Identification and Characterization of -Actinin 1 of Histomonas meleagridis and Its Potential Vaccine Candidates against Histomonosis

Simple Summary: Histomonas meleagridis is a protozoan parasite that causes histomonosis in gallinaceous birds. This study identified alpha-actinin 1 of H. meleagridis. alpha-actinin 1 was predicted as a virulence factor involved in cell adhesion in our previous differential proteomic analysis. It localized in different cellular regions as detected by an indirect immunofluorescent assay between virulent histomonads and attenuated histomonads JSYZ. Administration of recombinant expressed rHma-actinin 1 reduced lesion scores in the cecum and liver, improved weight gain, and induced humoral and cellular immune responses against H. meleagridis in chickens. Histomonas meleagridis is a protozoan parasite that causes histomonosis in gallinaceous birds such as turkeys and chickens. Since the banning and restricted usage of effective drugs such as nitarsone, 80-100% morbidity and mortality occur in turkeys and 20-30% mortality in chickens. New ideas are needed to resolve the re-emergence of histomonosis in poultry. In this study, the alpha-actinin encoding gene from H. meleagridis was cloned. The 1839-bp gene encoding 612 amnio acids showed close phylogenetic relationships with Trichomonas vaginalis and Tritrichomonas foetus. It was then inserted into the prokaryotic expression vector pET28a(+) and induced with isopropyl-beta-D-thiogalactopyranoside. A 73 kDa recombinant protein rHm alpha-actinin 1 was obtained and purified with a Ni-NTA chromatography column. rHm alpha-actinin 1 was recognized by mouse anti-rHm alpha-actinin 1 polyclonal antibody, mouse anti-rHm alpha-actinin 1 monoclonal antibody, and rehabilitation sera from H. meleagridis infected chickens. Native ff-actinin 1 in the total proteins of H. meleagridis can also be detected with mouse anti-rHm alpha-actinin monoclonal antibody. Immunolocalization assays showed that Hm alpha-actinin 1 was mainly distributed in the cytoplasm of virulent histomonads JSYZ-D9 and in the peripheral regions (near the plasma membrane) of attenuated histomonads JSYZ-D195. Based on in vivo experiment, when chickens were subcutaneously immunized with rHm alpha-actinin 1 at 5 and 12 days old and then challenged with H. meleagridis at 19 days old, rHm alpha-actinin 1 reduced the lesion scores 12 days after infection (31 days old) and increased the body weight gain during the challenged period (19-31 days old). Furthermore, it also strengthened the cellular and humoral immune responses 7 days after the second immunization (19 days old). In conclusion, Hm alpha-actinin 1 could be used as a candidate antigen to develop vaccines against chicken histomonosis.