Durable Immune Responses Research Articles

LMAP-07 POTENTIAL MECHANISM OF IMMUNE ESCAPE RELATED TO TUMOR-ASSOCIATED MACROPHAGE IN GLIOBLASTOMA AFTER COMBINED THERAPY WITH RADIOTHERAPY AND IMMUNE CHECKPOINT BLOCKER

Abstract Immune checkpoint blockers (ICBs) have revolutionized the treatment of cancer. Radiotherapy (RT) has been demonstrated to increase the survival benefit of ICBs in some cancers through its local and systemic immunomodulation, although its efficacy in glioblastoma (GBM) is very limited. With a thorough investigation of the immune responses to single and dual treatment utilizing single-cell RNA-seq analyses on the synergy of RT and anti-PD-L1 antibody (aPD-L1), we studied the potential mechanism of immune escape in GBM even when RT and ICB are combined. Our findings demonstrated a statistically significant longer survival of mice treated with RT and aPD-L1 combined than either single modality of treatment in an orthotopic syngeneic GBM model achieving a 70% cure rate. In the tumor tissues collected from the mouse brain that failed dual treatment, i.e., immune escaped, immune cell profiling still demonstrated much lower T regulatory cells and higher CD8+ cytotoxic T cells infiltrated to tumor, and elevated CD8+/CD4+ and CD8+/Treg ratios in the dual therapy group compared to single therapies, as expected with synergistic effects of dual treatment. RT with aPD-L1 markedly reduced CD8+ and CD4+ T exhaustion cells and elevated T-memory cells in comparison to single modality groups. Nevertheless, compared to the RT alone or no treatment control group, dual therapy failed to decrease the proportion of Arginase1-positive glioma-associated macrophages (GAM) in macrophage/monocytes in tumor microenvironment, which were considerably increased if treated with aPD-L1 only. Moreover, the combination of RT with aPD-L1 did not alter immunosuppressive gene expression in the macrophage/monocyte groups. In conclusion, our research demonstrated that RT and aPD-L1 together may elicit a potent and durable antitumor immune response in the GBM mouse model through regulating lymphocytes but not macrophages. Our findings point to the urgent need for research into GAM-modulating drug and their potential to prevent immunological escape.

Blocking LTB4 signaling-mediated TAMs recruitment by Rhizoma Coptidis sensitizes lung cancer to immunotherapy

BackgroundImmune checkpoint blockade (ICB) induces durable immune responses across a spectrum of advanced cancers and revolutionizes the oncology field. However, only a subset of patients achieves long-lasting clinical benefits. Tumor-associated macrophages (TAMs) usually secrete immunosuppressive cytokines and contribute to the failure of ICB therapy. Therefore, it is crucial to mechanically manipulate the abundance and function of TAMs in the tumor microenvironment (TME), which can offer a promising molecular basis to improve the clinical response efficacy of ICB in cancer patients. PurposeThis study aims to investigate TAMs in the immunosuppressive microenvironment to identify new therapeutic targets, improve the ability to predict and guide responses to clinical immunotherapy, and develop new strategies for immunotherapy of lung tumors. MethodsLewis lung carcinoma (LLC) xenograft-bearing mouse models were established to analyze the antitumor activity of Rhizoma Coptidis (RC) in vivo. A systems pharmacology strategy was used to predict the correlation between RC and M2 macrophages. The effect of RC on the abundance of M2 macrophages was analyzed by flow cytometry of murine samples. Western blot was performed to analyze the expression of Leukotriene A4 hydrolase (LTA4H) and LTB4 receptor 1 (BLT1) in harvested lung cancer tissues. The impact of blocking leukotriene B4 (LTB4) signaling by RC on the recruitment of M2 macrophages was assessed in vitro and in vivo. Transwell migration assays were conducted to clarify the inhibition of macrophage migration by blocking LTB4. Lta4h−/− mice were used to investigate the sensitivity of immunotherapy to lung cancer by blocking the LTB4 signaling. ResultsHere, we report that RC, an herbal medicine from the family Ranunculaceae, suppresses the recruitment and immunosuppressive function of TAMs, which in turn sensitizes lung cancer to ICB therapy. Firstly, a systems pharmacology strategy was proposed to identify combinatorial drugs for ICB therapy with a systems biology perspective of drug-target-pathway-TME phenotype. We predicted and verified that RC significantly inhibits tumor growth and the infiltration of M2-TAMs into TME of LLC tumor-bearing mice. Then, RC inhibits the recruitment of macrophages to the tumor TME via blocking LTB4 signaling, and suppresses the expression of immunosuppressive factors (IL-10, TGF-β and VEGF). As a result, RC enables CD8+ T cells to retain their proliferative and infiltrative abilities within the TME. Ultimately, these events promote cytotoxic T-cell-mediated clearance of tumor cells, which is further enhanced by the addition of anti-PD-L1 therapy. Furthermore, we employed LTA4H deficient mice (Lta4h−/− mice) to evaluate the antitumor efficiency, the results showed that the efficacy of immunotherapy was enhanced due to the synergistic effect of LTB4 signaling blockage and ICB inhibition, leading to remarkable inhibition of tumor growth in a mouse model of lung adenocarcinoma. ConclusionsTaken together, these findings suggest that RC enhances antitumor immunity, providing a rationale for combining RC with immunotherapies as a potential anti-cancer treatment strategy.

