Commentary
CDC
Cites Recombination In Influenza Evolution
Recombinomics Commentary 22:02
January 8, 2009
Point mutation or recombination in viral genes
The above comments are from slide 6 of today’s COCA teleconference entitled “Antiviral resistance among influenza A viruses and interim guidance for use of antivirals” by Anthony Fiore from the CDC’s Influenza Division. Although primarily directed at physicians to supplement the CDC interim guidance on the high frequency of Tamiflu resistance in H1N1 in the United States, the initial slides were designed to provide some background on how influenza evolves. The presentation noted that drift was caused by recombination between short regions of influenza genes.
This is a welcome change. In the past genetic drift was said to be due to selection of frequent copy errors, but sequence data showed that large regions of flu genes could be faithfully copied for dozens of years, and new polymorphisms were usually already found in the sequence database and followed acquisition rules that were far from random.
Moreover, in tomorrow’s NY Times the CDC’s chief of flu prevention, Joseph S Bresee, agreed that the H274Y polymorphism conferring Tamiflu resistance was likely to be a genetic hitch hiker that was being distributed by H1N1 with additional changes that created a strong selective advantage.
The Times reported noted that an HA change A193T was associated with the spread of the resistance. A193T is on all published HA sequences from the United States this season, as well as elementary students in Sendai, Japan, where H1N1 outbreaks closed 10 elementary schools in October, as reported the NIH in Japan. Additional closures were reported for elementary schools in Shiga Prefecture in November.
The Times article also noted that A193T has not been in any of the H1N1 vaccine targets in recent years, raising concerns of vaccine driven selection.
The acknowledgement of recombination in flu paves the way for a more detailed understanding of “elegant evolution” and the application of this process for predicting vaccine targets before they emerge.
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