Live-attenuated Listeria Monocytogenes Research Articles

ADXS11-001 immunotherapy targeting HPV-E7: Final results from a phase 2 study in Indian women with recurrent cervical cancer.

5610 Background: ADXS11-001 immunotherapy is a live attenuated Listeria monocytogenes (Lm) bioengineered to secrete a HPV-16-E7 fusion protein targeting HPV transformed cells. The Lm vector serves ...

A phase 2 study of live-attenuated listeria monocytogenes cancer immunotherapy (ADXS11-001) in the treatment of persistent or recurrent cancer of the cervix (GOG-0265).

A phase 2 study of live-attenuated listeria monocytogenes cancer immunotherapy (ADXS11-001) in the treatment of persistent or recurrent cancer of the cervix (GOG-0265).

Antimesothelin vaccine CRS-207 plus chemotherapy as front-line treatment for malignant pleural mesothelioma (MPM).

7532 Background: CRS-207 is live-attenuated Listeria monocytogenes engineered to express the tumor-associated antigen mesothelin which is highly expressed in malignant pleural mesothelioma (MPM). C...

A phase 2, randomized trial of GVAX pancreas and CRS-207 immunotherapy versus GVAX alone in patients with metastatic pancreatic adenocarcinoma: Updated results.

177^ Background: Immunotherapy for pancreatic ductal adenocarcinoma (PDA) is likely to require synergistic combinations. One approach is to use heterologous prime boost vaccinations to capitalize on immunostimulatory features of distinct vectors. GVAX is irradiated, GM-CSF-secreting allogeneic pancreatic cell lines given intradermally to elicit a broad antigenic response. Low-dose cyclophosphamide (CY) is given prior to GVAX to inhibit regulatory T-cells. CRS-207 is live-attenuated Listeria monocytogenes (Lm) which expresses mesothelin and stimulates innate and adaptive immunity. In mouse tumor models, Lm/GVAX vaccines are synergistic and in the Phase 1 study of CRS-207, 3 PDA patients who had received prior GVAX lived ≥15 months (mos). Methods: Metastatic PDA patients (ECOG 0-1; adequate organ function) who received or refused ≥1 prior chemotherapy were randomized 2:1 to receive either 2 doses of CY/GVAX followed by 4 doses of CRS-207 (Arm A) or 6 doses of CY/GVAX (Arm B) every 3 weeks. Courses could be repeated. The primary endpoint was to compare overall survival (OS) between the arms. Secondary endpoints were safety, clinical and immune responses. One-sided p-values are reported. Results: 90 patients (Full Analysis Set [FAS]; A: 61, B: 29), of which 51% had received ≥2 chemotherapy regimens for metastatic PDA, were treated. After a median follow-up of 7.8 mos, median OS in FAS was 6.1 vs 3.9 mos (A vs B; HR=0.54, p=0.011). Median OS in patients who received ≥3 doses (per protocol [PP] set: 2 doses of CY/GVAX and ≥1 dose of CRS-207 in A or ≥3 doses of CY/GVAX in B) was 9.7 vs 4.6 mos (A vs B; HR=0.44, p=0.0074). The treatment effect was particularly evident in patients who received ≥2 prior regimens for metastatic PDA with median OS of 5.1 vs 3.7 mos (A vs B; HR=0.34, p=0.001). OS in the PP set was 8.2 vs 4.0 mos (A vs B; HR=0.23, p=0.0003). CA19-9 stabilization was seen in 32% vs 13% of patients (A vs B; p=0.06). Toxicities included local reactions after GVAX and transient fevers, rigors and lymphopenia after CRS-207. Conclusions: CY/GVAX followed by CRS-207 shows extended survival with manageable toxicity in previously-treated metastatic PDA and warrants further study. Clinical trial information: NCT01417000.

A Phase IIb, randomized, multicenter study of the efficacy of GVAX pancreas vaccine and CRS-207 compared to chemotherapy or to CRS-207 alone...