Influenza vaccine format mediates distinct cellular and antibody responses in human immune organoids

Highly effective vaccines elicit specific, robust, and durable adaptive immune responses. To advance informed vaccine design, it is critical that we understand the cellular dynamics underlying responses to different antigen formats. Here, we sought to understand how antigen-specific B and Tcells were activated and participated in adaptive immune responses within the mucosal site. Using a human tonsil organoid model, we tracked the differentiation and kinetics of the adaptive immune response to influenza vaccine and virus modalities. Each antigen format elicited distinct B and Tcell responses, including differences in their magnitude, diversity, phenotype, function, and breadth. These differences culminated in substantial changes in the corresponding antibody response. A major source of antigen format-related variability was the ability to recruit naive vs. memory B and Tcells to the response. These findings have important implications for vaccine design and the generation of protective immune responses in the upper respiratory tract.

Nanoparticle-Based Adjuvants and Delivery Systems for Modern Vaccines.

Ever since the development of the first vaccine, vaccination has had the great impact on global health, leading to the decrease in the burden of numerous infectious diseases. However, there is a constant need to improve existing vaccines and develop new vaccination strategies and vaccine platforms that induce a broader immune response compared to traditional vaccines. Modern vaccines tend to rely on certain nanotechnology platforms but are still expected to be readily available and easy for large-scale manufacturing and to induce a durable immune response. In this review, we present an overview of the most promising nanoadjuvants and nanoparticulate delivery systems and discuss their benefits from tehchnological and immunological standpoints as well as their objective drawbacks and possible side effects. The presented nano alums, silica and clay nanoparticles, nanoemulsions, adenoviral-vectored systems, adeno-associated viral vectors, vesicular stomatitis viral vectors, lentiviral vectors, virus-like particles (including bacteriophage-based ones) and virosomes indicate that vaccine developers can now choose different adjuvants and/or delivery systems as per the requirement, specific to combatting different infectious diseases.

Targeting macrophage Syk enhances responses to immune checkpoint blockade and radiotherapy in high-risk neuroblastoma.

Neuroblastoma (NB) is considered an immunologically cold tumor and is usually less responsive to immune checkpoint blockade (ICB). Tumor-associated macrophages (TAMs) are highly infiltrated in NB tumors and promote immune escape and resistance to ICB. Hence therapeutic strategies targeting immunosuppressive TAMs can improve responses to ICB in NB. We recently discovered that spleen tyrosine kinase (Syk) reprograms TAMs toward an immunostimulatory phenotype and enhances T-cell responses in the lung adenocarcinoma model. Here we investigated if Syk is an immune-oncology target in NB and tested whether a novel immunotherapeutic approach utilizing Syk inhibitor together with radiation and ICB could provide a durable anti-tumor immune response in an MYCN amplified murine model of NB. Myeloid Syk KO mice and syngeneic MYCN-amplified cell lines were used to elucidate the effect of myeloid Syk on the NB tumor microenvironment (TME). In addition, the effect of Syk inhibitor, R788, on anti-tumor immunity alone or in combination with anti-PDL1 mAb and radiation was also determined in murine NB models. The underlying mechanism of action of this novel therapeutic combination was also investigated. Herein, we report that Syk is a marker of NB-associated macrophages and plays a crucial role in promoting immunosuppression in the NB TME. We found that the blockade of Syk in NB-bearing mice markedly impairs tumor growth. This effect is facilitated by macrophages that become immunogenic in the absence of Syk, skewing the suppressive TME towards immunostimulation and activating anti-tumor immune responses. Moreover, combining FDA-approved Syk inhibitor, R788 (fostamatinib) along with anti-PDL1 mAb provides a synergistic effect leading to complete tumor regression and durable anti-tumor immunity in mice bearing small tumors (50 mm3) but not larger tumors (250 mm3). However, combining radiation to R788 and anti-PDL1 mAb prolongs the survival of mice bearing large NB9464 tumors. Collectively, our findings demonstrate the central role of macrophage Syk in NB progression and demonstrate that Syk blockade can "reeducate" TAMs towards immunostimulatory phenotype, leading to enhanced T cell responses. These findings further support the clinical evaluation of fostamatinib alone or with radiation and ICB, as a novel therapeutic intervention in neuroblastoma.

Efficacy and Durability of Immune Response after Receipt of HPV Vaccines in People Living with HIV.

