Coatomer protein COPƐ, a novel NS1-interacting protein, promotes the replication of Porcine Parvovirus via attenuation of the production of type I interferon

Novel mutation N588 residue in the NS1 protein of feline parvovirus greatly augments viral replication

Feline parvovirus (FPV) infection is highly fatal in felines. NS1, which is a key nonstructural protein of FPV, can inhibit host innate immunity and promote viral replication, which is the main reason for the severe pathogenicity of FPV. However, the mechanism by which the NS1 protein disrupts host immunity and regulates viral replication is still unclear. Here, we identified an FPV M1 strain that is regulated by the NS1 protein and has more pronounced suppression of innate immunity, resulting in robust replication. We found that the neutralization titer of the FPV M1 strain was significantly lower than that of the other strains. Moreover, FPV M1 had powerful replication ability, and the FPV M1-NS1 protein had heightened efficacy in repressing interferon-stimulated genes (ISGs) expression. Subsequently, we constructed an FPV reverse genetic system, which confirmed that the N588 residue of FPV M1-NS1 protein is a key amino acid that bolsters viral proliferation. Recombinant virus containing N588 also had stronger ability to inhibit ISGs, and lower ISGs levels promoted viral replication and reduced the neutralization titer of the positive control serum. Finally, we confirmed that the difference in viral replication was abolished in type I IFN receptor knockout cell lines. In conclusion, our results demonstrate that the N588 residue of the NS1 protein is a critical amino acid that promotes viral proliferation by increasing the inhibition of ISGs expression. These insights provide a reference for studying the relationship between parvovirus-mediated inhibition of host innate immunity and viral replication while facilitating improved FPV vaccine production.IMPORTANCEFPV infection is a viral infectious disease with the highest mortality rate in felines. A universal feature of parvovirus is its ability to inhibit host innate immunity, and its ability to suppress innate immunity is mainly accomplished by the NS1 protein. In the present study, FPV was used as a viral model to explore the mechanism by which the NS1 protein inhibits innate immunity and regulates viral replication. Studies have shown that the FPV-NS1 protein containing the N588 residue strongly inhibits the expression of host ISGs, thereby increasing the viral proliferation titer. In addition, the presence of the N588 residue can increase the proliferation titer of the strain 5- to 10-fold without affecting its virulence and immunogenicity. In conclusion, our findings provide new insights and guidance for studying the mechanisms by which parvoviruses suppress innate immunity and for developing high-yielding FPV vaccines.

For better or worse: crosstalk of parvovirus and host DNA damage response

Parvoviruses are a group of non-enveloped DNA viruses that have a broad spectrum of natural infections, making them important in public health. NS1 is the largest and most complex non-structural protein in the parvovirus genome, which is indispensable in the life cycle of parvovirus and is closely related to viral replication, induction of host cell apoptosis, cycle arrest, DNA damage response (DDR), and other processes. Parvovirus activates and utilizes the DDR pathway to promote viral replication through NS1, thereby increasing pathogenicity to the host cells. Here, we review the latest progress of parvovirus in regulating host cell DDR during the parvovirus lifecycle and discuss the potential of cellular consequences of regulating the DDR pathway, targeting to provide the theoretical basis for further elucidation of the pathogenesis of parvovirus and development of new antiviral drugs.

The Structures and Functions of Parvovirus Capsids and Missing Pieces: the Viral DNA and Its Packaging, Asymmetrical Features, Nonprotein Components, and Receptor or Antibody Binding and Interactions

Parvoviruses are among the smallest and superficially simplest animal viruses, infecting a broad range of hosts, including humans, and causing some deadly infections. In 1990, the first atomic structure of the canine parvovirus (CPV) capsid revealed a 26-nm-diameter T=1 particle made up of two or three versions of a single protein, and packaging about 5,100 nucleotides of single-stranded DNA. Our structural and functional understanding of parvovirus capsids and their ligands has increased as imaging and molecular techniques have advanced, and capsid structures for most groups within the Parvoviridae family have now been determined. Despite those advances, significant questions remain unanswered about the functioning of those viral capsids and their roles in release, transmission, or cellular infection. In addition, the interactions of capsids with host receptors, antibodies, or other biological components are also still incompletely understood. The parvovirus capsid's apparent simplicity likely conceals important functions carried out by small, transient, or asymmetric structures. Here, we highlight some remaining open questions that may need to be answered to provide a more thorough understanding of how these viruses carry out their various functions. The many different members of the family Parvoviridae share a capsid architecture, and while many functions are likely similar, others may differ in detail. Many of those parvoviruses have not been experimentally examined in detail (or at all in some cases), so we, therefore, focus this minireview on the widely studied protoparvoviruses, as well as the most thoroughly investigated examples of adeno-associated viruses.

