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.

A duplex SYBR green I-based real-time polymerase chain reaction assay for concurrent detection of feline parvovirus and feline coronavirus

Feline coronavirus (FCoV) contains two serotypes, feline enteric coronavirus (FECV) and Feline infectious peritonitis virus (FIPV). FECV and feline parvovirus (FPV) can cause similar clinical symptoms in cats, such as diarrhea. The objective of this study was to establish a duplex SYBR Green I-based quantitative polymerase chain reaction (qPCR) assay for rapid and simultaneous detection of FPV and FCoV. Two pairs of specific PCR primers were designed to target fragments of the VP2 gene of FPV and of the 5' UTR gene of FCoV, respectively. The assay distinguished between the two viruses based on the melting curves (melting temperatures 77.0 ± 0.5 °C [FPV] and 80.5 ± 0.5 °C [FCoV]). The minimum limits of FPV and FCoV detection were 4.74 × 10¹ copies/μL and 7.77 × 10¹ copies/μL, respectively. The assay showed excellent reproducibility and reliability, based on the mean coefficient of variation. In conclusion, this novel duplex SYBR Green I-based qPCR assay is sensitive and can specifically, reliably, and rapidly detect FPV and FCoV (co-)infections.

Simultaneous detection of feline parvovirus and feline bocavirus using SYBR Green I-based duplex real-time polymerase chain reaction

Since both feline parvovirus (FPV) and feline bocavirus (FBoV) can cause diarrhea in cats, it is difficult to distinguish them clinically. This study aimed to develop a SYBR Green I-based duplex real-time polymerase chain reaction (PCR) assay for distinguishing FPV and FBoV-1 on the basis of the melting temperature of the PCR product. A total of 132 fecal samples from different domestic and feral cats were collected, and the results of SYBR Green I-based duplex real-time PCR assay were compared with those of the traditional PCR assay for a comprehensive evaluation. The melting temperatures were found to be 86 °C and 77.5 °C for FBoV-1 and FPV, respectively, and no specific melting peaks for other non-targeted feline viruses were observed. The data obtained from this assay had a good linear relationship; the detection limits of FPV and FBoV-1 were 2.907 × 10¹ copies/μL and 3.836 × 10¹ copies/μL, respectively. In addition, the experiment exhibited high reproducibility. The positive detection rates of the SYBR Green I-based duplex real-time PCR assay for FPV and FBoV-1 were 16.67% (22/132) and 6.82% (9/132), respectively, and the positive detection rate for co-infection with FPV and FBoV-1 was 3.03% (4/132). This result was much more sensitive than that of the traditional PCR method. Thus, the developed SYBR Green I-based assay is a sensitive, rapid, specific, and reliable method for the clinical diagnosis of FPV and FBoV-1 and can provide technical support for the simultaneous detection of co-infection with these viruses in the future.

Prophylactic Efficacy of Equine Immunoglobulin F(ab')2 Fragments Against Feline Parvovirus

Feline parvovirus (FPV), a type of parvovirus prevalent worldwide, can cause foetal death and acute enteritis in adult cats with severe leukopenia, and yet there are no effective drugs to prevent or treat FPV. Here, the immune effects of two FPV vaccines on horses were compared. IgG was extracted from FPV-immunized horse sera. Equine F(ab′)₂ fragments were obtained from pepsin-digested IgG and then purified by protein-G column chromatography. The results showed that the inactivated FPV oil vaccine was more effective than the inactivated FPV propolis vaccine in helping healthy horses to produce hyper-immune serum. Four methods were tested, among which the optimized octanoic acid-ammonium sulphate precipitation method was proved to be the best process for extracting IgG. The optimal condition for preparing F(ab′)₂ by pepsin digestion was 30 °C for 3.5 h, and the content, purity and recovery of F(ab′)₂ were 8.64 mg/mL, 90.36% and 93.24%, respectively. Our equine immunoglobulin F(ab′)₂ fragments effectively neutralized activity in vitro against FPV, alleviated the clinical symptoms of FPV-infected cats, reduced the viral loads in the intestine and had prophylactic effects in FPV-infected cats. These results indicate that the F(ab′)₂ fragment prepared from inactivated FPV-immunized horses may be used as a prophylactic agent for diseases caused by FPV.