Background: A heterologous prime-boost vaccination strategy using GVAX pancreas vaccine and CRS-207 is showing promise in patients with metastatic pancreatic adenocarcinoma (PDA). GVAX is composed of lethally-irradiated, allogeneic pancreatic cancer cells modified to express GM-CSF and induces a broad response against multiple tumor antigens. GVAX is given with low-dose cyclophosphamide (CY) to inhibit regulatory T cells. CRS-207 is live-attenuated Listeria monocytogenes engineered to express the tumor-associated antigen mesothelin. CRS-207 boosts responses against mesothelin and is unique in its capacity to stimulate both innate and adaptive immunity by activating T cells and NK cells. In a recently completed Phase II study, the CY/GVAX plus CRS-207 combination resulted in statistically-significant improvement of overall survival (OS) compared to CY/GVAX alone (Le, GI ASCO 2014). Methods: This is a Phase IIb study comparing CY/GVAX and CRS-207 to chemotherapy or to CRS-207 alone in adults with previously-treated metastatic PDA. Subjects will be enrolled in two cohorts: 150 subjects into a primary cohort of patients with at least two prior treatment regimens for metastatic disease (3rd+ line) and 90 subjects into an exploratory cohort of patients with only one prior treatment regimen for metastatic disease (2nd line). Subjects will be randomized in a 1:1:1 ratio to receive either 2 doses of CY/GVAX and 4 doses of CRS-207 (Arm A), 6 doses of CRS-207 (Arm B) or physician's choice of select single-agent chemotherapy (Arm C). The primary objective is to compare OS in the primary cohort between Arms A and C. Secondary/exploratory objectives include: comparison of OS in both primary and exploratory cohorts between all treatment arms, assessment of safety and clinical responses (tumor assessments and CA19-9 levels) and correlation of Lm- and mesothelin-specific T cell and other immunological responses with OS, progression-free survival and best overall response. (Sponsor: Aduro BioTech, Inc.; NCT02004262).

ADXS11-001 immunotherapy targeting HPV-E7: updated survival and safety data from a phase 2 study in Indian women with recurrent/refractory cervical cancer

Meeting abstracts ADXS11-001 immunotherapy is a live attenuated Listeria monocytogenes ( Lm ) bioengineered to secrete a HPV-16-E7 fusion protein targeting HPV transformed cells. The Lm vector serves as its own adjuvant and infects antigen presenting cells (APC) where it cross presents, stimulating

A phase II study of live-attenuated Listeria monocytogenes immunotherapy (ADXS11-001) in the treatment of persistent or recurrent cancer of the cervix (GOG-0265).

TPS3121 Background: This is a GOG/NCI-sponsored phase II study (NCT01266460, GOG 0265) of ADXS11-001 in patients with persistent or recurrent cancer of the cervix. ADXS11-001 is a live attenuated Listeria monocytogenes (Lm) immunotherapy bioengineered to secret a HPV-E7 fusion protein targeting HPV-E7 transformed cells. A previous phase I dose escalation study determined the safety of ADXS11-001 in patients with late stage cervical cancer (Maciag PA. Vaccine. 2009 Jun 18;27(30):3975-83). The primary objectives of this study are to evaluate the tolerability and safety of ADXS11-001, and to assess the activity of ADXS11-001 in patients with persistent or recurrent cancer of the cervix. Secondary objectives are progression-free survival, overall survival and objective tumor response. Methods: Patient eligibility criteria: Females age ≥ 18 years with persistent or recurrent squamous or non-squamous cell carcinoma, adenosquamous carcinoma, or adenocarcinoma of the cervix with documented disease progression (disease not amenable to curative therapy). Patients must have measurable disease as defined by RECIST 1.1; at least one “target lesion” as defined by RECIST 1.1; have had one prior systemic chemotherapeutic regimen for management of their disease; have adequate organ function and must be free of active infection and not on antibiotics. This protocol is a 2-stage design with 12-month survival as the primary endpoint and with a planned sample size of up to 67 patients. Patients will receive ADXS11-001 at a dose of 1x109 CFU on Day 1 and repeat every 28 days for 3 total doses in the absence of disease progression or unacceptable toxicity, with each dose followed at 72 hours by a 7 day course of ampicillin, 500 mg QID. Tumor tissue and serum samples may be collected periodically for translational research. After completion of study treatment, patients are followed every 3 months for 2 years and then every 6 months for 3 years. As of January 31, 2013, enrollment has been completed in the 6-patient safety lead-in portion of the study. Clinical trial information: NCT01266460.

ADXS11-001 immunotherapy targeting HPV-E7: Preliminary survival data from a P2 study in Indian women with recurrent/refractory cervical cancer.

