Effects of immunostimulatory CpG ODN on experimental allergic conjunctivitis caused by aspergillus fumigatus

Background: Researches demonstrated that CpG ODN, a immunostimulatory sequences, has preventing and treating effect on allergic conjunctivitis caused by protein allergen. However, its effect on allergic conjunctivitis caused by fungal allergen is unclear. Objective: This study aimed to investigate into whether the Th1-Th2 switching immunostimulatory CpG ODN could reverse the response in the murine allergic conjunctivitis model caused by aspergillus fumigatus. Methods: A mixture of spores and hyphae of aspergillus fumigatus strain was used to induce allergic conjunctivitis in male BALB/C mice aged 6-8 weeks. This experiment was designed into preventive or therapeutical treatment program. Under both settings, allergic conjunctivitis of the animals were treated with CpG ODN ,nonstimulatory GpC ODN or PBS. After the last challenge with the allergen, the clinical symptoms of the animals, were scored based on the criteria of Magone. The animals were sacrificed and the histopathological examination of conjunctiva was performed. Expression of TLR4 mRNA in conjunctiva was analyzed bv real-time PCR assay. The responsiveness and populations of lymphocytes in spleen and draining lymph nodes were analyzed by flow cytometry. The use complied with the Standard of Association for Research in Vision and Ophthalmology. Results: In the prevention mode, CpG ODN decreased subconjunctival infiltration compared with GpC ODN and PBS groups with the average neutrophil count index (21.25 ± 11.59/section, 30.75 ± 11.44 section and 69.00 ± 9.90/section, respectively). Expression of TLR4 mRNA was up-regulated significantly by CpG ODN. The clinical scores for CpG ODN group were insignificantly lower than those in GpC ODN group and PBS group (P > 0.05). In the therapeutic mode, compared with GpC ODN and PBS groups, the allergic symptom score in CpG ODN group manifested significantly lower(t=4.000, t=2.750, P < 0.01) and showed fewer cellular infiltration (t=4.870, t=3.829, P < 0.01) and higher expression of TLR4 mRNA (P < 0.01). In cultured splenic and draining lymph node cells, increased percentages of CD4⁺CD25⁺ and CD4⁺CD25⁺CD69⁺ in CpG ODN group were observed compared with control groups (P < 0.05). Conclusion: CpG ODN can relieve aspergillus fumigatus-induced allergic conjunctivitis via either subconjunctival injection or topical application by upregulating expression of TLR4 and activating Treg lymphocytes.