Protection of adenovirus from neutralizing antibody by cationic PEG derivative ionically linked to adenovirus

Abstract

Background:The generation of anti-adenovirus neutralizing antibody (NAb) in humans severely restricts the utilization of recombinant adenovirus serotype 5 (Ad5) vectors in gene therapy for a wide range of clinical trials. To overcome this limitation, we ionically complexed Ad5 with a newly synthesized copolymer, which we called APC, making an adenovirus shielded from NAb. Methods: APC, a cationic polyethylene glycol derivative, was synthesized via two steps of ring-opening copolymerization of ethylene oxide and allyl glycidyl ether, followed by the addition of 2-mercaptoethylamine. The copolymer or the control PEI-2k was ionically complexed to anionic Ad5 in 5% glucose, and in vitro transduction assays were carried out in coxsackievirus and adenovirus receptor-positive cells (A549) and coxsackievirus and adenovirus receptornegative cells (B16 and SKOV3). The physical properties and morphology of adenovirus alone or the complexes were investigated respectively by zeta potential, size distribution, and transmission electron microscopy image. Then cytotoxicity of APC was examined using 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide assays. Finally, the ability of APC to protect adenovirus from NAb was evaluated by transfection assays after a neutralizing effect. Results: APC was successfully synthesized and showed a low cytotoxicity. Positively charged Ad5/APC exhibited slightly increased diameter (130.2 ± 0.60 nm) than naked Ad5 (115.6 ± 5.46 nm) while Ad5/PEI-2k showed severe aggregation (1382 ± 79.9 nm). Ad5/APC achieved a gene transfection level as high as Ad5/PEI-2k in A549 or B16 cells, and significantly higher than Ad5/PEI-2k in SKOV3 cells. Most importantly, after the exposure to the neutralizing antibody, naked Ad5 and Ad5/PEI-2k exhibited poor gene expression while Ad5/APC still showed significantly efficient gene expression. Conclusion: Our results demonstrated that Ad5/APC complex offered good protection for Ad5 against NAb in vitro and suggested a potential strategy of resistance to NAb in vivo.

Systemic Administration and Targeted Delivery of Immunogenic Oncolytic Adenovirus Encapsulated in Extracellular Vesicles for Cancer Therapies

“…Thus, for solid tumors and disseminated malignancies, an innovative procedure for a systemic and targeted delivery of OV is highly warranted. To enhance OV delivery to neoplastic tissue, several approaches have been developed, including: (i) viral capsid modification with the addition of polyethylene glycol (PEG) polymers to reduce immunogenicity and increase the circulation time in the blood; an approach that, however, resulted also in a significant reduction of the viral infectivity [ 5 , 7 ]; (ii) the use of drug carrier systems, such as liposomes [ 8 , 9 ], to increase the tumor-specific transduction of OV; a strategy that demonstrated poor serum stability of the particles and induced immune rejections in the host, thus preventing its further development [ 10 ]; (iii) recent studies reported that OV can be selectively delivered into neoplastic cells by tumor microparticles for virotherapy [ 11 ].…”

Identification of Equid herpesvirus 2 in tissue-engineered equine tendon

“…To our knowledge, viral agents have not previously been isolated from tendons in horses. Zeng et al 30 used TEM to visualise adenovirus particles. Their TEM images suggest that adenoviruses are much smaller than the particles isolated in this experiment, with the approximate diameter being 70–90nm.…”

The Immune System – Friend or Foe for Adenovirus Based Therapies?

“…PEG is a long chain polymer, which when attached to Ads will protrude from the capsid in a hairlike manner [273]. Successful examples include O'Riordan [274], Wortmann et al [275] and Zeng et al [276], all of which found that they were able create shielded vectors able to evade neutralising anti-vector responses in vitro and in vivo. In vivo, PEG shielding also successfully prevented complement activation [190].…”