Proof-of-concept for a virus-induced obesity vaccine; vaccination against the obesity agent adenovirus 36

E4orf1: The triple agent of adenovirus - Unraveling its roles in oncogenesis, infectious obesity and immune responses in virus replication and vector therapy

Human Adenoviruses (HAdV) are nearly ubiquitous pathogens comprising numerous sub-types that infect various tissues and organs. Among many encoded proteins that facilitate viral replication and subversion of host cellular processes, the viral E4orf1 protein has emerged as an intriguing yet under-investigated player in the complex interplay between the virus and its host. E4orf1 has gained attention as a metabolism activator and oncogenic agent, while recent research is showing that E4orf1 may play a more important role in modulating cellular pathways such as PI3K-Akt-mTOR, Ras, the immune response and further HAdV replication stages than previously anticipated. In this review, we aim to explore the structure, molecular mechanisms, and biological functions of E4orf1, shedding light on its potentially multifaceted roles during HAdV infection, including metabolic diseases and oncogenesis. Furthermore, we discuss the role of functional E4orf1 in biotechnological applications such as Adenovirus (AdV) vaccine vectors and oncolytic AdV. By dissecting the intricate relationships between HAdV types and E4orf1 proteins, this review provides valuable insights into viral pathogenesis and points to promising areas of future research.

Adenovirus 36 infection and obesity risk: current understanding and future therapeutic strategies

INTRODUCTION

Obesity, a multifactorial disease caused by the interaction between genetic characteristics, metabolism, lifestyle, and environmental factors, is a major global health problem and is currently defined as a pandemic phenomenon. This disease is determined by an interaction of several factors, but the imbalance between energy consumption and expenditure seems to be the crucial point. In some cases, there is no linearity between exposure to those factors that cause the onset of obesity. A striking example of the occurrence of obesity despite no obvious risk factors is that of obesity induced by viral infections. The most important of such viruses appears to be human adenovirus 36 (Adv36).

AREAS COVERED

This review covers the relation between obesity and infection by Adv36 in humans. Also, discussed are the opportunities of prevention or treatment for the effects of Adv36 in human body.

EXPERT OPINION

The role of Ad36 in the development of obesity has already been established. Future research should focus on the development of vaccines against this agent, drug discovery for infected individuals, and effective therapeutic uses of E4orf1 gene protein for diabetes and other diseases in clinical practice.

Multifactorial Basis and Therapeutic Strategies in Metabolism-Related Diseases

Throughout the 20th and 21st centuries, the incidence of non-communicable diseases (NCDs), also known as chronic diseases, has been increasing worldwide. Changes in dietary and physical activity patterns, along with genetic conditions, are the main factors that modulate the metabolism of individuals, leading to the development of NCDs. Obesity, diabetes, metabolic associated fatty liver disease (MAFLD), and cardiovascular diseases (CVDs) are classified in this group of chronic diseases. Therefore, understanding the underlying molecular mechanisms of these diseases leads us to develop more accurate and effective treatments to reduce or mitigate their prevalence in the population. Given the global relevance of NCDs and ongoing research progress, this article reviews the current understanding about NCDs and their related risk factors, with a focus on obesity, diabetes, MAFLD, and CVDs, summarizing the knowledge about their pathophysiology and highlighting the currently available and emerging therapeutic strategies, especially pharmacological interventions. All of these diseases play an important role in the contamination by the SARS-CoV-2 virus, as well as in the progression and severity of the symptoms of the coronavirus disease 2019 (COVID-19). Therefore, we briefly explore the relationship between NCDs and COVID-19.

Adenovirus-36 infection and obesity: A case control study of Turkish women with polycystic ovary syndrome

BACKGROUND AND AIMS

Adenovirus-36 (Ad-36) seropositivity has been shown to be involved in the aetiology of obesity. The aim of this study was to examine Ad-36 positivity in obese and normal-weight patients with polycystic ovary syndrome (PCOS).

METHODS

There were two groups including 92 and 110 subjects. This study was a prospective case-control study. The enzyme-immunoassay method was used to quantitatively determine antibodies (Abs) specific to human Ad-36 in the serum samples. Age, body mass index (BMI), fasting glucose levels and insulin levels of the participants were recorded. The PCOS and control group patients were divided into two groups: the overweight group with BMI ≥25 kg/m² and non-obese group with BMI <25 kg/m².

