Lignin/alginate biomaterials as a promising complementary approach in ocular chlamydial infection.

BACKGROUND

Ocular infection with Chlamydia trachomatis remains the leading infectious cause of preventable blindness worldwide. While antibiotic-based strategies have significantly reduced disease burden, sustained control in endemic regions still relies on repeated treatments, highlighting the need for complementary, locally acting approaches that reduce treatment burden and systemic exposure.

METHODS

We evaluated a lignin-based biomaterial formulation, dehydrogenation polymer lignin in alginate (DHP/Alg), in ocular systems in vitro and in vivo. Anti-chlamydial activity was first assessed in human ocular epithelial (IM-HConEpiC) cells infected with C. trachomatis serovar B. In vivo efficacy was then tested in a guinea pig model of ocular infection using Chlamydia caviae. Bacterial burden was quantified by qPCR and by enumeration of chlamydial inclusions in cell culture, while disease progression was monitored using clinical pathology scoring.

RESULTS

DHP/Alg treatment significantly reduced chlamydial inclusion numbers in ocular epithelial cells in vitro in a dose-dependent manner without inducing cytotoxicity. In contrast, no reduction in bacterial load was observed in vivo at any time point. However, a transient improvement in pathology scores was detected in animals receiving a high infectious dose, suggesting an effect on host responses rather than direct bacterial clearance. Both qPCR and culture-based measurements yielded consistent results across treatment groups.

CONCLUSIONS

These findings demonstrate that, although DHP/Alg retains anti-chlamydial activity in vitro, these effects did not translate into a measurable reduction in bacterial burden in vivo under the conditions tested. Instead, the formulation appears to reduce disease severity, particularly at high pathogen loads. Together, these observations suggest that lignin-based biomaterials may exert their effects primarily at the host-pathogen interface and support further investigation of their use as locally acting adjuncts to, rather than replacements for, conventional antibiotic therapy.