Genetic characterization of the complete genome of a mutant canine parvovirus isolated in China

Molecular characterisation of the current high prevalence of the new CPV-2c variants in the Southern Vietnamese dogs signifies a widespread in the worldwide dog population

BACKGROUND

Canine parvovirus type 2 (CPV-2) is known as the primary etiological agent cause of acute gastroenteritis, myocarditis and death of canids worldwide. In Vietnam, although CPV-2 infection and its outbreaks are the most important risk factors of the canine's health concern, lack of available information about the molecular epidemiology of the CPV-2.

OBJECTIVES

In this study, the complete coding sequences of 10 CPV-2 strains collected from dogs vaccinated with CPV-2 vaccination were analysed to better understand the genomic characteristics of the current circulating CPV-2 in Vietnam.

METHODS

Ten CPV-specific PCR-positive rectal swab samples were collected from dogs with acute symptoms of haemorrhagic diarrhoea and vomiting in Vietnam in 2019. The complete coding sequences of these CPV strains were analysed to determine their phylogeny and genetic relationship with other available CPV strains globally.

RESULTS

Analysis of the VP2 gene sequences demonstrated that the studied strains belonged to the new CPV-2c variants with the unique mutations at amino acids 5^Ala-Gly and 447^Iso-Met . Phylogenetic tree analysis indicated that the studied strains share a common evolutionary origin with the current CPV-2c strains circulating in dogs in Asia countries, including China, Thailand, Taiwan and Mongolia, in recent years. Low sequence identity between the studied strains and commercial vaccine strains was observed.

CONCLUSIONS

This study provides deep insights into the molecular characteristics, genetic diversity, and evolution of circulating CPV-2 strains in Vietnam. We recommend more studies to estimate the effectiveness of the CPV vaccine and the need to continue developing other effective vaccination essential to better control the widespread of these new CPV-2 variants.

Viral Metagenomic Analysis of the Fecal Samples in Domestic Dogs (Canis lupus familiaris)

Canine diarrhea is a common intestinal illness that is usually caused by viruses, bacteria, and parasites, and canine diarrhea may induce morbidity and mortality of domestic dogs if treated improperly. Recently, viral metagenomics was applied to investigate the signatures of the enteric virome in mammals. In this research, the characteristics of the gut virome in healthy dogs and dogs with diarrhea were analyzed and compared using viral metagenomics. The alpha diversity analysis indicated that the richness and diversity of the gut virome in the dogs with diarrhea were much higher than the healthy dogs, while the beta diversity analysis revealed that the gut virome of the two groups was quite different. At the family level, the predominant viruses in the canine gut virome were certified to be Microviridae, Parvoviridae, Siphoviridae, Inoviridae, Podoviridae, Myoviridae, and others. At the genus level, the predominant viruses in the canine gut virome were certified to be Protoparvovirus, Inovirus, Chlamydiamicrovirus, Lambdavirus, Dependoparvovirus, Lightbulbvirus, Kostyavirus, Punavirus, Lederbergvirus, Fibrovirus, Peduovirus, and others. However, the viral communities between the two groups differed significantly. The unique viral taxa identified in the healthy dogs group were Chlamydiamicrovirus and Lightbulbvirus, while the unique viral taxa identified in the dogs with diarrhea group were Inovirus, Protoparvovirus, Lambdavirus, Dependoparvovirus, Kostyavirus, Punavirus, and other viruses. Phylogenetic analysis based on the near-complete genome sequences showed that the CPV strains collected in this study together with other CPV Chinese isolates clustered into a separate branch, while the identified CAV-2 strain D5-8081 and AAV-5 strain AAV-D5 were both the first near-complete genome sequences in China. Moreover, the predicted bacterial hosts of phages were certified to be Campylobacter, Escherichia, Salmonella, Pseudomonas, Acinetobacter, Moraxella, Mediterraneibacter, and other commensal microbiota. In conclusion, the enteric virome of the healthy dogs group and the dogs with diarrhea group was investigated and compared using viral metagenomics, and the viral communities might influence canine health and disease by interacting with the commensal gut microbiome.

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.

A multiplex nanoparticle-assisted polymerase chain reaction assay for detecting three canine epidemic viruses using a dual priming oligonucleotide system

A rapid and accurate diagnosis of mixed viral infections is important for providing timely therapeutic interventions. The aim of this study was to develop a highly sensitive and specific method for the simultaneous detection of canine distemper virus (CDV), canine parvovirus (CPV) and canine coronavirus (CCV) in mixed infections by combining the high specificity of a dual priming oligonucleotide (DPO) primer system with the high sensitivity of a nanoparticle-assisted PCR (nanoPCR) assay. Under the optimised assay conditions, the multiplex DPO-nanoPCR assay developed using DPO primers was 100-fold more sensitive than the multiplex PCR assay using conventional primers. The detection limits of the multiplex DPO-nanoPCR assay for the recombinant plasmids containing the cloned CDV, CPV and CCV target sequences were 5.4 × 10², 6.5 × 10² and 1.6 × 10² copies in a 25 μL assay, respectively. No cross-reaction with other canine viruses was observed. This is the first reported use of a multiplex nanoPCR assay with the DPO primer system for the simultaneous detection of CDV, CPV and CCV in mixed infections. The high sensitivity and specificity of the assay indicated its potential for use in clinical diagnosis and field surveillance of animal epidemics.

Dynamic evolution of canine parvovirus in Thailand

Background and Aim:

According to the previous study, the circulating canine parvovirus (CPV) in Thailand is 2a and 2b. Nowadays, CPV mutants, including CPV-2c, have been identified in many parts of the world. This study aimed to investigate the genetic diversity of the circulating CPV in Thailand.

