Multicentre Performance Evaluation of the Elecsys Anti-SARS-CoV-2 Immunoassay as an Aid in Determining Previous Exposure to SARS-CoV-2

Introduction We performed a multicentre evaluation of the Elecsys® Anti-SARS-CoV-2 immunoassay (Roche Diagnostics), an assay utilising a recombinant protein representing the nucleocapsid (N) antigen, for the in vitro qualitative detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods Specificity was evaluated using serum/plasma samples from blood donors and routine diagnostic specimens collected before September 2019 (i.e., presumed negative for SARS-CoV-2-specific antibodies); sensitivity was evaluated using samples from patients with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection. Point estimates and 95% confidence intervals (CIs) were calculated. Method comparison was performed versus commercially available assays. Results Overall specificity for the Elecsys Anti-SARS-CoV-2 immunoassay (n = 9575) was 99.85% (95% CI 99.75–99.92): blood donors (n = 6714; 99.82%), routine diagnostic specimens (n = 2861; 99.93%), pregnant women (n = 2256; 99.91%), paediatric samples (n = 205; 100.00%). The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated significantly higher specificity versus LIAISON SARS-CoV-2 S1/S2 IgG (99.71% vs. 98.48%), EUROIMMUN Anti-SARS-CoV-2 IgG (100.00% vs. 94.87%), ADVIA Centaur SARS-CoV-2 Total (100.00% vs. 87.32%) and iFlash SARS-CoV-2 IgM (100.00% vs. 99.58%) assays, and comparable specificity to ARCHITECT SARS-CoV-2 IgG (99.75% vs. 99.65%) and iFlash SARS-CoV-2 IgG (100.00% vs. 100.00%) assays. Overall sensitivity for Elecsys Anti-SARS-CoV-2 immunoassay samples drawn at least 14 days post-PCR confirmation (n = 219) was 93.61% (95% CI 89.51–96.46). No statistically significant differences in sensitivity were observed between the Elecsys Anti-SARS-CoV-2 immunoassay versus EUROIMMUN Anti-SARS-CoV-2 IgG (90.32% vs. 95.16%) and ARCHITECT SARS-CoV-2 IgG (84.81% vs. 87.34%) assays. The Elecsys Anti-SARS-CoV-2 immunoassay showed significantly lower sensitivity versus ADVIA Centaur SARS-CoV-2 Total (85.19% vs. 95.06%) and iFlash SARS-CoV-2 IgG (86.25% vs. 93.75%) assays, but significantly higher sensitivity versus the iFlash SARS-CoV-2 IgM assay (86.25% vs. 33.75%). Conclusion The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated very high specificity and high sensitivity in samples collected at least 14 days post-PCR confirmation of SARS-CoV-2 infection, supporting its use to aid in determination of previous exposure to SARS-CoV-2

Prevalence of SARS-CoV-2 antibodies in healthy blood donors from the state of Tyrol, Austria, in summer 2020.

BACKGROUND: Seroepidemiological studies provide important insight into the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV‑2) in our society. We aimed to determine seropositivity of SARS-CoV‑2 antibodies and its cross-sectional correlates in a large cohort of blood donors. METHODS: In this observational cohort study, we tested healthy blood donors residing in Tyrol, Austria, for SARS-CoV‑2 antibodies using the Abbott SARS-CoV‑2 IgG chemiluminescent microparticle immunoassay. We estimated 95% confidence intervals (95% CI) of seroprevalences using bootstrapping and tested for differences by participant characteristics using logistic regression. FINDINGS: Between 8 June and 4 September 2020, we screened 5345 healthy individuals at local blood donor sessions (mean age 42.7 years, SD 13.5 years, 46.7% female). Overall seroprevalence was 3.1% (95% CI 2.7-3.6%, 165 cases), which is 5.1-fold higher (95% CI 4.5-6.0%) than the case number identified by the health authorities in the state-wide testing program (0.6%; 4536 out of 757,634). Seroprevalence was higher in the district Landeck (16.6%, P < 0.001) and in individuals aged < 25 years (4.7%, P = 0.043), but did not differ by gender, blood types, or medication intake. The odds ratio for seropositivity was 2.51 for participants who had travelled to Ischgl (1.49-4.21, P = 0.001), 1.39 who had travelled to other federal states (1.00-1.93, P = 0.052), and 2.41 who had travelled abroad (1.61-3.63, P < 0.001). Compared to participants who had a suspected/confirmed SARS-CoV‑2 infection but were seronegative, seropositive participants more frequently reported loss of smell (odds ratio = 2.49, 1.32-4.68, P = 0.005) and taste (odds ratio = 2.76, 1.54-4.92, P = 0.001). CONCLUSION: In summer 2020, SARS-CoV‑2 seroprevalence in Tyrolean blood donors was 3.1%. Our study revealed regional variation and associations with young age, travel history and specific symptoms

