Type- and subtype-specific RT-PCR assays for avian influenza A viruses (AIV)

Reverse transcriptase (RT) PCR assays have been developed to improve the di agnosis of avian influenza A. RT-PCR using-primers complementary to a conse rved region of the matrix protein was assessed as being suitable for the de tection of influenza A virus RNA from poultry as well as from pigs, horses and humans, regardless of the haemagglutinin (HA) and neuraminidase (NA) su btype. Therefore, this RT-PCR is a valuable tool to confirm the initial dia gnosis of any influenza A infection. As a second approach, experiments were performed to identify the HA gene en coding the posttranslational cleavage site of potentially highly pathogenic AIV isolates by RT-PCR. The principal aim was to design one universal prim er pair for each virus subtype, H5 and H7, respectively, which allows the d etection of all strain variants using only one consistent method. To realiz e this objective, it was necessary to develop 'wobble' primers. AIV RNAs fr om seven H5 and 11 H7 subtype viruses included in the investigations were s pecifically recognized by RT-PCR using these primers. This method therefore provides a rapid, subtype-specific diagnosis and subsequent sequencing of H5 and H7 avian influenza viruses.