Evaluation of immunogenicity and cross-reactive responses of vaccines prepared from two chimeric serotype O foot-and-mouth disease viruses in pigs and cattle

Foot-and-mouth disease virus 3C protein acts as an anti-inflammatory factor by mediating degradation of TLR4 signaling various molecules via caspase activity

During the early stages of foot-and-mouth disease virus (FMDV) infection, a series of acute inflammatory responses occur in the host. As the disease progresses, these inflammatory responses gradually weaken until the host is nearly recovered. However, the mechanism by which FMDV participates in the negative regulation of host inflammatory responses remains unclear. In this study, we found that FMDV 3C plays a crucial role in inhibiting the inflammatory response by degrading various molecules in the TLR4 signaling pathway. Mechanistically, we discovered that this degradation is mediated by caspase activity, which is activated by 3C protease. Specifically, FMDV 3C targets TLR4, TRIF, p65, IRF3, and TBK1 for degradation through caspase-3, and degrades IRF3 and TBK1 via caspase-8. Notably, FMDV 3C targets TBK1 for degradation through caspase-3, caspase-8, and caspase-9 independently. In conclusion, this is the first report identifying FMDV 3C as an anti-inflammatory factor that mediates the degradation of various molecules to inhibit TLR4 signaling through caspase activity. This study provides a novel insight into explore the relationship between FMDV and inflammation and offers ideas for exploring the biological function of 3C and the pathogenesis of FMDV.

Establishment and Implementation of the Point-of-Care RT-RAA-CRISPR/Cas13a Diagnostic Test for Foot-And-Mouth Disease Virus Serotype O in Pigs

Foot and mouth disease virus (FMDV) is a highly pathogenic virus that mainly infects cloven hooved animals, such as pigs. The establishment of a rapid, sensitive and accurate point-of-care detection method is critical for the timely identification and elimination of infected pigs for controlling this disease. In this study, a RT-RAA-CRISPR/Cas13a method was developed for the detection of FMDV serotype O in pigs. Six pairs of RT-RAA primers were designed based on the conserved gene sequence of FMDV serotype O, and the optimal amplification primers and reaction temperatures were screened. The CRISPR-derived RNA (crRNA) was further designed based on the optimal target band sequence and the most efficient crRNA was screened. The results revealed that FMDV-O-F4/R4 was the optimal primer set, and the optimal temperature for the RT-RAA reaction was 37 °C. Moreover, crRNA4 exhibited the strongest detection signal among the six crRNAs. The established RT-RAA-CRISPR/Cas13a method demonstrated high specificity and no cross-reactivity with other common swine pathogens such as Senecavirus A (SVA), porcine reproductive and respiratory virus (PRRSV), porcine epidemic diarrhea virus (PEDV), porcine circovirus type 2 (PCV2), classical swine fever virus (CSFV), and pseudorabies virus (PRV), additionally, it was observed to be highly sensitive, with a detection limit of 19.1 copies/µL. The repeatability of this method was also observed to be good. This method could produce stable fluorescence and exhibited good repeatability when three independent experiments yielded the same results. A validation test using three types of simulated clinical samples (including swab, tissue, and serum samples) revealed a 100% concordance rate. The detection results could be visualized via a fluorescence reader or lateral flow strips (LFSs). Thus, a highly specific and sensitive RT-RAA-CRISPR/Cas13a detection method was developed and is expected to be applied for the rapid detection of FMDV serotype O in situ.

Foot-and-mouth disease: genomic and proteomic structure, antigenic sites, serotype relationships, immune evasion, recent vaccine development strategies, and future perspectives

Foot-and-mouth disease (FMD) is a highly contagious and transmissible disease that can have significant economic and trade repercussions during outbreaks. In Egypt, despite efforts to mitigate FMD through mandatory immunization, the disease continues to pose a threat due to the high genetic variability and quasi-species nature of the FMD virus (FMDV). Vaccines have been crucial in preventing and managing FMD, and ongoing research focusses on developing next-generation vaccines that could provide universal protection against all FMDV serotypes. This review thoroughly examines the genetic structure of FMDV, including its polyprotein cleavage process and the roles of its structural and non-structural proteins in immune evasion. Additionally, it explores topics such as antigenic sites, specific mutations, and serotype relationships from Egypt and Ethiopia, as well as the structural changes in FMDV serotypes for vaccine development. The review also addresses the challenges associated with creating effective vaccines for controlling FMD, particularly focusing on the epitope-based vaccine. Overall, this review offers valuable insights for researchers seeking to develop effective strategies and vaccines for controlling FMD.

Foot-and-mouth disease in Asia

Foot-and-mouth disease (FMD) is a highly contagious transboundary disease prevalent across the Asian continent, affecting both wild and domestic artiodactyls. The disease is caused by a virus belonging to the Aphthovirus genus of the Picornaviridae family which is categorized into seven serotypes: C, O, A, SAT1, SAT2, SAT3, and Asia1. The virus spreads through direct and indirect contact, including semen, meat, fomites, ingestion, and aerosols. FMD has a severe economic impact due to the high morbidity and mortality, especially in young animals. Prevention of the disease relies on vaccination with the prevalent serotype(s) or the slaughter and destruction of affected animals. This review discusses the prevalence of various FMD virus (FMDV) serotypes across Asia, along with the transmission modes, pathogenesis, immune response, and immune suppression by FMDV. Additionally, the review explores FMD diagnosis, prevention, and control strategies, and highlights future opportunities for research aimed at developing strain-specific viral and bacterial combined vaccines.

