Development of warm autoimmune hemolytic anemia after initiation of Ruxolitinib in a patient with STAT1 gain-of-function mutation

Introduction: STAT1 gain-of-function (GOF) disease is associated with chronic mucocutaneous candidiasis (CMC) and a broad spectrum of infectious, inflammatory, and vascular manifestations. The Janus Kinase inhibitor ruxolitinib has been used successfully for CMC and autoimmune phenomena. We describe a case of warm autoimmune hemolytic anemia (WAIHA) in a patient with STAT1 GOF disease after initiating ruxolitinib. Case report: A 36-year-old man with STAT1 c.850G>A (p.Glu284Lys) mutation presented with CMC as well as recurrent viral and bacterial infections, lymphadenopathy, enteritis, nodular regenerative hyperplasia (NRH) and splenomegaly. Immune workup confirmed a combined immunodeficiency with hypogammaglobulinemia and T-cell lymphopenia. Ruxolitinib was initiated at 5 mg twice daily (due to pre-existing thrombocytopenia) with up titration over 3 months to 20 mg twice daily. He improved with weight gain, increased energy, resolution of chronic anemia, and improved lymphadenopathy and splenomegaly on imaging. Serum CXCL9 only minimally decreased from 4660 pg/ml to 3990 pg/ml. Soon after reaching ruxolitinib 20 mg twice daily, he developed JC viremia, prompting dose reduction to 15 mg BID. Within two weeks, he developed a non-COVID upper respiratory tract infection followed by fatigue, shortness of breath with ambulation, and dark urine. Emergency evaluation revealed warm antibody positive hemolytic anemia with a hemoglobin of 5 g/dL, and worsened thrombocytopenia. He was treated with blood transfusions, pulse steroids, and high-dose IVIG with stabilization but continued hemolysis. Due to the JC viremia, there was concern to give rituximab with increased PML risk. Bone marrow showed trilineage hematopoiesis, a mild increase in megakaryocytes and RBC precursors, and a loss of B-cell progenitors with retention of mature B cells. His B and T lymphocyte numbers had increased since prior to ruxolitinib, with a predominance of Tfh1-cells (58.7% of total Tfh-cells). He was started on sirolimus with a slow taper of prednisone with continued stable hemoglobin and platelets, and resolution of hemolysis after 3 months. Conclusion(s): To our knowledge, this is the first case of a STAT1 GOF patient developing WAIHA while receiving ruxolitinib therapy. Treatment choices were complicated by the risks of PML. Sirolimus combined with ruxolitinib allowed wean of corticosteroid and subsequent resolution of hemolysis.Copyright © 2023 Elsevier Inc.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19.

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2-4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells - basophiles and eosinophils - were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory" Tfh1 cell and increased "pro-inflammatory" Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naive" and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24- plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.Copyright © 2022 Saint Petersburg Pasteur Institute. All rights reserved.

Boosting compromised SARS-CoV-2-specific T cell immunity in liver transplant recipients by mRNA vaccination

Background and aims Liver transplant recipients (LTR) are threatened by a lower immunogenicity of SARS-CoV-2 mRNA vaccines. However, the interplay between the different branches of the adaptive immune system especially after a third (and fourth) vaccine dose is still poorly understood. Methods Our study longitudinally compares the humoral as well as the cellular response between age-matched LTR (n = 24) and healthy controls (HC, n = 19) after three to four vaccine doses. Therefore, we assessed antibody titers, analyzed the spike-specific T cell epitope repertoire, performed an in-depth characterization of spike-specific CD8 + T cells on a single-epitope level and examined the distribution of different virus-specific CD4 + T cell subpopulations. Results Compared to HC, the development of high antibody titers depended on a third vaccine dose in most LTR. In contrast, spike-specific CD8 + T cells reached a stable level already after the second vaccine dose, albeit with a lower frequency and a narrower epitope repertoire compared to HC. Concerning the CD4 + T cells, the total number of detectable responses as well as the repertoire of targeted epitopes within the spike protein did not signifcantly difer in both cohorts. However, we observed a link between the overall attenuated vaccine response and a reduced frequency of spike-reactive follicular T helper cells (TFH) in LTR. Conclusion Three doses of a COVID-19 mRNA vaccine induce an overall robust humoral and cellular memory response in most LTR. Evaluations of additional booster doses may thus consider the individual vaccine responsiveness as well as the evolution of novel variants of concern.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2–4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells — basophiles and eosinophils — were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory” Tfh1 cell and increased "pro-inflammatory” Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naïve” and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24– plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.

