SummaryDuring periods of immunosuppression, such as postallogeneic stem cell transplantation (SCT), patients are at significant risk for severe viral infections. Human adenovirus (HAdV) infection is a serious complication post‐SCT, especially in children. Virus‐specific T cells are essential for the clearance of HAdV, as antiviral chemotherapy has revealed limited success. We present feasibility data for a new treatment option using virus‐specific donor T cells for adoptive transfer of immunity to patients with HAdV‐infection/reactivation. Virus‐specific donor T cells were isolated and infused into nine children with systemic HAdV infection after SCT. Isolation was based on γ‐interferon (IFN‐γ) secretion after short in vitro stimulation with viral antigen, resulting in a combination of CD4+ and CD8+ T cells. 1·2–50 × 103/kg T cells were infused for adoptive transfer. Isolated cells showed high specificity and markedly reduced alloreactivity in vitro. Adoptive transfer of HAdV‐specific immunity was successful in five of six evaluable patients, documented by a dose‐independent and sustained in vivo expansion of HAdV‐specific T cells, associated with a durable clearance/decrease of viral copies. T‐cell infusion was well tolerated in all nine patients, except one case with graft‐versus‐host disease II of the skin. In conclusion, induction of a specific T‐cell response through adoptive transfer was feasible and effective. When performed early in the course of infection, adoptive T‐cell transfer may protect from HAdV‐related complications.

Highly sensitive and specific platforms for the detection of anti-SARS-CoV-2 antibodies are becoming increasingly important for (1) evaluating potential SARS-CoV-2 convalescent plasma donors, (2) studying the spread of SARS-CoV-2 infections and (3) identifying individuals with seroconversion. This study provides a comparative validation of four anti-SARS-CoV-2 platforms. Unique feature of this study is the use of a representative cohort of COVID-19-convalescent patients with mild-to-moderate disease course. All platforms showed significant correlations with a SARS-CoV-2 plaque-reduction-neutralization test, with highest sensitivities for the Euroimmun and the Roche platforms, suggesting their preferential use for screening of persons at increased risk of SARS-CoV-2 infections.

To identify the most efficient methods of immunological protection against SARS-CoV-2, including the currently most widespread variants of concern (VOCs)—B.1.1.7, B.1.351 and P.1—a simultaneous side-by-side-comparison of available vaccination regimes is required. In this observational cohort study, we compared immunological responses in 144 individuals vaccinated with the mRNA vaccines BNT162b2 or mRNA-1273 and the vector vaccine ChAdOx1-nCoV-19, either alone, in combination, or in the context of COVID-19-convalescence. Unvaccinated COVID-19-convalescent subjects served as a reference. We found that cellular and serological immune responses, including neutralizing capacity against VOCs, were significantly stronger with mRNA vaccines as compared with COVID-19-convalescent individuals or vaccinated individuals receiving the vector vaccine ChAdOx1-nCoV-19. Booster immunizations with mRNA vaccines triggered strong and broadly neutralizing antibody and IFN-γ responses in 100% of vaccinated individuals investigated. This effect was particularly strong in COVID-19-convalescent and ChAdOx1-nCoV-19-primed individuals, who were characterized by comparably moderate cellular and neutralizing antibody responses before mRNA vaccine booster. Heterologous vaccination regimes and convalescent booster regimes using mRNA vaccines may allow enhanced protection against SARS-CoV-2, including current VOCs. Furthermore, such regimes may facilitate rapid (re-)qualification of convalescent plasma donors with high titers of broadly neutralizing antibodies.

Infection of vascular endothelial cells (ECs) is assumed to contribute to dissemination of human cytomegalovirus (HCMV). Investigation of virus-host interactions in ECs such as human umbilical vein endothelial cells (HUVECs) is limited due to the low maximal passage numbers of these primary cells. We tested a conditionally immortalized EC line (HEC-LTT) and a permanent cell line (EA.hy926) for their susceptibility to HCMV infection. Both cell lines resembled HUVECs in that they allowed for entry and immediate early protein expression of highly endotheliotropic HCMV strains but not of poorly endotheliotropic strains, rendering them suitable for analysis of the viral entry mechanism in ECs. The late phase of viral replication and release, however, was supported by growth-controlled HEC-LTT cells but not by EA.hy926 cells. HEC-LTT cells support both the early and late phase of viral replication and release infectious progeny virus at titers comparable to primary HUVECs; thus, the HEC-LTT cell line is a cell culture model representing the full viral replicative cycle of HCMV in ECs. The implementation of permanent HEC-LTT and EA.hy926 cell lines in HCMV research will facilitate long-term approaches that are not feasible in primary HUVECs.

