Immunostaining intensity for 3- Nitrotyrosine (3-NT, a marker for oxidative damage) increased during in vivo infection with C. rodentium. VIP treatment for day 5–14 and 5–10 alleviated the increase (p<0.01 and p<0.001), whereas VIP treatment for day 10–14 had less effect (Fig 8B), mirroring the effect on caspase-3 stain (Fig 8A). Here, CASP3 is linked to infection.