Phylogenetic Characteristics of Canine Parvovirus Type 2c Variant Endemic in Shanghai, China

Detection and genetic characterization of circulating canine parvovirus from stray dogs in Shanghai, China

Canine parvovirus (CPV) is the main cause of viral diarrhea in dogs. CPV became a global disease in 1978 and was endemic all over the world. CPV-2 was the first strain to be identified, but with genetic mutations, new genotypes such as CPV-2a/2b/2c/new-2a/new-2b have emerged. In this study, 128 fecal samples of stray dogs suspected of CPV-2 infection were collected from January to March 2021 in Shanghai, China. All samples were screened by PCR and further analyzed by VP2 gene. The positive rate of CPV-2 was 9.4% (12/128), of which 6 CPV-2 isolates were successfully isolated. Phylogenetic tree analysis showed that 4 isolates were CPV-2c genotype and 2 were new-CPV-2b genotype. VP-2 is a key protein that determines the antigenic properties, host range and receptor binding of cpv-2. The results of VP2 amino acid sequence analysis in this study showed that the CPV-2c isolated strain was the same as the previous strains reported in China, including F267Y, Y324I, Q370R and A5G mutations in addition to the typical N426E mutations. Similarly, in addition to the conventional N426D, S297A, F267Y and Y324I mutations, the new CPV-2b isolate also had a new mutation of T440A. This study further confirmed the prevalence of CPV-2c and new-CPV-2b in Shanghai, and also found a new mutation site of new-CPV-2c, which provided a theoretical basis for further enriching the epidemiological data of CPV-2 in Shanghai, as well as the development of vaccines and the prevention and control of the disease.

Molecular epidemiology of canine parvovirus type 2 in Sicily, southern Italy: A geographical island, an epidemiological continuum

Since it emerged as a major dog pathogen, canine parvovirus type 2 (CPV-2) has featured a remarkable genetic and phenotypic heterogeneity, whose biological, epidemiological, and clinical impact is still debated. The continuous monitoring of this pathogen is thus of pivotal importance. In the present study, the molecular epidemiology of CPV-2 in Sicily, southern Italy, has been updated by analysing 215 nearly complete sequences of the capsid protein VP2, obtained from rectal swabs/faeces or tissue samples collected between 2019 and 2022 from 346 dogs with suspected infectious gastrointestinal disease. The presence of the original CPV-2 type (4%) and CPV-2a (9%), CPV-2b (18%), or CPV-2c (69%) variants was documented. Over the years, we observed a decrease in the frequency of CPV-2a/-2b and a rapid increase of CPV-2c frequency, with a progressive replacement of the European lineage of CPV-2c by the Asian lineage. The observed scenario, besides confirming epidemiological relevance of CPV-2, highlights the occurrence of antigenic variant shifts over time, with a trend toward the replacement of CPV-2a, CPV-2b, and the European lineage of CPV-2c by the emerging Asian CPV-2c lineage. The comparison with other Italian and international sequences suggests the occurrence of viral exchange with other Italian regions and different countries, although the directionality of such viral flows could not be often established with confidence. In several instances, potential CPV-2 introductions led to epidemiological dead ends. However, major, long-lasting clades were also identified, supporting successful infection establishment, local spreading, and evolution. These results, besides demonstrating the need for implementing more effective control measures to prevent viral introductions and minimize circulation, stress the relevance of routine monitoring activities as the only tool to effectively understand CPV-2 epidemiology and evolution, and develop adequate countermeasures.

Development of a Novel Canine Parvovirus Vaccine Capable of Stimulating Protective Immunity in Four-Week-Old Puppies in the Face of High Levels of Maternal Antibodies

Many highly effective vaccines have been developed to protect dogs against disease caused by canine parvovirus, but despite this vaccine interference by maternally derived antibodies continues to cause immunisation failure. To help overcome this limitation we have developed a novel, recombinant canine parvovirus type 2c vaccine strain, based on the structural and non-structural elements of an established type 2 vaccine. This novel CPV-2c vaccine strain has unique efficacy in the field, it is able to induce sterilising immunity in naïve animals 3 days after vaccination and is able to overcome very high levels of maternally derived antibodies from 4 weeks of age-thus closing the immunity gap to canine parvovirus infection in young puppies. The vaccine strain, named 630a, has been combined with an established canine distemper virus Onderstepoort vaccine strain to produce a new bivalent vaccine (Nobivac DP PLUS), intended to immunise very young puppies in the face of high levels of maternally derived antibody. Here, we describe the onset of immunity and maternal antibody interference studies that support the unique efficacy of the strain, and present overdose studies in both dogs and cats that demonstrate the vaccine to be safe.

