Adenoviruses isolated from wild gorillas are closely related to human species C viruses

Variation in the affinity of three representative avian adenoviruses for the cellular coxsackievirus and adenovirus receptor

According to previous studies, three representative avian adenoviral strains utilize coxsackievirus-adenovirus receptor (CAR) as a receptor and seem to exhibit diverse binding affinities and modes. Thus, further revealing the exact molecular mechanism underlying the interaction between different FAdVs and the attachment receptor CAR is necessary. In this study, we successfully solved the crystal structure of the FAdV-4 fiber1 knob at 1.6 Å resolution. The interaction between the fibre knob and different domains of CAR was verified by confocal microscopy, coimmunoprecipitation and surface plasmon resonance (SPR) analysis. The fibre knobs of the three representative fowl adenoviruses specifically recognized CAR domain 1 (D1), but the recognition of CAR domain 2 (D2) by chicken embryo lethal orphan (CELO) strains was weak. These results provide insights into the differences in adenovirus‒host cell interactions and have important implications for the exploration of viral invasion mechanisms.

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.

A great ape perspective on the origins and evolution of human viruses

Over the last two decades, the viromes of our closest relatives, the African great apes (AGA), have been intensively studied. Comparative approaches have unveiled diverse evolutionary patterns, highlighting both stable host-virus associations over extended evolutionary timescales and much more recent viral emergence events. In this chapter, we summarize these findings and outline how they have shed a new light on the origins and evolution of many human-infecting viruses. We also show how this knowledge can be used to better understand the evolution of human health in relation to viral infections.

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.

New viral vectors for infectious diseases and cancer

Since the discovery in 1796 by Edward Jenner of vaccinia virus as a way to prevent and finally eradicate smallpox, the concept of using a virus to fight another virus has evolved into the current approaches of viral vectored genetic vaccines. In recent years, key improvements to the vaccinia virus leading to a safer version (Modified Vaccinia Ankara, MVA) and the discovery that some viruses can be used as carriers of heterologous genes encoding for pathological antigens of other infectious agents (the concept of 'viral vectors') has spurred a new wave of clinical research potentially providing for a solution for the long sought after vaccines against major diseases such as HIV, TB, RSV and Malaria, or emerging infectious diseases including those caused by filoviruses and coronaviruses. The unique ability of some of these viral vectors to stimulate the cellular arm of the immune response and, most importantly, T lymphocytes with cell killing activity, has also reawakened the interest toward developing therapeutic vaccines against chronic infectious diseases and cancer. To this end, existing vectors such as those based on Adenoviruses have been improved in immunogenicity and efficacy. Along the same line, new vectors that exploit viruses such as Vesicular Stomatitis Virus (VSV), Measles Virus (MV), Lymphocytic choriomeningitis virus (LCMV), cytomegalovirus (CMV), and Herpes Simplex Virus (HSV), have emerged. Furthermore, technological progress toward modifying their genome to render some of these vectors incompetent for replication has increased confidence toward their use in infant and elderly populations. Lastly, their production process being the same for every product has made viral vectored vaccines the technology of choice for rapid development of vaccines against emerging diseases and for 'personalised' cancer vaccines where there is an absolute need to reduce time to the patient from months to weeks or days. Here we review the recent developments in viral vector technologies, focusing on novel vectors based on primate derived Adenoviruses and Poxviruses, Rhabdoviruses, Paramixoviruses, Arenaviruses and Herpesviruses. We describe the rationale for, immunologic mechanisms involved in, and design of viral vectored gene vaccines under development and discuss the potential utility of these novel genetic vaccine approaches in eliciting protection against infectious diseases and cancer.

Adenovirus Infections in African Humans and Wild Non-Human Primates: Great Diversity and Cross-Species Transmission

