For a better understanding of classical swine fever (CSF) pathogenesis, a transcriptomic analysis was performed using porcine bone marrow (BM)-derived antigen-presenting cells (APCs) infected ex vivo with two different cDNA-derived classical swine fever virus (CSFV) strains, the low-virulence Pinar de Rio (vPdR-36U) or the lethal vPdR-H₃₀K-5U. The transcriptomic profile of vPdR-36U- or vPdR-H₃₀K-5U-infected versus noninfected cells revealed 946 and 2643 differentially expressed genes (DEGs), respectively. The upregulation of ISG15, CXCL-10, ADAM8, and CSF1 was found after infection with vPdR-36U, which could contribute to the generation of mild CSF forms. In contrast, cells infected with the lethal vPdR-H₃₀K-5U overexpressed the immune checkpoint molecules PD-L1, CD276, and LAG3, which are involved in T-cell exhaustion and could be associated with adaptive immunity impairment. vPdR-H₃₀K-5U also induced increased expression of PPBP, IL-8, IL-6, ECE1, and Rab27b, which are mediators of inflammatory responses that can be involved in cytokine storms. The TNF signaling pathway, which is related to the activation and proliferation of different subsets of immune cells, including CD4+ T cells, was notably upregulated in response to the low-pathogenicity virus. The Th17, Th1, and Th2 differentiation pathways were downregulated by the highly pathogenic virus only, supporting the role of T-cell-mediated immunity in protecting against CSFV.

The increasing spread of African swine fever (ASF) in recent years and the presence of classical swine fever (CSF) subclinical forms in endemic countries suggests that the possibility of coinfection with ASF virus (ASFV) and CSF virus (CSFV) in pigs cannot be ruled out in areas where both diseases are prevalent. Thus, rapid and reliable diagnosis through molecular testing is essential for the timely implementation of control measures to prevent the spread of these devastating swine diseases. Here, we have coupled two of the most validated PCR assays for the detection of CSFV and ASFV in a single reaction tube. The combination of the two tests for the detection of two target nucleic acids did not affect the analytical sensitivity, and the duplex RT-qPCR assay was comparable with the standard molecular techniques. The detection limits for CSFV RNA and ASFV DNA were 0.12 TCID₅₀/reaction and 0.25 TCID₅₀/reaction, respectively. The test showed high repeatability and reproducibility, the coefficient of variation was below 2%, and excellent performance was demonstrated in clinical samples. The duplex assay shows great potential to become a robust diagnostic tool for the rapid and reliable detection and differentiation of CSFV and ASFV in areas where both viruses may be circulating.

African swine fever (ASF) is a disease that affects both domestic and wild swine. It was recently reported in the Dominican Republic and Haiti (2021), representing a substantial risk to America. The goal of this study was to produce a truncated form of the ASF-p72 recombinant protein based on the ASF strain genotype II (Georgia 2017) as well as to develop and validate a sensitive and specific ASF indirect-ELISA (iELISA) for early detection of ASF. The truncated ASF-p72 recombinant protein was successfully expressed in E. coli BL21/DE3 cells using the pET-SUMO plasmid. Bioinformatics analysis showed 100% homology among the new isolates of ASFV from genotype II. The ASF-p72-truncated protein was used to develop an iELISA, which had a high sensitivity (88%) and strong specificity (97%); the concordance index kappa was K = 0.872, indicating nearly perfect agreement compared to the WOAH confirmatory immunoperoxidase test. The validation results utilizing the reference sera panel from the OIE-ASF Reference Laboratory show the excellent detection capabilities of ASF antibodies up to a 1:1000 serum dilution. The inter-assay coefficient of variation (CV 10.4%) and intra-assay CV (2.8%) data show that the assay is precise and reproducible. This biotechnology advancement can be used to conduct future epidemiological research for ASF surveillance in ASF-free American countries.

