Thus, the growth kinetics of wild-type MHV-A59 and MHV-N1348A in macrophages and DCs were indistinguishable. FIG. 3. MHV-N1348A replication in macrophages and DCs. (a) Peritoneal macrophages, a Kupffer cell line, and bone marrow-derived cDCs and pDCs were infected with wild-type MHV-A59 or MHV-N1348A (MOI = 1). Viral titers in supernatants were measured at the … MHV-N1348 meanwhile infection results in elevated IFN-�� expression in pDCs. The control of MHV-A59 in mice is strongly dependent on swift IFN-�� expression by pDCs during the early phase of infection (5). We found no difference in the ability of MHV-N1348A to replicate in pDCs (Fig. (Fig.3);3); however, compared to that for wild-type MHV-A59 infection, IFN-�� production was significantly increased following MHV-N1348A infection (Fig. (Fig.

4a).4a). Notably, neither macrophages nor cDCs produced elevated IFN-�� levels upon MHV-N1348A infection, suggesting that, similar to that for wild-type MHV-A59, immediate IFN-�� expression upon MHV-N1348A infection is still restricted to pDCs. We also assessed if MHV-N1348A replication is more vulnerable to IFN-�� pretreatment than wild-type MHV-A59 replication. Macrophages and cDCs were pretreated with different dosages of IFN-�� and, 4 h later, were infected with wild-type MHV-A59 or MHV-N1348A. As shown in Fig. Fig.4b,4b, the viral titers determined at 18 h p.i. were indistinguishable between wild-type MHV-A59 and MHV-N1348A infections, irrespective of whether the infections were done at low (0.01) or high (1) MOIs. FIG. 4. MHV-N1348A and type I IFNs.

(a) Bone marrow-derived pDCs and cDCs, as well as peritoneal macrophages, were infected with wild-type MHV-A59 (MHV wt) or MHV-N1348A (MOI = 1). The levels of IFN-�� in the supernatants were measured at the indicated … MHV-N1348A is attenuated in livers of IFNAR?/? mice. The phenotypic analysis of MHV-N1348A revealed a profound impact of this mutant virus on the induction of viral hepatitis in mice, and we observed elevated IFN-�� expression in MHV-N1348A-infected pDCs. To clarify if the lack of acute viral hepatitis is related to elevated IFN-�� expression, we infected type I IFN receptor-deficient mice (IFNAR?/? mice) that cannot respond to type I IFNs. MHV-A59 can replicate essentially uncontrolled in IFNAR?/? mice, and these mice succumb to the infection at day 2 p.i. (4). Therefore, at day 2 p.i.

we assessed the viral titers in the spleens and livers and the serum ALT values of IFNAR?/? mice (on the B6 or 129Sv background) that were infected with 5 PFU (i.p.) of wild-type MHV-A59 or MHV-N1348A. As shown in Fig. Fig.4c,4c, wild-type MHV-A59 and MHV-N1348A titers were increased by several orders of magnitude in mice lacking the IFNAR compared Brefeldin_A to those for wild-type mice. However, MHV-N1348A titers did not fully reach those of wild-type MHV-A59 in B6-IFNAR?/? and A129 (IFNAR?/? on the 129Sv background) mice.