R. Grogono-thomas et al., Roles of the surface layer proteins of Campylobacter fetus subsp fetus in ovine abortion, INFEC IMMUN, 68(3), 2000, pp. 1687-1691
The role of the surface (S)-layer proteins of Campylobacter fetus subsp, fe
tus has been investigated using an ovine model of abortion. Wild type strai
n 23D induced abortion in up to 90% of pregnant ewes challenged subcutaneou
sly. Isolates recovered from both dams and fetuses expressed S-layer protei
ns with variable molecular masses, The spontaneous S-layer-negative variant
, strain 23B, neither colonized nor caused abortions in pregnant elves. A s
eries of isogenic sapA and recA mutants, derived from 23D, also were invest
igated in this model, A mutant (501 [sapA recA(+)]) caused abortion in one
of five challenged animals and was recovered from the placenta of a second
animal. Another mutant (502 [sapA recA]) with no S-layer protein expression
caused no colonization or abortions in challenged animals but caused abort
ion when administered intraplacentally, Mutants 600(2) and 600(4), both rec
A, had fixed expression of 97- and 127-kDa S-layer proteins, respectively.
Two of the six animals challenged with mutant 600(4) were colonized, but th
ere were no abortions. As expected, all five strains recovered expressed a
127-kDa S-layer protein. In contrast, mutant 600(2) was recovered from the
placentas of all five challenged animals and caused abortion in two. Unexpe
ctedly. one of the 16 isolates expressed a 127-kDa rather than a 97-kDa S-l
ayer protein. Thus, these studies indicate that S-layer proteins appear ess
ential for colonization and/or translocation to the placenta but are not re
quired to mediate fetal injury and that S-lager variation may occur in a re
cA strain.