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Three out of 36 poliovirus type 1-specific monoclonal antibodies which, at 37 °C in a medium of normal ionic strength (It = 0'16), caused only aggregative neutralization (reversible by immune complex dissociation at pH2) shifted to cause disruptive, acid-irreversible neutralization when the temperature was raised to 39 °C or the ionic strength was lowered to 1/100 of normal.Under both conditions, the antigenic conversion was stoichiometric, but the efficiency was lower at 39 °C than at low ionic strength. Antigenic conversion and irreversible neutralization under both conditions were inhibited by WIN 51711, a capsid-stabilizing compound. Complete inhibition required filling of most of the virion's binding pockets by this compound.

Three of thirty-six monoclonal antibodies were found to cause irreversible inactivation of tpe 1 poliovirus at 39°C but not at 37°C. Neutralization at 37°C depended on aggregation and was reversible by acid-induced deaggregation; at 39°C, the virions (N antigenic, 160S) were disrupted to empty capsids (H antigenic, 100S), and neutralization was irreversible. The rate of antibody-dependent conversion of N to H antigen increased steeply between 37 and 39°C.