RESULTS

Ad-36 Ab positivity in the PCOS group was found to be significantly higher than that in the control group (p < 0.001). Ad-36 Ab positivity was significantly higher in the PCOS obese group than in the control obese group (p < 0.001). Ad-36 Ab positivity and BMI ≥25 kg/m² were identified as independent predictors of PCOS in logistic regression analysis.

CONCLUSION

Ad-36 Ab positivity was significantly higher in the obese/overweight PCOS patients. Obesity can be prevented in patients with PCOS by treating Ad-36.

Modulating effect of vitamin D status on serum anti-adenovirus 36 antibody amount in children with obesity: National Food and Nutrition Surveillance

Background

The association of ADV-36 infection and obesity has been reported in children.

The objective of this study was to examine the hypothesis that the association between ADV-36 infection and adiposity may be mediated by sub-optimal vitamin D status of the host.

Methods

Ninety one apparently healthy children in different weight categories (normal weight: 33, overweight: 33, obesity: 25) aged 5–18 years were randomly selected from the registered population at National Food and Nutrition Surveillance Program (NFNS). The groups were matched based on age and sex. Anthropometric, biochemical and serological assessments were performed.

Results

The amount of anti-ADV36-Ab increased whereas circulating concentrations of 25(OH) D decreased across BMI categories with higher amounts in children with normal weight than in children with overweight and obesity (31.0 ± 16.4, 22.5 ± 10.5 and 21.9 ± 9.8 nmol/L, respectively, p = 0.004). Logistic regression analysis revealed that for each unit increment of anti-ADV36-Ab, the chance of increase in weight was 8.5 times (OR: 8.5, p = 0.029). Interestingly, when 25(OH) D was introduced into the model, anti-ADV36-Ab was no longer the predictor of weight increment and the chance of increase in weight reduced 5% for each unit increase in 25(OH) D concentration (OR: 0.95, p = 0.012).

Conclusion

It is suggested that ADV36-induced lipogenesis may be mediated by vitamin D deficiency in children with obesity.

Tratamento farmacológico da obesidade: passado, presente e futuro

O tratamento da obesidade deve ser baseado na percepção de que a obesidade é uma enfermidade crônica, neuroquímica e recidivante. Sendo assim, a combinação de eficácia, sustentabilidade de longo prazo e perfil de segurança de excelência devem nortear a utilização dos medicamentos disponíveis assim como das novas moléculas vindouras. No momento, a liraglutida parece ser a mais completa droga para a obesidade como doença crônica, mas certamente deverá ser superada pelos novos peptídeos de múltiplo agonismo e/ou pela combinação de várias medicações ainda não disponíveis em baixas dosagens para pacientes precisa e individualmente selecionados.

Twenty-five years of research about adipogenic adenoviruses: A systematic review

Infectious etiology is implicated in chronic diseases such as gastric ulcer or atherosclerosis. However, "infection" is a recent term in the field of obesity. Since the first report in 1982 of obesity due to infection, several microbes have been linked to obesity. Among the adipogenic microbes, avian adenovirus SMAM-1 and human adenovirus Ad36 have been studied most extensively for the past 25 years. Here, we present a systematic review of literature about SMAM-1 and Ad36. Reports from North America, Europe, and Asia reveal strong evidence that Ad36 causes obesity in animals and paradoxically improves glycemic control, and in vitro data provides mechanistic explanation. Considering that experimental Ad36 infection of humans is unlikely, its causative role in human obesity or glycemic control has not been demonstrated unequivocally. Nonetheless, most, but not all, observational studies in children and adults link Ad36 infection to obesity and improvement in glycemic control. The E4orf1 gene of Ad36 was identified as responsible for better glycemic control. Overall, 25 years have considerably advanced knowledge about the role of infection in obesity. Potential translational benefits include the development of vaccines to prevent Ad36-induced obesity and drug development based on the E4orf1 protein to improve glycemic control.

Comment on Khanal et al. The Repertoire of Adenovirus in Human Disease: The Innocuous to the Deadly. Biomedicines 2018, 6, 30

In their comprehensive review on adenoviruses, Khanal et al. omitted obesity as a disease caused by adenovirus 36 (Adv36). Animal studies have shown that experimental infection with Adv36 causes increased adiposity, and human association studies have shown that prior infection with Adv36 is correlated with greater body weight in humans in multiple countries of the world.

