CX3CL1 and infection: We now report that there were no differences between groups in baseline production of fractalkine, and on day 4 following in vivo RV16 infection, levels of fractalkine protein in BAL fluid did not increase from baseline in any group of subjects, though there may have been a very small increase in subjects with moderate asthma, although this increase was not statistically significant (Fig 4A, P = 0.162).