Abstract
Purpose::
A common feature of sight-threatening chronic ocular allergic disease is an increased incidence of colonization with Staphylococcus aureus (SA), yet no animal models have been developed to study the contribution of SA to allergic conjunctivitis. The purpose of this study was to create a murine model to study the mechanisms through which SA can impact allergic conjunctivitis.
Methods::
Allergic conjunctivitis was induced using footpad injection with ragweed (RW) extract in alum followed by two ocular challenges (days 11,12) with RW pollen. When SA was used, an extract of SA cell wall (SA-CWE) was applied topically on day 10 and prior to RW challenge (days 11,12). Clinical scores were evaluated 20 min post-challenge (day 12). On day 13, mice were euthanized and heads were removed and fixed, decalcified, and paraffin embedded to facilitate histological examination of intact conjunctiva via hematoxylin and eosin staining.
Results::
Clinical symptom scores were similar in mice receiving SA-CWE ocular challenge prior to RW challenge (compared to RW challenge alone). However, histological examination revealed increased edema and goblet cell hyperplasia in mice receiving SA-CWE prior to RW challenge.
Conclusions::
Co-stimulation of the ocular surface with just three exposures to SA-CWE during acute allergic conjunctivitis increased histological signs of inflammation. A more chronic exposure to SA-CWE (as it would occur in chronic allergic conjunctivitis) could increase the severity of disease and may provide a model for studying both mechanisms of SA activation of the ocular surface as well as chronic ocular allergic disease.
Keywords: conjunctiva • inflammation • Staphylococcus