These results suggest that the viral load administered to the mice
is able to infect all the organs, including placenta and decidua;
however, in contrast to the effect observed with poly(I:C), the viral
infection in the placenta and decidua did not seem to have an effect
on pregnancy outcome. To better understand the differences between
the two responses [virus versus poly(I:C)], we evaluated the
cytokine/chemokine profile in the placenta and spleen of mice
infected with MHV-68. MHV-68 infection did not induce the production
of chemokines and inflammatory cytokines seen with poly
(I:C) administration (Fig. 2C, 2D). Moreover, we observed inhibition
on the production levels of IL-6, MIP-1b, and RANTES in
the placenta of MHV-68–infected mice. These data suggest that
the change in the cytokine profile may play an important role in
the induction of preterm labor/delivery