There is a need to develop HIV-1 vaccine formulations that incorporate inexpensive antigens and clinically acceptable potent adjuvants for inducing neutralizing antibodies. The purpose of this initial vaccine study was to produce peptide- and lipid-induced murine mAbs that replicate the characteristics of the 2F5 and/or 4E10 human antibodies in binding both to the membrane proximal external region (MPER) of glycoprotein 41 and the adjacent lipid bilayer for neutralizing HIV-1 infection of CD4 lymphocytes. RESEARCH DESIGNS AND METHODS: Liposomes containing a synthetic MPER peptide as a peptide antigen, phosphatidylinositol-4-phosphate (PIP) as a lipid antigen, and monophosphoryl lipid A as a potent adjuvant were used as a formulation to immunize mice. mAbs were then produced and tested for binding to MPER, glycoprotein 41, and PIP and for the ability to neutralize HIV-1 infection of CD4 cells in a human peripheral blood mononuclear cell assay. Polyclonal antisera contained antibodies that bound both to MPER and PIP. Immunoglobulin M mAbs were produced that bound both to the core MPER site of 2F5, or that overlapped with the 4E10 site, and that simultaneously bound PIP. High concentrations of these mAbs neutralized infection of peripheral blood lymphocytes by a primary infectious molecular clone of HIV-1. Liposomes containing MPER peptide as an antigen, PIP as a lipid antigen, and lipid A as an adjuvant induce anti-MPER-specific multispecific antibodies that simultaneously bind glycoprotein 41 MPER and adjacent lipid and neutralize HIV-1 infection in a human peripheral blood mononuclear cell assay.