The Relationship between B-cell Epitope and Mimotope Sequences

First detection and genetic characterization of canine bufavirus in domestic dogs, Thailand

Canine bufavirus (CBuV) was reported in domestic dogs worldwide. We conducted a survey of canine bufavirus in domestic dogs in Thailand from September 2016 to October 2022. Rectal swab samples (n = 531) were collected from asymptomatic dogs and dogs with gastroenteritis signs. The samples were tested for CBuV using PCR with specific primers to the VP1/VP2 gene, and 9.42% (50/531) was CBuV positive. Our findings showed that CBuVs could be detected in both symptomatic and healthy dogs. The Thai CBuVs were found in dogs from different age groups, with a significant presence in those under 1 year (12.60%) and dogs aged 1-5 years (7.34%) (p < 0.05), suggesting a high prevalence of Thai CBuVs in dogs under 5 years of age. We performed complete genome sequencing (n = 15) and partial VP1/VP2 sequencing (n = 5) of Thai CBuVs. Genetic and phylogenetic analyses showed that whole genomes of Thai CBuVs were closely related to Chinese and Italian CBuVs, suggesting the possible origin of Thai CBuVs. The analysis of VP1 and VP2 genes in Thai CBuVs showed that 18 of them were placed in subgroup A, while only 2 belonged to subgroup B. This study is the first to report the detection and genetic characterization of CBuVs in domestic dogs in Thailand. Additionally, surveillance and genetic characterization of CBuVs in domestic animals should be further investigated on a larger scale to elucidate the dynamic, evolution, and distribution of CBuVs.

Expression and immunogenicity of recombinant porcine epidemic diarrhea virus Nsp9

Porcine epidemic diarrhea virus (PEDV) causes acute diarrhea, vomiting, dehydration, and high mortality in newborn piglets, which leads to significant economic losses. Coronavirus nonstructural protein 9 (Nsp9) is an essential RNA binding protein for coronavirus replication, which renders it a promising candidate for developing antiviral drugs and diagnosis targeting PEDV. In this study, PEDV Nsp9 protein fused with MBP protein and His-tag were expressed and purified in Escherichia coli. Furthermore, immunization of MBP-Nsp9 enhances both humoral and cellular immunity responses as compared with that of His-Nsp9 protein. Finally, the swine immunization showed that Nsp9 protein could stimulate the swine immunity system to carry out humoral immunity, and the generated antibody could inhibit the proliferation of PEDV in Vero cells. Altogether, our data provide direct evidence for the immunogenicity of PEDV Nsp9, which sheds light on the future developments of anti-PEDV drugs and vaccines for PED prevention.

A Quantum Vaccinomics Approach for the Design and Production of MSP4 Chimeric Antigen for the Control of Anaplasma phagocytophilum Infections

Anaplasma phagocytophilum Major surface protein 4 (MSP4) plays a role during infection and multiplication in host neutrophils and tick vector cells. Recently, vaccination trials with the A. phagocytophilum antigen MSP4 in sheep showed only partial protection against pathogen infection. However, in rabbits immunized with MSP4, this recombinant antigen was protective. Differences between rabbit and sheep antibody responses are probably associated with the recognition of non-protective epitopes by IgG of immunized lambs. To address this question, we applied quantum vaccinomics to identify and characterize MSP4 protective epitopes by a microarray epitope mapping using sera from vaccinated rabbits and sheep. The identified candidate protective epitopes or immunological quantum were used for the design and production of a chimeric protective antigen. Inhibition assays of A. phagocytophilum infection in human HL60 and Ixodes scapularis tick ISE6 cells evidenced protection by IgG from sheep and rabbits immunized with the chimeric antigen. These results supported that the design of new chimeric candidate protective antigens using quantum vaccinomics to improve the protective capacity of antigens in multiple hosts.

