Seroprevalence of neutralizing antibodies to human adenoviruses type-5 and type-26 and chimpanzee adenovirus type-68 in healthy Chinese adults

An intranasal combination vaccine induces systemic and mucosal immunity against COVID-19 and influenza

Despite prolonged surveillance and interventions, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses continue to pose a severe global health burden. Thus, we developed a chimpanzee adenovirus-based combination vaccine, AdC68-HATRBD, with dual specificity against SARS-CoV-2 and influenza virus. When used as a standalone vaccine, intranasal immunization with AdC68-HATRBD induced comprehensive and potent immune responses consisting of immunoglobin (Ig) G, mucosal IgA, neutralizing antibodies, and memory T cells, which protected the mice from BA.5.2 and pandemic H1N1 infections. When used as a heterologous booster, AdC68-HATRBD markedly improved the protective immune response of the licensed SARS-CoV-2 or influenza vaccine. Therefore, whether administered intranasally as a standalone or booster vaccine, this combination vaccine is a valuable strategy to enhance the overall vaccine efficacy by inducing robust systemic and mucosal immune responses, thereby conferring dual lines of immunological defenses for these two viruses.

Chimeric oncolytic adenovirus evades neutralizing antibodies from human patients and exhibits enhanced anti-glioma efficacy in immunized mice

Oncolytic viruses are a promising treatment for patients with high-grade gliomas, but neutralizing antibodies can limit their efficacy in patients with prior virus exposure or upon repeated virus injections. Data from a previous clinical trial using the oncolytic adenovirus Delta-24-RGD showed that generation of anti-viral neutralizing antibodies may affect the long-term survival of glioma patients. Past studies have examined the effects of neutralizing antibodies during systemic virus injections, but largely overlooked their impact during local virus injections into the brain. We found that immunoglobulins colocalized with viral proteins upon local oncolytic virotherapy of brain tumors, warranting a strategy to prevent virus neutralization and maximize oncolysis. Thus, we generated a chimeric virus, Delta-24-RGD-H43m, by replacing the capsid protein HVRs from the serotype 5-based Delta-24-RGD with those from the rare serotype 43. Delta-24-RGD-H43m evaded neutralizing anti-Ad5 antibodies and conferred a higher rate of long-term survival than Delta-24-RGD in glioma-bearing mice. Importantly, Delta-24-RGD-H43m activity was significantly more resistant to neutralizing antibodies present in sera of glioma patients treated with Delta-24-RGD during a phase 1 clinical trial. These findings provide a framework for a novel treatment of glioma patients that have developed immunity against Delta-24-RGD.

Genomic Expedition: Deciphering Human Adenovirus Strains from the 2023 Outbreak in West Bengal, India: Insights into Viral Evolution and Molecular Epidemiology

Understanding the genetic dynamics of circulating Human Adenovirus (HAdV) types is pivotal for effectively managing outbreaks and devising targeted interventions. During the West Bengal outbreak of 2022-2023, an investigation into the genetic characteristics and outbreak potential of circulating HAdV types was conducted. Twenty-four randomly selected samples underwent whole-genome sequencing. Analysis revealed a prevalent recombinant strain, merging type 3 and type 7 of human mastadenovirus B1 (HAd-B1) species, indicating the emergence of recent strains of species B in India. Furthermore, distinctions in VA-RNAs and the E3 region suggested that current circulating strains of human mastadenovirus B1 (HAd-B1) possess the capacity to evade host immunity, endure longer within hosts, and cause severe respiratory infections. This study underscores the significance of evaluating the complete genome sequence of HAdV isolates to glean insights into their outbreak potential and the severity of associated illnesses.

Seroprevalence of human adenovirus type 5 neutralizing antibodies in the Philippines

Human adenovirus (HAdV), particularly the HAdV type 5 (HAdV-5), has been extensively utilized in the development of vector vaccines due to its high immunogenicity, good safety profile, and ease of propagation. However, one of the main challenges in its use is the presence of pre-existing immunity among vaccine recipients. Pre-existing neutralizing antibodies (NAbs) can prevent the uptake of HAdV-5 vectors and reduce vaccine efficacy. Hence, this study investigated the seroprevalence of NAbs against HAdV-5 in urban and rural regions of the Philippines. Luciferase-based neutralization assay was performed on 391 plasma/serum samples. Out of these samples, 346 or 88.5% were positive for HAdV-5 NAbs, and the majority of them (56.8%) had high titers against the virus. Among the regions included in this study, Bicol (Region V) had the highest seroprevalence rate (94.1%). Our findings show that a significant number of adults in the Philippines have pre-existing immunity against HAdV-5. This supports the recommendation that vaccination programs in the country should consider implementing vaccination techniques, such as a prime-boost regimen or addition of booster doses, to address the potential negative effects of pre-existing HAdV-5 immunity in the efficacy of adenoviral vector-based vaccines.

Characterization of Pre-Existing Neutralizing Antibody to Human Adenovirus Types 5 and 49 and Simian Type 23 in Chinese Population

Recombinant adenovirus vector has been widely used in vaccine development. Due to the pre-existing immunity of human adenovirus type 5 (HAd5) in humans, a range of rare human and chimpanzee adenovirus vectors have been developed. In the previous study, we constructed novel adenovirus vector Sad23L and Ad49L based on simian adenovirus type 23 (SAd23) and human adenovirus type 49 (HAd49), which were used in the development of ZIKV and COVID-19 vaccines. However, the levels of pre-existing neutralizing antibody (NAb) of HAd49 and SAd23 remain unclear in China. In this study, we measured NAbs titers of HAd5, HAd49, and SAd23 in 600 healthy blood donors from 6 regions across China. NAb titer of HAd49 or SAd23 was significantly lower than that of HAd5 (p < 0.001). There was no significant difference in seroprevalence and NAb titers of three adenoviruses between male and female donors. The seropositive rates of HAd5 and SAd23 increased with age growth in a positive correlation (p < 0.01), while in contrast to HAd5, HAd49, and SAd23 had a low level of pre-existing immunity in Chinese population, which suggested that Ad49L and Sad23L vectors could be used in vaccine development for humans.

Isolation of novel simian adenoviruses from macaques for development of a vector for human gene therapy and vaccines

IMPORTANCE

Adenoviruses are widely used in gene therapy and vaccine delivery. Due to the high prevalence of human adenoviruses (HAdVs), the pre-existing immunity against HAdVs in humans is common, which limits the wide and repetitive use of HAdV vectors. In contrast, the pre-existing immunity against simian adenoviruses (SAdVs) is low in humans. Therefore, we performed epidemiological investigations of SAdVs in simians and found that the SAdV prevalence was as high as 33.9%. The whole-genome sequencing and sequence analysis showed SAdV diversity and possible cross species transmission. One isolate with low level of pre-existing neutralizing antibodies in humans was used to construct replication-deficient SAdV vectors with E4orf6 substitution and E1/E3 deletion. Interestingly, we found that the E3 region plays a critical role in its replication in human cells, but the absence of this region could be compensated for by the E4orf6 from HAdV-5 and the E1 expression intrinsic to HEK293 cells.

