Breda virus (Toroviridae) infection and systemic antibody response in sentinel calves

M. Koopmans From the Department of Large Animal Medicine and Nutrition (Koopmans, Cremers), the Department of Infectious Diseases and Immunology, Virology Division, Veterinary Faculty, State University, Yalelaan 1, 3508TD, Utrecht, The Netherlands (Horzinek), and the Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467 (Woode).

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H. Cremers From the Department of Large Animal Medicine and Nutrition (Koopmans, Cremers), the Department of Infectious Diseases and Immunology, Virology Division, Veterinary Faculty, State University, Yalelaan 1, 3508TD, Utrecht, The Netherlands (Horzinek), and the Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467 (Woode).

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Dr G. Woode From the Department of Large Animal Medicine and Nutrition (Koopmans, Cremers), the Department of Infectious Diseases and Immunology, Virology Division, Veterinary Faculty, State University, Yalelaan 1, 3508TD, Utrecht, The Netherlands (Horzinek), and the Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467 (Woode).

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Dr M. C. Horzinek From the Department of Large Animal Medicine and Nutrition (Koopmans, Cremers), the Department of Infectious Diseases and Immunology, Virology Division, Veterinary Faculty, State University, Yalelaan 1, 3508TD, Utrecht, The Netherlands (Horzinek), and the Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467 (Woode).

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SUMMARY

Enzyme-linked immunosorbent assays were established to detect Breda virus antigen in feces and homologous antibodies of the IgGl, IgM, and IgA isotypes in serum. With the aid of solid-phase immune-electron microscopy, torovirions in fecal material were observed. The course of natural infection was studied in 10 sentinel calves that had been obtained from different farms, and housed together at 1 week of age. They were separated from other cattle until the age of 10 months.

Up to the age of 4 months, all calves regularly excreted Breda virus in the feces. Irrespective of the existence of IgG1 isotype maternal antibodies, all calves had early IgM responses in serum, but lack of IgA seroconversion. In 7 calves, antibody titer decreased below detection, whereas 3 calves had an isotype switch, resulting in persistent IgG1 titer. After introduction into the dairy herd at 10 months of age, all calves had diarrhea, and shedding of Breda virus was observed in 8 of them. Seroconversion for all antibody isotypes was observed, indicating lack of mucosal memory. In contrast, coronavirus infection in the presence of maternal antibodies led to isotype switch in all calves but one, and a memory response was observed after introduction into the dairy herd.

SUMMARY

Enzyme-linked immunosorbent assays were established to detect Breda virus antigen in feces and homologous antibodies of the IgGl, IgM, and IgA isotypes in serum. With the aid of solid-phase immune-electron microscopy, torovirions in fecal material were observed. The course of natural infection was studied in 10 sentinel calves that had been obtained from different farms, and housed together at 1 week of age. They were separated from other cattle until the age of 10 months.

Up to the age of 4 months, all calves regularly excreted Breda virus in the feces. Irrespective of the existence of IgG1 isotype maternal antibodies, all calves had early IgM responses in serum, but lack of IgA seroconversion. In 7 calves, antibody titer decreased below detection, whereas 3 calves had an isotype switch, resulting in persistent IgG1 titer. After introduction into the dairy herd at 10 months of age, all calves had diarrhea, and shedding of Breda virus was observed in 8 of them. Seroconversion for all antibody isotypes was observed, indicating lack of mucosal memory. In contrast, coronavirus infection in the presence of maternal antibodies led to isotype switch in all calves but one, and a memory response was observed after introduction into the dairy herd.

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