Chaperonin CCT5 binding with porcine parvovirus NS1 promotes the interaction of NS1 and COPƐ to facilitate viral replication

Porcine parvovirus (PPV) is an important pathogen causing reproductive disorders in first pregnant sows. The non-structure protein NS1 of PPV is a multifunctional protein playing a key role in viral replication. Chaperonin-containing T-complex polypeptide complex (CCT), containing CCT1-CCT8 subunits, belongs to the type II chaperones that interact with proteins to help in folding and maintaining. In this study, CCT5, for the first time, was found to be one of the host interacting proteins of PPV NS1, and CCT5 was directly bound with NS1. Interference of CCT5 expression by specific siRNA and knockout of CCT5 expression by CRISPR/Cas9 suppressed PPV replication, while overexpression of CCT5 promoted PPV replication in PK-15 cells. The interaction of CCT5 and PPV NS1 was dependent on the 36-42 aa motif at the N-terminal end of NS1. More importantly, CCT5 was also found interacting with COPƐ, which has previously been demonstrated to promote PPV replication by regulating type I interferon. Interference and knockout of CCT5 expression significantly reduced the interaction of PPV NS1 and host protein COPƐ, and promoted the IFN-β expression. These results show that CCT5 mediates the interaction of PPV NS1 and COPƐ to regulate viral replication, providing new insight into the mechanism of PPV replication.

Canine parvovirus-2: An Emerging Threat to Young Pets

Canine parvovirus-2 (CPV-2) is a highly contagious and key enteropathogen affecting the canine population around the globe by causing canine parvoviral enteritis (CPVE) and vomition. CPVE is one of the the leading causes of morbidity and mortality in puppies and young dogs. Over the years, five distinct antigenic variants of CPV-2, namely CPV-2a, CPV-2b, new CPV-2a, new CPV-2b, and CPV-2c, have emerged throughout the world. CPV-2 infects a diverse range of wild animals, and the newer variants of CPV-2 have expanded their host range to include felines. Despite the availability of highly specific diagnostics and efficacious vaccines, CPV-2 outbreaks have been reported globally due to the emergence of newer antigenic variants, expansion of the viral host range, and vaccination failures. The present chapter describes the latest information pertaining to virus properties and replication, disease manifestations in animals, and an additional recent updates on diagnostic, prevention and control strategies of CPV-2.

T598 and T601 phosphorylation sites of canine parvovirus NS1 are crucial for viral replication and pathogenicity

Canine parvovirus-2 (CPV-2) is an important pathogen causing severe diseases in dogs and other wild carnivores. Phosphorylation of NS1 may be related to CPV-2 pathogenicity, but the exact mechanism is unclear. Here, we conducted parvovirus disease surveillance in Shaanxi Province of China and 51 fecal swabs were detected to be infected with CPV-2. The 7 CPV-2 strains were identified, all of which belonged to CPV-2c. The complete genome sequence of one of the strains (CPV-2c XY) was cloned into pKQLL plasmid to construct a full-length infectious clone plasmid pX-CPV-2c, which carried a genetic marker. The plasmid pX-CPV-2c was transfected into F81 cells for virus rescue. And the rescued virus, which was designed as X-CPV-2c, showed the similar biological property to parental CPV-2c XY in vitro and in vivo. We further constructed four NS1 phosphorylation site mutant strains (X-CPV-2c^T584A, X-CPV-2c^S592A, X-CPV-2c^T598A/T601A and X-CPV-2c^T617A) on the basis of X-CPV-2c. After the analysis and comparison of biological characteristics, the low pathogenic strain X-CPV-2c^T598A/T601A was further screened out, which emphasized the importance of phosphorylation sites 598 T/601 T for the pathogenicity of CPV-2. Overall, our data indicated that T598 and T601, the C-terminal phosphorylation site of CPV-2 NS1, play important roles in viral pathogenicity and laid the foundation for the development of new attenuated live vaccine vectors.