Specific T-cell Responses Research Articles

Secreted NS1 proteins of tick-borne encephalitis virus and West Nile virus block dendritic cell activation and effector functions.

The flavivirus non-structural protein 1 (NS1) is secreted from infected cells into the circulation and the serum levels correlate with disease severity. The effect of secreted NS1 (sNS1) on non-infected mammalian immune cells is largely unknown. Here, we expressed recombinant sNS1 proteins of tick-borne encephalitis virus (TBEV) and West Nile virus (WNV) and investigated their effects on dendritic cell (DC) effector functions. Murine bone marrow-derived DCs (BMDCs) showed reduced surface expression of co-stimulatory molecules and decreased release of pro-inflammatory cytokines when treated with sNS1 of TBEV or WNV prior to poly(I:C) stimulation. Transcriptional profiles of BMDCs that were sNS1-exposed prior to poly(I:C) stimulation showed two gene clusters that were downregulated by TBEV or WNV sNS1 and that were associated with innate and adaptive immune responses. Functionally, both sNS1 proteins modulated the capacity for BMDCs to induce specific T-cell responses as indicated by reduced IFN-γ levels in both CD4+ and CD8+ T cells after BMDC co-cultivation. In human monocyte-derived DCs, poly(I:C)-induced upregulation of co-stimulatory molecules and cytokine responses were even more strongly impaired by TBEV sNS1 or WNV sNS1 pretreatment than in the murine system. Our findings indicate that exogenous flaviviral sNS1 proteins interfere with DC-mediated stimulation of T cells, which is crucial for the initiation of cell-mediated adaptive immune responses in human flavivirus infections. Collectively, our data determine soluble flaviviral NS1 as a virulence factor responsible for a dampened immune response to flavivirus infections. IMPORTANCE The effective initiation of protective host immune responses controls the outcome of infection, and dysfunctional T-cell responses have previously been associated with symptomatic human flavivirus infections. We demonstrate that secreted flavivirus NS1 proteins modulate innate immune responses of uninfected bystander cells. In particular, sNS1 markedly reduced the capacity of dendritic cells to stimulate T-cell responses upon activation. Hence, by modulating cellular host responses that are required for effective antigen presentation and initiation of adaptive immunity, sNS1 proteins may contribute to severe outcomes of flavivirus disease.

KS01.6.A UCPVAX-GLIO: A PHASE II TRIAL EVALUATING THE IMMUNOGENICITY AND EFFICACY OF AN ANTI-TELOMERASE VACCINE IN PATIENTS WITH NEWLY DIAGNOSED GBM

Abstract BACKGROUND The Telomerase Reverse Transcriptase (TERT) is activated in 85%-90% of cancers, and glioblastomas (GBM) harbor the highest incidence of activating mutations within its promoter (over 85% of patients). This high expression of TERT in cancers and its role in oncogenesis make TERT a very promising tumor antigen for immunotherapy, especially in GBM. UCPvax is a therapeutic vaccine in which two CD4 helper peptides derived from TERT are mixed with the Montanide adjuvant. This phase IIa trial was designed to test the immunogenicity, safety and efficacy of UCPvax in patients with newly diagnosed GBM. PATIENTS AND METHODS In this first cohort of the UCPvax-glio trial (NCT04280848), patients with unmethylated MGMT non-mutated IDH1 GBM were included if they had a Karnofsky Performance status (KPS) ≥ 70%, a steroid treatment < 10mg/ day equivalent prednisone, and lymphocytes count ≥ 0.8 x 109/L. One month after completion of radiation/ temozolomide (TMZ), patients started UCPvax vaccinations on days 1, 8, 15, 29, 36 and 43, then every two months until tumor progression. Patients did not receive any additional cure of TMZ because of the unmethylated MGMT promoter status. Peripheral blood mononuclear cells were collected before treatment, at 1 and 2 months after treatment, and at each vaccination boost. The primary endpoint was the anti-TERT specific CD4 T-cell response at 2 months using IFN-gamma ELISPOT. Secondary endpoints included safety, progression-free survival (PFS) and overall survival (OS). RESULTS All the 31 patients (median age 60-yr old, median KPS 90%) included in this study received at least one vaccination. Vaccinations were given for 4.5 months on average (min 2- max 14). At baseline, only one patient had a pre-existing anti-TERT CD4 T-cell response (3%). After immunizations, de novo induction and/or amplification of an anti-TERT response were found in 29/30 patients (97%). An epitope spread response against other tumor-associated antigens was detected in 12/25 patients (48%). All patients developed local skin reactions (≤ grade 2), 16 patients complained of transient asthenia (≤grade 2), and 13 patients experienced local pain (≤grade 2). No severe (grade 3-4) toxicity was attributable to the vaccination. In the intent-to-treat population (n = 31), the PFS was 8.9 months (95% CI: 7.6-10.6) and the median OS was 17.9 months (95% CI: 16-23). Two years after diagnosis, 26% of the patients were still alive. OS was significantly improved in the patients developing an epitope spread response vs the others (20.8 versus 14.1 months, respectively, p = 0.03). CONCLUSION s: In this population of unmethylated MGMT GBM patients, UCPVax is highly immunogenic and provides an interesting OS rate. These data strongly support the completion of the second ongoing cohort, assessing UCPvax in combination with TMZ for GBM patients with methylated MGMT promoter status.

