We aimed to evaluate the LIAISON^® SARS-CoV-2 antigen assay (DiaSorin), comparing its performance to real-time polymerase chain reaction (RT-PCR) for the detection of SARS-CoV-2 RNA. 182 (110 PCR-positive and 72 PCR-negative) nasopharyngeal swab samples were taken for the detection of SARS-CoV-2. RT-PCR and antigen assay were performed using the same material. The sensitivity and specificity of the antigen assay were calculated for different cut-offs, with RT-PCR serving as the reference method. Stored clinical samples that were positive for other respiratory viruses were tested to evaluate cross-reactivity. One third (33/110, 30%) were falsely classified as negative, while no false positives were found using the 200 TCID₅₀/mL cut-off for the SARS-CoV-2 antigen as proposed by the manufacturer. This corresponded to a sensitivity of 70% (60–78%) and a specificity of 100% (94–100%). Lowering the cut-off for positivity of the antigen assay to 22.79 or 57.68 TCID₅₀/mL increased the sensitivity of the method, reaching a sensitivity of 92% (85–96%) vs. 79% (70–86%) and a specificity of 81% (69–89%) vs. 99% (91–100%), respectively. The antigen assay reliably detected samples with high SARS-CoV-2 viral loads (≥10⁶ copies SARS-CoV-2/mL), while it cannot differentiate between negative and low positive samples. Cross-reactivity toward other respiratory viruses was not detected.

To estimate protection from cytomegalovirus (CMV) replication after solid organ transplantation, CMV serology has been considered insufficient and thus CMV immunity is increasingly assessed by cellular in vitro methods. We compared two commercially available IFN-γ ELISpot assays (T-Track CMV and T-SPOT.CMV) and an IFN-γ ELISA (QuantiFERON-CMV). Currently, there is no study comparing these three assays. The assays were performed in 56 liver transplant recipients at the end of antiviral prophylaxis and one month thereafter. In CMV high- or intermediate-risk patients the two ELISpot assays showed significant correlation (p < 0.0001, r > 0.6) but the correlation of the ELISpot assays with QuantiFERON-CMV was weaker. Results of both ELISpot assays were similarly predictive of protection from CMV-DNAemia ≥500 copies/mL [CMV pp65 T-SPOT.CMV at the end of prophylaxis: area under curve (AUC) = 0.744, cut-off 142 spot forming units (SFU), sensitivity set to 100%, specificity 46%; CMV IE-1 T-Track CMV at month 1: AUC = 0.762, cut-off 3.5 SFU, sensitivity set to 100%, specificity 59%]. The QuantiFERON-CMV assay was inferior, reaching a specificity of 23% when setting the sensitivity to 100%. In conclusion, both CMV-specific ELISpot assays appear suitable to assess protection from CMV infection/reactivation in liver transplant recipients.

Hepatitis B virus infection results in the appearance of anti-HBc antibodies that normally persist lifelong. We analyzed the course of anti-HBc antibodies overtime, focusing on patients with a permanent loss or fluctuating anti-HBc antibodies. From 120,531 patients tested for anti-HBc antibodies (Architect, Abbott) from January 2006 to December 2020, ≥4 serial values were available in 8098 and permanent or intermittent anti-HBc loss was observed in 139 patients. It was relatively frequent in baseline anti-HBc positive, immunocompromised patients with available serial measurements of anti-HBc overtime (13% of hematologic/oncologic patients, 10% of solid organ transplant recipients, and 6% of HIV patients compared to 3% in patients with other diseases). In the same period, 12,607 samples were tested for HBsAg, anti-HBc antibodies, and HBV DNA—in nine cases we detected HBV DNA with undetectable anti-HBc and HBsAg. In four out of nine cases contamination of the PCR during processing was the likeliest cause, in another four, no further data were available, while in one the HBV DNA was later followed by a temporary anti-HBc seroconversion. In conclusion, permanent or intermittent anti-HBc loss is more common in immunocompromised hosts than in patients with other underlying diseases. Furthermore, anti-HBc and HBsAg assays can be safely used to exclude an active HBV infection, even in immunocompromised hosts.

Background: Patients with primary brain tumors face profound disease- and treatment-related immunosuppression, placing them at high risk for severe infections. Their capacity to mount protective immune responses to vaccination, particularly to repeated antigen exposures such as COVID-19 boosters, remains critically under-defined, leading to uncertainty in clinical practice. Methods: In this prospective cohort study, we analyzed humoral responses to seasonal COVID-19 (mRNA-based) and influenza vaccination in 17 patients with primary brain tumors (recruited from an initial cohort of 37) who received a booster shot, and 19 healthy controls. Serum samples were collected before (T1) and 30 ± 2 days after (T2) vaccination to quantify SARS-CoV-2 anti-Spike (S) IgG and anti-Influenza IgG titers. Results: Despite ongoing chemotherapy in 47% of patients, baseline anti-S antibody titers were comparable between groups. Following the booster, median anti-S titers increased significantly and to a similar magnitude in both patients (from 5030 to 18,500 BAU/mL; IQR: 13,885–24,420) and controls (from 4429 to 20,200 BAU/mL; IQR: 11,075–26,680; p = 0.6137, Mann–Whitney U test). Only two heavily pre-treated patients showed no booster response. All participants showed sero-positivity to Anti-Influenza IgG at baseline. For the primary brain tumor cohort, a significant increase for anti-Influenza IgG at T2 was observed (p = 0.0002). Mean antibody titers did not differ between both cohorts. Conclusions: Our findings provide evidence that patients with primary brain tumors can mount robust recall immunity to mRNA vaccines, addressing clinical uncertainty about booster efficacy in this population. These data provide a strong rationale for prioritizing booster vaccinations in this vulnerable population and argue for the inclusion of these patients in future pivotal vaccine trials.