Pre-existing CD8 Research Articles

A viral vaccine design harnessing prior BCG immunization confers protection against Ebola virus.

Previous studies have demonstrated the efficacy and feasibility of an anti-viral vaccine strategy that takes advantage of pre-existing CD4+ helper T (Th) cells induced by Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccination. This strategy uses immunization with recombinant fusion proteins comprised of a cell surface expressed viral antigen, such as a viral envelope glycoprotein, engineered to contain well-defined BCG Th cell epitopes, thus rapidly recruiting Th cells induced by prior BCG vaccination to provide intrastructural help to virus-specific B cells. In the current study, we show that Th cells induced by BCG were localized predominantly outside of germinal centers and promoted antibody class switching to isotypes characterized by strong Fc receptor interactions and effector functions. Furthermore, BCG vaccination also upregulated FcγR expression to potentially maximize antibody-dependent effector activities. Using a mouse model of Ebola virus (EBOV) infection, this vaccine strategy provided sustained antibody levels with strong IgG2c bias and protection against lethal challenge. This general approach can be easily adapted to other viruses, and may be a rapid and effective method of immunization against emerging pandemics in populations that routinely receive BCG vaccination.

A viral vaccine design harnessing prior BCG immunization confers protection against Ebola virus.

Previous studies have demonstrated the efficacy and feasibility of an anti-viral vaccine strategy that takes advantage of pre-existing CD4 + helper T (Th) cells induced by Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccination. This strategy uses immunization with recombinant fusion proteins comprised of a cell surface expressed viral antigen, such as a viral envelope glycoprotein, engineered to contain well-defined BCG Th cell epitopes, thus rapidly recruiting Th cells induced by prior BCG vaccination to provide intrastructural help to virus-specific B cells. In the current study, we show that Th cells induced by BCG were localized predominantly outside of germinal centers and promoted antibody class switching to isotypes characterized by strong Fc receptor interactions and effector functions. Furthermore, BCG vaccination also upregulated FcγR expression to potentially maximize antibody-dependent effector activities. Using a mouse model of Ebola virus (EBOV) infection, this vaccine strategy provided sustained antibody levels with strong IgG2c bias and protection against lethal challenge. This general approach can be easily adapted to other viruses, and may be a rapid and effective method of immunization against emerging pandemics in populations that routinely receive BCG vaccination.

Modulation of innate immune response to mRNA vaccination after SARS-CoV-2 infection or sequential vaccination in humans.

mRNA vaccines are likely to become widely used for the prevention of infectious diseases in the future. Nevertheless, a notable gap exists in mechanistic data, particularly concerning the potential effects of sequential mRNA immunization or preexisting immunity on the early innate immune response triggered by vaccination. In this study, healthy adults, with or without documented prior SARS-CoV-2 infection, were vaccinated with the BNT162b2/Comirnaty mRNA vaccine. Prior infection conferred significantly stronger induction of proinflammatory and type I IFN-related gene signatures, serum cytokines, and monocyte expansion after the prime vaccination. The response to the second vaccination further increased the magnitude of the early innate response in both study groups. The third vaccination did not further increase vaccine-induced inflammation. In vitro stimulation of PBMCs with TLR ligands showed no difference in cytokine responses between groups, or before or after prime vaccination, indicating absence of a trained immunity effect. We observed that levels of preexisting antigen-specific CD4 T cells, antibody, and memory B cells correlated with elements of the early innate response to the first vaccination. Our data thereby indicate that preexisting memory formed by infection may augment the innate immune activation induced by mRNA vaccines.

MLXIPL associated with tumor-infiltrating CD8+ T cells is involved in poor prostate cancer prognosis.

