Vaccination with transgenic Eimeria tenella expressing Eimeria maxima AMA1 and IMP1 confers partial protection against high-level E. maxima challenge in a broiler model of coccidiosis

Background

Poultry coccidiosis is a parasitic enteric disease with a highly negative impact on chicken production. In-feed chemoprophylaxis remains the primary method of control, but the increasing ineffectiveness of anticoccidial drugs, and potential future restrictions on their use has encouraged the use of commercial live vaccines. Availability of such formulations is constrained by their production, which relies on the use of live chickens. Several experimental approaches have been taken to explore ways to reduce the complexity and cost of current anticoccidial vaccines including the use of live vectors expressing relevant Eimeria proteins. We and others have shown that vaccination with transgenic Eimeria tenella parasites expressing Eimeria maxima Apical Membrane Antigen-1 or Immune Mapped Protein-1 (EmAMA1 and EmIMP1) partially reduces parasite replication after challenge with a low dose of E. maxima oocysts. In the present study, we have reassessed the efficacy of these experimental vaccines using commercial birds reared at high stocking densities and challenged with both low and high doses of E. maxima to evaluate how well they protect chickens against the negative impacts of disease on production parameters.

Methods

Populations of E. tenella parasites expressing EmAMA1 and EmIMP1 were obtained by nucleofection and propagated in chickens. Cobb500 broilers were immunised with increasing doses of transgenic oocysts and challenged two weeks later with E. maxima to quantify the effect of vaccination on parasite replication, local IFN-γ and IL-10 responses (300 oocysts), as well as impacts on intestinal lesions and body weight gain (10,000 oocysts).

Results

Vaccination of chickens with E. tenella expressing EmAMA1, or admixtures of E. tenella expressing EmAMA1 or EmIMP1, was safe and induced partial protection against challenge as measured by E. maxima replication and severity of pathology. Higher levels of protection were observed when both antigens were delivered and was associated with a partial modification of local immune responses against E. maxima, which we hypothesise resulted in more rapid immune recognition of the challenge parasites.

Conclusions

This study offers prospects for future development of multivalent anticoccidial vaccines for commercial chickens. Efforts should now be focused on the discovery of additional antigens for incorporation into such vaccines.

High-Level Expression, Purification and Characterization of A Recombinant Plasmodium vivax Apical Membrane Antigen 1: Implication for vivax Malaria Vaccine Development

Objective

The apical membrane antigen-1 (AMA-1) is considered as a promising candidate for development of a malaria vaccine against Plasmodium parasites. The correct conformation of this protein appears to be necessary for the stimulation of parasite-inhibitory responses, and these responses, in turn, seem to be antibody-mediated. Therefore, in the present investigation, we expressed the Plasmodium vivax AMA-1 (PvAMA-1) ectodomain in Escherichia coli (E. coli), purified it using standard procedures and characterized it to determine its biological activities for it to be used as a potential target for developing a protective and safe vivax malaria vaccine.

Materials and Methods

In this experimental investigation, the ectodomain of PvAMA-1 antigen (GenBank accession no. JX624741) was expressed in the E. coli M15pQE30 expression system and purified with immobilized-metal affinity chromatography. The correct conformation of the recombinant protein was evaluated by Western blotting and indirect immunofluorescence antibody (IFA) test. In addition, the immunogenic properties of PvAMA-1 were evaluated in BALB/c mice with the purified protein emulsified in Freund’s adjuvant.

Results

In the present study, the PvAMA-1 ectodomain was expressed at a high-level (65 mg/L) using a bacterial system. Reduced and non-reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as well as Western blot analysis confirmed the appropriate conformation and folding of PvAMA-1. The evaluation of immunogenic properties of PvAMA-1 showed that both T helper-1 and 2 cells (Th1 and Th2) responses were present in mice after three immunizations and persisted up to one year after the first immunization. Moreover, the antibodies raised against the recombinant PvAMA-1 in injected mice could recognize the native protein localized on P. vivax parasites.

Conclusion

We demonstrate that our recombinant protein had proper conformation and folding. Also, there were common epitopes in the recombinant forms corresponding to native proteins. These results; therefore, indicate that the expressed PvAMA-1 has the potential to be used as a vivax malaria vaccine.

Genetic Variation and Selection of Domain I of the Plasmodium vivax Apical Membrane Antigen-1(AMA-1) Gene in Clinical Isolates from Iran

BACKGROUND

Apical Membrane antigen 1 (AMA-1) is positioned on the surface of merozoite and it may play a role in attack to red blood cells. The main aim of present study was to determine the genetic variation, as well as, to detect of selection at domain I of AMA-1 gene Plasmodium vivax isolates in Iran.

METHODS

Blood samples were collected from 58 patients positive for P. vivax, mono infection and the domain I of AMA-1 gene was amplified by nested PCR and then sequenced.

RESULTS

A total 33 different haplotypes were identified among 58 Iranian sequences. The 23 new haplotypes were determined in this study that was not reported previously in other regions of the world. There were totally observed 36 point mutations at the nucleotide level in the analyzed sequences. Sequences analyses indicated 25 amino acid changes at 20 positions in which 5 sites demonstrated thrimorphic polymorphism and the others were dimorphic in the domain I of the Iranian PvAMA-1 isolates.

CONCLUSION

Our findings indicated relatively high level of allelic diversity at the domain I of PvAMA-1 among P.vivax isolates of Iran. Since, PvAMA-1 is considering as vaccine candidate antigen, these data provide valuable information for the development of a PvAMA-1 based malaria vaccine.