Detection of antibodies against adenovirus protein IX, fiber, and hexon in human sera by immunoblot assay

The adenovirus DNA-binding protein DBP

Adenoviruses are a group of double-stranded DNA viruses that can mainly cause respiratory, gastrointestinal, and eye infections in humans. In addition, adenoviruses are employed as vector vaccines for combatting viral infections, including SARS-CoV-2, and serve as excellent gene therapy vectors. These viruses have the ability to modulate the host cell machinery to their advantage and trigger significant restructuring of the nuclei of infected cells through the activity of viral proteins. One of those, the adenovirus DNA-binding protein (DBP), is a multifunctional non-structural protein that is integral to the reorganization processes. DBP is encoded in the E2A transcriptional unit and is highly abundant in infected cells. Its activity is unequivocally linked to the formation, structure, and integrity of virus-induced replication compartments, molecular hubs for the regulation of viral processes, and control of the infected cell. DBP also plays key roles in viral DNA replication, transcription, viral gene expression, and even host range specificity. Notably, post-translational modifications of DBP, such as SUMOylation and extensive phosphorylation, regulate its biological functions. DBP was first investigated in the 1970s, pioneering research on viral DNA-binding proteins. In this literature review, we provide an overview of DBP and specifically summarize key findings related to its complex structure, diverse functions, and significant role in the context of viral replication. Finally, we address novel insights and perspectives for future research.

Review: Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). Vaccine development approaches consist of viral vector vaccines, DNA vaccine, RNA vaccine, live attenuated virus, and recombinant proteins, which elicit a specific immune response. The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines. This is due to the fact that nano-based vaccines are stable, able to target, form images, and offer an opportunity to enhance the immune responses. The diameters of ultrafine nanoparticles are in the range of 1-100 nm. The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features. To be successful, nanomaterials must be uptaken into the cell, especially into the target and able to modulate cellular functions at the subcellular levels. The advantages of nano-based vaccines are the ability to protect a cargo such as RNA, DNA, protein, or synthesis substance and have enhanced stability in a broad range of pH, ambient temperatures, and humidity for long-term storage. Moreover, nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells. In this review, we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens. The discussion about their safe, effective, and affordable vaccines to immunize against COVID-19 will be highlighted.

Non-human primate adenoviruses of the Human Adenovirus B species are potent and broadly-acting oncolytic vector candidates

The use of human adenoviruses (hAds) as oncolytic agents has demonstrated considerable potential. However, their efficacy in clinical studies is generally moderate and often varies between patients. This may, in part, be attributable to variable pre-existing neutralizing immunity in patients, which can impact the antitumor efficacy and lead to response heterogeneity. Our aim was to isolate new Ads for the development of oncolytic vectors with low prevalence of neutralizing immunity in the human population. To this end, we isolated a collection of new nonhuman primate (nhp) Ads from stool samples of four great ape species held captive. We elected 12 isolates comprising the broadest genetic variability for further characterization. For three new nhpAds, all classified as the human adenovirus B (HAdV-B) species, no neutralizing activity could be detected when exposed to a preparation of immunoglobulins isolated from a pool of >1,000 donors as a surrogate of population immunity. In addition, the nhpAds of the HAdV-B species showed enhanced oncolytic potency compared to nhpAds of the HAdV-C species as well as to human adenovirus type 5 (HAdV-C5) in vitro when tested in a panel of 29 human cancer cell lines. Next-generation sequencing of the viral genomes revealed higher sequence similarity between hAds and nhpAds of HAdV-B compared to HAdV-C, which might underlie the differences in oncolytic ability. As a proof-of-concept, the Rb-binding domain of the E1A protein of the gorilla-derived HAdV-B nhpAd-lumc007 was deleted, thereby creating a new oncolytic derivative, which demonstrated increased oncolytic potential compared to HAdV-C5. Collectively, our data demonstrate that nhpAds of the HAdV-B species can serve as an alternative for the development of potent oncolytic Ad vectors with limited pre-existing neutralizing immunity in humans.

Human Adenovirus Serotype 5 Is Sensitive to IgM-Independent Neutralization In Vitro and In Vivo

