New gorilla adenovirus vaccine vectors induce potent immune responses and protection in a mouse malaria model

The tumor microenvironment state associates with response to HPV therapeutic vaccination in patients with respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a rare, debilitating neoplastic disorder caused by chronic infection with human papillomavirus (HPV) type 6 or 11 and characterized by growth of papillomas in the upper aerodigestive tract. There is no approved medical therapy, and patients require repeated debulking procedures to maintain voice and airway function. PRGN-2012 is a gorilla adenovirus immune-therapeutic capable of enhancing HPV 6/11-specific T cell immunity. This first-in-human, phase 1 study (NCT04724980) of adjuvant PRGN-2012 treatment in adult patients with severe, aggressive RRP demonstrates the overall safety and clinically meaningful benefit observed with PRGN-2012, with a 50% complete response rate in patients treated at the highest dose. Responders demonstrate greater expansion of peripheral HPV-specific T cells compared with nonresponders. Additional correlative studies identify an association between reduced baseline papilloma HPV gene expression, greater interferon responses and expression of CXCL9 and CXCL10, and greater papilloma T cell infiltration in responders. Conversely, nonresponders were characterized by greater HPV and CXCL8 gene expression, increased neutrophilic cell infiltration, and reduced T cell papilloma infiltration. These results suggest that papilloma HPV gene expression may regulate interferon signaling and chemokine expression profiles within the tumor microenvironment that cooperate to govern clinical response to therapeutic HPV vaccination in patients with respiratory papillomatosis.

Alpha-1 antitrypsin deficiency: current therapy and emerging targets

INTRODUCTION

Alpha1 antitrypsin deficiency (AATD), a common hereditary disorder affecting mainly lungs, liver and skin has been the focus of some of the most exciting therapeutic approaches in medicine in the past 5 years. In this review, we discuss the therapies presently available for the different manifestations of AATD and new therapies in the pipeline.

AREAS COVERED

We review therapeutic options for the individual lung, liver and skin manifestations of AATD along with approaches which aim to treat all three. Along with this renewed interest in treating AATD come challenges. How is AAT best delivered to the lung? What is the desired level of AAT in the circulation and lungs which therapeutics should aim to provide? Will treating the liver disease increase the potential for lung disease? Are there treatments to target the underlying genetic defect with the potential to prevent all aspects of AATDrelated disease?

EXPERT OPINION

With a relatively small population able to participate in clinical studies, increased awareness and diagnosis of AATD is urgently needed. Better, more sensitive clinical parameters will assist in the generation of acceptable and robust evidence of therapeutic effect for current and emerging treatments.

Preclinical study of a novel therapeutic vaccine for recurrent respiratory papillomatosis

Activation of antigen-specific T-lymphocyte responses may be needed to cure disorders caused by chronic infection with low-risk human papillomavirus (lrHPV). Safe and effective adjuvant therapies for such disorders are needed. The safety and efficacy of a novel gorilla adenovirus vaccine expressing a protein designed to elicit immune responses directed against HPV6 and HPV11, PRGN-2012, was studied using in vitro stimulation of T lymphocytes from patients with recurrent respiratory papillomatosis, in vivo vaccination studies, and therapeutic studies in mice bearing tumors expressing lrHPV antigen. PRGN-2012 treatment induces lrHPV antigen-specific responses in patient T lymphocytes. Vaccination of wild-type mice induces E6-specific T-lymphocyte responses without toxicity. In vivo therapeutic vaccination of mice bearing established HPV6 E6 expressing tumors results in HPV6 E6-specific CD8+ T-lymphocyte immunity of sufficient magnitude to induce tumor growth delay. The clinical study of PRGN-2012 in patients with disorders caused by chronic infection with lrHPV is warranted.

Characterization of recombinant gorilla adenovirus HPV therapeutic vaccine PRGN-2009

