Zoonotic introduction of novel coronaviruses may encounter preexisting immunity in humans. Using diverse assays for antibodies recognizing SARS-CoV-2 proteins, we detect preexisting humoral immunity. SARS-CoV-2 spike glycoprotein (S)-reactive antibodies were detectable by a flow cytometry-based method in SARS-CoV-2-uninfected individuals and were particularly prevalent in children and adolescents. They were predominantly of the IgG class and targeted the S2 subunit. By contrast, SARS-CoV-2 infection induced higher titers of SARS-CoV-2 S-reactive IgG antibodies, targeting both the S1 and S2 subunits, and concomitant IgM and IgA antibodies, lasting throughout the observation period. Notably, SARS-CoV-2-uninfected donor sera exhibited specific neutralizing activity against SARS-CoV-2 and SARS-CoV-2 S pseudotypes. Distinguishing preexisting and de novo immunity will be critical for our understanding of susceptibility to and the natural course of SARS-CoV-2 infection.

No abstract

18-60 months), the actuarial overall survival (OS) rates at 3 years were 34% for HG-NHL, 60% for MCL, and 73% for LG-NHL (P < .001). The 100-day and 3-year transplant-related mortality (TRM) rates for patients with LG-NHL were 2% and 11%, respectively, and were better (P ‫؍‬ .01) than they were for patients with HG-NHL (27% and 38%, respectively). The actuarial current progression-free survival (PFS) rate at 3 years, including the rate for patients who achieved remission after donor lymphocyte infusion (DLI) for progression, was 65% for LG-NHL, 50% for MCL, and 34% for HG-NHL (P ‫؍‬ .002).

Several related human coronaviruses (HCoVs) are endemic in the human population, causing mild respiratory infections 1 . Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiologic agent of Coronavirus disease 2019 , is a recent zoonotic infection that has quickly reached pandemic spread 2,3 . Zoonotic introduction of novel coronaviruses is thought to occur in the absence of pre-existing immunity in the target human population. Using diverse assays for detection of antibodies reactive with the SARS-CoV-2 Spike (S) glycoprotein, we demonstrate the presence of pre-existing immunity in uninfected and unexposed humans to the new coronavirus. SARS-CoV-2 S-reactive antibodies, exclusively of the IgG class, were readily detectable by a sensitive flow cytometry-based method in SARS-CoV-2-uninfected individuals with recent HCoV infection and targeted the S2 subunit. In contrast, SARS-CoV-2 infection induced higher titres of SARS-CoV-2 Sreactive IgG antibodies, as well as concomitant IgM and IgA antibodies throughout the observation period of 6 weeks since symptoms onset. HCoV patient sera also variably reacted with SARS-CoV-2 S and nucleocapsid (N), but not with the S1 subunit or the receptor binding domain (RBD) of S on standard enzyme immunoassays. Notably, HCoV patient sera exhibited specific neutralising activity against SARS-CoV-2 S pseudotypes, according to levels of SARS-CoV-2 S-binding IgG and with efficiencies comparable to those of COVID-19 patient sera. Distinguishing pre-existing and de novo antibody responses to SARS-CoV-2 will be critical for serology, seroprevalence and vaccine studies, as well as for our understanding of susceptibility to and natural course of SARS-CoV-2 infection. ResultsImmune cross-reactivity among seasonally spreading human coronaviruses (HCoVs) has long been hypothesised to provide cross-protection, albeit transient, against infection with distinct HCoV types 1,4,5 . To determine the degree of cross-reactivity between HCoVs and the recently introduced zoonotic coronavirus SARS-CoV-2, we developed a sensitive flow cytometry-based assay for detection of SARS-CoV-2-binding antibodies. Sera from COVID-19 patients at University College London Hospitals (UCLH) (Table S1), contained high levels of IgG, IgM and IgA antibodies recognising the wild-type Spike (S) glycoprotein of SARS-CoV-2 expressed on the surface of HEK293T cells, whereas control sera did not (Fig. 1a). Notably, sera from a proportion patients with confirmed HCoV infection collected before or during the early spread of SARS-CoV-2 in the UK (Table S1), also contained SARS-CoV-2 S-specific antibodies (Fig. 1a). However, the latter sera contained only lower levels of S-specific IgG and no IgM or IgA antibodies, which clearly distinguished them from COVID-19 patient sera (Fig. 1a). The SARS-CoV-2 S protein is proteolytically processed into the S1 and S2 subunits that mediate target cell attachment and entry, respectively 6,7 . S2 exhibits a higher degree of homology among coronaviruses than S1 (Extended data Fig. 1...

Allo-SCT in relapsed DLBCL after ASCT is a promising therapeutic modality. Patients with a long remission after ASCT and with sensitive disease at allo-SCT are the best candidates for this approach.

These data indicate that application of cytomegalovirus-specific T cells generated by direct selection using γ-capture is both feasible and effective in a clinical environment. These simple in vitro methodologies should allow more widespread application of virus-specific T cell immunotherapies.

Data on the application of donor lymphocyte infusions (DLIs) following reduced-intensity transplantation (RIT) remain limited. Persistence of host antigen-presenting cells might increase the efficacy or toxicity of cellular immunotherapies. We report the results of dose-escalating DLIs in 46 patients undergoing RIT, who received a total of 109 infusions to treat mixed chimerism or residual or progressive disease. Diagnoses were myeloma (n = 19), Hodgkin lymphoma (n = 13), non-Hodgkin lymphoma (n = 10), and other (n = 4). Thirty-two had an HLA-matched family donor and 14 an unrelated donor. Grades II to IV graft-versus-host disease (GVHD) occurred in 5 sibling and 7 unrelated donor recipients. GVHD was more common (P =.002), occurred at lower T-cell doses, and was more severe in the unrelated donor cohort. Conversion from mixed to multilineage full donor chimerism occurred in 30 of 35 evaluable patients. Presence of mixed chimerism in the granulocyte lineage at the time of DLI did not predict for chimerism response or GVHD. Disease responses occurred in 63% of patients with myeloma and 70% of those with Hodgkin lymphoma and were not predicted by changes in chimerism. These data support the presence of clinically relevant graft-versus-Hodgkin activity and indicate that DLI may be associated with a significantly increased toxicity in unrelated compared to sibling donor transplant recipients receiving identical treatment protocols.

Persistence of alemtuzumab at lympholytic concentrations after reduced-intensity conditioning allogeneic stem cell transplantations (RITs) could impair immune reconstitution and reduce donor T-cell-mediated graft-versus-leukemia/ lymphoma (GVL) effects, derived from the graft or subsequent adoptive immunotherapy. We have studied the pharmacokinetics of alemtuzumab in 2 different groups: RIT (100 mg alemtuzumab in vivo over 5 days) and myeloablative allografts (20 mg alemtuzumab added in vitro to the stem cells prior to return). Alemtuzumab concentrations in RIT patients were in excess of that required to kill infused donor CD52 ؉ cells at the time of transplantation and remained at potentially lympholytic levels (> 0.1 g/mL) for approximately 56 days after transplantation, 26 days longer than for the myeloablative group. Total lymphocyte counts were significantly lower in the RIT group persisting beyond 6 months after transplantation (P ‫؍‬ .005), and median absolute CD4 counts higher than 200 ؋ 10 6 /L were delayed until 9 months after transplantation.