The impact of BNT162b2 mRNA vaccine on adaptive and innate immune responses

The mRNA-based BNT162b2 protects against severe disease and mortality caused by SARS-CoV-2 via induction of specific antibody and T-cell responses. Much less is known about its broad effects on immune responses against other pathogens. Here, we investigated the adaptive immune responses induced by BNT162b2 vaccination against various SARS-CoV-2 variants and its effects on the responsiveness of immune cells upon stimulation with heterologous stimuli. BNT162b2 vaccination induced effective humoral and cellular immunity against SARS-CoV-2 that started to wane after six months. We also observed long-term transcriptional changes in immune cells after vaccination. Additionally, vaccination with BNT162b2 modulated innate immune responses as measured by inflammatory cytokine production after stimulation - higher IL-1/IL-6 release and decreased IFN-α production. Altogether, these data expand our knowledge regarding the overall immunological effects of this new class of vaccines and underline the need for additional studies to elucidate their effects on both innate and adaptive immune responses.

Association between HSP-Specific T-Cell Counts and Retinal Nerve Fiber Layer Thickness in Patients with Primary Open-Angle Glaucoma.

Previous laboratory reports implicate heat shock protein (HSP)-specific T-cell responses in glaucoma pathogenesis; here, we aimed to provide direct clinical evidence by correlating systemic HSP-specific T-cell levels with glaucoma severity in patients with primary open-angle glaucoma (POAG). Cross-sectional case-control study. Thirty-two adult patients with POAG and 38 controls underwent blood draw and optic nerve imaging. Peripheral blood monocytes (PBMC) were stimulated in culture with HSP27, α-crystallin, a member of the small HSP family, or HSP60. Both interferon-γ (IFN-γ)+ CD4+ T helper type 1 cells (Th1) and transforming growth factor-β1 (TGF-β1)+ CD4+ regulatory T cells (Treg) were quantified by flow cytometry and presented as a percentage of total PBMC counts. Relevant cytokines were measured using enzyme-linked immunosorbent assays. Retinal nerve fiber layer thickness (RNFLT) was measured with OCT. Pearson's correlation (r) was used to assess correlations. Correlations of HSP-specific T-cell counts, and serum levels of corresponding cytokine levels with RNFLT. Patients with POAG (visual field mean deviation, -4.7 ± 4.0 dB) and controls were similar in age, gender, and body mass index. Moreover, 46.9% of POAG and 60.0% of control subjects had prior cataract surgery (P= 0.48). Although no significant difference in total nonstimulated CD4+ Th1 or Treg cells was detected, patients with POAG exhibited significantly higher frequencies of Th1 cells specific for HSP27, α-crystallin, or HSP60 than controls (7.3 ± 7.9% vs. 2.6 ± 2.0%, P= 0.004; 5.8 ± 2.7% vs. 1.8 ± 1.3%, P < 0.001; 13.2 ± 13.3 vs. 4.3 ± 5.2, P= 0.01; respectively), but similar Treg specific for the same HSPs compared with controls (P ≥ 0.10 for all). Concordantly, the serum levels of IFN-γ were higher in POAG than in controls (36.2 ± 12.1 pg/ml vs. 10.0 ± 4.3 pg/ml; P < 0.001), but TGF-β1 levels did not differ. Average RNFLT of both eyes negatively correlated with HSP27- and α-crystallin-specific Th1 cell counts, and IFN-γ levels in all subjects after adjusting for age (partial correlation coefficient r= -0.31, P= 0.03; r= -0.52, p= 0.002; r= -0.72, P < 0.001, respectively). Higher levels of HSP-specific Th1 cells are associated with thinner RNFLT in patients with POAG and control subjects. The significant inverse relationship between systemic HSP-specific Th1 cell count and RNFLT supports the role of these T cells in glaucomatous neurodegeneration. Proprietary or commercial disclosure may be found after the references.

