LIMITED INDUCTION OF LUNG-RESIDENT MEMORY T CELLS BY SARS-CoV-2 mRNA VACCINATION

Background: Resident memory T cells (TRM) present at the respiratory tract may be essential to enhance early SARS-CoV-2 viral clearance, thus limiting viral infection and disease. While long-term antigen-specific TRM are detectable beyond 11 months in the lung of convalescent COVID-19 patients after mild and severe infection, it is unknown if mRNA vaccination encoding for the SARS-CoV-2 S-protein can induce this frontline protection. Method(s): We obtained cross-sectional paired blood and lung biopsy samples from patients (n=30) undergoing lung resection for various reasons and assigned them to one of four groups: I.) uninfected unvaccinated individuals (n=5), II.) unvaccinated long-term SARS-CoV-2 convalescent individuals (between 6.0-10.5 months post-infection;n=9), III.) uninfected and long-term vaccinated individuals (between 6.0-7.7 months after the second or third dose;n=10), and IV.) uninfected and short-term vaccinated individuals (between 1.3-1.8 months after the third or fourth dose;n=6). We determined the presence of SARS-CoV-2-specific CD4+ and CD8+ T cells in blood and lung samples after exposure of cells to M, N, and S peptide pools, followed by flow cytometry to detect TRM cells expressing interferon (IFN)gamma and/or CD107a, as a degranulation marker. Result(s): We found that the frequency of CD4+ T cells secreting IFNgamma in response to S-peptides was variable but detectable in blood and lung up to 8 months after mRNA vaccination. Moreover, the IFNgamma response of CD4+ T cells in the lung of mRNA-vaccinated patients was similar to the response found in convalescent patients. However, in mRNA-vaccinated patients, lung responses presented less frequently with a TRM phenotype compared to convalescent infected individuals and, strikingly, polyfunctional CD107a+ IFNgamma+ TRM were virtually absent in vaccinated patients. Conclusion(s): mRNA vaccines might induce memory responses within the lung parenchyma in some patients, potentially contributing to the overall disease control. However, the robust and broad TRM response established in convalescent-infected individuals may offer advantages at limiting disease if the virus is not blocked by initial mechanisms of protection, such as neutralization. Our results warrant investigation of mucosal vaccine-induced resident T cell responses in establishing superior site-specific protective immunity.

Prolonged fever and inflammation in a young child in the midst of the pandemic - it's not always MIS-C

Case Report: Prolonged fever in children is a symptom that is seen in many different diseases, infections, malignancies, and autoimmune conditions. This can, at times, make the correct diagnosis challenging. A previously healthy 10-year-old male was transferred to our institution with one week history of fever, fatigue, abdominal pain, and vomiting. Laboratory studies demonstrated pancytopenia, transaminitis, electrolyte abnormalities, elevated pro-inflammatory markers & D-Dimer, and hypoalbuminemia. COVID-19 IgG was reactive. Due to the severity in presentation the patient was transferred to the ICU with a presumptive diagnosis of MIS-C. Hewas started on IVIG as well as a five-day course of high-dose methylprednisolone per protocol. Aspirin was added, but later discontinued, due to worsening thrombocytopenia. CT imaging with contrast showed small bilateral pleural effusions & periportal edema, mild splenomegaly, and echocardiogram showed diffuse dilation of the left main and left anterior descending arteries. Given the laboratory findings the differential diagnosis was expanded, Ehrlichia caffeensis serology was sent and empiric Doxycycline started. EBV Nuclear Antigen IgG antibody and EBV Viral Capsid Antigen IgM Antibody resulted as positive suggesting recent or reactivated infection. Respiratory viral PCR with COVID-19, Cytomegalovirus and Parvovirus PCR were negative. Despite initial treatment, the patient continued to have persistent fever, severe pancytopenia, and high ferritin up to 24 426 ng/mL, raising suspicion for Haemophagocytic Lymphohistiocytosis (HLH). Soluble interleukin-2 level was elevated & his presentation was then considered to be more consistent with HLH given that he met 6/8 criteria. Screening for primary HLH including CD107a, perforin and granzyme B, SAP, and XIAP resulted in the latter three being normal but CD107a was abnormal. Next generation sequencing for primary criteria was negative. E. Chaffeensis resulted positive: IgM 1:80, IgG 1:256. MIS-C and HLH have overlapping features but differ in some clinical manifestations. Timely recognition and management is paramount as the management differs. This case illustrates the importance of performing a broad search for potential causes, allowing for appropriate and timely treatment. COVID-19 serology alone should not be the basis for diagnosis of MIS-C in a patient with fever and inflammation. This is important as SARS-CoV2 becomes endemic. Infections such as EBV and Ehrlichiosis should be on the differential particularly in endemic areas and during seasons of higher prevalence for the latter, as these have been well documented to cause HLH. Copyright © 2023 Southern Society for Clinical Investigation.

