Alessandro Matarese

Multifunctional CD4+ T cells correlate with active Mycobacterium tuberculosis infection

Th1 CD4+ T cells and their derived cytokines are crucial for protection against Mycobacterium tuberculosis. Using multiparametric flow cytometry, we have evaluated the distribution of seven distinct functional states (IFN‐γ/IL‐2/TNF‐α triple expressors, IFN‐γ/IL‐2, IFN‐γ/TNF‐α or TNF‐α/IL‐2 double expressors or IFN‐γ, IL‐2 or TNF‐α single expressors) of CD4+ T cells in individuals with latent M. tuberculosis infection (LTBI) and active tuberculosis (TB). We found that triple expressors, while detectable in 85–90%TB patients, were only present in 10–15% of LTBI subjects. On the contrary, LTBI subjects had significantly higher (12‐ to 15‐fold) proportions of IL‐2/IFN‐γ double and IFN‐γ single expressors as compared with the other CD4+ T‐cell subsets. Proportions of the other double or single CD4+ T‐cell expressors did not differ between TB and LTBI subjects. These distinct IFN‐γ, IL‐2 and TNF‐α profiles of M. tuberculosis‐specific CD4+ T cells seem to be associated with live bacterial loads, as indicated by the decrease in frequency of multifunctional T cells in TB‐infected patients after completion of anti‐mycobacterial therapy. Our results suggest that phenotypic and functional signatures of CD4+ T cells may serve as immunological correlates of protection and curative host responses, and be a useful tool to monitor the efficacy of anti‐mycobacterial therapy.

Analysis of Mycobacterium tuberculosis-specific CD8 T-cells in patients with active tuberculosis and in individuals with latent infection.

CD8 T-cells contribute to control of Mycobacterium tuberculosis infection, but little is known about the quality of the CD8 T-cell response in subjects with latent infection and in patients with active tuberculosis disease. CD8 T-cells recognizing epitopes from 6 different proteins of Mycobacterium tuberculosis were detected by tetramer staining. Intracellular cytokines staining for specific production of IFN-γ and IL-2 was performed, complemented by phenotyping of memory markers on antigen-specific CD8 T-cells. The ex-vivo frequencies of tetramer-specific CD8 T-cells in tuberculous patients before therapy were lower than in subjects with latent infection, but increased at four months after therapy to comparable percentages detected in subjects with latent infection. The majority of CD8 T-cells from subjects with latent infection expressed a terminally-differentiated phenotype (CD45RA+CCR7−). In contrast, tuberculous patients had only 35% of antigen-specific CD8 T-cells expressing this phenotype, while containing higher proportions of cells with an effector memory- and a central memory-like phenotype, and which did not change significantly after therapy. CD8 T-cells from subjects with latent infection showed a codominance of IL-2+/IFN-γ+ and IL-2−/IFN-γ+ T-cell populations; interestingly, only the IL-2+/IFN-γ+ population was reduced or absent in tuberculous patients, highly suggestive of a restricted functional profile of Mycobacterium tuberculosis-specific CD8 T-cells during active disease. These results suggest distinct Mycobacterium tuberculosis specific CD8 T-cell phenotypic and functional signatures between subjects which control infection (subjects with latent infection) and those who do not (patients with active disease).

Limited usefulness of QuantiFERON-TB Gold In-Tube for monitoring anti-tuberculosis therapy.

The usefulness of IFN-gamma release assays to monitor the efficacy of anti-tuberculosis (TB) treatment is controversial. Sixty patients affected by culture-confirmed pulmonary TB (M = 36; mean age: 39.2 yr; Italians = 28) were serially tested in a low prevalence setting by means of QuantiFERON-TB GOLD In-Tube (QFT-IT) at baseline and after a successful six-month therapy regimen (T6). A sub-group of 40 cases was also tested at 1 and 3 months. Overall, 88.3% of patients scored a QFT-IT positive result at baseline, with the higher proportion of TB-specific IFN-gamma responses in foreign-born patients (p = 0.04). TB-specific responses were highly variable over time, the within-person variability being correlated with baseline IFN-gamma levels (r = 0.731; p < 0.001). Overall, 61.6% of cases still tested QFT-IT positive at the completion of therapy. Average IFN-gamma levels increased over time, being persistently significantly higher in Italian patients than in foreign-born cases both at baseline (p = 0.03) and at T6 (p = 0.02). Reversion mainly occurred in patients (26.6%) with baseline IFN-gamma levels close to the conventional cut-off value. No indeterminate results were recorded at any study time point. In conclusion, QFT-IT adds no significant information to clinicians for treatment monitoring when applied in routine clinical practice in a low prevalence setting. Kinetics of T cell responses upon TB treatment and reversion (and conversion) thresholds need to be addressed. Diversity of IFN-gamma responses among patients of different geographic origin is an issue to be investigated further.

Prevention of Tuberculosis in Patients Taking Tumor Necrosis Factor-α, Blockers

Treatment with tumor necrosis factor–α (TNF–α) inhibitors increases the risk of tuberculosis (TB) due to reactivation of latent Mycobacterium tuberculosis infection (LTBI). Screening for LTBI is based mainly on the tuberculin skin test (TST), which has several limitations in any patient who is immunosuppressed due to drugs or autoimmune disease. T cell interferon–γ release assays (IGRA) have been shown to be more specific than TST in immunocompetent patients and potentially represent a new approach for the management of patients taking TNF–α blockers. Even if there is no evidence-based literature of IGRA superiority versus TST in this specific clinical setting, some studies suggest blood assays may be helpful in clinical management of these patients, in addition to currently recommended clinical screening for risk factors for LTBI.

