Relevance of autoantibody detection to the rapid diagnosis of brucellosis

Prevalence and relevant factors of positive RF in brucellosis patients with arthralgia

Background

Brucellosis is a critical zoonotic disease in the world, it is the non-specific arthralgia that make brucellosis patients easily misdiagnosed as rheumatoid arthritis (RA) in endemic regions. Elevated rheumatoid factor (RF) is an essential indicator of RA, and the RF in brucellosis patients is significantly higher than healthy people. Therefore, this study further explored the distribution of RF and the relevant factors of the RF positivity in brucellosis patients with arthralgia, in order to strengthen the recognition of physicians for brucellosis patients with RF positivity, especially in brucellosis-endemic areas, so as to avoid misdiagnosis and untimely treatment that may lead to malignant outcomes.

Methodology and principal findings

The medical records of all 572 brucellosis inpatients were collected in the Sixth People’s Hospital of Shenyang, China from 2015 to 2016. After excluding 106 patients without arthralgia, 5 patients who unwilling to perform RF testing and 16 patients with diseases that may affect RF, 445 brucellosis inpatients with arthralgia were involved in this retrospective cross-sectional study. 143 (32.1%) patients with RF >10 IU/ml were classified into the RF positive group, with an average level of 16.5[12.2, 34.7] IU/ml, of which 45 (10.1%) patients were high-positive with RF >30 IU/ml. Multivariate logistic regression model was used to further analyze the relevant factors of the RF positivity and found that age, wrist joint pain and elevated C-reactive protein (CRP) were positively associated with RF positivity, with OR of 1.02 (P = 0.024), 8.94 (P = 0.008) and 1.79 (P = 0.019), respectively.

Conclusion

The prevalence of positive RF in brucellosis patients with arthralgia was critical, nearly one-third of patients had RF positive. Elderly men brucellosis patients with arthralgia, wrist joint pain and elevated CRP were at high risk of positive RF. It is reminded that physicians should focus on differential diagnosis during clinical diagnosis and treatment, especially in brucellosis-endemic regions.

Brucellosis is a highly contagious zoonosis caused by Brucella spp., which compromises to organs and systems, causing non-specific symptoms such as fever, headache, sweating, fatigue, myalgia and arthralgia. Similarly, patients with rheumatoid arthritis (RA) may also have the above non-specific symptoms. It is precisely because of the non-specificity and similarity of symptoms that brucellosis patients were easily misdiagnosed and failed to receive timely treatment, resulting in neurosis, chronic fatigue syndrome, endocarditis and other adverse outcomes. However, rheumatoid factor (RF) is an essential indicator of RA, and the RF in brucellosis patients is significantly higher than healthy people. In order to strengthen the recognition of physicians for brucellosis patients with RF positivity, we conducted this research and found that the prevalence of positive RF in brucellosis patients with arthralgia was common and critical. Elderly men brucellosis patients with arthralgia, wrist joint pain and elevated CRP were at high risk of positive RF. It is reminded that physicians should pay attention to the possibility of brucellosis during clinical diagnosis and treatment, especially in brucellosis-endemic regions, which had certain clinical significance.

Utility of the Rose Bengal Test as a Point-of-Care Test for Human Brucellosis in Endemic African Settings: A Systematic Review

In endemic African areas, such as Tanzania, Brucella spp. cause human febrile illnesses, which often go unrecognized and misdiagnosed, resulting in delayed diagnosis, underdiagnosis, and underreporting. Although rapid and affordable point-of-care tests, such as the Rose Bengal test (RBT), are available, acceptance and adoption of these tests at the national level are hindered by a lack of local diagnostic performance data. To address this need, evidence on the diagnostic performance of RBT as a human brucellosis point-of-care test was reviewed. The review was initially focused on studies conducted in Tanzania but was later extended to worldwide because few relevant studies from Tanzania were identified. Databases including Web of Science, Embase, MEDLINE, and World Health Organization Global Index Medicus were searched for studies assessing the diagnostic performance of RBT (sensitivity and specificity) for detection of human brucellosis, in comparison to the reference standard culture. Sixteen eligible studies were identified and reviewed following screening. The diagnostic sensitivity (DSe) and specificity (DSp) of RBT compared to culture as the gold standard were 87.5% and 100%, respectively, in studies that used suitable "true positive" and "true negative" patient comparison groups and were considered to be of high scientific quality. Diagnostic DSe and DSp of RBT compared to culture in studies that also used suitable "true positive" and "true negative" patient comparison groups but were considered to be of moderate scientific quality varied from 92.5% to 100% and 94.3 to 99.9%, respectively. The good diagnostic performance of RBT combined with its simplicity, quickness, and affordability makes RBT an ideal (or close to) stand-alone point-of-care test for early clinical diagnosis and management of human brucellosis and nonmalarial fevers in small and understaffed health facilities and laboratories in endemic areas in Africa and elsewhere.