CD64 GENE-MODIFIED PRIMARY NK CELLS LOADED with ANTI-HIV bNAbs TRIGGER HIGH ADCC

Background: As part of a combined HIV CURE immuno-therapy strategy, we transduced primary human NK cells with the high affinity CD64 Fc receptor and pre-loaded them with HIV-specific bNAbs. We named these chimeric NK cells "NuKES" (NK Enhancement Strategy) for their augmented capacity to mediate ADCC and their potential clinical application as an autologous primary NK cell immuno-therapy against HIV. Methods: We transduced primary NK cells from control donors with a lentivirus expressing human CD64 in the presence or absence of irradiated K562 feeder cells expressing co-stimulatory molecules (CD40, 4-1BB) and/or cytokine pre-stimulation (IL-2, IL-21, IL-15). CD64 expressing NK cells were CFSE labeled and expanded ex vivo or FACS sorted at various times post transduction to high purity. CD64 expressing NK cells were then pre-loaded with HIV-specific bNAbs and tested in a functional ADCC CD107a degranulation assay against HIV-1 infected autologous CD4+ primary T cells. Results: After pre-stimulation with cytokines and/or irradiated K562 Feeder Cells, we could routinely achieve (n=5) greater than 40% CD64 expression in primary human NK cells (Day 14 post-transduction shown in Figure 1A). NK cells maintained strong proliferation potential with greater than 6 cells divisions beyond 10 days post transduction as determined by CFSE dilution (Day 10 post-transduction shown in Figure 1B). Phenotypically, CD64 transduced NK cells were similar to control NK cells and possessed strong expression of CD56, CD16, CD69 with intermediate levels of the NK maturation marker CD57. CD64 transduced NK cells could be successfully pre-loaded with HIV-specific bNAbs and possessed an enhanced capacity (GMFI of 2,014 versus 276) to retain 10-1074 for several hours as compared to control NK cells (Figure 1C). Functionally, CD64 transduced NK cells showed a significant two-fold increase in ADCC-triggered degranulation capacity against autologous HIV-1 infected CD4+ primary T cells compared to control NK cells after pre-loading with HIV-specific bNAbs (27.6% versus 13.2% CD107a). Conclusion: Primary human NK cells can be successfully transduced with CD64 and expanded ex vivo to high purity. Preparation of bNAbs specific NuKES represent a viable autologous NK immuno-therapy approach against HIV-1 with potential adaptation for added disease targets (i.e., COVID, Cancer) moving forward.