Neutralizing antibody and T-cell responses against SARS-CoV-2 variants by heterologous CoronaVac/ChAdOx-1 vaccination in elderly subjects with chronic obstructive pulmonary disease

BackgroundData on humoral and cellular immune responses against SARS-CoV-2 after receiving heterologous CoronaVac/ChAdOx-1 (CoVac/ChAd) vaccination in subjects with chronic obstructive pulmonary disease (COPD) are still limited. Therefore, we determined the neutralizing antibody (NAb) and T-cell responses against SARS-CoV-2 wild type (WT) and variants of concern (VOCs) in COPD patients. MethodsThe levels of NAb as well as specific CD4 and CD8 T-cell responses against SARS-CoV-2 WT and VOCs were determined in COPD patients before and after vaccination. ResultsFour weeks after vaccinations, the median levels of % inhibition of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants were significantly higher compared to pre-vaccination. The induction of NAb against Omicron was very low compared to other variants. At four weeks after vaccination, in comparison to pre-vaccination, the increasing trend of TNF-α-, IFN-γ-, IL-4-, IL-17-, IL-10-, and FasL-producing CD4 T-cells upon stimulation with WT spike peptides were demonstrated. No difference in T-cell responses to spike peptides of Alpha, Beta, and Delta variants and their WT homologs was observed. ConclusionHeterologous CoVac/ChAd vaccine induced the production of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants, but low for Omicron in COPD patients. Induction of CD4 T-cell subset responses was slightly observed by this vaccine regimen.Clinical Trials Registry: This study was approved by the Clinical Trials Registry (Study ID: TCTR20210822002).

Proportion of Ugandans with pre-pandemic SARS-CoV-2 cross-reactive CD4+ and CD8+ T-cell responses: A pilot study.

The estimated mortality rate of the SARS-CoV-2 pandemic varied greatly around the world. In particular, multiple countries in East, Central, and West Africa had significantly lower rates of COVID-19 related fatalities than many resource-rich nations with significantly earlier wide-spread access to life-saving vaccines. One possible reason for this lower mortality could be the presence of pre-existing cross-reactive immunological responses in these areas of the world. To explore this hypothesis, an exploratory study of stored peripheral blood mononuclear cells (PBMC) from Ugandans collected from 2015-2017 prior to the COVID-19 pandemic (n = 29) and from hospitalized Ugandan COVID-19 patients (n = 3) were examined using flow-cytometry for the presence of pre-existing SARS-CoV-2 cross-reactive CD4+ and CD8+ T-cell populations using four T-cell epitope mega pools. Of pre-pandemic participants, 89.7% (26/29) had either CD4+ or CD8+, or both, SARS-CoV-2 specific T-cell responses. Specifically, CD4+ T-cell reactivity (72.4%) and CD8+ T-cell reactivity (65.5%) were relatively similar, and 13 participants (44.8%) had both types of cross-reactive types of T-cells present. There were no significant differences in response by sex in the population, however this may be in part due to the limited sample size examined. The rates of cross-reactive T-cell populations in this exploratory Ugandan population appears higher than previous estimates from resource-rich countries like the United States (20-50% reactivity). It is unclear what role, if any, this cross-reactivity played in decreasing COVID-19 related mortality in Uganda and other African countries, but does suggest that a better understanding of global pre-existing immunological cross-reactivity could be an informative data of epidemiological intelligence moving forward.

