Exploring the Potential of Humoral Immune Response to Commensal Bifidobacterium as a Biomarker for Human Health, including Both Malignant and Non-Malignant Diseases: A Perspective on Detection Strategies and Future Directions.

In this comprehensive review, we explore the pivotal role of commensal Bifidobacterium (c-BIF) as potent non-self-antigens through antigenic mimicry, along with exploring the potential of humoral immune responses for both malignant and non-malignant disease. c-BIF, a predominant component of the human gut microbiome encompassing around 90% of the human genome, has emerged as a pivotal player in human biology. Over recent decades, there has been extensive research elucidating the intricate connections between c-BIF and various facets of human health, with particular emphasis on their groundbreaking impact on anti-cancer effects and the management of non-malignant diseases. The multifaceted role of c-BIF is explored, ranging from enhancing anti-tumor immunity to improving the efficacy of anti-cancer and anti-infectious disease strategies, and serving as predictive biomarkers for various diseases. Recent studies highlight not only c-BIF's promotion of anti-tumor immunity but also their role in enhancing the efficacy of immune checkpoint inhibitors. The review emphasizes the promising avenue of manipulating the gut microbiota, particularly c-BIF, for modulating cancer immunotherapy with targeted effects on tumor cells while minimizing harm to normal tissue. In the context of infectious and inflammatory diseases, the crucial role of c-BIFs in the management of COVID-19 symptoms is examined, emphasizing their impact on the severity of and immune response to COVID-19. Furthermore, c-BIF exhibits preventive and therapeutic effects on Human Papillomaviruses (HPV) and shows promise in improving inflammatory bowel diseases. The potential application of c-BIF as a biomarker for immunotherapy is explored, with a specific emphasis on its predictive and prognostic value in cancer. Suggestions are made regarding the use of humoral immune responses to cytotoxic T lymphocyte (CTL) epitope peptides that share motifs with c-BIF, proposing them as potential markers for predicting overall survival in diverse cancer patients. In conclusion, c-BIF emerges as a crucial and multifaceted determinant of human health, across anti-tumor immunity to infectious and inflammatory disease management. The manipulation of c-BIF and gut microbiota presents a promising avenue for advancing therapeutic strategies, particularly in the realm of cancer immunotherapy. Additionally, this review highlights the significance of c-BIF as potent non-self-antigens via antigenic mimicry, emphasizing the importance of robust humoral immune responses against c-BIF for preventing various diseases, including inflammatory conditions. Elevated levels of circulating antibodies against c-BIF in healthy individuals may serve as potential indicators of lower risks for malignant and non-malignant diseases.

Evaluation of the Immunological Response of Childhood Cancer Patients Treated with a Personalized Peptide Vaccine for Refractory Soft Tissue Tumor: A Four-Case Series.

This case series aimed to evaluate the peptide-specific immunoglobulin G (IgG) response, clinical effectiveness, and the safety of a personalized peptide vaccine (PPV) in four children with refractory solid cancer. Although the pre-vaccination IgG responses were suppressed, IgG levels against the vaccinated peptides after 12 vaccinations were increased in all three cases who received at least 12 vaccinations. Vaccination-related adverse effects were grade 1 injection-site local skin lesions. One patient, whose diagnosis was relapsed rhabdomyosarcoma, remains in sustained remission after 37 months. Although the pre-vaccination immune response in this patient was low, IgG levels against 2 of the 4 peptide vaccines were increased after the sixth vaccination, followed by a strong increase at the eighteenth vaccination against all 4 peptides, with a >100-fold increase vs. 2 peptides. The remaining three patients exhibited progressive disease and eventually died of their original cancer. The results of the current case series suggest that in cases of childhood solid tumors, when the tumor is controlled at the time of entry PPV may have some consolidation effect. Therefore, PPV could be a new immunotherapy modality for refractory childhood solid tumors.

Immune responses of patients without cancer recurrence after a cancer vaccine over a long term.