T-CELL RESPONSE QUALITY to ACUTE SARS-CoV-2 INFECTION, IMMUNE MEMORY, and HCoV

Background: SARS-CoV-2 specific T-cell response has been associated with disease severity, immune memory and heterologous response to endemic coronaviruses (HCoV). However, an integrative approach combining a comprehensive analysis of the quality of SARS-CoV-2 specific T-cell response and antibody levels is needed. Methods: We assayed SARS-CoV-2 specific T-cell response in 103 participants. Thirty-seven (18 mild and 19 severe) were hospitalized during acute COVID-19 and 33 were recruited seven months after SARS-CoV-2 infection (19 previously hospitalized (H) and 14 non-hospitalized (NH) during acute infection). Pre-COVID-19 healthy donors (HD, n=33) were included. PBMCs were stimulated with Spike (S) and Nucleocapside (N) SARS-CoV-2 peptide pools. Likewise, an optimized peptide pool of HCoV S protein was used in HD. T-cell polyfunctionality by intracellular cytokine staining (IFN-γ, IL-2, TNF-α, CD107a and perforin (PRF)) was assayed by multiparametric flow cytometry together with measurements of T cell subsets, activation, exhaustion and senescence. Anti-S SARS-CoV-2 and HCoV IgG titers and pro-inflammatory markers were measured in plasma. Non-parametric statistic was used for the analysis. Results: Mild disease was associated with high T-cell polyfunctionality biased to IL-2 production and inversely correlated with anti-S IgG levels (eg, N-specific EM CD4+ IL-2+ T-cell, r=-0.594, p=0.004). However, only IFN-γ combinations without PRF production was mostly observed for severe disease (eg, S-specific TEMRA CD4+ CD107a-IFN-γ+IL-2-PRF-TNF-α-T-cells, p=0.008). Moreover, this response was long-lasting seven months after SARS-CoV-2 infection. Both NH and H individuals presented robust anti-S IgG levels and SARS-CoV-2 specific T-cell response. In addition, only H individuals showed a T-cell exhaustion profile (eg, TEMRA CD4+ TIGIT+ T cells, p=0.0004). Combinations including IL-2, but not IFN-γ, in response to HCoV S protein, were associated with SARS-CoV-2 S-specific T-cell response in HD (eg, S-specific CM CD8+ CD107a-IFN-γ-IL-2+PRF-TNF-α-T-cells, r=5414, p=0.001). Conclusion: T-cell polyfunctionality features were associated with disease severity. Moreover, T-cell response was robust seven months after infection, although previously hospitalized patients showed signs of exhaustion. SARS-CoV-2 and HCoV immune cross-reactivity have implications for protective immunity against SARS-CoV-2 to design new prototypes of vaccines in order to achieve of broader long-lasting protection against COVID-19.

DEFINING IMMUNOGENIC PEPTIDES TARGETING SARS-CoV-2 VARIANTS of CONCERN

Background: Identifying Severe Acute Respiratory Syndrome Coronavirus Type 2 (SARS-CoV-2) specific T-cell epitope-derived peptides that are also found within variants of concern (VOC) is critical for measuring the duration of cellular immunity induced by the virus and COVID-19 vaccines. Therefore, we assessed whether the peptides selected from topologically important regions of SARS-CoV-2 proteins avoid major mutations of VOC and induce T-cell immune response. Methods: We selected 32 peptides within topologically important regions of SARS-CoV-2 Spike (S) and Nucleocapsid (NC) proteins by applying an insilico pipeline to 607 viral sequences in 2019. To determine if these peptides avoid VOC mutations, we analyzed S and NC protein regions derived from 1.7 x 106 viral genomic sequences compiled from Mar 2020-Aug 2021. We identified α-, β-and δ-VOC mutations found within >1% of the S and NC protein sequences. These mutations were compared to the peptides. To determine T-cell immune response to these selected peptides as a pool, we assessed interferon-γ (IFN-γ), interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α) and CD107a/b (degranulation marker) production within peripheral blood mononuclear cell (PBMC) samples derived from COVID-19 post-recovery donors (n=23) by employing dual color FluoroSpot and intracellular cytokine staining (ICS). Results: We found 88% of S protein-derived peptides did not contain mutations of α-, β-and δ-VOC. All peptides from S protein (n=25) avoided known T-cell escape mutations. Of the 7 NC-derived peptides, three contained the L139F mutation found within α-and δ-VOC, however, this mutation was observed within <2% NC protein sequences. A peptide pool containing our 32 selected peptides elicited an immune response within PBMCs from 17/23 COVID-19 post-recovery donors. FluoroSpot analysis revealed IFN-γ and IL-2 production to our peptide pool was similar/higher compared to the commercial S and NC peptide pools. The response of CD4 and CD8 T-cells to our peptide pool was polyfunctional expressing ≥2 markers within most of the donors when ICS was performed, with IFN-γ and TNF-α being the main cytokines produced. Conclusion: Applying an immunoinformatics pipeline allowed us to select peptides from the S and NC proteins which avoid the majority of mutations found within the α-, β-and δ-VOC. Our peptide pool elicited a polyfunctional T-cell response making it an ideal candidate for assessing the duration of cellular immunity induced by SARS-CoV-2 variants and vaccines.

