A novel adjuvant-free H fusion system for the production of recombinant immunogens in Escherichia coli: Its application to a 12 kDa antigen from Cryptosporidium parvum.

The production of recombinant antigens in Escherichia coli and specific polyclonal antibodies for diagnosis and therapy is still a challenge for world-wide researchers. Several different strategies have been explored to improve both antigen and antibody production, all of them depending on a successful expression and immunogenicity of the antigen. Gene fusion technology attempted to address these challenges: fusion partners have been applied to optimize recombinant antigen production in E. coli, and to increase protein immunogenicity. Taking a 12-kDa surface adhesion antigen from Cryptosporidium parvum (CP12) by example, the novel H fusion partner was presented in this work as an attractive option for the development of recombinant immunogens and its adjuvant-free immunization. The H tag (of only 1 kDa) efficiently triggered a CP12-specific immune response, and it also improved the immunization procedure without requiring co-administration of adjuvants. Moreover, polyclonal antibodies raised against the HCP12 fusion antigen detected native antigen structures displayed on the surface of C. parvum oocysts. The H tag proved to be an advanced strategy and promising technology for the diagnosis and therapy of C. parvum infections in animals and humans, allowing a rapid and simple recombinant production of the CP12 antigen.