Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 21, 2006
Publication Date: December 8, 2006
Citation: Konjufca, V., Wanda, S., Jenkins, M.C., Curtiss, Iii, R. 2006. A recombinant attenuated Salmonella enterica Serovar Typhimurium vaccine encoding Eimeria acervulina antigen offers protection against E. acervulina challenge. Infection and Immunity. 74:6785-6796.
Interpretive Summary: Coccidiosis is an intestinal disease of poultry caused by protozoa in the genus Eimeria. The disease has serious economic impact on U.S. poultry production causing greater than $ 350 million loss per year due to poor weight gain and feed utilization in infected broilers. Worldwide avian coccidiosis causes greater than $ 1.5 billion in losses. Although the parasitic disease has been controlled in the past by the use of anticoccidial drugs in feed, the repeated appearance of drug-resistant strains and the increasing pressure to eliminate antibiotics in animal feed, has provided impetus for alternative control strategies. One such strategy is to vaccinate chickens against coccidiosis by using components of the parasite for immunization. The present paper describes successful immunization of chickens against Eimeria acervulina with a recombinant protein produced in a harmless bacterial strain of Salmonella enterica. This research shows that it is possible to vaccinate chickens against coccidiosis, but that the method of vaccine delivery is critical to the development of protective immunity.
Coccidiosis is a ubiquitous disease caused by several distinct species of intestinal protozoan parasite Eimeria spp.. Cell-mediated immunity (CMI) is critically important for protection against Eimeria, thus our approach utilizes bacterial Type Three Secretion System (TTSS) to deliver an antigen directly into the cell cytoplasm of the immunized host and into the MHC I antigen processing pathway for induction of CMI, and antigen-specific CTL responses in particular. To accomplish this goal, Eimeria genes encoding sporozoite antigen EASZ240 and merozoite antigen EAMZ250 were fused to Salmonella enterica Serovar Typhimurium effector protein gene sptP in the parental pYA3653 vector, yielding pYA3657 and pYA3658 respectively. SptP protein is secreted by TTSS of Salmonella and translocated into the cytoplasm of immunized host cells. Host-strain chromosomal copy of the sptP gene was deleted and replaced by a reporter gene xylE. Newly constructed vectors pYA3657 and pYA3658 were introduced into host strain '8879 ('PhoP233 'sptP1033::xylE 'asdA16). This strain is an attenuated derivative of highly virulent UK-1 strain. When strains '8879 (pYA3653) as the vector control and '8879 harboring pYA3657 or pYA3658 were used to orally immunize day of hatch chicks, colonization of bursa, spleen and liver were observed, with peak titers 6 to 9 days post-immunization. In vitro experiments show that EASZ240 antigen is secreted into the culture supernatant via TTSS and it is delivered into the cytoplasm of Int-407 cells by TTSS. In vivo experiments indicate that both humoral and cell-mediated immune responses are induced in RASV-vaccinated chickens, which leads to significant protection against Eimeria challenge.