The long term goal of this work is to prepare multivalent, multiepitope peptide-phospholipid composites that induce protective immunity in humans by inducing a primary immune response and by priming the immune system to produce a secondary immune response involving both antibodies and cytotoxic T lymphocytes in response to a pathogen challenge. Our research has demonstrated that peptide-phospholipid composites can stimulate very high antibody titers when the peptides which code for both B cell and T helper cell epitopes are covalently linked to phosphatidylethanolemine and injected as a peptide-phospholipid composite.
The specific aims of this research proposal are to focus on understanding in greater depth the properties governing the ability of peptide- phospholipid conjugates to elicit an immune response. We will extend our ongoing work in the following specific directions: 1. To further investigate and define the parameters regulating the ability of peptide- phospholipid conjugates to induce an antibody response. Studies on how best to present single B cell epitopes in conjunction with single T helper cell epitopes will be followed by studies involving multiple B cell and multiple T helper cell epitopes. 2. The use of peptide- phospholipid complexes to induce epitope-specific cytolytic T lymphocytes (CTL) will be investigated. Peptides representing epitopes stimulatory for CTL (Tc) will be used either in combination with T helper peptides or in combination with the envelope proteins of Sendai virus or influenza virus. Peptide sequences to be used in this study will be derived from Plasmodium falciparum. All of the various types of epitopes necessary for this study have been defined in P. falciparum. A number of these epitopes have already been used in our system. Information gained through these studies could be directly applicable to a human disease for which no vaccines are currently available. In addition, due to the simplicity of the peptide-phospholipid system, insights obtained using P. falciparum as a model system can and will be readily applied to other infectious agents, especially HIV-1 and HIV-2, as specific and appropriate epitopes become available. Peptide-phospholipid complexes will be prepared and inoculated into mice. The immune response will be measured by a) antibody titers detected by ELISA, b) 3H-thymidine incorporated into TCA percipitable counts for T helper cell activation, and c) 51Cr release for antigen specific cytotoxic T lymphocytes. Pathogen neutralization studies in vitro and in vivo will be carried out by collaborators.