Broad-spectrum vaccine via combined immunization routes triggers potent immunity to SARS-CoV-2 and its variants

IMPORTANCE

The development of broad-spectrum SARS-CoV-2 vaccines will reduce the global economic and public health stress from the COVID-19 pandemic. The use of conserved T-cell epitopes in combination with spike antigen that induce humoral and cellular immune responses simultaneously may be a promising strategy to further enhance the broad spectrum of COVID-19 vaccine candidates. Moreover, this research suggests that the combined vaccination strategies have the ability to induce both effective systemic and mucosal immunity, which may represent promising strategies for maximizing the protective efficacy of respiratory virus vaccines.

Evolution of nanomedicine formulations for targeted delivery and controlled release

Nanotechnology research over the past several decades has been aimed primarily at improving the physicochemical properties of small molecules to produce druggable candidates as well as for tumor targeting of cytotoxic molecules. The recent focus on genomic medicine and the success of lipid nanoparticles for mRNA vaccines have provided additional impetus for the development of nanoparticle drug carriers for nucleic acid delivery, including siRNA, mRNA, DNA, and oligonucleotides, to create therapeutics that can modulate protein deregulation. Bioassays and characterizations, including trafficking assays, stability, and endosomal escape, are key to understanding the properties of these novel nanomedicine formats. We review historical nanomedicine platforms, characterization methodologies, challenges to their clinical translation, and key quality attributes for commercial translation with a view to their developability into a genomic medicine. New nanoparticle systems for immune targeting, as well as in vivo gene editing and in situ CAR therapy, are also highlighted as emerging areas.

Clinical and laboratory features in health care volunteers with inactivated SARS-CoV-2 vaccination

Background/aim

To better optimize the inactivated vaccine-induced immune response and improve vaccine protection efficiency, a preliminary study was conducted on the influencing factors of producing neutralizing antibody (NAb) titers against the inactivated coronavirus disease 2019 (COVID-19) vaccine.

Materials and methods

A total of 91 health care volunteers were enrolled from the Immunology Division of the Laboratory Department of Chongqing General Hospital from February to March 2021. The study had a cross-sectional design. All of the volunteers were scheduled to receive a complete dose regimen of the inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine and the vaccination interval between 2 doses was 14 days. Clinical and laboratory features were collected for further analysis.

Results

The NAb titers gradually increased after COVID-19 vaccination, and 72.53% (n = 66) of the volunteers had NAbs after the second dose. Eight variables, including CD16+CD56+ NK cell level before the first dose (HR = 0.94, p = 0.02), CD16+CD56+ NK cell level after the second dose (HR = 0.94, p = 0.03), interleukin (IL)-2 level before the first dose (HR = 2.09, p = 0.05), mean corpuscular volume (HR = 0.86, p = 0.02), serum urea level (HR = 0.69, p = 0.05), increment of CD19+ B cells (HR = 0.86, p = 0.03), increment of CD4+/CD8+ T cells (HR = 0.21, p = 0.03), and increment of the IL-6 level (HR = 0.75, p = 0.04) demonstrated a correlation with the NAb titers after COVID-19 vaccination. In the multivariate logistical regression analysis, the serum urea level (HR = 2.32, P = 0.03) and increment of CD19+ B cells (HR = 1.96, p = 0.03) were positively correlated with the NAb titers. The principal component analysis effectively distinguished the response after COVID-19 vaccination. The Pearson correlation analysis indicated that the CD19+ B cell level (r = 0.23, p < 0.001) and IL-2 (r = 0.24, p < 0.001) and IL-6 levels (r = 0.22, p < 0.001) were weakly positively correlated with the concentration of NAbs.

Conclusion

The NAbs titers of the inactivated vaccines were positively correlated with the ratio of CD19+ B cell, IL-6, and IL-2 levels in the serum, which provide clinical guidance for inactivated SARS-CoV-2 vaccines.

Preclinical development of a vaccine-based immunotherapy regimen (VBIR) that induces potent and durable T cell responses to tumor-associated self-antigens

The development of therapeutic cancer vaccines remains an active area, although previous approaches have yielded disappointing results. We have built on lessons from previous cancer vaccine approaches and immune checkpoint inhibitor research to develop VBIR, a vaccine-based immunotherapy regimen. Assessment of various technologies led to selection of a heterologous vaccine using chimpanzee adenovirus (AdC68) for priming followed by boosts with electroporation of DNA plasmid to deliver T cell antigens to the immune system. We found that priming with AdC68 rapidly activates and expands antigen-specific T cells and does not encounter pre-existing immunity as occurs with the use of a human adenovirus vaccine. The AdC68 vector does, however, induce new anti-virus immune responses, limiting its use for boosting. To circumvent this, boosting with DNA encoding the same antigens can be done repetitively to augment and maintain vaccine responses. Using mouse and monkey models, we found that the activation of both CD4 and CD8 T cells was amplified by combination with anti-CTLA-4 and anti-PD-1 antibodies. These antibodies were administered subcutaneously to target their distribution to vaccination sites and to reduce systemic exposure which may improve their safety. VBIR can break tolerance and activate T cells recognizing tumor-associated self-antigens. This activation lasts more than a year after completing treatment in monkeys, and inhibits tumor growth to a greater degree than is observed using the individual components in mouse cancer models. These results have encouraged the testing of this combination regimen in cancer patients with the aim of increasing responses beyond current therapies.

An Old Acquaintance: Could Adenoviruses Be Our Next Pandemic Threat?

