Paola Mantegani

Survey of 150 strains belonging to the Mycobacterium terrae complex and description of Mycobacterium engbaekii sp. nov., Mycobacterium heraklionense sp. nov. and Mycobacterium longobardum sp. nov.

A thorough phenotypic and genotypic analysis of 150 strains belonging to the Mycobacterium terrae complex resulted in the identification of a number of previously unreported sequevars (sqvs) within the species known to belong to the complex. For the species Mycobacterium arupense, three sqvs were detected in the 16S rRNA gene, six sqvs in the hsp65 gene and 15 sqvs in the rpoB gene; in Mycobacterium senuense two sqvs were present in each of the three genetic regions; in Mycobacterium kumamotonense four, two and nine sqvs were found, respectively, and in M. terrae three, four and six sqvs were found, respectively. The inappropriate inclusion of Mycobacterium triviale within the M. terrae complex was confirmed. The limited utility of biochemical tests and of mycolic acid analyses for the differentiation of the members of M. terrae complex was also confirmed. The survey allowed the recognition of three previously undescribed species that were characterized by unique sequences in the 16S rRNA, hsp65 and rpoB genes. Mycobacterium engbaekii sp. nov. (proposed previously 40 years ago but never validly published) was characterized by pink photochromogenic pigmentation and rapid growth; phylogenetically it was related to Mycobacterium hiberniae. The type strain of this species, of which eight strains were investigated, is ATCC 27353(T) ( = DSM 45694(T)). A cluster of 24 strains was the basis for the description of Mycobacterium heraklionense sp. nov., which has an intermediate growth rate and is unpigmented; nitrate reductase activity is typically strong. Closely related to M. arupense with respect to the 16S rRNA gene, M. heraklionense sp. nov. could be clearly differentiated from the latter species in the other genetic regions investigated. The type strain is NCTC 13432(T) ( = LMG 24735(T) = CECT 7509(T)). Mycobacterium longobardum sp. nov., represented in the study by seven strains, was characterized by a unique phylogenetic location within the M. terrae complex, clearly divergent from any other species. The type strain is DSM 45394(T) ( = CCUG 58460(T)).

GenoType MTBDRsl performance on clinical samples with diverse genetic background

We evaluate the performance of the GenoType® MTBDRsl (Hain Lifescience Nehren, Germany) for the detection of second-line resistant tuberculosis and we correlate the frequency of mutations to different Mycobacterium tuberculosis genotypes. We tested 175 strains and 59 clinical specimens interpreting the results according to the Standards for Reporting of Diagnostic Accuracy recommendations. All the strains were also investigated by spoligotyping and Mycobacterial Interspersed Repetitive Units–Variable Number of Tandem Repeats typing. The performances of the MTBDRsl in detecting resistance to fluoroquinolones (FQ), second-line injectable drugs (SLID), and ethambutol (EMB) on clinical isolates were similar (specificity ∼99%, sensitivity ∼70%, and positive predictive value (PPV) ∼99%). Of the 59 respiratory specimens, three samples were classified as “indeterminate”. The specificity in detecting resistances was similar for FQs and EMB 100% (95% CI 92.7–100%) and 100% (95% CI 83.9–100%), respectively with a PPV of 100% (95% CI 64.6–100%) and 100% (95% CI 87.9–100%), respectively. Detection of SLID showed a specificity of 89.1% (95% CI 77.0–95.3%) and a PPV of 58.3% (95% CI 32.0–80.7%). Sensitivity for FQ-resistance detection was 100% (95% CI 64.6–100%), whereas for SLID and EMB it was 89.1% (95% CI 77.0-95.3%) and 86.1% (95% CI 71.3-93.9%), respectively. We detected a significant association between mutations in the rrs gene and Beijing lineage. The MTBDRsl can be used to “rule in” extensively drug-resistant strains of tuberculosis in a high risk group; the low sensitivity and negative predicted value (NPV) make confirmation by conventional drug susceptibility testing mandatory when mutations are not identified. NPV for SLID is higher in Beijing strains, showing that the predictive values of the molecular tests are related to the genetic background.