The present study aimed to clarify the humoral and cellular immune responses of patients with cancer who experienced no recurrence over a long term after receiving a cancer vaccine. The immune kinetics were investigated in response to a personalized peptide vaccination (PPV) among 44 Japanese patients without an active tumor at entry to the vaccination: Lung adenocarcinoma (n=11); colon (n=18); and breast cancer (n=15) (9, 10, 12, 8 and 5 patients with stage I, II, III and IV recurrences, respectively). The patients' immunoglobulin G (IgG) and cytotoxic T lymphocyte (CTL) activities were measured using a multiplexed Luminex assay and an interferon-γ release assay, respectively. There were no severe adverse events related to the PPV other than a grade III injection site reaction. A potent boost in IgG or CTL at the end of the 1st vaccination cycle was observed in 77% of the patients (n=84). The IgG levels were sustained throughout the follow-up period, whereas the CTL levels declined and were transient. A total of 37 of the 44 patients (84%) had no recurrence, with a median follow-up of 67.6 months (interquartile range, 45.6-82.8 months). Overall, the PPV induced long-term humoral immunity with transient cellular immunity in the majority of patients with cancer without an active tumor at their entry to the PPV.

Plasma level of prostate related-antigen peptide-reactive IgG is a prognostic factor of patients with breast cancer treated with personalized peptide vaccines.

The present study assessed plasma IgG in patients with metastatic recurrent breast cancer (mrBC) that is reactive to various T-cell epitope peptides of prostate-related antigens (PRAs), such as prostate-specific antigen, prostate-specific membrane antigen and prostate acid phosphatase. Patients were treated with personalized peptide vaccines (PPVs) which were selected and administered from a panel of candidate peptides based on human leukocyte antigen-types and prevaccination IgG levels to each peptide. The peptide panel consisted of 27 cytotoxic T-lymphocyte-epitope peptides derived from tumor-associated antigens, not including PRA. PRA peptides and peptide panels were retrospectively analyzed in 77 PPV-treated patients. The results revealed that PRA reactive IgG levels were increased after vaccination in 31 of the 97 patients included in the present study. Although there was no significant association between anti-PRA peptide levels and progression-free survival (PFS) or overall survival, anti-PRA peptide levels were significantly associated with PFS (P=0.009) in estrogen-receptor positive (ER+) patients with cancer. The results suggested that plasma anti-PRA IgG levels may be a useful prognostic marker for monitoring PPVs, particularly for ER+ patients with mrBC (trial registration no. from the UMIN Clinical Trials Registry, UMIN000001844).

Investigation of factors associated with reduced clinical benefits of personalized peptide vaccination for pancreatic cancer.

The aim of the present study was to determine the factors associated with reduced clinical benefits of personalized peptide vaccination (PPV) for pancreatic cancer. Phase II PPV clinical trials comprising 309 (8 non-advanced and 301 advanced-stage) patients with pancreatic cancer were conducted. Two to four peptides were selected among a set of 31 different peptides as vaccine candidates for personalized peptide vaccination based on human leukocyte antigen types and preexisting peptide-specific IgG levels, and subcutaneously injected. The selected peptides were subcutaneously injected. Of the 309 patients, 81 failed to complete the 1st PPV cycle due to rapid disease progression, and their median overall survival [2.1 months; 95% confidence interval (CI), 1.8-2.7] was significantly shorter than that of the remaining 228 patients (8.4 months; 95% CI, 8.4-9.9; P<0.01). 'Immune boosting' was defined when IgG levels before vaccination increased more than 2-fold after vaccination. Immune boosting was observed in the majority of patients with PPV irrespective of whether or not they received concomitant chemotherapy. Additionally, patients demonstrating immune boosting exhibited longer survival rates. Although the positive-response rates and peptide-specific IgG levels in pre- and post-vaccination samples differed among the 31 peptides, patients exhibiting immune boosting in response to each of the vaccinated peptides demonstrated longer survival times. Pre-vaccination factors associated with reduced clinical benefits were high c-reactive protein (CRP) levels, high neutrophil counts, lower lymphocyte and red blood cell counts, advanced disease stage and the greater number of chemotherapy courses prior to the PPV treatment. The post-vaccination factors associated with lower clinical benefits were PPV monotherapy and lower levels of immune boosting. In conclusion, pre-vaccination inflammatory signatures, rather than pre- or post-vaccination immunological signatures, were associated with reduced clinical benefits of personalized peptide vaccination (PPV) for pancreatic cancer.