Human adenovirus 5 (HAdV-5) is used as a vector in gene therapy clinical trials, hence its interactions with the host immune system have been widely studied. Previous studies have demonstrated that HAdV-5 binds specifically to murine coagulation factor X (mFX), inhibiting IgM and complement-mediated neutralization. Here, we examined the physical binding of immune components to HAdV-5 by nanoparticle tracking analysis, neutralization assays, mass spectrometry analysis and in vivo experiments. We observed that purified mouse Immunoglobulin M (IgM) antibodies bound to HAdV-5 only in the presence of complement components. Active serum components were demonstrated to bind to HAdV-5 in the presence or absence of mFX, indicating that immune molecules and mFX might bind to different sites. Since binding of mFX to HAdV-5 blocks the neutralization cascade, these findings suggested that not all complement-binding sites may be involved in virion neutralization. Furthermore, the data obtained from serum neutralization experiments suggested that immune molecules other than IgM and IgG may trigger activation of the complement cascade in vitro. In vivo experiments were conducted in immunocompetent C57BL/6 or immuno-deficient Rag2^-/- mice. HAdV-5T* (a mutant HAdV-5 unable to bind to human or mFX) was neutralized to some extent in both mouse models, suggesting that murine immunoglobulins were not required for neutralization of HAdV-5 in vivo. Liquid Chromatography-Mass Spectrometry (LC-MS/MS) analysis of HAdV-5 and HAdV-5T* after exposure to murine sera showed stable binding of C3 and C4b in the absence of mFX. In summary, these results suggest that HAdV-5 neutralization can be mediated by both the classical and alternative pathways and that, in the absence of immunoglobulins, the complement cascade can be activated by direct binding of C3 to the virion.

Progress in Adenoviral Capsid-Display Vaccines

Adenoviral vectored vaccines against infectious diseases are currently in clinical trials due to their capacity to induce potent antigen-specific B- and T-cell immune responses. Heterologous prime-boost vaccination with adenoviral vector and, for example, adjuvanted protein-based vaccines can further enhance antigen-specific immune responses. Although leading to potent immune responses, these heterologous prime-boost regimens may be complex and impact manufacturing costs limiting efficient implementation. Typically, adenoviral vectors are engineered to genetically encode a transgene in the E1 region and utilize the host cell machinery to express the encoded antigen and thereby induce immune responses. Similarly, adenoviral vectors can be engineered to display foreign immunogenic peptides on the capsid-surface by insertion of antigens in capsid proteins hexon, fiber and protein IX. The ability to use adenoviral vectors as antigen-display particles, with or without using the genetic vaccine function, greatly increases the versatility of the adenoviral vector for vaccine development. This review describes the application of adenoviral capsid antigen-display vaccine vectors by focusing on their distinct advantages and possible limitations in vaccine development.

Overcoming resistance to anti-PD immunotherapy in a syngeneic mouse lung cancer model using locoregional virotherapy

Anti-PD-1 and anti-PD-L1 immunotherapy has provided a new therapeutic opportunity for treatment of advanced-stage non-small cell lung cancer (NSCLC). However, overall objective response rates are approximately 15%-25% in all NSCLC patients who receive anti-PD therapy. Therefore, strategies to overcome primary resistance to anti-PD immunotherapy are urgently needed. We hypothesized that the barrier to the success of anti-PD therapy in most NSCLC patients can be overcome by stimulating the lymphocyte infiltration at cancer sites through locoregional virotherapy. To this end, in this study, we determined combination effects of anti-PD immunotherapy and oncolytic adenoviral vector-mediated tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL) gene therapy (Ad/E1-TRAIL) or adenoviral-mediated TP53 (Ad/CMV-TP53) gene therapy in syngeneic mice bearing subcutaneous tumors derived from M109 lung cancer cells. Both anti-PD-1 and anti-PD-L1 antibodies failed to elicit obvious therapeutic effects in the M109 tumors. Intratumoral administration of Ad/E1-TRAIL or Ad/CMV-TP53 alone suppressed tumor growth in animals preexposed to an adenovector and bearing subcutaneous tumors derived from M109 cells. However, combining either anti-PD-1 or anti-PD-L1 antibody with these two adenoviral vectors elicited the strongest anticancer activity in mice with existing immunity to adenoviral vectors. Dramatically enhanced intratumoral immune response was detected in this group of combination therapy based on infiltrations of CD4+ and CD8+ lymphocytes and macrophages in tumors. Our results demonstrate that resistance to anti-PD-1 immunotherapy in syngeneic mouse lung cancer can be overcome by locoregional virotherapy.

Small-size recombinant adenoviral hexon protein fragments for the production of virus-type specific antibodies

Background

Adenoviruses are common pathogens infecting animals and humans. They are classified based on serology, or genome sequence information. These methods have limitations due to lengthy procedures or lack of infectivity data. Adenoviruses are easy to produce and amenable to genetic and biochemical modifications, which makes them a powerful tool for biological studies, and clinical gene-delivery and vaccine applications. Antibodies directed against adenoviral proteins are important diagnostic tools for virus identification in vivo and in vitro, and are used to elucidate infection mechanisms, often in combination with genomic sequencing and type specific information from hyper-variable regions of structural proteins.