Within tumor microenvironment, the presence of preexisting antitumor CD8+ T Q7 cells have been shown to be associated with a favorable prognosis in most solid cancers. However, in the case of prostate cancer (PCa), they have been linked to a negative impact on prognosis. To gain a deeper understanding of the contribution of infiltrating CD8+ T cells to poor prognosis in PCa, the infiltration levelsof CD8+ T cells were estimated using the TCGA PRAD (The Cancer Genome Atlas Prostate Adenocarcinoma dataset) and MSKCC (Memorial Sloan Kettering Cancer Center) cohorts. Bioinformatic analyses revealed that CD8+ T cells likely influence PCa prognosis through increased expression of immune checkpoint molecules and enhanced recruitment of regulatory T cells. The MLXIPL was identified as the gene expressed in response to CD8+ T cell infiltration and was found to be associated with PCa prognosis. The prognostic role of MLXIPL was examined in two cohorts: TCGA PRAD (p = 2.3E-02) and the MSKCC cohort (p = 1.6E-02). Subsequently, MLXIPL was confirmed to be associated with an unfavorable prognosis in PCa, as evidenced by an independent cohort study (hazard ratio [HR] = 2.57, 95% CI: 1.42- 4.65, p = 1.76E-03). In summary, the findings suggested that MLXIPL related to tumor-infiltrating CD8+ T cells facilitated a poor prognosis in PCa.

Abstract LB117: Virus-inspired Particles (ViPs) harnessing cytomegalovirus immune memory for local and systemic cancer immunotherapy

Abstract VerImmune is pioneering a First-in-Class treatment known as “Anti-tumor Immune Redirection” (AIR). This approach repurposes a patient’s pre-existing anti-viral or childhood vaccine immunity towards tumor cells for targeted destruction. VerImmune’s lead product, VERI-101, leverages pre-existing CD8+ T-cell immune memory acquired from past human cytomegalovirus (HCMV) infections. VERI-101 consists of VerImmune’s proprietary platform technology known as ViPs (Virus-inspired Particles) that are conjugated on their surface with a CD8+ T cell viral peptide antigen. ViPs are based on a modified mouse papillomavirus capsid protein of which 60 copies self-assemble into a 20-30nm T=1 icosahedral structure. In the case of VERI-101, the ViP is conjugated with an HLA-A*0201 restricted peptide epitope (NLVPMVATV, [NLV]), derived from the CMV pp65 antigen with an upstream furin protease cleavage site. The mechanism of action of AIR-ViPs including VERI-101 has been previously presented and involves three steps. Briefly, (1) VERI-101 targets the surface of the tumor cells and (2) enables the presentation of the CMV viral epitopes on their surface MHC, together (3) stimulating a recall of the pre-existing CMV memory response to attack the cancer cells (Dorrier et al., 2023 AACR). Here, we sought to study the in vivo anti-tumor efficacy of AIR-ViPs via both intra-tumoral and systemic treatment routes in two murine tumor models with pre-existing murine CMV (MCMV) immunity: (1) MC38 subcutaneous tumors for local and (2) B16.F10 lung metastasis for systemic treatments. As human CMV is species-specific, instead of VERI-101, a surrogate product, VERI-003 which redirects MCMV immunity, was tested as a single agent or in combination with anti-PD-1 in these tumor models. Our intra-tumoral studies with VERI-003 alone showed a dose-dependent anti-tumor effect (from 5 to 100ug) compared to no treatment controls. Surprisingly, no dose dependence was observed across the same three dose levels when combined with anti-PD-1, although significantly better anti-tumor effects occurred leading to complete tumor clearances in 50% of mice. Statistically significant prolonged survival was observed in most treated groups compared to controls. Our systemic studies with VERI-003 were consistent with our intratumoral studies in showing statistically significant single agent anti-tumor efficacy against B16.F10 lung metastases compared to no treatment. Anti-tumor effects of anti-PD-1 and combination were also observed. Additional studies are on-going to assess dose dependence and analysis of PK/PD effects. Taken together, our initial in vivo results demonstrate the tumor antigen-agnostic therapeutic potential of AIR and our AIR-ViP technology as a novel class of immuno-therapeutic drugs that could be used either as a monotherapy or in combination with checkpoint inhibitors. Citation Format: Cayce Dorrier, Felagot Abebe, Olivia Pak, Emily De-Bodene, Joshua Wang. Virus-inspired Particles (ViPs) harnessing cytomegalovirus immune memory for local and systemic cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB117.

