The Value of Serum Antilipoarabinomannan Antibody Detection in the Diagnosis of Latent Tuberculosis in Hemodialysis Patients

Subacute Cardiac Tamponade Due to Tuberculous Pericarditis Diagnosed by Urine Lipoarabinomannan Assay in a Immunocompetent Patient in Oyam District, Uganda: A Case Report

BACKGROUND

Uganda ranks among the countries with the highest burden of TB the world and tuberculous pericarditis (TBP) affects up to 2% of people diagnosed with pulmonary tuberculosis worldwide. In Africa, it represents the most common cause of pericardial disease. Here, we present the case of a 21-year-old male patient who was diagnosed of cardiac tamponade due to tuberculous pericarditis with a positive urine LF-LAM.

CASE REPORT

We report a case of a 21-year-old male living in Oyam district, Uganda, who presented to the emergency department with difficulty in breathing, easy fatigability, general body weakness, and abdominal pain. A chest X-ray showed the presence of right pleural effusion and massive cardiomegaly. Thus, percutaneous pericardiocentesis was performed immediately and pericardial fluid resulted negative both for gram staining and real-time PCR test Xpert MTB/RIF. The following day's urine LF-LAM test resulted positive, and antitubercular therapy started with gradual improvement. During the follow-up visits, the patient remained asymptomatic, reporting good compliance to the antitubercular therapy.

CONCLUSION

Our case highlights the potential usefulness of a LF-LAM-based diagnostic approach, suggesting that, in low-resource settings, this test might be used as part of routine diagnostic workup in patients with pericardial disease or suspected extra-pulmonary tuberculosis.

Decreased percentage of memory B cells is independently associated with increased susceptibility to infection in patients on maintenance hemodialysis

PURPOSE

Infection is a common complication and cause of death in patients on maintenance hemodialysis (MHD). B lymphocytes, which are an important component of the immune system, play a significant role in defending against pathogen invasion. However, in patients on MHD, the connection between infection and B cell subsets remains largely unknown. Our study aims to clarify the potential role of the distribution of B cell subsets in the infection process in patients on MHD.

METHODS

In this cross-sectional study, basic information was collected from 175 patients on MHD from July 2016 to July 2017 at Zhongshan Hospital, Fudan University. The distributions of the B cell subsets in patients with and without infection were analyzed using flow cytometry to determine the role of B lymphocyte subsets in the infection process in patients on MHD.

RESULTS

Among the 175 patients, 45 suffered from infection. The respiratory tract was the most common infection site, accounting for 67.86% of all infections. After adjustment using multivariate logistic regression models, memory B cells [per 1% increase, odds ratio [95% confidence interval (CI)]: 0.949 (0.915, 0.984), P < 0.01], switched memory B cells [per 1% increase, odds ratio (95% CI): 0.939 (0.898, 0.982), P < 0.01], naïve B cells [per 1% increase, odds ratio (95% CI): 1.042 (1.009, 1.075), P < 0.05] and IgG titers [per 1 g/L increase, odds ratio (95% CI): 0.779 (0.630, 0.963), P < 0.05] were independent risk factors for infection in dialysis patients.

CONCLUSION

A decrease in memory B cells is independently associated with an increased risk of infection in patients on dialysis.

Humoral Responses to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR Regulon-Encoded Proteins of Mycobacterium tuberculosis in Individuals with Latent Tuberculosis Infection

Latent tuberculosis infection (LTBI) is evidence of immunological control of tuberculosis. Dormancy survival regulator (DosR) regulon-encoded proteins may have a role in the maintenance of LTBI. T cell responses to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins were found to be most frequent among household contacts of TB cases from Uganda compared to other DosR proteins, but antibody responses were not described. We characterized antibody responses to these proteins in individuals from Uganda. Antibodies to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins were measured in 68 uninfected individuals, 62 with LTBI, and 107 with active pulmonary tuberculosis (APTB) cases. There were no differences in the concentrations of antibodies to Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins between individuals with LTBI and APTB and those who were uninfected. LTBI was associated with higher concentrations of antibodies to Rv1733c in female participants [adjusted geometric mean ratio: 1.812, 95% confidence interval (CI): 1.105 2.973, and p = 0.019] but not in males (p value for interaction = 0.060). Antibodies to the four DosR regulon-encoded proteins investigated may not serve as good biomarkers of LTBI in the general population. More of the M.tb proteome needs to be screened to identify proteins that induce strong antibody responses in LTBI.

