Inhibition of Human Cytomegalovirus Entry into Host Cells through A Pleiotropic Small Molecule

Elste, James; Kaltenbach, Dominik; Patel, Vraj R.; Nguyen, Max T.; Sharthiya, Harsh; Tandon, Ritesh; Mehta, Satish K.; Volin, Michael V.; Fornaro, Michele; Tiwari, Vaibhav; Desai, Umesh R.

Together, two independent experiments with two different types agents bearing glycoprotein gB, i.e., HCMV virus and CHO-K1 cells, exhibited almost equivalent results for 100 µM SPGG. These results are encouraging and likely support that SPGG binds to glycoprotein gB of HCMV, although its affinity is expected to be weaker (10 to 100 µM). One explanation for this is that the anti-gB antibody and SPGG do not compete ideally for the same site of binding on gB. It is possible that both competitors bind gB simultaneously, albeit in a partially competitive manner, resulting in a less robust competition. Another possibility is that SPGG mediates HCMV inhibition through multiple viral surface receptors, one of which is gB. The foundation for this expectation is that SPGG has been earlier shown to bind tightly to glycoprotein D of HSV [50, 51] . Likewise, SPGG also inhibits Chlamydia infection through binding to its cell surface receptors [66] . Finally, potential pathways that could be targeted by SPGG do exist, e.g., the engagement of one or more host cell surface receptors (e.g., PDGF-R, EGF-R, neuropilin, or others). Of the two, the latter is more likely because heparan sulfate and its mimetics are known to be pleiotropic entities. **** Figure 5 . HCMV-mediated foci formation using plaque reduction assay in presence of SPGG. In the experiment, HFF-1 cells were infected with an MOI of 1.0 of HCMV β-galactosidase-expressing reporter virus strain (RC256) pretreated with 100 µM SPGG or mock-treated in serum free media (SFM). The number of plaques was quantified in both treated and untreated samples and revealed a dramatic decrease in samples pretreated with 100 µM SPGG compared to mock treatment. The graphs are the result of mean values and SD for a N = 3 experiments with triplicates of each conditions. Statistical significance was determined with a T-Test, (****) signifies a P-value of < 0.0001.