Nanovaccines for Cancer Immunotherapy

There are three major types of therapeutic approaches currently available to combat cancer, namely chemotherapy (which utilises small molecule agents to destroy cancer cells), radiotherapy (radio labelled small molecules) and immunotherapy. The immunotherapy is the oldest among them, which dates back to the discovery of a surgeon known as William B. Coley in 1891, who has treated his patients with bacterial products, which is now believed to have induced non-specific inflammatory responses [2]. However, immunotherapy as a cancer treatment regiment has been a subject of debate for a long time due to continuous failures in clinical trials until 2013, the year in which ‘Nature’ has declared as ‘breakthrough of the year’. Resurgence of cancer immunotherapy or Immno-Oncology (as sometimes referred to) is now evident in the advent of dendritic cell-based vaccines and immune checkpoint inhibitors. They have ushered a new line of cancer therapy and raised the hope for harnessing patients’ own immune system to eradicate tumours. Cancer immunity by the human immune system is a highly complex cascade of immune response events. However, it can be attempted to be summarized in to four fold steps. Firstly, the release of antigens from tumours, secondly, presentation of tumour antigens by antigen-presenting cells (APCs), thirdly, priming and activation of T cells by activated APCs, fourthly the migration and infiltration of effectors T cells (Teff) back to the tumour and finally the recognition and destruction of tumour cells by Teff [3]. In theory, each of these steps can be targeted in terms of various therapeutic approaches and can be divided into two major types, namely the passive and active therapeutic approaches. The passive immunotherapy is associated with immune checkpoint inhibitors [4] which are monoclonal antibodies directed to block binding intracellular signalling surface cell receptors of T cells to tumour cells, thereby enabling indirect manipulation of T cells to combat cancer. In contrast, active approach involved direct manipulation of T cells in vitro. While adoptive cell transfer remains the oldest, wherein T cells are isolated from the body and cultured and genetically modified for specificity towards tumour associated antigens (TAAs) and subsequently reintroduced to the patient. A similar approach is undertaken with cancer vaccines, wherein TAAs are indentified and are co-administered to stimulate immune response, sometimes in the context of professional antigen presenting cells (APCs) such as dendritic cells (DCs) [5] or viral vectors as in the case of viral vaccines [6].