Epitopes prediction for microcystin-LR by molecular docking

Microcystin-LR (MC-LR) is one of the most worldwide harmful cyanobacterial toxins. A lots of antibodies against MC-LR have been generated and characterized. However, the knowledge about the epitopes of MC-LR was still limited. The objective of this study was to analyze the epitopes of MC-LR and demonstrate the binding mode of MC-LR with its antibody. The variable genes of a mouse hybridoma cell line (Mab5H1-3B3) raised against MC-LR have been cloned and assembled in a single chain variable fragment (scFv), and then soluble expressed in E.coli BL21. Based on the scFv, the IC₅₀ and IC₁₀ for MC-LR were determined to be 7.45 nM and 0.30 nM by competitive ELISA. And the scFv also showed 115% and 112% cross-reactivities to MC-RR and MC-YR, and 59% to MC-LA. By molecular docking, the binding mode between MC-LR and its scFv was demonstrated. A hydrogen bond interaction was observed between the carbonyl group of Adda⁵ residue of MC-LR and its scFv, and the guanidyl group of Arg⁴ residue and phenyl group of Adda⁵ residue of MC-LR were also involved in the interaction. These predicted epitopes were supported by antibody cross-reactivity data. By comparing the antibody informatics of MC-LR scFv with its predicted paratopes, VH-CDR1 was crucial for MC-LR binding, and its specificity could be tuned by engineering in Vκ-CDR1 and Vκ-CDR3. These information would be useful for the hapten design for microcystins or improving the properties of MC-LR scFv in vitro.

Influence of adjuvants on the amount, specificity and functional activity of antibody response to human influenza vaccine in mice

It's been almost a century since immunologists started using adjuvants as tools to develop more effective vaccines. Despite the rising number of adjuvanted vaccines in the last decades, we still lack knowledge of the adjuvants' effects on antibody response. This study was aimed to test the effect of immunizing mice with the human Inactivated Influenza vaccine (IIV), either alone or combined with different widely used adjuvants on the specific antibody response induced. Differential levels of IgM and IgG subclasses were found with the different adjuvants tested. Higher levels of antibodies did not always correspond with a higher efficacy to interfere with the virus infectivity. Differences in neutralization properties are possibly mediated by the specificity of the repertoire of antibodies induced. The repertoire was studied using a phage display 7-mer peptide library to screen for epitopes/mimotopes recognized by serum pools from vaccinated mice. The selected phage clones included peptides that corresponded to conformational mimotopes since they have no homology with lineal sequences of the Influenza strains' proteins. Five peptides were identified as recognized by sera from mice immunized with the IIV vaccine alone, including peptides from the hemagglutinin stalk domain, and by sera from mice immunized with the vaccine plus the different adjuvants employed. Adjuvants elicited a more diverse repertoire of epitope-recognizing antibodies that recognized epitopes of the HA recombinant globular head. Mimotopes were theoretically located at the neutralizing antigenic sites of the globular head of Influenza A H1N1pdm09, Influenza A H3N2, and Influenza B hemagglutinin. This study illustrates how different adjuvants can modify the extent and quality of humoral immunity against the IIV vaccine and the effectiveness of vaccination.

Genetic and phylogenetic analysis of canine bufavirus from Anhui Province, Eastern China

Bufavirus is a novel virus associated with canine gastroenteritis. Three strains of bufavirus were first detected in dog feces collected from Anhui province in Eastern China. The near-complete genome sequences were amplified. Sequence alignment showed 98.3-99.5% homology between the three bufavirus strains and reference strains. Phylogenetic analysis showed the distributed viruses forming a cluster of close relationships. Selective pressure analysis of the VP2 region indicated that the canine bufavirus (CBuV) was mainly subject to negative selection during evolution. The negative selection site was located on the residue of B-cell epitopes, indicating minimal change to the virus's immunogenicity. Since this is the first report of CBuV circulating in Anhui Province, this study will provide further understanding of the phylogenetic and molecular characteristics of CBuV and serve as a reference for prevention and vaccine development.

Advances in In-silico B-cell Epitope Prediction

Identification of B-cell epitopes in target antigens is one of the most crucial steps for epitopebased vaccine development, immunodiagnostic tests, antibody production, and disease diagnosis and therapy. Experimental methods for B-cell epitope mapping are time consuming, costly and labor intensive; in the meantime, various in-silico methods are proposed to predict both linear and conformational B-cell epitopes. The accurate identification of B-cell epitopes presents major challenges for immunoinformaticians. In this paper, we have comprehensively reviewed in-silico methods for B-cell epitope identification. The aim of this review is to stimulate the development of better tools which could improve the identification of B-cell epitopes, and further for the development of therapeutic antibodies and diagnostic tools.