Interferon-γ and Immunoglobulins in Latent Tuberculosis Infection

Nutritional status positively impacts humoral immunity against its Mycobacterium tuberculosis, disease progression, and vaccine development

Nutritional status contributes to the regulation of immune responses against pathogens, and malnutrition has been considered as a risk factor for tuberculosis (TB). Mycobacterium tuberculosis (Mtb), the causative agent of TB, can modulate host lipid metabolism and induce lipid accumulation in macrophages, where the bacilli adopt a dormant phenotype. In addition, serum lipid components play dual roles in the regulation of and protection from Mtb infection. We analyzed the relationship between nutritional status and the humoral immune response in TB patients. We found that serum HDL levels are positively correlated with the serum IgA specific for Mtb antigens. Analysis of the relationship between serum nutritional parameters and clinical parameters in TB patients showed that serum albumin and CRP levels were negatively correlated before treatment. We also observed reduced serum LDL levels in TB patients following treatment. These findings may provide insight into the role of serum lipids in host immune responses against Mtb infection. Furthermore, improving the nutritional status may enhance vaccination efficacy.

Risk of Occupational Latent Tuberculosis Infection among Health Personnel Measured by Interferon-Gamma Release Assays in Low Incidence Countries-A Systematic Review and Meta-Analysis

Healthcare workers (HCWs) have increased risk for latent tuberculosis infection (LTBI) and tuberculosis (TB) disease due to their occupational exposure. For some years now, interferon-γ release assays (IGRAs) have replaced the tuberculin skin test for the diagnosis of LTBI in many countries. This review examined the occupational risk of LTBI in HCWs with IGRA testing in low incidence countries. A systematic review and meta-analysis of studies from 2005 onwards provide data regarding the prevalence of LTBI in HCWs. In addition, the pooled effect estimates were calculated for individual regions and occupational groups. 57 studies with 31,431 HCWs from four regions and a total of 25 countries were analysed. The prevalence of LTBI varied from 0.9 to 85.5%. The pooled estimation found the lowest prevalence of LTBI for North American and West Pacific countries (<5%), and the highest prevalence for Eastern Mediterranean countries (19.4%). An increased risk for LTBI was found only for administrative employees. Studies on the occupational risk of LTBI continue to show increased prevalence of HCWs, even in low-incidence countries. Good quality studies will continue to be needed to describe occupational exposure.

Latent tuberculosis infection in healthcare workers in low- and middle-income countries: an updated systematic review

Healthcare workers (HCWs) are at increased risk of latent tuberculosis (TB) infection (LTBI) and TB disease.We conducted an updated systematic review of the prevalence and incidence of LTBI in HCWs in low- and middle-income countries (LMICs), associated factors, and infection control practices. We searched MEDLINE, Embase and Web of Science (January 1, 2005-June 20, 2017) for studies published in any language. We obtained pooled estimates using random effects methods and investigated heterogeneity using meta-regression.85 studies (32 630 subjects) were included from 26 LMICs. Prevalence of a positive tuberculin skin test (TST) was 14-98% (mean 49%); prevalence of a positive interferon-γ release assay (IGRA) was 9-86% (mean 39%). Countries with TB incidence ≥300 per 100 000 had the highest prevalence (TST: pooled estimate 55%, 95% CI 41-69%; IGRA: pooled estimate 56%, 95% CI 39-73%). Annual incidence estimated from the TST was 1-38% (mean 17%); annual incidence estimated from the IGRA was 10-30% (mean 18%). The prevalence and incidence of a positive test was associated with years of work, work location, TB contact and job category. Only 15 studies reported on infection control measures in healthcare facilities, with limited implementation.HCWs in LMICs in high TB incidence settings remain at increased risk of acquiring LTBI. There is an urgent need for robust implementation of infection control measures.

Assessing the Prevalence of Latent Tuberculosis among Health Care Providers in Zagazig City, Egypt Using Tuberculin Skin Test and QuantiFERON-TB Gold In-Tube Test

AIM

Early detection of latent tuberculosis infection (LTBI) will prevent development of active TB among health care providers. The aim of the study was to assess the prevalence of LTBI among health care providers and compare the QuantiFERON-TB Gold In-Tube Test (QFT-GIT) and Tuberculin skin test in efforts to detect LTBI and to investigate possible associated risk factors of infection.

METHODS

A cross sectional study was carried out during the period of 6 months in the Chest Hospital in Zagazig city and the Nephrology Unit at Zagazig University Hospitals in 132 randomly selected health care providers who were examined for LTBI by QFT-GIT and Tuberculin skin test and for the associated risk factors as well.

RESULTS

The prevalence of LTBI identified by QFT-GIT and by Tuberculin skin test was 28.8% and 59.1%, respectively. Poor agreement was observed between the two tests (kappa=0.10). Working more than 10 years, being nurse, diabetic and smoker were risk factors significantly associated with LTBI (p<0.05).

CONCLUSIONS

QFT-GIT is considered a useful tool in detecting LTBI cases, especially in a country where BCG vaccination is a national policy (as in Egypt). Duration of work, profession, diabetes and smoking are the risk factors for LTBI. Active surveillance and infection control measures are recommended to reduce the risk of LTBI.

Interferon-γ Release Assay vs. Tuberculin Skin Test for Tuberculosis Screening in Exposed Healthcare Workers: A Longitudinal Multicenter Comparative Study

OBJECTIVE

Healthcare workers (HCWs), especially those caring for patients with tuberculosis (TB), are at high risk of acquiring that disease. The poor specificity of tuberculin skin testing (TST) prompted us to evaluate the effectiveness of the interferon-γ release assay (IGRA) in comparison with TST in a large prospective, multicenter, 1-year study of HCWs with occupational exposure to TB.