NATURAL KILLER CELL-MEDIATED ADCC in SARS-CoV-2 INFECTION and VACCINATION

Background: COVID-19, caused by SARS-CoV-2, has emerged as a global pandemic. While immune responses of the adaptive immune system have been in the focus of research, the role of Natural killer (NK) cells in COVID-19 remains poorly understood. Methods: We characterized NK cell-mediated SARS-CoV-2 antibody-dependent cellular cytotoxicity (ADCC) against SARS-CoV-2 spike-1 (S1) and nucleocapsid (NC) protein using NK cell degranulation (CD107a) and killing assays. Results: Serum samples from SARS-CoV-2 resolvers induced significant CD107a expression by NK cells in response to S1 and NC (p < 0.0001), while serum samples from SARS-CoV-2-negative individuals did not. Furthermore, serum samples from individuals that received the BNT162b2 vaccine induced strong CD107a expression by NK cells that increased with the second vaccination and was significantly higher than observed in infected individuals (p < 0.0001). As expected, vaccine-induced responses were directed against S1 and not against NC protein. S1-specific CD107a responses by NK cells were significantly correlated to NK cell-mediated killing of S1-expressing cells (r = 0.86, p = 1.82 x 10-6). Interestingly, screening of serum samples collected prior to the COVID-19 pandemic identified two individuals with cross-reactive antibodies against SARS-CoV-2 S1, which also induced degranulation of NK cells. Conclusion: These data demonstrate that antibodies induced by SARS-CoV-2 infection and anti-SARS-CoV-2 vaccines can trigger significant NK cell-mediated ADCC activity, and identify some cross-reactive ADCC activity against SARS-CoV-2 by endemic coronavirus-specific antibodies.

TCR SEQUENCING of EPITOPE-SPECIFIC T CELLS from SARS-CoV-2 CONVALESCENT INDIVIDUALS

Background: T cells have been shown to play a role in the immune response to SARS-CoV-2. Identification of T cell epitopes and a better understanding of the T cell repertoire will provide important insights into how T cells impact antiviral immunity. Here, we identified T cell epitopes within the Spike (S), Nucleocapsid (N) and Membrane (M) proteins from SARS-CoV-2 convalescent individuals and performed TCR sequencing on epitope-specific T cells. Methods: Epitope mapping was performed by IFNγ ELISpot on PBMC from SARS-CoV-2 convalescent patients with mild/moderate disease (n = 19 for S;n=15 for N and M), and minimum epitopes were determined using truncated peptides and ICS. TCR sequence analysis was performed on a subset of individuals (n=9 donors;2-3 epitopes/donor), with longitudinal samples for 7 donors (2-3 time points/donor;33 to 236 days post-symptom onset). T cells were stimulated with individual peptides for 6 hours and sorted based on the expression of activation markers (CD4+: CD69, CD40L;CD8+: CD69, CD107a, surface TNF). scRNAseq was performed on sorted cells for TCR repertoire and transcriptome analysis. Results: We identified several peptides recognized by multiple individuals, including S42 (amino acids 165-179;7/19 donors), S302 (a.a. 1205-1219;6/19 donors), N27 (a.a. 106-120;6/14 donors) and M45 (a.a. 177-191;10/14 donors). S42 elicited both CD4+ (n=5) and CD8+ (n=1) T cell responses, with one individual having both a CD4+ and CD8+ response. The minimum epitope for S42 was determined to be a 9mer (FEYVSQPFL) for both CD4+ and CD8+ cells. TCR sequencing of S42-specific T cells identified a dominant gene pairing for TCRα across multiple donors (TRAV35;TRAJ42) and for both CD4+ and CD8+ T cells (Figure 1). In general, epitope-specific CD4+ responses (S42, M45) were more clonally diverse than CD8+ responses (S42, S302, N27). For both CD4+ and CD8+ T cells, conserved TCR gene usage and gene pairings could be identified within multiple donors responding to the same epitope. Conclusion: These data suggest that in SARS-CoV-2 convalescent people, epitope-specific CD4+ and CD8+ T cells can differ in their clonal diversity and that related TCRs can be identified across multiple donors. S42-specific T cell studies are ongoing to determine their transcriptional profile and pMHC presentation. Ongoing longitudinal analysis will provide a better understanding of different epitope-specific TCR repertoires and T cell transcriptional profiles, and how they evolve after infection.

