Herpes simplex virus type 1 variants arising after selection with an antiviral carrageenan: Lack of correlation between drug susceptibility and syn phenotype

Abstract

Natural carrageenans of diverse structural types isolated from the red seaweed Gigartina skottsbergii were recently identified as potent and selective inhibitors of herpes simplex virus types 1 and 2 (HSV-1 and -2). The mu/nu-carrageenan 1C3 was tested in vitro for its ability to select resistant variants. After serial passages of HSV-1 strain F in Vero cells in the presence of increasing concentrations of 1C3, viruses emerged that were approximately 2- to 10-fold more resistant to 1C3 inhibition than parental virus; these viruses formed large plaques with an altered syncytial phenotype (1C3-syn). Plaque-purified syncytial variants isolated from passages 13 and 14 have shown variable levels of resistance to 1C3, as well as to the other antiviral carrageenans isolated from G. skottsbergii and to other sulfated polysaccharides with known antiviral activity, such as heparin and dextran sulfate 8000, but all the clones were susceptible to acyclovir. The syn phenotype was not related to polysaccharide resistance. All the 1C3-syn variants formed large syncytia in Vero and CV-1 cells but did not induce fusion in other cell types. The growth efficiency in Vero cells, as well as the virulence for mice by intracerebral or intraperitoneal inoculation of 1C3-syn variants, showed no significant alterations in comparison with the parental virus. The syncytial properties were not affected by cyclosporine or melittin, suggesting that an alteration on glycoprotein gB could be responsible for the syn phenotype induced by 1C3.

Herpes Simplex Virus Type 2 Glycoprotein G Is Targeted by the Sulfated Oligo- and Polysaccharide Inhibitors of Virus Attachment to Cells

“…Variants of HSV-1 resistant to heparin (12,29) or carrageenan (4) produced syncytia in cultured cells due to mutations in gK (29) or the gB endodomain (12) or were predicted to contain an alteration(s) in gB (4). However, in line with our results obtained with PI-88-selected variants of HSV-2, the syncytium-inducing mutations in gB were not found to contribute to HSV-1 resistance to heparin (12) or carrageenan (4). The problem of frequent selection of syncytium-inducing mutants of HSV by sulfated polysaccharides and an unexpected lack of contribution of this phenotype to the drug resistance of the virus are difficult to explain.…”

“…PI-88 also shows anti-dengue and -encephalitic flavivirus (18) and anti-malarial (1) activities. One approach to further explore the interaction of HSV with HS chains has been the analysis of HSV-1 mutants resistant to sulfated oligo-and polysaccharides, such as heparin (12,29) and carrageenan (4). Furthermore, our recent analysis of HSV-1 variants resistant to the sulfated oligosaccharide PI-88 revealed that this compound specifically targets the mucin-like region at the amino-terminal portion of viral gC (7).…”

Polysaccharides from Red Algae: Genesis of a Renaissance

“…After the viral selection and cloning, all the variants showed a syncytial phenotype on Vero cells, this phenotype was also observed on mouse lung and genitals primary cell cultures [74,75]. In order to characterize the obtained viral variants, the susceptibility to CGNs was assessed.…”

Antiviral polysaccharides isolated from Hong Kong brown seaweed Hydroclathrus clathratus

“…Antiviral activity of polysaccharides was tested using cytopathic effect (CPE) reduction assay [11] and plaque reduction assay (PRA) [12] . In these assays, confluent Vero cells were infected with HSV-2 at multiplicity of infection (MOI) of 10 3 TCID 50 /mL or 80 plaque formation unit (PFU)/well respectively.…”