Human adenoviruses (HAdV) are one of the most important pathogens detected in acute respiratory diseases in pediatrics and immunocompromised patients. In 1953, Wallace Rowe described it for the first time in oropharyngeal lymphatic tissue. To date, more than 110 types of HAdV have been described, with different cellular tropisms. They can cause respiratory and gastrointestinal symptoms, even urinary tract inflammation, although most infections are asymptomatic. However, there is a population at risk that can develop serious and even lethal conditions. These viruses have a double-stranded DNA genome, 25-48 kbp, 90 nm in diameter, without a mantle, are stable in the environment, and resistant to fat-soluble detergents. Currently the diagnosis is made with lateral flow immunochromatography or molecular biology through a polymerase chain reaction. This review aimed to highlight the HAdV variability and the pandemic potential that a HAdV3 and 7 recombinant could have considering the aggressive outbreaks produced in health facilities. Herein, we described the characteristics of HAdV, from the infection to treatment, vaccine development, and the evaluation of the social determinants of health associated with HAdV, suggesting the necessary measures for future sanitary control to prevent disasters such as the SARS-CoV-2 pandemic, with an emphasis on the use of recombinant AdV vaccines to control other potential pandemics.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Combining intramuscular and intranasal homologous prime-boost with a chimpanzee adenovirus-based COVID-19 vaccine elicits potent humoral and cellular immune responses in mice

The efficacy of many coronavirus disease 2019 (COVID-19) vaccines has been shown to decrease to varying extents against new severe acute respiratory syndrome coronavirus 2 variants, which are responsible for the continuing COVID-19 pandemic. Combining intramuscular and intranasal vaccination routes is a promising approach for achieving more potent immune responses. We evaluated the immunogenicity of prime-boost protocols with a chimpanzee adenovirus serotype 68 vector-based vaccine, ChAdTS-S, administered via both intranasal and intramuscular routes in BALB/c mice. Intramuscular priming followed by an intranasal booster elicited the highest levels of IgG, IgA, and pseudovirus neutralizing antibody titres among all the protocols tested at day 42 after prime immunization compared with the intranasal priming/intramuscular booster and prime-boost protocols using only one route. In addition, intramuscular priming followed by an intranasal booster induced high T-cell responses, measured using the IFN-γ ELISpot assay, that were similar to those observed upon intramuscular vaccination. All ChAdTS-S vaccination groups induced Th1-skewing of the T-cell response according to intracellular cytokine staining and Meso Scale Discovery cytokine profiling assays on day 56 after priming. This study provides reference data for assessing vaccination schemes of adenovirus-based COVID-19 vaccines with high immune efficacy.

Seroprevalence of neutralizing antibodies against adenovirus type 26 and 35 in healthy populations from Guangdong and Shandong provinces, China

Human adenoviruses type 26 (HAdV26) and type 35 (HAdV35) have increasingly become the choice of adenovirus vectors for vaccine application. However, the population pre-existing immunity to these two adenoviruses in China, which may reduce vaccine efficacy, remains largely unknown. Here, we established micro-neutralizing (MN) assays to investigate the seroprevalence of neutralizing antibodies (nAbs) against HAdV26 and HAdV35 in the general population of Guangdong and Shandong provinces, China. A total of 1184 serum samples were collected, 47.0% and 15.8% of which showed HAdV26 and HAdV35 nAb activity, respectively. HAdV26-seropositive individuals tended to have more moderate nAbs titers (201–1000), while HAdV35-seropositive individuals appeared to have more low nAbs titers (72–200). The seropositive rates of HAdV26 and HAdV35 in individuals younger than 20 years old were very low. The seropositive rates of HAdV26 increased with age before 70 years old and decreased thereafter, while HAdV35 seropositive rates did not show similar characteristics. Notably, the seropositive rates and nAb levels of both HAdV26 and HAdV35 were higher in Guangdong Province than in Shandong Province, but did not exert significant differences between males and females. The seroprevalence between HAdV26 and HAdV35 showed little correlation, and no significant cross-neutralizing activity was detected. These results clarified the characteristics of the herd immunity against HAdV26 and HAdV35, and provided information for the rational development and application of HAdV26 and HAdV35 as vaccine vectors in China.

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We address the pre-existing immunity of HAdV26 and HAdV35.

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The overall seroprevalence of nAbs against HAdV26 and HAdV35 were 47.0% and 15.8%.

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The seroprevalence level of HAdV26 and HAdV35 differed in age and in district.

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Pre-existing immunity should be considered when adenoviral vectors are used.

Role of Adenoviruses in Cancer Therapy

Cancer is one of the leading causes of death in the world, which is the second after heart diseases. Adenoviruses (Ads) have become the promise of new therapeutic strategy for cancer treatment. The objective of this review is to discuss current advances in the applications of adenoviral vectors in cancer therapy. Adenoviral vectors can be engineered in different ways so as to change the tumor microenvironment from cold tumor to hot tumor, including; 1. by modifying Ads to deliver transgenes that codes for tumor suppressor gene (p53) and other proteins whose expression result in cell cycle arrest 2. Ads can also be modified to express tumor specific antigens, cytokines, and other immune-modulatory molecules. The other strategy to use Ads in cancer therapy is to use oncolytic adenoviruses, which directly kills tumor cells. Gendicine and Advexin are replication-defective recombinant human p53 adenoviral vectors that have been shown to be effective against several types of cancer. Gendicine was approved for treatment of squamous cell carcinoma of the head and neck by the Chinese Food and Drug Administration (FDA) agency in 2003 as a first-ever gene therapy product. Oncorine and ONYX-015 are oncolytic adenoviral vectors that have been shown to be effective against some types of cancer. The Chiness FDA agency has also approved Oncorin for the treatment of head and neck cancer. Ads that were engineered to express immune-stimulatory cytokines and other immune-modulatory molecules such as TNF-α, IL-2, BiTE, CD40L, 4-1BBL, GM-CSF, and IFN have shown promising outcome in treatment of cancer. Ads can also improve therapeutic efficacy of immune checkpoint inhibitors and adoptive cell therapy (Chimeric Antigen Receptor T Cells). In addition, different replication-deficient adenoviral vectors (Ad5-CEA, Ad5-PSA, Ad-E6E7, ChAdOx1-MVA and Ad-transduced Dendritic cells) that were tested as anticancer vaccines have been demonstrated to induce strong antitumor immune response. However, the use of adenoviral vectors in gene therapy is limited by several factors such as pre-existing immunity to adenoviral vectors and high immunogenicity of the viruses. Thus, innovative strategies must be continually developed so as to overcome the obstacles of using adenoviral vectors in gene therapy.

Human adenovirus type 26 basic biology and its usage as vaccine vector

Due to their nature, adenoviruses have been recognised as promising candidates for vaccine vector development. Since they mimic natural infection, recombinant adenovirus vectors have been proven as ideal shuttles to deliver foreign transgenes aiming at inducing both humoral and cellular immune response. In addition, a potent adjuvant effect can be exerted due to the adenovirus inherent stimulation of various elements of innate and adaptive immunity. Due to its low seroprevalence in humans as well as induction of favourable immune response to inserted transgene, human adenovirus type 26 (HAdV-D26) has been recognised as a promising platform for vaccine vector development and is studied in number of completed or ongoing clinical studies. Very recently HAdV-D26 based Ebola and Covid-19 vaccines were approved for medical use. In this review, current state of the art regarding HAdV-D26 basic biology and its usage as vaccine vector will be discussed.

