SDS-PAGE and Western blot analysis of epitope-expressing phages. 3 × 1014 purified phage particles were separated by SDS-PAGE gel and transferred to PVDF membrane for Western blot assay. A is SDS-PAGE analysis of purified recombinant phage particles. B and C are the Western blot results, using rabbit sera against Leptospira interrogans or recombinant proteins. D is the result using sera mixture from five IgG- and IgM- positive leptospire patients. Lane M, protein ladder; lane 1, wild type M13KE particles; lane 2-5, recombinant phage particles containing epitope fragments 58-78, 87-98, 173-191 and 297-320 from OmpL1; lane 6-9, recombinant phage particles containing epitope fragments 30-48, 181-195, 233-256 and 263-282 from LipL41.