IFN-γ release assays in tuberculosis management in selected high-risk populations

Tuberculosis (TB) is the most deadly infectious disease in the world. TB control relies on passive case findings and targeted treatment of latently infected individuals at high risk of disease progression. Tuberculin skin testing (TST) is conventionally used for detection of TB infection. Recently, blood assays measuring the release of IFN-γ by TB-specific effector memory T cells have been developed to overcome TST limitations. Overall, IFN-γ release assays are more specific than TST, more sensitive in detecting active TB and correlate better with TB exposure in immune-competent patients, at least in low-burden settings. There are three US FDA-approved assays commercially available: the ELISpot-based assay T-SPOT.TB® (Oxford Immunotech, UK) and two ELISA-based formats, QuantiFERON® TB Gold (QFT) and QFT-in tube (Cellestis, Australia). Recent international guidelines and consensus statements recommend the use of IFN-γ release assays at different levels in TB management. However, conclusive evidence-based information targeting populations at high TB risk, including HIV-infected individuals, children and patient candidates for biotherapy with TNF-α blockers, are lacking. The aim of this review is to focus our attention on studies addressing the performance of commercial IFN-γ release assays in clinical management of TB infection in these highly selected settings to provide a more comprehensive picture of the actual scenario and to identify areas to be investigated further.

Screening and monitoring of latent tubercular infection in patients taking tumor necrosis factor-α blockers for psoriatic arthritis.

Patients with arthritis who need treatment with biologics are carefully screened for possible previous exposure to tuberculosis to detect any latent tubercular infection (LTBI). The traditional method of screening for LTBI is not specific, because positivity could also depend on infection by atypical mycobacteria and bacillus Calmette-Guerin vaccination. In addition, the screening does not show high sensitivity, frequently presenting a false negativity because of immunosuppression caused by drugs used for arthritis. Recently, interferon-γ release assays (IGRA) have been used to screen LTBI with more sensitivity and specificity before treatment with anti-tumor necrosis factor-α drugs. Moreover, in our experience, IGRA are potentially useful in monitoring LTBI during biologic therapy.

Comparison of tuberculin skin test and interferon-γ assays in patients with moderate to severe psoriasis who are candidates for antitumour necrosis factor-α therapy

the Mann–Whitney test. The point prevalence of AD was determined at 19 locations in a large area in central Netherlands. The prevalence of AD in Dutch children younger than 4 years was 7Æ5%. More boys than girls were affected (P < 0Æ0005), and the prevalence of AD was greater in younger (< 2 years) than in older children (Fig. 1). Most of the children were white skinned. The mean TIS score was 3 both in boys and in girls with AD (P = 0Æ63), and in groups of different ages (P = 0Æ48). This is the first study on the prevalence and severity of AD in Dutch children aged 0–4 years. The point prevalence was 7Æ5%, and 1 in 10 (10%) was referred to a general practitioner. There were more boys than girls with AD. This difference was particularly marked at the age of < 2 years. The severity of AD was equally distributed over age and gender. Atopy and eczema develop differently in boys and girls. Boys with AD are more often atopic than girls, who more often have intrinsic AD. It may be assumed that the observed prevalence of AD in this age group reflects the real situation, as does the level of severity at which medical aid is sought.

Usefulness of IFN-gamma release assays in clinical management of difficult TB cases: Evidence from clinical practice

Performance of T-SPOT.TB™ (TS-TB) and QuantiFERON TB Gold-In tube (QFT-IT) assays was evaluated for detection of M. tuberculosis (Mtb) infection in patients with suspected extra-pulmonary or smear-negative pulmonary tuberculosis (TB) in a low prevalence country. Twenty-one out of 35 patients were affected by active TB. Mtb culture isolation was achieved in 76% of cases. Tuberculin skin testing (TST), TS-TB, and QFT-IT yielded a positive result in 67%, 95% and 81% of cases, respectively. Agreement of interferon-γ release assays and TST was 70% (κ=0.18 for TS-TB; κ=0.46 for QFT-IT). Increased sensitivity of blood assays (>80%) improved diagnostic evaluation of difficult TB cases.

Current Treatment Options for Latent Tuberculosis Infection

Treatment of latent tuberculosis infection (LTBI) is a key component in TB control strategies worldwide. However, as people with LTBI are neither symptomatic nor contagious, any screening decision should be weighed carefully against the potential benefit of preventing active disease in those who are known to be at higher risk and are willing to accept therapy for LTBI. This means that a targeted approach is desirable to maximize cost effectiveness and to guarantee patient adherence. We focus on LTBI treatment strategies in patient populations at increased risk of developing active TB, including candidates for treatment with tumor necrosis factor-α blockers. In the last 40 years, isoniazid (INH) has represented the keystone of LTBI therapy across the world. Although INH remains the first therapeutic option, alternative treatments that are effective and associated with increased adherence and economic savings are available. Current recommendations, toxicity, compliance, and cost issues are discussed in detail in this review. A balanced relationship between the patient and healthcare provider could increase adherence, while cost-saving treatment strategies with higher effectiveness, fewer side effects, and of shorter duration should be offered as preferred.