Evaluation of recombinant porin (rOmp2a) protein as a potential antigen candidate for serodiagnosis of Human Brucellosis

Brucellosis detection and the role of Brucella spp. cell wall proteins

Brucellosis remains an endemic zoonotic disease in many developing countries, causing great harm to public health and devastating losses to livestock. One of the main reasons for the low effectiveness of anti-brucellosis measures is the lack of reliable methods for diagnosing infected animals throughout their lifespan. Classical serological tests, such as the tube agglutination test, rose Bengal plate test, and complement fixation test, as well as commercial enzyme-linked immunosorbent assay kits, are based on the detection of antibodies to the cell wall polysaccharide antigens of Brucella spp. smooth strains. As a result, they do not exclude cross-reactions with related bacteria and fail to differentiate between infected and vaccinated animals. Over the past decades, many attempts have been made to identify immunoreactive and pathogen-specific protein antigens. To date, several studies have investigated Brucella spp. recombinant proteins, including cell wall proteins, as the best antigens for diagnosing brucellosis in animals and humans. However, the available results on the specificity and sensitivity of serological tests based on cell wall proteins are ambiguous and sometimes contradictory. This review aims to provide an overview of the current state of knowledge of the diagnostic value of outer membrane and/or periplasmic proteins of Brucella spp. The goal is to identify future developments that may lead to reliable antigens for serological tests.

NLRP6 Induces Lung Injury and Inflammation Early in Brucella and Influenza Coinfection

(1) Background: With the resurgence of brucellosis epidemics in China in recent years, the chances of a brucella coinfection with other common respiratory pathogens, such as the influenza virus, have increased dramatically. However, little is known about the pathogenicity or the mechanisms of brucella and influenza coinfections. (2) Methods: To clarify the interventions in the early stages of lung damage due to brucella and influenza coinfections, we evaluated the effect of the coinfection on disease progression and mortality using a coinfection model in WT mice and NLRP6^-/- mice, and we verified the function of NLRP6 in infection and proinflammation. (3) Results: The coinfection induced significant respiratory symptoms, weight loss, and a high mortality rate in WT mice. Influenza in the coinfection group significantly increased brucella proliferation in a synergistic manner. Meanwhile, a histological examination showed severe lung tissue destruction and excessive inflammatory responses in coinfected WT animals, and the expression of NLRP6 and IL-18 was dramatically increased in the lung tissues. Furthermore, NLRP6 deletion attenuated lung injuries and inflammation, a reduced bacterial load, and decreased IL-18 protein expression. (4) Conclusions: Our findings indicated that NLRP6 plays a critical role and might be a promising potential therapeutic target for brucella-influenza coinfections.

Hybrid recombinant Omp 22, 25, and 31 immunodominant epitopes can be used for serodiagnosis of brucellosis

Brucellosis is a well-known infectious disease in most parts of the world, especially in developing countries, common between humans and animals. Brucellosis is diagnosed by serological tests based on lipopolysaccharides (LPSs), which are bacterial cell wall antigens, and due to the similarities between LPSs antigens of some gram-negative bacterias, false-positive responses are inevitable. Alternatively, Outer membrane proteins (Omps), as antigenic conserved membrane proteins, can be used to diagnose brucellosis instead of LPS antigens. In this study, by using bioinformatics tools, linear B-cell epitopes were selected from Omp22, Omp25, and Omp31 antigens and fused with the rigid KP linker (K = Lysine, P=Proline). Designed gene cassette was cloned into pET-28a (+) vector and expressed recombinant protein was purified using Ni-NTA chromatography column and was confirmed with Poly-Histidine-HRP antibody. Finally, recombinant protein's seroreactivity with serum samples from 37 patients and 27 healthy individuals was evaluated by western blotting and enzyme-linked immunosorbent assay (ELISA) methods. Western blotting results showed high reactivity of the recombinant protein with serum samples of Brucella infected patients. ELISA results were analyzed using the receiver operating curve (ROC). Optical density cut-off point, accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Youden index J for recombinant protein were > 0.809, 84.37%,83.78%,88.89%,88.57%, 79.31% and 0.72 respectively. Western blotting and ELISA results showed that our recombinant protein has good sensitivity and specificity for the diagnosis of brucellosis.

Cloning, expression and purification of virB10 protein of Brucella melitensis and evaluation of its role as a serological marker for Brucella infection in experimental and natural host

Brucellosis is a zoonotic disease caused by various species of the genus Brucella. The control of this disease mainly depends on its accurate and early diagnosis. Culture methods employed for diagnosis are time consuming and require well equipped biosafety level 3 laboratories and hence serological tests are favored alternative for brucellosis diagnosis. At present serological diagnosis is based on LPS (lipopolysaccharide) which is less specific as it shows cross reactivity with other gram-negative bacteria. There is a need to develop serological diagnostic assay based on purified recombinant antigen of Brucella. T4SS (Type IV Secretion System) is an important virulent factor of Brucella and required for infection suggesting their expression in vivo and can be targeted as serological marker for infection. To test this concept, the present study is designed to clone, express and purify virB10 gene of Brucella T4SS under denaturing conditions and to evaluate its use as serological marker of Brucella infection. The immunoreactivity of this recombinant antigen was checked with antisera collected after experimental infection in Balb/C mice with B. melitensis 16M, BR31 (human clinical isolate) and Y. enterocolitica O:9. The recombinant protein was also tested against a panel of 46 bovine sera samples collected from Leh, India. Antibody response against VirB10 was detected in experimental and natural host suggesting that it can be explored as potential target for serodiagnosis of Brucella infection.