Evaluation of a Prototype of a Novel Galactomannan Sandwich Assay Using the VIDAS® Technology for the Diagnosis of Invasive Aspergillosis.

Objectives: To evaluate the analytical and clinical performance of a prototype of a VIDAS® Galactomannan (GM) unitary test (bioMérieux, Marcy l'Etoile, France) and compare to that of the Platelia™ Aspergillus Ag assay (Bio-Rad, CA, USA). Methods: Repeatability, reproducibility, and freeze-thaw stability of VIDAS®GM were evaluated. Sera from patients at risk of IA were concurrently tested with both the VIDAS®GM and Platelia™ Aspergillus Ag assays. Correlations between the two assays were assessed by Passing Bablok (PB) regression and performance by ROC analysis. Results: The correlations between the VIDAS®GM indexes after one and two cycles of freezing/thawing were r=1.00 and r=0.989, respectively. The coefficients of variation for negative, low-positive, and positive sera were 13%, 6%, and 5% for repeatability and 14.4%, 7.2%, and 5.5% for reproducibility. Overall, 126 sera were tested with both assays (44 fresh and 82 frozen). The correlation between VIDAS®GM and Platelia™ Aspergillus Ag was r=0.798. The areas under the curve of the ROC analyses were 0.892 and 0.894, for VIDAS®GM and Platelia™ Aspergillus Ag, respectively. Conclusions: This new VIDAS®GM prototype assay showed adequate analytical and clinical performance and a good correlation with that of Platelia™ Aspergillus Ag with 126 sera, although these results need to be confirmed in a larger prospective and multicentric study. As for the other VIDAS® assays, VIDAS®GM is a single-sample automated test using a solid reagent strip and receptacle. It is easy to use and suitable for rapid on-demand test results.

Performance Characteristics of the Vidas SARS-CoV-2 IgM and IgG Serological Assays.

The COVID-19 pandemic, caused by the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread worldwide. Serological testing for SARS-CoV-2-specific antibodies plays an important role in understanding and controlling the pandemic, notably through epidemiological surveillance. Well-validated and highly specific SARS-CoV-2 serological assays are urgently needed. We describe here the analytical and clinical performance of Vidas SARS-CoV-2 IgM and Vidas SARS-CoV-2 IgG, two CE-marked, emergency use authorization (EUA)-authorized, automated, qualitative assays for the detection of SARS-CoV-2-specific IgM and IgG, respectively. Both assays showed high within-run and within-laboratory precision (coefficients of variation < 11.0%) and very low cross-reactivity toward sera of patients with a past common coronavirus or respiratory virus infection. Clinical specificity determined on up to 989 prepandemic healthy donors was ≥99% with a narrow 95% confidence interval for both IgM and IgG assays. Clinical sensitivity was determined on up to 232 samples from 130 reverse transcriptase PCR (RT-PCR)-confirmed SARS-CoV-2 patients. The positive percent agreement (PPA) with SARS-CoV-2 PCR reached 100% at ≥16 days (Vidas SARS-CoV-2 IgM) and ≥32 days (Vidas SARS-CoV-2 IgG) of symptom onset. Combined IgM/IgG test results improved the PPA compared to each test alone. SARS-CoV-2 IgG seroconversion followed closely that of SARS-CoV-2 IgM and remained stable over time, while SARS-CoV-2 IgM levels rapidly declined. Interestingly, SARS-CoV-2-specific IgM and IgG responses were significantly higher in COVID-19 hospitalized versus nonhospitalized patients. Altogether, the Vidas SARS-CoV-2 IgM and IgG assays are highly specific and sensitive serological tests suitable for the reliable detection of past acute SARS-CoV-2 infections.

The kinetic profile and clinical implication of SCC-Ag in squamous cervical cancer patients undergoing radical hysterectomy using the Simoa assay: a prospective observational study.

BACKGROUND: To study the kinetic profile and clinicopathological implications of squamous cell carcinoma antigen (SCC-Ag) in cervical cancer patients who underwent surgery by a self-developed SCC-Ag single molecule assay (Simoa) prototype immunoassay. METHODS: Participants were prospectively enrolled between 04/2016 and 06/2017. Consecutive serum samples were collected at five points: day 0 (the day before surgery), postoperative day 4, weeks 2-4, months 2-4 and months 5-7. In total, 92 patients and 352 samples were included. The kinetic change in SCC-Ag levels and their associations with clinicopathological characteristics were studied. RESULTS: Simoa SCC-Ag was validated by comparison with the Architect assay. SCC-Ag levels measured by the Simoa assay were highly correlated with the Architect assay's levels (Pearson's correlation coefficient = 0.979, Passing-Bablok regression slope 0.894 (0.847 to 0.949), intercept - 0.009 (- 0.047 to 0.027)). The median values for each time-point detected by the Simoa assay were 2.49, 0.66, 0.61, 0.72, and 0.71 ng/mL, respectively. The SCC-Ag levels decreased dramatically after surgery and then stabilized and fluctuated to some extent within 6 months. Patients with certain risk factors had significantly higher SCC-Ag values than their negative counterparts before surgery and at earlier time points after surgery, while no difference existed at the end of observation. Furthermore, although patients with positive lymph nodes had sustained higher SCC-Ag levels compared to those with negative lymph nodes, similar kinetic patterns of SCC-Ag levels were observed after surgery. Patients who received postoperative treatment had significantly higher SCC-Ag values than those with surgery only at diagnosis, while no difference existed after treatment. CONCLUSIONS: The Simoa SCC-Ag prototype was established for clinical settings. The SCC-Ag levels were higher in patients with risk factors, whereas the kinetic trend of SCC-Ag might be mainly affected by postoperative adjuvant therapy. These data indicate that the SCC-Ag level might be a good predictor for the status of cervical cancer, including disease aggressiveness and treatment response.