IMMUNE PARAMETERS ASSOCIATED with LOWER SARS-CoV-2 VACCINATION RESPONSE in OLD PEOPLE

Background: The number of cases of SARS-CoV-2 infection after BNT162b2 mRNA vaccination is significantly higher in elderly people, which has been associated to lower frequencies of SARS-CoV-2 neutralizing antibodies. Our objective was to investigate the differences in the cellular response in old and young people after the SARS-CoV-2 vaccination. Methods: Young (24-53 years, n=20) and old (70-76 years, n=20) healthy subjects vaccinated with BNT162b2 SARS-CoV-2 mRNA vaccine were studied before vaccination, two weeks after the first dose and two months after the second dose. SARS-CoV-2 (spike) specific T cell response, TLR-4 dependent monocyte response and TLR-3 dependent myeloid dendritic cell (DC) response and DC, monocyte and T-cell immunophenotype, were studied by multiparametric flow cytometry. TLR-9 dependent interferon-α (IFNα) production by PBMCs was measured by ELISA and thymic function assayed by sj/β TREC ratio using droplet digital PCR. Results: The SARS-CoV-2 specific T cell response was lower and less polyfunctional in old people. Most of the differences in CD4+ and CD8+ T cell subsets were found in degranulation (CD107a), cytokine (IFN-γ) and cytotoxic (perforin) profile (eg, Memory CD8+ perforin+;p=0.0016). The lower SARS-CoV-2 specific T cell response was associated with lower thymic function levels (eg, Memory CD4+ perforin+, r=0.631;p=0.0001). The vaccination induced a higher activation and proliferation (eg, CM CD4 HLA-DR+ p=0.002, Ki67+ p=0.019) of T cells in young people than in old ones, in addition to a higher level of homing makers to different tissues and inflammatory sites (eg, CD1c mDC integrin β7+ p=0.001, intermediate monocytes CCR2+ p=0.0003) in DCs and monocytes. Moreover, after the vaccination, old subjects showed a higher production of proinflammatory cytokines by monocytes in response to LPS (eg, IL6+;p=0.015), while young people showed a higher production of IFNα by plasmacytoid DCs after CpG-A stimulation (p=0.0009). Conclusion: The magnitude and polyfunctionality of SARS-CoV-2 specific T cell response is lower in old people, associated to a lower thymic function. In old people, the vaccination induced less immune activation and homing and the myeloid TLR-dependent response is directed towards a proinflammatory response, while in young people prevails IFNα production, related to a more effective antiviral response. These results support the additional boosting strategies in this vulnerable population.

Pharmacologic inhibition of SUMOactivating enzyme potentiates interferon response and T cell-mediated anti-tumor immunity in chronic lymphocytic leukemia (CLL) and lymphoma models