5529 Background: ADXS11-001 immunotherapy is a live attenuated Listeria monocytogenes (Lm) bioengineered to secrete a HPV16-E7 fusion protein targeting HPV transformed cells. The Lm vector serves as its own adjuvant and infects APC where it naturally cross presents, stimulating both MHC class 1 and 2 pathways resulting in specific T-cell immunity to tumors. Here we describe the preliminary survival data associated with ADXS11-001 administration in Lm-LLO-E7-015, a randomized P2 study being conducted in India in 110 patients with recurrent/refractory cervical cancer who have been treated previously with chemotherapy, radiotherapy or both. Methods: Patients were randomized to either 3 doses of ADXS11-001 at 1 x 109 cfu or 4 doses of ADXS11-001 at 1 x 109cfu with cisplatin chemotherapy. Naprosyn and oral promethazine were given as premedications and a course of ampicillin was given 72h after infusion. Patients received CT scans at baseline and 3, 6, 9, 12 and 18 months. The primary endpoint is overall survival. Results: As of February 2013, the trial has completed enrollment and 110 patients have received 264 doses of ADXS11-001. The percentage of patients alive at 6 months is 63% (67/107); at 9 months is 46% (49/106); at 12 months is 34% (30/87) and at 18 months is 15% (8/54). Tumor responses have been observed in both treatment arms with 6 CRs and 6 PRs; 36 additional patients had stable disease > 3 months, for a disease control rate of 44% (48/110). Activity against different high risk HPV strains has been observed. Three serious adverse events and 69 mild-moderate adverse events possibly related/related to ADXS11-001 treatment have been reported in 41% (45/110) of patients. The non-serious adverse events consisted predominately of transient, non-cumulative flu-like symptoms associated with infusion that either resolved on their own or responded to symptomatic treatment. Conclusions: ADXS11-001 can be safely administered to patients with advanced cancer alone and in combination with chemotherapy. ADXS11-001 is well tolerated and presents a predictable and manageable safety profile. Final 12-month OS, updated safety and translational analyses will be presented at the meeting.

CRS-207 vaccine plus chemotherapy as front-line treatment for subjects with malignant pleural mesothelioma (MPM).

TPS7607 Background: CRS-207 is a live-attenuated Listeria monocytogenes (Lm) vaccine expressing the tumor-associated antigen mesothelin which is overexpressed in MPM. CRS-207 was well tolerated and induced Lm- and mesothelin-specific T cell immunity in a phase 1 study in adults with mesothelin-expressing cancers (Le et al., Clin. Cancer Res. 2012). Preclinical and clinical studies suggest that vaccines and chemotherapies work synergistically and augment anti-tumor effectiveness of subsequent chemotherapies. Methods: This phase 1B study is evaluating the safety and induction of mesothelin-specific immune responses by CRS-207 plus chemotherapy with pemetrexed (P) and cisplatin (C) in adults with newly diagnosed, unresectable MPM. Two doses of 1×109colony forming units (CFU) CRSE207 are administered intravenously two weeks apart followed two weeks later by up to six cycles of P (500 mg/m2) and C (75 mg/m2) given every 3 weeks. Two booster vaccinations of CRS-207 are administered three weeks apart 4 weeks after completing PC. Secondary and exploratory endpoints will assess objective tumor response, time to progression, overall survival and immune correlates. This is one of the first trials to assess the synergy between vaccines and chemotherapy in newly diagnosed patients with MPM. Sponsor: Aduro BioTech, Inc. ClinicalTrials.gov ID: NCT01675765. Clinical trial information: NCT01675765.

Interim safety and efficacy analysis of a phase II, randomized study of GVAX pancreas and CRS-207 immunotherapy in patients with metastatic pancreatic cancer.

