CXCL12 and infection: WT PR8 infection induced higher levels of proinflammatory cytokines, such as TNF-α, CXCL12, and interleukin 6 (IL-6), than infection with the segment 8 reassortant viruses, while the profiles in O175A- and O265B-infected mice were more similar to each other than to the profile in PR8-infected mice (Fig. 7D).