A real-time reverse transcriptase polymerase chain reaction for detection and quantification of Vesiculovirus

RT-qPCR for the diagnosis of the vesiculovirus Cocal virus

Cocal virus (COCV) is one of the causative agents of vesicular stomatitis, presenting clinical signs indistinguishable from those caused by foot-and-mouth disease virus (FMDV). Therefore, the differentiation of these two viruses via laboratory diagnosis is essential. The objective of this study was to develop and validate a real-time quantitative PCR (RT-qPCR) protocol for the diagnosis of COCV directly from epithelial samples. The method developed had 97% accuracy at 3950 pfu and a repeatability error of 1.29%. RT-qPCR was able to distinguish COCV from other viruses that cause vesicular diseases, an important factor because seroneutralization may produce cross-reactivity between COCV and vesicular stomatitis Alagoas virus (VSAV). No epithelial sample originating from vesicular disease outbreaks between 2014 and 2018 in Brazil was positive for COCV.

Increased Virulence of an Epidemic Strain of Vesicular Stomatitis Virus Is Associated With Interference of the Innate Response in Pigs

Vesicular stomatitis virus (VSV) causes sporadic outbreaks of vesicular disease in the southwestern United States. The intrinsic characteristics of epidemic strains associated with these outbreaks are poorly understood. In this study, we report the distinctive genomic and biological characteristics of an epidemic (NJ0612NME6) strain of VSV compared with an endemic (NJ0806VCB) strain. Genomic comparisons between the two strains revealed a total of 111 nucleotide differences (23 non-synonymous) with potentially relevant replacements located in the P, G, and L proteins. When tested in experimentally infected pigs, a natural host of VSV, the epidemic strain caused higher fever and an increased number of vesicular lesions compared to pigs infected with the endemic strain. Pigs infected with the epidemic strain showed decreased systemic antiviral activity (type I - IFN), lower antibody levels, higher levels of interleukin 6, and lower levels of tumor necrosis factor during the acute phase of disease compared to pigs infected with the endemic strain. Furthermore, we document the existence of an RNAemia phase in pigs experimentally infected with VSV and explored the cause for the lack of recovery of infectious virus from blood. Finally, the epidemic strain was shown to be more efficient in down-regulating transcription of IRF-7 in primary porcine macrophages. Collectively, the data shows that the epidemic strain of VSV we tested has an enhanced ability to modulate the innate immune response of the vertebrate host. Further studies are needed to examine other epidemic strains and what contributions a phenotype of increased virulence might have on the transmission of VSV during epizootics.

Development and validation of rt-qpcr for vesicular stomatitis virus detection (Alagoas vesiculovirus)

Vesicular stomatitis is an infectious disease that occurs mainly in countries of the Western Hemisphere and affects cattle, swine and horses. The clinical symptoms in cattle and swine are similar to foot-and-mouth disease and include vesicular ulceration of the tongue and mouth. The disease requires a rapid and accurate differential diagnosis, aiming for immediate implementation of control measures. The objective of the present study was to develop and perform validation tests of multiplex RT-qPCR(s) for the detection of RNA from Alagoas vesiculovirus, considering the parameters of sensitivity and analytical specificity, analytical performance (repeatability and reproducibility criteria) and the uncertainty of the measurement. The threshold cycle values obtained in triplicate from each sample were evaluated by considering the variations between days, analysts and equipment in an analysis of variance aimed at determining the variances of repeatability and reproducibility. The results showed that RT-qPCRs had excellent sensitivity and specificity in the detection of RNA of the Alagoas vesiculovirus. The validation parameters showed low coefficients of variation and were equivalent to those found in other validation studies, indicating that the tests presented excellent repeatability and reproducibility.