Identification of conserved peptides containing B-cell epitopes of Babesia bovis AMA-1 and their potential as diagnostics candidates

Development of a multi-epitope chimeric vaccine in silico against Babesia bovis, Theileria annulata, and Anaplasma marginale using computational biology tools and reverse vaccinology approach

The three rickettsial parasites- Babesia bovis, Theileria annulata and Anaplasma Marginale are responsible for causing Babesiosis, Theileriosis and Anaplasmosis among cattle. These diseases exist due to spreading of infected ticks. A large number of cattle were found to suffer from mixed infections caused by the three parasites at the same time. Due to these reasons cattle have been devoid of milk production with reduced meat availability. Hence, it is a matter of urgency for the immunity of cattle to exhibit resilience against all three rickettsial parasites. It could be possible if trials are carried out after producing a subunit chimeric vaccine against the rickettsial protozoan parasites and introducing it into the bloodstream of the cattle species. In this paper, we have used the process of reverse vaccinology to conduct a study in which we have developed a multi-epitope subunit chimeric vaccine against three protozoan parasites. We constructed three chimeric vaccine sequences from which only one chimeric vaccine construct was found to be an effective and efficient vaccine which is stable with high solubility and negative allergenicity. Following that, we performed molecular docking of the refined chimeric vaccine construct with Rp-105 and TLR-9. It was observed that the chimeric vaccines interacted with the receptors with high binding energy. Immune simulation was also performed to determine the potentiality of the chimeric vaccine for eliciting an immune response. The best-designed chimeric vaccine construct was then reverse transcribed and adapted for the host E. coli K12 strain which was later inserted into the pET28a (+) vector for the cloning and expression of the vaccine. The study could be a good initiative for the development of an effective chimeric vaccine against bovine parasites.

Evidence of the efficiency of reverse vaccinology against bovine parasites: A systematic review

Reverse vaccinology is a novel vaccine development technology that uses genome and proteome analyses through bioinformatics to select antigenic epitopes capable of eliciting an immunological and protective response through a quick and cheap methodology. However, data on its use in animal health are scant and further research is advocated. Therefore, this systematic review aimed to evaluate the evidence of the efficiency of reverse vaccinology in the search for antigens against bovine parasites, as well as its perspectives and limitations. One hundred seventy-four studies were found, of which 95 were selected for full reading following the PRISMA guidelines and considering all databases. After the last evaluation and reading of the references, only 19 studies were included and evaluated for methodological quality and biases. The studies applied reverse vaccinology to bacteria, protozoa, and ectoparasites that affect cattle, emphasizing on the tick species Rhipicephalus microplus and the protozoa of the genus Babesia that use it as a vector. Most studies evaluated the acquisition of an immune response through ELISA, WB and IFAT analyses to measure predominantly IgG. In addition, many studies did not examine the complete proteome of the parasites and are carried out only in silico, in vitro, or even with unrelated animals, the reason why they were excluded from our systematic review. Due to lack of studies that met the eligibility criteria, in this systematic review we also included studies carried out with different groups and species of parasites, providing a broad overview of the application of this technique in cattle farming. Conversely, this also resulted in variable methodologies, which makes comparison among studies difficult. Despite that, the application of reverse vaccinology in cattle farming has shown promising results in the development of immunological and protective responses in cattle. However, research methodologies need to be improved to reduce biases and obtain reliable results, in addition to clarity of data and methodologies to enable reproducibility.

Immunogenic and diagnostic potential of recombinant apical membrane antigen-1 from Plasmodium malariae

The apical membrane antigen-1 (AMA-1) is a crucial target for malaria management and prevention strategies. While the immunogenicity of AMA-1 has been extensively studied for Plasmodium falciparum and Plasmodium vivax, there is a notable scarcity of information for Plasmodium malariae. In this study, recombinant PmAMA-1 was expressed in Escherichia coli, and its integrity was confirmed via western blotting and indirect immunofluorescence assays. Immunization of BALB/c mice with rPmAMA-1 emulsified in Freund's adjuvant resulted in significantly elevated specific IgG antibodies, predominantly IgG1. The immune response exhibited Th1, Th2, and Th17 phenotypes, with a notable Th1 bias. Antisera from immunized mice effectively recognized native PmAMA-1 on P. malariae. These results suggest that PmAMA-1 is a promising target for both vaccine development and diagnostic applications for P. malariae infections, offering dual preventive and diagnostic benefits in malaria control.