First person - Sarantis Korniotis

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Sarantis Korniotis is first author on 'GM-CSF-activated human dendritic cells promote type 1 T follicular helper cell polarization in a CD40-dependent manner', published in JCS. Sarantis conducted the research described in this article while a postdoctoral researcher in Professor Vassili Soumelis's lab at Saint-Louis Hospital, Universite de Paris, France. He is now a Senior Scientific Associate in Immunology at Intelligencia AI, Athens, Greece, investigating new signals and factors that make cells acquire regulatory or immune-suppressive properties. Copyright © 2022 Company of Biologists Ltd. All rights reserved.

Model Immunization with Coronavirus-2 Vaccines Induce Potent Antibody Responses but Does Not Aggravate Lymphocyte Abnormalities in Primary Sjogren's Syndrome Patients

Objectives. The peripheral lymphocyte compartment of patients with primary Sjogren's syndrome (pSS) differs strongly from healthy individuals. Whether this altered lymphocyte composition also abnormally changes during immune reactions, especially in the context of novel mRNA-vaccines, is unknown. Methods. Peripheral blood samples from 26 pSS patients were compared to 6 healthy controls before Coronavirus-2 (CoV-2) vaccination (BNT162b2, ChAdOx1, mRNA-1273) and 7 days after secondary vaccination. Spike. 1 (S1)-receptor binding domain (RBD)-neutralizing IgG antibodies were measured in serum samples. Within peripheral blood mononuclear cells (PBMC), lymphocytes were characterized using spectral flow cytometry and B and T cell subpopulations were phenotypically analyzed. Results. Immunization induced CoV-2 specific serum antibodies in all pSS and healthy participants. When analyzing pSS and healthy individuals together, frequencies of circulating IgG+ RBD-binding antibody-secreting cells (ASC) and anti-CoV-2 serum titers correlated (r=0.42, p=0.022). Previously described alterations of peripheral B cells in pSS patients (like reduced memory B cells, increased naive and transitional B cells and higher maturity of ASCs) remained stable during vaccination. Also the subset distribution of CD4+ and CD8+ T cells mainly stayed unchanged. However, CD4+CXCR5-PD-1+ T cells phenotypically mimicking peripheral helper TPH cells increased in pSS patients comparing pre- and post-vaccination (p=0.020), while circulating CD4+CXCR5+PD-1+ follicular helper TFH cells declined (p=0.024). Conclusions. An immune reaction induced by vaccination with the novel mRNA technology yields adequate antibody production and vaccine specific lymphocytes in pSS patients and controls. However, no major changes within the typical composition of lymphocyte subpopulations of pSS patients were observed despite small changes in TPH and TFH subsets.

Characterization of the humoral response to Orf virusvectored immunization

Recombinant Orf virus (rORFV) based vectors are under clinical development for COVID-19 vaccination. Little is known, however, about the cellular correlates of antibody responses to this poxviral vector platform. To monitor antigen-specific B cell responses to vaccination, we adoptively transferred to mice indicator populations of monoclonal B cells recognizing the glycoproteins (GPs) of either vesicular stomatitis virus or lymphocytic choriomeningitis virus and epitope variants thereof. Immunizations of mice with rORFV expressing the respective GPs stimulated the transferred B cells to engage in a protracted germinal center (GC) response, which was maintained longer-term when the delivered antigen was of lower affinity. GPspecific CD8 and CD4 T cells responses were also induced, and the latter included T follicular helper cells (Tfh). These T cell responses contracted over time but re-expanded upon homologous rORFV booster vaccination, alongside with an augmentation in antigen-specific memory B cells. Pre-existing rORFV-specific anti-vector immunity suppressed CD8 T cell responses to ORFV-vectored cargo whereas CD4 T cell and B cell responses were unaffected. Importantly, rORFV-based vaccination conferred long-term antibodymediated protection against VSV challenge. This study demonstrates the versatility of rORFV-vectored vaccination including its capacity to induce substantial GC B cell as well as Tfh responses. Limited interference by anti-vector immunity should facilitate the challenging task of maintaining protective antibody immunity by prime - boost vaccination.