A randomized phase III trial of personalized peptide vaccination for castration­resistant prostate cancer progressing after docetaxel.

First­line chemotherapy for men with metastatic castration­resistant prostate cancer (mCRPC) has been employed to improve overall survival (OS) and progression­free survival (PFS). However, several new agents for CRPC after first­line chemotherapy prolonged survival by only a few months. To develop a new treatment modality, we conducted a phase III randomized trial of personalized peptide vaccination (PPV) for human leukocyte antigen (HLA)­A24­positive patients with castration­resistant prostate cancer (CRPC) for whom docetaxel chemotherapy failed. This randomized, double­blind, placebo­controlled, phase III trial was carried out at 68 medical centers in Japan. Patients were randomly assigned at a 2:1 ratio to receive PPV or placebo. Four of 12 warehouse peptides selected based on pre­existing peptide­specific immunoglobulin G levels or the corresponding placebo were subcutaneously injected in 6 doses weekly and then bi­weekly following the maximum of 30 doses until disease progression. The primary end­point was overall survival (OS). Efficacy analyses were performed by the full analysis set. Between August 2013 and April 2016, 310 patients were randomly assigned, and 306 patients were analyzed. Baseline characteristics were balanced between groups. The estimated median OS was 16.1 months [95% confidence interval (CI), 13­18.2] with PPV and 16.9 months (95% CI, 13.1­20.4) with placebo [hazard ratio (HR), 1.04, 95% CI, 0.80­1.37; P=0.77]. Grade ≥3 adverse events were observed in 41% of both groups. The analysis of treatment arm effects among subgroups revealed lower HRs for OS in favor of the PPV arm in patients with <64% neutrophils (HR, 0.55, 95% CI, 0.33­0.93; P=0.03) or ≥26% lymphocytes (HR, 0.70, 95% CI, 0.52­0.92; P=0.02) at baseline. PPV did not prolong OS in HLA­A24­positive patients with CRPC progressing after docetaxel chemotherapy. Subgroup analysis suggested that the patients with a lower proportion of neutrophils or a higher proportion of lymphocytes at baseline can receive survival benefits from PPV treatment.

Early phase II study of mixed 19-peptide vaccine monotherapy for refractory triple-negative breast cancer.

We undertook an early phase II study of mixed 19-peptide cancer vaccine monotherapy for 14 advanced metastatic triple-negative breast cancer (mTNBC) patients refractory to systemic chemotherapy to develop a new type of cancer vaccine. The treatment protocol consisted of a weekly vaccination for 6 weeks, and there were no severe adverse events related to the vaccination throughout the trial. Increase of peptide-specific IgG against the vaccinated human leukocyte antigen-matched peptides, but not against the nonmatched peptides, was positively correlated with overall survival (OS) (P < .01). The median OS was 11.5 or 24.4 months in all 14 patients or the 10 patients who completed the vaccination. The patients with lower C-reactive protein levels or 3 or fewer systemic chemotherapies were favorable candidates for this treatment. Advancement of this therapy to the next stage of study could be warranted based on the safety and immune boosting determined herein (clinical trial registration number: UMIN000014616).

Identification of biomarkers for personalized peptide vaccination in 2,588 cancer patients.