Spherical Body Protein 4 from Babesia bigemina: A Novel Gene That Contains Conserved B-Cell Epitopes and Induces Cross-Reactive Neutralizing Antibodies in Babesia ovata

Bovine babesiosis is a tick-transmitted disease caused by intraerythrocytic protozoan parasites of the genus Babesia. Its main causative agents in the Americas are Babesia bigemina and Babesia bovis, while Babesia ovata affects cattle in Asia. All Babesia species secrete proteins stored in organelles of the apical complex, which are involved in all steps of the invasion process of vertebrate host cells. Unlike other apicomplexans, which have dense granules, babesia parasites instead have large, round intracellular organelles called spherical bodies. Evidence suggests that proteins from these organelles are released during the process of invading red blood cells, where spherical body proteins (SBPs) play an important role in cytoskeleton reorganization. In this study, we characterized the gene that encodes SBP4 in B. bigemina. This gene is transcribed and expressed in the erythrocytic stages of B. bigemina. The sbp4 gene consists of 834 nucleotides without introns that encode a protein of 277 amino acids. In silico analysis predicted a signal peptide that is cleaved at residue 20, producing a 28.88-kDa protein. The presence of a signal peptide and the absence of transmembrane domains suggest that this protein is secreted. Importantly, when cattle were immunized with recombinant B. bigemina SBP4, antibodies identified B. bigemina and B. ovata merozoites according to confocal microscopy observations and were able to neutralize parasite multiplication in vitro for both species. Four peptides with predicted B-cell epitopes were identified to be conserved in 17 different isolates from six countries. Compared with the pre-immunization sera, antibodies against these conserved peptides reduced parasite invasion in vitro by 57%, 44%, 42%, and 38% for peptides 1, 2, 3, and 4, respectively (p < 0.05). Moreover, sera from cattle infected with B. bigemina cattle contained antibodies that recognized the individual peptides. All these results support the concept of spb4 as a new gene in B. bigemina that should be considered a candidate for a vaccine to control bovine babesiosis.

Zambrano-Rodríguez P. The Use of Peptides in Veterinary Serodiagnosis of Infectious Diseases: A Review

Peptides constitute an alternative and interesting option to develop treatments, vaccines, and diagnostic tools as they demonstrate their scope in several health aspects; as proof of this, commercial peptides for humans and animals are available on the market and used daily. This review aimed to know the role of peptides in the field of veterinary diagnosis, and include peptide-based enzyme-linked immunosorbent assay (pELISA), lateral flow devices, and peptide latex agglutination tests that have been developed to detect several pathogens including viruses and bacteria of health and production relevance in domestic animals. Studies in cattle, small ruminants, dogs, cats, poultry, horses, and even aquatic organisms were reviewed. Different studies showed good levels of sensitivity and specificity against their target, moreover, comparisons with commercial kits and official tests were performed which allowed appraising their performance. Chemical synthesis, recombinant DNA technology, and enzymatic synthesis were reviewed as well as their advantages and drawbacks. In addition, we discussed the intrinsic limitations such as the small size or affinity to polystyrene membrane and mention several strategies to overcome these problems. The use of peptides will increase in the coming years and their utility for diagnostic purposes in animals must be evaluated.

Structural and immunological characterization of an epitope within the PAN motif of ectodomain I in Babesia bovis apical membrane antigen 1 for vaccine development

Background

Bovine babesiosis caused by Babesia bovis (B. bovis) has had a significant effect on the mobility and mortality rates of the cattle industry worldwide. Live-attenuated vaccines are currently being used in many endemic countries, but their wide use has been limited for a number of reasons. Although recombinant vaccines have been proposed as an alternative to live vaccines, such vaccines are not commercially available to date. Apical membrane antigen-1 (AMA-1) is one of the leading candidates in the development of a vaccine against diseases caused by apicomplexan parasite species. In Plasmodium falciparum (P. falciparum) AMA-1 (PfAMA-1), several antibodies against epitopes in the plasminogen, apple, and nematode (PAN) motif of PfAMA-1 domain I significantly inhibited parasite growth. Therefore, the purpose of this study was to predict an epitope from the PAN motif of domain I in the B. bovis AMA-1 (BbAMA-1) using a combination of linear and conformational B-cell epitope prediction software. The selected epitope was then bioinformatically analyzed, synthesized as a peptide (sBbAMA-1), and then used to immunize a rabbit. Subsequently, in vitro growth- and the invasion-inhibitory effects of the rabbit antiserum were immunologically characterized.

Results

Our results demonstrated that the predicted BbAMA-1 epitope was located on the surface-exposed α-helix of the PAN motif in domain I at the apex area between residues 181 and 230 with six polymorphic sites. Subsequently, sBbAMA-1 elicited antibodies capable of recognizing the native BbAMA-1 in immunoassays. Furthermore, anti-serum against sBbAMA-1 was immunologically evaluated for its growth- and invasion-inhibitory effects on B. bovis merozoites in vitro. Our results demonstrated that the rabbit anti-sBbAMA-1 serum at a dilution of 1:5 significantly inhibited (p < 0.05) the growth of B. bovis merozoites by approximately 50–70% on days 3 and 4 of cultivation, along with the invasion of merozoites by approximately 60% within 4 h of incubation when compared to the control groups.

Conclusion

Our results indicate that the epitope predicted from the PAN motif of BbAMA-1 domain I is neutralization-sensitive and may serve as a target antigen for vaccine development against bovine babesiosis caused by B. bovis.