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The prevalence of low virulence classical swine fever virus (CSFV) strains makes viral eradication difficult in endemic countries. However, the determinants for natural CSFV attenuation and persistence in the field remain unidentified. The aim of the present study was to assess the role of the RNase activity of CSFV Erns in pathogenesis, immune response, persistent infection, and viral transmission in pigs. To this end, a functional cDNA clone pPdR-H30K-36U with an Erns lacking RNase activity was constructed based on the low virulence CSFV field isolate Pinar de Rio (PdR). Eighteen 5-day-old piglets were infected with vPdR-H30K-36U. Nine piglets were introduced as contacts. The vPdR-H30K-36U virus was attenuated in piglets compared to the parental vPdR-36U. Only RNA traces were detected in sera and body secretions and no virus was isolated from tonsils, showing that RNase inactivation may reduce CSFV persistence and transmissibility. The vPdR-H30K-36U mutant strongly activated the interferon-α (IFN-α) production in plasmacytoid dendritic cells, while in vivo, the IFN-α response was variable, from moderate to undetectable depending on the animal. This suggests a role of the CSFV Erns RNase activity in the regulation of innate immune responses. Infection with vPdR-H30K-36U resulted in higher antibody levels against the E2 and Erns glycoproteins and in enhanced neutralizing antibody responses when compared with vPdR-36U. These results pave the way toward a better understanding of viral attenuation mechanisms of CSFV in pigs. In addition, they provide novel insights relevant for the development of DIVA vaccines in combination with diagnostic assays for efficient CSF control. [ABSTRACT FROM AUTHOR]

The diagnosis and control of economically important viral diseases have progressed significantly in the last decade due to the application of polymerase chain reaction (PCR) technologies, as well as various applications thereof such as the PCR reaction based on the fluorescence detection in real time (rPCR), the loop-mediated isothermal amplification (LAMP) and the sequencing techniques based on nucleic acids. These approaches allow the amplification, simultaneous quantification and sequence analysis of nucleic acids, combining high speed with sensitivity and specificity, the benefits related to the conventional or endpoint PCR assays, a high dynamic range, a reduced cross contamination, the ability to be scaled, and the precise quantification of the target, allowing the determination of the viral load. [ABSTRACT FROM AUTHOR]

Avian influenza virus causes infection, disease and death on different bird species and has also acquired the capability of transmitting from avian species to humans and other mammals causing severe diseases. For that reason, there is a great international concern on avian influenza virus detection and diagnostic strategies. Although conventional laboratory methods used for isolation and identification of the virus and for detection of specific antibodies continued to be widely applied, new technologies have been rapidly developed. With the use of molecular tools detection, pathotyping, and phylogenetic characterization of influenza A viruses obtained from clinical specimens can be done on the some day. [ABSTRACT FROM AUTHOR]

Equine influenza is an acute respiratory infection of horses, donkeys, mules and zebras. Nowadays, the reverse transcriptase polymerase chain reaction (RT-PCR) and real-time RT-PCR (rRT-PCR) assays are being widely used in diagnostic laboratories as a more sensitive alternative to virus isolation for the detection of equine influenza virus. The purpose of this study was to standardize an rRT-PCR, based on SYBR Green-I coupled with melting curve analysis for the detection of equine influenza virus (gene M) and the typing of hemagglutinin gene (HA). Sensitivity and specificity of the assay (gene M) were evaluated. In terms of the matrix gene copy number, the detection limit was 4.5 gene copies/µl of in vitro transcribed RNA. The linear range obtained for the transcript in the assay genered a typical standard curve from 107 until 100 gene copies/µl in terms of RNA copy number. The correlation coefficient (R²) was 0.99 for the RNA copies detected in nuclease free water and the error of standard curve was 0.0139. The rRT-PCR assay showed to be specific for equine influenza virus. No specific amplification curves were obtained with any of the other viruses tested such as equine viral arteritis, equine herpesvirus-1 and equine herpesvirus-4. The assay showed amplification and specific melting curves when the second set of primers against HA gene was evaluated. Thus, the proposed SYBR Green-I based rRT-PCR assay for the detection of equine influenza virus can be used in case of a possible emergency of this agent in Cuba. [ABSTRACT FROM AUTHOR]

Bluetongue is a non-contagious acute viral disease affecting ruminants. It is a disease of great clinical importance for the physical deterioration and the long convalescence that it causes and, from the economic point of view, for the colossal production losses and prevention and control expenses. It is highly feared in spite of being innocuous for man and of only medium mortality. Bluetongue virus spreads from animal to animal by biting insects of the genus Culicoides and this is the reason for the disease being more prevalent in the geographic areas where climate conditions are favorable for the insect development. The disease was described in detail in early 1900, and at present, is one of the main concerns in animal health, being studied in order to clarify its epidemiology and pathogenesis and to control its spreading. In this review, an attempt has been made to summarize some aspects of the disease related to its history, economic importance and etiological agent, the viral genome organization, the disease epidemiology and distribution, its clinical signs and lesions, as well as its diagnosis. [ABSTRACT FROM AUTHOR]