@Txdg00 - Yes, but it's expensive and (comparatively) slow; it thus will NOT be used on a mass basis prior to giving people jabs.

It also won't tell you WHERE the cross-reaction is. There's no way to know whether it matters at present, but the presumption from this paper is that nucleocapsid reaction is where you get the best protection; whether you get effective protection from spike recognition is much less-certain. I would not expect you do, simply because it takes TIME for the immune system to detect and attack a thing, and unfortunately the spike does its job VERY rapidly. Viral replication, on the other hand, requires about 10 hours for a cycle which is plenty of time.

Note that the time required for blood to circulate is approximately one minute (heart -> heart); add to this the enzyme activation and mobilization time once "detection" has occurred before the various defensive mechanisms associated with that (macrophages, etc) are loosed and get to the correct location. 10 hours is a long time and plenty, but the few minutes (if that) required for the spike to penetrate may not be enough. As such I would expect that T-cell recognition to the spike is much less-protective than recognition of the nucleocapsid sections of the virus, simply on the "time in action" during which interdiction can take place.

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