Chaperones Hsc70 and Hsp70 play distinct roles in the replication of bocaparvovirus minute virus of canines.

Minute virus of canines (MVC) belongs to the genus Bocaparvovirus (formerly Bocavirus) within the Parvoviridae family and causes serious respiratory and gastrointestinal symptoms in neonatal canines worldwide. A productive viral infection relies on the successful recruitment of host factors for various stages of the viral life cycle. However, little is known about the MVC-host cell interactions. In this study, we identified that two cellular proteins (Hsc70 and Hsp70) interacted with NS1 and VP2 proteins of MVC, and both two domains of Hsc70/Hsp70 were mediated for their interactions. Functional studies revealed that Hsp70 was induced by MVC infection, knockdown of Hsc70 considerably suppressed MVC replication, whereas the replication was dramatically promoted by Hsp70 knockdown. It is interesting that low amounts of overexpressed Hsp70 enhanced viral protein expression and virus production, but high amounts of Hsp70 overexpression weakened them. Upon Hsp70 overexpressing, we observed that the ubiquitination of viral proteins changed with Hsp70 overexpression, and proteasome inhibitor (MG132) restored an accumulation of viral proteins. In addition, we verified that Hsp70 family inhibitors remarkably decreased MVC replication. Overall, we identified Hsc70 and Hsp70 as interactors of MVC NS1 and VP2 proteins and were involved in MVC replication, which may provide novel targets for anti-MVC approach.

Immune escape of bovine parvovirus by VP1 inhibiting IFN-ß production through the RIG-I-like receptor pathway.

OBJECTIVE: The present study aimed to explore if bovine parvovirus (BPV) impacts beta interferon (IFN-ß) production and to reveal further molecular mechanism of BPV immune escape. METHOD: The pCMV-Myc-BPV-VP1 recombinant plasmid was verified with both double-enzyme digestion and sequence. HEK 293 T cells were transfected with this recombinant protein and then infected with the vesicular stomatitis virus (VSV). Expression levels of IFN-ß mRNA were detected using qPCR. RESULTS: The expression level of BPV VP1 mRNA in the pCMV-Myc-BPV-VP1 group was significantly higher than those of the untreated group (UT) and pCMV-Myc vector group. BPV virus copies in bovine turbinate (BT) cells of the BPV-VP1 group were raised (P < 0.05) with an increment of 5.8 × 104. Expression levels of IFN-ß mRNA of the BPV VP1 group in HEK 293 T cells were decreased (P < 0.01). Following treatment of TBK1 and IRF3(5D), IFN-ß expression levels in HEK 293 T cells were depressed. Additionally, expression levels of TBK1, IRF3(5D), MDA5, and MAVS were less than those of the flag empty vector, respectively. CONCLUSION: pCMV-Myc-BPV-VP1 could heighten transcription levels of VP1 protein in BT cells, promote BPV proliferation, and ascend the production of IFN-ß. Overexpression of pCMV-Myc-BPV-VP decreased IFN-ß mRNA expression in HEK 293 T cells and inhibited IFN-ß production induced by TBK1 and IRF3(5D). Furthermore, BPV VP1 obviously declined expression levels of TBK1, IRF3(5D), MDA5, and MAVS in the RIG-I-like receptor (RLR) pathway. Our findings revealed a novel mechanism evolved by BPV VP1 to inhibit type I IFN production and provided a solid scientific basis into the immunosuppression of BPV.

Differential contributions of porcine bocavirus NP1 protein N- and C-terminal regions to its nuclear localization and immune regulation.

Porcine bocavirus (PBoV), a newly identified parvovirus in the family Parvoviridae, has been reported worldwide in swine with post-weaning multisystemic wasting syndrome, respiratory disease or diarrhoea and in asymptomatic swine. NP1 is a protein unique to the genus Bocavirus and its function is not fully understood. In this study, we show that the N-terminal region of PBoV NP1 contains two classical nuclear localization signals (cNLSs) and a non-classical NLS. The N-terminal region also inhibits the promoter activity of IFN-ß and IFN-stimulated response element activity the same as full-length NP1 protein, but the PBoV NP1 C-terminal region does not. PBoV NP1 also induces NFκB activation by increasing the phosphorylation of p65, and we demonstrate that the C-terminal region (aa 168-218) is responsible for the induction of NFκB, although the cNLS region of NP1 enhances this activation. The data suggest that PBoV NP1 contains two functionally independent domains in its N- and C-terminal regions. Thus, the N-terminal region of PBoV NP1 is critical for its nuclear localization and IFN-related promoter inhibition, and the C-terminal region is critical for its induction of NFκB.

Porcine bocavirus: achievements in the past five years.

Porcine bocavirus is a recently discovered virus that infects pigs and is classified within the Bocavirus genus (family Parvoviridae, subfamily Parvovirinae). The viral genome constitutes linear single-stranded DNA and has three open reading frames that encode four proteins: NS1, NP1, VP1, and VP2. There have been more than seven genotypes discovered to date. These genotypes have been classified into three groups based on VP1 sequence. Porcine bocavirus is much more prevalent in piglets that are co-infected with other pathogens than in healthy piglets. The virus can be detected using PCR, loop-mediated isothermal amplification, cell cultures, indirect immunofluorescence, and other molecular virology techniques. Porcine bocavirus has been detected in various samples, including stool, serum, lymph nodes, and tonsils. Because this virus was discovered only five years ago, there are still many unanswered questions that require further research. This review summarizes the current state of knowledge and primary research achievements regarding porcine bocavirus.