Genetic Immunization with Lung-Targeting Macroaggregated Polyethyleneimine-Albumin Conjugates Elicits Combined Systemic and Mucosal Immune Responses

Abstract

Genetic immunization is a novel form of vaccination in which transgenes are delivered into the host to produce the foreign protein within host cells. Although systemic immune responses have been relatively easy to induce by genetic immunization, the induction of regional and mucosal immunity has often been more challenging. To address the problem of eliciting mucosal immunity in the lung, we utilized macroaggregated albumin to target plasmid DNA to the lung. Macroaggregated albumin is trapped in the lung after i.v. injection, and it is routinely used in radiolabeled form as an imaging modality to evaluate pulmonary blood flow. To couple DNA to this targeting agent, polyethyleneimine (a polycation that binds DNA and enhances transfection) was conjugated to serum albumin, and the conjugate was aggregated by heating to produce particles of 25–100 μm. The resulting particles bound plasmid DNA avidly, and when injected i.v. in mice, the particles distributed in the peripheral lung tissue in the alveolar interstitium. Particle-bound luciferase plasmid transfected a variety of cell lines in vitro, and after i.v. injection, gene expression was detected exclusively in the lung. Using human growth hormone as the encoded foreign Ag for immunization, i.v. injection of the particle-bound plasmid elicited both pulmonary mucosal and systemic immune responses, whereas naked DNA injected either i.v. or i.m. elicited only systemic responses. Thus, particle-bound plasmid DNA may have utility for genetic immunization by intravascular delivery to the lung and potentially to other organs and tissues.

Gene delivery to the lung using protein/polyethylenimine/plasmid complexes

“…However, its use in vivo has been limited to some extent by a requirement for large amounts of DNA and PEI, and by the need to inject the PEI/DNA complexes in a large volume very quickly. 14 As a result of our previous studies with conjugated albumin-PEI particles with low doses of plasmid, 15 we investigated whether soluble protein by itself could enhance gene delivery by PEI, so that it could be administered under conditions that would be realistic for therapeutic applications.…”

“…MSA was used in these experiments because we wanted to avoid any influence of anti-HSA antibodies that might be expected to develop with repeated injections over 3 weeks. 15 After a single injection, luciferase expression was maximal from 24 to 48 h, but declined markedly after 72 h (Figure 9a). Nonetheless, luciferase activity was still present at 7 days after injection (about 1% of maximal levels), indicating continued low level gene expression, because maximal levels declined to roughly stable levels by 4 days in most experiments.…”

Induction of gp120-specific protective immune responses by genetic vaccination with linear polyethylenimine–plasmid complex

“…PEI22-DNA complexes can repeatedly be administered to animals without eliciting an immune response against the polymer, although the development of an immune response against the exogenously expressed protein has been reported to reduce the level of protein expression [28]. In fact, administration of lungtargeted macroaggregated polyethylenimine-albumin conjugates expressing human growth hormone (HGH) has been shown to elicit a humoral immune response against the HGH [29].…”

Generation of Genome-Wide CD8 T Cell Responses in HLA-A*0201 Transgenic Mice by an HIV-1 Ubiquitin Expression Library Immunization Vaccine

“…Gene gun delivery was selected for this study, because this method generates more efficient library-mediated immune responses in mice for screening efforts (28). Work is underway to compare the level of multivalent HLA-restricted CD8 responses in mice generated by the HIV-1 library vaccine delivery by gene gun, naked DNA injection, and mucosal-targeting approaches (39). Because naked DNA injection of full-length HIV and SIV genes has proven more effective in non-human primates (40), work is also underway to determine which method of genetic immunization is most effective for the proteasome-targeting, fragmented format of the HIV-1 library vaccine in macaques.…”