UNASSIGNED: Fowl adenovirus (FAdV) is a significant pathogen in poultry, causing various diseases such as hepatitis-hydropericardium, inclusion body hepatitis, and gizzard erosion. Different serotypes of FAdV are associated with specific conditions, highlighting the need for targeted prevention strategies. Given the rising prevalence of FAdV-related diseases globally, effective vaccination and biosecurity measures are crucial. In this study, we explore the potential of structural proteins to design a multi-epitope vaccine targeting FAdV.
UNASSIGNED: We employed an in silico approach to design the multi-epitope vaccine. Essential viral structural proteins, including hexon, penton, and fiber protein, were selected as vaccine targets. T-cell and B-cell epitopes binding to MHC-I and MHC-II molecules were predicted using computational methods. Molecular docking studies were conducted to validate the interaction of the multi-epitope vaccine candidate with chicken Toll-like receptors 2 and 5.
UNASSIGNED: Our in silico methodology successfully identified potential T-cell and B-cell epitopes within the selected viral structural proteins. Molecular docking studies revealed strong interactions between the multi-epitope vaccine candidate and chicken Toll-like receptors 2 and 5, indicating the structural integrity and immunogenic potential of the designed vaccine.
UNASSIGNED: The designed multi-epitope vaccine presents a promising approach for combating FAdV infections in chickens. By targeting essential viral structural proteins, the vaccine is expected to induce a robust immunological response. The in silico methodology utilized in this study provides a rapid and cost-effective means of vaccine design, offering insights into potential vaccine candidates before experimental validation. Future studies should focus on in vitro and in vivo evaluations to further assess the efficacy and safety of the proposed vaccine.

Numerous human adenovirus (AdV) types are endowed with arginine-glycine-aspartic acid (RGD) sequences that enable them to recognize vitronectin-binding (αv) integrins. These RGD-binding cell receptors mediate AdV entry into host cells, a crucial early step in virus infection. Integrin interactions with adenoviruses not only initiate receptor-mediated endocytosis but also facilitate AdV capsid disassembly, a prerequisite for membrane penetration by AdV protein VI. This review discusses fundamental aspects of AdV-host interactions mediated by integrins. Recent efforts to re-engineer AdV vectors and non-viral nanoparticles to target αv integrins for bioimaging and the eradication of cancer cells will also be discussed.

Hepatitis-hydropericardium syndrome (HHS), caused by fowl adenovirus serotype 4 (FAdV-4), has been widely spread across China, resulting in great financial losses in the poultry industry. Therefore, efficient vaccines against this disease urgently need to be developed. In our study, the fiber-2 and penton base proteins derived from the FAdV-4 JS strain were expressed in a prokaryotic system (E. coli) in a soluble form. Then, the efficacy of the two recombinant proteins formulated with cheap and widely used adjuvants (Marcol™ 52 white oil) were respectively tested, and the minimum immune doses and safety of the above proteins were also determined. It was indicated that the fiber-2 (20 µg/bird, 200 µg/bird) and penton base (200 µg/bird) could provide complete protection against the highly pathogenic FAdV-4 and suppress its replication and shedding. Unfortunately, only the fiber-2 protein could induce complete protection (10/10) at a low dose (10 µg/bird). In addition, we confirmed that the fiber-2 subunit vaccine formulated with oil adjuvants was safe for vaccinated chickens. Conclusively, all of our results suggest that we successfully prepared an efficient and cheap fiber-2 subunit vaccine with few side effects.

In the present study, 31 samples (12 fecal, 9 nasal and 10 rectal swabs) from 28/92 (30.43%, 10 captive and 18 free-roaming African green monkeys (AGMs, Chlorocebus sabaeus)) apparently healthy AGMs in the Caribbean Island of St. Kitts tested positive for adenoviruses (AdVs) by DNA-dependent DNA polymerase (pol)-, or hexon-based screening PCR assays. Based on analysis of partial deduced amino acid sequences of Pol- and hexon- of nine AGM AdVs, at least two AdV genetic variants (group-I: seven AdVs with a Simian mastadenovirus-F (SAdV-F)/SAdV-18-like Pol and hexon, and group-II: two AdVs with a SAdV-F/SAdV-18-like Pol and a Human mastadenovirus-F (HAdV-F)/HAdV-40-like hexon) were identified, which was corroborated by analysis of the nearly complete putative Pol, complete hexon, and partial penton base sequences of a representative group-I (strain KNA-08975), and -II (KNA-S6) AdV. SAdV-F-like AdVs were reported for the first time in free-roaming non-human primates (NHPs) and after ~six decades from captive NHPs. Molecular characterization of KNA-S6 (and the other group-II AdV) indicated possible recombination and cross-species transmission events involving SAdV-F-like and HAdV-F-like viruses, corroborating the hypothesis that the evolutionary pathways of HAdVs and SAdVs are intermingled, complicated by recombination and inter-species transmission events, especially between related AdV species, such as HAdV-F and SAdV-F. To our knowledge, this is the first report on detection and molecular characterization of AdVs in AGMs.

Inclusion body hepatitis (IBH) is a metabolic disease affecting chickens, associated with different serotypes of fowl adenovirus (FAdV). Experimentally tested vaccines against IBH include several capsid-based subunit vaccines, but not the penton base protein. In the present study, specific pathogen-free chickens were vaccinated with recombinant penton base expressed from each of two different FAdV serotypes (FAdV-7 and FAdV-8b), followed by challenge with a virulent IBH-causing strain. No protection was observed with either vaccine, possibly due to the low immunogenicity of each protein and their inability to induce neutralizing antibodies in the host.