METHODS

HCWs from high-risk units at 14 university hospitals were invited to participate and underwent both TST and IGRA (first Quantiferon TB Gold-IT®, QFT-G, then T-SPOT.TB® if QFT-G was indeterminate) at baseline and after 1 year. We collected demographic characteristics, country of birth, history of TB, immunosuppression, past exposure to TB, history of BCG vaccination, results of most recent TST, job category, and duration of current function.

RESULTS

Among 807 HCWs enrolled, current or past TST at baseline was positive (≥15 mm) in 282 (34.9%); the IGRA was positive in 113 (14.0%) and indeterminate in 3 (0.4%). After 1 year, 594 HCWs had both an IGRA and TST (or prior TST≥15 mm) at baseline and an IGRA and TST (if indicated). The conversion rate was 2.5% (9 of 367) with TST and 7.6% (45 of 594) with IGRA, with poor agreement between the 2 tests. Using only QFT-G, conversion (9.9%) and reversion (17.8%) rates were higher for baseline QFT-G positive quantitative values <1 IU/mL.

CONCLUSION

TST and the IGRA yielded discordant results. The value of IGRA in addition to TST remains undetermined; the two should be jointly interpreted in decision-making (clinical trial registration NCT00797836).

Infect Control Hosp Epidemiol 2015;00(0): 1–6

Tuberculin skin test and Quantiferon test agreement and influencing factors in tuberculosis screening of healthcare workers: a systematic review and meta-analysis

Objective

A systematic review and meta-analysis was conducted to evaluate the agreement between Tuberculin Skin Test (TST) and Quantiferon (QFT) in screening for tuberculosis (TB) infection among healthcare workers (HCWs) and to estimate associations between TST and QFT agreement and variables of interest, such as Bacillus Calmette-Guérin (BCG) vaccination and incidence of TB.

Methods

Cross-sectional and longitudinal studies on HCWs, published in English until October 2013, comparing TST and QFT results, were selected. For each study Cohen’s κ value and a 95% confidence interval were calculated. Summary measures and indexes of heterogeneity between studies were calculated.

Results

29 studies were selected comprising a total of 11,434 HCWs. Cohen’s κ for agreement between TST and QFT for 24 of them was 0.28 (95% CI 0.22 to 0.35), with the best value in high TB incidence countries and the lowest rate of BCG vaccination.

Conclusion

Currently, there is no gold standard for TB screening and the most-used diagnostic tools show low agreement. For evidence-based health surveillance in HCWs, occupational physicians need to consider a number of factors influencing screening results, such as TB incidence, vaccination status, age and working seniority.

Frequent detection of anti-tubercular-glycolipid-IgG and -IgA antibodies in healthcare workers with latent tuberculosis infection in the Philippines

Anti-tubercular-glycolipid-IgG (TBGL-IgG) and -IgA (TBGL-IgA) antibodies, and the QuantiFERON-TB Gold test (QFT) were compared in healthcare workers (HCWs, n = 31) and asymptomatic human immunodeficiency virus-carriers (HIV-AC, n = 56) in Manila. In HCWs, 48%, 51%, and 19% were positive in QFT, TBGL-IgG, and -IgA, respectively. The TBGL-IgG positivity was significantly higher (P = 0.02) in QFT-positive than QFT-negative HCWs. Both TBGL-IgG- and -IgA-positive cases were only found in QFT-positive HCWs (27%). The plasma IFN-γ levels positively correlated with TBGL-IgA titers (r = 0.74, P = 0.005), but not TBGL-IgG titers in this group, indicating that mucosal immunity is involved in LTBI in immunocompetent individuals. The QFT positivity in HIV-AC was 31% in those with CD4+ cell counts >350/μL and 12.5% in low CD4 group (<350/μL). 59 % and 29% were positive for TBGL-IgG and -IgA, respectively, in HIV-AC, but no association was found between QFT and TBGL assays. TBGL-IgG-positive rates in QFT-positive and QFT-negative HIV-AC were 61% and 58%, and those of TBGL-IgA were 23% and 30%, respectively. The titers of TBGL-IgA were associated with serum IgA (P = 0.02) in HIV-AC. Elevations of TBGL-IgG and -IgA were related to latent tuberculosis infection in HCWs, but careful interpretation is necessary in HIV-AC.

B lymphocytes that migrate to tuberculous pleural fluid via the SDF-1/CXCR4 axis actively respond to antigens specific for Mycobacterium tuberculosis

B-cell biology has been largely uncharacterized in the field of tuberculosis (TB). In this study, we investigated the immunophenotypical and functional characteristics of B cells obtained from the pleural fluid (PF) and peripheral blood of patients with tuberculous pleuritis (TP). Our results indicated that the total numbers of B cells, CD27(+) memory B cells and plasmablasts were clearly lower in the PF than in peripheral blood. Furthermore, we found significantly higher expression of CXCR4 on B cells in the PF, and a chemotaxis assay showed that B cells in the PF were more responsive to stromal cell-derived factor-1 (SDF-1) than B cells from peripheral blood. In addition, SDF-1 levels in PF were remarkably high compared with SDF-1 levels in plasma, suggesting that the SDF-1/CXCR4 axis might facilitate the migration of circulating B cells into tuberculous pleural space. Importantly, we observed that significantly more antibodies were produced by B cells in the PF following stimulation with BCG, early secretory antigenic target (ESAT-6)/culture filtrate protein-10 (CFP-10) or ESAT-6 protein. Collectively, these data demonstrate that Mycobacterium tuberculosis-specific B cells exist at local sites of infection in TP patients and this localization might influence the immune response to M. tuberculosis.