 days (> 99% coccoid). After SDS-PAGE, with 10% separating gel of total antigens (rod and coccoid), transblotting (Trans-Blot electrophoretic cell, Bio-Rad) was taken onto a nitrocellulose membrane (Bio-Rad). Then, the blots, with human sera diluted at 1/100, were developed with color reaction by goat serum anti-human IgG with alkaline phosphatase and BCIP.
Results: The antigenic profiles were not changed in 46.7% (14/30 cases) and were changed in 53.3% (16/30 cases) during coccoid conversion. Antigenic fractions changed during coccoid conversion were protein band at 120 kDa and band at 35 kDa, and were not detected in coccus forms. The rest of the profiles were identical between rod and coccoid forms. The protein which disappeared include CagA (120 kDa) and porin, or adhesin (35 kDa). The morphological changes during coccoid conversion were U shaped at day 7, doughnut shaped at day 9 and full coccoid at day 15.
Conclusions: The results showed that coccoid forms of H. pylori retain cellular structures similar to rod form, and some of the antigens (CagA and porin) disappeared during coccoid conversion. Therefore, coccoid form might be viable and represent one of the stages of H. pylori biological cycle.