PTGER3 and infection: In contrast, IBV-EP3-S1 (17–451 aa), IBV-20884-21335 (179–323 aa), and IBV-20884-21717 (179–451 aa) displayed markedly delayed and reduced growth phenotypes compared to IBV-P65, with titers approximately 100-fold lower than those of IBV-P65 at 24 h post-infection (Figure 3B).