Molecular characteristics and genetic evolutionary analyses of circulating parvoviruses derived from cats in Beijing

Genetic characterization of the parvovirus full-length VP2 gene in domestic cats in Brazil

Feline parvovirus (FPV) and canine parvovirus (CPV) are over 98% identical in their DNA sequences, and the new variants of CPV (2a/2b/2c) have gained the ability to infect and replicate in cats. The aim of this study was to determine the genetic diversity in the VP2 gene of parvovirus strains circulating in domestic cats in Brazil during a 10-year period (2008-2017). For parvovirus screening, specific PCR was performed, and 25 (34.7%) of 72 cats tested positive. The PCR-positive samples were further subjected to full-length VP2 sequencing (1755 bp), and eight sequences (36%) were characterized as FPV, seven (28%) as CPV-2a and (32%) nine (36%) as CPV-2b. One sequence (RJ1085/11) showing typical CPV amino acid (aa) at residues 80 R, 93 N, 103 A, 232 I, and 323 N could not be characterized at this time. The sequences in this study displayed aa changes previously described for FPV (A14T, A91S, I101T, N564S, and A568G) from cats and CPV-2a/2b (S297N and Y324L) from dogs. However, the Y324L mutation has not yet been reported in any CPV-2a/2b strains from cats. Phylogenetic analysis supported the division of these sequences into two well-defined clades, clade 1 for FPV and clade 2 for CPV2a/2b. Unusually, the sequence RJ1085/11 was grouped separately. Two recombination breakpoints were detected by Bootscan and 3Seq methods implemented in the RDP4. This study is the first report of CPV-2a/2b in cats in Brazil. The detection of FPV strains with mutations characteristic of CPV indicates that Brazilian FPV strains have undergone genetic changes.

TaqMan-based real-time polymerase chain reaction for the detection of feline chaphamaparvovirus

Feline chaphamaparvovirus (FeChPV) is a new viral strain detected in Chinese Mainland in recent years. The symptoms mainly include diarrhea and bloody stool in young cats, which can lead to death in severe cases. In this study, a TaqMan-based real-time quantitative PCR (qPCR) with specific primers and TaqMan probes based on the VP1 gene sequence of FeChPV was performed to detect the virus. The established qPCR indicated that there is no cross-reaction of FeChPV with other common feline viruses. The minimum detection limit of the established qPCR method is 3.75 × 10 copies/µL, while conventional PCR is 3.75 × 103 copies/µL. The result that the proposed qPCR protocol was shown to be 100 times more sensitive than conventional PCR. The correlation coefficients exceeded 0.995, and the amplification efficiency was 98%. The difference within and between groups is less than 5%, indicating that the established method has good repeatability. The results of clinical sample detection shown that 16 positive samples were detected from 45 stool samples by the established qPCR method. The conventional PCR method only detected 3 positive samples. In conclusion, the established qPCR method is fast and effective in identifying FeChPV, with higher specificity and sensitivity. It could be used as a diagnostic tool to quantitatively detect the virus content, which is conducive to disease monitoring and epidemiological investigation.

China-origin G1 group isolate FPV072 exhibits higher infectivity and pathogenicity than G2 group isolate FPV027

Introduction

Feline parvovirus (FPV), a single-stranded DNA virus, is accountable for causing feline panleukopenia, a highly contagious and often lethal disease that primarily affects cats. The epidemiology prevalence and pathogenicity of FPV in certain regions of China, however, remains unclear. The aim of this research was to investigate the epidemiology of FPV in different regions of China in 2021 and compare its infectivity and pathogenicity.

Methods

In this research, a total of 36 FPV strains were obtained from diverse regions across China. Phylogenetic analysis was performed based on the VP2 and NS1 sequences, and two representative strains, FPV027 and FPV072, which belonged to different branches, were selected for comparative assessment of infectivity and pathogenicity.

Results and discussion

The results revealed that all strains were phylogenetically classified into two groups, G1 and G2, with a higher prevalence of G1 strains in China. Both in vitro and in vivo experiments demonstrated that FPV072 (G1 group) exhibited enhanced infectivity and pathogenicity compared to FPV027 (G2 Group). The structural alignment of the VP2 protein between the two viruses revealed mutations in residues 91, 232, and 300 that may contribute to differences in infectivity and pathogenicity. The findings from these observations will contribute significantly to the overall understanding of the molecular epidemiology of FPV in China and facilitate the development of an effective FPV vaccine.