Genetic characterization of feline panleukopenia virus from dogs in Vietnam reveals a unique Thr101 mutation in VP2

Background

Canine parvovirus type 2 (CPV-2) and feline parvovirus (FPV) are known as the main causes of several serious diseases and have a severe impact on puppies and kittens, respectively. FPV and new CPV-2 variants are all able to infect cats, causing diseases indistinguishable from feline panleukopenia. However, FPV only replicates efficiently in feline cells in vitro and replicates in dogs in the thymus and bone marrow without being shed in feces. In our previous study, the genotypes of six parvoviral isolates were unable to be identified using a SimpleProbe^® real-time PCR assay.

Methods

In the present study, we characterized previously unidentified FPV-like viruses isolated from dogs in Vietnam. The six isolates were utilized to complete VP2 gene sequencing and to conduct phylogenetic analyses.

Results

Sequence analysis of the six parvoviral strains identified the species as being similar to FPV. Phylogenetic analysis demonstrated that the complete VP2 genes of the strains are similar to those of FPV. The FPV-like strains contain a Thr101 mutation in the VP2 protein, which is different from prototype FPV strains.

Discussion

Our data provide evidence for the existence of changes in the charge, protein contact potential and molecular surface of the core of the receptor-binding size with an Ile101 to Thr101 mutation. This is also the first study to provide reliable evidence that FPV may be a threat to the Vietnamese dog population.

Simultaneous detection and differentiation of canine parvovirus and feline parvovirus by high resolution melting analysis

BACKGROUND

Canine parvovirus (CPV) and feline parvovirus (FPV) are causative agents of diarrhea in dogs and cats, which manifests as depression, vomiting, fever, loss of appetite, leucopenia, and diarrhea in young animals. CPV and FPV can single or mixed infect cats and cause disease. To diagnose sick animals effectively, an effective virus diagnostic and genome typing method with high sensitivity and specificity is required.

RESULTS

In this study, a conserved segment containing one SNP A4408C of parvovirus was used for real-time PCR amplification. Subsequently, data were auto-analyzed and plotted using Applied Biosystems® High Resolution Melt Software v3.1. Results showed that CPV and FPV can be detected simultaneously in a single PCR reaction. No cross-reactions were observed with canine adenovirus, canine coronavirus, and canine distemper virus. The assay had a detection limit of 4.2 genome copies of CPV and FPV. A total of 80 clinical samples were subjected to this assay, as well as to conventional PCR-sequence assay and virus isolation. Results showed that the percentage of agreement of the assay and other methods are high.

CONCLUSIONS

In short, we have developed a diagnostic test for the accurate detection and differentiation of CPV and FPV in fecal samples, which is also cost effective.

Canine parvovirus type 2 (CPV-2) and Feline panleukopenia virus (FPV) codon bias analysis reveals a progressive adaptation to the new niche after the host jump

Based on virus dependence from host cell machinery, their codon usage is expected to show a strong relation with the host one. Even if this association has been stated, especially for bacteria viruses, the linkage is considered to be less consistent for more complex organisms and a codon bias adaptation after host jump has never been proven. Canine parvovirus type 2 (CPV-2) was selected as a model because it represents a well characterized case of host jump, originating from Feline panleukopenia virus (FPV). The current study demonstrates that the adaptation to specific tissue and host codon bias affected CPV-2 evolution. Remarkably, FPV and CPV-2 showed a higher closeness toward the codon bias of the tissues they display the higher tropism for. Moreover, after the host jump, a clear and significant trend was evidenced toward a reduction in the distance between CPV-2 and the dog codon bias over time. This evidence was not confirmed for FPV, suggesting that an equilibrium has been reached during the prolonged virus-host co-evolution. Additionally, the presence of an intermediate pattern displayed by some strains infecting wild species suggests that these could have facilitated the host switch also by acting on codon bias.