Future Pharmacotherapy for Obesity: New Anti-obesity Drugs on the Horizon

PURPOSE OF REVIEW

Obesity is a global health crisis with detrimental effects on all organ systems leading to worsening disease state and rising costs of care. Persons with obesity failing lifestyle therapies need to be escalated to appropriate pharmacological treatment modalities, medical devices, and/or bariatric surgery if criteria are met and more aggressive intervention is needed. The progression of severe obesity in the patient population coupled with related co-morbidities necessitates the development of novel therapies for the treatment of obesity. This development is preceded by increased understanding of the underpinnings of energy regulation and neurohormonal pathways involved in energy homeostasis.

RECENT FINDINGS

Though there are approved anti-obesity drugs available in the USA, newer drugs are now in the pipeline for development given the urgent need. This review focuses on anti-obesity drugs in the pipeline including centrally acting agents (setmelanotide, neuropeptide Y antagonist [velneperit], zonisamide-bupropion [Empatic], cannabinoid type-1 receptor blockers), gut hormones and incretin targets (new glucagon-like-peptide-1 [GLP-1] analogues [semaglutide and oral equivalents], amylin mimetics [davalintide, dual amylin and calcitonin receptor agonists], dual action GLP-1/glucagon receptor agonists [oxyntomodulin], triple agonists [tri-agonist 1706], peptide YY, leptin analogues [combination pramlintide-metreleptin]), and other novel targets (methionine aminopeptidase 2 inhibitor [beloranib], lipase inhibitor [cetilistat], triple monoamine reuptake inhibitor [tesofensine], fibroblast growth factor 21), including anti-obesity vaccines (ghrelin, somatostatin, adenovirus36). With these new drugs in development, anti-obesity therapeutics have potential to vastly expand allowing better treatment options and personalized approach to obesity care.

Is early life exposure to polyomaviruses and herpesviruses associated with obesity indices and metabolic traits in childhood?

BACKGROUND

Evidence for an infectious origin of obesity is emerging. We explored whether common viruses were associated with obesity and metabolic traits.

METHODS

We used cross-sectional (n = 674) and prospective (n = 440) data from children participating at the 4 and 6 years of age follow-up in the Rhea birth cohort. Presence of IgG antibodies to ten polyomaviruses (BKPyV, JCPyV, KIPyV, WUPyV, HPyV6, HPyV7, TSPyV, MCPyV, HPyV9, and HPyV10) and four herpesviruses (EBV, CMV, HSV-1, and HSV-2) were measured at age 4. Body mass index, waist circumference, and skinfold thickness were measured at age 4 and 6. Data on serum lipids, leptin, and adiponectin were also available. Multivariable linear regression models were used to explore the associations.

RESULTS

At 4 years of age, seroprevalence to polyomaviruses ranged from 21.0% for HPyV9 to 82.0% for HPyV10. Seroprevalence for EBV, CMV, HSV-1, and HSV-2 was 53.0%, 26.0%, 3.6%, and 1.5% respectively. BKPyV seropositivity was associated with lower BMI SD score at age 4 [-0.21 (95% CI: -0.39, -0.03)] and 6 [-0.27 (95% CI:-0.48, -0.05)], waist circumference at age 4 [-1.12 cm (95% CI: -2.10, -0.15)] and 6 [-1.73 cm (95% CI: -3.33, -0.12)], sum of four skinfolds [-2.97 mm (95% CI: -5.70, -0.24)], and leptin levels at age 4 [ratio of geometric means, 0.83 (95% CI: 0.70, 0.98)]. CMV seropositivity was associated with higher BMI SD score at age 4 [0.28 (95% CI: 0.11, 0.45)] and 6 [0.24 (95% CI: 0.03, 0.45)] and sum of four skinfolds at age 6 [4.75 mm (95% CI: 0.67, 8.83)]. Having "2-3 herpesviruses infections" (versus "0 herpesvirus infections") was associated with higher BMI SD score [0.32, (95% CI: 0.12, 0.53)], waist circumference [1.22 cm (95% CI: 0.13, 2.31)], and sum of four skinfolds [3.26 mm (95% CI: 0.18, 6.35)] at age 4. Polyomaviruses burden was not associated with outcomes.

CONCLUSIONS

A higher herpesviruses burden and CMV seropositivity were associated with obesity traits in childhood.

Viral Infections and Obesity

PURPOSE OF REVIEW

Obesity is a multifactorial disease that is now endemic throughout most of the world. Although addressing proximate causes of obesity (excess energy intake and reduced energy expenditure) have been longstanding global health priorities, the problem has continued to worsen at the global level.

