Maternally and Naturally Acquired Antibodies to Shiga Toxins in a Cohort of Calves Shedding Shiga-Toxigenic Escherichia coli

Abstract

Calves become infected with Shiga toxin-producing Escherichia coli (STEC) early in life, which frequently results in long-term shedding of the zoonotic pathogen. Little is known about the animals' immunological status at the time of infection. We assessed the quantity and dynamics of maternal and acquired antibodies to Shiga toxins (Stx1 and Stx2), the principal STEC virulence factors, in a cohort of 27 calves. Fecal and serum samples were taken repeatedly from birth until the 24th week of age. Sera, milk, and colostrums of dams were also assessed. STEC shedding was confirmed by detection of stx in fecal cultures. Stx1-and Stx2-specific antibodies were quantified by Vero cell neutralization assay and further analyzed by immunoblotting. By the eighth week of age, 13 and 15 calves had at least one stx 1 -type and at least one stx 2 -type positive culture, respectively. Eleven calves had first positive cultures only past that age. Sera and colostrums of all dams and postcolostral sera of all newborn calves contained Stx1-specific antibodies. Calf serum titers decreased rapidly within the first 6 weeks of age. Only five calves showed Stx1-specific seroconversion. Maternal and acquired Stx1-specific antibodies were mainly directed against the StxA1 subunit. Sparse Stx2-specific titers were detectable in sera and colostrums of three dams and in postcolostral sera of their calves. None of the calves developed Stx2-specific seroconversion. The results indicate that under natural conditions of exposure, first STEC infections frequently coincide with an absence of maternal and acquired Stx-specific antibodies in the animals' sera.

The Accessory Genome of Shiga Toxin-Producing Escherichia coli Defines a Persistent Colonization Type in Cattle

“…The observation that three of four STEC per genoserotypes possess predominantly stx 1 (O26:H11, O156:H25, O182:H25), while STEC spo genoserotypes are significantly more often positive for stx 2 is consistent with the observation that calves are first colonized by an STEC-1 population, which is later expanded by the occurrence of STEC-2 isolates (16,35,61), implying that stx 1 -positive E. coli are particularly adopted to be part of the normal microbiota in the bovine host. Even though only four cattle herds were sampled, albeit intensively, we detected 4 (O26, O103, O145, O157) of the 5 (additionally O111) EHEC O antigens, which define strains that account for most of the human HUS cases in Germany (31,62,63).…”

“…Clones suspected to have been shed by a single animal or circulating within a herd for at least 4 months were defined as persistent colonization type (STEC per ), whereas isolates detected either Յ2 months (two successive sampling time points) and/or occasionally with at least a 4-month gap in detection were considered sporadically occurring (STEC spo ), resulting in 77 STEC per and 85 STEC spo isolates. Additionally, 16 isolates obtained from calves during a 6-month monitoring study (35) were used as unrelated controls, resulting in a total of 178 STEC isolates in the study.…”

“…Isolates belonging to O-antigen groups O26, O103, O156, O157, and O165 and rough forms were genotyped by contourclamped homogeneous electric field-pulsed-field gel electrophoresis (CHEF-PAGE) (18)(19)(20)(21). Sixteen STEC isolates obtained from sampling a cohort of calves in a different study and randomly selected for further genetic characterization were included in the current study as controls with an undefined colonization pattern (35).…”

Immune Response in Calves Vaccinated with Type Three Secretion System Antigens and Shiga Toxin 2B Subunit of Escherichia coli O157:H7

“…Calves bearing maternal and acquired antibodies against Stx1 and in lesser extent, Stx2 [64] have been reported, sometimes with high frequency of reacting animals [65]. These antibodies have also been detected in natural bovine colostra [66] and in cows immunized with Stx2 [22, 23].…”

Use of Antibody Responses against Locus of Enterocyte Effacement (LEE)-Encoded Antigens To Monitor Enterohemorrhagic Escherichia coli Infections on Cattle Farms

“…Both natural and experimental EHEC infections have shown that cattle develop serum antibodies against intimin, EspA, EspB, and Tir and the Shiga toxins Stx1 and Stx2 (5-7), although the latter are poorly immunogenic in cattle (8). Intimin, EspA, and EspB are more immunogenic in ruminants since oral infection of sheep with a Shiga toxin-negative O157:H7 E. coli strain induced antibody responses against intimin, EspA, and EspB (9).…”