Introduction: CLL is characterized by deficient immunity which clinically manifests as an increased predisposition toward malignancies and infectious complications. T-cells from patients with CLL exhibit a skewed repertoire with a predominance of Tregs as well as impaired immune synapse formation and cytotoxic function. Unlike chemotherapy, novel targeted agents may have beneficial immunomodulatory effects, which may be particularly relevant in the COVID-19 era. Small ubiquitin-like modifier (SUMO) family proteins regulate a variety of cellular processes, including nuclear trafficking, gene transcription, and cell cycle progression, via post-translational modification of target proteins. Sumoylation regulates NFjB signaling, IFN response, and NFAT activation, processes indispensable in immune cell activation. Despite this, the role of sumoylation in T cell biology in the context of cancer is not known. TAK-981 is a small molecule inhibitor of the SUMO-activating enzyme (SAE) that forms a covalent adduct with an activated SUMO protein, thereby preventing its transfer to the SUMO-conjugating enzyme (Ubc9). Here, we investigated the immunomodulatory effects of TAK-981 in CLL. Methods: T cells from patients with CLL were purified using Dynabeads. Activation, proliferation, and apoptosis of CD3+ T cells were studied following T-cell receptor engagement (TCR;aCD3/CD28) with/without 0-1 lM TAK-981. Cytokines were measured after in vitro stimulation. For polarization assays, FACS-sorted naïve CD4+ T cells were cultured for 7 days in control or differentiation media. For gene expression profiling (GEP;Clariom S), RNA was harvested after 3 and 24 h of TCR engagement from FACS-sorted naïve CD4+ T cells. For in vivo immunization experiments, CD4+KJ1-26+ cells were inoculated IV into BALB/cJ mice. Mice received 100 mg IV ovalbumin ± R848 followed by TAK-981 7.5 mg/kg or vehicle control IV twice weekly for 10 days before spleen collection. Both recipient and transplanted splenocytes were analyzed. For analysis of tumor-infiltrating lymphocytes (TILs), BALB/c mice were injected with 1×106 A20 lymphoma cells and treated as above. TAK-981 was provided by Millennium Pharmaceuticals, Inc. (Cambridge, MA, USA). Results: T cells from patients with CLL demonstrated high baseline protein sumoylation that slightly increased following TCR engagement. Treatment with TAK-981 significantly downregulated SUMO1 and SUMO2/3-modified protein levels, yet did not disrupt early TCR signaling as evidenced by sustained ZAP70, p65/NFjB, and NFAT activation detected by immunoblotting, immunocytochemistry, and GEP. Treatment with TAK-981 resulted in dose-dependent upregulation of the early activation marker CD69 in CD4+ T cells following 72 and 96 h of TCR stimulation vs. control. Meanwhile, the expression of CD25, HLA-DR, and CD40L was delayed in the presence of TAK-981. Interestingly, CD38, an IFN response target, was induced 2-fold in TAK-981-treated cells after 24 h and persisted at high levels at subsequent timepoints. T cell proliferation was reduced in the presence of high (1 lM) but not low/intermediate concentrations of TAK-981, accompanied by reduced S phase entry and decreased synthesis of IL- 2. However, T cells did not undergo apoptosis under those conditions. Targeting SAE in either control or Th1/Treg polarizing conditions facilitated an increase in IFNc and loss of FoxP3 expression (accompanied by decreased IL-2/STAT5), suggesting a shift toward Th1 and away from Treg phenotype, respectively. GEP (Reactome, GSEA) confirmed a dramatically upregulated IFN response in TAK-981-treated CD4+ naïve T cells. Furthermore, targeting SAE enhanced degranulation (CD107a), IFNc, and perforin secretion in cytotoxic CD8+ T cells and potentiated T cell cytotoxicity in allogeneic assays with lymphoma cells (OCI-LY3, U2932) as targets. Consistent with our in vitro data, OVA-stimulated transplanted transgenic KJ1-26+ splenocytes, as well as total CD4+ T cells from recipient mice treated with TAK-981 in vivo exhibited a significant reduction in express on of FoxP3 and an increased production of IFNc. In the A20 syngeneic model, treatment with TAK-981 similarly downregulated FoxP3 expression in CD4+ TILs and induced IFNc secretion in CD8+ TILs. Conclusion: Using a combination of in vitro and in vivo experiments, we demonstrate that pharmacologic targeting of sumoylation with TAK-981 does not impair proximal TCR signaling in T cells obtained from patients with CLL, but leads to rebalancing toward healthy immune T cell subsets via induction of IFN response and downmodulation of Tregs. These data provide a strong rationale for continued investigation of TAK-981 in CLL and lymphoid malignancies.