RECENT FINDINGS

Numerous microbial agents cause obesity in various experimental models-a phenomena known as infectobesity. Several of the same agents alter metabolic function in human cells and are associated with human obesity or metabolic dysfunction in humans. We address the evidence for a role in the genesis of obesity for viral agents in five broad categories: adenoviridae, herpesviridae, phages, transmissible spongiform encephalopathies (slow virus), and other encephalitides and hepatitides. Despite the importance of this topic area, there are many persistent knowledge gaps that need to be resolved. We discuss factors motivating further research and recommend that future infectobesity investigation should be more comprehensive, leveraged, interventional, and patient-centered.

Obesity and Infection: Reciprocal Causality

Associations between different infectious agents and obesity have been reported in humans for over thirty years. In many cases, as in nosocomial infections, this relationship reflects the greater susceptibility of obese individuals to infection due to impaired immunity. In such cases, the infection is not related to obesity as a causal factor but represents a complication of obesity. In contrast, several infections have been suggested as potential causal factors in human obesity. However, evidence of a causal linkage to human obesity has only been provided for adenovirus 36 (Adv36). This virus activates lipogenic and proinflammatory pathways in adipose tissue, improves insulin sensitivity, lipid profile and hepatic steatosis. The E4orf1 gene of Adv36 exerts insulin senzitizing effects, but is devoid of its pro-inflammatory modalities. The development of a vaccine to prevent Adv36-induced obesity or the use of E4orf1 as a ligand for novel antidiabetic drugs could open new horizons in the prophylaxis and treatment of obesity and diabetes. More experimental and clinical studies are needed to elucidate the mutual relations between infection and obesity, identify additional infectious agents causing human obesity, as well as define the conditions that predispose obese individuals to specific infections.

Role of adenoviruses in obesity

Five human adenovirus subtypes, Ad5, Ad9, Ad31, Ad36, and Ad37, and a non-human adenovirus, SMAM1, are linked to increased adiposity in vitro or in vivo. Experimental infection with Ad5, Ad36, and Ad37 produced excess adiposity or weight gain in animals. Ad9 and Ad31 increase fat storage in tissue culture but are not associated with animal or human obesity. Ad36 is the most extensively studied adipogenic adenovirus and is correlated with some measure of overweight/obesity in humans from multiple countries. The correlation is strongest and most consistent in children, but some studies have been negative in both children and adults. About 30% of overweight/obese children and adults and about 15-20% of lean individuals have Ad36 antibodies in epidemiologic studies. The mechanisms of action of Ad36 are due to the early gene 4, open reading frame 1 (E4-ORF1). Blocking E4-ORF1 with siRNA prevents the effects of Ad36, and transfection of lentivirus with E4-ORF1 reproduces the Ad36 effects. Increased adiposity is caused by stimulation of at least three pathways by Ad36. Cell membrane glucose receptors are increased via the Ras pathway, leading to increased intracellular glucose. Fatty acid synthase is increased, which converts the glucose to fatty acids. Finally, peroxisome proliferator-activated receptor-γ is increased, resulting in differentiation of adult stem cells into adipocytes.

CONCLUSIONS

several adenoviruses increase adiposity in animals and are associated with obesity in humans. There are critical gaps in the literature needing further investigation including evaluation of other adenovirus subtypes and better research designs to improve the strength of causal inferences.

Adenovirus 36 and Obesity: An Overview

There is an epidemic of obesity starting about 1980 in both developed and undeveloped countries definitely associated with multiple etiologies. About 670 million people worldwide are obese. The incidence of obesity has increased in all age groups, including children. Obesity causes numerous diseases and the interaction between genetic, metabolic, social, cultural and environmental factors are possible cofactors for the development of obesity. Evidence emerging over the last 20 years supports the hypothesis that viral infections may be associated with obesity in animals and humans. The most widely studied infectious agent possibly linked to obesity is adenovirus 36 (Adv36). Adv36 causes obesity in animals. In humans, Adv36 associates with obesity both in adults and children and the prevalence of Adv36 increases in relation to the body mass index. In vivo and in vitro studies have shown that the viral E4orf1 protein (early region 4 open reading frame 1, Adv) mediates the Adv36 effect including its adipogenic potential. The Adv36 infection should therefore be considered as a possible risk factor for obesity and could be a potential new therapeutic target in addition to an original way to understand the worldwide rise of the epidemic of obesity. Here, the data indicating a possible link between viral infection and obesity with a particular emphasis to the Adv36 will be reviewed.