4040^ Background: GVAX is composed of GM-CSF-secreting allogeneic pancreas cancer cell lines and administered with low-dose cyclophosphamide (CY) to inhibit regulatory T cells. In prior studies, GVAX induced mesothelin-specific T cell responses that correlated with survival. CRS-207 is a live-attenuated Listeria monocytogenes engineered to express human mesothelin. CRS-207 stimulates potent innate and adaptive immunity and has shown synergy with GVAX in mouse tumor models. Anecdotal survival benefit was observed in the CRS-207 phase I study in patients who received prior GVAX. Methods: Patients were enrolled with metastatic pancreatic ductal adenocarcinoma (PDA) who received or refused ≥ 1 prior chemotherapy, had ECOG ≤ 1 and adequate organ function. Patients were randomized 2:1 to receive 2 doses of CY/GVAX followed by 4 doses of CRS-207 (Arm A) or 6 doses of CY/GVAX (Arm B) every 3 weeks. Clinically stable patients were offered additional 20-week courses. The primary endpoint was comparison of OS between treatment arms. Secondary endpoints were to evaluate safety, clinical and immune responses. Results: 90 patients were treated (Arm A: 61, Arm B: 29). As of Jan 2013, 27 patients completed 1 course (A: 24, B: 3) and 17 patients (A: 15, B: 2) initiated a 2nd course. Median age was 63. Median number of prior regimens was 3. No treatment-related serious adverse events (SAEs) or unexpected toxicities were observed. The most frequent Grade (G) 3/4 related toxicities were fever, lymphopenia, hypophosphatemia, elevated liver enzymes, and fatigue following CRS-207 in <5% of subjects. Of 51 patients evaluated post-treatment, 34% had stable disease in Arm A vs. 19% in Arm B. OS for all patients treated was 6 months in Arm A vs. 3.4 months in Arm B (two-sided, p=0.0114). Conclusions: Combined CY/GVAX pancreas and CRS-207 was generally well-tolerated with no treatment-related SAEs or unexpected G3/4 toxicities. The significant difference in OS between treatment arms met the criteria for early stopping. This indicates that the combination immunotherapy may extend OS for metastatic PDA patients with minimal toxicity and should continue to be developed as an effective therapy. Clinical trial information: NCT01417000.

37. ADXS11-001, mitomycin, 5-FU and radiation for anal cancera A phase I/II study

Background Human papillomavirus (HPV) DNA is present in the majority of squamous cell cancers of the anus. ADXS11–001 immunotherapy is a live attenuated Listeria monocytogenes (Lm) bioengineered to secrete an HPV-16-E7 fusion protein targeting HPV-transformed cells. The Lm vector infects antigen-presenting cells, stimulating both MHC class 1 and 2 pathways resulting in specific T-cell immunity to tumours. The Brown University Oncology Research Group has initiated a phase I/II study evaluating two treatment schedules of ADXS11–001 with standard chemoradiation for anal cancer. Methods: Patients with newly diagnosed anal cancer with a primary tumour >4 cm or lymph node involvement, without distant metastases, are eligible. All patients receive two courses of mitomycin, 5-FU with concurrent radiation (54 Gy in 30 fractions by IMRT). Patients receive four treatments of ADXS11–001, 1 × 109 colony-forming units intravenously once approximately every 28 days. In treatment schedule 1, the first dose is given before chemoradiation and the second to fourth doses are given every 28 days after completion of radiation. In treatment schedule 2, the second dose of ADXS11–001 is administered during chemoradiation. Results: Three patients have been treated with ADXS11–001 and chemoradiation on treatment schedule 1. One patient developed grade 3 chills and one patient experienced grade 2 flu-like symptoms post-infusion, both resolved with symptomatic treatment. Conclusions: ADXS11–001 is a highly novel form of immunotherapy designed to generate an immune response against HPV transformed cells. Accrual is continuing to evaluate safety and efficacy for patients with anal cancer.

ADXS11-011 immunotherapy: Preliminary safety data from two P2 studies in women with CIN 2/3 and with recurrent/refractory cervical cancer.

