Coronavirus induction of class I major histocompatibility complex expression in murine astrocytes is virus strain specific

To investigate the effects of coronavirus infection on MHC class I expression in primary astrocytes~ cultures were routinely used at 20-30 d in vitro, or 6-12 d after mechanical shaking to remove oligodendrocytes and microglia. Fig. 1 shows that A59 induced abundant class I expression in astrocytes, measured by RIA using the Kb-specific mAb AF6.88.5.3. Class I expression was routinely measured on days 3 and 5 p.i. after infection at an m.o.i, of 1, though it was detectable within 24-48 h p.i. K b was preferentially expressed over D b after A59 infection. This was not due to a lack of inducibility of the D b molecule, since both K b and D b were expressed spontaneously with time in culture, and also in response to 100 U/ml of IFN-3/(data not shown). Under these conditions, K b was expressed earlier than D b, and usually at significantly higher levels. In infected astrocytes, the class I-inducing activity of A59 was consistently 30-50% more potent than the single dose of 100 U/ml of IFN-3' (Fig. 2) . Finally, FACS | analyses revealed that K b was expressed on '~50% of the astrocytes in the infected cultures.