RHEUMATOID ARTHRITIS DISEASE ACTIVITY ASSESSED by PATIENT-REPORTED OUTCOMES and FLOW CYTOMETRY before and after AN ADDITIONAL DOSE of COVID-19 VACCINE

Background: The Centers for Disease Control and Prevention recommends an additional dose (AddDose) of COVID-19 vaccine for moderately/severely immunosuppressed individuals following an initial vaccine series. The American College of Rheumatology suggests that patients interrupt use (hold) certain DMARDs around the time of COVID-19 vaccination to improve immunogenicity. Whether holding DMARDs around an AddDose of COVID-19 vaccine affects RA disease activity or affects frequencies of lymphocyte populations that may be associated with RA disease activity remains unknown. Objectives: To test whether RA disease activity and frequencies of lymphocyte populations change pre-vs. post-AddDose of COVID-19 vaccine, overall and stratifed by holding vs. continuation of DMARDs around the AddDose. Methods: Prospective observational cohort study of patients with RA who had completed an initial COVID-19 vaccine series (2 doses of mRNA vaccine or 1 dose of adenovirus vector vaccine). Subjects enrolled July-November 2021, prior to receiving an AddDose. Subjects held or continued DMARDs around the AddDose based on discussion with their rheumatologist and/or personal decision-making. RA disease activity was assessed weekly using the validated patient-reported RA Disease Activity Index-5 (RADAI-5) from enrollment through 4 weeks post-AddDose. We compared mean RADAI-5 pre-vs. post-AddDose using generalized estimating equations to account for correlated data among individual subjects. We aimed to enroll 60 subjects to achieve 91% power to detect a 15% non-inferiority margin in mean RADAI-5 post-vs. pre-AddDose. A subset of subjects with seropositive RA provided blood for fow cytometry at enrollment and week 4 post-AddDose. Frequencies of lymphocyte populations (T peripheral helper [Tph] cells, T follicular helper [Tfh] cells, age-associated B cells [ABC], and plasmablasts) were compared pre-vs. post-AddDose using Wilcoxon paired tests with Bonferroni correction. Results: Among 71 subjects, mean age was 62 (SD 12) years, 85% were female, and 87% had seropositive RA. Methotrexate (42%) and TNF inhibitors (38%) were the most common DMARDs;21% were taking prednisone. One subject reported COVID-19 infection prior to the AddDose. The mean RADAI-5 was 3.20 (SD 0.23) pre-AddDose compared to 3.25 (SD 0.23) after (difference of 1.6%, p=0.51). Figure 1 displays mean RADAI-5 in 35 (49%) subjects that held at least 1 DMARD and 36 (51%) subjects that continued all DMARDs around the AddDose. Mean change in RADAI-5 between pre-vs. post-AddDose did not signifcantly differ based on whether subjects held vs. continued DMARDs (p for interaction = 0.16). Frequencies of Tph, Tfh, ABC, and plasmablast populations did not signifcantly differ between the pre-and post-AddDose timepoints in subjects that held at least 1 DMARD (n=16) or subjects that continued all DMARD (n=11) (Figure 1). Conclusion: RA disease activity, measured weekly with a validated patient-reported outcome, is stable around the time of an AddDose of COVID-19 vaccine. Lymphocyte subsets of interest in RA were also similar before and after the AddDose, supporting the observation of stable patient-reported RA disease activity. Holding DMARDs was not associated with greater RA disease activity following the AddDose.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2–4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells — basophiles and eosinophils — were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased “regulatory” Tfh1 cell and increased “pro-inflammatory” Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of “naïve” and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24– plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.

