A Synthetic, Small, Sulfated Agent Is a Promising Inhibitor of Chlamydia spp. Infection in vivo

Abstract

Chlamydia is the most frequently reported sexually transmitted bacteria causing 2.9 million infections annually in the United States. Diagnosis, treatment, and sequelae of chlamydial disease cost billions of dollars each year in the United States alone. Considering that a heparin sulfate-like cell surface receptor is involved in Chlamydia infections, we reasoned that sulfated and sulfonated mimics of heparin sulfate would be useful in topical prophylactic prevention of Chlamydia. In this study, we tested a small, synthetic sulfated agent sulfated pentagalloyl glucoside (SPGG) and three synthetic sulfonated polymers PSS and SPS with average molecular weight in the range of 11 to 1000 kDa for inhibition against Chlamydia. Infection of HeLa cells with C. muridarum or C. trachomatis in the presence of increasing concentrations of SPGG or sulfonated polymers were quantified by immunofluorescence of Chlamydia inclusions. To determine whether in vitro pre-treatment of SPGG inhibits infection of C. muridarum, HeLa monolayers were incubated with SPGG-containing media, and then infected with Chlamydia. Our in vitro results show that SPGG pre-treatment inhibits Chlamydia infection in a dose-dependent manner. In addition, we further determined if SPGG treatment has an inhibitory effect during infection, therefore cell monolayers were infected with C. muridarum in the concurrent presence of SPGG. Our results show that SPGG inhibits C. muridarum infection with an IC50 at 10 μg/ml levels. We also tested the inhibitory effect of synthetic polymers PSS and SPS against Chlamydia and found inhibition of C. muridarum and C. trachomatis infections with IC50 ranging from 0.3 to 0.8 μg/ml. SPGG, PSS, and SPS inhibit formation of Chlamydia inclusions in a concentration-dependent manner. For evaluation of in vivo efficacy of the most effective agent in blocking C. muridarum, SPGG, we intravaginally pre-treated mice with SPGG before infection with C. muridarum. Cervical swabs were collected post-infection to quantify Chlamydia inclusions in vitro. Our in vivo data show that the SPGG-treated group has a statistically significant reduction of infection compared to the no-treatment control. Overall, our results show that SPGG could serve as a promising topical inhibitor for preventing Chlamydia infection.

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

“…Earlier, we have demonstrated that SPGG inhibits HSV [50,51] and Chlamydia infection [66]. Since HSV and Chlamydia are known to exploit heparan sulfate during early stages of host pathogen interactions [66,67], SPGG's lowering of HCMV early gene expression is not too surprising considering that the viral entry is blocked in the first place. A more important point of this result is the possibility that SPGG could be utilizing multiple mechanisms for its antiviral effects.…”

“…This is especially important because Our study is first to report a unique heparin mimetic, which has been previously been reported as a broad spectrum antimicrobial activity, as an inhibitor of HCMV. Earlier, we have demonstrated that SPGG inhibits HSV [50,51] and Chlamydia infection [66]. Since HSV and Chlamydia are known to exploit heparan sulfate during early stages of host pathogen interactions [66,67], SPGG's lowering of HCMV early gene expression is not too surprising considering that the viral entry is blocked in the first place.…”

“…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).…”

“…The variant of SPGG used in this report has defined molecular composition of septa-(6%), octa-(17%), nona-(21%), deca-(45%), undeca-(11%), and dodeca-(3%) sulfated species (average molecular weight 2178; see Al-Horani et al, 2013), which has been reproducibly synthesized and characterized using advanced LC-MS/MS methods. This SPGG variant is most studied variant so far through characterization of anti-thrombotic, anti-HSV and anti-Chlamydia activity profiles [66].…”

Preferential recognition and antagonism of SARS-CoV-2 spike glycoprotein binding to 3-O-sulfated heparan sulfate

“…Likewise, fondaparinux, which has a 3- O -sulfate group, is also a significant inhibitory agent. Of these, SPGG is particularly attractive because of its ease of synthesis, lack of cytotoxicity, and broad spectrum antimicrobial activity ( 42 , 43 , 56 ). SPGG is also an inhibitor of coagulation factor XIa ( 56 ), which would simultaneously induce an anti-coagulant effect without major bleeding risk.…”