Avaliação de um teste imunocromatográfico rápido para o diagnóstico da brucelose bovina baseado em uma proteína recombinante BP26

Abstract

Brucellosis is an infectious disease that is an important zoonosis worldwide. It is caused by a gram-negative facultative intracellular bacterium that has the ability to adapt to their preferred host, modulating the immune response to induce a chronic infection. It affects several species of animals and can be transmitted through contaminated food, mainly unpasteurized milk and dairy products. In cattle, the disease causes losses in livestock production due to reproductive changes. The most common species that infects cattle is Brucella abortus. The disease is enzootic in Brazil, therefore, control measures in domestic animals are the main form of control in humans. In 2001, the Ministry of Agriculture and Livestock launched the national program for the control and eradication of brucellosis (PNCEBT) which, together with tuberculosis, constitutes an important health program for the control and eradication of both diseases. Recommended measures included mass vaccination of heifers and serological tests for the detection of infected animals. The serological tests used in Brazil are based on the S-LPS antigen of Brucella more precisely the O chain. However, false-negative or false-positive reactions may occur. In order to overcome this limitation, novel antigens have been studied. The BP26 protein has been extensively studied and considered a promising antigen, as it induced a detectable response in infected animals. This study evaluated a recombinant BP26 protein used as antigen in a rapid test (rBP26-TRIFL) that could be used in the field, with quick visual reading and without the need for laboratory equipment and personnel with specific training. Analytical performance characteristics and accuracy were evaluated in positive and negative bovine serum samples characterized by the AAT and SAL/2-ME tests, with analyticals sensitivity and specificity of 73,91% (CI 95%: 51,59% - 89,77%) e 97,14% (CI 95%: 90,06% - 99,65%), respectively. Then, the diagnostic performance of the test was evaluated using 467 bovine serum samples characterized by the AAT, SAL/2-ME from several Brazilian states and with different epidemiological situations. The diagnostic sensitivity (DSe) and specificity (DSp) for rBP26-TRIFL were 5.73% (CI 95%: 2.65% - 10.60%) and 99.35% (CI 95%: 97.69% - 99.92%), respectively. The estimated accuracy was 67.88%. The calculation of the kappa index presented a value of 0, indicating low agreement with the AAT, SAL/2-ME tests. In conclusion, rBP26-TRIFL showed a low DSe despite a high DSp. In conclusion, rBP26-TRIFL In conclusion, the rBP26-TRIFL test showed good analytical performance, but limited diagnostic performance, restricting for the time being its recommendation for use in different epidemiological scenarios for the care of the PNCEBT. This study also allowed demonstrating that a test with good analytical performance may not necessarily present good diagnostic performance, indicating the need for a new standardization according to field conditions and that both evaluations are necessary for making a more accurate decision regarding its use by a health program.