Peptide­based cancer vaccines have failed to provide sufficient clinical benefits in order to be approved in clinical trials since the 1990s. To understand the mechanisms underlying this failure, the present study investigated biomarkers associated with the lower overall survival (OS) among 2,588 patients receiving personalized peptide vaccination (PPV). Survival data were obtained from a database of 2,588 cancer patients including 399 patients with lung, 354 with prostate and 344 with colon cancer. They entered into phase II clinical trials of PPV in which 2 to 4 of 31 warehouse peptides were selected for vaccination on an individual patient basis based on human leukocyte antigen (HLA) class IA­types and pre­existing peptide­specific IgG levels. Higher pre­vaccination neutrophil, monocyte and platelet counts, and lower pre­vaccination lymphocyte and red blood cell counts were inversely associated with OS, with higher sensitivities in the proportions of neutrophils and lymphocytes, respectively. The most potent unfavorable and favorable factors for OS were the median percentage of neutrophils (≥64.8%) or percentage of lymphocytes (≥25.1%) with correlation coefficients (R2) of 0.98 and 0.92, respectively. Higher pre­vaccination levels of c­reactive protein and other inflammatory soluble factors were inversely associated with OS. Pre­vaccination peptide­specific immunity levels had no effect on OS, although lower immune boosting levels were inversely associated with OS. None of the 31 peptides was inversely associated with OS, although a few peptides were positively associated with it. On the whole, the findings of the present study suggested that pre­vaccination inflammatory signatures, but not those of post­vaccination immune induction, were associated with lower clinical benefits of PPV.

Mixed 20-peptide cancer vaccine in combination with docetaxel and dexamethasone for castration-resistant prostate cancer: a randomized phase II trial.

A novel cancer vaccine consisting of 20 mixed peptides (KRM-20) was designed to induce cytotoxic T lymphocytes (CTL) against twelve different tumor-associated antigens. The aim of this phase II trial was to examine whether KRM-20 in combination with docetaxel and dexamethasone enhances the antitumor effects in patients with castration-resistant prostate cancer (CRPC). In this double-blind, placebo-controlled, randomized phase II study, we enrolled chemotherapy-naïve patients with CRPC from ten medical centers in Japan. Eligible patients were randomly assigned 1:1 centrally to receive either KRM-20 combined with docetaxel and dexamethasone (n = 25) or placebo with docetaxel and dexamethasone (n = 26). The primary endpoint was the difference in prostate-specific antigen (PSA) decline between each treatment. The rates of > 50% PSA decline in the two arms were similar (56.5% versus 53.8%; P = 0.851). Human leukocyte antigen (HLA)-matched peptide-specific immunoglobulin G (P = 0.018) and CTL (P = 0.007) responses in the KRM-20 arm significantly increased after treatment. The addition of KRM-20 did not increase toxicity. There were no between-group differences in progression-free or overall survival (OS). The addition of KRM-20 was safe, and similar PSA decline and HLA-matched peptide-specific CTL and IgG responses increased in combination with docetaxel and dexamethasone in CRPC patients. Subgroup analysis suggested that this treatment is favorable for CRPC patients with ≥ 26% lymphocytes or PSA levels of < 11.2 ng/ml, but further clinical trials comparing OS are required.

Immunological consequences following splenectomy in patients with liver cirrhosis.

The immune status in patients with liver cirrhosis is generally impaired due to concomitant hypersplenism. As the spleen is the largest lymphoid organ, deleterious events resulting from splenectomy are of concern in these patients. However, the immunological consequences after splenectomy have not yet been fully elucidated. In the present study, the immune status after splenectomy was comprehensively examined. Splenectomy was performed in 11 patients with liver cirrhosis and hypersplenism, and the immune status in peripheral blood was examined and compared before and at 1, 3 and 6 months after splenectomy. Splenectomy significantly lowered the neutrophil-to-lymphocyte ratio, due to a surge in lymphocytes in the peripheral circulation at 3 and 6 months after splenectomy. The frequency of cluster of differentiation (CD)4+ T cells decreased after splenectomy, whereas the frequency of CD8+ T cells increased. Notably, the frequencies of the naïve and central memory subsets of CD4+ and CD8+ T cells decreased, whereas those of the effector memory subset trended upward. In addition, the frequencies of other immune cells such as γδ T cells, natural killer T cells and natural killer cells transiently increased, while inhibitory cells such as regulatory T cells and myeloid-derived suppressor cells significantly decreased. T-cell responses to viral- and tumor-associated antigens increased after splenectomy in five of eight and two of five patients, respectively. To the best of our knowledge, this is the first study to precisely examine the drastic changes of immunological phenotypes in peripheral blood after splenectomy in patients with cirrhosis. Our findings suggested that splenectomy in patients with cirrhosis may ameliorate the impaired immune status, possibly by reducing suppressive cells and enhancing the effector cell population and function, which could, at least in part, explain the mechanisms responsible for the clinical benefits of splenectomy.

