What does this mean?

I'll point to a thread of commentary on Twitter but I really can't vouch for anything said in it.

https://twitter.com/Kevin_McKernan/status/145051423062551756...

I Interpret this as: They have confirmed a hypotheses for a immunization pathway, namely through these exosomes.

"These results demonstrate an important role of circulating exosomes with spike protein for effective immunization following mRNA-based vaccination."