Circumvention of Vector-Specific Neutralizing Antibody Response by Alternating Use of Human and Non-Human Adenoviruses: Implications in Gene Therapy

Abstract

To determine whether non-human adenovirus-specific antibodies are cross-neutralizing, rabbit and mouse anti-human adenovirus type 5 (HAd5), anti-bovine adenovirus type 3 (BAd3), and anti-porcine adenovirus type 3 (PAd3) sera were used in cross-virus neutralization assays. Adenovirus neutralizing antibodies were found to be virus-specific, suggesting that virus neutralizing epitope differs significantly in HAd5, BAd3, and PAd3. To further investigate whether immunity to an HAd5-derived vector could be circumvented by the use of non-human adenoviruses in vivo, mice were first immunized either intranasally or intraperitoneally with HAd5, BAd3, PAd3, or BAd3 + PAd3, and after development of adenovirus-specific antibodies, animals were inoculated with the HAd5 recombinant (AdCA36lacZ) containing the bacterial beta-galactosidase gene under the control of murine cytomegalovirus immediate-early promoter. Virus-inoculated animals developed virus-specific IgG and IgA antibodies. LacZ expression in animals initially primed with HAd5 was significantly reduced (P < 0.05), suggesting that the immune response against the vector could prevent the transgene expression following subsequent inoculation of the same vector, whereas LacZ expression in mice initially primed with BAd3, PAd3, or BAd3 + PAd3 was significantly higher (P > 0.05) than that obtained in HAd5-primed animals. Our results suggest that HAd5-, BAd3-, or PAd3-based vectors may be used sequentially for human gene therapy or vaccine production as a means to avoid immunity to the vector.

Encapsulation of recombinant adenovirus into alginate microspheres circumvents vector-specific immune response

“…This concept has been demonstrated previously. 13,44 However, in HAd5-immunized mice, transgene expression following inoculation with E-Z, ie AdCA36lacZ encapsulated into alginate microspheres, was slightly reduced (10% in 1 Â HAd5-immunized, and 20-25% in 2 Â HAd5-immunized) compared to levels obtained in naïve animals. Similar results were obtained with i.n.…”

“…with nonencapsulated-AdCA36lacZ (NE-Z), the maximum LacZ expression in various tissues was observed on day 1 post-inoculation. 13 In a preliminary study, the highest level of LacZ expression in different tissues of mice inoculated i.n. or i.p.…”

“…[40][41][42] and use of human and nonhuman adenovirus vectors in sequential administration. 13 However, it has been suggested that repeated intramuscular (i.m.) inoculation with helperdependent HAd vectors could be done even in the presence of pre-existing immunity.…”

“…[4][5][6] The cellular immune response against the vector may kill the transduced cells expressing viral and transgene products, [7][8][9][10] whereas the humoral response, especially neutralizing antibody, reduces virus uptake by the target cells on readministration of the same vector. [11][12][13] Moreover, pre-existing HAdneutralizing antibodies are common in the human population due to the ubiquitous nature of HAd serotypes, 14,15 and therefore, may interfere with transgene expression even upon the first inoculation of the vector.…”

“…5 Sequential administration of HAd, bovine adenovirus (BAd) and porcine adenovirus (PAd) could also circumvent vector-specific neutralizing immune response. 13 Masking of the capsid components of the virus by covalently linking polyethylene glycol (PEG) 21,22 or N-(2-hydroxypropyl)methacrylamide (HPMA) 23 is another approach to curtail antibody-mediated virus neutralization. Retargeting of adenoviral vectors to specific cell receptors other than coxsackie/adenoviral receptor (CAR) will not only provide a mean to target-specific cells but also elude immunity to the vector.…”