Performance comparison of a flow cytometry immunoassay for intracellular cytokine staining and the QuantiFERON® SARS-CoV-2 test for detection and quantification of SARS-CoV-2-Spike-reactive-IFN-γ-producing T cells after COVID-19 vaccination.

PURPOSE: We compared the performance of an in-house-developed flow cytometry assay for intracellular cytokine staining (FC-ICS) and a commercially-available cytokine release assay (the QuantiFERON® SARS-CoV-2 Test [QF]) for detection and quantification of SARS-CoV-2-Spike (S)-reactive-IFN-γ-producing T cells after COVID-19 vaccination. PATIENTS AND METHODS: The sample included 141 individuals (all male; median age, 42 years; 20-72) who had been fully vaccinated with the Comirnaty® COVID-19 vaccine (at a median of 114 days; 34-145). Prior to vaccination, 91 were categorized as being SARS-CoV-2-naïve and 50 as SARS-CoV-2-experienced. A whole blood-based FC-ICS using 15-mer overlapping peptides encompassing the entire SARS-CoV-2 S protein was used for enumeration of virus-specific IFN-γ-producing CD4+ and CD8+ T cells. The QF test (Ag1 for CD4+ T cells and Ag2 for CD4+ and CD8+ T cells in combination) was carried out following the manufacturer's instructions. RESULTS: The FC-ICS and the QF assays returned significantly discordant qualitative results in both the entire cohort (P<0.001 with QF Ag1 and QF Ag2) and in SARS-CoV-2-naïve participants alone (P=0.005 and P=0.01, respectively). Discrepant results mostly involved FC-ICS positive/QF negative specimens. Overall, no correlation was found either between SARS-CoV-2 IFN-γ- CD4+ T-cell frequencies and IFN-γ levels measured in the QF Ag1 tube (P=0.78) or between the sum of SARS-CoV-2 IFN-γ CD4+ and CD8+ T-cell frequencies and IFN-γ levels quantified in the QF Ag2 tube. CONCLUSION: The data suggest a greater sensitivity for the FC-ICS assay than the QF test, and urge caution when comparing SARS-CoV-2 T-cell immune responses assessed using different analytical platforms.

Commercial Interferon-gamma release assay to assess the immune response to first and second doses of mRNA vaccine in previously COVID-19 infected versus uninfected individuals.

We analysed immunological response during vaccination by using quantitative anti-spike IgG antibodies (qAbs) and Interferon-gamma (IFNγ) production by SARS-CoV-2-specific CD4+ and CD8+ T cells (QuantiFERON® assay). Blood samples were collected at four time points: a day before the reception of first (T0) and second (T1) BNT162b2 doses, 14 (T2) and 28 days (T3) after second dose. Fifty individuals were included: 34 previously infected by SARS-CoV-2 (CoV2+) and 16 that were not (CoV2-). Among CoV2+, we only observed significant differences after the first dose in both qAbs and IFNγ+ T cells. CoV2- showed differences after each dose, and the response was lower than CoV2+. Older people presented a higher response in CoV2+, while in CoV2, young people responded best. Our results suggest that the second BNT162b2 vaccine dose is not a priority in people with previous COVID-19. QuantiFERON® is a good option to monitor T-cell immunity to SARS-CoV-2.

PCR detection of viral DNA in serum as an ancillary analysis for the diagnosis of acute mononucleosis-like syndrome due to human cytomegalovirus (HCMV) in immunocompetent patients.

BACKGROUND: Serologic tests are occasionally inconclusive for the diagnosis of mononucleosis-like syndrome due to human cytomegalovirus (HCMV). OBJECTIVES: To determine the value of viral DNA detection in serum by PCR as an ancillary test for the diagnosis of HCMV mononucleosis. STUDY DESIGN: Sera from 34 previously healthy individuals with HCMV mononucleosis, obtained within 1 month after the onset of symptoms, were assayed for viral DNA by three commercial PCRs (QCA gB, QCA MIE and Amplicor CMV Monitor). Sera from 30 patients with evidence of past HCMV infection served as controls. RESULTS: Viral DNA was detected in 20% of the samples from patients with HCMV mononucleosis by both QCA procedures, but in none of the controls. All samples tested negative by the Amplicor CMV Monitor. CONCLUSION: Analysis of sera for the presence of HCMV DNA is of limited value for the diagnosis of HCMV mononucleosis.

Comparison of BinaxNOW Influenza A&B assay and real-time reverse transcription polymerase chain reaction for diagnosis of influenza A pandemic (H1N1) 2009 virus infection in adult patients.

The BinaxNOW Influenza A&B assay was evaluated for the diagnosis of influenza A pandemic (H1N1) 2009 virus infection in 354 adult patients. The sensitivity, specificity, and positive and negative predictive values were 32%, 100%, 100%, and 67%, respectively. The analytic sensitivity of the assay was log105.0 tissue culture infective dose (TCID)50/mL.

Sensitivity of a marketed immunochromatographic assay specifically targeting the pandemic influenza A/H1N1 2009 virus.

The sensitivity of an immunochromatographic assay specifically detecting the pandemic influenza A/H1N1 2009 virus (influenza Ag A/B/A(H1N1) pandemic rapid test; SD Standard Diagnostics, South Korea) was evaluated. The overall sensitivity of the assay and its analytic sensitivity were 26.9% and 2.6 x 10(4) TCID(50)/mL, respectively.

Concurrent detection of human herpesvirus type 6 and measles-specific IgMs during acute exanthematic human parvovirus B19 infection.

A familial outbreak of human parvovirus B19 infection is described in which serological tests carried out routinely for determining the causal agent of febrile rashes of viral etiology failed to yield a definitive diagnosis. Concurrent detection of serum IgMs to parvovirus B19 and to heterologous viruses such as human herpesvirus type 6 (HHV-6) and measles virus complicated interpretation of the data. IgG avidity tests and investigation and testing for the presence of viral DNA in sera by PCR were required to confirm parvovirus B19. The study stresses the importance of avidity and PCR tests to obtain a firm diagnosis of febrile exanthematic viral diseases.