Regulation of bovine viral diarrhea virus replication by vesicle-associated membrane protein A

Abstract:

[Background] Bovine viral diarrhea virus (BVDV) is among the important pathogens of calf diarrhea. However, there are few studies on the interaction mechanism between BVDV and host factors, which impedes the prevention and control of BVDV. [Objective] This study aims to explore the effect of vesicle-associated membrane protein A (VAPA) on BVDV replication. [Methods] According to the information of VAPA gene in GenBank, we designed the small guide RNA (sgRNA) targeting VAPA using Benchling and CHOPCHOP, cloned it to lentiCRISPR v2 vector, and then packed the lentivirus. Afterward, Madin-Darby bovine kidney (MDBK) cells were transfected with the lentivirus, followed by puromycin screening for 5 generations and detection of VAPA knockout (KO) by Western Blot. Total RNA was extracted from VAPA KO cells at different time after BVDV infection and then reverse-transcribed into cDNA. Real-time quantitative PCR (RT-qPCR) and immunofluorescence assay (IFA) were used to detect the 5'-untranslated region (UTR) mRNA level and the accumulation of double strand RNA (dsRNA) of BVDV, respectively. Cytopathic effect (CPE) was observed at different time after BVDV infection. Progeny virus titer was calculated with the Reed-Muench method. The same number of VAPA KO and scramble control cells were inoculated and then the living cells were counted at different time after virus infection to detect whether VAPA KO affected the cell viability. [Results] After lentivirus infection and puromycin screening, the results of Western Blot showed that VAPA protein was significantly decreased and thus VAPA KO cells were successfully established. The 5'-UTR mRNA level and dsRNA accumulation in VAPA KO cells infected with BVDV were significantly reduced compared with those of the scramble control cells. The CPE caused by BVDV infection was significantly delayed and attenuated and the titer of progeny virus decreased significantly at 12 h and 36 h and highly significantly at 48 h. The viability of VAPA KO cells was not affected compared with that of the scramble control cells. [Conclusion] VAPA KO can significantly inhibit BVDV replication. Therefore, this study provides an important target for the prevention and control of BVDV.