Perturbation of the natural killer cell compartment during primary human immunodeficiency virus 1 infection primarily involving the CD56bright subset

We investigated the distribution of natural killer (NK) cell subsets, their activating and inhibitory receptors, and their cytolytic potential, in primary human immunodeficiency virus (HIV)‐infected (PHI) individuals at baseline and during 1 year of follow‐up with or without antiretroviral therapy, and compared the results with those obtained in treatment‐naïve, chronically HIV‐infected (CHI) individuals, and HIV‐seronegative (HN) healthy individuals. The proportion of the CD56dim and CD56bright subsets decreased with disease progression, whereas that of the CD56− CD16+ subset increased. In the CD56dim subset, the proportion of cells with natural cytotoxicity receptors (NCRs) decreased with disease progression, and their cytolytic potential was reduced. Conversely, the CD56bright subset was characterized by a high proportion of NCR‐positive, killer cell immunoglobulin‐like receptor (KIR)‐positive NKG2A+ cells in both CHI and PHI individuals, which was associated with an increase in their cytolytic potential. During the 1 year of follow‐up, the PHI individuals with high viraemia levels and low CD4+ T‐cell counts who received highly active antiretroviral therapy (HAART) had a similar proportion of NK subsets to CHI individuals, while patients with low viraemia levels and high CD4+ T‐cell counts who remained untreated had values similar to those of the HN individuals. Our results indicate a marked perturbation of the NK cell compartment during HIV‐1 infection that is multifaceted, starts early and is progressive, primarily involves the CD56bright subset, and is partially corrected by effective HAART.

Altered distribution of natural killer cell subsets identified by CD56, CD27 and CD70 in primary and chronic human immunodeficiency virus-1 infection

Human natural killer (NK) (CD3− CD56+) cells can be divided into two functionally distinct subsets, CD3− CD56dim and CD3− CD56bright. We analysed the distribution of NK cell subsets in primary and chronic human immunodeficiency virus‐1 (HIV‐1) infection, to determine if HIV infection stage may influence the subset distribution. In primary infection, contrary to chronic infection, the CD3− CD56dim subset was expanded compared to healthy controls. We also studied the effect of antiretroviral therapy administered early in infection and found that NK cell subset distribution was partially restored after 6 months of antiretroviral therapy in primary infection, but not normalized. Recently, NK cells have been divided into CD27− and CD27+ subsets with different migratory and functional capacity and CD27‐mediated NK cell activation has been described in mice. We therefore investigated whether CD27 and/or CD70 (CD27 ligand) expression on NK cells, and thus the distribution of these novel NK subsets, was altered in HIV‐1‐infected patients. We found up‐regulated expression of both CD27 and CD70 on NK cells of patients, resulting in higher proportions of CD27high and CD70high NK cells, and this phenomenon was more pronounced in chronic infection. Experiments conducted in vitro suggest that the high interleukin‐7 levels found during HIV‐1 infection may participate in up‐regulation of CD70 on NK cell subsets. Imbalance of NK cell subsets and up‐regulated expression of CD27 and CD70 initiated early in HIV‐1 infection may indicate NK cell activation and intrinsic defects initiated by HIV‐1 to disarm the innate immune response to the virus.

An In-House RD1-Based Enzyme-Linked Immunospot-Gamma Interferon Assay Instead of the Tuberculin Skin Test for Diagnosis of Latent Mycobacterium tuberculosis Infection

ABSTRACT Identification of individuals infected with Mycobacterium tuberculosis is essential for the control of tuberculosis (TB). The specificity of the currently used tuberculin skin test (TST) is poor because of the broad antigenic cross-reactivity of purified protein derivative (PPD) with BCG vaccine strains and environmental mycobacteria. Both ESAT-6 and CFP-10, two secretory proteins that are highly specific for M. tuberculosis complex, elicit strong T-cell responses in subjects with TB. Using an enzyme-linked immunospot (ELISPOT)-IFN-γ assay and a restricted pool of peptides derived from ESAT-6 and CFP-10, we have previously demonstrated a high degree of specificity and sensitivity of the test for the diagnosis of TB. Here, 119 contacts of individuals with contagious TB who underwent TST and the ELISPOT-IFN-γ assay were consecutively recruited. We compared the efficacy of the two tests in detecting latent TB infection and defined a more appropriate TST cutoff point. There was little agreement between the tests (k = 0.33, P < 0.0001): 53% of the contacts with a positive TST were ELISPOT negative, and 7% with a negative TST were ELISPOT positive. Furthermore, respectively 76 and 59% of the ELISPOT-negative contacts responded in vitro to BCG and PPD, suggesting that most of them were BCG vaccinated or infected with nontuberculous mycobacteria. The number of spot-forming cells significantly correlated with TST induration (P < 0.0001). Our in-house ELISPOT assay based on a restricted pool of highly selected peptides is more accurate than TST for identifying individuals with latent TB infection and could improve chemoprophylaxis for the control of TB.

