Figure 5: MAbs M2-4 and E2-9 in combination conferred best protection against systemic candidiasis in passive transfer experiments. A monoclonal antibody (MAb IgG3 M2-4) specific for Met6 peptide was obtained by use of standard hybridoma techniques. BALB/c mice were given an i.p. dose of MAb M2-4, or MAb E2-9 or the MAbs in combination four hours before hematogensous challenge with a lethal dose of C. albicans 3153A cells. (A) Mice received either MAb M2-4 or MAb E2-9 had 60% survival rate with prolonged survival as compared to control animals that received either DPBS or adsorbed MAbs; surprisingly, the MAbs combination (M2-4/E2-9) treatment was able to provide the best protection, 100% survival up to 50 days. Passive protection was prevented by removal of the MAbs through absorption with C. albicans cells before transfer, which provided strong additional evidence for the protection being due to the MAbs. (B) Consistently, the group received treatment of two protective MAbs in combination had the least CFUs among all the groups (P< 0.01). (C) To test how many doses of each MAb are needed for providing complete protection in naïve mice, each MAb was further evaluated by giving to naïve mice every other day post-challenge for two weeks. When given every other day for 14 days, MAb M2-4 was able to increase protection of recipient animals from 60% to 80%, and for MAb E2-9, from 60% to 100%. Combination of two protective MAbs provides the best protection with reduced dose of each MAb administered.