Xenogeneic and allogeneic anti-MHC immune responses induced by plasmid DNA immunization

A Histological Comparison of Two Human Acellular Dermal Matrix Products in Prosthetic-Based Breast Reconstruction

Background

Acellular dermal matrices (ADMs) are an integral component of breast reconstruction. The ideal matrix would be relatively immuno-inert, allow rapid vascularization, and be affordable. The purpose of this study was to histologically compare 2 commonly used ADM products.

Methods

This is a prospective histological study of 17 patients (20 breasts) following prosthetic-based breast reconstruction with ADM: Alloderm (LifeCell Corp, Branchburg, N.J.) or Cortiva (RTI Surgical, Alachua Fla.). Biopsies were taken from the dermal matrix and natural capsules surrounding the expander/implant during secondary surgery [Range, 72-694 days (mean, 217 days)]. Biopsy specimens were prepared via hematoxylin and eosin, Masson's trichrome, elastin, and transforming growth factor (TGF)-1 stains. Quantitative analysis of staining was performed with ImageJ software. The clinical outcome of each patient is analyzed in relation to capsule architecture and ADM performance.

Results

There were 7 breasts in the Alloderm group and 13 in the Cortiva group. Both groups had similar demographic, aesthetic results, and complication profiles. The TGF-1 staining demonstrated significantly lower levels in the Cortiva capsules (P = 0.0139). The percentage of elastin and collagen are similar in the Cortiva, Alloderm, and natural peri-implant capsules. The native capsules show a significantly greater number of blood vessels when compared with Cortiva and Alloderm (P = 0.0371 and P = 0.0347, respectively); however, there is no difference in vascular pattern between the 2 dermal matrices.

Discussion

Postoperatively, Cortiva demonstrates equal vascularity with less TGF-1 activation compared with Alloderm. The clinical success and complication profile were similar between the Alloderm and Cortiva patients.

Naked DNA immunization as an approach to target the generic tumor antigen survivin induces humoral and cellular immune responses in mice

Survivin, a 16.5 kDa tumor associated antigen, is the smallest member of the inhibitor of apoptosis family that is abundantly expressed during development but essentially absent in normal adult tissues. Interestingly, survivin expression is up-regulated in virtually all types of cancers studied, as well as in vascular endothelial cells during tumor associated angiogenesis. Survivin links apoptosis to cell cycle progression and plays a pivotal role in regulation of cell proliferation. These characteristics make survivin a potentially promising generic target for cancer immunotherapy. Hence, a genetic immunization strategy to induce tumor-specific immune responses against human survivin in a pre-clinical animal model was developed. In initial studies, BALB/c mice were immunized by intramuscular injection with DNA coding for human survivin (pcDNA3.1/hSurv). In addition, a construct encoding a secreted version of survivin (pSecTag2B/hSurv) was designed. A plasmid coding for murine granulocyte-macrophage colony-stimulating factor (GM-CSF) was co-injected in both cases as a molecular adjuvant. Expression of survivin following transfection in mouse cells was corroborated. Humoral responses against human survivin were detected in mice sera using two immunization protocols (injections at 2- or 3-week intervals). The humoral response was markedly improved by secretion of survivin and co-expression of GM-CSF. The predominant antibody subclass detected in responsive mice was IgG2a, suggesting that a Th1-CD4+ cellular response had been induced. Furthermore, DNA immunization with survivin encoding vectors generated an effective CD8+ T cell response measured as an increase of cytotoxic Interferon-gamma (IFN-gamma) secreting CD8+ T cells. In conclusion, intramuscular genetic immunization of mice with human survivin encoding plasmids induced a survivin-specific humoral as well as cellular immune response in recipient mice. Secretion of survivin and co-injection of GM-CSF as a genetic adjuvant appear to be more important in generating an humoral than a cellular immune response.

Breakdown of CTL Tolerance to Self HLA-B*2705 Induced by Exposure toChlamydiatrachomatis

There is a strong association between seronegative arthritis and HLA B27, but it is still unresolved whether the contribution of B27 to disease pathogenesis is solely as a restriction element for an arthritogenic peptide, or whether B27 itself serves as an autoantigen. This study uses transgenic rats to address the question as to whether exposure to an arthritogenic pathogen can alter tolerance to B27. Unlike their nontransgenic counterparts, B27-transgenic rats are tolerant of B27 immunization using either B27(+) splenocytes or plasmid DNA and do not develop anti-B27 CTL. However, if splenocytes from such immunized animals are exposed to Chlamydia in vitro, CTL are generated that lyse B27(+) targets. No killing was seen with targets transfected with control B7, B14, B40, or B44. This phenomenon was not observed with immunization by nontransgenic splenocytes, or HLA-A2 DNA alone. Using targets expressing mutated B27, we show that the epitope for autoreactive CTL recognition of B27 involves the Lys(70) amino acid residue in the alpha(1) domain of the MHC class I molecule. The generation of CTL with specificity for B27 under these conditions demonstrates that tolerance to B27 can be subverted by CHLAMYDIA: This indicates a dynamic interrelationship between the pathogen and B27, which may have important implications for B27-related spondyloarthropathies triggered by intracellular bacteria.