Results

Here we describe a novel and readily useable method for cloning, expressing and purifying small fragments of hyper-variable regions 1-6 of the adenoviral hexon protein. We used these polypeptides as antigens for generating polyclonal rabbit antibodies against human adenovirus 3 (HAdV-B3), mouse adenovirus 1 (MAdV-1) and MAdV-2 hexon. In Western immunoblots with lysates from cells infected from thirteen human and three mouse viruses, these antibodies bound to homologous full-length hexon protein and revealed variable levels of cross-reactivity to heterologous hexons. Results from immuno-fluorescence and electron microscopy studies indicated that HAdV-B3 and MAdV-2 hexon antibodies recognized native forms of hexon.

Conclusions

The procedure described here can in principle be applied to any adenovirus for which genome sequence information is available. It provides a basis for generating novel type-specific tools in diagnostics and research, and extends beyond the commonly used anti-viral antibodies raised against purified viruses or subviral components.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0822-5) contains supplementary material, which is available to authorized users.

Efficient transduction of primary vascular cells by the rare adenovirus serotype 49 vector

Neointima formation and vascular remodeling through vascular smooth muscle cell migration and proliferation can limit the long-term success of coronary interventions, for example, in coronary artery bypass grafting (CABG). Ex vivo gene therapy has the potential to reduce unnecessary cell proliferation and limit neointima formation in vascular pathologies. To date, the species C adenovirus serotype 5 has been commonly used for preclinical gene therapy; however, its suitability is potentially limited by relatively poor tropism for vascular cells and high levels of preexisting immunity in the population. To avoid these limitations, novel species of adenovirus are being tested; here we investigate the potential of adenovirus 49 (Ad49) for use in gene therapy. Transduction of primary human vascular cells by a range of adenovirus serotypes was assessed; Ad49 demonstrated highest transduction of both vascular smooth muscle and endothelial cells. Gene transfer with Ad49 in vascular smooth muscle and endothelial cells was possible following short exposure times (<1 hr) and with low MOI, which is clinically relevant. Ex vivo delivery to surplus CABG tissue showed efficient gene transfer with Ad49, consistent with the in vitro findings. Luminal infusion of Ad49GFP into intact CABG samples ex vivo resulted in efficient vessel transduction. In addition, no seroprevalence rates to Ad49 were observed in a Scottish cohort of patients from cardiovascular clinics, thus circumventing issues with preexisting immunity. Our results show that Ad49 has tropism for vascular cells in vitro and ex vivo and demonstrate that Ad49 may be an improved vector for local vascular gene therapy compared with current alternatives.

The prevalence of IgG and IgA against adenoviruses in serum of children aged 11-26 months, hospitalised in the Clinical Paediatric Hospital in Warsaw, Poland

Adenoviruses are widely spread viruses causing infections related mainly to children. Contact with the pathogen may result in the presence of either immunoglobulin (Ig) A or IgG antibodies in the serum. The aim of this study was to assess the prevalence of IgA and IgG antibodies against adenoviruses in serum of children aged 11-27 months, hospitalised at the Public Children's Clinical Hospital in Warsaw. Immunoassay tests DRG Adenovirus IgA ELISA and IgG DRG Adenovirus ELISA detecting antibodies against all pathogenic serotypes of adenoviruses were performed in 128 sera samples. A low percentage of positive results for both immunoglobulins, 17 cases (13.28%) for IgA and 16 cases (12.50%) for IgG antibodies respectively were reported. We conclude, that the prevalence of antibodies against adenoviruses does not coincide with epidemiological data on the spread of infections among young children. The assays performed may be more useful in distinguishing the active form of the infection from seropositivity due to prior infection.

Identification of a nonstructural DNA-binding protein (DBP) as an antigen with diagnostic potential for human adenovirus

Background

Human adenoviruses (HAdVs) have been implicated as important agents in a wide range of human illnesses. To date, 58 distinct HAdV serotypes have been identified and can be grouped into six species. For the immunological diagnosis of adenoviruses, the hexon protein, a structural protein, has been used. The potential of other HAdV proteins has not been fully addressed.

Methodology/Principal Findings

In this study, a nonstructural antigenic protein, the DNA binding protein (DBP) of human adenovirus 5 and 35 (Ad5, Ad35) - was identified using immunoproteomic technology. The expression of Ad5 and Ad35 DBP in insect cells could be detected by rhesus monkey serum antibodies and healthy adult human serum positive for Ad5 and Ad35. Recombinant DBPs elicited high titer antibodies in mice. Their conserved domain displayed immunological cross-reactions with heterologous DBP antibodies in Western blot assays. DBP-IgM ELISA showed higher sensitivity adenovirus IgM detection than the commercial Adenovirus IgM Human ELISA Kit. A Western blot method developed based on Ad5 DBP was highly consistent with (χ² =  44.9, P<0.01) the Western blot assay for the hexon protein in the detection of IgG, but proved even more sensitive.