IMMUNE RESPONSE TO SARS-COV-2 IN PATIENTS WITH CHRONIC HIV INFECTION

Introduction. Data for the long-term effects of SARS-CoV-2/HIV co-infection on immune restoration, as well as the level of post-exposure and post-vaccination immunity at the current stage of SARS-CoV-2 pandemic in HIV+ individuals is still scarce. We assessed SARS-CoV-2-specific immune responses, and the effects of SARS-CoV-2 infection on the immune recovery in HIV+cART+ patients with different exposure history. Materials and methods. HIV+cART+ patients 9 (2-18) months after mild/moderate COVID-19 and completed immunization with anti-SARS-CoV-2 vaccine (n=13, group A), convalescent, not immunized (n=11, group B), or with no history of exposure to SARS-CoV-2 (n=11, group C) were included in the study. CD4AC and CD4/CD8 ratio were determined before and after the documented/probable contact with SARS-CoV-2 by 4-color flow cytometry (TRUCount, MultiTest, FACSCanto II). Virus-specific immunity was characterized by the SARS-CoV-2 specific IFNγ production (SARS-CoV-2 IGRA, Euroimmun) and the levels of RBD-IgG ((Euroimmun ELISA). Results. SARS-CoV-2 specific T-cell and IgG responses were highly correlated and present, respectively, in 92% and 100%; 64% and 54%, 36% and 50% from group A, B and C patients. SARS-CoV-2 specific IFNy+T cells and RDB-IgG were significantly higher in the group with hybrid exposure (A) as compared to convalescent (B) and asymptomatic (C) patients. No significant difference existed between background and actual CD4AC (mean 836 vs 799 cells/µl, p&gt;0.05, Mann-Whitney), and the CD4/CD8 ratio significantly increased in the group with hybrid exposure (0.92 vs 1.07, p&lt;0.01, paired T-test). Conclusion. Over 80% of tested HIV+ individuals have mounted a SARS-CoV-2 specific immune response. Immunization and hybrid exposure provide a durable and significantly stronger SARS-CoV-2-specific immune response as compared to mild/ asymptomatic infection, without affecting the long-term immune recovery.

Human Cytomegalovirus (HCMV) - specific T-cell response after letermovir prophylaxis is predictive for subsequent HCMV reactivation in haematopoietic stem cell transplant recipients.

Human Cytomegalovirus (HCMV) is still one of the major concerning infection in hematopoietic stem cell transplant (HSCT) recipients. Letermovir (LTV) has been recently introduced for HCMV prophylaxis in adult patients who received allogeneic HSCT. However, many aspects related to immune reconstitution need to be further explored. The aim of this study was to define the prognostic role of HCMV-specific T-cell frequency measured at the end of LTV prophylaxis in predicting the risk for clinically significant HCMV infection (i.e. infection requiring antiviral treatment) after the stop of the prophylaxis. Sixty-six adult patients who underwent allogeneic HSCT were enrolled and HCMV DNAemia was prospectively monitored. Additionally, HCMV-specific T-cell response was evaluated using ELISpot assay against two different antigens (HCMV infected cell lysate and pp65 peptide pool). Ten patients (15.2%) developed at least one positive HCMV DNAemia episode during LTV prophylaxis, whereas 50/66 (75.8%) patients developed at least one positive HCMV DNA event after LTV prophylaxis. Of note, 25 of them (50%) experienced a clinically significant HCMV infection. The median HCMV-specific T-cell response measured against HCMV lysate but not against pp65 peptide pool was lower in patients who developed HCMV clinically significant infection after prophylaxis. A ROC analysis revealed that the level of 0.04 HCMV-specific T cells/µl should be used as cut-off for development of clinically significant HCMV reactivation after prophylaxis. Assessment of HCMV-specific immunity upon discontinuation of universal prophylaxis with LTV should be considered as a method for identification of patients at risk for clinically significant HCMV infection.

MRNA vaccination boosts S-specific T cell memory and promotes expansion of CD45RAint TEMRA-like CD8+ T cells in COVID-19 recovered individuals

SARS-CoV-2 infection and mRNA vaccination both elicit spike (S)-specific Tcell responses. To analyze how Tcell memory from prior infection influences Tcell responses to vaccination, we evaluated functional Tcell responses in naive and previously infected vaccine recipients. Pre-vaccine S-specific responses are predictive of subsequent CD8+ Tcell vaccine-response magnitudes. Comparing baseline with post-vaccination TCRβ repertoires, we observed large clonotypic expansions correlated with the frequency of spike-specific Tcells. Epitope mapping the largest CD8+ Tcell responses confirms that an HLA-A∗03:01 epitope was highly immunodominant. Peptide-MHC tetramer staining together with mass cytometry and single-cell sequencing permit detailed phenotyping and clonotypic tracking of these S-specific CD8+ Tcells. Our results demonstrate that infection-induced S-specific CD8+ Tcell memory plays a significant role in shaping the magnitude and clonal composition of the circulating Tcell repertoire after vaccination, with mRNA vaccination promoting CD8+ memory Tcells to a TEMRA-like phenotype.

Co-delivery of a trimeric spike DNA and protein vaccine with aluminum hydroxide enhanced Th1-dominant humoral and cellular immunity against SARS-CoV-2.

