EVALUATION OF THE ANTIGENICITY AND IMMUNOGENICITY OF Eimeria tenella BY REPRODUCTIVE INDEX AND HISTOPATHOLOGICAL CHANGES OF CECAL COCCIDIOSIS VIRULENT LIVE VACCINE IN BROILER CHICKENS

Development and evaluation of protective immunity of a ROP27 DNA vaccine against Eimeria tenella in chickens

This study aimed to develop and evaluate the protective immunity of a ROP27 DNA vaccine against Eimeria tenella (E. tenella) in chickens. E. tenella is a parasitic protozoan that poses a significant threat to the poultry industry. The rhoptry protein 27 (ROP27) of E. tenella has been shown to have immunoprotective properties. However, traditional protein expression methods are time-consuming and labor-intensive, limiting large-scale production. In this study, we developed a pVAX-ROP27 DNA vaccine and confirmed its expression in chickens using RT-PCR and Western blot analysis. The protective immunity of the DNA vaccine was evaluated through an animal experiment with different immunization doses. The results confirmed the successful construction of the pVAX-ROP27 DNA vaccine and its in vivo expression. Chickens immunized with the vaccine at different doses showed significant improvements in average weight gain, relative weight gain rate (RWG), cecal lesion score reduction (RLS), and oocyst reduction rate, as well as a decrease in oocysts per gram (OPG). The group immunized with 100 μg/feather of pVAX-ROP27 exhibited the most significant effect, achieving an anticoccidial index (ACI) of 179.80. Additionally, levels of IL-2, IFN-γ, IL-6, IgG, and IgY significantly increased with the number of immunizations, whereas IL-4 and IL-10 showed no significant differences. Histopathological analysis of the ceca revealed that lesions were least severe in the 100 μg/feather pVAX-ROP27 immunized group. These findings suggest that the pVAX-ROP27 DNA vaccine offers immune protection against E. tenella infection and could serve as a promising candidate for preventing and controlling chicken coccidiosis.

Effects of diclazuril on the expression of enolase in second-generation merozoites of Eimeria tenella

Eimeria tenella is an obligate intracellular parasite of the chicken cecum; it brings huge economic loss to the chicken industry. Enolase is a multifunctional glycolytic enzyme involved in many processes of parasites, such as infection and migration. In this study, the effect of diclazuril on the expression of enolase in second-generation merozoites of E. tenella (EtENO) was reported. The prokaryotic expression plasmid pET-28a-EtENO was constructed and transformed into Escherichia coli BL21 (DE3). Then, it was subjected to expression under the induction of isopropyl-β-D-1-thiogalactopyranoside. The expressed products were identified and purified. The purified EtENO protein was used for antibody preparation. The EtENO mRNA and protein expression levels were analyzed via real-time PCR and Western blotting. Localization of EtENO on the merozoites was examined by immunofluorescence technique. The mRNA and protein expression levels of EtENO were decreased by 36.3 and 40.36%, respectively, by diclazuril treatment. EtENO distributed in the surface, cytoplasm, and nucleus of the infected/control group. With diclazuril treatment, it was significantly reduced in the surface and cytoplasm and even disappeared in the nucleus of the infected/diclazuril group. These observations suggested that EtENO may play an important role in mechanism of diclazuril anticoccidial action and be a potential drug target for the intervention with E. tenella infection.

A review of Eimeria antigen identification for the development of novel anticoccidial vaccines

Coccidiosis is a major poultry disease which compromises animal welfare and costs the global chicken industry a huge economic loss. As a result, research entailing coccidial control measures is crucial. Coccidiosis is caused by Eimeria parasites that are highly immunogenic. Consequently, a low dosage of the Eimeria parasite supplied by a vaccine will enable the host organism to develop an innate immune response towards the pathogen. The production of traditional live anticoccidial vaccines is limited by their low reproductive index and high production costs, among other factors. Recombinant vaccines overcome these limitations by eliciting undesired contaminants and prevent the reversal of toxoids back to their original toxigenic form. Recombinant vaccines are produced using defined Eimeria antigens and harmless adjuvants. Thus, studies regarding the identification of potent novel Eimeria antigens which stimulate both cell-mediated and humoral immune responses in chickens are essential. Although the prevalence and risk posed by Eimeria have been well established, there is a dearth of information on genetic and antigenic diversity within the field. Therefore, this paper discusses the potential and efficiency of recombinant vaccines as an anticoccidial control measure. Novel protective Eimeria antigens and their antigenic diversity for the production of cheap, easily accessible recombinant vaccines are also reviewed.