Conclusions/Significance

The HAdV nonstructural protein DBP is an antigenic protein that could serve as an alternative common antigen for adenovirus diagnosis.

T-cell response to viral antigens in adults and children with common variable immunodeficiency and specific antibody deficiency

Several T cell abnormalities have been described in common variable immunodeficiency (CVID), a B cell disorder of mainly unknown origin. A subset of CVID patients suffers from frequent reactivations of herpes viruses. We studied T cell function in CVID [and in a subset of paediatric patients with specific antibody deficiency (SAD)] by measuring T cell proliferation and cytokine production in response to herpes virus-antigens in paediatric CVID patients (n=9) and paediatric SAD patients (n=5), in adult CVID patients (n=14) and in healthy controls. Paediatric CVID patients, but not SAD patients, displayed moderately increased CD8+ T cell proliferation in response to cytomegalovirus, human herpes virus type 6B (HHV6-B) and herpes simplex virus compared to controls. CD8+ T cell responses in adult CVID patients tended to be increased in response to cytomegalovirus and herpes simplex virus. In response to stimulation with herpes virus antigens, the proinflammatory cytokines interleukin (IL)-1beta, IL-6, tumour necrosis factor (TNF)-alpha and interferon inducible protein (IP)-10 were produced. Overall, no major differences were detected in cytokine production upon stimulation between patients and controls, although higher IL-10 and IL-12 production was detected in paediatric patients. In conclusion, cellular immunity against herpes virus antigens appears undisturbed in CVID patients, although defects in subpopulations of CVID patients cannot be excluded.

Evaluation of cross-reactive cell-mediated immune responses among human, bovine and porcine adenoviruses

The absence of preexisting immunity against porcine adenovirus (Ad) serotype 3 (PAd3) and bovine Ad serotype 3 (BAd3) in humans makes them attractive alternatives to human Ad serotype 5 (HAd5) vectors. To determine whether there is significant cross-reactivity among HAd5, BAd3, and PAd3 at the level of cell-mediated immune responses, BALB/c mice were inoculated intraperitoneally with wild type (WT) or replication-defective (RD) HAd5, BAd3, or PAd3. Thirty-five days after the first inoculation, cross-reactive CD8+ cytotoxic T cells, as well as CD4+ Th1- and Th2-helper T cells, in the spleen were analyzed by ELISPOT, flow cytometry and cytotoxic T lymphocyte (CTL) assays. Virus neutralization assays were used to evaluate humoral cross-reactivity. CD8+ or CD4+ T cells primed with WT or RD HAd5, PAd3, or BAd3 demonstrated significant (P <0.005) reactivity with homologous Ad antigens, whereas, only minimal cross-reactivity was observed upon stimulation with heterologous Ad antigens. Ad-neutralizing antibodies were found to be homologous Ad-specific. Overall, these results suggest that there is no significant immunological cross-reactivity among HAd5, BAd3, and PAd3, thereby supporting the rationale for the use of BAd3 and PAd3 as alternative HAd vectors to circumvent anti-HAd immunity in humans.

Interactions between human plasma components and a xenogenic adenovirus vector: reduced immunogenicity during gene transfer

By the time we are adolescents most of us have been in contact with several of the >50 human adenovirus (HAd) serotypes. These common subclinical infections lead to an efficient anti-adenovirus cross-reacting adaptive immunity. During gene therapy, the ubiquitous anti-adenovirus humoral response and complement activation will modify and dictate vector biodistribution, as well as the response to the virion and transgene(s). In this study, we assayed the interactions of a xenogenic adenovirus derived from canine serotype 2 (CAV-2) with naturally occurring human antibodies (Abs) and the complement system. In our cohort, we found class G immunoglobulins (Igs) that recognized the intact CAV-2 virion and the external virion proteins. However, the majority of donors had low or no neutralizing Abs, class A, or class M Igs. Purified anti-HAd serotype 5 Abs also recognized CAV-2 virion proteins. In addition, in spite of the presence of anti-CAV-2 IgGs, CAV-2 poorly activated the classical and alternative complement cascades. This atypical response was due to a block upstream of the component 3 (C3) convertase and interplay between the component 1 (C1) inhibitor, the C1q-C1r2-C1s2 complex and CAV-2. Our data demonstrate that some xenogenic adenovirus vectors, like CAV-2, could lead to notably different outcomes following systemic delivery.

Seroprevalence of neutralizing antibodies to adenovirus type 5 among children in India: implications for recombinant adenovirus-based vaccines

We determined the levels of adenovirus 5 (Ad5) neutralizing antibodies in children in India less than 2 years of age. The results clearly show an age-dependent increase in Ad5-specific immunity, with 7- to 12-month-old children having the lowest levels of Ad5 immunity. This opens up the scope for the use of recombinant Ad5-based vaccines in this age group.