People living with HIV (PLH) experience higher rates of HPV infection as well as an increased risk of HPV-related disease, including malignancies. Although they are considered a high-priority group for HPV vaccination, there are limited data regarding the long-term immunogenicity and efficacy of HPV vaccines in this population. Seroconversion rates and geometric mean titers elicited by vaccination are lower in PLH compared to immunocompetent participants, especially in individuals with CD4 counts below 200 cells/mm3 and a detectable viral load. The significance of these differences is still unclear, as a correlate of protection has not been identified. Few studies have focused on demonstrating vaccine efficacy in PLH, with variable results depending on the age at vaccination and baseline seropositivity. Although waning humoral immunity for HPV seems to be more rapid in this population, there is evidence that suggests that seropositivity lasts at least 2-4 years following vaccination. Further research is needed to determine the differences between vaccine formulations and the impact of administrating additional doses on durability of immune protection.

EO2401 (E) peptide immunotherapy + nivolumab (N) +/- bevacizumab (B) in recurrent glioblastoma (GB): EOGBM1-18/ROSALIE.

2020 Background: EO2401 was designed to activate/expand existing memory T cells recognizing specific protein sequences from gut bacteria, which cross-react with tumor associated antigens (TAAs). E contains 3 CD8 HLA-A2 epitopes with mimicry to GB-TAAs (IL13Rα2, BIRC5, and FOXM1) and the CD4 epitope UCP2. Methods: Patients (pt) at 1st progression GB received E (300 µg/peptide, q2w x4 then q4w) with N (3 mg/kg q2w) in cohorts: 1a E x2 → EN; 2a/1, 2a/2 and 2b EN from start; 2c EN x2 → surgery → EN; 3/1 and 3/2 EN + B (10mg/kg q2w) (Table). Results: Among 100 treated pt EN+/-B was well tolerated, with E associated events limited to local skin reactions (45% of pt; 96% Grades 1/2, and 4% Grade 3) and N-/B-tox consistent with historical data. EN induced immune response against all 3 mimics in 94% of 35 tested pt (all pt responded against at least 2 mimics), detectable as early as 2 weeks after first EN, and with durations beyond 10 months. Cross-reactivity against human peptides found in 89%. Conclusions: EN +/- B was well tolerated and generated fast and durable immune responses. EN survival like current standards. Delayed N was not advantageous for outcome. sLDB increased trt duration of EN, and improved efficacy. Continuous B plus EN further improved efficacy. Neo-/adjuvant EN was clinically feasible. Updated data, including C3/2 to confirm C3/1, to be presented. Clinical trial information: NCT04116658 . [Table: see text]

Phase 1 study of LB1410, a bivalent TIM-3/PD-1 bispecific antibody, in patients with advanced solid tumors or lymphoma.

TPS2663 Background: Cancer immunotherapies targeting PD-1 or PD-L1 have been proven effective in causing durable antitumor immune responses with less toxicity in many types of tumors. However, the response rate of anti-PD-1/PD-L1 treatments is far from satisfactory and most patients show primary or acquired resistance to the treatments. Tim-3, one of the next generation of immune checkpoint targets, co-expressed on exhausted T cells with PD-1. It is also expressed by innate immune populations, including NK and DC. Dual blocking PD-1 and Tim-3 not only on T cells but also on DC, NK cells may achieve better clinical benefit. LB1410 is a recombinant humanized anti-PD-1/TIM-3 bispecific antibody (BsAb) developed by L&L Biopharma Co., Ltd. for the patients who are resistant to or refractory from PD-1/PD-L1 treatments. It blocked the immune checkpoint PD-1 and TIM-3-mediated immunosuppressive signal pathways simultaneously, showed better T/DC cell activity and in vivo anti-tumor efficacy compared to Tim-3 and PD-1 antibody combination in preclinical studies. Methods: This is a FIH, multicenter, non-randomized, open label, phase 1 study of LB1410 in Participants With Advanced Solid Tumor or Lymphoma（Keyplus-001）. The planned sample size is approximately 100 patients in two parts: part 1 dose escalation will evaluate safety, tolerability, pharmacokinetics (PK), pharmacodynamics, and determine the maximum tolerated dose (MTD) and/or the recommended phase 2 dose (RP2D), and Part 2 dose expansion will further characterize the safety profile and preliminary tumor response in several cohorts including NSCLC, CRC, EC etc. Enrollment criteria include adults with life expectancy of > 3 months, ECOG performance status 0-1，histologically or cytologically confirmed advanced and/or metastatic solid tumor malignancies or lymphoma for which standard treatment fails, or no standard treatment is available, or standard treatment is not applicable at this stage. Exclusion criteria include pregnancy, lactation, or breastfeeding, ongoing or recent evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments. The primary endpoints are incidence of dose limiting toxicities and adverse events, MTD, and recommended phase 2 dose. Secondary objectives will evaluate PK parameters, preliminary antitumor activity, and immunogenicity of LB1410. Besides, the pharmacodynamics (PD) biomarkers related to LB1410 treatment, clinical activity will be explored. This clinical trial is in progress; cohorts 1 to 5 in dose escalation part have been completed. Clinical trial information: NCT05357651 .

