U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska

 

Date of this Version

December 2006

Comments

Published in CLINICAL AND VACCINE IMMUNOLOGY, Dec. 2006, p. 1322–1327.

Abstract

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.

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