Studies of the pH inactivation of three variants of Mengo encephalomyelitis virus

Abstract

Three variants of Mengo virus (designated L, M, and S) are rapidly inactivated when incubated at slightly acid pH's. The inactivation reaction appears to have a rigorous requirement for chloride (or bromide) ions; no loss of infectivity occurs when the virions are incubated at slightly acid pH's in solutions of other salts, including sodium iodide and sodium fluoride. Inactivation is maximal at pH 6.2 and at a sodium chloride concentration of 0.1-0.2 M. The rate of inactivation is temperature dependent, being approximately doubled for each 10 ° rise in temperature over the range 7-37 °C. At 17 ° (but not at 37 °) the M variant may be shown to be inactivated more rapidly than are the other two. The inactivation of all three variants results in the dissociation of the viral capsids into protein subunits of uniform size having a sedimentation coefficient of the order of 15 S. If care is taken to block the activity of traces of nucleases that appear to be present in preparations of purified virus, it can be shown that this dissociation proceeds with the release of intact viral genomes from the virions. © 1970.