Development of three triplex real-time reverse transcription PCR assays for the qualitative molecular typing of the nine serotypes of African horse sickness virus

• Published in: Journal of virological methods 2015-10, Vol.223, p.69-74
• Main Authors: Weyer, Camilla T., Joone, Christopher, Lourens, Carina W., Monyai, Mpho S., Koekemoer, Otto, Grewar, John D., van Schalkwyk, Antoinette, Majiwa, Phelix O.A., MacLachlan, N. James, Guthrie, Alan J.
• Format: Article
• Language: English
• Subjects: African horse sickness virus; African Horse Sickness Virus - classification; African Horse Sickness Virus - genetics; AHS; Animals; Equine; Field diagnosis; Genotyping Techniques - methods; Horses; Molecular Typing - methods; Multiplex Polymerase Chain Reaction - methods; Real-Time Polymerase Chain Reaction - methods; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Viral - genetics; RT-qPCR; Sensitivity and Specificity; Serogroup; Serotype
• ISSN: 0166-0934; 1879-0984
• DOI: 10.1016/j.jviromet.2015.07.015

•Three AHSV TS RT-qPCR assays can be applied directly to nucleic acid extracted from blood.•Multiplexing of the primers and probes for 9 AHSV serotypes increases assay output.•Use of these assays with a group specific AHSV RT-qPCR assay can enhance investigation of outbreaks. Blood samples collected as part of routine diagnostic investigations from South African horses with clinical signs suggestive of African horse sickness (AHS) were subjected to analysis with an AHS virus (AHSV) group specific reverse transcription quantitative polymerase chain reaction (AHSV RT-qPCR) assay and virus isolation (VI) with subsequent serotyping by plaque inhibition (PI) assays using AHSV serotype-specific antisera. Blood samples that tested positive by AHSV RT-qPCR were then selected for analysis using AHSV type specific RT-qPCR (AHSV TS RT-qPCR) assays. The TS RT-qPCR assays were evaluated using both historic stocks of the South African reference strains of each of the 9 AHSV serotypes, as well as recently derived stocks of these same viruses. Of the 503 horse blood samples tested, 156 were positive by both AHSV RT-qPCR and VI assays, whereas 135 samples that were VI negative were positive by AHSV RT-qPCR assay. The virus isolates made from the various blood samples included all 9 AHSV serotypes, and there was 100% agreement between the results of conventional serotyping of individual virus isolates by PI assay and AHSV TS RT-qPCR typing results. Results of the current study confirm that the AHSV TS RT-qPCR assays for the identification of individual AHSV serotypes are applicable and practicable and therefore are potentially highly useful and appropriate for virus typing in AHS outbreak situations in endemic or sporadic incursion areas, which can be crucial in determining appropriate and timely vaccination and control strategies.