FIG 8.

“Original antigenic sin” model. (A) In this model, we suggest that it is crucial in which order paramyxo- and pneumoviruses are encountered to develop cross-immunity to the highly pathogenic henipaviruses (or other paramyxoviruses). (B) Initially committing T cell immunity to epitopes present in pneumoviruses or MeV could lead to a relative narrow immunity and therefore no protection and death upon encountering a highly pathogenic virus. (C) Encountering HPIV2 or -3 before MeV vaccination or infection could lead to committing to broadly reactive T cell epitopes and therefore (partial) immunity to highly pathogenic viruses.