e15546 Background: ADXS11-001 immunotherapy is a live attenuated Listeria monocytogenes (Lm) bioengineered to secrete a HPV-16-E7 fusion protein targeting HPV transformed cells. The Lm vector serves as its own adjuvant and infects APC where it naturally cross presents, stimulating both MHC class 1 and 2 pathways resulting in specific T-cell immunity to tumors. Here we describe the preliminary survival data associated with ADXS11-001 administration in Lm-LLO-E7-015, a randomized phase II study being conducted in India in 110 patients with recurrent/refractory cervical cancer who have been treated previously with chemotherapy, radiotherapy or both. Methods: Patients are randomized to either 3 doses of ADXS11-001 at 1 x 109 CFU or 4 doses of ADXS11-001 at 1 x 109 CFU with cisplatin chemotherapy. Naprosyn and oral promethazine are given as premedications and a course of ampicillin is given 72h after infusion thereby clearing any residual vector. Patients receive CT scans at baseline and Days 84, 184, 273, 365 and 545. The primary endpoint is 12 month survival. Results: As of January 26, 2012, 88 patients have received 200 doses of ADXS11-001; with the percentage of patients alive at 6 months at 62% (34/55); at 9 months at 41% (15/37) and at 12 months at 40% (6/15). Tumor responses have been observed in both treatment arms with 3 complete responses (elimination of tumor burden) and 4 partial responses (≥30% reduction in tumor burden) by RECIST. One serious (Gr3) adverse event and 77 mild-moderate (Gr 1-2) adverse events possibly related to study treatment have been reported in 35% (31/88) of patients. The non-serious adverse events consisted predominately of transient, non-cumulative flu-like symptoms associated with infusion that responded to symptomatic treatment, or resolved on their own within hours of treatment. Conclusions: This immunotherapy can be safely administered to patients with advanced cancer alone and in combination with chemotherapy. ADXS11-001 is well tolerated and presents a predictable and manageable safety profile. Early signs of clinical benefit merit further investigation. Updated findings will be presented at the meeting.

A phase II study of live-attenuated listeria monocytogenes immunotherapy (ADXS11-001) in the treatment of persistent or recurrent cancer of the cervix (GOG-0265).

TPS5115 Background: This is a GOG/NCI sponsored phase II study (NCT01266460, GOG 0265) of ADXS11-001 in patients with persistent or recurrent cancer of the cervix. ADXS11-001 is a live attenuated Listeria monocytogenes (Lm) immunotherapy bioengineered to secret a HPV E7 fusion protein targeting HPV-E7 transformed cells. A previous phase I dose escalation study determined the safety of ADXS11-001 in patients with late stage cervical cancer (Maciag PA. Vaccine. 2009 Jun 18;27(30):3975-83). The primary objectives of this study are: to evaluate the tolerability and safety of ADXS11-001; and to assess the activity of ADXS11-001 in patients with persistent or recurrent cancer of the cervix. Secondary objectives are progression-free survival, overall survival and objective tumor response. Methods: Patient eligibility criteria: Females age ≥ 18 years with persistent or recurrent squamous or non-squamous cell carcinoma, adenosquamous carcinoma, or adenocarcinoma of the cervix with documented disease progression (disease not amenable to curative therapy). Patients must have measurable disease as defined by RECIST 1.1; at least one “target lesion” as defined by RECIST 1.1; have had one prior systemic chemotherapeutic regimen for management of their disease; have adequate organ function and must be free of active infection and not on antibiotics. This protocol is a Simon 2-stage design with a planned sample size of up to 67 patients. Patients will receive ADXS11-001 at a dose of 1x109 CFU on Day 1 and repeat every 28 days for 3 total doses in the absence of disease progression or unacceptable toxicity, with each dose followed at 72 hours by a 7 day course of ampicillin, 500 mg QID. Tumor tissue and serum samples may be collected periodically for translational research. After completion of study treatment, patients are followed every 3 months for 2 years and then every 6 months for 3 years. This phase II study just began enrolling and as of January 27, 2012, 2 patients have been enrolled.

ADXS11-001 immunotherapy targeting HPV-E7: Preliminary survival data from a phase II study in Indian women with recurrent/refractory cervical cancer.

5106 Background: ADXS11-001 immunotherapy is a live attenuated Listeria monocytogenes (Lm) bioengineered to secrete a HPV-16-E7 fusion protein targeting HPV transformed cells. The Lm vector serves as its own adjuvant and infects APC where it naturally cross presents, stimulating both MHC class 1 and 2 pathways resulting in specific T-cell immunity to tumors. Here we describe the preliminary survival data associated with ADXS11-001 administration in Lm-LLO-E7-015, a randomized phase II study being conducted in India in 110 patients with recurrent/refractory cervical cancer who have been treated previously with chemotherapy, radiotherapy or both. Methods: Patients are randomized to either 3 doses of ADXS11-001 at 1 x 109 CFU or 4 doses of ADXS11-001 at 1 x 109 CFU with cisplatin chemotherapy. Naprosyn and oral promethazine are given as premedications and a course of ampicillin is given 72h after infusion thereby clearing any residual vector. Patients receive CT scans at baseline and Days 84, 184, 273, 365 and 545. The primary endpoint is 12 month survival. Results: As of January 26, 2012, 88 patients have received 200 doses of ADXS11-001; with the percentage of patients alive at 6 months at 62% (34/55); at 9 months at 41% (15/37) and at 12 months at 40% (6/15). Tumor responses have been observed in both treatment arms with 3 complete responses (elimination of tumor burden) and 4 partial responses (≥30% reduction in tumor burden) by RECIST. One serious (Gr3) adverse event and 77 mild-moderate (Gr 1-2) adverse events possibly related to study treatment have been reported in 35% (31/88) of patients. The non-serious adverse events consisted predominately of transient, non-cumulative flu-like symptoms associated with infusion that responded to symptomatic treatment, or resolved on their own within hours of treatment. Conclusions: This immunotherapy can be safely administered to patients with advanced cancer alone and in combination with chemotherapy. ADXS11-001 is well tolerated and presents a predictable and manageable safety profile. Early signs of clinical benefit merit further investigation. Updated findings will be presented at the meeting.

