Antiviral effect on MS-2 coliphage obtained with a synthetic antigen

The coat protein of bacteriophage MS-2 was cleaved with cyanogen bromide to yield three fragments, possessing the sequence 1-88 (P1), 89-108 (P2), and 109-129 (P3), respectively. The mixture of peptides P2 and P3, which could not be separated, was found capable of inhibiting the neutralization of the phage by antiserum to the whole MS-2. The peptides corresponding to P2 and P3 were therefore synthesized. The synthetic P3 had no capacity to interfere with neutralization of MS-2, not did its macromolecular conjugate with multichain poly(DL-alanine) elicit neutralizing antibodies. On the other hand, the synthetic P2 was very efficient in inhibiting the inactivation of the phage by the antiserum against phage. Furthermore, a synthetic antigen prepared by attachment of P2 to multichain poly(alanine) incuded antiserum in rabbits that was capable of neutralizing MS-2 activity almost as efficiently as the antiserum prepared against the intact coat protein. This inactivation is specific, because it can, in turn, be totally inhibited by P2 peptide.