Comparison of Claudin 18.2 expression in primary tumors and lymph node metastases in Japanese patients with gastric adenocarcinoma.

BACKGROUND: The monoclonal antibody zolbetuximab (formerly IMAB362), which is being developed as a potential treatment for gastric cancer (GC), targets Claudin 18.2 (CLDN18.2), a GC biomarker. This study aimed to determine the prevalence of CLDN18.2 in primary tumors and lymph node (LN) metastases of Japanese patients with GC. METHODS: CLDN18.2 expression was investigated in tissue samples from patients with gastric adenocarcinoma archived at Kurume University Medical Center, Japan, between 2000 and 2012. Expression of CLDN18.2 in tumor samples was evaluated by immunohistochemistry using the same detection antibody (43-14A) and assay used in the FAST clinical trial (NCT01630083), a phase 2 randomized trial that compared the safety and antitumor activity of the zolbetuximab-chemotherapy combination with chemotherapy alone. Samples showing any specific staining with ≥1+ intensity were defined as CLDN18.2-positive. RESULTS: Of 263 samples analyzed (134 primary gastric tumors and corresponding LN metastases; 128 primary tumors only; one LN metastases only), CLDN18.2 was detected in 87% (n = 228/262) of all primary tumors and 80% (n = 108/135) of LN metastases. Moderate-to-strong CLDN18.2 expression (≥2+ membrane staining intensity in ≥40% of tumor cells [FAST eligibility criterion]) was observed in 52% (n = 135/262) of primary tumors and 45% (n = 61/135) of (LN) metastases. CLDN18.2 expression was significantly higher in GCs of the diffuse histological subtype per Lauren classification and in high grade (G3) tumors. CONCLUSIONS: The high prevalence of CLDN18.2 among Japanese patients with GC supports the therapeutic assessment of zolbetuximab in this population.

A randomized, double-blind, phase III trial of personalized peptide vaccination for recurrent glioblastoma.

BACKGROUND: We conducted a phase III trial of personalized peptide vaccination (PPV) for human leukocyte antigen (HLA)-A24+ recurrent glioblastoma to develop a new treatment modality. METHODS: We randomly assigned 88 recurrent glioblastoma patients to receive PPV (n = 58) or the placebo (n = 30) at a 2-to-1 ratio. Four of 12 warehouse peptides selected based on preexisting peptide-specific immunoglobulin G levels or the corresponding placebos were injected 1×/week for 12 weeks. RESULTS: Our trial met neither the primary (overall survival [OS]) nor secondary endpoints. Unfavorable factors for OS of 58 PPV patients compared with 30 placebo patients were SART2-93 peptide selection (n = 13 vs 8, hazard ratio [HR]: 15.9), ≥70 years old (4 vs 4, 7.87), >70 kg body weight (10 vs 7, 4.11), and performance status (PS)3 (8 vs 2, 2.82), respectively. Consequently, the median OS for PPV patients without SART2-93 selection plus one of these 3 favorable factors (<70 y old, ≤70 kg, or PS0-2) was significantly longer than that for the corresponding placebo patients (HR: 0.49, 0.44, and 0.51), respectively. Preexisting immunity against both all 12 warehouse peptides besides SART2-93 and the other cytotoxic T lymphocyte epitope peptides was significantly depressed in the patients with SART2-93 selection (n = 21) compared with that of the patients without SART2-93 selection (n = 67). Biomarkers correlative for favorable OS of the PPV patients were a lower percentage of CD11b+CD14+HLA-DRlow immunosuppressive monocytes and a higher percentage of CD4+CD45RA- activated T cells, the intermediate levels of chemokine C-C ligand 2 (CCL2), vascular endothelial growth factor, interleukin (IL)-6, IL-17, or haptoglobin, respectively. CONCLUSION: This phase III trial met neither the primary nor secondary endpoints.

