Bacteriophage conjugates: the effect of coupling reaction and specific antibodies on the kinetics of inactivation and reactivation.

The reaction of bacteriophage T4 with l-fluoro-2,4-dinitrobenzene resulted in a covalent binding of 2,4-dinitrophenyl (D N P) determinants to the phage. From the kinetics of inactivation re­ flecting the coupling process it is concluded that attachment of more than one D N P group to the critical site(s) of the phage is required for inactivation (multi-hit reaction). Contrary to this the neutralization c f D N P-T4 by anti-D N P antibody turned out to be a first order re­ action, until 80 °/o neutralization fitting one-hit kinetics. If compared with native T4, the susceptibility of D N P-T 4 to neutralization by anti-T4 antibody is considerably higher, indicating that attachment of D N P groups to T4 amplifies the sensitivity to neutralization by anti-T4. Comparing neutralization kinetics of D N P-T 4 and native T4 by anti-D N P-T 4 antibody it is suggested that native determinants and D N P groups, as well as determinants resulting from alteration due to the coupling process, all together may contribute as targets for neutralization. Three characteristics strengthen the view that the velocity of T4 conjugates in infecting the host strain is markedly decreased if compared with that of native T 4 : (a) considerable discrepancy between direct plating and decision technique (b) increasing variety of plaque size and (c) decreased velocity of the first step of repro­ duction. The kinetics of neutralization observed can be reconciled with a model proposed by K rummel and U h r . The kinetics of reactivation of neutralized D N P -T 4 by the presence cf D NP-BSA has been investigated and the problems involved in the reaction are discussed.