Haller, University of Freiburg, Freiburg, Germany), human α-defensins, or isotype control. Three selective areas of oral epithelium: upper, middle, and lower parts of each tissue specimen were counted for MxA positive cells. The immunoreactivity of MxA staining was given a semiquantitative score ranging from score 1–3. Score 1 = the area of positive cells was less than 10% in the counting field, score 2 = 10–50%, and score 3 = more than 50%. Nontoxic concentrations of different antimicrobial peptides

for HGECs were predetermined as assessed by cell viability (MTT assay and Trypan blue exclusion). HGECs, normal human bronchial epithelial cells (Clonetics) PKC inhibitor and primary human microvascular endothelial cells (Clonetics) were treated with nontoxic doses of either α-defensin-1 (10 μM); α-defensin-2 (10 μM); α-defensin-3 (10 μM); β-defensin-1 (10 μM); β-defensin-2 (10 μM); β-defensin-3 (0.5 μM); LL-37 (2 μg/mL); or IFN-α (100 U/mL). After 6 h of treatment with antimicrobial peptide or cytokine, mRNA expression of MxA was analyzed.

In neutralization find more experiment, cells were treated with α-defensin-1 or IFN-α in the absence or presence of neutralizing antibodies against IFN-α (400 neutralization unit/mL) and IFN-β (400 neutralization unit/mL). After 24 h of treatment, immunohistochemical analysis of MxA protein was carried out. H5N1 virus (A/open-billed stork/Nahkonsawan/BBD0104F/04) was isolated from cloacal swabs of live Asian open-billed storks between 2004–2005 and propagated in Madin-Darby canine kidney cells using MEM (Gibco, Grand Island, NY, USA) supplemented with 10% FBS (Hyclone, Logan, UT, USA) and penicillin and streptomycin [[48]]. The sequence

data of the virus was submitted to GenBank with accession numbers DQ989958. The virus was grown in Madin-Darby canine kidney cells and the titer of virus stock was determined as described previously Lck [[48]]. All experiments with H5N1 virus were performed in a Biosafety Level 3 facility (Mahidol University) by trained researchers. HGECs (40,000 cells/well) were treated with either α-defensin-1 (10 μM); α-defensin-2 (10 μM); α-defensin-3 (10 μM); β-defensin-1 (10 μM); β-defensin-2 (10 μM); β-defensin-3 (0.5 μM); LL-37 (2 μg/mL); or IFN-α (100 U/mL) for 24 h. They were washed two times and then co-cultured with H5N1 virus at MOI 1 (1 PFU/cell). After 1 h, the inoculum virus was removed and the HGECs were washed two times with PBS and cultured with fresh medium. Virus titers in culture supernatants and cytopathic effect were determined 48 h postinfection. To assess the number of infectious particles (plaque titers) in cell culture supernatants, a plaque assay using Avicel (RC-591, FMC Biopolymer, Germany) was performed in 96-well plates [[49, 50]].