Brucella is a globally distributed zoonotic disease that can cause abortion and changes in immune function in humans and animals. At present, there is no good treatment plan for Brucella, and animals can only be treated harmlessly once they become ill, resulting in huge economic losses. Therefore, the prevention of Brucella infection is a very crucial step. Although a variety of Brucella vaccines have been widely used, they have varying degrees of shortcomings. For example, some Brucella vaccines have residual virulence, which leads to the emergence of Brucella in animals during the immunization process. Bacillus infection and other conditions occur. To further reduce the toxicity of the Brucella vaccine and enhance its protective effect on animals, this study used Antigen 85A (Ag85A) as a carrier of the Brucella vaccine to fuse with the Brucella S2 vaccine. The results of the study found that the S2-Ag85A oral Brucella vaccine could effectively reduce the toxicity residue of the S2 vaccine, stimulate the mice to produce a better immunogenic response, and effectively activate the expression levels of Brucella heterozygous IgG1 and IgG2a. Experiments have shown that the expression of IFN-γ in the peripheral blood serum and spleen of mice is significantly increased, and the expression levels of IL-1β, TNF-α, and IL-6 are significantly reduced, which may indicate that S2-Ag85A oral Brucella vaccine could induce the expression of IFN-γ, thus downregulating the expression levels of IL-6 and TNF-α in the spleen tissue. The above results indicate that the S2-Ag85A oral vaccine is an effective attenuated vaccine for preventing Brucella infection.

Background Porcine Parvovirus (PPV) are small, enveloped viruses with single stranded genomic DNA. Till now seven genotypes of PPV have been detected worldwide. They are PPV1 to PPV7 with later was first discovered in 2016 in America and then in Asia and European. It has been reported that PPV7 was a co-infector with Porcine Circovirus 2 (PCV2), PCV3 and Porcine reproductive and respiratory syndrome virus (PRRSV). A rapid, sensitive and specific PPV7 detection method that could be applied in poorly equipped laboratory or event in field could be helpful to reveal its distribution and control the spread of this virus. CRISPR/Cas based systems have exhibited outstanding capacities in the detection of pathogenic microorganisms due to the trans-cleavage activities of the Cas proteins.Results Herein, we established a recombinase polymerase amplification (RPA)-CRISPR/Cas12a based rapid viral detection assay for PPV7. Specific RPA primers and five CRISPR RNAs (crRNAs) were designed and synthesized based on the highly conserved region within the NS1 gene of PPV7. The concentration of crRNA and ssDNA were further optimized. Furthermore, we evaluated the sensitivity, specificity, and clinical effectiveness of the RPA-Cas12a based detection assay. The results indicated that this method could be applied for real-time detection. The detection sensitivity of the novel assay was 100 copies/µl, and there were no cross-reactions with other genotypes of PPV, PCV2, PCV3, PRRSV and pseudorabies virus. The RPA-Cas12a based assay could work well in the detection of clinical samples.Conclusions In summary, we developed a visual, sensitive and specific viral diagnostic method based on CRISPR-Cas12a system for PPV7.