Assessment of an ultra-sensitive IFNγ immunoassay prototype for latent tuberculosis diagnosis.

Worldwide there are about 1.7 billion individuals with latent tuberculosis infection (LTBI) and only 5% to 15% will develop active tuberculosis (TB). It is recommended to treat only those most at risk of developing active TB to avoid problems of drug resistance. LTBI diagnosis involves reviewing the individual's medical history, physical examination, and biological tests. Interferon gamma release assays (IGRA) can yield "undeterminate" or "uncertain" results, which makes clinical management decisions difficult. We assessed an ultra-sensitive immunoassay prototype based on single molecule array (SiMoA) technology to evaluate its overall performance, and in particular, its performance for indeterminate and uncertain positive or negative samples, as classified by the results from the current ELISA technique used for IFNγ quantification. We analyzed samples from hospitalized or consulting patients and healthcare workers from three hospitals in Paris, previously classified as negative (n = 30), positive (n = 35), uncertain negative (n = 25), uncertain positive (n = 31), or indeterminate (n = 30). We observed that with the SiMoA assay 83.3% of the indeterminate samples became interpretable and could be classified as negative, whereas 74% of uncertain positive samples were classified as positive. Most uncertain negative samples (72%) were reclassified as uncertain positive (68%) or positive (4%). The results suggest that the ultra-sensitive SiMoA IFNγ assay could represent a useful tool for the identification of true positive and negative samples among those giving indeterminate or uncertain results with the TB IGRA assay currently used.

Comparative evaluation of the VIDAS HIV DUO Ultra assay for combined detection of HIV-1 antigen and antibodies to HIV.

The aim of the study was to evaluate the performance of the combined antigen and antibody HIV screening assay VIDAS HIV DUO Ultra (BioMérieux, Marcy l'Etoile, France) in comparison with two other combined tests: the former version of the same test (VIDAS HIV DUO, BioMérieux) and the AxSYM HIV Ag/Ab Combo assay (Abbott Laboratories, Rungis, France). A prospective study was performed on serum specimens received on a routine basis for HIV testing: 1443 blood samples were tested with the three assays. Sensitivity was 100% for the three tests. Specificity assessed on repeated false-positive samples was 99.86, 99.03 and 99.65% for VIDAS HIV DUO Ultra, VIDAS HIV DUO and AxSYM HIV Ag/Ab Combo, respectively. In addition, 14 seroconversion panels were tested with the VIDAS DUO Ultra and AxSYM HIV Ag/Ab Combo assays. For four of these panels, a positive signal was detected one blood sampling point earlier with the VIDAS DUO Ultra assay, corresponding to a higher sensitivity of the HIV antigen test. These results indicate that the VIDAS HIV DUO Ultra exhibits an improved specificity with comparison to the former version of this assay and an excellent sensitivity for early detection of HIV seroconversion.

Mapping of B-cell epitopes in a Trypanosoma cruzi immunodominant antigen expressed in natural infections.

Tc40 is an immunodominant antigen present in natural Trypanosoma cruzi infections. This immunogen was thoroughly mapped by using overlapping amino acid sequences identified by gene cloning and chemical peptide synthesis. To map continuous epitopes of the Tc40 antigen, an epitope expression library was constructed and screened with sera from human chagasic patients. A major, linear B-cell epitope spanning residues 403 to 426 (PAKAAAPPAA) was identified in the central domain of Tc40. A synthetic peptide spanning this region reacted strongly with 89.8% of the serum samples from T. cruzi-infected individuals. This indicates that the main antigenic site is defined by the linear sequence of the peptide rather than a conformation-dependent structure. The major B-cell epitope of Tc40 shares a high degree of sequence identity with T. cruzi ribosomal and RNA binding proteins, suggesting the existence of cross-reactivity among these molecules.

Experimental transfection of Macaca sylvanus with cloned human hepatitis B virus.

Due to the absence of easily accessible animal models for the study of hepatitis B virus (HBV), the possibility of using Macaca sylvanus, a monkey originating from Morocco, North Africa, was investigated. Three monkeys were intrahepatically inoculated with a replication-competent head-to-tail HBV DNA plasmid dimer construct. The HBV surface antigen and HBV DNA were detected prior to alanine aminotransferase elevation in the serum of two of three HBV-inoculated monkeys at day 2 post-transfection and persisted for several weeks. This indicates that transfected animals developed markers of HBV infection. In addition, electron microscopy of the serum 3 weeks post-transfection showed the presence of virus particles whose shape and size were similar to complete 42 nm HBV Dane particles. Histological examination of liver tissues also revealed pathological changes not observed in uninfected controls, which strongly suggested acute hepatitis. HBV DNA was also detected by PCR in these monkey livers. Taken together, these results indicate that HBV can successfully replicate in this model and that M. sylvanus could be a potentially useful new primate model for the study of HBV replication.