Inhibition of Orbivirus Replication by Aurintricarboxylic Acid.

Bluetongue virus (BTV) and African horse sickness virus (AHSV) are vector-borne viruses belonging to the Orbivirus genus, which are transmitted between hosts primarily by biting midges of the genus Culicoides. With recent BTV and AHSV outbreaks causing epidemics and important economy losses, there is a pressing need for efficacious drugs to treat and control the spread of these infections. The polyanionic aromatic compound aurintricarboxylic acid (ATA) has been shown to have a broad-spectrum antiviral activity. Here, we evaluated ATA as a potential antiviral compound against Orbivirus infections in both mammalian and insect cells. Notably, ATA was able to prevent the replication of BTV and AHSV in both cell types in a time- and concentration-dependent manner. In addition, we evaluated the effect of ATA in vivo using a mouse model of infection. ATA did not protect mice against a lethal challenge with BTV or AHSV, most probably due to the in vivo effect of ATA on immune system regulation. Overall, these results demonstrate that ATA has inhibitory activity against Orbivirus replication in vitro, but further in vivo analysis will be required before considering it as a potential therapy for future clinical evaluation.

Immune gene expression profiling of PBMC isolated from horses vaccinated with attenuated African horsesickness virus serotype 4.

Development of African horsesickness (AHS) subunit vaccines will have to include a rational approach that uses knowledge of how the virus interacts with the host immune system. The global in vivo immune response induced by attenuated AHSV serotype 4 in horses was characterised using transcriptome sequencing. PBMC were collected with 24h intervals for four days after inoculation and four days after a second boost, 21 days later. Transcriptome data were normalised to the day 0 naïve transcriptome and up- or down-regulated immune genes identified using the CLC workbench. Peak expression was observed 24h after each inoculation. Innate immunity was up-regulated after both inoculations and was characterised by type-1 interferon activation via the RIG-1/MDA5 pathway and the up-regulation of complement cascade components. After the second boost an adaptive immune response could be identified that included the production of cytokines indicative of T helper (Th)1, Th2 and Th17 responses.

Effects of chlorine, iodine, and quaternary ammonium compound disinfectants on several exotic disease viruses.

The effects of three representative disinfectants, chlorine (sodium hypochlorite), iodine (potassium tetraglicine triiodide), and quaternary ammonium compound (didecyldimethylammonium chloride), on several exotic disease viruses were examined. The viruses used were four enveloped viruses (vesicular stomatitis virus, African swine fever virus, equine viral arteritis virus, and porcine reproductive and respiratory syndrome virus) and two non-enveloped viruses (swine vesicular disease virus (SVDV) and African horse sickness virus (AHSV)). Chlorine was effective against all viruses except SVDV at concentrations of 0.03% to 0.0075%, and a dose response was observed. Iodine was very effective against all viruses at concentrations of 0.015% to 0.0075%, but a dose response was not observed. Quaternary ammonium compound was very effective in low concentration of 0.003% against four enveloped viruses and AHSV, but it was only effective against SVDV with 0.05% NaOH. Electron microscopic observation revealed the probable mechanism of each disinfectant. Chlorine caused complete degeneration of the viral particles and also destroyed the nucleic acid of the viruses. Iodine destroyed mainly the inner components including nucleic acid of the viruses. Quaternary ammonium compound induced detachment of the envelope of the enveloped viruses and formation of micelle in non-enveloped viruses. According to these results, chlorine and iodine disinfectants were quite effective against most of the viruses used at adequately high concentration. The effective concentration of quaternary ammonium compound was the lowest among the disinfectants examined.

Detection of African horse sickness virus in the blood of experimentally infected horses: comparison of virus isolation and a PCR assay.

A reverse transcription-polymerase chain reaction (RT-PCR) assay followed by dot-blot hybridisation was used to detect African horse sickness virus (AHSV); the primers employed amplified the S7 gene that encodes the VP7 protein. The RT-PCR assay was compared with virus isolation for detecting AHSV in blood samples form horses experimentally infected with AHSV-4 and AHSV-9. The influence of sample storage and transportation and the effects of two anticoagulants (EDTA and heparin) were also studied. RT-PCR results were obtained within 48 hours as opposed to a minimum of 15 days for virus isolation. RT-PCR and virus isolation were equally sensitive for detection of AHSV-4. Viraemia was detected more consistently by RT-PCR than by virus isolation from horses infected with the less virulent AHSV-9 isolate except from one animal in which virus was detected only by virus isolation. The sensitivity of virus isolation was increased by passaging samples five times. This study indicates that RT-PCR is a sensitive and rapid method for use in the face of an outbreak of this serious disease, although it has also some limitations as a diagnostic technique.

Inactivation of African horse-sickness virus by betapropiolactone and by pH.

The inactivation of several types of African horse sickness virus (AHSV) by pH and by betapropiolactone (BPL) was studied. At 19 degrees - 22 degrees C the virus was stable between pH 6.0 and 10.4, whether suspended in mouse brain or in serumfree buffer. Below pH 5.6 and above pH 10.9, more than 99 per cent of infectivity was inactivated within 15 minutes. The addition of 50 per cent serum did not influence pH stability. Disinfection in the presence of citric acid and caustic soda is briefly discussed. Inactivation by BPL was complete within 30 minutes at 37 degrees C, yet incomplete after 15 hours at 4 degrees C. Types 3 and 9 virus grown in suckling mouse brain and types 1, 3 and 9 produced in pig kidney cells were equally susceptible to 0.1 per cent BPL, more than 99.9 per cent being inactivated. The effectiveness of BPL was reduced at least 10-fold by the addition of 50 per cent serum. No infective virus was detected following incubation of either tissue culture virus with 0.2 per cent BPL or of mouse brain virus with 0.3 per cent BPL. Virus suspensions exposed to 0.3 per cent BPL required buffering with Tris of at least 0.05 molar strength in order to maintain the pH within an acceptable range. Inactivated antigens prepared with 0.4 per cent or lower concentrations of BPL were immunogenic in guinea pigs.