Clinical Development of Listeria monocytogenes–Based Immunotherapies

Active immunotherapy targeting dendritic cells (DCs) has shown great promise in preclinical models and in human clinical trials for the treatment of malignant disease. Sipuleucel-T (Provenge, Dendreon, Seattle, WA), which consists of antigen-loaded dendritic cells (DCs), recently became the first targeted therapeutic cancer vaccine to be approved by the US Food and Drug Administration (FDA). However, ex vivo therapies such as Provenge have practical limitations and elicit an immune response with limited scope. By contrast, live-attenuated Listeria monocytogenes (Lm) naturally targets DCs in vivo and stimulates both innate and adaptive cellular immunity. Lm-based vaccines engineered to express cancer antigens have demonstrated striking efficacy in several animal models and have resulted in encouraging anecdotal survival benefit in early human clinical trials. Two different Lm-based vaccine platforms have advanced into phase II clinical trials in cervical and pancreatic cancer. Future Lm-based clinical vaccine candidates are expected to feature polyvalent antigen expression and to be used in combination with other immunotherapies or conventional therapies such as radiotherapy and chemotherapy to augment efficacy.

Glycolipid Antigens for Treating Hepatic Colorectal Cancer Metastases and Their Effect on the Therapeutic Efficacy of Live Attenuated Listeria monocytogenes

Previous work demonstrated that a subset of natural killer T cells in mice decreased the antitumor efficacy of live attenuated Listeria monocytogenes where the actin A and internalin B genes were genetically deleted (LMD) against murine hepatic colorectal cancer metastases. Therefore, we hypothesized that the use of specific glycolipids known to selectively stimulate natural killer T-cell subsets used alone or co-administered with LMD would increase survival. We found that early or multiple administrations of glycolipids after tumor challenge had a strong impact on survival with or without LMD. Solitary administration or treatment given later was less efficacious but still showed a strong trend toward enhancing the antitumor activity of LMD. These results underscore the potential of glycolipids in the treatment of hepatic metastases and encourage further investigations into the immunomodulation of natural killer T cells to enhance the antitumor activity of LMD.

Lm-LLO-Based Immunotherapies and HPV-Associated Disease

HPV infection is a direct cause of neoplasia and malignancy. Cellular immunologic activity against cells expressing HPV E6 and E7 is sufficient to eliminate the presence of dysplastic or neoplastic tissue driven by HPV infection. Live attenuated Listeria monocytogenes- (Lm-) based immunotherapy (ADXS11-001) has been developed for the treatment of HPV-associated diseases. ADXS11-001 secretes an antigen-adjuvant fusion (Lm-LLO) protein consisting of a truncated fragment of the Lm protein listeriolysin O (LLO) fused to HPV-16 E7. In preclinical models, this construct has been found to stimulate immune responses and affect therapeutic outcome. ADXS11-001 is currently being evaluated in Phase 2 clinical trials for cervical intraepithelial neoplasia, cervical cancer, and HPV-positive head and neck cancer. The use of a live attenuated bacterium is a more complex and complete method of cancer immunotherapy, as over millennia Lm has evolved to infect humans and humans have evolved to prevent and reject this infection over millennia. This evolution has resulted in profound pathogen-associated immune mechanisms which are genetically conserved, highly efficacious, resistant to tolerance, and can be uniquely invoked using this novel platform technology.