A phase 1/2 study of a first-in-human immune-stimulating antibody conjugate (ISAC) BDC-1001 in patients with advanced HER2-expressing solid tumors.

2538 Background: BDC-1001 is a HER2-targeted immune-stimulating antibody conjugate (ISAC), designed to trigger local activation of the innate immune system and generate a durable tumor-targeted adaptive immune response. BDC-1001 incorporates a trastuzumab biosimilar (EG12014) conjugated to a proprietary TLR7/8 agonist using a non-cleavable linker and a cell membrane-impermeable payload. An international phase 1/2 study was initiated to evaluate the safety of BDC-1001 ± nivolumab (nivo) and to identify the recommended phase 2 dose (RP2D) considering PK/PD analyses and preliminary efficacy. Methods: Dose-escalation (3+3, +backfills) enrolled patients (pts) with HER2-positive (amplified, or IHC 3+) or HER2 low (IHC 2+ and not amplified) solid tumors who had progressed after standard therapies. BDC-1001 was given IV q3w, q2w, or q1w as monotherapy (mono; n=91) and q2w or q1w with nivo 240 mg q2w (combo; n=27). Results: As of Nov 23, 2022, 118 pts with 16 different tumor types, were enrolled with BDC-1001 doses ranging from 0.15 to 20 mg/kg. Mean age was 61 yrs with a median of 4 and 5 prior lines of therapy (range, 1-11; 1-14; prior anti-HER2 therapy (HER2Tx) [66%/70%], immunotherapy (IO) [23%/22%]) for mono and combo, respectively. Median follow-up time was 5.0-6.1 months. Treatment was well tolerated with only 1 DLT (Gr3 supraventricular tachycardia) at 8 mg/kg q1w combo cohort. Low-grade IRRs were the most common related TEAEs (mono, 26.5%; combo, 25.9%). A related SAE (Gr4, bronchopulmonary hemorrhage) was seen in 1 pt (mono, 1.1%). Antitumor activity was observed at a range of doses and malignancies. There were 4 confirmed (RECIST 1.1) durable PRs (all in MSS tumors with low/intermediate TMB, prior Tx: 1 HER2Tx, 1 IO) including 1 pt with colon cancer (CRC) in the 5 mg/kg q3w mono cohort, and 3 in the 20 mg/kg q2w cohorts (mono 1/7; combo 2/7; ovarian, biliary, and rectal cancers). After the data cut, an additional PR (unconfirmed) was reported at week 6 in a pt with CRC receiving 12m/kg 1qw combo. Ten additional pts had SD lasting ≥6 months (8 mono; 2 combo; prior Tx: 6 HER2Tx; 1 IO; e.g., ovarian, endometrial, colorectal, gastric). Durable SDs were most frequent in the q2w cohorts. BDC-1001 exposure (e.g., Cmin) correlated with activity among pts in q2w cohorts. Increases in myeloid and T cell infiltration markers in post-Tx tumor biopsies align with mechanism of action (MoA). No anti-drug antibodies were detected. Conclusions: BDC-1001 mono and combo were well-tolerated. Targeted serum exposure levels were achieved, and encouraging clinical activity was noted in heavily pretreated pts with various HER2 positive tumors, especially in the 20 mg/kg q2w cohorts. Immune biomarker changes from plasma and tumor were consistent with MoA of this ISAC. These data support further development of BDC-1001 with phase 2 expansion in HER2-expressing solid tumors at the RP2D. Clinical trial information: NCT04278144 .

Results of phase I-II bridging study for Nous-209, a neoantigen cancer immunotherapy, in combination with pembrolizumab as first line treatment in patients with advanced dMMR/MSI-h colorectal cancer.

