Effect of tolerance induction to immunodominant T-cell epitopes of Sendai virus on gene expression following repeat administration to lung

Abstract

Sendai virus (SeV) is able to transfect airway epithelial cells efficiently in vivo. However, as with other viral vectors, repeated administration leads to reduced gene expression. We have investigated the impact of inducing immunological tolerance to immunodominant T-cell epitopes on gene expression following repeated administration. Immunodominant CD4 and CD8 T-cell peptide epitopes of SeV were administered to C57BL/6 mice intranasally 10 days before the first virus administration with transmission-incompetent F-protein-deleted DF/SeV-GFP. At 21 days after the first virus administration, mice were again transfected with DF/SeV. To avoid interference of anti-GFP antibodies, the second transfection was carried out with DF/SeV-lacZ.At 2 days after the final transfection lung b-galactosidase expression, T-cell proliferation and antibody responses were measured. A state of 'split tolerance' was achieved with reduced T-cell proliferation, but no impact on antiviral antibody production. There was no enhancement of expression on repeat administration; instead, T-cell tolerance was, paradoxically, associated with a more profound extinction of viral expression. Multiple immune mechanisms operate to eradicate viruses from the lung, and these findings indicate that impeding the adaptive T-cell response to the immunodominant viral epitope is not sufficient to prevent the process.

Validation of recombinant Sendai virus in a non-natural host model

“…20 We have previously shown that SeV administration evokes cellular and humoral immune responses in an animal model and that the level of neutralising antibodies (as measured by in vitro assays) increases after virus re-administration. 7 However, there was no correlation between neutralising antibody levels and residual gene expression (r 2 ¼0.046, P¼0.16). We have also shown that partial T-cell tolerance to SeV infection can be induced in mice after administration of immunodominant CD4 peptide eptiopes, but that a reduction in T-cells does not alter the levels of SeV-neutralising antibodies, or allow for repeat administration of the virus.…”

“…This is supported by our data. After a second dose of DF/SeV, expression is significantly reduced by 60 and 490% in mice 7 and sheep, respectively. However, because of the original extremely high gene transfer efficiency the residual gene expression after the second dose is still significantly higher than untransfected controls, or a single dose of non-viral vector.…”

“…with short-term intervals to mouse lung are similar to non-viral gene transfer We have previously shown that SeV-mediated transfection on second administration, although reduced by 60% when compared with levels achieved after a single dose, 7 is still high because of the efficient transfection achieved by SeV vector in murine airways. Here, we assessed whether these residual levels are maintained on subsequent dosing.…”

“…5,6 We have previously shown that SeV-mediated gene expression is reduced by 60% on second dose, and that tolerization of mice against immune-dominant SeV epitopes does not improve efficacy. 7 However, given the extremely high transfection efficiency of SeV, the levels of gene expression achieved after repeat administration may still be of sufficient therapeutic value, if retained on subsequent administrations. Here, we assessed SeV-mediated transfection efficiency after three doses of the virus and compared residual levels of gene expression with that achieved using plasmid DNA complexed to the cationic lipid GL67A, currently being used in a clinical trial by the UK CF Gene Therapy Consortium (http://www.cfgenetherapy.org.uk/).…”

Pushing the envelope in the lung

“…2,3,4 Another study has demonstrated that a second successive dose of an SeV vector was able to transduce the murine airways, at B60% of the efficiency seen in naïve animals. 5 Although these earlier studies represented a significant advance in broadening the armamentarium of recombinant vectors suitable for transducing the murine airway, it was unclear whether vectors based on this murine virus would be capable of transducing larger animals. The latter would be seen as a necessary step toward clinical use, both to fulfill regulatory requirements and as a test of the ability of the vector system to work across various species, including humans, in vivo.…”