Immunization, Vaccines and Biologicals

WHO informal consultation: Development of viral vectored vaccines for HIV, malaria, tuberculosis and other indications

Geneva, 1-2 October 2013

Abstract

Novel vaccines for the prevention or treatment of infectious diseases such as HIV, HCV, malaria, TB as well as various oncology indications are a major unmet need. Pre-clinical and clinical evidence supports the role of T cell immunity and in particular CD8+ T-cells in the clearance of intracellular pathogens and tumour cells. Efficient induction of CD8+ T-cell responses against a given antigen follows intracellular delivery of the gene encoding for the antigen along with suitable pathogen-derived innate activators, thereby mimicking the native pathway of antigen processing and MHC class I presentation. The use of replication deficient viruses as antigen delivery vectors has been shown to be a safe and robust mechanism to induce both effector cell mediated and humoral immunity, and priming with these vectors can improve magnitude, quality and durability of those responses.

In the ten years since the WHO last convened a meeting of experts to consider the development, production and quality control of viral-vectored vaccine candidates for development, the field has progressed greatly. The lead candidate vaccines in HIV and tuberculosis include viral vectored vaccines, and such vectors also form a major part of the malaria vaccine pipeline. Other pathogens with active viral vectored vaccine approaches under evaluation include dengue virus, influenza virus, ebola virus, hepatitis C virus, respiratory syncytial virus and many others. The list of recombinant viral vectors in pre-clinical and clinical development has expanded and many thousands of subjects have been enrolled in Phase II and Phase III clinical trial programmes in multiple disease areas with recombinant adenovirus and pox viruses being the most advanced platforms.

Given the large number of candidates now in clinical studies, there is a need for guidance for vaccine manufacturers to identify appropriate regulatory pathways, development gaps and critical data sets to support the advancement of viral vector based vaccines to licensure. Key leaders from academia, biotech and industry together with clinical scientists and regulatory agencies from the EU, USA and Canada were convened with the objective to review progress in developing viral vectored vaccines and related regulatory considerations.

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