Characterization of the VP2 and NS1 genes from canine parvovirus type 2 (CPV-2) and feline panleukopenia virus (FPV) in Northern China

Canine parvovirus type 2 (CPV-2) and feline panleukopenia virus (FPV) cause severe disease in young animals, pups, and kittens. CPV-2 evolved from FPV by altering the species-specific binding of the viral capsid to the host receptor, i.e., the transferrin receptor (TfR), and CPV-2 genetic variants have been identified by specific VP2 amino acid residues (297, 426). Early studies focused on the main capsid protein VP2; however, there have been limited studies on the non-structural protein NS1. In this study, we identified the genetic variants of clinical samples in dogs and cats in northern China during 2019-2020. The genetic characterization and phylogenetic analyses of VP2 and NS1 gene were also conducted. The results revealed that the CPV-2c was identified as the major genetic variant. One new CPV-2b and two CPV-2c strains were collected from cats. Four mutation sites (60, 630, 443, and 545 amino acid residues) were located in the functional domains of the NS1 protein. The phylogenetic analysis of VP2 and NS1 genes showed that they were clustered by geographical regions and genotypes. The gene mutation rate of CPV-2 was increasing in recent years, resulting in a complex pattern of gene evolution in terms of host preference, geographical selection, and new genetic variants. This study emphasizes that continuous molecular epidemiological surveillance is required to understand the genetic diversity of FPV and CPV-2 strains.

Isolation and identification of a novel canine parvovirus type 2c strain in domestic cats in Dalian, China

Canine parvovirus (CPV) and feline panleukopenia virus (FPV) are highly contagious and cause severe enteric diseases, with high mortality rates in dogs and cats. In the present study, we isolated and identified a novel CPV-2c strain (FPV-DL04 strain) from 18 cats with gastroenteritis symptoms and a positive parvovirus PCR test result in Dalian, China. Molecular characterization, sequence analysis, and phylogeny determination were performed on the VP2 gene of this strain. The results showed that the FPV-DL04 strain had 99.4% homology with the CPV-2c CN/HN1708 strain, and both strains had S297A and A300G key mutation sites. Interestingly, we also found that the DL04 strain has a A5G mutation site, but no F267Y and Y324I mutation sites. This study provided new important findings regarding the evolution of parvovirus infection in domestic cats in China.

Genetic characterization and evolutionary analysis of canine parvovirus in Tangshan, China

Canine parvovirus (CPV) is a major enteric virus of carnivores worldwide that poses a considerable threat to dogs. In this study, we investigated the genetic variation of CPV in Tangshan, China, and the relationships between CPV disease and the vaccination status, age, and gender of dogs. Seventy-seven fecal samples from dogs in Tangshan that tested positive for CPV were obtained for analysis. Twenty-two full-length VP2 gene sequences were successfully amplified. The 22 strains included 17 CPV-2c variants, four new CPV-2a variants, and one new CPV-2b variant. Phylogenetic analysis showed that all of the CPV-2c strains clustered together and were closely related to CPV-2c strains from Asia but distantly related to CPV-2c strains from Europe. Further amino acid sequence analysis showed that, relative to CPV-2c strains from Europe, most of the CPV-2c stains in this study had A5G, F267Y, Y324I, and Q370R mutations. These findings provide a more comprehensive understanding of the variants of CPV circulating in China.

Genomic Divergence Characterization and Quantitative Proteomics Exploration of Type 4 Porcine Astrovirus

Porcine astrovirus (PAstV) has been identified as an important diarrheic pathogen with a broad global distribution. The PAstV is a potential pathogen to human beings and plays a role in public health. Until now, the divergence characteristics and pathogenesis of the PAstV are still not well known. In this study, the PAstV-4 strain PAstV/CH/2022/CM1 was isolated from the diarrheal feces of a piglet in Shanghai, which was identified to be a recombination of PAstV4/JPN (LC201612) and PAstV4/CHN (JX060808). A time tree based on the ORF2 protein of the astrovirus demonstrated that type 2–5 PAstV (PAstV-2 to 5) diverged from type 1 PAstV (PAstV-1) at a point from 1992 to 2000. To better understand the molecular basis of the virus, we sought to explore the host cell response to the PAstV/CH/2022/CM1 infection using proteomics. The results demonstrate that viral infection elicits global protein changes, and that the mitochondria seems to be a primary and an important target in viral infection. Importantly, there was crosstalk between autophagy and apoptosis, in which ATG7 might be the key mediator. In addition, the NOD-like receptor X1 (NLRX1) in the mitochondria was activated and participated in several important antiviral signaling pathways after the PAstV/CH/2022/CM1 infection, which was closely related to mitophagy. The NLRX1 may be a crucial protein for antagonizing a viral infection through autophagy, but this has yet to be validated. In conclusion, the data in this study provides more information for understanding the virus genomic characterization and the potential antiviral targets in a PAstV infection.