Humoral and Cellular Responses to COVID-19 Vaccines in SARS-CoV-2 Infection-Naïve and -Recovered Korean Individuals

In the face of a global COVID-19 vaccine shortage, an efficient vaccination strategy is required. Therefore, the immunogenicity of single or double COVID-19 vaccination doses (ChAdOX1, BNT162b2, or mRNA-1273) of SARS-CoV-2-recovered individuals was compared to that of unvaccinated individuals with SARS-CoV-2 infection at least one year post-convalescence. Moreover, the immunogenicity of SARS-CoV-2-naïve individuals vaccinated with a complete schedule of Ad26.CoV2.S, ChAdOX1, BNT162b2, mRNA-1273, or ChAdOX1/BNT162b2 vaccines was evaluated. Anti-SARS-CoV-2 S1 IgG antibody (S1-IgG), pseudotyped virus-neutralizing antibody titer (pVNT₅₀), and IFN-γ ELISpot counts were measured. Humoral immune responses were significantly higher in vaccinated than in unvaccinated recovered individuals, with a 43-fold increase in the mean pVNT₅₀ values. However, there was no significant difference in the pVNT₅₀ and IFN-γ ELISpot values between the single- and double-dose regimens. In SARS-CoV-2-naïve individuals, antibody responses varied according to the vaccine type: BNT162b2 and mRNA-1273 induced similar levels of S1-IgG to those observed in vaccinated, convalescent individuals; in contrast, pVNT₅₀ was much lower in SARS-CoV-2-naïve vaccinees than in vaccinated recovered individuals. Therefore, a single dose of ChAdOX1, BNT162b2, or mRNA-1273 vaccines would be a good alternative for recovered individuals instead of a double-dose regimen.

Immune responses following the first dose of the Sputnik V (Gam-COVID-Vac)

As the first dose of Gam-COVID-Vac, is currently used as a single dose vaccine in some countries, we investigated the immunogenicity of this at 4 weeks (327 naïve individuals). 88.7% seroconverted, with significantly lower seroconversion rates in those over 60 years (p = 0.004) and significantly lower than previously seen with AZD1222 (p = 0.018). 82.6% developed ACE2 receptor blocking antibodies, although levels were significantly lower than following natural infection (p = 0.0009) and a single dose of AZD1222 (p < 0.0001). Similar titres of antibodies were observed to the receptor binding domain of WT, B.1.1.7 and B.1.617.2 compared to AZD1222, while the levels for B.1.351 were significantly higher (p = 0.006) for Gam-COVID-Vac. 30% developed ex vivo IFNγ ELISpot responses (significantly lower than AZD1222), and high frequency of CD107a expressing T cells along with memory B cell responses. Although single dose of Gam-COVID-Vac was highly immunogenic, administration of a second dose is likely to be beneficial.

Oncolytic Viruses and Cancer, Do You Know the Main Mechanism?

The global rate of cancer has increased in recent years, and cancer is still a threat to human health. Recent developments in cancer treatment have yielded the understanding that viruses have a high potential in cancer treatment. Using oncolytic viruses (OVs) is a promising approach in the treatment of malignant tumors. OVs can achieve their targeted treatment effects through selective cell death and induction of specific antitumor immunity. Targeting tumors and the mechanism for killing cancer cells are among the critical roles of OVs. Therefore, evaluating OVs and understanding their precise mechanisms of action can be beneficial in cancer therapy. This review study aimed to evaluate OVs and the mechanisms of their effects on cancer cells.

Immunological Study of Reconstructed Common Ancestral Sequence of Adenovirus Hexon Protein

Aim: To reconstruct the ancestral sequence of human adenoviral hexon protein by combining sequence variations and structural information. And to provide a candidate hexon protein for developing new adenoviral vector capable of escaping the pre-existing immunity in healthy populations.

Methods: The sequences of 74 adenovirus-type strains were used to predict the ancestral sequence of human adenovirus hexon protein using FastML and MEGA software. The three-dimensional structure model was built using homology modeling methods. The immunological features of ancestral loop 1 and loop 2 regions of sequences were tested using protein segments expressed in a prokaryotic expression system and polypeptides synthesized with human serum samples.

Results: The tower region of the hexon protein had the highest sequence variability, while the neck and base regions remained constant among different types. The modern strains successfully predicted the common ancestral sequence of the human adenovirus hexon. The positive sera against neutralizing epitopes on the common ancestor of adenoviral hexon were relatively rare among healthy adults.

Conclusion: The existing strains inferred the common ancestor of human adenoviruses, with epitopes never observed in the current human strains. The predicted common ancestor hexon is a good prospect in the improvement of adenovirus vectors.

Sixteen capillary electrophoresis applications for viral vaccine analysis

A broad range of CE applications from our organization is reviewed to give a flavor of the use of CE within the field of vaccine analyses. Applicability of CE for viral vaccine characterization, and release and stability testing of seasonal influenza virosomal vaccines, universal subunit influenza vaccines, Sabin inactivated polio vaccines (sIPV), and adenovirus vector vaccines were demonstrated. Diverse CZE, CE-SDS, CGE, and cIEF methods were developed, validated, and applied for virus, protein, posttranslational modifications, DNA, and excipient concentration determinations, as well as for the integrity and composition verifications, and identity testing (e.g., CZE for intact virus particles, CE-SDS application for hemagglutinin quantification and influenza strain identification, chloride or bromide determination in process samples). Results were supported by other methods such as RP-HPLC, dynamic light scattering (DLS), and zeta potential measurements. Overall, 16 CE methods are presented that were developed and applied, comprising six adenovirus methods, five viral protein methods, and methods for antibodies determination of glycans, host cell-DNA, excipient chloride, and process impurity bromide. These methods were applied to support in-process control, release, stability, process- and product characterization and development, and critical reagent testing. Thirteen methods were validated. Intact virus particles were analyzed at concentrations as low as 0.8 pmol/L. Overall, CE took viral vaccine testing beyond what was previously possible, improved process and product understanding, and, in total, safety, efficacy, and quality.

GRAd-COV2, a gorilla adenovirus-based candidate vaccine against COVID-19, is safe and immunogenic in younger and older adults

[Figure: see text].

