Development and Evaluation of Real-Time Reverse Transcription Polymerase Chain Reaction Test for Quantitative and Qualitative Recognition of H5 Subtype of Avian Influenza Viruses.

Avian influenza viruses (AIV) affect a wide range of birds and mammals, cause severe economic damage to the poultry industry, and pose a serious threat to humans. Highly pathogenic avian influenza viruses (HPAI) H5N1 were first identified in Southeast Asia in 1996 and spread to four continents over the following years. The viruses have caused high mortality in chickens and various bird species and deadly infections in humans. Multiple conventional methods have been so far introduced for the detection and identification of avian influenza viruses. Traditional virus isolation methods are gold standard protocol in AI detection; nonetheless, virus isolation in embryonating chicken eggs (ECE) is not a rapid method for the detection of influenza viruses since it is time-consuming and labor-intensive. Furthermore, the isolation of highly pathogenic viruses, such as H5, needs BSL3 laboratories. Real-Time Reverse Transcription-Polymerase Chain Reaction (RRT-PCR) is a sensitive and specific method for the detection of influenza viruses. The application of these nucleic acid-based techniques has increased our ability to identify and perform influenza virus care programs, especially in surveillance programs. The current study aimed to detect H5 subtype of avian influenza (AI) virus using fast, specific, and sensitive TaqMan RRT-PCR. Notably, single step RRT-PCR was used to prevent possible laboratory contamination. The specificity of this test was evaluated using nucleic acid extracted from several poultry pathogenic microorganisms and negative clinical specimens from AI-uninfected birds. The sensitivity analysis of the RRT-PCR assay was performed using in vitro-transcribed RNA copy and 10-fold serial dilution of standard AI virus with specific titer. The results indicated the high sensitivity of this method and the lowest detectable dilution of this method based on RNA copies and 1:10 serial dilutions of the standard virus was 10 1.9 EID50 /100.

Development and Evaluation of Real-Time RT-PCR Test for Quantitative and Qualitative Recognition of Current H9N2 Subtype Avian Influenza Viruses in Iran.

Avian influenza H9N2 subtype viruses have had a great impact on Iranian industrial poultry production economy since introduction in the country. To approach Rapid and precise identification of this viruses as control measures in poultry industry, a real time probe base assay was developed to directly detect a specific influenza virus of H9N2 subtype -instead of general detection of Influenza A viruses- which has been endemic over two last decades in the country. An Iranian avian influenza virus strain of A/Iran/chicken/772/1998 H9N2 subtype were selected as reference strain for of primers and probe designing. The high agreement value of 99% indicated that the devolved real time assay for detection of H9 subtype viruses could easily replace the conventional method of virus isolation particularly in investigation of viruses like national surveillance plan. The limit of detection was almost one EID50 which was the least real infectious unit could be detected. So it can be said that this sensitive assay provided a powerful tool to not to miss any significant viral biological activity neither in the host body nor in the environment. A high level of correlation coefficient (R2 = 0.998) also indicated a good correlation between Ct values and viral concentrations. , it can be conclude that the real time RT-PCR could be easily replace virus isolation in detection of H9N2 influenza viruses especially in large monitoring program. The ability in quantifying of the virus concentration extends usage of test in more accurate studies.