HUMORAL AND T CELL RESPONSES TO COVID-19 VACCINATION IN INFLAMMATORY BOWEL DISEASE

BACKGROUND: The characteristics of SARS-CoV-2 vaccine-induced immunity in inflammatory bowel disease (IBD) patients on immune modifying agents has not been clearly defined due to their exclusion in vaccine trials. Emerging results suggest infliximab impairs antibody response compared to vedolizumab. However there has not been direct comparison to controls. We evaluated this with both humoral and T cell response in IBD patients. METHODS: Antibody and T cell response were analysed in IBD patients who received BNT162b2 (Pfizer–BioNTech) or ChAdOx1 nCoV-19 (Oxford–AstraZeneca) vaccination from a single Australian centre. The control group were healthcare workers (HCW) without IBD. Blood samples were taken at 4 time points: at baseline V0 (before vaccination);V1 (7- 14 days after vaccine 1);V2 (7-14 days after vaccine 2);V3 (21-42 days after vaccine 2). Antibodies to the S1/2 IgG subunit and receptor-binding protein (RBD) were measured and reported here. RESULTS: 88 (28 ulcerative colitis, 50 Crohn's disease) IBD patients were included and compared to 53 healthy controls (Table 1). IBD patients medications included 6 5ASA (6.8%), 6 immunomodulator monotherapy (6.8%), 14 anti-TNF monotherapy (15.9%), 32 anti-TNF combination therapy with immunomodulator (36%), 16 IL12/23 (18%) and 13 vedolizumab (14%). Pre-vaccine baseline sera showed absence of anti-RBD antibodies in all participants. 84 patients (87%) received BNT162b2 and 4 (4.5%) received ChAdOx1 nCoV-19 vaccines. Geometric mean [SD] anti-S1/2 antibody concentrations at 4 weeks after second vaccination (V3) were significantly lower in IBD TNF treated patients (162.6[1.7]) compared to IBD non TNF treated patients (325.2[1.3]), and healthy controls (325.2[1.3]), p<0.0001 (Figure 1). There was no difference between non-TNF treated patients including those on vedolizumab or IL12/23 compared to controls. Similarly there was a significant difference between anti-RBD IgG titres between TNF and non-TNF IBD patients at V3 but not when compared to controls. There was no difference in RBD IgG and anti-S1/2 antibodies between anti-TNF monotherapy and combination therapy. All healthy controls and most IBD patients seroconverted at V3. 2 patients that failed to seroconvert were on steroid. CONCLUSION: TNF agents influence SARS-CoV-2 vaccine-induced antibody response in IBD patients, with lower anti-S1/2 IgG concentrations compared to non-TNF IBD patients and healthy controls. However, there was no difference in RBD IgG concentrations. It is unclear whether these subtle differences in antibody response in IBD patients on TNF agents is biologically meaningful, as most seroconverted after second dose vaccination. They may translate to differences in antibody longevity, but this is yet to be demonstrated. Neutralising antibody and T cell (CD4+/CD8+/follicular T cell) data from this study to come. (Table Presented) (Figure Presented)

PUSHING the ENVELOPE: MRNA VACCINES for COVID-19, HIV, and OTHER PATHOGENS

Vaccines prevent 4-5 million deaths a year making them the principal tool of medical intervention worldwide. Nucleoside-modified mRNA was developed over 15 years ago and has become the darling of the COVID-19 pandemic with the first 2 FDA approved vaccines based on it. These vaccines show greater than 90% efficacy and outstanding safety in clinical use. The mechanism for the outstanding immune response induction are the prolonged production of antigen leading to continuous loading of germinal centers and the adjuvant effect of the LNPs, which selectively stimulate T follicular helper cells that drive germinal center responses. Vaccine against many pathogens, including HIV, HCV, HSV2, CMV, universal influenza, coronavirus variants, pancoronavirus, nipah, norovirus, malaria, TB, and many others are currently in development. Nucleoside-modified mRNA is also being developed for therapeutic protein delivery. Finally, nucleoside-modified mRNA-LNPs are being developed and used for gene therapy. Cas9 knockout to treat transthyretin amyloidosis has shown success in phase 1 trials. We have developed the ability to target specific cells and organs, including lung, brain, heart, CD4+ cells, all T cells, and bone marrow stem cells, with LNPs allowing specific delivery of gene editing and insertion systems to treat diseases such as sickle cell anemia. Nucleoside-modified mRNA will have an enormous potential in the development of new medical therapies.

