Preliminary Study Of Nitazoxanide Inhibiting PRRSV

Porcine reproductive and respiratory syndrome virus（PRRSV）belongs to the order nest viruses,arteritis viridae,arteritis virus,arteritis virus,is a pathogen that is harmful to piglets and causes reproductive and respiratory diseases in pigs.It mainly proliferates in the respiratory tract and blood,and the main symptoms are dyspnea,mental depression,reproductive disorders,and blue-purple patches on the skin.At present,there is no specific treatment for this disease,and vaccination has a limited protective effect against variant strains,so the research of antiviral drugs will lay a scientific research and application foundation for the prevention and control of the disease in the future.In this study,it was first verified by in vitro test that the viability of cells was greater than 50%after incubation with Marc-145 cells for 48 and 72 h whe n the concentration of Nitazoxanide（NTZ）was 0.625～10μM,and then it was f ound that 20μM NTZ could significantly reduce the RNA transcription level an d viral titer of PRRSV VR2332,GSWW2015 and GSWW2018 strains.The EC₅₀values of NTZ for PRRSV VR2332 and GSWW2018 were 3.856μM and 1.326μM,respectively,through indirect immunofluorescence test,RT-q PCR and TCI D₅₀.Ribavirin（RBV）is a classic broad-spectrum antiviral drug that has been fou nd to have antagonism when NTZ is used in combination with RBV through a zero-combined interaction（ZIP）model.In summary,NTZ has an in vitro antivira l effect on PRRSV.The absolute real-time RT-q PCR detection method of PRRSV was established to detect animal shedding capacity and tissue viral load.After the plasmid was sequenced correctly,a single peak appeared at Tm=（84.5±0.2）°C,and the linear regression equation of copies and CT value was:CT=-3.6561×log X（copies）+41.816,the correlation coefficient was 0.998,and the amplification efficiency was 106.864%.There was no fluorescence produced in CSFV,PRV and PCV in this detection method,indicating that the specificity of this detection method was good.In the same experiment,the double standard curve detection showed that the two standard curves were in parallel relationship,and the coefficients of variation were 0.312%and 0.363%at 10⁶ and 10² copies,respectively,indicating that the reproducibility of this detection method was good.In summary,the establishment of PRRSV absolute real-time RT-q PCR detection method can be used for subsequent animal testing.After that,the experimental pigs were orally administered with 25 mg/kg NTZ suspension to evaluate the antiviral effect of NTZ on PRRSV.The results showed that oral NTZ could reduce the clinical symptoms of PRRS,increase the body weight by 15%at the 14th day compared with the 0 d,increase the survival rate by 100%compared with the Mock group,reduce the amount of oral and nasal detoxification by more than6.6×10⁴ copies/μL compared with the Mock group,and reduce the viral load of lymph node tissue by more than 1×10⁶ copies/μL compared with the Mock group.In summary,NTZ can be used as one of the clinical drug candidates against PRRSV infection and provide a reference for the treatment of diseases caused by nestiovirus or other members of the arteritis virus family.