Oral Tablet Vaccination Induces Heightened Cross-Reactive CD8 T Cell Responses to SARS-COV-2 in Humans

Background. Covid-19 has accelerated global demand for easily distributed vaccines. Furthermore, as variant SARS-CoV-2 strains that circumvent antibody responses emerge, cross-protective vaccines provide substantial public health benefits. Vaxart is developing a shelf stable oral tablet vaccine that incorporates both the spike (S) and the more conserved nucleocapsid (N) proteins. Vaxart's vaccine platform uses a non-replicating adenovirus and a TLR3 agonist as an adjuvant. Methods. In an open-label phase 1 clinical study, 35 healthy subjects received either a single low (1x1010 IU;n=15) or high (5x1010 IU;n=15) dose of the vaccine candidate VXA-CoV2-1 with a small cohort receiving 2 low doses. PBMCs were taken at pre- and 7 days post-vaccination and restimulated with S and N peptides from SARSCoV-2 or the 4 human endemic coronaviruses (HCoV). Cells were stained for CD4/ CD8/CD107a (surface) and IFNγ/TNFα (intracellular). Subjects that received an intramuscular (i.m.) mRNA vaccine had PBMCs taken at the same timepoints and were compared in the same assay. Results. The study's results indicate that the VXA-CoV2-1 tablet was well tolerated. The majority of subjects had an increase in S-specific anti-viral CD8+ T cell responses. 19/26 (73%) subjects had a measurable CD8+ T cell response on day 8 above baseline, on average 1.5-4.6%. In a comparator experiment with the 2 SARS-CoV-2 i.m. mRNA vaccines, VXA-CoV2-1 outperformed other vaccine candidates with a >3.5-fold increase in S specific antiviral CD8 T cell responses. T cell responses specific to the 4 endemic HCoV were increased by 0.6% in subjects given VXA-CoV2-1. Conclusion. Here we describe a room temperature stable tablet that induces SARS-CoV-2 S specific CD8 T cells of high magnitude after one dose in humans. Overall, the level of antiviral SARS-CoV-2 specific T cells, particularly IFNg-producing CD8s, induced following oral immunization with VXA-CoV2-1 are of higher magnitude than the mRNA vaccines currently in use against COVID-19. T cell responses against 4 endemic HCoV were also induced. Because T cells may be important in protecting against death and severe infection, these results suggest that VXA-CoV2-1 could be cross-protective against a wide array of emerging pandemic coronaviruses.

CORRELATION OF IMMUNOLOGICAL MARKERS LEVELS (IL-2Ra, CD107A & FASL) WITH THE SEVERITY OF COVID-19 PATIENTS

The coronavirus disease 2019 (COVID-19) pandemic is the most severe worldwide crisis;it affects both human lives and the global economy;according to WHO, there are 156,496,592 confirmed cases, including 3,264,143 deaths up to 6 May 2021. The causative agent of COVID-19 is Coronavirus;lymphocyte count has been a marker of interest since the first COVID-19 publication. Lymphopenia is related to the disease severity;many immunological markers such as IL2Rá, CD107a and FasL can affect lymphopenia. To evaluate immunological markers (IL2Rá, CD107a and FasL) in mild and severe COVID-19 patients and correlation with disease severity and lymphopenia. Eighty-eight proofed COVID-19 patients were enrolled in this study, divided into two groups: mild and severe according to patients signs and symptoms, their lymphocytes count and immunological markers (IL2Rá, CD107a and FasL) were measured and statistically correlated. In mild patients group: the median age 57.7 years ± 12.7 (18-75 years), 25 males and 19 females, male to female ratio were 1:1, their WBC was 6.44 ± 2.2, ranging from 3.4 to 12.4, the lymphocytes were 2.8 ± 0.71 ranging from 1.6-4.2. In sever group patients: the median age 43 years ± 14.4 (26-80 years), 22 males and 22 females, male to female ratio was 1.3:1 their WBC was 12.1 ± 4.6, ranging from 4.1 to 26.6, Lymphocytes were 1.29 ± 0.69 ranging from 0.3-3.4. There was a significant difference between mild and severe cases for age, WBC and lymphocytes (P<0.05). Gender distribution was not significantly related to disease activity (P>0.05). Lymphopenia was not found in mild cases but 59.1% of severe cases had lymphopenia (P<0.05). There was a significant difference between mild and severe cases for IL2-Ra and CD107 (P<0.005). No significant relation between FasL and disease severity in our specimen. In conclusion, measuring serum levels of IL-2R, CD107a and FasL in COVID-19 patients will serve as a sensitive marker for monitoring patients conditions and provide a suitable tool to verify which patient will develop severe lymphopenia and may need care in the intensive care unit.