ELISPOT-IFN-γ assay instead of tuberculin skin test for detecting latent Mycobacterium tuberculosis infection in rheumatic patients candidate to anti-TNF-α treatment

In rheumatic patients candidate to anti-TNF-α treatment, there is an increased risk of developing tuberculosis (TB). The tuberculin skin test (TST), the standard diagnostic test for latent tuberculosis infection (LTBI), suffers low specificity and sensitivity. Here, we compared the performance characteristics of an in-house ELISPOT-IFN-γ assay (using a restricted pool of Mycobacterium tuberculosis-specific peptides or MTP) to TST for the diagnosis of LTBI in 69 rheumatic patients candidate to anti-TNF-α treatment and in 60 healthy LTBI individuals. Among the 69 patients enrolled, 17 (25%) had a positive TST response and 15 (22%) a positive ELISPOT-MTP response. Among the patients with a positive TST result, eight had a positive and nine a negative ELISPOT-MTP response, whereas among the 49 patients with a negative TST result, 42 were ELISPOT-MTP negative, but seven (14%) were ELISPOT-MTP positive, with three indeterminate results. The agreement between the two tests was poor (k = 0.341, 95% CI = 0.060 to 0.622) and the test of symmetry was not significant (P = 0.8). Considering the ELISPOT assay, rheumatic patients had a reduced number of spot-forming cells after stimulation of lymphocytes with PHA or PPD when compared with healthy LTBI individuals. Thus, the ELISPOT-IFN-γ assay performs better than the TST in recognizing patients with LTBI, on one hand reducing the number of patients submitted to isoniazid prophylaxis, and on the other hand, since the assay is less biased by immunosuppressive regimens than TST, recognizing LTBI patients among those with a negative TST response.

Clinical application of an in-house ELISPOT assay in patients with suspicious tuberculous uveitis and no signs of active tuberculosis

Purpose The purpose of this study is to evaluate the rate of Mycobacterium tuberculosis infection in uveitis patients using an ELISPOT-IFN-γ (ELISPOT-MTP) assay and a tuberculin skin test (TST). Methods Fifty-three patients with suspicious tuberculous uveitis, seen at the Ocular Immunology and Uveitis Service, Scientific Institute San Raffaele, Milan, Italy, were compared with 233 healthy control subjects. All uveitis patients, together with healthy control subjects, underwent in-house ELISPOT-MTP assay and then the TST. Results None of the patients had signs of active tuberculosis. A total of 75.5% of uveitis patients showed positive TST reaction while 58.5% responded positively to ELISPOT-MTP. In healthy individuals, these responses were 30.5% and 25.3%, respectively (p<0.0001). In a different diagnosis subset, TST and ELISPOT positivity were, respectively, 80% and 50% in anterior uveitis; 75% and 50% in intermediate uveitis; 100% and 87.5% in serpiginous-like choroiditis; 90% and 80% in posterior uveitis; and 57.1% and 42.9% in panuveitis. Serpiginous-like choroiditis and posterior uveitis patients had a higher number of ELISPOT-MTP positive results and a higher grade of intensity of ELISPOT-MTP responses compared to healthy control subjects (p=0.0098). Conclusions Our uveitis patients had higher M tuberculosis infection rate and grade of intensity response than healthy control subjects detected by ELISPOT-MTP. This response is statistically significant and higher in patients with serpiginous-like choroiditis and posterior uveitis.

Interleukin-7 Unveils Pathogen-Specific T Cells by Enhancing Antigen-Recall Responses

IL-7 supports host immunity in lymphopenic and immunosuppressed patients and expands tumor-reactive T cells for adoptive immunotherapy. Here, we report that IL-7 also enables the accumulation of clinically relevant pathogen-reactive T cells from TB-, CMV-, and Candida albicans-infected individuals.