e14665 Background: Microsatellite instability (MSI) is a molecular hallmark in which systemic deficiency of DNA mismatch-repair (dMMR) generates tumor-specific frameshift peptides (FSPs). Nous-209 is an off-the-shelf cancer vaccine targeting 209 FSPs selected from dMMR/MSI-H tumors (Leoni, G. et al., 2020). Treatment options for unresectable dMMR/MSI-H tumors have improved, but further efforts to increase long-term progression-free survival are needed. NOUS-209-01 Phase I demonstrated that Nous-209 and pembrolizumab is safe, well tolerated, and provides clinical benefit in advanced gastric and CRC dMMR/MSI-H tumors (Fakih et al., 2022). Moreover, Nous-209 induces durable specific anti-tumoral immune response, capable of successfully infiltrating the tumor (D’Alise et al., 2022). Here, we present data from NOUS-209-01 study Phase I-II expansion cohort at the recommended phase 2 dose (RP2D) of Nous-209 and pembrolizumab in adults with dMMR/MSI-H locally advanced unresectable or metastatic colorectal cancer (mCRC) eligible for 1st line immune checkpoint inhibition. Methods: NOUS-209-01 ( NCT04041310 ) Phase I-II bridge expansion cohort receives one GAd20-209-FSP prime intramuscularly at the 1st infusion of pembrolizumab, followed by 3 MVA-209-FSP boosts with the 2nd, 3rd and 4th pembrolizumab cycles. Patients can continue treatment with pembrolizumab for 18 months. Response assessment is evaluated every 9 (+/-1) weeks by CT imaging, according to RECIST v1.1 criteria. ctDNA assessments are at baseline, 11, 28, 49, 79 weeks and at objective progression on study. Results: Phase I-II bridge enrolled 8 patients with dMMR/MSI-H treatment-naïve mCRC. One patient had clinical progression before 1st scan and was excluded as non-evaluable and 7 were evaluable for tumor response. 5/7 (71%, CI: 95% 29.0, 96.3) patients achieved objective response: 1 (14%) complete response (CR) and 4 (57%) partial responses (PR). 2 patients (29%) had disease progression (PD) at the 1st scan. ctDNA assessments were available for 6 out of 7 patients (4 PR; 2 PD); ctDNA levels reduced >50% at week 11 in the 4 PR patients, in contrast to a 28% increase in 1 PD. Interestingly 1 PD patient had ctDNA > 50% reduction. The median follow-up at data cut-off was 7.5 months (range: 3.3-8.4), median progression free survival and median duration of response have not been reached. 6/7 (85.7%) patients had treatment emergent adverse events (TEAE), all mild or moderate grade; no TEAEs were serious or led to treatment discontinuation. Conclusions: The combination of Nous-209 and pembrolizumab is safe, well tolerated and shows encouraging clinical efficacy in patients with treatment-naive dMMR/MSI-H mCRC eligible for anti-PD-1 therapy. The study is ongoing and expanding to Phase II randomization with a new accelerated Nous-209 vaccination schedule. Clinical trial information: NCT04041310 .

A pilot trial of personalized neoantigen pulsed autologous dendritic cell vaccine as adjuvant treatment in hepatocellular carcinoma.

e14658 Background: The primary means of treating hepatocellular carcinoma (HCC) is radical surgery. However, HCC has a high propensity to recur post-operatively, and no standard adjuvant therapies have been approved. Tumor neoantigens, which are epitopes derived from tumor-specific mutations, may be utilized in personalized vaccines to activate T cell responses. This trial aims to assess the safety and efficacy of personalized neoantigen pulsed autologous dendritic cell vaccine (Neo-DCVac-02) in patients with HCC. Methods: Eligible patients had histologically confirmed high-risk HCC after radical surgery. Upon obtaining the baseline biopsy specimens and PBMCs of appropriate quality for DNA and RNA sequencing, neoantigen prediction, screening, and synthesis were performed. Subsequently, autologous dendritic cells (DCs) were generated and pulsed with neoantigen peptides to produce Neo-DCVac-02.On day 0, patients were treated with cyclophosphamide at a dose of 250 mg/m2. The prepared Neo-DCVac-02 vaccine was administered subcutaneously on day 1, followed by GM-CSF administered daily for 5 days. The primary objectives of this study were to evaluate the feasibility and safety/tolerability. Secondary objectives included assessment of immune responses (via vaccine response: IFNγ ELISpot), recurrence-free survival (RFS), and overall survival (OS). Results: A total of 32 patients provided informed consent to initiate the process of personalized neoantigen discovery, of which 26 (81%) met the requirements for successful product selection for clinical manufacturing. And feasibility was shown with 13 patients receiving Neo-DCVac-02. Thirteen patients did not receive neoantigen vaccines (7 for progressive disease,6 for withdrawal of informed consent because of COVID-19). Treatment was well-tolerated with no grade 2+ treatment-related adverse events (TRAEs). The common grade 1TRAEs were neutropenia (8.3%), injection site reactions (75%), rash (16.7%), fatigue (8.3%), and headache (8.3%). The median follow-up to date is 19.30 (14.4-31.9) months, with median RFS and OS not yet reached and a 1-year RFS of 83%. Five of 13 evaluable patients showed elevated antigen-specific T-cell activity by IFNγ ELISpot for more than 50% of neoantigen peptides in Neo-DCVac-02, and persistent cellular responses were noted out to 1 year. Increases in activation/co-stimulatory of T cells seen after treatment with Neo-DCVac-02 revealed by Flow-cytometric analyses, suggest immune priming. Conclusions: These data demonstrate that Neo-DCVac-02 is safe, well tolerated, and able to generate durable antigen-specific lymphocyte immune responses. Early signs of clinical efficacy were observed in HCC patients. Clinical trial information: NCT04147078 .

Immunoglobulin G follow-up and immune response longevity analysis in SARS-CoV-2 convalescent patients and vaccinated individuals: A longitudinal analysis.