From the environment to the cells: An overview on pivotal factors which affect spreading and infection in COVID-19 pandemic

Several factors ranging from environmental risks to the genetics of the virus and that of the hosts, affect the spread of COVID-19. The impact of physicochemical variables on virus vitality and spread should be taken into account in experimental and clinical studies. Another avenue to explore is the effect of diet and its interaction with the immune system on SARS-CoV-2 infection and mortality rate. Past year have witnessed extensive studies on virus and pathophysiology of the COVID-19 disease and the cellular mechanisms of virus spreading. However, our knowledge has not reached a level where we plan an efficient therapeutic approach to prevent the virus entry to the cells or decreasing the spreading and morbidity in severe cases of disease. The risk of infection directly correlates with the control of virus spreading via droplets and aerosol transmission, as well as patient immune system response. A key goal in virus restriction and transmission rate is to understand the physicochemical structure of aerosol and droplet formation, and the parameters that affect the droplet-borne and airborne in different environmental conditions. The lifetime of droplets on different surfaces is described based on the contact angle. Hereby, we recommend regular use of high-quality face masks in high temperature and low humidity conditions. However, in humid and cold weather conditions, wearing gloves and frequently hand washing, gain a higher priority. Additionally, social distancing rules should be respected in all aforementioned conditions. We will also discuss different routes of SARS-CoV-2 entry into the cells and how multiple genetic factors play a role in the spread of the virus. Given the role of environmental and nutritional factors, we discuss and recommend some strategies to prevent the disease and protect the population against COVID-19. Since an effective vaccine can prevent the transmission of communicable diseases and abolish pandemics, we added a brief review of candidate SARS-CoV-2 vaccines.

Racing to immunity: Journey to a COVID-19 vaccine and lessons for the future

SARS-CoV-2 is the novel coronavirus behind the COVID-19 pandemic. Since its emergence, the global scientific community has mobilized to study this virus, and an overwhelming effort to identify COVID-19 treatments is currently ongoing for a variety of therapeutics and prophylactics. To better understand these efforts, we compiled a list of all COVID-19 vaccines undergoing preclinical and clinical testing using the WHO and ClinicalTrials.gov database, with details surrounding trial design and location. The most advanced vaccines are discussed in more detail, with a focus on their technology, advantages and disadvantages, as well as any available recent clinical findings. We also cover some of the primary challenges, safety concerns and public responses to COVID-19 vaccine trials, and consider what this can mean for the future. By compiling this information, we aim to facilitate a more thorough understanding of the extensive COVID-19 clinical testing vaccine landscape as it unfolds, and better highlight some of the complexities and challenges being faced by the joint effort of the scientific community in finding a prophylactic against COVID-19.

Single-Dose Immunization With a Chimpanzee Adenovirus-Based Vaccine Induces Sustained and Protective Immunity Against SARS-CoV-2 Infection

The development of a safe and effective vaccine against SARS-CoV-2, the causative agent of pandemic coronavirus disease-2019 (COVID-19), is a global priority. Here, we aim to develop novel SARS-CoV-2 vaccines based on a derivative of less commonly used rare adenovirus serotype AdC68 vector. Three vaccine candidates were constructed expressing either the full-length spike (AdC68-19S) or receptor-binding domain (RBD) with two different signal sequences (AdC68-19RBD and AdC68-19RBDs). Single-dose intramuscular immunization induced robust and sustained binding and neutralizing antibody responses in BALB/c mice up to 40 weeks after immunization, with AdC68-19S being superior to AdC68-19RBD and AdC68-19RBDs. Importantly, immunization with AdC68-19S induced protective immunity against high-dose challenge with live SARS-CoV-2 in a golden Syrian hamster model of SARS-CoV-2 infection. Vaccinated animals demonstrated dramatic decreases in viral RNA copies and infectious virus in the lungs, as well as reduced lung pathology compared to the control animals. Similar protective effects were also found in rhesus macaques. Taken together, these results confirm that AdC68-19S can induce protective immune responses in experimental animals, meriting further development toward a human vaccine against SARS-CoV-2.

Understanding Post Entry Sorting of Adenovirus Capsids; A Chance to Change Vaccine Vector Properties

Adenovirus vector-based genetic vaccines have emerged as a powerful strategy against the SARS-CoV-2 health crisis. This success is not unexpected because adenoviruses combine many desirable features of a genetic vaccine. They are highly immunogenic and have a low and well characterized pathogenic profile paired with technological approachability. Ongoing efforts to improve adenovirus-vaccine vectors include the use of rare serotypes and non-human adenoviruses. In this review, we focus on the viral capsid and how the choice of genotypes influences the uptake and subsequent subcellular sorting. We describe how understanding capsid properties, such as stability during the entry process, can change the fate of the entering particles and how this translates into differences in immunity outcomes. We discuss in detail how mutating the membrane lytic capsid protein VI affects species C viruses' post-entry sorting and briefly discuss if such approaches could have a wider implication in vaccine and/or vector development.

COVID-19 immunity and vaccines: what a pharmacist needs to know

COVID-19 vaccines are being produced using different platforms by different companies, some of which are entering Phase 3 and 4 trials. Due to the pandemic, this production has been accelerated, which leaves a window for speculation on the method of production and safety. Pharmacists are familiar with vaccination; however, COVID-19 vaccines are still new and further work is needed to clarify many aspects, including side effects, methods of storage, and number of doses. Prioritization of vaccination has been implemented to a certain extent, but no clear strategy is available. A comprehensive overview on immunity and immunological principles for the design of COVID-19 vaccine strategies is provided in this narrative review and the current COVID-19 vaccine landscape is discussed, in addition to exploring the principles for prioritization of vaccination using data from articles available in PubMed and from health organizations. Pharmacists should have a better understanding of COVID-19 vaccines and their manufacture. This would also allow better counseling of the public on COVID 19, immunization, and explaining prioritization basis and vaccination programs.

The conundrum of current anti-SARS-CoV-2 vaccines

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has given rise to the urgent need for vaccines and therapeutic interventions to address the spread of the SARS-CoV-2 virus. SARS-CoV-2 vaccines in development, and those being distributed currently, have been designed to induce neutralizing antibodies using the spike protein of the virus as an immunogen. However, the immunological correlates of protection against the virus remain unknown. This raises questions about the efficacy of current vaccination strategies. In addition, safety profiles of several vaccines seem inadequate or have not yet been evaluated under controlled experimentation. Here, evidence from the literature regarding the efforts already made to identify the immunological correlates of protection against SARS-CoV-2 infection are summarized. Furthermore, key biological features of most of the advanced vaccines and considerations regarding their safety and expected efficacy are highlighted.

An overview of vaccine development for COVID-19

The COVID-19 pandemic continues to endanger world health and the economy. The causative SARS-CoV-2 coronavirus has a unique replication system. The end point of the COVID-19 pandemic is either herd immunity or widespread availability of an effective vaccine. Multiple candidate vaccines - peptide, virus-like particle, viral vectors (replicating and nonreplicating), nucleic acids (DNA or RNA), live attenuated virus, recombinant designed proteins and inactivated virus - are presently under various stages of expansion, and a small number of vaccine candidates have progressed into clinical phases. At the time of writing, three major pharmaceutical companies, namely Pfizer and Moderna, have their vaccines under mass production and administered to the public. This review aims to investigate the most critical vaccines developed for COVID-19 to date.

