An analysis of the growth curve obtained in vitro for influenza virus in chorioallantoic membrane has been made using two known viral inhibitors,
methoxinine and alpha-amino-alpha p-methoxyphenylmethanesulfonic
acid. The action of these compounds has been shown to be specific for particular phases of viral development. Further, this action is sequential indicating that the inhibited phases do not occur concurrently. The
sulfonic acid interferes with the initiation of
infection and with the release of newly formed virus from the host-cell. The former effect is dependent upon the relative concentrations of viral inoculum and
sulfonic acid. The latter effect is prevented by the action of the receptor-destroying
enzyme obtained from
cholera vibrio extracts. It is proposed that a function of the viral
enzyme is to facilitate the release of virus from the host-cell. The intracellular concentration of virus necessary to initiate this release is increased in the presence of alpha-amino-alpha p-methoxyphenylmethanesulfonic
acid. It was found that
infection can be initiated in the presence of
methoxinine under which condition viral increase is disallowed. The function in viral development of one biochemical process which is inhibited by
methoxinine was found to be completed at an interval after initiation of
infection and before the appearance of the infectious form of the virus. It is possible to define four stages of viral development in terms of sensitivity to
methoxinine and alpha-amino-alpha-p-methoxyphenylmethanesulfonic
acid.