Although the detection of immunoglobulin G (IgG) molecules has long been considered to be crucial for successful humoral immune defence against infections and harmful metabolites, it has become increasingly important in relation to SARS-CoV-2 research. To compare longitudinal changes in IgG titres in post-infection and post-vaccination Iraqi participants, and to estimate the protective benefits of the two principal vaccines used in Iraq. This quantitative study used samples from SARS-CoV-2 recovered patients (n= 75), those vaccinated with two doses of Pfizer or Sinopharm vaccine (n= 75), and healthy unvaccinated individuals (n= 50) who formed a control group. Participant ages (range 20-80 years) and sex (52.7% men, 47.3% females). An enzyme-linked immunosorbent assay was used to measure IgG. IgG antibody levels peaked in the first month and tapered off in the following three months in both convalescent and vaccinated groups. The latter showed a significant decrease in IgG titres than in the convalescent group. Samples from the group given the mRNA vaccination that targeted spike (S) proteins might have a cross-reactivity between nucleocapsid (N) and spike (S) proteins. Participants who had recovered from or who were vaccinated against SARS-CoV-2 exhibited a protective, persistent and durable humoral immune response for at least a month. This was more potent in the SARS-CoV-2 convalescent group compared to the vaccinated cohort. The IgG titres decayed faster after vaccination with Sinopharm than following the Pfizer-BioNTech vaccine.

Safety and immunogenicity of a modified COVID-19 mRNA vaccine, SYS6006, as a fourth-dose booster following three doses of inactivated vaccines in healthy adults: an open-labeled Phase 1 trial

Abstract The continuous emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants led to a rapid decline in protection efficacy and neutralizing titers even after three doses of COVID-19 vaccines. Here, we report an open-labeled Phase I clinical trial of a modified mRNA vaccine (SYS6006) as a fourth-dose booster in healthy adults. Eighteen eligible participants, who had completed three doses of inactivated COVID-19 vaccines, received a fourth boosting dose of SYS6006-20 μg. Eighteen convalescent COVID-19 patients were enrolled for the collection of serum samples as a comparator of immunogenicity. The primary endpoint of this trial was titers of anti-receptor binding domain of spike glycoprotein (RBD) antibodies of the Omicron strain (BA.2 and BA.4/5) in serum; titers of neutralizing antibodies against pseudovirus of the Omicron strain (BA.2 and BA.4/5). The secondary endpoint was the incidence of adverse events within 30 days after the boosting. The exploratory endpoint was the cellular immune responses (interferon gamma, IFN-γ). This trial was registered with the Chinese Clinical Trial Registry website. No serious adverse events were reported within 30 days after vaccination. No Grade 3 fever or serious adverse event was reported in the SYS6006 group. Notably, SYS6006 elicited higher titers and longer increases in anti-RBD antibodies and neutralizing antibodies (>90 days) compared with the convalescent group (P < 0.0001) against Omicron strain (BA.2 and BA.4/5). Besides, higher positive spots of T-cell-secreting IFN-γ were observed in the SYS6006 group than those in the convalescent group (P < 0.05). These data demonstrated that SYS6006 was well tolerated and highly immunogenic, generating a stronger and more durable immune response against different variants of SARS-CoV-2.

L-fucose enhances anti-tumor immunity through modulation of monocyte-derived dendritic cell signaling

Abstract Although immunotherapies have emerged as standard of care for severals cancer types, their efficacy remains limited to ~30% of patients. Limited efficacy has in part been attributed to a lack of infiltrating tumor-suppressive immune cells and overabundance of immunosuppressive cell populations. To combat this problem, extensive research efforts have focused on modulating intratumoral T cells to overcome the immunosuppressive tumor microenvironment (TME). While these treatment modalities show promise in preventing intratumoral T cell exhaustion, they fail to provide robust and durable anti-tumor immune responses. For this reason, the targeting of other intratumoral immune subpopulations—particularly dendritic cells (DC)—has become a subject of increased study. The dual activation of anti-tumor and suppression of pro-tumor immune populations is expected to significantly enhance immunotherapeutic outcomes. Recently, our group found that the dietary sugar L-fucose (L-fuc) reduces melanoma tumor growth viaa CD4 +T cell-dependent mechanism. Interestingly, analysis of immune cells in the tumors of L-fuc-treated mice revealed dynamic changes in the DC compartment, predominantly in the monocyte-derived DC subset (moDC). Additionally, myeloid cells treated ± L-fucex vivoexhibited enhanced T cell stimulation, increased neutral fluorescent bait uptake, and altered cytokine production. qPCR-RT analysis revealed that L-fuc affects downstream CD209 signaling, leading to a shift towards an immunostimulatory signature. Together, these data suggest a mechanism to enhance anti-tumor immunity by increasing abundance and immunostimulatory activity of moDCs and supports the use of L-fucose as an immunotherapeutic agent. Supported by funding from Moffitt Cancer Center Skin Cancer Sport Project

Characterization of the cell-mediated immune response to the NIH tetravalent dengue vaccine in an endemic population