Abstract 4991: Radiotherapy-induced immunological and therapeutic response depends on stem-like TCF-1+PD-1+CD8+ T-cells

Abstract Radiotherapy is a frequently used treatment for cancer. Recent data, including ours, showed that radiotherapy promotes an inflammatory response in the tumor that supports tumor-specific immunity, and in fact, the efficacy of radiotherapy in pre-clinical models depends on CD8+ T-cells. According to our preliminary data, the response to radiotherapy is independent of de novo recruited CD8+ T-cells, suggesting that radiation drives differentiation and proliferation of preexisting intratumoral CD8+ T-cells. Intratumoral CD8+ T-cells are heterogeneous concerning phenotype and function. Under conditions of chronic stimulation by antigen, a subset of CD8+ T-cells expressing PD-1 and the transcription factor TCF-1 was described. These so-called stem-like CD8+ T-cells, which give rise to effector cells, were shown to be essential for the clinical response to PD-1 blockade. How radiotherapy influences the different CD8+ T-cell subsets in the tumor microenvironment has not been comprehensively investigated. We propose that the efficacy of radiotherapy depends on the presence of stem-like CD8+ T-cells, presumably by giving rise to effector cells. To address this, we selectively depleted TCF-1+ cells from tumor-bearing mice immediately before radiotherapy. Subsequently, we correlated tumor regression with the immunological response using single-cell analyses of intratumoral CD8+ T-cells. In the absence of TCF-1+ cells, we found a reduced efficacy and reduced number of intratumoral effector cells after radiotherapy. We currently analyze our single-cell RNA-sequencing data and expect to discover novel radiotherapy-induced pathways in CD8+ T-cells that contribute to therapeutic efficacy. Citation Format: Hakan Köksal, Michael Herbst, Nicola Marti, Maries van den Broek. Radiotherapy-induced immunological and therapeutic response depends on stem-like TCF-1+PD-1+CD8+ T-cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4991.

Response to tumor-infiltrating lymphocyte adoptive therapy is associated with preexisting CD8+ T-myeloid cell networks in melanoma.

Adoptive cell therapy (ACT) using ex vivo-expanded tumor-infiltrating lymphocytes (TILs) can eliminate or shrink metastatic melanoma, but its long-term efficacy remains limited to a fraction of patients. Using longitudinal samples from 13 patients with metastatic melanoma treated with TIL-ACT in a phase 1 clinical study, we interrogated cellular states within the tumor microenvironment (TME) and their interactions. We performed bulk and single-cell RNA sequencing, whole-exome sequencing, and spatial proteomic analyses in pre- and post-ACT tumor tissues, finding that ACT responders exhibited higher basal tumor cell-intrinsic immunogenicity and mutational burden. Compared with nonresponders, CD8+ TILs exhibited increased cytotoxicity, exhaustion, and costimulation, whereas myeloid cells had increased type I interferon signaling in responders. Cell-cell interaction prediction analyses corroborated by spatial neighborhood analyses revealed that responders had rich baseline intratumoral and stromal tumor-reactive T cell networks with activated myeloid populations. Successful TIL-ACT therapy further reprogrammed the myeloid compartment and increased TIL-myeloid networks. Our systematic target discovery study identifies potential T-myeloid cell network-based biomarkers that could improve patient selection and guide the design of ACT clinical trials.

Long-lasting humoral and cellular memory immunity to vaccinia virus Tiantan provides pre-existing immunity against mpox virus in Chinese population

Investigating immune memory to vaccinia virus and pre-existing immunity to mpox virus (MPXV) among the population is crucial for the global response to this ongoing mpox epidemic. Blood was sampled from vaccinees inoculated with vaccinia virus Tiantan (VTT) strain born before 1981 and unvaccinated control subjects born since 1982. After at least 40 years of the inoculation, 60% or 5% VTT vaccinees possess neutralizing antibodies (NAbs) to VTT or MPXV, with at least 50% having Tcell memory to VTT protein antigens. Notably, 46.7% vaccinees show pre-existing Tcell responses to MPXV. Broad pre-existing CD8+ Tcell reactivities to MPXV are detected not only against conserved epitopes but also against variant epitopes between VTT and MPXV. Persistent NAbs and Tcell memory to VTT among vaccinees, along with pre-existing Tcells to MPXV among both vaccinees and the unvaccinated population, indicate a particular immune barrier to mpox.

Intranasal immunization with an RBD-hemagglutinin fusion protein harnesses preexisting immunity to enhance antigen-specific responses.