Frontrunners in the race to develop a SARS-CoV-2 vaccine

Numerous studies continue to be published on the COVID-19 pandemic that is being caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Given the rapidly evolving global response to SARS-CoV-2, here we primarily review the leading COVID-19 vaccine strategies that are currently in Phase III clinical trials. Nonreplicating viral vector strategies, inactivated virus, recombinant protein subunit vaccines, and nucleic acid vaccine platforms are all being pursued in an effort to combat the infection. Preclinical and clinal trial results of these efforts are examined as well as the characteristics of each vaccine strategy from the humoral and cellular immune responses they stimulate, effects of any adjuvants used, and the potential risks associated with immunization such as antibody-dependent enhancement. A number of promising advancements have been made toward the development of multiple vaccine candidates. Preliminary data now emerging from phase III clinical trials show encouraging results for the protective efficacy and safety of at least 3 frontrunning candidates. There is hope that one or more will emerge as potent weapons to protect against SARS-CoV-2.

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.

Immunological considerations for COVID-19 vaccine strategies

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most formidable challenge to humanity in a century. It is widely believed that prepandemic normalcy will never return until a safe and effective vaccine strategy becomes available and a global vaccination programme is implemented successfully. Here, we discuss the immunological principles that need to be taken into consideration in the development of COVID-19 vaccine strategies. On the basis of these principles, we examine the current COVID-19 vaccine candidates, their strengths and potential shortfalls, and make inferences about their chances of success. Finally, we discuss the scientific and practical challenges that will be faced in the process of developing a successful vaccine and the ways in which COVID-19 vaccine strategies may evolve over the next few years.

The Oncolytic Virus in Cancer Diagnosis and Treatment

Cancer has always been an enormous threat to human health and survival. Surgery, radiotherapy, and chemotherapy could improve the survival of cancer patients, but most patients with advanced cancer usually have a poor survival or could not afford the high cost of chemotherapy. The emergence of oncolytic viruses provided a new strategy for us to alleviate or even cure malignant tumors. An oncolytic virus can be described as a genetically engineered or naturally existing virus that can selectively replicate in cancer cells and then kill them without damaging the healthy cells. There have been many kinds of oncolytic viruses, such as herpes simplex virus, adenovirus, and Coxsackievirus. Moreover, they have different clinical applications in cancer treatment. This review focused on the clinical application of oncolytic virus and predicted the prospect by analyzing the advantages and disadvantages of oncolytic virotherapy.

Adenovirus delivery of encoded monoclonal antibody protects against different types of influenza virus infection

Due to the high mutation and recombination rates of the influenza virus, current clinically licensed influenza vaccines and anti-influenza drugs provide limited protection against the emerging influenza virus epidemic. Therefore, universal influenza vaccines with high efficacy are urgently needed to ensure human safety and health. Passive immunization of influenza broadly neutralizing antibodies may become an ideal option for controlling influenza infection. CR9114 isolated from the peripheral blood mononuclear cells of healthy donors is a broadly neutralizing monoclonal antibody that targets different types of influenza viruses. As the adenovirus vector is one of the most promising delivery vehicles, we employed the chimpanzee adenoviral vector, AdC68, to express CR9114 as a universal anti-influenza vaccine, termed AdC68-CR9114, and evaluated its antibody expression and its broad spectrum of prophylactic and therapeutic effects in animal models. Based on our findings, AdC68-CR9114-infected cell expressed the broadly neutralizing antibody at a high level in vitro and in vivo, exhibited biological functions, and protected mice from different types of influenza virus infection at different time points. The findings from this study shed light on a new strategy for controlling and preventing influenza infection.

High-Capacity Adenoviral Vectors: Expanding the Scope of Gene Therapy

The adaptation of adenoviruses as gene delivery tools has resulted in the development of high-capacity adenoviral vectors (HC-AdVs), also known, helper-dependent or "gutless". Compared with earlier generations (E1/E3-deleted vectors), HC-AdVs retain relevant features such as genetic stability, remarkable efficacy of in vivo transduction, and production at high titers. More importantly, the lack of viral coding sequences in the genomes of HC-AdVs extends the cloning capacity up to 37 Kb, and allows long-term episomal persistence of transgenes in non-dividing cells. These properties open a wide repertoire of therapeutic opportunities in the fields of gene supplementation and gene correction, which have been explored at the preclinical level over the past two decades. During this time, production methods have been optimized to obtain the yield, purity, and reliability required for clinical implementation. Better understanding of inflammatory responses and the implementation of methods to control them have increased the safety of these vectors. We will review the most significant achievements that are turning an interesting research tool into a sound vector platform, which could contribute to overcome current limitations in the gene therapy field.

Seroprevalence of Human Adenovirus Type 5 Neutralizing Antibody in Common Marmosets Determined by a New Set of Two Assays

Preexisting neutralizing antibody (NAb) against human adenovirus serotype 5 (AdHu5) can reduce the immunogenicity of AdHu5 vector-based vaccine, thus inhibiting the host's immune response and utility of other homologous vectors. Common marmoset (Callithrix jacchus), a small new world primate, has attracted considerable attention for its potential as a preclinical research model of vaccine development. However, the prevalence of anti-AdHu5 NAb activity in common marmosets bred in China remains unknown. A recombinant adenovirus expressing luciferase and Zs Green reporter genes were constructed to detect NAb against rAdHu5 by flow cytometry (FCM) and chemiluminescence (CL) assay. Five of 25 marmosets (20%) presented AdHu5 NAb detectable by FCM. Four animals had low titer (1/16), while the fifth one reached 1/64. While by CL assay, 7 of 25 (28%) marmosets were anti-AdHu5 NAb positive. Four animals, two of whom were negative by FCM, also had low titer NAb (1/16), suggesting assay discrepancy at low levels. Two marmosets, 1/32 titer by CL, were at 1/16 by FCM. A single animal showed a high titer with both assays (1/128 and 1/64 by CL and FCM, respectively). The CL method was simpler, more sensitive, accurate, and stable. The low prevalence of preexisting anti-AdHu5 NAb in marmosets provides important background information on the feasibility and applicability of using marmosets as a preclinical research model for vaccine development.

A chimpanzee adenoviral vector-based rabies vaccine protects beagle dogs from lethal rabies virus challenge

Rabies continues to poses serious threats to the public health in many countries. The development of novel inexpensive, safe and effective vaccines has become a high priority for rabies control worldwide. We previously generated a novel recombinant rabies vaccine by cloning rabies virus glycoprotein into a chimpanzee adenoviral vector, termed ChAd68-Gp. The present study evaluated the immune responses and protection afforded by this vaccine in beagle dogs. The results demonstrated that intramuscular immunization with both low-dose and high-dose of ChAd68-Gp induced strong immune responses and provided complete protection in beagles even at low-dose. However, when administered orally, high-dose vaccination was protective while low-dose vaccination was ineffective. Further investigation indicated that the low-pH value of gastric juice in the stomach of beagles might decompose the adenovirus. Therefore, suitable formulation for adenovirus-based oral vaccine should be considered and developed. The chimpanzee adenovirus-vectored rabies vaccine ChAd68-Gp warrants extensive test for clinical application.