Protein subunit vaccines have been used as prophylactic vaccines for a long time. The well-established properties of these vaccines make them the first choice for the coronavirus disease 2019 (COVID-19) outbreak. However, it is not easy to develop a protein vaccine that induces cytotoxic T lymphocyte responses and requires a longer time for manufacturing, which limits the usage of this vaccine type. Here, we report the combination of a recombinant spike (S)-trimer protein with a DNA vaccine-encoded S protein as a novel COVID-19 vaccine. The recombinant S protein was formulated with different adjuvants and mixed with the DNA plasmid before injection. We found that the recombinant S protein formulated with the adjuvant aluminum hydroxide and mixed with the DNA plasmid could enhance antigen-specific antibody titers, neutralizing antibody titers. We further evaluated the IgG2a/IgG1 isotype and cytokine profiles of the specific boosted T-cell response, which indicated that the combined vaccine induced a T-helper 1 cell-biased immune response. Immunized hamsters were challenged with severe acute respiratory syndrome coronavirus 2, and the body weight of the hamsters that received the recombinant S protein with aluminum hydroxide and/or the DNA plasmid was not reduced. Alternatively, those that received control or only the DNA plasmid immunization were reduced. Interestingly, after the third day of the viral load in the lungs, the viral challenge could not be detected in hamsters immunized with the recombinant S protein in aluminum hydroxide mixed with DNA(tissue culture infectious dose < 10). The viral load in the lungs was 109 , 106 , and 107 for the phosphate-buffered saline, protein in aluminum hydroxide, and DNA-only immunizations, respectively. These results indicated that antiviral mechanisms neutralizing antibodies play important roles. Furthermore, we found that the combination of protein and DNA vaccination could induce relatively strong CD8+ T-cell responses. In summary, the protein subunit vaccine combined with a DNA vaccine could induce strong CD8+ T-cell responses to increase antiviral immunity for disease control.

Cladribine Tablets Mode of Action, Learning from the Pandemic: A Narrative Review.

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system, characterized by chronic, inflammatory, demyelinating, and neurodegenerative processes. MS management relies on disease-modifying drugs that suppress/modulate the immune system. Cladribine tablets (CladT) have been approved by different health authorities for patients with various forms of relapsing MS. The drug has been demonstrated to deplete CD4+ and CD8+ T-cells, with a higher effect described in the former, and to decrease total CD19+, CD20+, and naive B-cell counts. COVID-19 is expected to become endemic, suggesting its potential infection risk for immuno-compromised patients, including MS patients treated with disease-modifying drugs. We report here the available data on disease-modifying drug-treated-MS patients and COVID-19 infection and vaccination, with a focus on CladT. MS patients treated with CladT are not at higher risk of developing severe COVID-19. While anti-SARS-CoV-2 vaccination is recommended in all MS patients with guidelines addressing vaccination timing according to the different disease-modifying drugs, no vaccination timing restrictions seem to be necessary for cladribine, based on its mechanism of action and available evidence. Published data suggest that CladT treatment does not impact the production of anti-SARS-CoV-2 antibodies after COVID-19 vaccination, possibly due to its relative sparing effect on naïve B-cells and the rapid B-cell reconstitution following treatment. Slightly lower specific T-cell responses are likely not impacting the risk of breakthrough COVID-19. It could be stated that cladribine's transient effect on innate immune cells likely contributes to maintaining an adequate first line of defense against the SARS-CoV-2 virus.

T-cell immunity against SARS-CoV-2 measured by an interferon-γ release assay is strongly associated with patient outcomes in vaccinated persons hospitalized with Delta or Omicron variants.

We measured T-cell and antibody responses to SARS-CoV-2 in vaccinated patients hospitalized for COVID-19, and explored their potential value to predict outcomes. Prospective, longitudinal study including vaccinated patients hospitalized with Delta and Omicron SARS-CoV-2 variants. TrimericS-IgG antibodies and SARS-CoV-2 T-cell response were measured using a specific quantitative interferon-γ release assay (IGRA). Primary outcome was all-cause 28-day mortality or need for ICU admission. Cox models were used to assess associations with outcomes. 158 (87.3%) of 181 individuals had detectable SARS-CoV-2 antibodies, 92 (50.8%) showed SARS-CoV-2 specific T-cell responses, and 87 (48.1%) had both responses. Patients who died within 28 days or needed ICU were less likely to have both unspecific and specific T-cell responses in IGRA. In adjusted analyses, for the entire cohort, having both T-cell and antibody responses at admission (aHR:0.16; 95%CI, 0.05-0.58) and Omicron variant (aHR:0.38; 95%CI, 0.17-0.87) reduced the hazard of 28-day mortality or ICU, whereas higher Charlson comorbidity index (aHR:1.27; 95%CI, 1.07-1.51) and lower SpO2/FIO2 (aHR:2.36; 95%CI, 1.51-3.67) increased the risk. Pre-existing immunity against SARS-CoV-2 is strongly associated with patient outcomes in vaccinated individuals requiring hospital admission for COVID-19. Persons showing both T-cell and antibody responses have the lowest risk of severe outcomes.

