Viruses: As mediators in “Élan vital” of the “creative” evolution

Abstract

The understanding of the processes occurring in Nature has been a continuing concern throughout the history of mankind. Intellectual tools employed towards this goal were specific for each period and have been largely based on the prevailing paradigms that reigned in the past. In this work we present evidence that supports the idea of viruses as key agents mediating natural processes linked to the evolution of organisms, particularly those involved in the flux of genes in the environment. This point of view tinges our perception of Nature and prompts us to include “viral” creativity and plasticity among the tools we employ to analyze those processes far beyond actual paradigms. Experimental data to support this proposal arose during the study of the interaction of the human pathogen, herpes simplex virus (HSV) with sulfated polysaccharides during multiplication of the virus in vitro. Sulfated polysaccharides are the main chemical structures found in carrageenans (CGNs) that are natural products obtained from seaweeds, which proved to be strong inhibitors for the virus. Here we describe the interaction between virus and CGNs as a suitable scenario for the emergence of viral variants which proved to be markedly attenuated for mice. A striking feature of these variants is that they showed changes at the level of conserved regions of the genome such as the DNA polymerase and thymidine kinase genes. In view of these findings, the importance of HSV evolution towards attenuated variants by the action of polysaccharides is also discussed. Attenuation may be considered part of a natural evolutionary process enabling the virus to contribute with valuable information for the host.