Influenza Vaccine With Consensus Internal Antigens as Immunogens Provides Cross-Group Protection Against Influenza A Viruses

Given that continuing antigenic shift and drift of influenza A viruses result in the escape from previous vaccine-induced immune protection, a universal influenza vaccine has been actively sought. However, there were very few vaccines capable of eliciting cross-group ant-influenza immunity. Here, we designed two novel composite immunogens containing highly conserved T-cell epitopes of six influenza A virus internal antigens, and expressed them in DNA, recombinant adenovirus-based (AdC68) and recombinant vaccinia vectors, respectively, to formulate three vaccine forms. The introduction of the two immunogens via a DNA priming and viral vectored vaccine boosting modality afforded cross-group protection from both PR8 and H7N9 influenza virus challenges in mice. Both respiratory residential and systemic T cells contributed to the protective efficacy. Intranasal but not intramuscular administration of AdC68 based vaccine was capable of raising both T cell subpopulations to confer a full protection from lethal PR8 and H7N9 challenges, and blocking the lymphatic egress of T cells during challenges attenuated the protection. Thus, by targeting highly conserved internal viral epitopes to efficiently generate both respiratory and systemic memory T cells, the sequential vaccination strategy reported here represented a new promising candidate for the development of T-cell based universal influenza vaccines.

A review of 65 years of human adenovirus seroprevalence

Introduction: Human adenovirus (HAdV)-derived vectors have been used in numerous pre-clinical and clinical trials during the last 40 years. Current research in HAdV-based vaccines focuses on improving transgene immunogenicity and safety. Because pre-existing humoral immunity against HAdV types correlate with reduced vaccine efficacy and safety, many groups are exploring the development of HAdV types vectors with lower seroprevalence. However, global seroepidemiological data are incomplete. Areas covered: The goal of this review is to centralize 65 years of research on (primarily) HAdV epidemiology. After briefly addressing adenovirus biology, we chronical HAdV seroprevalence studies and highlight major milestones. Finally, we analyze data from about 50 studies with respect to HAdVs types that are currently used in the clinic, or are in the developmental pipeline. Expert opinion: Vaccination is among the most efficient tools to prevent infectious disease. HAdV-based vaccines have undeniable potential, but optimization is needed and antivector immunity remains a challenge if the same vectors are to be administrated to different populations. Here, we identify gaps in our knowledge and the need for updated worldwide epidemiological data.

Adenovirus 5 produces obesity and adverse metabolic, morphological, and functional changes in the long term in animals fed a balanced diet or a high-fat diet: a study on hamsters

Adenovirus 5 (Ad-5) infection is a common cause of acute respiratory infections and the main vector used in gene therapy. There are few studies on the relationship of Ad-5 to obesity. In the present study, we evaluated the chronic effects of Ad-5 infection on golden (Syrian) hamsters fed either a balanced diet (BD) or a high-fat diet (HFD). After a single inoculation with Ad-5 (1 × 10⁷ pfu), the body weight of the animals was measured weekly. Medium-term (22 weeks) serum biochemical analyses and long-term (44 weeks) liver morphology, adiposity, and locomotive functionality (movement velocity) assessments were carried out. In the animals fed the BD, adenovirus infection produced hyperglycemia and hyperlipidemia. In the long term, it produced a 57% increase in epididymal pad fat and a 30% body weight gain compared with uninoculated animals. In addition, morphological changes related to non-alcoholic fatty liver disease (NAFLD) were observed. The animals fed the HFD had similar but more severe changes. In addition, the hamsters presented an obesity paradox: at the end of the study, the animals that had the most morphological and functional changes (significantly reduced movement velocity) had the lowest body weight. Despite the fact that an HFD appears to be a more harmful factor in the long term than adenovirus infection alone, infection could increase the severity of harmful effects in individuals with an HFD. Epidemiological studies are needed to evaluate the effect of adenovirus as a precursor of chronic liver and cardiovascular diseases, including the chronic effects of gene therapy.

The emerging role of oncolytic virus therapy against cancer

This review discusses current clinical advancements in oncolytic viral therapy, with a focus on the viral platforms approved for clinical use and highlights the benefits each platform provides. Three oncolytic viruses (OVs), an echovirus, an adenovirus, and a herpes simplex-1 virus, have passed governmental regulatory approval in Latvia, China, and the USA and EU. Numerous other recombinant viruses from diverse families are in clinical testing in cancer patients and we highlight the design features of selected examples, including adenovirus, herpes simplex virus, measles virus, retrovirus, reovirus, vaccinia virus, vesicular stomatitis virus. Lastly, we provide thoughts on the path forward for this rapidly expanding field especially in combination with immune modulating drugs.

Seroprevalence of Neutralizing Antibodies against Human Adenovirus Type-5 and Chimpanzee Adenovirus Type-68 in Cancer Patients

Since the preclinical results about chimpanzee adenovirus serotype-68 (AdC68)-based vaccine showed an encouraging results, it reminded us that AdC68 may be a suitable cancer vaccine vector. Previous study indicated that the seroprevalence of neutralizing antibodies (NAbs) against adenovirus was different between cancer patients and healthy volunteers. Knowledge regarding the prevalence rates of AdC68 NAbs for cancer patients is lacking. Therefore, assessing the preexistence of NAbs against AdC68 in cancer patients could provide useful insights for developing future AdC68-based cancer vaccines. In this study, 440 patients with different pathological types of tumors and 204 healthy adult volunteers were enrolled to evaluate the NAbs against AdC68 and human adenovirus serotype-5 (AdHu5). The seroprevalence of NAbs against AdC68 was much lower than that against AdHu5 in cancer subjects (43.64 vs. 67.05%, P < 0.01). The seroprevalence rates of NAbs to AdC68 in the cancer subjects were statistically higher than those detected in the healthy adult volunteers (43.64 vs. 23.53%, P = 0.000). The seroprevalence rates of AdC68 NAbs were much lower in lung, laryngeal, esophageal, and cervical cancer patients compared with oropharyngeal, colon, and rectal cancer patients. Furthermore, the seroprevalence rates of AdC68 NAbs were much lower in lung adenocarcinoma patients than in lung squamous cell carcinoma patients (35.00 vs. 70.00%, P < 0.05). No significant difference in the AdC68 NAbs among patients with different clinical stages of cancer was detected. The percentage of NAbs against AdC68 was significantly lower than that against AdHu5 (P < 0.05) in stage-I, -II, and -III cancer patients. No significant difference between the percentage of NAbs against AdC68 and AdHu5 in the subjects with stage-IV cancer was detected. The study also demonstrated the distribution of AdHu5 and AdC68 NAb titers for the positive samples. It showed that very low NAb titers against AdC68 with respect to AdHu5 in both healthy subjects and cancer subjects, especially in lung, laryngeal, esophageal, gastric, and cervical carcinomas. Also, the titer of NAbs against AdC68 was significantly lower than that against AdHu5 in the same clinical stage and age group (P < 0.05). Taken together, the present study showed that NAbs against AdC68 is much lower than AdHu5, especially in lung adenocarcinoma, laryngeal cancer, esophageal cancer, and cervical cancer patients. These results provided strong support for candidating AdC68 as a suitable vector of cancer vaccines.

