Circumvention of Anti-Adenovirus Neutralizing Immunity by Administration of an Adenoviral Vector of an Alternate Serotype

Abstract

Effective gene transfer and expression following repetitive administration of adenoviral (Ad) vectors in experimental animals is limited by anti-Ad neutralizing antibodies. Knowing that anti-Ad humoral immunity is serotype-specific, we hypothesized that anti-Ad neutralizing immunity could be circumvented using Ad vectors of different serotypes (Ad2, Ad5) within the same subgroup (C) to transfer and express beta-glucuronidase (beta glu) in the lung. Sprague-Dawley rats received an intratracheal administration of either Ad2 beta glu or Ad5 beta glu, and, 14 days later, repeat administration of either the same vector or a vector of a different serotype. Analysis of serum and bronchoalveolar lavage fluid following initial vector administration demonstrated systemic and local serotype-specific neutralizing antibodies. For both the Ad2 and Ad5 vectors, beta glu expression 24 hr following the second administration of the same serotype was < 30% of that of naive animals. In contrast, beta glu expression 24 hr following second administration of a different serotype Ad vector was similar to expression at 24 hr of naive animals receiving a single administration (Ad5 beta glu followed by Ad2 beta glu, as well as Ad2 beta glu followed by Ad5 beta glu; p > 0.2 both comparisons). Although the alternative serotype bypassed anti-Ad neutralizing immunity, persistence of expression was reduced compared to that following administration to naive animals. Compatible with this observation, systemic administration of the same vectors to C57B1/6 mice demonstrated induction of cytotoxic T lymphocytes directed against the beta glu transgene, as well as products of the Ad genome. Interestingly, intratracheal administration of vectors with different serotypes and different transgenes to rats resulted in longer expression (but still not normalized) compared to that achieved with vectors of different serotypes but the same transgene. These observations demonstrate that alternate use of Ad vectors from different serotypes within the same subgroup can circumvent anti-Ad humoral immunity to permit effective gene transfer after repeat administration, although the chronicity of expression is limited, likely by cellular immune process directed against both the transgene and viral gene products expressed by the vector.

Increased revascularization efficacy after administration of an adenovirus encoding VEGF121

“…Successful repeat administration of adenovirus has been achieved with serotype switching. [10][11][12] Neutralizing antibodies against one adenovirus serotype do not prevent infection by another adenovirus serotype, but this approach is rather limited in that it requires multiple adenoviral vectors to be constructed. Other attempts to avoid an immunologic response include engineering the adenovirus genome and capsid to minimize the expression of viral antigens, thus limiting the host's humoral immune response.…”

The extra- and intracellular barriers to lipid and adenovirus-mediated pulmonary gene transfer in native sheep airway epithelium

“…16 However, adenoviruses show inherent immunological problems, 17 resulting in reduction of gene expression on repeated application. Alterations in the adenovirus sero-type, 18 blocking antibodies to the CD40 antigen 19 and increasing deletions of the viral genome 20 have begun to address this problem. Both preclinical studies in primates and cotton rats 21,22 and clinical trials in man show adenoviruses are capable of producing an acute T cell-mediated inflammatory response.…”

Use of helper-dependent adenoviral vectors of alternative serotypes permits repeat vector administration

“…Neutralizing antibodies formed against one serotype should have no effect on subsequent delivery of a different serotype, and this approach has allowed repeat administration of firstgeneration Ad vectors. 46,[59][60][61] However, a reduced persistence of expression has been observed after the second administration, 60 presumably due to cross-reacting cytotoxic T lymphocytes which can eliminate the transduced cells. 62 Over 40 different serotypes of human Ads have been isolated, suggesting that, in theory, Ad vectors of different serotypes could be administered many times throughout the life of a patient.…”