DEVELOPMENT OF CONJUGATED SECONDARY ANTIBODIES FOR WILDLIFE DISEASE SURVEILLANCE

Abstract

Intro: Wildlife can be reservoir hosts for a variety of pathogens causing disease along the livestock- wildlife- and human interface, such as brucellosis, tuberculosis, and anthrax. Proactive surveillance relying on detection of specific antibodies could give more reliable and timely insight into the prevalence of a disease in an environment, especially if it occurs below detection thresholds for passive surveillance. Host-specific ELISAs (Enzyme-Linked Immunosorbent Assays) are serological tests most often used in wildlife disease studies; for example, the Bacillus anthracis protective antigen (PA)-ELISA that has been used for surveillance of anthrax exposure in kudu and impala in the Kruger National Park, South Africa. However, serological biosurveillance is often hampered by a lack of species-specific conjugates that can be used in assays. Methods: In this study, we developed anti-kudu and -impala conjugates in chickens and evaluated the performance of these conjugates in comparison to commercial protein-A, -G and -AG conjugates. This was accomplished by measuring avidity, which is the total binding strength of an antibody at antigen binding sites between the conjugates and wildlife (kudu, impala) sera, in an avidity ELISA. The developed conjugates were also evaluated for cross-reaction with other wild herbivores to evaluate the use of these conjugates for diagnostic ELISAs in other wildlife species. Findings: The developed conjugates had a high relative avidity index of > 70%, compared to the commercial conjugates (protein A, G and AG), which had significantly low relative avidity (<20%). Eighteen other wildlife species demonstrated cross reactivity with a relative avidity of more than 50% with the impala and kudu conjugates. Conclusion: Developing conjugates that perform better in wildlife will provide tools for better surveillance of zoonotic agents along the livestock, wildlife, and human interface. These results also demonstrate the value of these developed conjugates for significantly improving the quality of the immunoassays currently in use in wildlife.