There are approximately 44,000 cases of human papillomavirus-associated (HPV-associated) cancer each year in the United States, most commonly caused by HPV types 16 and 18. Prophylactic vaccines successfully prevent healthy people from acquiring HPV infections via HPV-specific antibodies. In order to treat established HPV-associated malignancies, however, new therapies are necessary. Multiple recombinant gorilla adenovirus HPV vaccine constructs were evaluated in NSG-β2m-/- peripheral blood mononuclear cell-humanized mice bearing SiHa, a human HPV16+ cervical tumor, and/or in the syngeneic HPV16+ TC-1 model. PRGN-2009 is a therapeutic gorilla adenovirus HPV vaccine containing multiple cytotoxic T cell epitopes of the viral oncoproteins HPV 16/18 E6 and E7, including T cell enhancer agonist epitopes. PRGN-2009 treatment reduced tumor volume and increased CD8+ and CD4+ T cells in the tumor microenvironment of humanized mice bearing the human cervical tumor SiHa. PRGN-2009 monotherapy in the syngeneic TC-1 model also reduced tumor volumes and weights, generated high levels of HPV16 E6-specific T cells, and increased multifunctional CD8+ and CD4+ T cells in the tumor microenvironment. These studies provide the first evaluation to our knowledge of a therapeutic gorilla adenovirus HPV vaccine, PRGN-2009, showing promising preclinical antitumor efficacy and induction of HPV-specific T cells, along with the rationale for its evaluation in clinical trials.

Combination Therapies for HPV-Associated Malignancies

Human papillomavirus (HPV)-associated malignancies cause almost all cases of cervical cancer in women, and a significant percentage of head and neck cancer, together totaling almost 5% of the global cancer burden, and representing an important public health issue. The approval and use of two prophylactic HPV vaccines, Gardasil® and Cervarix®, have significantly decreased infections with HPV, but unfortunately, prophylactic vaccination does not treat established infections or malignancies resulting from HPV. Therefore, therapies for HPV-associated malignancies are necessary to improve the quality of life and survival in patients with these diseases. This review will detail new combinations of therapies in clinical development for HPV-associated malignancies.

Advances in Alpha-1 Antitrypsin Gene Therapy

AAT (alpha-1 antitrypsin) deficiency (AATD), characterized by low levels of circulating serine protease inhibitor AAT, results in emphysematous destruction of the lung. Inherited serum deficiency disorders, such as hemophilia and AATD, have been considered ideal candidates for gene therapy. Although viral vector-meditated transduction of the liver has demonstrated utility in hemophilia, similar success has not been achieved for AATD. The challenge for AAT gene therapy is achieving protective levels of AAT locally in the lung and mitigating potential liver toxicities linked to systemically administered viral vectors. Current strategies with ongoing clinical trials involve different routes of adeno-associated virus administrations, such as intramuscular and intrapleural injections, to provide consistent therapeutic levels from nonhepatic organ sites. Nevertheless, exploration of alternative methods of nonhepatic sourcing of AAT has been of great interest in the field. In this regard, pulmonary endothelium-targeted adenovirus vector could be a key technical mandate to achieve local augmentation of AAT within the lower respiratory tract, with the potential benefit of circumventing liver toxicities. In addition, incorporation of the CRISPR/Cas9 (CRISPR-associated protein 9) nuclease system into gene-delivery technologies has provided adjunctive technologies that could fully realize a one-time treatment for sustained, lifelong expression of AAT in patients with AATD. This review will focus on the adeno-associated virus- and adenoviral vector-mediated gene therapy strategies for the pulmonary manifestations of AATD and show that endeavoring to use genome-editing techniques will advance the current strategy to one fully compatible with direct human translation.

Non-Human Primate-Derived Adenoviruses for Future Use as Oncolytic Agents?

Non-human primate (NHP)-derived adenoviruses have formed a valuable alternative for the use of human adenoviruses in vaccine development and gene therapy strategies by virtue of the low seroprevalence of neutralizing immunity in the human population. The more recent use of several human adenoviruses as oncolytic agents has exhibited excellent safety profiles and firm evidence of clinical efficacy. This proffers the question whether NHP-derived adenoviruses could also be employed for viral oncolysis in human patients. While vaccine vectors are conventionally made as replication-defective vectors, in oncolytic applications replication-competent viruses are used. The data on NHP-derived adenoviral vectors obtained from vaccination studies can only partially support the suitability of NHP-derived adenoviruses for use in oncolytic virus therapy. In addition, the use of NHP-derived adenoviruses in humans might be received warily given the recent zoonotic infections with influenza viruses and coronaviruses. In this review, we discuss the similarities and differences between human- and NHP-derived adenoviruses in view of their use as oncolytic agents. These include their genome organization, receptor use, replication and cell lysis, modulation of the host’s immune responses, as well as their pathogenicity in humans. Together, the data should facilitate a rational and data-supported decision on the suitability of NHP-derived adenoviruses for prospective use in oncolytic virus therapy.

