Abstract
Purpose :
The periocular mucosa (POM) is one of the most exposed mucosal surfaces in the human body, encountering pathogens like SARS-CoV-2 on a regular basis. However, due to the critical function of the eye, it has developed a powerful and timely immune response to prevent immune-related injury, that can be seen in both local and distant tissues. Utilizing a murine-specific respiratory coronavirus (MHV-1), we sought to explore the systemic effects of topical 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 periocular mucosa. Local and systemic tissues including the conjunctiva, nasal-associated lymphoid tissue (NALT), submandibular lymph nodes (SMLN) and spleen were collected from 8 to 12-week-old mice. Mice were examined 1, 4, 7 and 14 days-post infection (dpi) to characterize the time-course of the immune response and leukocyte-specific differences. Single cell-suspensions were prepared from tissues and stained with a cocktail of leukocyte antibodies. Cells were analyzed using flow cytometry to identify changes in cell populations within tissues collected between infected and vehicle mice.
Results :
Mice exposed to 5,000 pfu of MHV-1 were monitored daily for clinical signs of infections. No signs of clinical infection were observed. Compared to the vehicle, MHV-1 infected A/J mice demonstrate a shift in leukocyte populations as early as 1dpi. Locally, at 7dpi, a significant increase in cytotoxic T cells (CD3+CD8+) is observed in the conjunctiva (p<0.01) and a significant increase of B cells (CD3-B220+) in the NALT (p=0.01). Furthermore, at 4 and 7dpi, the SMLN and spleen demonstrate a significant increase of myeloid cells (CD3-CD11b+) (p<0.001, p<0.05). Across all tissues collected, an upregulation of several activated leukocytes including B cells and T cells is observed and an increase of virus-specific T cells (CD3+CD8+CD11b+).
Conclusions :
Our results highlight that topical ocular exposure to MHV-1 induces a robust and potentially specific immune response that is measurable both locally (conjunctiva and NALT) and systemically (SMLN and spleen). Importantly, no signs of ocular or respiratory illness were observed, highlighting the effective pathogen clearance from the eye and immune inductive capabilities.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.