Non-human primates (NHPs) are known hosts for adenoviruses (AdVs), so there is the possibility of the zoonotic or cross-species transmission of AdVs. As with humans, AdV infections in animals can cause diseases that range from asymptomatic to fatal. The aim of this study was to investigate the occurrence and diversity of AdVs in: (i) fecal samples of apes and monkeys from different African countries (Republic of Congo, Senegal, Djibouti and Algeria), (ii) stool of humans living near gorillas in the Republic of Congo, in order to explore the potential zoonotic risks. Samples were screened by real-time and standard PCRs, followed by the sequencing of the partial DNA polymerase gene in order to identify the AdV species. The prevalence was 3.3 folds higher in NHPs than in humans. More than 1/3 (35.8%) of the NHPs and 1/10 (10.5%) of the humans excreted AdVs in their feces. The positive rate was high in great apes (46%), with a maximum of 54.2% in chimpanzees (Pan troglodytes) and 35.9% in gorillas (Gorilla gorilla), followed by monkeys (25.6%), with 27.5% in Barbary macaques (Macaca sylvanus) and 23.1% in baboons (seven Papio papio and six Papio hamadryas). No green monkeys (Chlorocebus sabaeus) were found to be positive for AdVs. The AdVs detected in NHPs were members of Human mastadenovirus E (HAdV-E), HAdV-C or HAdV-B, and those in the humans belonged to HAdV-C or HAdV-D. HAdV-C members were detected in both gorillas and humans, with evidence of zoonotic transmission since phylogenetic analysis revealed that gorilla AdVs belonging to HAdV-C were genetically identical to strains detected in humans who had been living around gorillas, and, inversely, a HAdV-C member HAdV type was detected in gorillas. This confirms the gorilla-to-human transmission of adenovirus. which has been reported previously. In addition, HAdV-E members, the most often detected here, are widely distributed among NHP species regardless of their origin, i.e., HAdV-E members seem to lack host specificity. Virus isolation was successful from a human sample and the strain of the Mbo024 genome, of 35 kb, that was identified as belonging to HAdV-D, exhibited close identity to HAdV-D members for all genes. This study provides information on the AdVs that infect African NHPs and the human populations living nearby, with an evident zoonotic transmission. It is likely that AdVs crossed the species barrier between different NHP species (especially HAdV-E members), between NHPs and humans (especially HAdV-C), but also between humans, NHPs and other animal species.

The coxsackievirus and adenovirus receptor: virological and biological beauty

The coxsackievirus and adenovirus receptor (CAR) is an essential multifunctional cellular protein that is only beginning to be understood. CAR serves as a receptor for many adenoviruses, human group B coxsackieviruses, swine vesicular disease virus, and possibly other viruses. While named for its function as a viral receptor, CAR is also involved in cell adhesion, immune cell activation, synaptic transmission, and signaling. Knockout mouse models were first to identify some of these biological functions; however, tissue-specific model systems have shed light on the complexity of different CAR isoforms and their specific activities. Many of these functions are mediated by the large number of interacting proteins described so far, and several new putative interactions have recently been discovered. As antiviral and gene therapy strategies that target CAR continue to emerge, future work poised to understand the biological implications of manipulating CAR in vivo is critical.

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 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.

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.

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

Background

A DNA-human Ad5 (HuAd5) prime-boost malaria vaccine has been shown to protect volunteers against a controlled human malaria infection. The potency of this vaccine, however, appeared to be affected by the presence of pre-existing immunity against the HuAd5 vector. Since HuAd5 seroprevalence is very high in malaria-endemic areas of the world, HuAd5 may not be the most appropriate malaria vaccine vector. This report describes the evaluation of the seroprevalence, immunogenicity and efficacy of three newly identified gorilla adenoviruses, GC44, GC45 and GC46, as potential malaria vaccine vectors.

Results

The seroprevalence of GC44, GC45 and GC46 is very low, and the three vectors are not efficiently neutralized by human sera from Kenya and Ghana, two countries where malaria is endemic. In mice, a single administration of GC44, GC45 and GC46 vectors expressing a murine malaria gene, Plasmodium yoelii circumsporozoite protein (PyCSP), induced robust PyCSP-specific T cell and antibody responses that were at least as high as a comparable HuAd5-PyCSP vector. Efficacy studies in a murine malaria model indicated that a prime-boost regimen with DNA-PyCSP and GC-PyCSP vectors can protect mice against a malaria challenge. Moreover, these studies indicated that a DNA-GC46-PyCSP vaccine regimen was significantly more efficacious than a DNA-HuAd5-PyCSP regimen.

Conclusion

These data suggest that these gorilla-based adenovectors have key performance characteristics for an effective malaria vaccine. The superior performance of GC46 over HuAd5 highlights its potential for clinical development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1911-z) contains supplementary material, which is available to authorized users.

Molecular epidemiological study of adenovirus infecting western lowland gorillas and humans in and around Moukalaba-Doudou National Park (Gabon)

Adenoviruses are widespread in human population as well as in great apes, although the data about the naturally occurring adenovirus infections remain rare. We conducted the surveillance of adenovirus infection in wild western lowland gorillas in Moukalaba-Doudou National Park (Gabon), in order to investigate naturally occurring adenovirus in target gorillas and tested specifically a possible zoonotic transmission with local people inhabiting the vicinity of the park. Fecal samples were collected from western lowland gorillas and humans, and analyzed by PCR. We detected adenoviral genes in samples from both gorillas and the local people living around the national park, respectively: the overall prevalence rates of adenovirus were 24.1 and 35.0 % in gorillas and humans, respectively. Sequencing revealed that the adenoviruses detected in the gorillas were members of Human mastadenovirus B (HAdV-B), HAdV-C, or HAdV-E, and those in the humans belonged to HAdV-C or HAdV-D. Although HAdV-C members were detected in both gorillas and humans, phylogenetic analysis revealed that the virus detected in gorillas are genetically distinct from those detected in humans. The HAdV-C constitutes a single host lineage which is compatible with the host-pathogen divergence. However, HAdV-B and HAdV-E are constituted by multiple host lineages. Moreover, there is no evidence of zoonotic transmission thus far. Since the gorilla-to-human transmission of adenovirus has been shown before, the current monitoring should be continued in a broader scale for getting more insights in the natural history of naturally occurring adenoviruses and for the safe management of gorillas' populations.