Development of a Listeria monocytogenes-based vaccine against hepatocellular carcinoma

Live attenuated Listeria monocytogenes (LM) is a promising bacterial vector able to induce a T-cell response to tumor-associated antigens and demonstrates great potential for use in vaccine development. A novel recombinant LM-based vaccine (Lmdd (LM ΔdalΔdat)-MPFG (multiple peptide fusing genes)) was developed with the ability to express and secrete hepatocellular carcinoma (HCC)-related tumor-associated antigens fragments due to the insertion of hepatitis B virus (HBV)-X protein (HBx)-derived epitopes HBx(52-60) and HBx(140-148), the universal T-helper epitope, alpha-fetoprotein (AFP) epitope AFP(158-166), and melanoma antigen gene (MAGE)-3(271-279) into the HBV core protein. Following immunization with the Lmdd-MPFG vaccine, macrophages exhibited uptake of the bacteria; the vaccine was then nearly cleared 3 days after the first administration. It disappeared even more quickly following subsequent vaccinations. However, recombinant Lmdd-MPFG allowed for the full development of an antitumor response towards the human leukocyte antigen (HLA)-A0201 epitopes of MPFG. Each epitope stimulated an augmented T-cell proliferation and enhanced the supernatant level of interferon (IFN)-γ in vitro. In addition, IFN-γ-producing CD8(+) T cells as well as in vivo cytolytic activity were significantly increased in HLA-A2 transgenic mice. Additionally, the Lmdd-MPFG developed a strong antitumor response, as indicated by the significant resistance of immunized mice to MPFG-positive Hepa1-6 cell challenge in both a prophylactic and therapeutic setting. Tumor regression was accompanied by an enhanced cytotoxic T lymphocyte response and a decrease of regulatory T cells in the tumor. Collectively, these results suggest that utilizing attenuated LM as a vaccine vector, able to carry the MPFG gene, presents a potentially feasible strategy for prevention of HCC.

Prime–boost vaccination with heterologous live vectors encoding SIV gag and multimeric HIV-1 gp160 protein: Efficacy against repeated mucosal R5 clade C SHIV challenges

We sought to induce primate immunodeficiency virus-specific cellular and neutralizing antibody (nAb) responses in rhesus macaques (RM) through a bimodal vaccine approach. RM were immunized intragastrically (i.g.) with the live-attenuated Listeria monocytogenes (Lm) vector Lmdd-BdopSIVgag encoding SIVmac239 gag. SIV Gag-specific cellular responses were boosted by intranasal and intratracheal administration of replication-competent adenovirus ( Ad5hr-SIVgag) encoding the same gag. To broaden antiviral immunity, the RM were immunized with multimeric HIV clade C (HIV-C) gp160 and HIV Tat. SIV Gag-specific cellular immune responses and HIV-1 nAb developed in some RM. The animals were challenged intrarectally with five low doses of R5 SHIV-1157ipEL-p, encoding a heterologous HIV-C Env (22.1% divergent to the Env immunogen). All five controls became viremic. One out of ten vaccinees was completely protected and another had low peak viremia. Sera from the completely and partially protected RM neutralized the challenge virus >90%; these RM also had strong SIV Gag-specific proliferation of CD8 + T cells. Peak and area under the curve of plasma viremia (during acute phase) among vaccinees was lower than for controls, but did not attain significance. The completely protected RM showed persistently low numbers of the α4β7-expressing CD4 + T cells; the latter have been implicated as preferential virus targets in vivo. Thus, vaccine-induced immune responses and relatively lower numbers of potential target cells were associated with protection.

A live attenuated Listeria monocytogenes vaccine vector expressing SIV Gag is safe and immunogenic in macaques and can be administered repeatedly

Listeria monocytogenes (Lm) is known to induce strong cellular immune responses. We constructed a live-attenuated Lm vector, Lmdd-BdopSIVgag, which encodes SIVmac239 gag. Intragastric (i.g.) administration of 3 × 10 12 bacteria to rhesus macaques was safe and induced anti-Gag cellular but no humoral immune responses. Boosting of Gag-specific cellular responses was observed after i.g. administration of Lmdd-BdopSIVgag to previously vaccinated RM despite preexisting anti-Lm immunity shown by lymphoproliferative responses. Surprisingly, anti-Lm cellular responses were also detected in non-vaccinated controls, which may reflect the fact that Lm is a ubiquitous bacterium. The novel, live-attenuated Lmdd-BdopSIVgag may be an attractive platform for oral vaccine delivery.