Bovine immune response to shiga-toxigenic Escherichia coli O157:H7.
Although cattle develop humoral immune responses to Shiga-toxigenic (Stx+) Escherichia coli O157:H7, infections often result in long-term shedding of these human pathogenic bacteria. The objective of this study was to compare humoral and cellular immune responses to Stx+ and Stx- E. coli O157:H7. Three groups of calves were inoculated intrarumenally, twice in a 3-week interval, with different strains of E. coli: a Stx2-producing E. coli O157:H7 strain (Stx2+ O157), a Shiga toxin-negative E. coli O157:H7 strain (Stx- O157), or a nonpathogenic E. coli strain (control). Fecal shedding of Stx2+ O157 was significantly higher than that of Stx- O157 or the control. Three weeks after the second inoculation, all calves were challenged with Stx2+ O157. Following the challenge, levels of fecal shedding of Stx2+ O157 were similar in all three groups. Both groups inoculated with an O157 strain developed antibodies to O157 LPS. Calves initially inoculated with Stx- O157, but not those inoculated with Stx2+ O157, developed statistically significant lymphoproliferative responses to heat-killed Stx2+ O157. These results provide evidence that infections with STEC can suppress the development of specific cellular immune responses in cattle, a finding that will need to be addressed in designing vaccines against E. coli O157:H7 infections in cattle.
Hoffman
Mark A
MA
Enteric Diseases and Food Safety Research, National Disease Center, USDA, Agriculture Research Service, Ames, IA 50010, USA.
Menge
Christian
C
Casey
Thomas A
TA
Laegreid
William
W
Bosworth
Brad T
BT
Dean-Nystrom
Evelyn A
EA
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000382:microbiology; D004927:Escherichia coli Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000276:immunology* / Q000378:metabolism / Q000472:pathogenicity; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008213:Lymphocyte Activation; D022641:Shiga Toxin 2 / Q000096:biosynthesis*
D000907:Antibodies, Bacterial; D022641:Shiga Toxin 2