Reassortant influenza A viruses have been responsible for 3 major human pandemics this century. Although influenza B shares the segmented genome which allows influenza viruses to reassort into novel genetic combinations, it is a pathogen only in humans and thus lacks the large gene pool in aquatic birds that provides the genetic diversity for emergence of pandemic strains seen with influenza A. Reassortment of 2 influenza B viruses to produce a novel virus has been performed in the laboratory, but has not been described in nature. We utilized direct sequencing to establish the hemagglutinin and neuraminidase nucleotide and amino acid sequences of influenza B viruses collected in Memphis, Tennessee, and Nanchang, China between 1993 and 1997, and compared them to sequences available in Genbank. 3 viruses collected in Memphis in 1993, 1995, and 1996 possess a hemagglutinin gene closely related to B/Yamagata/16/88 (the prototype for currently circulating influenza B viruses), and a neuraminidase gene closely related to B/Beijing/1/87, a virus in the other branch of the evolutionary tree of influenza B viruses. 43 characteristic nucleotide differences between the HA1s of representative viruses related to B/Yamagata/16/88 or B/Beijing/1/87 coding for 17 amino acid changes, and 17 nucleotide differences accounting for 8 amino acid changes in the NAs were examined. The HA1s of the reassortant viruses possessed nucleotides corresponding to the B/Yamagata-like strains in 35/43 (82%) of these positions, accounting for amino acid changes in 14/17 (82%), and possessed nucleotides in 0/43 positions corresponding to B/Beijing, accounting for amino acid changes in 0/17 possible cases. The NAs of the reassortant viruses possessed nucleotides corresponding to B/Yamagata-like strains in 2/17 (12%) in these positions, accounting for amino acid changes in 1/8 (12%) cases, and possessed nucleotides corresponding to B/Beijing-like strains in 14/17 (82%) positions, accounting for amino acid changes in 6/8 (75%) possible positions. Analysis of viruses isolated before 1993 and after 1996 in Memphis, and isolated in 1993 through 1997 in Nanchang demonstrates no gene reassortment. This is the first description of reassortment of influenza B in nature, and has important implications for epidemic human influenzal disease.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - Feb 1999|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)