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R. Siva Ganesa Karthikeyan, P. Lalitha, V. Prajna, E. Pearlman, K. Dharmalingam; Innate Immunity in Aspergillus and Fusarium Deratitis in Tamil Nadu, India. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2430. doi: https://doi.org/.
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Fungal keratitis constitutes 65% of total corneal ulcers in South India, the majority of which are caused by Fusarium and Aspergillus species. The purpose of this study is to examine innate immunity in corneal tissues from patients with fungal corneal ulcers.
Corneal scrapings were collected for diagnosis from patients between February and July 2009, and categorized as Fusarium or Aspergillus species. Total RNA from the corneal scrapings was extracted by the TRIzol method, and quantitative PCR was performed for expression of TLR (Toll Like Receptor) 2, TLR4, Dectin-1, Dectin-2, IL-1β, IL-8, TNF-α, and IFN-γ. Nine cadaver corneas obtained from Aravind Rotary Eye Bank were used as controls for relative quantification. Histological sections of paraffin embedded infected corneas obtained after transplant during this time period were examined for infiltrating cells.
The total number of patients with corneal ulcers presenting during this period was 519, of which 332 were fungal ulcers (64%). For the current study, 40 patients (21 Fusarium sp and 19 Aspergillus sp) were analyzed by quantitative PCR. We found that expression of TLR2, TLR4, IL-1β, IL-8, and TNF-α was higher in infected corneal tissues compared with controls, whereas there was no difference between control and infected corneas in expression of IFN- or Dectin-2. The histopathological analysis of the infected corneal tissue showed consistent neutrophil and mononuclear infiltration into the corneal stroma. There was no difference in expression of these mediators between patients infected with Fusarium sp and those infected with Aspergillus sp.
Elevated expression of TLRs, Dectin-1 and pro-inflammatory and chemotactic cytokines in infected versus control corneal tissue implicates these mediators in fungal recognition, and recruitment of neutrophils to the infected cornea. These studies will lead to an increased understanding of the host response in fungal keratitis, and may identify novel targets for immunotherapy.
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