In the murine intranasal model of infection, mice infected with 107 p.f.u. vH1, v176-WT, v176-NHA or v176-CHA all showed loss of body weight (Fig. 5a, upper panel) and signs of illness (Fig. 5a lower panel); however, from day 4 p.i. there was a significant attenuation (P<0.05) of v176-WT and v176-CHA compared with vH1 and v176-NHA. Here, TCFL5 is linked to infection.