PLGA microparticle based vaccine carriers for an improved and efficacious tumor therapy

Abstract

Cancer is a collection of diseases that is characterized by an uncontrolled proliferation of aberrant cells. The conventional treatment strategies including chemotherapy and radiotherapy prove detrimental to healthy cells and are unable to combat primary and secondary metastases. Hence immunotherapy is gaining momentum in cancer clinics and translational research labs as an alternative safer and more efficacious approach to tumor therapy. Vaccines based on antigen alone lack the ability to optimally activate the antigen presenting cells (APCs) including dendritic cells (DCs) to generate significantly greater antigen-specific T cell responses. A typical strategy to overcome this limitation has been the use of adjuvants in order to improve the immunogenicity of the vaccines. A newer class of adjuvants called toll like receptor (TLR) ligands recognize pathogen associated molecular patterns (PAMP) and thus elicit a Th-1 polarized response. The hypothesis of the current research is that co-delivery of antigen and adjuvant in a microparticulate carrier will elicit a strong cell-mediated immune response conferring anti-tumor immunity. Furthermore, we proposed that a combination of TLR ligands when co-delivered with an antigen will be able to mount a synergistic anti-tumor response in comparison to the delivery of antigen alone. There were three primary objectives of the study; 1) Fabrication, process design optimization and characterization of antigen and adjuvant co-loaded microparticles (MP), 2) Study the ability of the MP fabricated in step 1 in eliciting a potent immune response in a murine model by various routes of administration and 3) Study the effect of the various treatment as prophylactic and therapeutic cancer vaccines in a murine tumor model. Objective 1 was achieved by optimizing various process parameters including PLGA type and concentration, surfactant concentration and modification of a previously reported double emulsification solvent evaporation technique. Process optimization lead to the development of the following 5 treatment groups, a) Empty PLGA MP, b) OVA PLGA MP, c) OVA + CpG PLGA MP, d) OVA + poly I: C PLGA