Abstract Dengue is now endemic in more than 100 countries, with Southeast Asian and Pacific Island regions being the most seriously affected. The Department of Defense has long recognized the threat of dengue and has made great contributions to understanding it. The ideal dengue vaccine will provide long-lasting protection against all four serotypes of dengue virus (DENV1-4) and will be effective in both endemic and non-endemic populations. Several tetravalent dengue vaccines are either licensed or in advanced stages of clinical development, including the live attenuated vaccine candidate developed by the NIH. The purpose of this study is to characterize the cellular immune responses to the NIH vaccine, with particular attention to the activation and memory profiles of DENV-specific T and B cell populations. Our hypothesis is that the NIH vaccine induces a durable and tetravalent DENV-specific adaptive immune response, which varies in its magnitude and phenotype over time (3 years post-vaccination) and across age strata. To assess the magnitude, breadth, and evolution of DENV-specific T and B cells following vaccination, we use a suite of different assays, including IFNγ ELISpot, memory B cell fluorospot, and flow cytometry-based assays. This study evaluates the ability of the NIH vaccine to induce durable and balanced immune responses to all four DENV serotypes, and how that compares to naturally acquired immunity.

Serological assessment of the durability of vaccine-mediated protection against SARS-CoV-2 infection.

Abstract Virus-specific neutralizing antibodies are generally accepted as a correlate of protection against infection, though many questions remain about which components of the immune response protect against SARS-CoV-2 infection. We longitudinally measured Spike receptor binding domain (RBD)-specific serum IgG and nucleocapsid protein (NP)-specific serum IgG in a human cohort immunized with the Pfizer BNT162b2 vaccine. Serum samples were collected and stored at −80 °C. Antibody titers were quantitated using an endpoint dilution ELISA and reported as inverse titers. A four-fold or greater increase in NP-specific antibody titers was used as serological marker of clinical infection at some point prior to the sample collection. Using the RBD-specific IgG titer measured in participants’ serum collected prior to seroconversion for NP, we were able to calculate a protective threshold titer for RBD-specific IgG. We calculated the rate of decay of antibodies in participants who did not exhibit a four-fold increase in NP-specific IgG, i.e. had no serological evidence of infection, and found that, on average, the RBD-specific IgG response waned below the protective threshold by four months following vaccination. These data highlight the need for a more durable immune response to vaccination which may require different adjuvants, dosages, or vaccination schedules. This work was supported by The Robert M. Hearin Foundation, The Bower Foundation, and James L. Barksdale.

Toward a pan-SARS-CoV-2 vaccine targeting conserved epitopes on spike and non-spike proteins for potent, broad and durable immune responses.

The SARS-CoV-2 non-Spike (S) structural protein targets on nucleocapsid (N), membrane (M) and envelope (E), critical in the host cell interferon response and memory T-cell immunity, are grossly overlooked in COVID vaccine development. The current Spike-only vaccines bear an intrinsic shortfall for promotion of a fuller T cell immunity. Vaccines designed to target conserved epitopes could elicit strong cellular immune responses that would synergize with B cell responses and lead to long-term vaccine success. We pursue a universal (pan-SARS-CoV-2) vaccine against Delta, Omicrons and ever-emergent new mutants. We explored booster immunogenicity of UB-612, a multitope-vaccine that contains S1-RBD-sFc protein and sequence-conserved promiscuous Th and CTL epitope peptides on the Sarbecovirus N, M and S2 proteins. To a subpopulation (N = 1,478) of infection-free participants (aged 18-85 years) involved in a two-dose Phase-2 trial, a UB-612 booster (third dose) was administered 6-8 months after the second dose. The immunogenicity was evaluated at 14 days post-booster with overall safety monitored until the end of study. The booster induced high viral-neutralizing antibodies against live Wuhan WT (VNT50, 1,711) and Delta (VNT50, 1,282); and against pseudovirus WT (pVNT50, 11,167) vs. Omicron BA.1/BA.2/BA.5 variants (pVNT50, 2,314/1,890/854), respectively. The lower primary neutralizing antibodies in the elderly were uplifted upon boosting to approximately the same high level in young adults. UB-612 also induced potent, durable Th1-oriented (IFN-γ+-) responses (peak/pre-boost/post-boost SFU/106 PBMCs, 374/261/444) along with robust presence of cytotoxic CD8+ T cells (peak/pre-boost/post-boost CD107a+-Granzyme B+, 3.6%/1.8%/1.8%). This UB-612 booster vaccination is safe and well tolerated without SAEs. By targeting conserved epitopes on viral S2, M and N proteins, UB-612 could provide potent, broad and long-lasting B-cell and T-cell memory immunity and offers the potential as a universal vaccine to fend off Omicrons and new VoCs without resorting to Omicron-specific immunogens. ClinicalTrials.gov ID: NCT04773067; ClinicalTrials.gov ID: NCT05293665; ClinicalTrials.gov ID: NCT05541861.

