Differences in the susceptibility of herpes simplex virus types 1 and 2 to modified heparin compounds suggest serotype differences in viral entry

Abstract

Although heparan sulfate (HS) serves as an initial receptor for the binding of both herpes simplex virus type 1 (HSV-1) and HSV-2 to cell surfaces, the two serotypes differ in epidemiology, cell tropism, and ability to compete for viral receptors in vitro. These observations are not necessarily contradictory and can be explained if the two serotypes recognize different structural features of HS. To compare the specific features of HS important for the binding and infection of HSV-1 and HSV-2, we took advantage of structural similarities between heparin and cell surface HS and compared the abilities of chemically modified heparin compounds to inhibit plaque formation. We found that the antiviral activity of heparin for both serotypes was independent of anticoagulant activity. Moreover, specific negatively charged regions of the polysaccharide, including N sulfations and the carboxyl groups, are key structural features for interactions of both HSV-1 and HSV-2 with cell surfaces since N desulfation or carboxyl reduction abolished heparin's antiviral activity. In contrast, 6-O sulfations and 2-,3-O sulfations are important determinants primarily for HSV-1 infection. The O-desulfated heparins had little or no inhibitory effect on HSV-1 infection but inhibited HSV-2 infection. Using a series of intertypic recombinant mutant viruses, we found that susceptibility to O-desulfated heparins can be transferred to HSV-1 by the gene for glycoprotein C of HSV-2 (gC-2). This supports the notion that the envelope glycoproteins of HSV-1 and HSV-2 interact with different affinities for different structural features of heparin. To determine if the modified heparin compounds inhibited plaque formation by competing with cell surface HS for viral attachment, binding studies were also performed. As anticipated, most compounds inhibited binding and plaque formation in parallel. However, several compounds inhibited the binding of HSV-1 to cells during the initial attachment period at 4؇C; this inhibitory effect was reversed when the cells and inoculum were shifted to 37؇C. This temperature-dependent differential response to modified heparin compounds was evident primarily when glycoprotein C of HSV-1 (gC-1) was present in the virion envelope. Minimal temperaturedependent differences were seen for HSV-1 with gC-1 deleted and for HSV-2. These results suggest differences in the interactions of HSV-1 and HSV-2 with cell surface HS that may influence cell tropism.

Viral entry mechanisms: cellular and viral mediators of herpes simplex virus entry

“…Another interesting property of 3-OS HS is that HSV-2 gD fails to use it as a receptor for entry [7]. Indeed, even for the attachment process, HSV-2 demonstrates many differences in the HS structure recognition than HSV-1 [33]. It remains to be determined whether the inability to use 3-OS HS and additional differences in HS binding may have a role in the tissue tropism shown by the two HSV serotypes.…”

Cell surface heparan sulfate and its roles in assisting viral infections

“…For example, recent studies about the role of HS in assisting HSV-1 infections suggest that highly sulfated HS interacts with viral glycoprotein C and glycoprotein B, and is essential for the binding of virus to cells. 11,12 It has also been observed that a specific 3-O-sulfated HS interacts with viral glycoprotein D, which is critical for viral entry. These results suggest that the saccharide structures of HS have different activities in promoting viral infections, and understanding the structural specificity for viral infections is essential for antiviral drug development.…”

“…13,14 In addition, such structural variations of HS might provide the tissue-specificity for the viral bindings as suggested by the recently published results on herpes simplex viral attachment and infection. 11,12 However, unlike proteins or DNA, structural analysis of HS is very difficult as there are no general methods for characterizing these molecules. Combining the techniques from virology, carbohydrate biochemistry, molecular biology/genetics, and mass spectrometry, it becomes possible to rapidly investigate the specific roles of HS in assisting viral infections.…”

“…Structural analysis of gC-binding HS, as well as the study about the inhibition effect of chemically modified HS on the infection HSV-1 suggest that a specific saccharide sequence might be necessary for the binding of gC to HS. 11,12 It is also interesting to note that chondroitin sulfate assists HSV-1 infection in an L-cell mutant that is defective in the biosynthesis of HS. 98 It is important to emphasize that wild type CHO cells and swine testis cells are resistant to HSV-1 infection, despite the fact that binding of HSV-1 appears to be normal.…”

Heparin prevents Zika virus induced-cytopathic effects in human neural progenitor cells

“…This has already been proposed for the treatment of both hepatitis C (He et al, 2015) and Ebola virus (Sakurai et al, 2015) infections. Heparin, the widely used anticoagulant, has potentially attractive features including activity against attachment and entry of the enveloped viruses, human simplex (HSV) (Herold et al, 1996;Nahmias and Kibrick, 1964), human immunodeficiency (HIV) (Baba et al, 1988), SARS coronavirus (Vicenzi et al, 2004), and influenza (H5N1) . Here, we explore the effects of heparin on ZIKV infection in human neural progenitor cells (hNPCs) with particular regard to virus replication and induction of cytopathic effects (CPE) resulting in cell death.…”