Coronavirus disease 2019 (COVID-19) is a highly contagious disease caused by a newly identified coronavirus called the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) which was initially emerged in Wuhan, China in late December 2019 and then rapidly extended to other countries worldwide. COVID-19 is now known as a pandemic threat to global public health. It possesses a wide spectrum of clinical manifestations, ranging from asymptomatic infection to mild, moderate, and ultimately severe pneumonia accompanied by multi-organ system dysfunction that can cause the death of the afflicted patients. The host immune system plays a critical role in defending against potentially pathogenic microorganisms such as coronaviruses, and it eliminates and eradicates these invading agents by triggering effective immune responses. However, there exists evidence indicating that in critically ill cases of the COVID-19, dysregulated immune responses and hyper-inflammation lead to acute respiratory distress syndrome (ARDS) and multi-organ failure. Achieving a profound understanding of the pathological immune responses involved in the pathogenesis of COVID-19 will boost our comprehending of disease pathogenesis and its progression toward severe form, contributing to the identification and rational design of effective therapies. In this review, we have tried to summarize the current knowledge regarding the role of immune responses against SARS-CoV-2 and also give a glimpse of the immune evasion strategies of this virus.

The current SARS-CoV-2 pandemic has triggered the development of various SARS-CoV-2 neutralization tests. A wild-type virus (using African green monkey VeroE6 cells), a pseudovirus (using human Caco-2 cells), and a surrogate neutralization test platform were applied to characterize the SARS-CoV-2 neutralization potential of a cohort of 111 convalescent plasma donors over a period of seven months after diagnosis. This allowed an in-depth validation and assay performance analysis of these platforms. More importantly, we found that SARS-CoV-2 neutralization titers were stable or even increased within the observation period, which contradicts earlier studies reporting a rapid waning of Ab titers after three to four months. Moreover, we observed a positive correlation of neutralization titers with increasing age, number of symptoms reported, and the presence of the Rhesus Ag RhD. Validation of the platforms revealed that highest assay performances were obtained with the wild-type virus and the surrogate neutralization platforms. However, our data also suggested that selection of cutoff titers had a strong impact on the evaluation of neutralization potency. When taking strong neutralization potency, as demonstrated by the wild-type virus platform as the gold standard, up to 55% of plasma products had low neutralization titers. However, a significant portion of these products were overrated in their potency when using the surrogate assay with the recommended cutoff titer. In summary, our study demonstrates that SARS-CoV-2 neutralization titers are stable for at least seven months after diagnosis and offers a testing strategy for rapid selection of high-titer convalescent plasma products in a biosafety level 1 environment.

Elderly residents of long-term care facilities (LTCFs) have long been underrepresented in studies on vaccine efficacy, particularly in light of currently emerging variants of concern (VOCs). In this prospective observational cohort study, we analyzed serological immune responses in 190 individuals before, 3 weeks after 1st and 3 weeks after 2nd vaccination with BNT162b2. Unvaccinated COVID-19-convalescent subjects served as reference. End points comprised serum anti-spike IgG and IgA titers as well as neutralization capacities against unmutated and mutated SARS-CoV-2 receptor binding domains including B.1.1.7, B.1.351 and P.1. We found that antibody titers and neutralization capacities up to 3 weeks after 2nd vaccination with BNT162b2 were significantly higher in COVID-19-convalescent as compared to COVID-19-naive vaccinees. Moreover, pre-vaccination anti-NCP IgG titers, but not age or gender, had a high impact on the strength and kinetics of post-vaccination neutralization capacity development. Most importantly, BNT162b2-induced neutralization capacity was cross-reactive with VOCs. In contrast to unvaccinated convalescents, vaccinated convalescent individuals of all ages acquired strong neutralizing capacities against current VOCs. The present study suggests that COVID-19-convalescent individuals with a broad age range between 18 and 98 years benefit from BNT162b2 vaccination by developing strong and broad neutralizing immune responses against SARS-CoV-2 including current VOCs.

BACKGROUND. Results of many randomized trials on COVID-19 convalescent plasma (CCP) have been reported but information on long-term outcome after CCP treatment is limited. The objectives of this extended observation of the randomized CAPSID Trial are to assess long-term outcome and disease burden in patients initially treated with or without CCP. METHODS. Of 105 randomized patients, 50 participated in the extended observation. Quality of life (QoL) was assessed by questionnaires and a structured interview.CCP-donors (n=113) with asymptomatic to moderate COVID-19 were included as a reference group.RESULTS. The median follow-up of patients was 396 days, the estimated 1-year survival was 78.7% in the CCP and 60.2% in the control group (p=0.08). The subgroup treated with a higher cumulative amount of neutralizing antibodies showed a better 1-year survival compared to the control group (91.5% versus 60.2%; p=0.01). Medical events and QoL assessments showed a consistent trend for better results in the CCP group without reaching statistical significance. There was no difference in the increase of neutralizing antibodies after vaccination between CCP and the control group.CONCLUSION. The trial demonstrated a trend towards better outcome in the CCP group without reaching statistical significance. A pre-defined subgroup analysis showed a significant better outcome (long-term survival; time to discharge from ICU and time to hospital discharge) among those who received a higher amount of neutralizing antibodies compared to the control group. A substantial long-term disease burden remains after severe COVID-19.