Virulence and Immune Evasion Strategies of FMDV: Implications for Vaccine Design

Foot-and-mouth disease (FMD) is globally recognized as a highly economically devastating and prioritized viral disease affecting livestock. Vaccination remains a crucial preventive measure against FMD. The improvement of current vaccine platforms could help control outbreaks, leading to the potential eradication of the disease. In this review, we describe the variances in virulence and immune responses among FMD-susceptible host species, specifically bovines and pigs, highlighting the details of host-pathogen interactions and their impact on the severity of the disease. This knowledge serves as an important foundation for translating our insights into the rational design of vaccines and countermeasure strategies, including the use of interferon as a biotherapeutic agent. Ultimately, in this review, we aim to bridge the gap between our understanding of FMDV biology and the practical approaches to control and potentially eradicate FMD.

A meta-analysis on the potency of foot-and-mouth disease vaccines in different animal models

Whether mice can be used as a foot-and-mouth disease (FMD) model has been debated for a long time. However, the major histocompatibility complex between pigs and mice is very different. In this study, the protective effects of FMD vaccines in different animal models were analyzed by a meta-analysis. The databases PubMed, China Knowledge Infrastructure, EMBASE, and Baidu Academic were searched. For this purpose, we evaluated evidence from 14 studies that included 869 animals with FMD vaccines. A random effects model was used to combine effects using Review Manager 5.4 software. A forest plot showed that the protective effects in pigs were statistically non-significant from those in mice [MH = 0.56, 90% CI (0.20, 1.53), P = 0.26]. The protective effects in pigs were also statistically non-significant from those in guinea pigs [MH = 0.67, 95% CI (0.37, 1.21), P = 0.18] and suckling mice [MH = 1.70, 95% CI (0.10, 28.08), P = 0.71]. Non-inferiority test could provide a hypothesis that the models (mice, suckling mice and guinea pigs) could replace pigs as FMDV vaccine models to test the protective effect of the vaccine. Strict standard procedures should be established to promote the assumption that mice and guinea pigs should replace pigs in vaccine evaluation.

Molecular evolution, diversity, and adaptation of foot-and-mouth disease virus serotype O in Asia

Foot-and-mouth disease (FMD) is highly contagious and affects the economy of many countries worldwide. Serotype O is the most prevalent and is present in many regions of Asia. Lineages O/SEA/Mya-98, O/Middle East-South Asia (ME-SA)/PanAsia, O/Cathay and O/ME-SA/Ind-2001 have been circulating in Asian countries. Low antigenic matching between O/Cathay strains and current vaccine strains makes the disease difficult to control, therefore, analyzing the molecular evolution, diversity, and host tropisms of FMDV Serotype O in Asia may be helpful. Our results indicate that Cathay, ME-SA, and SEA are the predominant topotypes of FMDV serotype O circulating in Asia in recent years. Cathay topotype FMDV evolves at a higher rate compared with ME-SA and SEA topotypes. From 2011 onwards, the genetic diversity of the Cathay topotype has increased substantially, while large reductions were found in the genetic diversity of both ME-SA and SEA topotypes, suggesting a trend that infections sustained by the Cathay topotype were becoming a more severe epidemic in recent years. Analyzing the distributions of host species through time in the dataset, we found that the O/Cathay topotype was characterized by a highly swine-adapted tropism in contrast with a distinct host preference for O/ME-SA. The O/SEA topotype strains identified in Asia were isolated mainly from cattle until 2010. It is worth noting that there may be a fine-tuned tropism of the SEA topotype viruses for host species. To further explore the potential molecular mechanism of host tropism divergence, we analyzed the distribution of structure variations on the whole genome. Our findings suggest that deletions in the PK region may reflect a common pattern of altering the host range of serotype O FMDVs. In addition, the divergence of host tropism may be due to accumulated structural variations across the viral genome, rather than a single indel mutation.

Evaluation of Vaccine Strains Developed for Efficient, Broad-Range Protection against Foot-and-Mouth Disease Type O

Foot-and-mouth disease (FMD) type O includes 11 genetic topotypes. The Southeast Asia (SEA), Middle East-South Asia (ME-SA), and Cathay topotypes belong to FMD type O and occur frequently in Asia. Therefore, it is necessary to develop a potent vaccine strain with a broad antigenic coverage in order to provide complete protection against these three topotypes. In this study, an experimental vaccine was produced using chimeric vaccine strains (JC-VP1 or PA2-VP1) that contained VP4, VP2, and VP3 of the ME-SA topotype (O Manisa) and VP1 of the SEA topotype (Mya98 lineage; O/SKR/Jincheon/2014) or ME-SA topotype (PanAsia2 lineage; O/PAK/44). Mice were immunized with the experimental vaccines, and they were fully protected against the three topotypes. The neutralizing antibody titers of PA2-VP1 were significantly higher than those of JC-VP1 in the early vaccination phase in pigs. Here, we confirmed complete protection in pigs vaccinated with JC-VP1 or PA2-VP1, when challenged against the SEA (O/SKR/Jincheon/2014), ME-SA (O/SKR/Boeun/2017) and Cathay (O/Taiwan/97) topotype viruses, with moderately higher protection provided by PA2-VP1 than by JC-VP1.