Ocular Microbiology and Immunology Group
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2025 OMIG Abstract

Ocular Exposure to a Murine Coronavirus Induces a Subclinical and Protective Immune Response in Mice

Jana Livingston¹, Patricia Azevedo de Lima^1,2, Miranda Mathieson², Che Colpitts², Jacob Rullo<sup>2,3

1</sup>Department of Medicine, Queen's University, Kingston, Ontario, Canada; ²Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada; ³Department of Ophthalmology, Queen's University, Kingston, Ontario, Canada

Purpose: Utilizing a murine-specific respiratory coronavirus (MHV-1), we sought to explore the systemic and protective immunological effects of ocular mucosal exposure to respiratory viruses in the eye.

Methods: A/J mice were inoculated with 5,000 PFU of MHV-1 -- a dose known to cause SARS-like illness in mice, or virus medium (DMEM) via eyedrop to the ocular mucosa. The conjunctiva, submandibular lymph nodes (SMLN) and spleen were collected from 8 to 12-week-old mice, at 1-, 4-, 7- and 14-days post-exposure to characterize the time-course of the immune response and leukocyte-specific differences. Alternatively, 21 or 100-days post-ocular exposure to MHV-1 or DMEM, mice were intranasally exposed to 5,000 PFU of MHV-1 to investigate clinical outcomes.

Results: Mice exposed to 5,000 PFU of MHV-1 via the ocular mucosa were monitored daily for clinical signs of infections. No signs of clinical infection were observed. Compared to the control, ocular exposure to MHV-1 induced a shift in leukocyte populations as early as 1-day post-inoculation. Locally, at 4 and 7dpi, a significant increase in cytotoxic T cells (CD3+CD8+), myeloid cells (CD11b+) and B cells (CD3-B220+) is observed in the conjunctiva (p<0.01). Systemically, at 4 and 7dpi, a significant increase in myeloid cells (CD11b+) and B cells (CD3-B220+) is observed in the SMLN and spleen (p<0.01). Mice were subsequently given a primary ocular dose of MHV-1 followed by a secondary intranasal dose, 21 or 100-days following initial exposure. No significant weight loss was observed and a significantly lower clinical score in the mice who received prior exposure compared to their naïve counterparts (p<0.0002).

Conclusions: Our results highlight that ocular exposure to MHV-1 induces a robust and specific immune response that is measurable both locally (conjunctiva) and systemically (SMLN and spleen). No signs of ocular or respiratory illness were observed post-ocular exposure. Additionally, priming the ocular mucosa with MHV-1 is protective against clinical illness, highlighting the effective pathogen clearance from the eye and immune inductive capabilities.