Magnetic Fluorescent Bead-Based Dual-Reporter Flow Analysis of PDL1-Vaxx Peptide Vaccine-Induced Antibody Blockade of the PD-1/PD-L1 Interaction

Our project led by Professor Pravin Kaumaya are focused on developing B-cell epitope peptide vaccines that can be used to boost the immune system to better fight against the cancer. We believe that peptide vaccines targeting immune checkpoint targets may even be combined with other therapies to improve patient outcomes. We wanted to test the blocking ability of our anti PD-L1 antibodies in a traditional microbead assay where human recombinant PD-L1 protein was bound to MagPlex beads.

We found that, once the PD-L1 was bound to the beads, they had a low binding capacity for its PD-1 ligand. This prevented us using this avenue of testing blocking. When binding protein to beads inhibits binding to ligand or antibodies, pretreatment with the test antibodies in solution is an option, later adding ligand-coated beads to the target blocker mixture.

Their interaction may be examined. This may be a different path to study the same target-ligand-binding interaction We have developed B-Vaxx, PD1-Vaxx, PDL1-Vaxx, and CTLA4-Vaxx cancer vaccines. These vaccines target HER2 and several immune checkpoint markers are involved in various forms of cancer.

B-Vaxx and PD1-Vaxx are in ongoing clinical trials in Australia and the US.We hope our immune checkpoint vaccines will benefit more patients. In previous microsphere experiments, we found that PD-1 interacted well with its ligand PD-L1. Therefore, we re-engineered the protocol, prebinding the anti-PD-L1 peptide antibodies to biotinylated PD-L1 protein before adding the PD-1-tagged MagPlex beads.

This allowed us to test our antibodies for their ability to block PD-1/PD-L1 interaction. We will continue to focus on combination immunotherapies that overcome treatment resistance. We also want to explore more effective combination therapies that better inhibit tumor growth, prevent metastasis, and prolong patient survival rates.