Association of lipoarabinomannan with high density lipoprotein in blood: implications for diagnostics

Understanding the pathophysiology of tuberculosis, and the bio-distribution of pathogen-associated molecules in the host is essential for the development of efficient methods of intervention. One of the key virulence factors in the pathology of tuberculosis infection is Lipoarabinomannan (LAM). Previously, we have demonstrated the reliable detection of LAM in urine from tuberculosis patients in a sandwich immunoassay format. We have also applied an ultra-sensitive detection strategy developed for amphiphilic biomarkers, membrane insertion, to the detection of LAM with a limit of detection of 10 fM. Herein, we evaluate the application of membrane insertion to the detection of LAM in patient serum, and demonstrate that the circulating concentrations of 'monomeric' LAM in serum are very low, despite significantly higher concentrations in the urine. Using spiked samples, we demonstrate that this discrepancy is due to the association of LAM with high-density lipoprotein (HDL) nanodiscs in human serum. Indeed, pull-down of HDL nanodiscs from human serum allows for the recovery of HDL-associated LAM. These studies suggest that LAM is likely associated with carrier molecules such as HDL in the blood of patients infected with tuberculosis. This phenomenon may not be limited to LAM in that many pathogen-associated molecular patterns like LAM are amphiphilic in nature and may also be associated with host lipid carriers. Such interactions are likely to affect host-pathogen interactions, pathogen bio-distribution and clearance in the host, and must be thoroughly understood for the effective design of vaccines and diagnostics.

Plasma indoleamine 2,3-dioxygenase and arginase type I may contribute to decreased blood T-cell count in hemodialysis patients

BACKGROUND

Acquired immunity is impaired in hemodialysis (HD) patients, and decreased T-cell number may contribute. Indoleamine 2,3-dioxygenase (IDO) and arginase type I (ARG) catabolize tryptophane and arginine, respectively, and exert proapoptotic and antiproliferative effects on T-cells. Plasma levels of IDO and ARG and their relation to blood T-cell number were evaluated in HD patients.

METHODS

Thirty-two HD patients and 20 healthy controls participated in the study. Plasma IDO and ARG were measured by means of enzyme-linked immunosorbent assay. T-cell number was assessed by means of flow cytometry.

RESULTS

IDO concentration was significantly higher in HD patients than in healthy volunteers (44.30 ± 31.83 ng/mL vs. 21.28 ± 26.21 ng/mL, p = 0.009). There was a trend for higher ARG concentration in HD patients (13.43 ± 11.91 ng/mL) than in healthy volunteers (9.56 ± 4.03 ng/mL), which, however, did not reach statistic significance (p = 0.099). Absolute T-cell count was significantly lower in HD patients than in healthy controls (1176.99 ± 567.71 cells/mm3 vs. 1519.85 ± 594.96 cells/mm3, p = 0.040). Absolute blood T-cell number was inversely related to plasma IDO (r = -0.490, p = 0.004) and to plasma ARG (r = -0.387, p = 0.029) concentrations.

CONCLUSIONS

Plasma IDO and ARG may contribute to decreased blood T-cell count in HD patients.

Lipoarabinomannan in urine during tuberculosis treatment: association with host and pathogen factors and mycobacteriuria

BACKGROUND

Detection of lipoarabinomannan (LAM), a Mycobacterium tuberculosis (Mtb) cell wall antigen, is a potentially attractive diagnostic. However, the LAM-ELISA assay has demonstrated variable sensitivity in diagnosing TB in diverse clinical populations. We therefore explored pathogen and host factors potentially impacting LAM detection.

METHODS

LAM-ELISA assay testing, sputum smear and culture status, HIV status, CD4 cell count, proteinuria and TB outcomes were prospectively determined in adults diagnosed with TB and commencing TB treatment at a South African township TB clinic. Sputum TB isolates were characterised by IS61110-based restriction fragment length polymorphism (RFLP) and urines were tested for mycobacteriuria by Xpert® MTB/RIF assay.

RESULTS

32/199 (16.1%) of patients tested LAM-ELISA positive. Median optical density and proportion testing LAM positive remained unchanged during 2 weeks of treatment and then declined over 24 weeks. LAM was associated with positive sputum smear and culture status, HIV infection and low CD4 cell counts but not proteinuria, RFLP strain or TB treatment outcome. The sensitivity of LAM for TB in HIV-infected patients with CD4 counts of ≥ 200, 100-199, 50-99, and < 50 cells/μl, was 15.2%, 32%, 42.9%, and 69.2% respectively. Mycobacteriuria was found in 15/32 (46.9%) of LAM positive patients and in none of the LAM negative controls.