Intranasal vaccines are anticipated to be powerful tools for combating many infectious diseases, including SARS-CoV-2, because they induce not only systemic immunity but also mucosal immunity at the site of initial infection. However, they are generally inefficient in inducing an antigen-specific immune response without adjuvants. Here, we developed an adjuvant-free intranasal vaccine platform that utilizes the preexisting immunity induced by previous infection or vaccination to enhance vaccine effectiveness. We made RBD-HA, a fusion of the receptor-binding domain (RBD) of spike derived from SARS-CoV-2 as a vaccine target with HA derived from influenza A virus (IAV) as a carrier protein. Intranasal immunization of previously IAV-infected mice with RBD-HA without an adjuvant elicited robust production of RBD-specific systemic IgG and mucosal IgA by utilizing both HA-specific preexisting IgG and CD4+ T cells. Consequently, the mice were efficiently protected from SARS-CoV-2 infection. Additionally, we demonstrated the high versatility of this intranasal vaccine platform by assessing various vaccine antigens and preexisting immunity associated with a variety of infectious diseases. The results of this study suggest the promising potential of this intranasal vaccine platform to address problems associated with intranasal vaccines.

Both Humoral and Cellular Immunity Limit the Ability of Live Attenuated Influenza Vaccines to Promote T Cell Responses.

One potential advantage of live attenuated influenza vaccines (LAIVs) is their ability to establish both virus-specific Ab and tissue-resident memory T cells (TRM) in the respiratory mucosa. However, it is hypothesized that pre-existing immunity from past infections and/or immunizations prevents LAIV from boosting or generating de novo CD8+ T cell responses. To determine whether we can overcome this limitation, we generated a series of drifted influenza A/PR8 LAIVs with successive mutations in the hemagglutinin protein, allowing for increasing levels of escape from pre-existing Ab. We also inserted a CD8+ T cell epitope from the Sendai virus nucleoprotein (NP) to assess both generation of a de novo T cell response and boosting of pre-existing influenza-specific CD8+ T cells following LAIV immunization. Increasing the level of escape from Ab enabled boosting of pre-existing TRM, but we were unable to generate de novo Sendai virus NP+ CD8+ TRM following LAIV immunization in PR8 influenza-immune mice, even with LAIV strains that can fully escape pre-existing Ab. As these data suggested a role for cell-mediated immunity in limiting LAIV efficacy, we investigated several scenarios to assess the impact of pre-existing LAIV-specific TRM in the upper and lower respiratory tract. Ultimately, we found that deletion of the immunodominant influenza NP366-374 epitope allowed for sufficient escape from cellular immunity to establish de novo CD8+ TRM. When combined, these studies demonstrate that both pre-existing humoral and cellular immunity can limit the effectiveness of LAIV, which is an important consideration for future design of vaccine vectors against respiratory pathogens.

Biomarkers of Pathologic Complete Response to Neoadjuvant Immunotherapy in Mismatch Repair-Deficient Colorectal Cancer.

Immune checkpoint inhibitors (ICI) have become the standard of care for patients with mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) colorectal cancer. However, biomarkers of response to ICI are still lacking. Forty-two patients with dMMR colorectal cancer treated with neoadjuvant PD-1 blockade were prospectively enrolled. To identify biomarkers of pathologic complete response (pCR) to neoadjuvant therapy, we analyzed genomic and transcriptomic profiles based on next-generation sequencing, and immune cell density based on multiplex immunofluorescence (mIF) staining. An integrated analysis of single-cell RNA sequencing from our previous study and GSE178341, as well as mIF was performed to further explore the significance of the tumor microenvironment (TME) on pCR response. The tumor mutation burden of both tumor tissue and plasma blood samples was comparable between the pCR and non-pCR groups, while HLA-DQA1 and HLA-DQB1 were significantly overexpressed in the pCR group. Gene signature enrichment analysis showed that pathways including T-cell receptor pathway, antigen presentation pathway were significantly enriched in the pCR group. In addition, higher pre-existing CD8+ T-cell density was associated with pCR response (767.47 per.mm2 vs. 326.64 per.mm2, P = 0.013 Wilcoxon test). Further integrated analysis showed that CD8+ T cells with low PD-1 expression (PD-1lo CD8+ T cells) expressing high levels of TRGC2, CD160, and KLRB1 and low levels of proliferated and exhausted genes were significantly associated with pCR response. Immune-associated transcriptomic features, particularly CD8+ T cells were associated with pCR response to ICI in dMMR colorectal cancer. Heterogeneity of TME within dMMR colorectal cancer may help to discriminate patients with complete response to neoadjuvant ICI.

