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United States Department of Agriculture

Agricultural Research Service

Research Project: Immunological Intervention of Malignant Catarrhal Fever Virus-Induced Disease in Ruminants

Location: Animal Diseases Research

Title: Development of an in vivo system to measure antibody-blocking of ovine herpesvirus 2 entry

Authors
item Li, Hong
item Cunha, Cristina
item O'Toole, D -
item Nicola, A -
item Knowles, Donald
item Taus, Naomi

Submitted to: Journal of Virological Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 17, 2012
Publication Date: March 1, 2013
Citation: Li, H., Cunha, C.W., O'Toole, D., Nicola, A.V., Knowles Jr, D.P., Taus, N.S. 2013. Development of an in vivo system to measure antibody-blocking of ovine herpesvirus 2 entry. Journal of Virological Methods. 188(1-2):104-107.

Interpretive Summary: Sheep-associated malignant catarrhal fever, a frequently fatal disease caused by a herpesvirus called ovine herpesvirus 2, has emerged as a significant threat to American bison. With no treatment available, development of a vaccine to protect bison from the disease becomes a higher priority for the industry and the producers. Since the causative virus has never been cultured, an alternative to a culture-based virus blocking assay is needed to assess neutralizing antibody activity in vaccine development. Herein we evaluated two animal systems using sheep and rabbits to determine whether they could be used to assess the ability of antibodies to block the virus at the entry site by mixing virus and antiviral serum before challenge by intranasal nebulization. Results showed the system works well. The positive serum reduced viral infectivity by approximately 1,000 fold in sheep based on delayed detection of viral DNA and seroconversion as compared to the negative control group, which received virus treated with negative sheep serum. All rabbits that received the virus mixed with the positive sheep serum were protected from the infection, while all rabbits in the control groups developed disease. The data indicate that this type of animal system, sheep or rabbits, can be used to assess antibody's ability to block virus entry, which is a significant tool for the analysis of protective antibody responses to the virus.

Technical Abstract: Ovine herpesvirus 2 (OvHV-2), the causative agent of sheep-associated malignant catarrhal fever (SA-MCF), has never been propagated in vitro. Thus, an alternative to in vitro virus neutralization is needed to assess neutralizing antibody activity to OvHV-2 in SA-MCF vaccine development. Herein we evaluated an in vivo system in sheep and rabbits to determine whether it could be used to assess the ability of antibodies to block OvHV-2 at the entry site by mixing virus and anti-OvHV-2 serum before challenge by intranasal nebulization. A dose of OvHV-2 (10^6 viral DNA copies) incubated with sheep sera (1:4 final dilution) at 37 C for 1 hr was delivered by intranasal nebulization to sheep and rabbits. All sheep became infected, but the positive serum reduced viral infectivity by approximately 1,000 fold based on delayed detection of viral DNA and seroconversion as compared to the negative control group, which received virus treated with negative sheep serum. All rabbits that received the virus mixed with the positive sheep serum, either with or without complement, were protected from the infection while all rabbits in the control groups developed SA-MCF. The data indicate that this type of in vivo system, sheep or rabbits, can be used to assess antibody's ability to block OvHV-2 entry, which is a significant tool for the analysis of protective antibody responses to the virus.

Last Modified: 12/18/2014