Characterization of the Early Humoral and Cellular Response Developed in Oncohematological Patients Post-Vaccination with One Dose Against COVID-19

[Formula presented] Background: Oncohematological patients present a variable immune response against many vaccines, due to the immunodeficiency caused by the disease and its treatment. The experience of vaccination against COVID-19 in oncohematological patients is low and mostly limited to studies of humoral immunity. However, the humoral and cellular immune responses between different oncohematological diseases (OHD) have not been compared. Objective: To compare the humoral and cellular immune responses in four groups of patients with OHD after receiving the first dose of one COVID-19 vaccine. Materials & methods: We recruited 53 patients in four groups according to diagnosis: Chronic Lymphatic Leukemia (CLL) (n=14), Chronic Myeloid Leukemia (CML) (n=11), Multiple Myeloma (MM) (n=15), and Allogeneic Hematopoietic Stem Cell Transplantation (ASCT) (n=13) (Table 1). Samples were collected prior to vaccination and 3 weeks after receiving one dose of COMIRNATY (BioNTech-Pzifer), mRNA-1273 (Moderna), or AZD1222 (AstraZeneca). Twenty-six healthy donors with similar vaccination pattern were recruited. IgG titers against SARS-CoV-2 were quantified by Euroimmun-Anti-SARS-CoV-2 ELISA. Direct cellular cytotoxicity (DCC) was determined against Vero E6 cells infected with pseudotyped SARS-CoV-2, measuring caspase-3 activation after co-culture with PBMCs, in which cytotoxic populations were phenotyped by flow cytometry. Antibody-dependent cellular cytotoxicity (ADCC) analyses were performed using Annexin V on Raji cells as a target. Results: 1) Early humoral response against COVID-19 vaccination in patients with CML was 5.1- (p<0.0001), 2.8- (p=0.0027), and 3.2-fold (p<0.0001) higher than in patients with CLL, MM and HSCT, respectively, and 3.5-fold higher than in healthy donors (p=0.0460) (Fig. 1). 84% of CLL patients did not develop detectable IgG titers. Individuals with OHD developed lower titres of neutralizing antibodies than healthy donors. 2) Unspecific ADCC was overall reduced in patients with OHD, mostly in individuals with ASCT (3.2-fold lower (p<0,0001)), whereas ADCC was reduced 2.2- (p<0.0001), 1.8- (p=0.0040), and 2.2-fold (p<0.0001) in individuals with CLL, CML and MM, respectively (Fig. 2A). However, specific DCC was increased 4.7-, 8.1- (p=0.0189), and 2.1-fold, respectively, in PBMCs from patients with CLL, MM, or ASCT, in comparison with healthy donors, whereas patients with CML showed a very similar response than healthy donors (Fig. 2B). 3) Levels of CD3+CD8+TCRγδ+ T cells were increased 2.2-, 2.1-, 2.7-, and 4.3-fold (p=0.0394) in patients with CLL, CML, MM, and ASCT, respectively, in comparison with healthy donors. CD3+CD8-TCRγδ+ T cells were also increased in patients with OHD, expressing high levels of the degranulation marker CD107a. However, the levels of CD3-CD56+CD107a+ NK cells were reduced 4.2- (p=0.0003) and 3.6-fold (p=0.0010) in PBMCs from patients with MM and ASCT, respectively, in comparison with healthy donors. Conclusions: We found significant differences in the early humoral immune response after one single dose of COVID-19 vaccine depending on the OHD analyzed. It was observed for the first time that the early cytotoxic immune response is efficient in all groups of patients, although superior in those who were not exposed to ASCT. Most cytotoxic activity relied on CD8+ T cells. These data can be useful to determine the efficacy of COVID-19 vaccines in patients with OHD. [Formula presented] Disclosures: Garcia Gutierrez: BMS: Consultancy, Honoraria, Research Funding;Novartis: Consultancy, Honoraria, Research Funding;Incyte: Consultancy, Honoraria, Research Funding;Pfizer: Consultancy, Honoraria, Research Funding.