Background/Objectives: Classical swine fever (CSF) continues to challenge global eradication efforts, particularly in endemic regions, where pregnant sows face heightened risks of vertical transmission following exposure to CSFV. Methods: This study evaluates the early protective efficacy of FlagT4G, a novel live attenuated DIVA-compatible vaccine. Pregnant sows were vaccinated at mid-gestation and challenged 14 days later with a highly virulent CSFV strain. Results: FlagT4G conferred complete clinical protection, preventing both maternal viremia and transplacental transmission. No CSFV RNA, specific antibodies, or IFN-α were detected in fetal samples from vaccinated animals. In contrast, unvaccinated sows exhibited clinical signs, high viral loads, and widespread fetal infection. Interestingly, early protection was observed even in the absence of strong humoral responses in some vaccinated sows, suggesting a potential role for innate or T-cell-mediated immunity in conferring rapid protection. Conclusions: The demonstrated efficacy of FlagT4G within two weeks of vaccination underscores its feasibility for integration into emergency vaccination programs. Its DIVA compatibility and ability to induce early fetal protection against highly virulent CSFV strains position it as a promising tool for CSF control and eradication strategies.

The transplacental transmission of CSFV and the resulting persistent congenital infection in newborn piglets have been abundantly discussed in pregnant sows suffering from virus infection. Importantly, the availability of safe commercial vaccines with proven efficacy to prevent the generation of congenital and postnatal persistent infections in pregnant sows are critical tools for controlling the disease in CSF endemic areas. Here, we demonstrate the high efficacy of a single dose of the recombinant FlagT4G vaccine to provide solid protection in pregnant sows against transplacental transmission of a highly virulent CSFV. Pregnant sows vaccinated with FlagT4G at 44 days of gestation elicited a strong CSFV-specific antibody response, with neutralizing antibody levels above those required for protection against CSFV. Importantly, after the challenge with a highly virulent CSFV, all foetuses from FlagT4G-vaccinated sows lacked CSF macroscopic lesions and showed a complete absence of the challenge virus in their internal organs at day 79 of gestation. Therefore, pregnant sows safely vaccinated with FlagT4G without affecting reproductive efficacy are efficaciously protected, along with their foetuses, against the infection and disease caused by a CSFV virulent field strain.

Classical swine fever (CSF) is a highly contagious transboundary animal disease that causes major economic losses to the global swine industry and remains notifiable to the World Organisation for Animal Health (WOAH). Handling and transport of infectious classical swine fever virus (CSFV)-positive samples require biosafety level 3 (BSL-3) containment, limiting diagnostic capacity and interlaboratory exchange in many regions. In this study, we evaluated the efficacy of PrimeStore^® Molecular Transport Medium (PS-MTM) for eliminating detectable CSFV infectivity while preserving viral ribonucleic acid (RNA) detectability for downstream molecular detection. Validation assays were performed using the CSFV Alfort/187 reference strain and clinical samples collected from pigs experimentally infected with the Catalonia01 and Margarita CSFV strains. Residual infectivity was assessed by virus isolation, whereas viral RNA detection and stability were evaluated using the WOAH-recommended real-time reverse transcription quantitative polymerase chain reaction(RT-qPCR) assay. Following PS-MTM treatment, no residual infectivity was detected in either cell culture-derived virus stocks or clinical samples, including extensive replicate testing and three subsequent blind passages. RT-qPCR analyses confirmed preservation and stability of detectable CSFV RNA for at least 60 days under the storage conditions evaluated, including refrigerated storage and room temperature storage for Catalonia01-derived samples. Overall, these findings demonstrate that PS-MTM eliminates detectable CSFV infectivity while preserving viral RNA for molecular diagnosis. The implementation of PS-MTM may facilitate safer handling, transport, and interlaboratory exchange of CSFV-positive samples, contributing to improved biosafety, diagnostic harmonization, and global surveillance capacity for this transboundary animal disease.