Influence of SARS-CoV-2 mRNA Vaccine Booster among Cancer Patients on Active Treatment Previously Immunized with Inactivated versus mRNA Vaccines: A Prospective Cohort Study.

Cancer patients on chemotherapy have a lower immune response to SARS-CoV-2 vaccines. Therefore, through a prospective cohort study of patients with solid tumors receiving chemotherapy, we aimed to determine the immunogenicity of an mRNA vaccine booster (BNT162b2) among patients previously immunized with an inactivated (CoronaVac) or homologous (BNT162b2) SARS-CoV-2 vaccine. The primary outcome was the proportion of patients with anti-SARS-CoV-2 neutralizing antibody (NAb) seropositivity at 8-12 weeks post-booster. The secondary end points included IgG antibody (TAb) seropositivity and specific T-cell responses. A total of 109 patients were included. Eighty-four (77%) had heterologous vaccine schedules (two doses of CoronaVac followed by the BNT162b2 booster) and twenty-five had (23%) homologous vaccine schedules (three doses of BNT162b2). IgG antibody positivity for the homologous and heterologous regimen were 100% and 96% (p = 0.338), whereas NAb positivity reached 100% and 92% (p = 0.13), respectively. Absolute NAb positivity and Tab levels were associated with the homologous schedule (with a beta coefficient of 0.26 with p = 0.027 and a geometric mean ratio 1.41 with p = 0.044, respectively). Both the homologous and heterologous vaccine regimens elicited a strong humoral and cellular response after the BNT162b2 booster. The homologous regimen was associated with higher NAb positivity and Tab levels after adjusting for relevant covariates.

Synthetic Self-Adjuvanted Lipopeptide Vaccines Conferred Protection against Helicobacter pylori Infection.

Helicobacter pylori(H. pylori) colonizes the stomach epithelium of half the world's population and is responsible for various digestive diseases and even stomach cancer. Vaccine-mediated protection against H. pylori infection depends primarily on the specific mucosal and T-cell responses. In this study, the synthetic lipopeptide vaccines, Hp4 (Pam2 Cys modified UreB T-cell epitope) and Hp10 (Pam2 Cys modified CagA T/B cell combined epitope), not only induce the bone marrow derived dendritic cells (BMDCs) maturation by activating a variety of pattern-recognition receptors (PRRs) such as Toll-like receptor (TLR), Nod-like receptor (NLR), and retinoic acid-inducing gene (RIG) I-like receptor (RLR), and but also stimulate BMDCs to secret cytokines that have the potential to modulate T-cell activation and differentiation. Although intranasal immunization with Hp4 or Hp10 elicits robust epitope-specific T-cell responses in mice, only Hp10 confers protection against H. pylori infection, possibly due to the fact that Hp10 also induces substantial specific sIgA response at mucosal sites. Interestingly, Hp4 elevates the protective response against H. pylori infection of Hp10 when administrated in combination, characterized by better protective effect and enhanced specific T-cell and mucosal antibody responses. The results suggest that synthetic lipopeptide vaccines based on the epitopes derived from the protective antigens are promising candidates for protection against H. pylori infection.

