Influenza A virus is subtyped based on the antigenicity of its two surface

27 28 The recent association of certain Influenza A subtypes with clinically relevant phenotypes has 29 led to the increasing importance of subtyping by clinical virology laboratories. To provide 30 clinical laboratories with a definitive immunofluorescence assay for the subtyping of influenza A 31 virus isolates, we generated a panel of monoclonal antibodies (MAbs) against the major 32 circulating influenza A subtypes using multiple inactivated H1N1, H3N2, and 2009 H1N1 strains 33 individually as immunogens. Eleven MAbs that target hemagglutinin (HA) of H1N1 and H3N2 34 subtypes were selected. These MAbs were combined into three subtype-specific reagents, one 35 each for pan-H1 (seasonal and 2009 strains), H3, and 2009 H1for the subtyping of influenza A36 positive specimens by indirect immunofluorescence assay (IFA). Each subtype-specific reagent 37 was tested on twenty-one prototype influenza A virus strains and confirmed to be specific for its 38 intended subtype. In addition, the subtyping reagents did not cross-react with any of forty other 39 viruses. The clinical performance of the subtyping reagents was evaluated with seventy-five 40 archived clinical samples collected between 2006 and 2009 using the D 3 Ultra DFA influenza A 41 ID Reagent (Diagnostic Hybrids, Inc., a Quidel Company, Athens, OH) and the influenza A 42 subtyping reagents by IFA simultaneously. Sixty-four samples grew virus and were subtyped as 43 follows: thirty H3N2, nine seasonal H1N1 and twenty-five 2009 H1N1. RT-PCR was used to 44 confirm subtyping influenza A of these samples and there was 100% agreement with IFA. This 45 subtyping IFA provides clinical laboratories with a cost-effective, diagnostic tool for better 46 management of influenza virus infection and surveillance of influenza virus activity. 47 on D ecem er 3, 2017 by gest ht://jcm .sm .rg/ D ow nladed fom