Rapid molecular analysis of the haemagglutinin gene of human influenza A H3N2 viruses isolated in Spain from 1996 to 2000

A simple molecular technique was used for the rapid preliminary genetic cha racterization of human influenza A H3N2 viruses isolated in Spain from 1996 to 2000. Subtyping, based on RT-PCR, was followed by subtype-specific rest riction enzyme fragment length polymorphism (RFLP) analyses of an amplified region of the HA1 domain of the H3 haemagglutinin (HA) gene to distinguish variants differentiated by common amino acid substitutions in HAI. The app roach was tested using 135 Spanish H3N2 isolates and included nucleotide se quencing and phylogenetic analyses of a region of the HAI domain of 41 repr esentative isolates. The viruses were distinguished by haemagglutination in hibition (HI) assays into two antigenically discernible groups, the A/Wuhan /359/95-like and A/Sydney/5/97-like viruses. The results of PCR-RFLP analys is allowed a finer classification into five genetic variant subgroups, corr esponding to those distinguished by phylogenetic analyses. This rapid, simp le and variant-specific procedure could, therefore, be used to rapidly scre en clinical specimens prior to more detailed antigenic and genetic, analyse s.