COL2A1 and infection: These results were consistent with the suggested role of ∆gG-ILTV in modulating leukocyte migration to the site of infection (27) and warrant further investigations in vivo. Upregulation of several collagen genes (COL9A3, COL2A1, COL9A1, and COL28A1) in the ∆gG-ILTV-infected TOCs was different from the observations of Luo et al., who reported downregulation of collagen- and myosin-related genes in the trachea of chickens immunized with a different chicken embryo origin ILTV vaccine.