Not Asian Anymore: Reconstruction of the History, Evolution, and Dispersal of the "Asian" Lineage of CPV-2c

Variability has been one of the hallmarks of canine parvovirus type 2 (CPV-2) since its discovery, and several lineages and antigenic variants have emerged. Among these, a group of viruses commonly called Asian CPV-2c has recently been reported with increasing frequency in different regions. Currently, its global epidemiology and evolution are essentially unknown. The present work deals with this information gap by evaluating, via sequence, phylodynamic, and phylogeographic analyses, all the complete coding sequences of strains classified as Asian CPV-2c based on a combination of amino acid markers and phylogenetic analysis. After its estimated origin around 2008, this lineage circulated undetected in Asia until approximately 2012, when an expansion in viral population size and geographical distribution occurred, involving Africa, Europe, and North America. Asia was predicted to be the main nucleus of viral dispersal, leading to multiple introduction events in other continents/countries, where infection establishment, persistence, and rapid evolution occurred. Although the dog is the main host, other non-canine species were also involved, demonstrating the host plasticity of this lineage. Finally, although most of the strains showed an amino acid motif considered characteristic of this lineage, several exceptions were observed, potentially due to convergent evolution or reversion phenomena.

Molecular characterization and genetic diversity of parvoviruses prevalent in cats in Central and Eastern China from 2018 to 2022

Cats are a potential source of genetic diversity for parvoviruses. Herein, 134 samples were collected from cats with clinical gastroenteritis and analyzed for the presence of viral DNA via polymerase chain reaction, which revealed 48 positive samples. Identity analysis of VP2 nucleotide sequences indicated that these 48 strains, belonging to feline panleukopenia virus (FPV) and canine parvovirus type-2 (CPV-2; including new CPV-2a and CPV-2c genotypes), shared 94.59-99.94% nucleotide identity with the reference strains. The FPV strain F8 (isolated from Vietnam) appeared to be a recombinant of strains HB2003 and JS1901, whereas the Chinese CPV-2b strain BM-(11) isolated in 2011 was believed to be a recombinant of strains AH2008 and JS1901. In phylogenetic tree analysis based on VP2 nucleotide sequences, all obtained FPV strains and most reference FPV strains were clustered together, except strain BJ-22, which originated from monkeys. Further, two new CPV-2a strains (AH2005 and AH2008) were close to the newly reported Chinese CPV-2a strains but were distant from the other CPV-2a strains, namely CPV-339 (from the United States) and K022 (from South Korea). Additionally, the FPV and CPV-2 strains had high mutation rates in the antigenic regions of the VP2 protein. According to model prediction of the CPV-VP2 protein, these mutations may cause changes in the tertiary structure of VP2. The findings of this study can be used to improve the pre-evaluation of vaccination efficacy against diseases caused by FPV and CPV-2 in domestic cats and understand their genotypic transmission and mutation trends.

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.

Identification and Molecular Characterization of a Divergent Asian-like Canine Parvovirus Type 2b (CPV-2b) Strain in Southern Italy

Canine parvovirus type 2 (CPV-2) is an infectious agent relevant to domestic and wild carnivorans. Recent studies documented the introduction and spread of CPV-2c strains of Asian origin in the Italian canine population. We investigated tissue samples from a puppy collected during necropsy for the presence of viral enteropathogens and all samples tested positive only for CPV-2. The full coding sequence of a CPV-2b (VP2 426Asp) strain was obtained. This virus was related to CPV-2c strains of Asian origin and unrelated to European CPV-2b strains. The sequence had genetic signatures typical of Asian strains (NS1: 60Val, 545Val, 630Pro; VP2: 5Gly, 267Tyr, 324Ile) and mutations rarely reported in Asian CPV-2b strains (NS1: 588N; VP2: 370Arg). Phylogenetic analyses placed this strain in well-supported clades, including Asian CPV-2c-like strains, but always as a basal, single-sequence long branch. No recombination was observed for this strain, and we speculate that it could have originated from an Asian CPV-2c-like strain that acquired the 426Asp mutation. This study reports the first evidence of an Asian-like CPV-2b strain in Italy, confirming the occurrence of continuous changes in the global CPV-2 spread. Since positive convergent mutations complicate data interpretation, a combination of phylogenetic and mutation pattern analyses is crucial in studying the origin and evolution of CPV-2 strains.