STAT1α/βand STAT3α/β splice-form activation in mice with MHV-3 induced hepatitis

Objective Signal transducer and activator of transcription 1α(STAT1α) is essential to IFN γ and IFN α regulated gene expression, while STAT1β, an alternate splice form mediates only IFN α dependent gene expression. STAT3α and STAT3β splice forms are also differentially activated in response to cytokines including IL 6, IL 10 and GM CSF. In this report, we studied the host immune response to viral infection with a murine hepatitis model for rates of STAT1α, β and STAT3α, β activation following infection with hepatitis virus in resistant and sensitive mouse strains. Methods Mice were i.p infected with 100 PFU of MHV 3. The mice were killed at required intervals and livers/spleens were immediately frozen in liquid nitrogen. Nuclear extracts were separated in an 8% SDS polyacrylamide gel and proteins were detected by immunoblotting. DNA mobility shift assay was also performed to examine the protein DNA interreaction. Results STAT1 and STAT3 activation in spleen enhanced in 24 hs to 72 hs following MHV 3 infections in both sensitive and resistant mouse strains. However, beyond this time period, ratio of activated α to β splice form for STAT1 and STAT3 enhanced to above 1.0 in resistant A/J mice, while decreased to less than 0.3 in MHV 3 sensitive BALB/c and C3H/HeJ strains. Activated STAT1α/β and STAT3α/β ratio in liver was similar in both resistant and sensitive mouse strains. Conclusion The ratios of activated STAT1α/β and STAT3α/β in mixed leukocytes from spleen predict outcome of MHV 3 infection and may function as an important markers of therapeutic effect for modification of host immune response