Production and characterization of polyclonal antibody against major capsid protein of Salmonella bacteriophage SE-W109

Abstract

Salmonella spp., are important foodborne pathogens that are predominantly found in poultry, swine, eggs and dairy
products. Rapid detection of Salmonella contamination in animals and food is urgently needed to reduce the risk of
infection. Bacteriophages or phages are viruses that specifically infect and kill bacteria. Our research team at the
Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand isolated
Salmonella phage SE-W109 that demonstrated a broad host range of infection to various serovars of Salmonella spp., but
that did not cross-react with other Gram-negative bacteria. We then set forth to develop this phage for the rapid detection
of Salmonella spp. contamination in food samples. However, to achieve this objective, a polyclonal antibody against
Salmonella phage SE- W109 is required. In the present study, an optimization condition for rabbit immunization to
generate an anti- phage antibody was successfully developed. Western blot analysis revealed that the generated
antibody recognized the 45 kDa antigen of Salmonella phage SE-W109 and that it had no cross-reaction with other
Salmonella phages or with Salmonella spp. Mass spectrometry analysis and PCR sequencing revealed the 45 kDa antigen
to be a major capsid protein of Salmonella phage SE-W109. In conclusion, we report the protocol for generating a
polyclonal antibody against a Salmonella phage and that the main antigen recognized by antiserum is a major capsid
protein. The identified antibody will be used for further development of a phage-based method for detection of
Salmonella contamination in food samples.