Survival analysis of multiple peptide vaccination for the selection of correlated peptides in urological cancers.

Peptide-based cancer vaccines are able to induce strong immune responses, but their clinical results are unsatisfactory. To determine clinically correlated peptides, we analyzed survival data from urological cancer patients treated by personalized peptide vaccination (PPV), in which different multiple peptides were used for individual patients based on human leukocyte antigen (HLA) type and pre-existing immunity. Survival data were obtained from a database of 265 urological cancer patients treated in 5 clinical PPV trials comprising 154 patients with castration-resistant prostate cancer (CRPC) and 111 patients with advanced urothelial cancer (UC). Expression of tumor-associated antigens (TAA) was evaluated in 10 prostate cancer tissues, 4 metastatic lymph nodes from prostate cancer, and 10 UC tissues using immunohistochemical staining. Clinical efficacy of individual peptides for overall survival was evaluated by the Cox proportional hazards regression model. All TAA coding candidate peptides used in PPV treatment were expressed in tumor cells from prostate cancer and UC samples except for p56Lck in both, and prostate-specific antigen (PSA), prostatic acid phosphatase (PAP) and prostate-specific membrane antigen (PSMA) in the UC samples. Patients with the following peptides had a significantly longer survival than patients without the peptides (hazard ratio <1.0, 95% confidence intervals <1.0 and P < .05): SART3-109, PTHrP-102, HNPRL-140, SART3-302 and Lck-90 in CRPC patients, and EGF-R-800, Lck-486, PSMA-624, CypB-129 and SART3-734 in advanced UC patients, respectively. Correlated peptides selected using both survival data and pre-existing immunity for PPV treatment may enhance the clinical benefits for urological cancer patients.

Antitumor activity of antibody against cytotoxic T lymphocyte epitope peptide of lymphocyte-specific protein tyrosine kinase.

Although humoral responses against CTL epitope peptides from lymphocyte-specific protein tyrosine kinase (Lck) antigen have been observed in the majority of healthy donors and cancer patients, the biological activity of the antibody has not been determined. We investigated the biological activity of mAb against CTL epitope peptide of Lck antigen at positions 486-494 (anti-Lck-486 mAb). This mAb induced dendritic cell maturation from murine bone marrow cells by the immune complex form in vitro, and inhibited tumor growth in association with a suppression of tumor-infiltrating T cells, including T regulatory cells in a murine model using female BALB/cCrlCrlj mice (H-2Kd ). More potent tumor inhibition was observed when this mAb was given prior to peptide vaccination. These results may help to unveil the biological activity of anti-Lck peptide antibodies against CTL epitope peptides.

Personalized peptide vaccination as second-line treatment for metastatic upper tract urothelial carcinoma.

This study investigated the applicability of personalized peptide vaccination (PPV) for patients with metastatic upper tract urothelial cancer (mUTUC) after failure of platinum-based chemotherapy. In this single arm, open-label, phase II clinical trial, patients with mUTUC received PPV at a single institution. Personalized peptide vaccination treatment used a maximum of four peptides chosen from 27 candidate peptides according to human leukocyte antigen types and peptide-reactive IgG titers, for six s.c. injections weekly as one cycle. The safety of PPV, as well as its influence on host immunity and effect on overall survival were assessed. Forty-eight patients were enrolled in this study. Personalized peptide vaccinations were well tolerated without severe adverse events. Median survival time was 7.3 months (95% confidence interval [CI], 5.3-13.1) with 13.0 months for patients receiving combined salvage chemotherapy (95% CI, 5.7-17.5) and 4.5 months for patients receiving PPV alone (95% CI, 1.7-10.1) (P = 0.080). Patients with positive CTL responses showed a significantly longer survival than patients with negative CTL responses (hazard ratio, 0.37; 95% CI, 0.16-0.85; P = 0.019). Multivariate Cox regression analysis showed that lower numbers of Bellmunt risk factors and lower levels of B-cell activating factor were significantly associated with favorable overall survival for patients under PPV treatment. This study indicated that PPV for patients with mUTUC after failure of platinum-based chemotherapy induced substantial peptide-specific CTL responses without severe adverse events and has the potential to prolong survival when combined with salvage chemotherapy. UMIN Clinical Trials Registry ID: 000001854.