Prevalence of positive autoimmune biomarkers in the brucellosis patients

Brucellosis is a chronic infectious disease with articular involvement. Discrimination between brucellosis and rheumatologic disorders is difficult in regions endemic for brucellosis. There are few studies about the rate of positive autoantibodies as rheumatologic biomarkers in brucellosis, and the prevalence is variable. In this study, the rheumatologic tests were studied in brucellosis patients. This cross sectional study was performed in two teaching hospitals in Tehran, Iran. Forty-nine patients with brucella infection and 42 healthy participants were enrolled in this study. Brucellosis was diagnosed on the basis of the clinical symptoms and positive serology for brucellosis. Rheumatic factor (RF) and antinuclear antibodies (ANA) were evaluated in all patients. Cyclic citrullinated peptides antibody (ACPA) and anti-double strand DNA (anti-dsDNA) were checked in all patients and control groups. Out of 49 patients, 15 (30.6 %) were RF positive and 4 (8.2 %) were ANA positive. Anti-dsDNA was concurrently positive with ANA in 1 patient (2 %) but ACPA titer was positive in 8 patients (16.3 %). None of the patients with positive autoantibody biomarkers fulfilled the criteria for rheumatologic disorders. The rate of positive RF in healthy people was significantly lower than patient group (2.4 vs. 30.6 %), but the positiveness rate of other biomarkers did not have significant difference in two groups. Sixty percent of the patients with positive RF and 75 % with positive ACPA had skeletal involvement (P < 0.05). Autoantibody biomarkers can be positive in brucellosis. Rheumatologists should be aware of brucellosis in patients with musculoskeletal involvement and positive autoantibody biomarkers in endemic regions.

Thermostable cross-protective subunit vaccine against Brucella species

A subunit vaccine candidate was produced from Brucella suis 145 (biovar 4; expressing both the A antigen of Brucella abortus and the M antigen of Brucella melitensis). The preparation consisted mostly of polysaccharide (PS; >90% [wt/wt]; both cell-associated PS and exo-PS were combined) and a small amount of protein (1 to 3%) with no apparent nucleic acids. Vaccinated mice were protected (these had a statistically significant reduction in bacterial colonization compared to that of unvaccinated controls) when challenged with representative strains of three Brucella species most pathogenic for humans, i.e., B. abortus, B. melitensis, and B. suis. As little as 1 ng of the vaccine, without added adjuvant, protected mice against B. suis 145 infection (5 × 10(5) CFU), and a single injection of 1 μg of this subunit vaccine protected mice from B. suis 145 challenge for at least 14 months. A single immunization induced a serum IgG response to Brucella antigens that remained elevated for up to 9 weeks. The use of heat (i.e., boiling-water bath, autoclaving) in the vaccine preparation showed that it was thermostable. This method also ensured safety and security. The vaccine produced was immunogenic and highly protective against multiple strains of Brucella and represents a promising candidate for further evaluation.

Bayesian estimation of the seroprevalence of brucellosis in humans and livestock in Kyrgyzstan

Kyrgyzstan reported 77.5 new cases of human brucellosis per 100,000 inhabitants in 2007, which is one of the highest incidences in the world. However, because this number is based on official records, it is very likely that the incidence is underreported. The diagnostic tests most commonly used in Kyrgyzstan are the Rose Bengal test in ruminants and the Huddleson test in humans. The sensitivity and specificity of these tests have never been evaluated under field conditions in Kyrgyzstan, where the strains circulating in livestock and humans are unknown. Therefore, a representative national cross-sectional serological study was undertaken in humans, cattle, sheep and goats to assess the true seroprevalence and to compare different serologicaltests. In the year of study (2006), few animals were vaccinated against brucellosis in Kyrgyzstan. A total of 5,229 livestock sera and 1,777 human sera from three administrative regions were collected during spring 2006 and submitted to a range of serological tests. The true seroprevalence of brucellosis, estimated using Bayesian methodology, was 7% (95% credibility interval 4%-9%) in humans, 3% (1%-5%) in cattle, 12% (7%-23%) in sheep and 15% (7%-30%) in goats. The Rose Bengal test was confirmed as a useful screening test in livestock and humans, although its sensitivity was lower than that of other tests. The estimates of specificity of all tests were significantly higher than those for sensitivity. The high seroprevalence of brucellosis in humans, cattle and small ruminants in Kyrgyzstan was confirmed. Bayesian statistical approaches were demonstrated to be useful for simultaneously deriving test characteristics and true prevalence estimates in the absence of a gold standard.

Soluble expression and purification of Brucella cell surface protein (BCSP31) of Brucella melitensis and preparation of anti-BCSP31 monoclonal antibodies

Brucella cell surface protein (BCSP31) is potentially useful for diagnosing brucellosis. We aimed to establish a monoclonal antibody (MAb) against Brucella melitensis BCSP31 and to investigate its distribution in diagnosis. Soluble recombinant BCSP31 was successfully expressed and purified. Two MAbs (1F1 and 1E5) against B. melitensis BCSP31, effective in detecting both recombinant and cellular proteins, were obtained and characterized. The MAbs did not react with Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Mycobacterium tuberculosis, or Bacillus aeruginosus, but strongly reacted with BCSP31 and B. melitensis by ELISA and Western blot analysis. We also tested different Brucella species and brucellosis using the prepared anti-BCSP31 MAbs. BCSP31 and anti-BCSP31 MAbs may play important roles in future research in diagnosing brucellosis.