TJP1 and infection: Reverse transcription (RT)-PCR analysis (Table 3) revealed that NE infection sharply downregulated (P < 0.05) the expression levels of claudin-3 (CLDN-3) and zona occludens-1 (ZO-1) genes and upregulated (P < 0.05) the myosin light chain kinase (MLCK)-gene mRNA expression in the jejunum compared with the expression in non-infected birds.