Macromolecular therapeutics such as nucleic acids, peptides, and proteins have the potential to overcome treatment barriers for cancer. For example, nucleic acid or peptide biologics may offer an alternative strategy for attacking otherwise undruggable therapeutic targets such as transcription factors and similar oncologic drivers. Delivery of biological therapeutics into tumor cells requires a robust system of cell penetration to access therapeutic targets within the cell interior. A highly effective means of accomplishing this may be borrowed from cell-penetrating pathogens such as viruses. In particular, the cell entry function of the adenovirus penton base capsid protein has been effective at penetrating tumor cells for the intracellular deposition of macromolecular therapies and membrane-impermeable drugs. Here, we provide an overview describing the evolution of tumor-targeted penton-base-derived nano-capsids as a framework for discussing the requirements for overcoming key barriers to macromolecular delivery. The development and pre-clinical testing of these proteins for therapeutic delivery has begun to also uncover the elusive mechanism underlying the membrane-penetrating function of the penton base. An understanding of this mechanism may unlock the potential for macromolecular therapeutics to be effectively delivered into cancer cells and to provide a treatment option for tumors resisting current clinical therapies.

In the current study, we have evaluated the protective efficacy of the \'insertion domain\' which is commonly found in the capsid penton base protein of many adenoviruses. Using the \'insertion domain\' of the penton base protein of a representative fowl adenovirus, fowl adenovirus serotype 4 (FAdV-4), we find that the \'insertion domain\' can readily be expressed in a soluble form in the bacterial system, and can be purified in sufficient quantities through simple chromatographic methods. We demonstrate that the \'insertion domain\', when employed as a subunit vaccine candidate, provides complete protection against hydropericardium syndrome, caused by FAdV-4, in chickens. The data presented here indicate that the protein, adjuvanted with Montanide™ ISA71 VG, provides complete protection in chickens against a lethal FAdV-4 challenge after administration of two doses (100 μg of the protein per dose) two weeks apart (the first dose at the 7th day of life and a booster dose at the age of 21 days). Furthermore, the purified protein can be stored at low temperatures without any observable loss in the protein integrity up to one year, tested so far. Due to the conserved nature of the \'insertion domain\' across the penton base protein of fowl adenoviruses, it is suggested that homologous insertion domains could be employed as highly stable and cost-effective subunit vaccine candidates against infections caused by respective fowl adenoviruses.

Human adenoviruses (HAdVs) are large (150 MDa), complex, nonenveloped dsDNA viruses that cause self-limiting respiratory, ocular and enteric infections. They are significant health hazard in young, elderly and immuno-compromised populations. Moreover, various adenoviruses (AdVs) of mammalian origin are being used as vectors in gene, vaccine and cancer therapies. Multiple copies of at least 13 different proteins, all in all ~2800 protein molecules, come together to form an adenovirus virion packaging the ~36 Kbp geome. The details of structural organization of the adenovirus capsid and underlying network of protein-protein interactions provide clues into designing the modified and novel adenovirus vectors with desired functionalities and/or targeting specificities. The advancements in 3D structure determination by cryo-electron microscopy (cryo-EM) in the past decade have enabled unveiling of the complex organization of adenovirus architecture at near atomic resolution. Specifically, these studies revealed the structures and the network of interactions involving cement/minor proteins in stabilizing the AdV icosahedral architecture, which appear to be mostly conserved among human adenoviruses. In this chapter, we describe the current state of knowledge on the structure and organization of human adenoviruses.

Hepatitis-hydropericardium syndrome (HHS) caused by hypervirulent fowl adenovirus 4 (FAdV-4) have been causing great economic losses to Chinese poultry industry since 2015. Elucidation of the pathogenesis of FAdV-4 will lay solid foundation for developing attenuated FAdV-4 vaccine and vaccine vector. Our previous study has demonstrated that the increased virulence of hypervirulent FAdV-4 was associated with fiber-2 and hexon genes. However, the roles of fiber-1 and penton in virulence of FAdV-4 have never been elucidated. To further investigate the roles of the major structural proteins fiber-1 and penton in the virulence of hypervirulent FAdV-4, the fiber-1- and penton-replaced mutant viruses were constructed based on the FAdV-4 infectious clones of hypervirulent strain HNJZ using Redαβ recombineering techniques. The pathogenicity of the rescued viruses was evaluated in 3-week-old SPF chickens. Chickens infected with the rescued recombinant viruses carrying the fiber-1 or penton base gene from a nonpathogenic strain ON1 developed similar clinical signs to the natural hypervirulent FAdV-4 infection, including HHS-indicative gross lesions and histopathological changes in sick/dead chickens. Our results suggested that the increased virulence of hypervirulent FAdV-4 was independent of fiber-1 and penton. The detailed pathogenesis of FAdV-4 and the roles of fiber-1 and penton in the viral replication and infection process need to be further explored.

Following receptor-mediated uptake into endocytic vesicles and subsequent escape, adenovirus particles are transported along microtubules. The microtubule motor proteins dynein and one or more kinesins are involved in this behavior. Dynein is implicated in adenovirus transport toward the nucleus. The kinesin Kif5B has now been found to move the adenovirus (AdV) toward microtubule plus ends, though a kinesin role in adenovirus-induced nuclear pore disruption has also been reported. In undifferentiated cells, dynein-mediated transport predominates early in infection, but motility becomes bidirectional with time. The latter behavior can be modeled as a novel assisted diffusion mechanism, which may allow virus particles to explore the cytoplasm more efficiently. Cytoplasmic dynein and Kif5B have both been found to bind AdV through direct interactions with the capsid proteins hexon and penton base, respectively. We review here the roles of the microtubule motor proteins in AdV infection, the relationship between motor protein recruitment to pathogenic vs. physiological cargoes, the evolutionary origins of microtubule-mediated AdV transport, and a role for the motor proteins in a novel host-defense mechanism.