CONCLUSIONS

Urinary LAM was related to host immune factors, was unrelated to Mtb strain and declined steadily after an initial 2 weeks of TB treatment. The strong association of urine LAM with mycobacteriuria is a new finding, indicating frequent TB involvement of the renal tract in advanced HIV infection.

Validity of interferon-γ-release assays for the diagnosis of latent tuberculosis in haemodialysis patients

Haemodialysis patients are at higher risk of developing active tuberculosis (TB) infection. However, tuberculin skin tests (TST) have limitations and the diagnostic usefulness of interferon-γ-release assays (IGRAs) remains unclear in immunocompromised hosts including haemodialysis patients. Haemodialysis patients were enrolled from a dialysis centre in Korea, an intermediate TB-burden country with a high bacille Calmette-Guérin (BCG) vaccination rate. The QuantiFERON-Gold TB In tube test (QFT) and the T-SPOT TB test (TSPOT) were performed, along with the TST. We stratified patients to low- and high-risk groups, according to the risk factors for latent TB. Association between each of the three diagnostic tests and the risk of latent TB was analysed. One hundred and sixty-seven patients were enrolled. The positive rates for the TST, the QFT and TSPOT were 23.5, 45.9 and 60.4%, respectively. Previous BCG vaccination increased the TST-positive rate in the low-risk group (OR 4.438), whereas it affected neither QFT nor TSPOT. The positive QFT rates were 41.2 and 62.5% in the low- and high-risk groups, respectively. The QFT was associated with the high-risk group (OR 2.578), whereas the TST was not. The positive TSPOT rates were 58.9 and 65.7% in the low- and high-risk groups, respectively. The frequency of indeterminate results was higher for the QFT (12.6%) compared with the TSPOT (4.8%). In conclusion, the IGRAs can be useful for the diagnosis of latent TB infection in haemodialysis patients.

Disturbances of acquired immunity in hemodialysis patients

Acquired immunity disturbances in hemodialysis (HD) patients are many and diverse. They are caused by uremia per se, the HD procedure, chronic renal failure complications, and therapeutic interventions for their treatment. Current data suggest that acquired immunity disturbances in HD patients concern mainly the T-lymphocyte and the antigen-presenting cell (APC). The T-lymphocyte-dependent immune response is deficient, predisposing to infections and inadequate response to vaccinations. In addition, APCs are preactivated, which seems to be responsible for the malnutrition-inflammation-atherosclerosis syndrome, and also affects T-lymphocyte function. At the molecular level it is assumed that the interaction between the APC and the T-lymphocyte is impaired. This disturbance is likely to concern the signal that results from the interaction between the major histocompatibility complex:peptide complex on APC surfaces and T-cell receptors on T-lymphocyte surfaces, or the signal that results from the interaction among the co-receptors of these two cells. The aim of the present review was to collect and classify the available clinical and experimental data in this area. Although many pieces are still missing from the puzzle, a better understanding of the responsible molecular mechanisms, will potentially lead to increased survival and a better quality of life in HD patients.

Evaluation of Serological Diagnosis Tests for Tuberculosis in Hemodialysis Patients

Patients receiving hemodialysis are generally considered to be at increased risk of developing tuberculosis. In the current study, in order to evaluate the usefulness of serological tests in dialysis patients, serum antibodies for tuberculous glycolipids antigen (TBGL) and for lipoarabinomannan (LAM) were measured in hemodialysis patients. The present study included 243 hemodialysis patients. Serum antibodies for TBGL and LAM were measured. Tuberculin skin tests were carried out and chest X-rays evaluated at the same time. There were no patients with active tuberculosis at the time of blood sampling. Thirty-six patients (14.8%) and 25 patients (10.3%) were positive for anti-TBGL antibody and anti-LAM antibody, respectively. One hundred and fifty-five patients (63.8%) were positive for tuberculin skin testing and 123 patients (50.6%) had old pulmonary tuberculosis on their chest X-ray. There was no significant correlation between the results of anti-TBGL antibody and anti-LAM antibody. There were no relationships among the results of tuberculin skin test and the two serological tests. However, positivity of anti-TBGL antibody and anti-LAM antibody was significantly higher in patients with findings of old tuberculosis on the chest X-ray than those without findings. The current results show that these serological tests are positive more frequently in hemodialysis patients without any proof of active tuberculosis than in healthy subjects (2%) and careful interpretation is necessary for relevant results.