A New Gorilla Adenoviral Vector with Natural Lung Tropism Avoids Liver Toxicity and Is Amenable to Capsid Engineering and Vector Retargeting

In the aggregate, our mouse studies suggest that GAd is a promising gene therapy vector that utilizes lung ECs as a source of therapeutic payload production and a highly desirable toxicity profile. Further genetic engineering of the GAd capsid holds the promise of in vivo vector tropism modification and targeting.

Human adenoviruses have many attractive features for gene therapy applications. However, the high prevalence of preexisting immunity against these viruses in general populations worldwide has greatly limited their clinical utility. In addition, the most commonly used human adenovirus, human adenovirus subgroup C serotype 5 (HAd5), when systemically administered, triggers systemic inflammation and toxicity, with the liver being the most severely affected organ. Here, we evaluated the utility and safety of a new low-seroprevalence gorilla adenovirus (GAd; GC46) as a gene transfer vector in mice. Biodistribution studies revealed that systemically administered GAd had a selective and robust lung endothelial cell (EC) tropism with minimal vector expression throughout many other organs and tissues. Administration of a high dose of GAd accomplished extensive transgene expression in the lung yet elicited no detectable inflammatory histopathology in this organ. Furthermore, GAd, unlike HAd5, did not exhibit hepatotropism or induce liver inflammatory toxicity in mice, demonstrating the exceptional safety profile of the vector vis-à-vis systemic utility. We further demonstrated that the GAd capsid fiber shared the flexibility of the HAd5 equivalent for permitting genetic modification; GAd with the pan-EC-targeting ligand myeloid cell-binding peptide (MBP) incorporated in the capsid displayed a reduced lung tropism and efficiently retargeted gene expression to vascular beds in other organs.

IMPORTANCE In the aggregate, our mouse studies suggest that GAd is a promising gene therapy vector that utilizes lung ECs as a source of therapeutic payload production and a highly desirable toxicity profile. Further genetic engineering of the GAd capsid holds the promise of in vivo vector tropism modification and targeting.

Therapeutic Vaccines for HPV-Associated Malignancies

Human papillomavirus (HPV)-related malignancies are responsible for almost all cases of cervical cancer in women, and over 50% of all cases of head and neck carcinoma. Worldwide, HPV-positive malignancies account for 4.5% of the global cancer burden, or over 600,000 cases per year. HPV infection is a pressing public health issue, as more than 80% of all individuals have been exposed to HPV by age 50, representing an important target for vaccine development to reduce the incidence of cancer and the economic cost of HPV-related health issues. The approval of Gardasil^® as a prophylactic vaccine for high-risk HPV 16 and 18 and low-risk HPV6 and 11 for people aged 11-26 in 2006, and of Cervarix^® in 2009, revolutionized the field and has since reduced HPV infection in young populations. Unfortunately, prophylactic vaccination does not induce immunity in those with established HPV infections or HPV-induced neoplasms, and there are currently no therapeutic HPV vaccines approved by the US Food and Drug Administration. This comprehensive review will detail the progress made in the development of therapeutic vaccines against high-risk HPV types, and potential combinations with other immunotherapeutic agents for more efficient and rational designs of combination treatments for HPV-associated malignancies.

A Single and Un-Adjuvanted Dose of a Chimpanzee Adenovirus-Vectored Vaccine against Chikungunya Virus Fully Protects Mice from Lethal Disease

The mosquito-borne chikungunya virus (CHIKV) has become a major global health problem. Upon infection, chikungunya fever (CHIKF) can result in long-term joint pain and arthritis, and despite intense research, no licensed vaccine for CHIKV is available. We have developed two recombinant chimpanzee adenovirus-vectored vaccines (ChAdOx1) that induce swift and robust anti-CHIKV immune responses with a single dose, without the need for adjuvants or booster vaccines. Here, we report the vaccines’ protective efficacies against CHIKV infection in a lethal A129 mouse model. Our results indicate that a single, un-adjuvanted ChAdOx1 Chik or ChAdOx1 Chik ΔCap dose provided complete protection against a lethal virus challenge and prevented CHIKV-associated severe inflammation. These candidate vaccines supported survival equal to the attenuated 181/25 CHIKV reference vaccine but without the vaccine-related side effects, such as weight loss. Vaccination with either ChAdOx1 Chik or ChAdOx1 Chik ΔCap resulted in high titers of neutralizing antibodies that are associated with protection, indicating that the presence of the capsid within the vaccine construct may not be essential to afford protection under the conditions tested. We conclude that both replication-deficient ChAdOx1 Chik vaccines are safe even when used in A129 mice and afford complete protection from a lethal challenge.