TEMPORAL ASSOCIATIONS of B and T CELL IMMUNITY in A 16-WEEK INTERVAL BNT162b2 REGIMEN

Background: Spacing of the BNT162b2 mRNA doses beyond the standard 3-week interval raised concerns about vaccine efficacy. We longitudinally analyzed B cell, T cell and humoral responses to two BNT162b2 mRNA doses administered 16 weeks apart in 43 SARS-CoV-2 naïve and previously-infected (PI) donors. We examined blood samples at five time points from baseline to 4 months post second dose. Methods: We used high-parameter flow cytometry to study: i) receptor binding domain (RBD)-specific B cells;ii) Spike (S)-specific CD4 and CD8 T cells by activation-induced marker (AIM) assay;iii) S-specific CD4 and CD8 T cells by intracellular staining (ICS) assay. We measured humoral responses by ELISA, neutralization and ADCC assays. We did supervised and unsupervised (FlowSOM) analyses of B and T cell subsets, and temporal association analyses. Results: We observed partial attrition of B and T cell responses between doses at a memory time point 12 weeks post first dose. RBD-specific B cell kinetics differed between cohorts: the first dose led to their robust increase in PI but small magnitude in naïve. The second dose had little effect in PI but briskly expanded RBD-specific B cells in naïve, leading to convergence between cohorts. Robust T cell responses, with a dominance of CD4 over CD8 responses, were universally induced and did not significantly differ in magnitude after either dose, although there was a trend for a gain in CD8 responses after the second dose in naïve. Unsupervised and supervised analyses of S-specific CD4 T cells showed that the first dose was sufficient to generate highly diverse CD4 subsets, including robust populations of follicular T helper cells. The second dose did not elicit new subsets but lead to convergent phenotypic and functional profiles between PI and naïve with qualitative shifts. Integrated analyses of antigen-specific responses showed immune component-specific associations over-time, with early CD4 responses post-first dose (but not at late time points) strongly correlating with B cell responses after the second dose. In contrast, CD8 responses post second dose correlated with CD4 responses at the same time point. Conclusion: The 16-week interval schedule is associated with robust, multi-faceted recall cellular responses after the second dose, consistent with highly functional immune memory. The early induction of robust CD4 responses and their associations with longer-term B cell and humoral immunity support their central role in the efficacy of this vaccine regimen.

Impact of immunotherapy on COVID-19immunity: Insights from checkpoint blockade in cancer

Over the last few years, we have gained insights into how immunotherapy, including checkpoint blockade, modulates key CD4 and CD8 T cell subsets in anti-tumor immunity. This information can now give us insights intohow immunotherapy can impact immunity in the setting of COVID-19. Indeed, we recently demonstrated that cancerpatients with T cell depletion have high COVID-19 mortality despite adequate B cell and antibody production, highlighting the importance of cellular immunity. Conversely, in the setting of B cell depletion by anti-CD20 therapy, CD8 T cells can compensate for impaired humoral immunity. PD-1 blockade increases the activation and proliferation of CD4 T follicular-helper cells, which plays a key role in promoting B cell responses and qualityantibody production. Thus, it is possible that PD-1 blockade enhances the efficacy of SARS-CoV-2 vaccination. However, PD-1 blockade in melanoma patients was actually associated with at 2-fold decrease in SARS-CoV-2specific antibodies and neutralizing antibodies, compared to a healthy donor cohort. PD-1 blockade was alsoassociated with depletion of memory CD4 T cells, suggesting there may be consequences to prolonged PD-1blockade.

Lipid nanoparticles enhance the efficacy of mRNA and protein subunit vaccines by inducing robust T follicular helper cell and humoral responses.

Adjuvants are critical for improving the quality and magnitude of adaptive immune responses to vaccination. Lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA vaccines have shown great efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the mechanism of action of this vaccine platform is not well-characterized. Using influenza virus and SARS-CoV-2 mRNA and protein subunit vaccines, we demonstrated that our LNP formulation has intrinsic adjuvant activity that promotes induction of strong T follicular helper cell, germinal center B cell, long-lived plasma cell, and memory B cell responses that are associated with durable and protective antibodies in mice. Comparative experiments demonstrated that this LNP formulation outperformed a widely used MF59-like adjuvant, AddaVax. The adjuvant activity of the LNP relies on the ionizable lipid component and on IL-6 cytokine induction but not on MyD88- or MAVS-dependent sensing of LNPs. Our study identified LNPs as a versatile adjuvant that enhances the efficacy of traditional and next-generation vaccine platforms.