MONOCLONAL-ANTIBODIES RAISED AGAINST NATIVE MAJOR CAPSID PROTEINS OF LACTOCOCCAL C2-LIKE BACTERIOPHAGES

Phage Q38, a representative member of the c2 species, was purified by CsCl gradient and used to immunize BALB/c mice. Monoclonal antibodies (MAbs) were raised and then characterized by enzyme-linked immunosorbe nt assay. Two MAbs of isotype immunoglobulin G2a, designated 2A5 and 6 G7, reacted only with phages belonging to the c2 species and not with phages of the 936 and P335 species, with a Lactococcus lactis cell ext ract, or,vith phage DNA. Immunoelectron microscopy showed that both MA bs recognized only phage head proteins. They did not react with any de natured phage proteins in Western blot assays. However, when the nitro cellulose membranes were treated with a Triton-based buffer to assist in protein renaturation, MAbs 2A5 and 6G7 recognized the two major cap sid proteins with molecular masses of 80 and 170 kDa. Competitive inhi bition tests showed that the two MAbs bind to overlapping epitopes, Th ese MAbs may be a useful tool for monitoring c2 bacteriophages during dairy fermentation and in genetic studies.