#4938 PATIENTS RECEIVING HEMODIALYSIS MAINTAIN STRONGER SARS-COV-2 IMMUNITY AFTER DISEASE RATHER THAN VACCINATION

Abstract Background and Aims We aimed to compare the dynamics of humoral and cellular immunity caused by natural COVID-19 or vaccination against of SARS-CoV-2 with Gam-COVID-Vac (Sputnik V) vaccine in patients, receiving maintenance hemodialysis (HD). Method Data were extracted from two prospective cohort studies which had investigated the long-term immune responses after SARS-CoV-2 infection (NCT 04633915) or vaccination (NCT 04805632) in patients receiving HD compared with those in healthy individuals. The group of patients after natural COVID-19 (n = 24) had confirmed history of disease, nobody of them received vaccination before and during the study period. Levels of specific IgG and T-cells were quantified in them at 2.5 and 6 months from disease onset. The group of vaccinated patients (n = 23) had been vaccinated twice with Gam-COVID-Vac vaccine and had no prior history of confirmed COVID-19. Levels of anti-SARS-CoV-2-specific IgG and T-cells were quantified at 1 month and 6 months from the second vaccine shot. IgG levels were determined using a semi-quantitative ELISA (Euroimmun, Germany) and converted to Binding Antibody Units (BAU/ml) according to the WHO International Standard. Specific T-cell responses (CD4+ and CD8+ cytotoxic T-lymphocytes) were evaluated using the TIGRA-test® (Generium, Russia). Only spike-specific T-spots were used for the analyses. Results Seropositivity rate declined over the course of the study among vaccinated patients (from 91% to 51%), however, all patients after natural COVID-19 remained seropositive over the study period. Thus, seropositivity rate at 6 months was greater in disease group: RR = 1.91 [95%CI: 1.4–3.1] (reciprocal of RR = 0.52 [95% CI: 0.32–0.72]), P = 0.0004. In both groups, IgG levels decreased over time, but antibodies disappeared more rapidly in vaccinated HD patients (analysis of variance p = 0.0374 for the “time × group” interaction) – Figure 1 (left). T-test reached positivity in 73% of vaccinated patients and 93% of patients after natural COVID-19 at the first timepoint. At the end of the study, T-test remained positive in 67% and 91% of the patients in both groups, respectively. Risk of T-test positivity rate at 6 months did not differ between groups (P = 0.133). T-spot counts remained stable over time in vaccinated patients, while tended to increase in patients after COVID-19 to the end of the follow-up. Differences in dynamics in these two groups were statistically significant (analysis of variance p = 0.0293 for the “time × group” interaction) – Fig.1 (right). Conclusion Patients receiving HD maintain more sustainable humoral immune responses after natural COVID-19 disease than after complete vaccination with Gam-COVID-Vac vaccine. Specific SARS-CoV-2 IgG antibodies declines faster in vaccinated patients than in patients after COVID-19 over 6-month period. Cellular immunity remains stable in both groups increasing by the 6-months period among those who had natural COVID-19.

Human Ad19a/64 HERV-W Vaccines Uncover Immunosuppression Domain-Dependent T-Cell Response Differences in Inbred Mice.

Expression of human endogenous retrovirus type W (HERV-W) has been linked to cancer, making HERV-W antigens potential targets for therapeutic cancer vaccines. In a previous study, we effectively treated established tumours in mice by using adenoviral-vectored vaccines targeting the murine endogenous retrovirus envelope and group-specific antigen (Gag) of melanoma-associated retrovirus (MelARV) in combination with anti-PD-1. To break the immunological tolerance to MelARV, we mutated the immunosuppressive domain (ISD) of the MelARV envelope. However, reports on the immunogenicity of the HERV-W envelope, Syncytin-1, and its ISD are conflicting. To identify the most effective HERV-W cancer vaccine candidate, we evaluated the immunogenicity of vaccines encoding either the wild-type or mutated HERV-W envelope ISD in vitro and in vivo. Here, we show that the wild-type HERV-W vaccine generated higher activation of murine antigen-presenting cells and higher specific T-cell responses than the ISD-mutated counterpart. We also found that the wild-type HERV-W vaccine was sufficient to increase the probability of survival in mice subjected to HERV-W envelope-expressing tumours compared to a control vaccine. These findings provide the foundation for developing a therapeutic cancer vaccine targeting HERV-W-positive cancers in humans.

Assessment of mRNA Vaccine Immunogenicity in Solid Organ Transplant Recipients.