Immunological efficacy of herbal medicines in prostate cancer patients treated by personalized peptide vaccine.

This randomized phase II study investigated the immunological efficacy of herbal medicines (HM) using Hochu-ekki-to and Keishi-bukuryo-gan in combination with personalized peptide vaccination (PPV) for castration-resistant prostate cancer (CRPC). Seventy patients with CRPC were assigned to two arms; PPV plus HM or PPV alone. Two to four peptides were chosen from 31 peptides derived from cancer antigens for a s.c. injection of PPV given eight times according to the patient's human leukocyte antigen type and levels of antigen-specific IgG titer before PPV treatment. Peptide-specific CTL, IgG, regulatory T cells (Treg), monocytic myeloid-derived suppressor cells (Mo-MDSC), and interleukin-6 (IL-6) responses were measured before and at the eighth vaccination. Clinical outcomes were also analyzed. Combination therapy of PPV with HM was well tolerated without severe adverse events. There was no significant change in antigen-specific IgG, CTL, Treg or clinical outcomes. Combination therapy of PPV with HM stabilized the frequency of Mo-MDSC (1.91%-1.92%, P = 0.96) and serum levels of IL-6 (19.2 pg/mL to 16.1 pg/mL, P = 0.63) during the treatment. In contrast, the frequency of Mo-MDSC and levels of IL-6 in the PPV-alone group were significantly increased (0.91%-1.49% for Mo-MDSC and 9.2 pg/mL to 19.4 pg/mL for IL-6, respectively). These results suggest that the combined use of HM has the potential to prevent the immunosuppression induced by Mo-MDSC or IL-6 during immunotherapy. More research is needed to validate the findings of the present study.

Clinical development of immunotherapy for prostate cancer.

Prostate cancer is the most common cancer in men, and the second leading cause of cancer-related death in Western countries. Prostate cancer-related death occurs in patients with metastatic castration-resistant prostate cancer. Although several new drugs for castration-resistant prostate cancer have been approved, each of these has prolonged survival by just a few months. Consequently, new therapies are sorely needed. Recently, it has been recognized that immunotherapy is an effective treatment for prostate cancer patients. Several strategies, such as cancer vaccines and immune checkpoint inhibitors, have been investigated in clinical studies for prostate cancer patients. In the present review, the results of the most recent clinical studies investigating immunotherapy in prostate cancer patients are reported, and the future clinical development of immunotherapy for prostate cancer is discussed.

Feasibility study of personalized peptide vaccination for hepatocellular carcinoma patients refractory to locoregional therapies.

Overall survival of patients with hepatocellular carcinoma (HCC) refractory to locoregional therapy is dismal, even following treatment with sorafenib, a multikinase inhibitor. To develop a more efficacious treatment, we undertook a feasibility study of personalized peptide vaccination (PPV) for HCC, in which the peptides were selected from 31 peptide candidates based on the pre-existing immunity. Twenty-six HCC patients refractory to locoregional therapies (cohort 1) and 30 patients refractory to both locoregional and systemic therapies (cohort 2) were entered into the study. There were no severe adverse events related to PPV except for one injection site reaction. At the end of the first cycle of six vaccinations, successful CTL or IgG boosting was observed in 57% or 46% of patients in cohort 1 and in 54% or 52% of patients in cohort 2, respectively. Successful IgG boosting at the end of the second cycle was observed in the majority of patients tested. Median overall survival was 18.7 months (95% confidence interval, 12.2-22.5 months) in cohort 1, and 8.5 months (95% confidence interval, 5.9-12.2 months) in cohort 2. Based on the higher rates of immune boosting and the safety profile of PPV, further clinical studies of PPV would be warranted for patients with HCC refractory to not only locoregional therapy but also both locoregional and systemic therapies. The protocol of this study was registered with the UMIN Clinical Trials Registry (UMIN000001882 and UMIN000003590).

