Estrategy to obtain attenuated viral variants employing natural compounds

CARLUCCI MJ

Bellaire, Texas

Conferencia; 1st World Virology & Microbiology online Conference; 2012

Target Meeting

Natural carrageenans are widely known as potent and selective antiviral compounds, specially against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), because they possess heparan-like structures that mimic the cell receptor required for virus entry. Frequent use of antivirals against HSV favors the appearance of resistant virus populations. Previous studies shown that viral variants of HSV-1 (F) obtained through several passages on Vero cells with increasing concentrations of the m/n carrageenan 1C3 (precursor of  é and ê carrageenans) extracted from the red seaweed Gigartina skottsbergii did not show neither morbidity nor mortality when C57BL/6 mice were infected via intranasal or intravaginal. New variants of HSV-2 (MS) were obtained using the same protocol with  é and ê carrageenans. To test the phenotypic stability, variants were passaged  5-10 times in Vero cells without compound. These variants exhibited properties similar to those observed for HSV-1 variants when considering: 1) cytopathic action (100% syncytial phenotype ), 2) relative resistance (ratio between IC50 for each variant and the IC50  for the parental strain) to the compounds used during the selective treatment (between 10,5 to 79) and to Acyclovir (between 2 and 10), 3) cellular disemination in vitro and 4) differential cytokine activation (the level of TNF-a, IL-6 and IFN-a were drastically diminished in animals inoculated with syncitial variants). Sequencing of tk genes obtained from variants did not reveal significative changes other than those associated to viral polymorphism. The results obtained support the idea that the strategy employed to obtain HSV variants could probably affect genomic regions that are involved in strain virulence, tropism, immune response and pathology of the host.  Study of virulent and attenuated variants with large and ancestral genomes, may conferee information by accessory genes that act as virokines or viroceptors, some of which appear to have originated from eukaryotic genes. Much information exists about the selection resistant variants obtained from increasing concentration of different antiviral drugs such as acyclovir, foscarnet, ribavirin, heparin. In this work we use natural chemical structures (extracted from red seaweed) similar to cellular components in contact with the virus. Moreover, we describe the characteristics of the asymtomatic variants for human/mammalian application without affecting the natural evolution host-pathogen.