Identification and characterization of Eimeria tenella EtTrx1 protein

Molecular characterization and immune protective efficacy of 3 Eimeria tenella antigens

Avian coccidiosis caused by Eimeria is a serious parasitic disease that poses a threat to the poultry industry. Currently, prevention and treatment mainly rely on the administration of anticoccidials and live oocyst vaccines. However, the prevalence of drug resistance and the inherent limitations of live vaccines have driven the development of novel vaccines. In this study, the surface protein (Et-SAG14), a previously annotated rhoptry protein (Eten5-B), and a gametocyte phosphoglucomutase (Et-PGM1) were characterized and the vaccine potential of the recombinant proteins were evaluated. Et-SAG14 was dispersed in the form of particles in the sporozoite and merozoite stages, whereas Et-PGM1 was distributed in the apical part of the sporozoite and merozoite stages. The previously annotated rhoptry Eten5-B was found not to be located in the rhoptry but distributed in the cytoplasm of sporozoites and merozoites. Immunization with rEten5-B significantly elevated host interferon gamma (IFN-γ) and interleukin 10 (IL-10) transcript levels and exhibited moderate anticoccidial effects with an anticoccidial index (ACI) of 161. Unexpectedly, both recombinant Et-SAG14 and Et-PGM1 immunization significantly reduced host IFN-γ and IL-10 transcription levels, and did not show protection against E. tenella challenge (ACI < 80). These results suggest that the rEten5-B protein can trigger immune protection against E. tenella and may be a potential and effective subunit vaccine for the control of coccidiosis in poultry.

Vaccination Against Poultry Parasites

The complexity of parasites and their life cycles makes vaccination against parasitic diseases challenging. This review highlights this by discussing vaccination against four relevant parasites of poultry. Coccidia, i.e., Eimeria spp., are the most important parasites in poultry production, causing multiple billions of dollars of damage worldwide. Due to the trend of antibiotic-free broiler production, use of anticoccidia vaccines in broilers is becoming much more important. As of now, only live vaccines are on the market, almost all of which must be produced in birds. In addition, these live vaccines require extra care in the management of flocks to provide adequate protection and prevent the vaccines from causing damage. Considerable efforts to develop recombinant vaccines and related work to understand the immune response against coccidia have not yet resulted in an alternative. Leucozytozoon caulleryi is a blood parasite that is prevalent in East and South Asia. It is the only poultry parasite for which a recombinant vaccine has been developed and brought to market. Histomonas meleagridis causes typhlohepatitis in chickens and turkeys. The systemic immune response after intramuscular vaccination with inactivated parasites is not protective. The parasite can be grown and attenuated in vitro, but only together with bacteria. This and the necessary intracloacal application make the use of live vaccines difficult. So far, there have been no attempts to develop a recombinant vaccine against H. meleagridis. Inactivated vaccines inducing antibodies against the poultry red mite Dermanyssus gallinae have the potential to control infestations with this parasite. Potential antigens for recombinant vaccines have been identified, but the use of whole-mite extracts yields superior results. In conclusion, while every parasite is unique, development of vaccines against them shares common problems, namely the difficulties of propagating them in vitro and the identification of protective antigens that might be used in recombinant vaccines.

Analysis of codon usage bias of thioredoxin in apicomplexan protozoa

BACKGROUND

Apicomplexan protozoa are a diverse group of obligate intracellular parasites causing many diseases that affect humans and animals, such as malaria, toxoplasmosis, and cryptosporidiosis. Apicomplexan protozoa possess unique thioredoxins (Trxs) that have been shown to regulate various cellular processes including metabolic redox regulation, parasite survival, and host immune evasion. However, it is still unknown how synonymous codons are used by apicomplexan protozoa Trxs.

METHODS

Codon usage bias (CUB) is the unequal usage of synonymous codons during translation which leads to the over- or underrepresentation of certain nucleotide patterns. This imbalance in CUB can impact a variety of cellular processes including protein expression levels and genetic variation. This study analyzed the CUB of 32 Trx coding sequences (CDS) from 11 apicomplexan protozoa.

RESULTS

The results showed that both codon base composition and relative synonymous codon usage (RSCU) analysis revealed that AT-ended codons were more frequently used in Cryptosporidium spp. and Plasmodium spp., while the Eimeria spp., Babesia spp., Hammondia hammondi, Neospora caninum, and Toxoplasma gondii tended to end in G/C. The average effective number of codon (ENC) value of these apicomplexan protozoa is 46.59, which is > 35, indicating a weak codon preference among apicomplexan protozoa Trxs. Furthermore, the correlation analysis among codon base composition (GC1, GC2, GC3, GCs), codon adaptation index (CAI), codon bias index (CBI), frequency of optimal codons (FOP), ENC, general average hydropathicity (GRAVY), aromaticity (AROMO), length of synonymous codons (L_sym), and length of amino acids (L_aa) indicated the influence of base composition and codon usage indices on CUB. Additionally, the neutrality plot analysis, PR2-bias plot analysis, and ENC-GC3 plot analysis further demonstrated that natural selection plays an important role in apicomplexan protozoa Trxs codon bias.

CONCLUSIONS

In conclusion, this study increased the understanding of codon usage characteristics and genetic evolution of apicomplexan protozoa Trxs, which expanded new ideas for vaccine and drug research.

Characterization of the novel glucose-methanol-choline (GMC) oxidoreductase EnOXIO1 in Eimeria necatrix

Eimeria species are intracellular obligate parasites, among the most common pathogens affecting the intensive poultry industry. Oxidoreductases are members of a class of proteins with redox activity and are widely found in apicomplexan protozoans. However, there have been few reports related to Eimeria species. In this study, total RNA was extracted from the gametocytes of E. necatrix Yangzhou strain to amplify the EnOXIO1 gene using reverse-transcription polymerase chain reaction. After cloning and sequence analysis, the prokaryotic expression vector pET-28a(+)-EnOXIO1 was constructed and transformed into Escherichia coli BL21(DE3), and the recombinant protein rEnOXIO1 was expressed by induction with isopropyl ß-D-1-thiogalactopyranoside. The full length EnOXIO1 gene was 2535 bp encoding 844 amino acids, and the EnOXIO1 protein had a molecular weight of about 100 kDa and was mainly expressed in inclusion bodies. Western blot analysis indicated that the rEnOXIO1 protein had good antigenicity and cross-reactivity and was specifically recognized by a 6 ×HIS labeled monoclonal antibody, mouse anti-recombinant protein polyclonal antibody, and recovery serum from chickens infected with E. necatrix, E. acervulina, and E. tenella sporulated oocysts. The results of laser confocal immunofluorescence localization showed that the EnOXIO1 protein was mainly located on the wall-forming bodies in gametocytes and played an important role in the formation of the oocyst wall. Quantitative PCR analysis revealed that transcript levels of EnOXIO1 were highest in the gametocyte stage. Protein expression levels of EnOXIO1 were higher in the gametocyte stage than in other developmental stages according to western blot analysis. Vaccination of chickens against E. necatrix was achieved with recombinant protein rEnOXIO1, which triggered humoral immunity and antibody production, increased average body weight gain, reduced oocyst output and alleviated lesions after E. necatrix infection. The highest ACI value (172.36) was observed in chickens that received 200 μg rEnOXIO1 compared with other immunization groups.