Emerging viruses and current strategies for vaccine intervention

Abstract

During the past decade several notable viruses have suddenly emerged from obscurity or anonymity to become serious global health threats, provoking concern regarding their sustained epidemic transmission in immunologically naive human populations. With each new threat comes the call for rapid vaccine development. Indeed, vaccines are considered a critical component of disease prevention for emerging viral infections because, in many cases, other medical options are limited or non-existent, or that infections result in such a rapid clinical deterioration that the effectiveness of therapeutics is limited. While classic approaches to vaccine development are still amenable to emerging viruses, the application of molecular techniques in virology has profoundly influenced our understanding of virus biology, and vaccination methods based on replicating, attenuated and non-replicating virus vector approaches have become useful vaccine platforms. Together with a growing understanding of viral disease emergence, a range of vaccine strategies and international commitment to underpin development, vaccine intervention for new and emerging viruses may become a possibility.

Keywords: molecular biology; vaccination; viral.

Figure 1

Virus vector platform technologies. Replication competent but attenuated virus vectors (RHS) deliver heterologous antigen targets resulting in the induction of cellular and humoral responses. Their complement of genes enables a full round of replication and assembly of progeny virus which can amplify and spread the vaccine effect to susceptible cells. While these platforms are based on highly attenuated viral backgrounds, replication competence may lead to the development of mutations and reversion to virulence. Replication defective vectors (LHS) support effective cellular entry and a single round of expression of the target gene / antigen; they result in effective induction of cellular and humoral responses. They are unable to generate new infectious progeny and are considered safer than replication competent vectors.