Materials and Methods:

Eighty-five CPV-positive fecal samples were obtained from dogs with either acute hemorrhagic diarrhea or diarrhea. The complete VP2 gene of these samples was amplified using VP2 specific primers and polymerase chain reaction (PCR). The obtained full-length VP2 sequences were analyzed and a phylogenetic tree was constructed.

Results:

Sixty and 25 CPV-positive fecal samples were collected in 2010 and 2018, respectively. Thirty-four samples were new CPV-2a and 31 samples were new CPV-2b due to amino acids substitution at position 297 (Ser-Ala). In 2018, 5 new CPV-2a, 19 CPV-2c, and 1 feline panleukopenia virus (FPV) were found, but no new CPV-2b was detected. Moreover, most of the CPV in this study had amino acids mutations at positions 324 and 440. The phylogenetic construction demonstrated the close relationship between the current new CPV-2a with the previous CPV-2a reported from Thailand, China, Uruguay, Vietnam, Singapore, and India. Interestingly, the current new CPV-2b in this study was not closely related to the previous CPV-2b reported in Thailand. The CPV-2c in this study was closer to Asian CPV-2c and further from either European or South America CPV-2c. Interestingly, FPV was identified in a diarrhea dog.

Conclusion:

The evolution of CPV in Thailand is very dynamic. Thus, it is important to monitor for CPV mutants and especially the clinical signs relating to these mutants to conduct surveillance for the emergence of new highly pathogenic CPV in the future.

Spreading of canine parvovirus type 2c mutants of Asian origin in southern Italy

Canine parvovirus type 2 (CPV‐2) emerged as dog pathogen in the late 1970s, causing severe and often fatal epizootics of gastroenteritis in the canine population worldwide. Although to date CPV‐2 is circulating in all continents, most of the current studies have analysed the amino acid changes accounted in the VP2 gene sequence, with limited information on virus introductions from other countries. The aim of this study was to analyse the genetic features of CPV‐2c strains currently spreading in Italy. Swabs and tissue samples were collected from dogs suspected of CPV infection. The nearly complete genome sequence from the CPV‐positive samples was obtained. The co‐circulation of two different but related CPV‐2c strains, with amino acid changes characteristic of CPV strains of Asian origin (NS1: 60V, 544F, 545F, 630P – NS2: 60V, 151N, 152V ‐ VP2: 5A/G, 267Y, 297A, 324I, 370R), were observed. The phylogenetic analyses inferred from the NS1 and VP2 gene sequences confirmed the relationship with Asian CPV‐2c strains. This study reports the spread of novel CPV‐2c mutants in Italy and supports further studies to evaluate the coexistence of genetically divergent CPV strains in the same geographical environment.

A divergent canine parvovirus type 2c (CPV-2c) isolate circulating in China

The variability and the intrinsically high mutation rate of canine parvovirus type 2(CPV-2) increased the diversity of CPV-2 in canine populations. Since the first occurrence of CPV-2, three antigenic variants (2a, 2b and 2c) were detected and distributed worldwide. CPV-2c infection has been detected and increasingly reported in China. Here, a CPV-2c strain CPV-SH1516 was isolated and its complete genome sequence was first characterized. Compared with other CPV-2c isolates, CPV-2c isolates from China continued to evolve into divergent CPV-2c variants with specific unique amino acid substitutions under purifying selection. Emergence of CPV-2c isolates from China was driven by the unique gradual point mutations in key sites of VP2 rather than introduction from outside China. Combining sequence comparison with phylogenetic analysis based on the amino acid sequences of VP2, the vast majority of CPV-2c isolates from China formed a monophyletic cluster and CPV-SH1516 was a representative isolate of CPV-2c circulating in China. Overall, our study provides valuable insight into the evolutionary mechanism of CPV-2c.

New variants of canine parvovirus in dogs in southern Brazil

Carnivore protoparvovirus 1 (canine parvovirus 2, CPV-2) has undergone a rapid evolution through mutations in the capsid protein VP2, giving rise to variants associated with unique clinicopathological and immunological features. VP2 is a major capsid protein involved in key steps of virus biology, including interactions with cellular receptors and with the immune system. This study analyzed the complete VP2 coding sequence of 38 CPV-2 isolates obtained from dogs with clinical parvovirosis in southern Brazil. Amplicons encompassing the whole VP2 coding region were subjected to nucleotide sequencing, and predicted amino acid sequences were analyzed to identify molecular markers of viral variants. Viral variants were classified as CPV-2a, -2b or -2c based on the presence of the amino acid Asn, Asp or Glu, respectively, at VP2 residue 426. Amino acid sequence analysis identified 20 CPV-2c and four CPV-2b isolates. Eleven viruses were identified as New CPV-2a, two as New CPV-2b, and one resembled the original CPV-2 and was designated CPV-2-like. In addition to the mutation at amino acid 426 of VP2, new 2a/2b variants containing a Ser297Ala mutation at residue 297 were identified. CPV-2-like samples contained some mutations that were also present in the original CPV-2 isolate, including as Leu, Thr, Ala and Asp at residues 87, 101, 300 and 305, respectively. The New CPV-2a isolates had three additional mutations (Phe267Tyr, Tyr324Ile and Thr440Ala) associated with selective pressure and development of disease in vaccinated dogs. The resemblance of the CPV-2-like isolate to CPV-2 suggests reemergence of CPV-2 and/or evolution from vaccine strains. Phylogenetic analysis grouped the variants with their respective reference strains, in general, according to amino acid changes. These results demonstrate the high VP2 diversity of CPV circulating in dogs in southern Brazil and indicate the emergence of new viral variants that differ markedly from the current vaccine strains.