Genetic diversity of KELnull and KELel: a nationwide Austrian survey

BACKGROUND: Besides ABO and RH, the KEL blood group system, including the two antithetical antigens KEL1 and KEL2, is the most important owing to the frequent appearance of anti-KEL alloantibodies and their considerable clinical significance. So far, only limited information was available on KEL variant alleles determining the rare silent KELnull and KELel phenotypes with absent or diminished KEL antigen expression detected only by adsorption-elution techniques, respectively. STUDY DESIGN AND METHODS: For a systematic investigation of the KELnull and KELel phenotypes, 401 KEL:1,-2 samples (representing 2.6% of all Austrian KEL:1,-2 samples) and 811 KEL:1,2 samples were genotyped for the KEL*1/KEL*2-specific single-nucleotide polymorphism. All heterozygous KEL*1/KEL*2 and 4 additional KELnull samples were subjected to detailed immunohematologic examination and allele-specific sequencing. RESULTS: In 14 KEL:1,-2 samples, discrepant KEL*1/KEL*2 heterozygosity was observed, indicating the presence of silent or barely expressed KEL*2 alleles, whereas all KEL:1,2 individuals were homozygous for KEL*2. In the course of further molecular analysis, 8 novel KEL*2null and 2 KEL*2el alleles were discovered, representing 67 and 33 percent of previously known KEL*2null- and KEL*2el-encoding alleles, respectively. In addition, two different known KEL*2null and KEL*2el alleles each were confirmed. The immunohematologic properties of KEL variant red blood cells were defined by extended KEL phenotyping and flow cytometric KEL1, KEL2, KEL4, and KEL7 antigen as well as total Kell protein quantification. CONCLUSION: For the first time, exact KELnull and KELel population frequencies could be established in this population

Antibodies attenuate the capacity of dendritic cells to stimulate HIV-specific cytotoxic T lymphocytes

International audienceBACKGROUND: Control of HIV is suggested to depend on potent effector functions of the virus-specific CD8(+) T-cell response. Antigen opsonization can modulate the capture of antigen, its presentation, and the priming of specific CD8(+) T-cell responses. OBJECTIVE: We have previously shown that opsonization of retroviruses acts as an endogenous adjuvant for dendritic cell (DC)-mediated induction of specific cytotoxic T lymphocytes (CTLs). However, in some HIV-positive subjects, high levels of antibodies and low levels of complement fragments coat the HIV surface. METHODS: Therefore we analyzed the effect of IgG opsonization on the antigen-presenting capacity of DCs by using CD8(+) T-cell proliferation assays after repeated prime boosting, by measuring the antiviral activity against HIV-infected autologous CD4(+) T cells, and by determining IFN-γ secretion from HIV-specific CTL clones. RESULTS: We find that DCs exposed to IgG-opsonized HIV significantly decreased the HIV-specific CD8(+) T-cell response compared with the earlier described efficient CD8(+) T-cell activation induced by DCs loaded with complement-opsonized HIV. DCs exposed to HIV bearing high surface IgG levels after incubation in plasma from HIV-infected subjects acted as weak stimulators for HIV-specific CTL clones. In contrast, HIV opsonized with plasma from patients exhibiting high complement and low IgG deposition on the viral surface favored significantly higher activation of HIV-specific CD8(+) T-cell clones. CONCLUSION: Our ex vivo and in vitro observations provide the first evidence that IgG opsonization of HIV is associated with a decreased CTL-stimulatory capacity of DCs

Multicenter Evaluation of a New Automated Fourth-Generation Human Immunodeficiency Virus Screening Assay with a Sensitive Antigen Detection Module and High Specificity

Fourth-generation assays for the simultaneous detection of human immunodeficiency virus (HIV) antigen and antibody that were available on the international market until now have antigen detection modules with relatively poor sensitivity and produce a higher rate of false-positive results than third-generation enzyme immunoassays (EIAs). The new Cobas Core HIV Combi EIA with an improved sensitivity for HIV p24 antigen was compared to alternative fourth- and third-generation assays, the p24 antigen test, and HIV type 1 (HIV-1) RNA reverse transcriptase PCR (RT-PCR). A total of 94 seroconversion panels (n = 709 sera), samples from the acute phase of infection after seroconversion (n = 32), anti-HIV-1-positive specimens (n = 730) from patients in different stages of the disease, 462 subtyped samples from different geographical locations, anti-HIV-2-positive sera (n = 302), dilutions of cell culture supernatants (n = 62) from cells infected with different HIV-1 subtypes, selected performance panels from Boston Biomedica Inc., 7,579 unselected samples from blood donors, 303 unselected daily routine samples, 997 specimens from hospitalized patients, and potentially interfering samples (n = 1,222) were tested with Cobas Core HIV Combi EIA. The new assay showed a sensitivity comparable to that of the Abbott HIV-1 AG Monoclonal A for early detection of HIV infection in seroconversion panels. The mean time delay of Cobas Core HIV Combi EIA (last negative sample plus 1 day) in comparison to that for HIV-1 RT-PCR for 87 panels tested with both methods was 2.75 days. The diagnostic window was reduced with Cobas Core HIV Combi EIA by between 3.6 and 5.7 days from that for third-generation assays. The specificities of Cobas Core HIV Combi EIA in blood donors were 99.84 and 99.85% (after repeated testing). Overall, 30 repeatedly reactive false-positive results out of 10,031 HIV-negative samples were obtained with Cobas Core HIV Combi EIA. Our results show that a fourth-generation assay with improved specificity such as Cobas Core HIV Combi EIA is suitable for blood donor screening because of its low number of false positives and because it detects HIV p24 antigen with a sensitivity comparable to that of single-antigen assays