Generation of MHC class I‐restricted cytotoxic T lymphocytes by expression of a viral protein in muscle cells: antigen presentation by non‐muscle cells

Abstract

Expression of reporter genes in muscle cells has been achieved by intramuscular (i.m.) injection of plasmid DNA expression vectors. We previously demonstrated that this technique is an effective means of immunization to elicit both antibodies capable of conferring homologous protection and cell‐mediated immunity leading to cross‐strain protection against influenza virus challenge in mice. These results suggested that expression of viral proteins by muscle cells can result in the generation of cellular immune responses, including cytotoxic T lymphocytes (CTL). However, because DNA has the potential to be internalized and expressed by other cell types, we sought to determine whether or not induction of CTL required synthesis of antigen in non‐muscle cells and, if not, whether transfer of antigen to antigen‐presenting cells from muscle cells may be involved. In the present study, we demonstrate that transplantation of nucleoprotein (NP)‐transfected myoblasts into syngeneic mice led to the generation of NP‐specific antibodies and CTL, and cross‐strain protective immunity against a lethal challenge with influenza virus. Furthermore, transplantation of NP‐expressing myoblasts (H‐2k) intraperitoneally into F1 hybrid mice (H‐2d × H‐2k) elicited NP CTL restricted by the MHC haplotype of both parental strains. These results indicate that NP expression by muscle cells after transplantation was sufficient to generate protective cell‐mediated immunity, and that induction of the CTL response was mediated, at least in part, by transfer of antigen from the transplanted muscle cells to a host cell.

Superiority of the ear pinna over muscle tissue as site for DNA vaccination

“…Such APC did not need to be transfected themselves. [16][17][18] The presence of the foreign antigen ␤-gal in the lymph nodes was a first hint for induction and generation of an immune response. The generation of a specific humoral immune response against the encoded protein after genetic immunization was seen for every site of injection, but the titers were influenced by the injection site.…”

“…Thus, bone marrow-derived nonmuscle cells were shown to be involved in the induction of cytotoxic T lymphocytes (CTL) following intramuscular DNA immunization. [16][17][18] In contrast, the skin and mucous membranes are the physiological sites where most exogenous antigens are normally encountered. The skin-associated lymphoid tissues contain specialized cells such as keratinocytes, macrophages and Langerhans' cells, which are involved in the initiation and further augmentation of immune responses.…”

Secretory heat-shock protein as a dendritic cell-targeting molecule: a new strategy to enhance the potency of genetic vaccines

“…However, only few bone marrow-derived antigen-presenting cells (APCs), 3,4 especially dendritic cells (DCs) that perform a critical step in the induction of primary immune responses, are directly transfected by injected DNA, 5,6 leading to deficient presentation of peptides from endogenously synthesized antigens on major histocompatibility complex (MHC) molecules. Studies of stably transfected myoblasts, [7][8][9] reconstitution of SCID mice with allogeneic bone marrow-derived APCs after DNA vaccination, 4 and surgical ablation of the injection site, 10 as well as skin excision/grafting experiments 11 also indicate a role for transfected myocytes and keratinocytes in DNA-initiated immune responses. However, these studies demonstrate that acquisition of antigens released from transfected myocytes or keratinocytes and cross-presentation by DCs are essential to induce T-cell responses for any DNA vaccination strategy.…”

Designing gene therapy vectors: avoiding immune responses by using tissue-specific promoters

“…However, it was subsequently shown that only professional antigen-presenting cells (APC) could actually prime immune responses with DNA vaccines. [7][8][9][10] While direct transfection of APC is not absolutely essential, 11 it is probable that some APC are transfected and antigen expression in these APC primes MHC class I and II responses. This may account for the strong immune responses induced by DNA vaccines, especially considering the extremely small quantities of antigen expressed from typical doses of plasmid DNA.…”