Development of replication-deficient adenovirus malaria vaccines

INTRODUCTION

Malaria remains a major threat to endemic populations and travelers, including military personnel to these areas. A malaria vaccine is feasible, as radiation attenuated sporozoites induce nearly 100% efficacy. Areas covered: This review covers current malaria clinical trials using adenoviruses and pre-clinical research. Heterologous prime-boost regimens, including replication-deficient human adenovirus 5 (HuAd5) carrying malaria antigens, are efficacious. However, efficacy appears to be adversely affected by pre-existing anti-HuAd5 antibodies. Current strategies focus on replacing HuAd5 with rarer human adenoviruses or adenoviruses isolated from non-human primates (NHPs). The chimpanzee adenovirus ChAd63 is undergoing evaluation in clinical trials including infants in malaria-endemic areas. Key antigens have been identified and are being used alone, in combination, or with protein subunit vaccines. Gorilla adenoviruses carrying malaria antigens are also currently being evaluated in preclinical models. These replacement adenovirus vectors will be successfully used to develop vaccines against malaria, as well as other infectious diseases. Expert commentary: Simplified prime-boost single shot regimens, dry-coated live vector vaccines or silicon microneedle arrays could be developed for malaria or other vaccines. Replacement vectors with similar or superior immunogenicity have rapidly advanced, and several are now in extensive Phase 2 and beyond in malaria as well as other diseases, notably Ebola.

Simian adenoviruses as vaccine vectors

Replication incompetent human adenovirus serotype 5 (HAdV-C5) has been extensively used as a delivery vehicle for gene therapy proteins and infectious disease antigens. These vectors infect replicating and nonreplicating cells, have a broad tissue tropism, elicit high immune responses and are easily purified to high titers. However, the utility of HAdV-C5 vectors as potential vaccines is limited due to pre-existing immunity within the human population that significantly reduces the immunogenicity of HAdV-C5 vaccines. In recent years, adenovirus vaccine development has focused on simian-derived adenoviral vectors, which have the desirable vector characteristics of HAdV-C5 but with negligible seroprevalence in the human population. Here, we discuss recent advances in simian adenovirus vaccine vector development and evaluate current research specifically focusing on clinical trial data.

Viral vectors as vaccine carriers

This chapter reviews the performance of viral vectors based on adenoviruses or adeno-associated virus as vaccine carriers for infectious diseases. Replication-defective adenovirus vectors based on multiple human or non-human serotypes have consistently induced potent transgene product-specific B and T cell responses and are increasingly being explored in human clinical trials. The immunogenicity of most vectors based on adeno-associated virus vectors has been poor with the exception of a recently described hybrid vector from rhesus macaques that due to its ability to induce potent responses in mice warrant further investigation.

Adenovirus and herpesvirus diversity in free-ranging great apes in the Sangha region of the Republic Of Congo

Infectious diseases have caused die-offs in both free-ranging gorillas and chimpanzees. Understanding pathogen diversity and disease ecology is therefore critical for conserving these endangered animals. To determine viral diversity in free-ranging, non-habituated gorillas and chimpanzees in the Republic of Congo, genetic testing was performed on great-ape fecal samples collected near Odzala-Kokoua National Park. Samples were analyzed to determine ape species, identify individuals in the population, and to test for the presence of herpesviruses, adenoviruses, poxviruses, bocaviruses, flaviviruses, paramyxoviruses, coronaviruses, filoviruses, and simian immunodeficiency virus (SIV). We identified 19 DNA viruses representing two viral families, Herpesviridae and Adenoviridae, of which three herpesviruses had not been previously described. Co-detections of multiple herpesviruses and/or adenoviruses were present in both gorillas and chimpanzees. Cytomegalovirus (CMV) and lymphocryptovirus (LCV) were found primarily in the context of co-association with each other and adenoviruses. Using viral discovery curves for herpesviruses and adenoviruses, the total viral richness in the sample population of gorillas and chimpanzees was estimated to be a minimum of 23 viruses, corresponding to a detection rate of 83%. These findings represent the first description of DNA viral diversity in feces from free-ranging gorillas and chimpanzees in or near the Odzala-Kokoua National Park and form a basis for understanding the types of viruses circulating among great apes in this region.