A Gorilla Adenovirus-Based Vaccine against Zika Virus Induces Durable Immunity and Confers Protection in Pregnancy

The teratogenic potential of Zika virus (ZIKV) has made the development of an effective vaccine a global health priority. Here, we generate two gorilla adenovirus-based ZIKV vaccines that encode for pre-membrane (prM) and envelope (E) proteins (GAd-Zvp) or prM and the ectodomain of E protein (GAd-Eecto). Both vaccines induce humoral and cell-mediated immune responses and prevent lethality after ZIKV challenge in mice. Protection is antibody dependent, CD8⁺ T cell independent, and for GAd-Eecto requires the complement component C1q. Immunization of GAd-Zvp induces antibodies against a key neutralizing epitope on domain III of E protein and confers durable protection as evidenced by memory B and long-lived plasma cell responses and challenge studies 9 months later. In two models of ZIKV infection during pregnancy, GAd-Zvp prevents maternal-to-fetal transmission. The gorilla adenovirus-based vaccine platform encoding full-length prM and E genes is a promising candidate for preventing congenital ZIKV syndrome and possibly infection by other flaviviruses.

Immunogenicity and Cross-Reactivity of Rhesus Adenoviral Vectors

Adenovirus (Ad) vectors are being investigated as vaccine candidates, but baseline antivector immunity exists in human populations to both human Ad (HuAd) and chimpanzee Ad (ChAd) vectors. In this study, we investigated the immunogenicity and cross-reactivity of a panel of recently described rhesus adenoviral (RhAd) vectors. RhAd vectors elicited T cells with low exhaustion markers and robust anamnestic potential. Moreover, RhAd vector immunogenicity was unaffected by high levels of preexisting anti-HuAd immunity. Both HuAd/RhAd and RhAd/RhAd prime-boost vaccine regimens were highly immunogenic, despite a degree of cross-reactive neutralizing antibodies (NAbs) between phylogenetically related RhAd vectors. We observed extensive vector-specific cross-reactive CD4 T cell responses and more limited CD8 T cell responses between RhAd and HuAd vectors, but the impact of vector-specific cellular responses was far less than that of vector-specific NAbs. These data suggest the potential utility of RhAd vectors and define novel heterologous prime-boost strategies for vaccine development.

IMPORTANCE To date, most adenoviral vectors developed for vaccination have been HuAds from species B, C, D, and E, and human populations display moderate to high levels of preexisting immunity. There is a clinical need for new adenoviral vectors that are not hindered by preexisting immunity. Moreover, the development of RhAd vector vaccines expands our ability to vaccinate against multiple pathogens in a population that may have received other HuAd or ChAd vectors. We evaluated the immunogenicity and cross-reactivity of RhAd vectors, which belong to the poorly described adenovirus species G. These vectors induced robust cellular and humoral immune responses and were not hampered by preexisting anti-HuAd vector immunity. Such properties make RhAd vectors attractive as potential vaccine vectors.

Profiling the Targets of Protective CD8+ T Cell Responses to Infection

T cells are critical effectors of host immunity that target intracellular pathogens, such as the causative agents of HIV, tuberculosis, and malaria. The development of vaccines that induce effective cell-mediated immunity against such pathogens has proved challenging; for tuberculosis and malaria, many of the antigens targeted by protective T cells are not known. Here, we report a novel approach for screening large numbers of antigens as potential targets of T cells. Malaria provides an excellent model to test this antigen discovery platform because T cells are critical mediators of protection following immunization with live sporozoite vaccines and the specific antigen targets are unknown. We generated an adenovirus array by cloning 312 highly expressed pre-erythrocytic Plasmodium yoelii antigens into adenovirus vectors using high-throughput methodologies. The array was screened to identify antigen-specific CD8⁺ T cells induced by a live sporozoite vaccine regimen known to provide high levels of sterile protection mediated by CD8⁺ T cells. We identified 69 antigens that were targeted by CD8⁺ T cells induced by this vaccine regimen. The antigen that recalled the highest frequency of CD8⁺ T cells, PY02605, induced protective responses in mice, demonstrating proof of principle for this approach in identifying antigens for vaccine development.