A 39-kDa capsular protein is a major cross-protection factor as demonstrated by protection of chickens with a live attenuated Pasteurella multocida strain of P-1059.

The aim of this study was to show that a 39-kDa protein or OmpH of Pasteurella multocida strain P-1059 is essential for cross protection. Strain PBA322, a thinly capsulated strain of P. multocida strain P-1059, was used as a live vaccine in chickens.