Proteomic identification of immunodominant membrane-related antigens in Campylobacter jejuni associated with sheep abortion

Campylobacter jejuni clone SA is the predominant agent inducing sheep abortion and a zoonotic agent causing gastroenteritis in humans in the United States. In an attempt to identify antigens of clone SA that may be useful for vaccine development, immunoproteomic analyses were conducted to characterize the membrane proteome of C. jejuni clone SA. 2-DE of C. jejuni membrane-related proteins was followed by immunoblotting analyses using convalescent sera that were derived from ewes naturally infected by C. jejuni clone SA. Totally 140 immunoreactive spots were identified, 50 of which were shared by all tested convalescent sheep sera. Conserved and immunodominant spots were identified by mass spectrometry. Among the 26 identified immunogenic proteins, there were 8 cytoplasmic proteins, 2 cytoplasmic membrane proteins, 11 periplasmic proteins, 3 outer membrane proteins, and 2 extracellular proteins. Notably, many of the immunodominant antigens were periplasmic proteins including HtrA, ZnuA, CjaA, LivK, CgpA, and others, some of which were previously shown to induce protective immunity. Interestingly, 11 immunoreactive proteins including 9 periplasmic proteins are known N-linked glycosylated proteins. These findings reveal immunogens that may potentially elicit protective immune responses and provide a foundation for developing vaccines against C. jejuni induced sheep abortion.

Biological significance: Campylobacter jejuni clone SA is the predominant agent inducing sheep abortion and incurs a significant economic loss to sheep producers. This emergent strain is also a zoonotic agent, causing gastroenteritis in humans. However, the immunogens of C. jejuni induced abortion are largely unknown. Considering the significance of C. jejuni clone SA in causing sheep abortion and foodborne illnesses, protective vaccines are needed to control its transmission and spread. Additionally, immunological markers are required for detection and identification of this highly pathogenic clone. To address these needs, we applied an immunoproteomic approach to identify the membrane-associated antigens of this highly virulent C. jejuni clone associated with sheep abortions in the U.S. The findings reveal immunogens that may potentially elicit protective immune responses and provide a foundation for developing vaccines against C. jejuni induced sheep abortion.