Plasma Levels of High-Mobility Group Box 1 during Peptide Vaccination in Patients with Recurrent Ovarian Cancer.

High-mobility group box 1 (HMGB1) is a nuclear protein that is known to be secreted into extracellular fluids from injured cells, activated macrophages, and tumor cells. The clinical correlation of circulating HMGB1 levels with various diseases including cancer has been reported. However, there is no information on HMGB1 levels in cancer patients treated with peptide vaccination. In the present study, we investigated the plasma levels of HMGB1 during personalized peptide vaccination in patients with recurrent ovarian cancer. Frozen plasma samples of 39 patients from previously conducted clinical trials were used in this study. HMGB1 levels were decreased after the 1st cycle of vaccination from their prevaccination levels. However, no correlation was observed between HMGB1 and overall survival (OS). The correlation between plasma HMGB1 levels and other biomarker levels was further analyzed by scatter plot, revealing that HMGB1 levels after the 1st cycle of vaccination were significantly correlated with myeloid-derived suppressor cell (MDSC) frequency after the 1st cycle of vaccination (r = 0.357, p = 0.032). Chi-square test showed that epitope spreading was significantly related with changes of HMGB1 (p = 0.030). These results suggest that plasma HMGB1 is a possible biomarker for cancer vaccine therapy, although direct correlation with OS has not been obtained. This trial is registered with Clinical Trial Registry under trial numbers UMIN000003083 and UMIN000001482.

Enhancement of humoral and cell mediated immune response to HPV16 L1-derived peptides subsequent to vaccination with prophylactic bivalent HPV L1 virus-like particle vaccine in healthy females.

Currently prophylactic HPV16/18 L1 virus-like particle (VLP) vaccines are employed with great success for the prevention of HPV infection. However, limited information is available regarding the immune responses against human papillomavirus (HPV) 16/18 L1 subsequent to HPV16/18 L1 VLP vaccination, primarily due to the lack of widely used assays for immune monitoring. The aim of the present study was to identify HPV16 L1-derived B and T cell epitopes for monitoring the immune responses after HPV16/18 L1 VLP vaccination in healthy females. The levels of immunoglobulin G (IgG), IgE, IgA and IgM reactive to HPV16 L1-derived peptides were measured by multiplex bead suspension assay. Following detailed B cell epitope mapping, T cell responses specific to HPV16 L1-derived peptides were evaluated by an IFN-γ ELISPOT assay. The levels of IgG, IgM and IgA reactive to 20-mer peptides (PTPSGSMVTSDAQIFNKPYW) at positions 293-312 and 300-319 of HPV16 L1 were significantly increased in the plasma after 2, 7, and 12 months after first vaccination. Detailed epitope mapping identified the amino acid sequence (TSDAQIFNKP) at position 301-310 of HPV16 L1 as an immunogenic B cell epitope. In addition, T cell responses to an HLA-A2- and HLA-A24-restricted epitope (QIFNKPYWL) at position 305-313 of HPV16 L1 were increased following immunization, suggesting that the HPV16/18 L1-VLP vaccination as able to induce specific immune responses in T and B cells simultaneously. The identified B and T cell epitopes may be useful as a biomarker for monitoring the immune responses subsequent to HPV16/18 L1 VLP vaccination. Thus, the present study may provide novel information to improve the understanding of the immune responses to HPV16 L1.