Designing Anti-Viral Vaccines that Harness Intrastructural Help from Prior BCG Vaccination.

Vaccines are among the most effective tools for combatting the impact and spread of infectious diseases. However, the effectiveness of a vaccine can be diminished by vaccine inequality, particularly during severe outbreaks of infectious diseases in resource-poor areas. As seen in many developing countries that lack adequate healthcare infrastructure and economic resources, the acquisition and distribution of potentially life-saving vaccines may be limited, leading to prolonged suffering and increased deaths. To improve vaccine equity, vaccine design must take into consideration the logistics needed to implement a successful vaccination drive, particularly among the most vulnerable populations. In the manuscript titled "Exploiting Pre-Existing CD4+ T Cell Help from Bacille Calmette-Guérin Vaccination to Improve Antiviral Antibody Responses" published in the Journal of Immunology, the authors designed a recombinant subunit vaccine against the Ebola virus (EBOV) glycoprotein that can harness the pre-existing T helper cells from prior BCG vaccination. As a recombinant subunit vaccine adjuvanted with alum, this approach has many features that make it well suited for the design of vaccines for developing nations, such as relative ease of production, scalability, and distribution. In addition, the high prevalence of BCG immunization and natural immunity to mycobacteria in many regions of the world endow such vaccines with features that should increase potency and efficacy among populations residing in such regions. As a result of using the helper activity of pre-existing BCG-specific Th cells to drive antibody responses, a lower vaccine dose is needed, which is a major advantage for vaccine manufacture. Furthermore, the BCG-specific Th cells also stimulate immunoglobulin class switching to IgG isotypes that have strong affinities for activating Fc-gamma receptors (FcγRs). Taken together, we propose that the design of subunit vaccines with intrastructural help from BCG-specific Th cells can improve protection against viral infection and represents a vaccine design that can be generally adapted to other emerging viral pathogens for the control and prevention of infection in many developing countries.

Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection.

Congenital cytomegalovirus (cCMV) is the leading infectious cause of neurologic defects in newborns with particularly severe sequelae in the setting of primary CMV infection in the first trimester of pregnancy. The majority of cCMV cases worldwide occur after non-primary infection in CMV-seropositive women; yet the extent to which pre-existing natural CMV-specific immunity protects against CMV reinfection or reactivation during pregnancy remains ill-defined. We previously reported on a novel nonhuman primate model of cCMV in rhesus macaques where 100% placental transmission and 83% fetal loss were seen in CD4+ T lymphocyte-depleted rhesus CMV (RhCMV)-seronegative dams after primary RhCMV infection. To investigate the protective effect of preconception maternal immunity, we performed reinfection studies in CD4+ T lymphocyte-depleted RhCMV-seropositive dams inoculated in late first / early second trimester gestation with RhCMV strains 180.92 (n = 2), or RhCMV UCD52 and FL-RhCMVΔRh13.1/SIVgag, a wild-type-like RhCMV clone with SIVgag inserted as an immunological marker, administered separately (n = 3). An early transient increase in circulating monocytes followed by boosting of the pre-existing RhCMV-specific CD8+ T lymphocyte and antibody response was observed in the reinfected dams but not in control CD4+ T lymphocyte-depleted dams. Emergence of SIV Gag-specific CD8+ T lymphocyte responses in macaques inoculated with the FL-RhCMVΔRh13.1/SIVgag virus confirmed reinfection. Placental transmission was detected in only one of five reinfected dams and there were no adverse fetal sequelae. Viral whole genome, short-read, deep sequencing analysis confirmed transmission of both reinfection RhCMV strains across the placenta with ~30% corresponding to FL-RhCMVΔRh13.1/SIVgag and ~70% to RhCMV UCD52, consistent with the mixed human CMV infections reported in infants with cCMV. Our data showing reduced placental transmission and absence of fetal loss after non-primary as opposed to primary infection in CD4+ T lymphocyte-depleted dams indicates that preconception maternal CMV-specific CD8+ T lymphocyte and/or humoral immunity can protect against cCMV infection.

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.