Background and Objectives: Solid organ transplant (SOT) recipients have a higher risk of suffering from severe Coronavirus (COVID-19) compared to the general population. Studies have shown impaired immunogenicity of mRNA vaccines in this high-risk population; thus, SOT recipients have been prioritized globally for primary and booster doses. Materials and Methods: We analyzed 144 SOT recipients who had previously received two doses of BNT162b2 or mRNA1273 vaccine, and who were subsequently vaccinated with a booster dose of the mRNA1273 vaccine. Humoral and cellular immune responses were measured 1 and 3 months after the second dose, and 1 month after the third dose. Results: One month after the second dose, 33.6% (45/134) of patients displayed a positive antibody response with a median (25th, 75th) antibody titer of 9 (7, 161) AU/mL. Three months after the second dose, 41.8% (56/134) tested positive with a median (25th, 75th) antibody titer of 18 (7, 251) AU/mL. After the booster dose, the seropositivity rate increased to 69.4% (93/134), with a median (25th, 75th) titer of 966 (10, 8027) AU/mL. The specific SARS-CoV-2 T-cell response was assessed in 44 randomly selected recipients 3 months after the second dose, and 11.4% (5/44) of them had a positive response. Following the third dose, 42% (21/50) tested positive. Side effects after the third dose were mild, with pain at the injection site being the most frequent adverse effect, reported by 73.4% of the recipients. Conclusion: Our study shows a mild delayed increase in antibody titer, three months after primary vaccination compared to one month after. It also shows a robust augmentation of humoral and specific T-cell responses after the booster dose, as well as the safety and tolerability of the mRNA vaccines in SOT recipients.

The presence of senescent peripheral T-cells is negatively correlated to COVID-19 vaccine-induced immunity in cancer patients under 70 years of age.

Cancer patients are at risk of severe COVID-19 infection, and vaccination is recommended. Nevertheless, we observe a failure of COVID-19 vaccines in this vulnerable population. We hypothesize that senescent peripheral T-cells alter COVID-19 vaccine-induced immunity. We performed a monocentric prospective study and enrolled cancer patients and healthy donors before the COVID-19 vaccination. The primary objective was to assess the association of peripheral senescent T-cells (CD28-CD57+KLRG1+) with COVID-19 vaccine-induced immunity. Eighty cancer patients have been included, with serological and specific T-cell responses evaluated before and at 3 months post-vaccination. Age ≥ 70 years was the principal clinical factor negatively influencing the serological (p=0.035) and specific SARS-CoV-2 T-cell responses (p=0.047). The presence of senescent T-cells was correlated to lower serological (p=0.049) and specific T-cell responses (p=0.009). Our results sustained the definition of a specific cut-off for senescence immune phenotype (SIP) (≥ 5% of CD4 and ≥ 39.5% of CD8 T-cells), which was correlated to a lower serological response induced by COVID-19 vaccination for CD4 and CD8 SIPhigh (p=0.039 and p=0.049 respectively). While CD4 SIP level had no impact on COVID-19 vaccine efficacy in elderly patients, our results unraveled a possible predictive role for CD4 SIPhigh T-cell levels in younger cancer patients. Elderly cancer patients have a poor serological response to vaccination; specific strategies are needed in this population. Also, the presence of a CD4 SIPhigh affects the serological response in younger patients and seems to be a potential biomarker of no vaccinal response.

MERS-CoV‒Specific T-Cell Responses in Camels after Single MVA-MERS-S Vaccination.

We developed an ELISPOT assay for evaluating Middle East respiratory syndrome coronavirus (MERS-CoV)‒specific T-cell responses in dromedary camels. After single modified vaccinia virus Ankara-MERS-S vaccination, seropositive camels showed increased levels of MERS-CoV‒specific T cells and antibodies, indicating suitability of camel vaccinations in disease-endemic areas as a promising approach to control infection.

Evaluation of a commercial interferon-γ release assay for the detection of SARS-CoV-2 T-cell response after vaccination

ObjectiveEvidence regarding the role of cellular immunity in protecting against COVID-19 is emerging. To better assess immune status, simple and robust assays measuring specific T-cell responses associated with humoral responses are needed. We aimed to evaluate the Quan-T-Cell SARS-CoV-2 test for measuring cellular immune responses in vaccinated healthy and immunosuppressed subjects. MethodsT-cell responses were assessed in healthy vaccinated and unvaccinated and unexposed healthcare workers to determine the sensitivity and specificity of the EUROIMMUN SARS-CoV-2 Quan-T-Cell IGRA test performed on vaccinated kidney transplant recipients (KTRs). ResultsThe EUROIMMUN SARS-CoV-2 Quan-T-Cell IGRA test showed good sensitivity (87.2%) and specificity (92.3%) at the calculated 147 mIU/mL cutoff, with an 88.33% accuracy. In KTRs, specific cellular immunity was lower than the antibody response; however, those with a positive IGRA result produced as much IFN-γ as healthy individuals. ConclusionsThe EUROIMMUN SARS-CoV-2 Quan-T-Cell IGRA test showed good sensitivity and specificity for the detection of specific T-cell responses against the SARS-CoV-2 spike protein. These results present an additional tool for better management of COVID-19, especially in vulnerable populations.