Prevalence of serum neutralizing antibodies to adenovirus type 5 (Ad5) and 41 (Ad41) in children is associated with age and sanitary conditions

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Serum neutralizing antibodies to Ad5 and Ad41 in adults and children were titrated.

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Prevalence of NAb in children was associated with age and sanitary conditions.

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NAb titer distribution pattern was very different between Ad5 an Ad41.

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Ad41 vectored vaccine candidates might have a bright future.

Neutralizing antibody (NAb) can dampen the immunogenicity of adenovirus (Ad) vector-based vaccine. Vector systems based on human adenovirus type 41 (Ad41) have been constructed and used to develop recombinant vaccines. Here, we attempted to study the seroprevalence of NAbs to Ad5 and Ad41 among children and adults in Qinghai province, China. The positive rates (titer ⩾ 40) of Ad5 and Ad41 NAb in adults from Xining city were 75.7% and 94.7%, respectively. The moderate/high-positive rates (titer ⩾ 160) of NAb were quite close between the two viruses in adults (70.4% for Ad5 and 73.5% for Ad41). Age-dependent increase of NAb seroprevalence was observed for both viruses in children. NAb-positive rate of Ad41 reached 50% at 3.3–4.6 years of age for children from Chengxi district, Xining city, approximately 1.5 years earlier than that of Ad5 did. Interestingly, NAb level was also associated with sanitary conditions among young children. For Ad5, 8–15% children (0.2–3.0 years of age) from city or town, where the sanitations were relatively better, had moderate/high-positive NAb, while the same rate was 62% for children from villages. For Ad41, 22% children from city, 47% from town and 88% from villages possessed moderate/high-positive NAb. The possible influence of NAb titer distributions on the application of Ad41-vectored vaccines was discussed in detail. Our results suggested that children from places with poor sanitations should be included for comprehensive Ad NAb seroprevalence studies, and provided insights to the applications of Ad41 vectors.

Chimpanzee adenoviral vectors as vaccines - challenges to move the technology into the fast lane

INTRODUCTION

In recent years, replication-defective chimpanzee-derived adenoviruses have been extensively evaluated as genetic vaccines. These vectors share desirable properties with human adenoviruses like the broad tissue tropism and the ease of large-scale manufacturing. Additionally, chimpanzee adenoviruses have the advantage to overcome the negative impact of pre-existing anti-human adenovirus immunity. Areas covered: Here the authors review current pre-clinical research and clinical trials that utilize chimpanzee-derived adenoviral vectors as vaccines. A wealth of studies are ongoing to evaluate different vector backbones and administration routes with the aim of improving immune responses. The challenges associated with the identification of an optimal chimpanzee vector and immunization strategies for different immunological outcomes will be discussed. Expert commentary: The demonstration that chimpanzee adenoviruses can be safely used in humans has paved the way to the use of a whole new array of vectors of different serotypes. However, so far no predictive signature of vector immunity in humans has been identified. The high magnitude of T cell responses elicited by chimpanzee adenoviruses has allowed dissecting the qualitative aspects that may be important for protective immunity. Ultimately, only the results from the most clinically advanced products will help establish the efficacy of the vaccine vector platform in the field of disease prevention.

Seroprevalence of neutralizing antibodies against adenovirus type 14 and 55 in healthy adults in Southern China

Re-emerging human adenovirus types 14 (Ad14) and 55 (Ad55) have caused severe respiratory diseases and even deaths during recent outbreaks. However, the seroprevalence of neutralizing antibodies (nAbs) in healthy adults, which may reflect previous circulation and help to predict potential outbreaks, remains unclear. In this study, we established micro-neutralizing (MN) assays on the basis of recombinant Ad14 and Ad55 reporter viruses, and we investigated serum nAbs in healthy blood donors from Southern China. We found that the overall seropositive rates were 24.8% and 22.4% for Ad14 and Ad55 nAbs, respectively. The seropositive rates were low in individuals younger than 20, and they gradually increased with age. Ad55-seropositive individuals tended to have high nAb titers (>1000), while low (72–200) and moderate (201–1000) nAb levels were frequently observed in Ad14-seropositive ones. Surprisingly, the seropositive rates and nAb levels were associated with the blood type but not the gender of the blood donors, with type AB individuals displaying higher seropositive rates and nAb levels. Interestingly, a significant positive correlation was observed between Ad14 and Ad55 seroprevalence, and higher titers of nAbs were detected in double-positive individuals compared to single-positive ones. These results clarified the human humoral immune responses against Ad14 and Ad55 and revealed a low level of herd immunity in some subpopulations, which emphasized the importance of monitoring these two highly virulent adenoviruses and reinforced the development of prophylactic vaccines.

Both haemagglutinin-specific antibody and T cell responses induced by a chimpanzee adenoviral vaccine confer protection against influenza H7N9 viral challenge

Since 2013, the outbreak or sporadic infection of a new reassortant H7N9 influenza virus in China has resulted in hundreds of deaths and thousands of illnesses. An H7N9 vaccine is urgently needed, as a licensed human vaccine against H7N9 influenza is currently not available. Here, we developed a recombinant adenovirus-based vaccine, AdC68-H7HA, by cloning the H7N9 haemagglutinin (HA) gene into the chimpanzee adenoviral vector AdC68. The efficacy of AdC68-H7HA was evaluated in mice as well as guinea pigs. For comparison, an H7N9 DNA vaccine based on HA was also generated and tested in mice and guinea pigs. The results demonstrated that both AdC68-H7HA and the DNA vaccine prime-adenovirus boost regimen induced potent immune responses in animals and completely protected mice from lethal H7N9 influenza viral challenge. A post-immunization serum transfer experiment showed that antibody responses could completely protect against lethal challenge, while a T cell depletion experiment indicated that HA-specific CD8⁺ T cells responses also contributed to protection. Therefore, both HA-specific humoral immunity and cellular immunity play important roles in the protection. These data suggest that the chimpanzee adenovirus expressing HA is a promising vaccine candidate for H7N9 virus or other influenza viral subtypes.

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.