Abstract
To identify antigens unique to live Pasteurella multocida P1059, 10 week old
specific pathogen-free (SPF) chickens were vaccinated three times with one of the
following: viable cells from P. multocida P1059, 3865, 3866, or cells from
formalin-killed strain PI059 or formalin-killed strain P1059 that were opsonized with
antiserum directed against killed strain PI059 prior to immunization. Vaccinated
birds were challenged with 1.5 x 107 CPU of live strain P1059. Eight, 71, 86, and
50% of the birds that received live strains P1059, 3865, 3866 and killed strain P1059
(respectively), exhibited clinical signs of fowl cholera. Antisera directed against live
strain PI059 recognized 23 proteins ranging from 14- to 92-kilodaltons (kDa); 20 of
which were adsorbed by strain 3865. The molecular masses of the three remaining
proteins were 25-, 30- and 43-kDa.
A genomic library of strain P1059 was constructed using the plasmid vector
pUC-19 and screened with antisera against live strain P1059; 12 out of 4,100 clones
were recognized. The inserts of the plasmids from these clones ranged from 0.48-
to 6.S-kilobases (kb) in length. Five of the 12 clones expressed proteins with
molecular masses of 34-, 37-, 42-, 46- and 55-kDa. Escherichia coli CSR603(pOP43-
2G) and CSR603(pOP33-SF) expressed proteins recognized by antisera directed
against live strain P1059. E. coli CSR603(pOP43-2G) expressed an epitope(s) which
was recognized by antisera directed against strains 3865 and 3866.
Conditions for transformation were optimized and attempts were made to
create a shuttle vector in order to establish a cloning system for gene expression in
P. multocida. The highest efficiency of transformation (1.25 x 10 7 CFU/p.g DNA)
was obtained when 7.6 x 1010 cells of P. multocida R473 were electroporated at 12.5
kV cm-1 for 10 ms with 5 ng of the plasmid, p VM109. Of the six strains tested,
representing serogroups A, B, D and E, all were transformed successfully. Vectors
including pBR322, pUC19, pJFF224-NX and pSP329 were unable to transform P.
multocida. To create a shuttle vector for gene expression in P. multocida, a
Pasteurella plasmid (pLAR-1) was cloned in both orientations into the BamH I site
of pBR322. These plasm ids, pLRBR .. 21 and pLRBR-67, had a transformation
efficiency of 4.5 to 8 x 104 CFU/μg of DNA in strain R473. Chromosomal DNA
containing the Brucella abortus copper-zinc superoxide dismutase gene was cloned
into the Cia I site of pLRBR-21. The 1.8-kb fragment encoding a 42-kDa
Pasteurella protein was cloned into an additional unique site (Nru 1) of pLRBR-21
to determine if this plasmid was a viable shuttle vector for gene expression in P.
multocida.
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