The effect of an anti-HLA-B27 immune response on CTL recognition of Chlamydia

The interplay between triggering bacteria and HLA-B27 in the pathogenesis of the spondyloarthropathies remains one of the most active areas of investigation in the rheumatic diseases. This has proved difficult to study systematically in the clinical setting, and in this study we utilized a rat model to address the influence that B27-related immunity may have on the process of generating anti-Chlamydia immunity. When splenocytes from HLA-B27 DNA-immunized Lewis (LEW) animals received restimulation in vitro with Chlamydia-treated cells from B27-transgenic LEW rats, we observed that in addition to the expected CTL recognition of HLA-B27, there was also anti-Chlamydia CTL killing of Chlamydia-sensitized syngeneic fibroblast targets. This was not seen when responding cells in vitro were naive LEW splenocytes. To confirm the existence of CTLs recognizing both HLA-B27 and Chlamydia, LEW rats were immunized with B27-transgenic LEW cells, instead of the B27 DNA construct. Splenocytes from the immune rats were restimulated in vitro with Chlamydia-treated B27-transgenic LEW cells. In this instance, the CTLs retained the allele-specific recognition of HLA-B27, as well as recognition of Chlamydia-sensitized syngeneic fibroblasts. Thus, if there is prior expansion of an immune response against HLA-B27, then the resulting splenocytes demonstrate a reduced threshold for generating a primary anti-Chlamydia CTL response. These studies implicate a dynamic interrelationship between recognition of HLA-B27 and Chlamydia trachomatis. The results may have implications for deciphering the cellular basis of Chlamydia-induced reactive arthritis.

Creating HIV-1 reverse transcriptase cytotoxic T lymphocyte target structures by HLA-A2 heavy chain modifications

Vigorous HIV-1-specific CD8(+) cytotoxic T lymphocyte (CTL) responses play an important role in the control of HIV-1 replication and the induction of a strong, broadly cross-reactive CTL response remains an important goal of HIV vaccine development. It is known that the display of high levels of class I MHC-viral peptide complexes at the cell surface of target cells is necessary to elicit a strong CTL response. We now report two strategies to enhance the presentation of defined HIV-1 epitope-specific CTL target structures, by incorporating subdominant HIV-1 reverse transcriptase (RT) CTL epitope sequences into the human class I MHC molecule HLA-A2. We show that either incorporation of HIV-1 CTL epitopes into the signal sequence of HLA or tethering of epitopes to the HLA-A2 heavy chain provide simple ways to create effective CTL target structures that can be recognized and lysed by human HLA-A2-restricted RT-specific CD8(+) CTL. Moreover, cells expressing these epitope-containing HLA-A2 constructs stimulated the generation of primary epitope-specific CTL in vitro. These strategies offer new options in the design of plasmid DNA-based vaccines or immunotherapeutics for the induction of CTL responses against subdominant HIV-1 epitopes.

Anti-major histocompatibility complex antibody responses in macaques via intradermal DNA immunizations

In simian immunodeficiency virus (SIV) models, immunization of macaques with uninfected human cells or human major histocompatibility complex (MHC) proteins can induce xenogeneic immune responses which can protect the animals from subsequent SIV challenges. These studies suggest that the induction of anti-MHC immune responses can be a viable vaccine strategy against human immunodeficiency virus type 1 (HIV-1). We have previously shown in mouse studies that DNA immunization with class I and class II MHC-encoding plasmids can elicit both xenogeneic and allogeneic antibody responses against conformationally intact MHC molecules (Vaccine 17 (1999) 2479-92). Here we take these observations one step closer to human applications and report that intradermal needle immunizations of non-human primates with plasmid DNA encoding human MHC alleles can safely elicit xenogeneic anti-MHC antibody responses. Moreover, injecting macaques with DNA encoding a specific macaque allogeneic MHC induced anti-allogeneic MHC antibodies production. These studies show that DNA immunization with MHC-encoding vectors can indeed be used to induce specific anti-human xenogeneic, as well as anti-macaque allogeneic MHC immunity in non-human primates. This strategy could thus be used to mobilize anti-MHC antibody response which may be useful as part of an anti-HIV-1 vaccination approach.