Lenvatinib plus anti-PD-1 antibodies as conversion therapy for patients with unresectable intermediate-advanced hepatocellular carcinoma: a single-arm, phase II trial

BackgroundOver 70% of the patients with hepatocellular carcinoma (HCC) are diagnosed at an advanced stage and lose the opportunity for radical surgery. Combination therapy of tyrosine kinase inhibitors (TKIs) and...

Pre-existing CD4 T cell help boosts antibody responses but has limited impact on germinal center, antigen-specific B cell frequencies after influenza infection.

The influenza virus is a persistent burden on global health, with seasonal vaccines providing incomplete protection. CD4+ T cells help shape B cell and antibody responses; however, the selectivity of help and the effect on various antigen-specific B cell populations have not been fully elucidated. Here, we studied the specificity, selectivity, and influence of nucleoprotein (NP) CD4+ T cells on the magnitude and quality of hemagglutinin (HA) and NP-specific B cells and antibody responses. We identified immunodominant peptides and showed that peptide immunization was sufficient to induce CD4+ cells with Th1 and Tfh phenotypes. Surprisingly, while preexisting CD4+ T cells enhanced the influx of total germinal center (GC) B cells in the mediastinal lymph node after infection, this was not reflected by an increase in the frequency of antigen-specific cells within the GC. Furthermore, we demonstrated that NP-specific help was able to accelerate the kinetics and magnitude of the Ab response for NP but not for HA. Overall, our results showed that pre-existing CD4+ T cells provide strong cognate help during immunization or infection to enhance Ab production but not antigen-specific GC or memory B cells.

Structural definition of HLA class II-presented SARS-CoV-2 epitopes reveals a mechanism to escape pre-existing CD4+ T cell immunity

CD4+ Tcells recognize a broad range of peptide epitopes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which contribute to immune memory and limit COVID-19 disease. We demonstrate that the immunogenicity of SARS-CoV-2 peptides, in the context of the model allotype HLA-DR1, does not correlate with their binding affinity to the HLA heterodimer. Analyzing six epitopes, some with very low binding affinity, we solve X-ray crystallographic structures of each bound to HLA-DR1. Further structural definitions reveal the precise molecular impact of viral variant mutations on epitope presentation. Omicron escaped ancestral SARS-CoV-2 immunity to two epitopes through two distinct mechanisms: (1) mutations to TCR-facing epitope positions and (2) a mechanism whereby a single amino acid substitution caused a register shift within the HLA binding groove, completely altering the peptide-HLA structure. This HLA-II-specific paradigm of immune escape highlights how CD4+ Tcell memory is finely poised at the level of peptide-HLA-II presentation.

Peripheral pre-existing cancer-antigen specific T-cell immunity as predictive biomarker for immunotherapy in NSCLC patients.

e20504 Background: Pre-existing Tumor Antigen specific T-cells describe the endogenous adaptive immunity before any treatment that may represent a valuable novel predictive biomarker for ICI treatment. We investigate the potential value of pre-existing cancer-antigen specific CD8+ T-cells as a circulating predictive biomarker. Additionally, we analyze the major differences of known immune-cell phenotypes between Pre-existing positive (PreI+) and Pre-existing negative immunity (PreI-) NSCLC patients. Here, we present the preliminary results of this study. Methods: Blood was collected from 24 patients with NSCLC, stage III PD-L1+, after completion of radical chemoradiation, before initiation of maintenance durvalumab. PBMCs were isolated with Ficoll density gradient centrifugation from patients and 10 healthy donors (HD). PreI was calculated by detecting endogenous IFNg expressing cells with FACS after in-vivo co-cultures of PBMCs with mixes of hTERT, MAGEA1, NY-ESO-1 και Survivin cancer-associated antigens. Immunophenotyping was performed by multi-color flow cytometry using antibodies against CD3, CD4, CD8, CD45RA, CD45RO, CCR7, PD-1, PD-L1 for T-cells. Results: From 24 patients receiving Durvalumab, 10/24 (41.6%) had peptide specific T-cells (PreI + patients), 60% (6/10) had detectable peptide specific T cells for all (4/4) antigens tested. Survival analysis revealed better PFS in PreI+ than PreI – patients (Log-rank = 0.06, median 333.5 and 185 days ) and better OS (p = 0.032, median not reached and 254 days). The levels of CD3CD4PD-1 were higher in patients compared to HD (p = 0.019) but there was not a difference between PreI+ and PreI- patients (p = 0.25). PreI+ patients had significantly higher numbers of CD3CD8PD-1 cells compared to PreI- (p = 0.024) but not CD3CD8PD-L1. Prei+ patients had high numbers of Teff (CD3+CD8+CD45RA+CD45RO-CCR7) compared to both HD (p = 0.0039) and PreI- (p = 0.032). Conclusions: Pre-existing tumor antigen specific immunity before initiation of ICI in NSCLC patients could serve as a good predictive factor of response. The study is ongoing.

