Single plaques were isolated after three days
of growth in cell cultures and used to infect the allantoic cavities of chicken
eggs (2). Viruses were harvested after
two days and plated in the presence and absence of amantadine to score
resistant viruses. From ten independent
experiments, the average f-values
were 4.2 ´ 10-4 and 1.8 ´ 10-3 for H1N1 and H2N2 genotypes,
respectively. Amantadine resistance was conferred
by four different nucleotide substitutions (T
= Ts = 4), which were
probably neutral (a » 1).
In the original publication, the mutation rate per strand copying was
estimated by assuming binary replication, but this assumption does not seem justified. According to other authors (1) the virus
completes a cell infection cycle in ca. 7 hours. Thus, after 5 days of growth, c = 17. Thus, ms/n/c = 3 ´ 4.2 ´ 10-4 / 17 / 4 = 1.9 ´ 10-5 for H1N1, ms/n/c = 7.9 ´ 10-5 for H2N2, the geometric mean being 3.9 ´ 10-5.
1. Nobusawa, E. and K. Sato. 2006. Comparison of
the mutation rates of human influenza A and B viruses. J Virol. 80:3675-3678.
2. Stech, J., X. Xiong,
C. Scholtissek, and R. G. Webster. 1999.