COVID-19 vaccines based on viral nanoparticles displaying a conserved B-cell epitope show potent immunogenicity and a long-lasting antibody response.

The COVID-19 pandemic caused by SARS-CoV-2 sparked intensive research into the development of effective vaccines, 50 of which have been approved thus far, including the novel mRNA-based vaccines developed by Pfizer and Moderna. Although limiting the severity of the disease, the mRNA-based vaccines presented drawbacks, such as the cold chain requirement. Moreover, antibody levels generated by these vaccines decline significantly after 6 months. These vaccines deliver mRNA encoding the full-length spike (S) glycoprotein of SARS-CoV-2, but must be updated as new strains and variants of concern emerge, creating a demand for adjusted formulations and booster campaigns. To overcome these challenges, we have developed COVID-19 vaccine candidates based on the highly conserved SARS CoV-2, 809-826 B-cell peptide epitope (denoted 826) conjugated to cowpea mosaic virus (CPMV) nanoparticles and bacteriophage Qβ virus-like particles, both platforms have exceptional thermal stability and facilitate epitope delivery with inbuilt adjuvant activity. We evaluated two administration methods: subcutaneous injection and an implantable polymeric scaffold. Mice received a prime-boost regimen of 100 μg per dose (2 weeks apart) or a single dose of 200 μg administered as a liquid formulation, or a polymer implant. Antibody titers were evaluated longitudinally over 50 weeks. The vaccine candidates generally elicited an early Th2-biased immune response, which stimulates the production of SARS-CoV-2 neutralizing antibodies, followed by a switch to a Th1-biased response for most formulations. Exceptionally, vaccine candidate 826-CPMV (administered as prime-boost, soluble injection) elicited a balanced Th1/Th2 immune response, which is necessary to prevent pulmonary immunopathology associated with Th2 bias extremes. While the Qβ-based vaccine elicited overall higher antibody titers, the CPMV-induced antibodies had higher avidity. Regardless of the administration route and formulation, our vaccine candidates maintained high antibody titers for more than 50 weeks, confirming a potent and durable immune response against SARS-CoV-2 even after a single dose.

Combination of Recombinant Proteins S1/N and RBD/N as Potential Vaccine Candidates.

Despite all successful efforts to develop a COVID-19 vaccine, the need to evaluate alternative antigens to produce next-generation vaccines is imperative to target emerging variants. Thus, the second generation of COVID-19 vaccines employ more than one antigen from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to induce an effective and lasting immune response. Here, we analyzed the combination of two SARS-CoV-2 viral antigens that could elicit a more durable immune response in both T- and B-cells. The nucleocapsid (N) protein, Spike protein S1 domain, and receptor binding domain (RBD) of the SARS-CoV-2 spike surface glycoproteins were expressed and purified in a mammalian expression system, taking into consideration the posttranscriptional modifications and structural characteristics. The immunogenicity of these combined proteins was evaluated in a murine model. Immunization combining S1 or RBD with the N protein induced higher levels of IgG antibodies, increased the percentage of neutralization, and elevated the production of cytokines TNF-α, IFN-γ, and IL-2 compared to the administration of a single antigen. Furthermore, sera from immunized mice recognized alpha and beta variants of SARS-CoV-2, which supports ongoing clinical results on partial protection in vaccinated populations, despite mutations. This study identifies potential antigens for second-generation COVID-19 vaccines.

A “2 + 2” strategy for tumor immune microenvironment remodeling based on complementary immune checkpoint blockade

Despite a clinical success of cancer immunotherapy, its efficacy is often limited due to immune resistance and insufficient immune response induced by the tumor immune microenvironment (TIME). Thus, further appropriate interventions are needed to reshape the TIME and to maintain an effective and durable immune response. Herein, we report that a strategy involving complementary immune checkpoint blockade of ADAR1 and PD-1 can enhance the immune response and decrease the rate of immune evasion by regulating the TIME. We first designed a charge-reversible nanosystem Au-PEI/shADAR1/PEI-citraconic anhydride (AAPC), to effectively deliver shADAR1 to inhibit expression of ADAR1, a potential immune checkpoint in tumor cells. Then, we demonstrated a simultaneous decrease in immune escape and activation of antitumor immunity in tumor-bearing mice upon combined treatment with AAPC and an anti-PD-1 antibody. The immune checkpoint blockade acts on T cells and we show that this combination therapy was more efficacious than individual treatments. Additionally, mechanistic and transcriptomic analysis confirmed that complementary immune checkpoint blockade regulated the abundance of immune cells. Finally, combined with X-ray irradiation, a “2 + 2” strategy involving combined dual normalization (“2”, dsRNA sensitization and anti-PD therapy) and dual enhancement (“2”, antigen presentation by radiotherapy and immunogenetic cell death induced by MDA5 activation) immunotherapy efficiently reshaped the TIME by regulating a variety of immune cells.