Evaluation of P22 Antigenic Complex for the Immuno-Diagnosis of Tuberculosis in BCG Vaccinated and Unvaccinated Goats

Claudia Arrieta-Villegas; José Antonio Infantes-Lorenzo; Javier Bezos; Miriam Grasa; Enric Vidal; Irene Mercader; Mahavir Singh; Mariano Domingo; Lucía de Juan; Bernat Pérez de Val

doi:10.3389/fvets.2020.00374

Evaluation of P22 Antigenic Complex for the Immuno-Diagnosis of Tuberculosis in BCG Vaccinated and Unvaccinated Goats

Front Vet Sci. 2020 Jul 3:7:374. doi: 10.3389/fvets.2020.00374. eCollection 2020.

Authors

Affiliations

¹ IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus Universitat Autònoma de Barcelona, Barcelona, Spain.
² Servicio de Inmunología Microbiana, Centro Nacional de Microbiología, Instituto de Investigación Carlos III, Madrid, Spain.
³ VISAVET Health Surveillance Center, Universidad Complutense de Madrid, Madrid, Spain.
⁴ Departamento de Sanidad Animal, Universidad Complutense de Madrid, Madrid, Spain.
⁵ Agrupació de Defensa Sanitària de Cabrum i Oví Lleter de Catalunya, Barbens, Spain.
⁶ Departament d'Agricultura, Ramaderia, Pesca i Alimentació de la Generalitat de Catalunya, Barcelona, Spain.
⁷ Lionex Diagnostics and Therapeutics GmbH, Braunschweig, Germany.
⁸ Departament de Sanitat i Anatomia Animals, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain.

Abstract

Current eradication strategies of tuberculosis (TB) in goats mainly rely on the single intradermal tuberculin test (SIT) and single intradermal cervical comparative tuberculin tests (SICCTs). TB vaccination has been proposed as a cost-effective option in high-prevalence herds or countries where economic compensation for the slaughter of positive animals is not affordable. However, TB vaccination compromises the efficiency of tuberculin-based diagnostic tests. In this study, the performance of a new diagnostic platform, based on the P22 antigenic complex, was assessed for skin test (ST), interferon-gamma release assay (IGRA), and serology under different TB scenarios. The sensitivity (Se) of diagnostic tests was assessed in TB-infected goats from the same farm (herd A, N = 77). The specificity (Sp) was assessed in two TB-negative farms (both vaccinated against paratuberculosis): one TB unvaccinated (herd B, N = 77) and another vaccinated with bacille Calmette-Guérin (BCG) (herd C, N = 68). The single (s) P22-IGRA showed the highest Se among IGRA tests (91%), and the comparative (c) P22-ST showed the highest Sp (100% in herd B and 98% in herd C). Combined interpretation of techniques enabled the best diagnostic performances. Combining the SICCT + sP22-IGRA improved Se (97%) compared to SICCT + tuberculin-based IGRA (95%), with a reduction of Sp (95 and 100%, respectively). Besides, combination of P22-ELISA with cP22-ST or SICCT elicited a similar performance in the non-vaccination context (Se: 94 and 95%; Sp: 95 and 95%, respectively), but Sp was significantly higher for the combination with cP22-ST compared to SICCT in the TB vaccination context (95 and 79%, respectively). The combination of serological tests based on P22 and MPB83 showed higher complementarity and improved 13 percentage points the Se of P22-ELISA alone. These findings suggest that either cell-mediated or antibody-based diagnostic techniques, using the P22 antigen complex, can contribute to improve the immunodiagnostics of TB in goats under different TB control strategies.

Keywords: P22; bacille Calmette-Guérin (BCG); diagnosis; goats; interferon-gamma release assay (IGRA); serology; skin test; tuberculosis.