Thus, we choose to restrict our detailed analysis to MOI 2 at 6 h and 9 h p.i. To determine whether infection with MHV-A59 was associated with a general ER stress response in infected DBT cells, we measured the steady-state expression of the ER stress markers, BiP, total Xbp-1 [total Xbp(t) and spliced Xbp(s)], measured by quantifying spliced Xbp-1[ Xbp(s)] with respect to total Xbp-1 mRNA expression, an indication of IRE1 activation (8, 9, 10). The gene discussed is ERN1; the disease is infection.