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bHerpes simplex virus (HSV) and many other viruses, including HIV, initiate infection of host cells by binding to glycosaminoglycan (GAG) chains of cell surface proteoglycans. Although GAG mimetics, such as sulfated oligo-and polysaccharides, exhibit potent antiviral activities in cultured cells, the prophylactic application of these inhibitors as vaginal microbicides failed to protect women upon their exposure to HIV. A possible explanation for this failure is that sulfated oligo-and polysaccharides exhibit no typical virucidal activity, as their interaction with viral particles is largely electrostatic and reversible and thereby vulnerable to competition with GAG-binding proteins of the genital tract. Here we report that the cholestanol-conjugated sulfated oligosaccharide PG545, but not several other sulfated oligosaccharides lacking this modification, exhibited virucidal activity manifested as disruption of the lipid envelope of HSV-2 particles. The significance of the virus particle-disrupting activity of PG545 was also demonstrated in experimental animals, as this compound, in contrast to unmodified sulfated oligosaccharide, protected mice against genital infection with HSV-2. Thus, PG545 offers a novel prophylaxis option against infections caused by GAG-binding viruses. Since the original finding of WuDunn and Spear (1) that ubiquitous and negatively charged glycosaminoglycan (GAG) chains of cell surface proteoglycans provide the binding sites for attachment of herpes simplex virus (HSV) to cells, these oligosaccharides have been reported to assist infection of cells by a number of different viruses, including respiratory syncytial virus (RSV) (2, 3), HIV-1 (4), and Ebola virus (5). In HSV, glycoprotein C (gC) (6) and/or gB (7) mediates virus binding to cell surface GAGs. Sulfated polysaccharides and other polysulfonated compounds that mimic the structure of GAG chains are well-known inhibitors of the virus-GAG interaction in cultured cells (3,8,9). Due to extensive sulfonation, these compounds efficiently outcompete the binding of cell surface GAGs to the viral attachment proteins, thus preventing infection of cells. Notably, the same GAG mimetics can inhibit infectivity of different 9). In spite of potent antiviral activity in cultured cells, these inhibitors, i.e., cellulose sulfate, carrageenan, and PRO2000 (sulfonated poly-naphthalene), failed to protect women against contraction of HIV when tested as intravaginal virucides in several large clinical trials (10-12). Furthermore, there was an indication that one of these GAG mimetics, i.e., cellulose sulfate, increased the risk of contracting HIV (10). Although it is unclear why these compounds lack protective effects in humans (12, 13), some intrinsic features of the virus-GAG interaction, such as reversibility of the binding, may help to elucidate this issue. Virus binding to ubiquitous cell surface components, such as GAGs or sialic acid, has to be neatly balanced to avoid redundant dead-end interactions resulting in trapping of viral particles. Some...

Replication-selective oncolytic adenoviruses have proven safety records with promising clinical outcomes. However, strategies to improve efficacy are still required. Here we report greatly improved antitumor efficacy for both attenuated (dl1520) and highly potent (dl922–947) oncolytic mutants in combination with the current standard of care for late-stage hormone-independent prostate cancers, mitoxantrone or docetaxel. In agreement with previous reports, dl922–947 had superior potency compared with dl1520 both as a single agent and in combination with cytotoxic drugs. The dl922–947 mutant caused significant synergistic cell killing in both drug-insensitive and -sensitive prostate cancer cell lines, PC3 and DU145, respectively, when combined with docetaxel or mitoxantrone. The magnitude of the synergistic response was greatest for dl1520 whereas overall efficacy was greatest for dl922–947, and the latter was also more efficacious in vivo in prostate cancer models. In DU145 and PC3 cells increased viral uptake (up to 9- and 8-fold, respectively), E1A expression, and altered cell cycle progression contributed to the synergistic cell killing. A similar trend was also detected in LNCaP cells. Potent E1A expression was essential for the response. In murine xenograft models (DU145 and PC3) tumor growth inhibition was improved when suboptimal doses of docetaxel and viral mutants were combined. These findings demonstrate that the efficacy of highly potent oncolytic mutants such as dl922–947 that target the retinoblastoma protein (pRb) pathway could be further enhanced even with low drug doses, and support the deletion of the E1ACR2 region in future candidate adenoviruses for treatment of hormone-independent prostate cancers.

Variants of herpes simplex virus type 2 (HSV-2) generated by virus passage in GMK-AH1 cells in the presence of the sulfated oligosaccharide PI-88 were analyzed. Many of these variants were substantially resistant to PI-88 in their initial infection of cells and/or their cell-to-cell spread. The major alteration detected in all variants resistant to PI-88 in the initial infection of cells was a frameshift mutation(s) in the glycoprotein G (gG) gene that resulted in the lack of protein expression. Molecular transfer of the altered gG gene into the wild-type background confirmed that the gG-deficient recombinants were resistant to PI-88. In addition to PI-88, all gG-deficient variants of HSV-2 were resistant to the sulfated polysaccharide heparin. The gGdeficient virions were capable of attaching to cells, and this activity was relatively resistant to PI-88. In addition to having a drug-resistant phenotype, the gG-deficient variants were inefficiently released from infected cells. Purified gG bound to heparin and showed the cell-binding activity which was inhibited by PI-88. Many PI-88 variants produced syncytia in cultured cells and contained alterations in gB, including the syncytium-inducing L792P amino acid substitution. Although this phenotype can enhance the lateral spread of HSV in cells, it conferred no virus resistance to PI-88. Some PI-88 variants also contained occasional alterations in gC, gD, gE, gK, and UL24. In conclusion, we found that glycoprotein gG, a mucin-like component of the HSV-2 envelope, was targeted by sulfated oligo-and polysaccharides. This is a novel finding that suggests the involvement of HSV-2 gG in interactions with sulfated polysaccharides, including cell surface glycosaminoglycans.It is well-established that cell surface heparan sulfate (HS) chains provide the binding sites for the initial interactions with cells of many viruses, including herpes simplex virus type 1 (HSV-1) and HSV-2 (38). The two types of HSV differ in their interactions with HS with respect to both the viral glycoproteins and the HS motifs involved. In particular, glycoprotein C (gC) of HSV-1 was identified as a component of the viral envelope that interacts with HS/heparin chains, thus mediating the attachment of the virus to cells (15). Although gC of HSV-2 can bind to HS/heparin chains and was found to be responsible for several HSV type-specific differences, such as polycation (28) and the hypertonic medium (36) resistance of HSV-2 infection of cells, this protein did not mediate HSV-2 attachment to cells (11). Instead, gB, another HS-binding component of the HSV envelope, was identified as the major virus attachment protein (5). In addition to gB and gC, gD of HSV-1, but not its HSV-2 homolog, can bind to HS chains modified by several isoforms of 3-O-sulfotransferase (31), an interaction that triggers HSV-1 entry into cells. Thus, interaction of HSV with HS seems to be a complex process that involves several kinds of viral proteins promoting virus attachment to and entry into cells.Compounds such as sulfa...