Anti-telomerase vaccine in patients with newly diagnosed, unmethylated MGMT glioblastoma: A phase II study.

2005 Background: TERT, a subunit of the telomerase complex, is largely expressed in almost all cancers. Among those cancers, glioblastomas (GBM) harbor the highest incidence of activating mutations within the TERT promoter (over 85% of patients). This high incidence underlies the potential role of TERT in oncogenesis, and points out TERT as a highly relevant tumor target in GBM. UCPvax is a therapeutic vaccine composed of two CD4 helper peptides derived from TERT, combined with the montanide adjuvant. We conducted a phase IIa trial to test the immunogenicity, safety and efficacy of UCPvax in patients with newly diagnosed GBM. Methods: Key inclusion criteria were: histologically confirmed, non-mutated IDH1 glioblastoma, unmethylated MGMT promoter status, previous treatment with concomitant radiotherapy and temozolomide (TMZ), Karnofsky Performance status (KPS) ≥ 70%, steroids < 10mg/ day equivalent prednisone, and lymphocytes count ≥ 0.8 x 109/L. One month after completion of radiation/TMZ, patients started UCPvax vaccinations on days 1, 8, 15, 29, 36 and 43, then every two months until tumor progression, without additional cure of TMZ. Peripheral blood mononuclear cells were collected before treatment, at 1 and 2 months after treatment and, at each vaccination boost. The primary endpoint was an anti-TERT specific CD4 T-cell response measured ex vivo in peripheral blood using IFN-gamma ELISPOT at 2 months. Secondary endpoints included safety, overall survival (OS) and progression-free survival (PFS). Results: Thirty-one adult patients (median age 60-yr old, median KPS 90%) were included in this study. All patients received at least one vaccination, and 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 pts (97%). An epitope spread response against other tumor-associated antigens was detected in 12/25 pts (48%). No severe (grade 3–4) toxicity was attributable to the vaccination. All patients developed local skin reactions (≤ grade 2), 16 patients complained of transient asthenia (≤grade 2), and 13 patients experienced local pain (≤grade 2). 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 (19.3 vs 15.8 months, respectively, p=0.03). Conclusions: UCPVax is highly immunogenic and provides an interesting OS rate in this population of poor prognosis, unmethylated MGMT GBM patients. These data support further clinical studies of UCPvax in GBM patients. Clinical trial information: NCT04280848 .

Pre-existing humoral immunity and CD4+ T cell response correlate with cross-reactivity against SARS-CoV-2 Omicron subvariants after heterologous prime-boost vaccination

BackgroundInformation regarding the heterologous prime-boost COVID vaccination has been fully elucidated. The study aimed to evaluate both humoral, cellular immunity and cross-reactivity against variants after heterologous vaccination. MethodsWe recruited healthcare workers previously primed with Oxford/AstraZeneca ChAdOx1-S vaccines and boosted with Moderna mRNA-1273 vaccine boost to evaluate the immunological response. Assay used: anti-spike RBD antibody, surrogate virus neutralizing antibody and interferon-γ release assay. ResultsAll participants exhibited higher humoral and cellular immune response after the booster regardless of prior antibody level, but those with higher antibody level demonstrated stronger booster response, especially against omicron BA.1 and BA.2 variants. The pre-booster IFN-γ release by CD4+ T cells correlates with post-booster neutralizing antibody against BA.1 and BA.2 variant after adjustment with age and gender. ConclusionsA heterologous mRNA boost is highly immunogenic. The pre-existing neutralizing antibody level and CD4+ T cells response correlates with post-booster neutralization reactivity against the Omicron variant.