RNA interference-mediated prevention and therapy for hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death and is on the increase worldwide. Hepatocellular carcinoma results from chronic liver disease and cirrhosis most commonly associated with chronic hepatitis B (HBV) or hepatitis C (HCV) infection. The highest incidences of HCC are found in China and Africa, where chronic HBV infection is the major risk component. In the United States, Europe and Japan, the significant increase in HCC and HCC-related deaths within the last three decades is mainly attributed to the rise in the number of HCV-infected individuals; smaller increases of HCC are associated with HBV. Given that HCV and HBV infection account for the majority of HCCs, therapeutic and prophylactic approaches to control or eliminate virus infection may prove effective in reducing the occurrence of HCC. Although anti-viral therapies exist for both HBV and HCV infections, they are ineffective for a significant number of patients. In addition, some treatments such as interferon therapy are dose limiting owing to toxic side effects. Clearly, new approaches are needed. RNA interference (RNAi)-based approaches may meet this need and have already shown promising preclinical results in cell culture and animal models. Although this paper focuses on the potential of RNAi as a prophylactic for HCC development, the potential use of RNAi-mediated approaches for HCC therapy will also be discussed.

DNA vaccines encoding interleukin-8 and RANTES enhance antigen-specific Th1-type CD4(+) T-cell-mediated protective immunity against herpes simplex virus type 2 in vivo.

Chemokines are inflammatory molecules that act primarily as chemoattractants and as activators of leukocytes. Their role in antigen-specific immune responses is of importance, but their role in disease protection is unknown. Recently it has been suggested that chemokines modulate immunity along more classical Th1 and Th2 phenotypes. However, no data currently exist in an infectious challenge model system. We analyzed the modulatory effects of selected chemokines (interleukin-8 [IL-8], gamma interferon-inducible protein 10 [IP-10], RANTES, monocyte chemotactic protein 1 [MCP-1], and macrophage inflammatory protein 1 alpha [MIP-1 alpha]) on immune phenotype and protection against lethal challenge with herpes simplex virus type 2 (HSV-2). We observed that coinjection with IL-8 and RANTES plasmid DNAs dramatically enhanced antigen-specific Th1 type cellular immune responses and protection from lethal HSV-2 challenge. This enhanced protection appears to be mediated by CD4(+) T cells, as determined by in vitro and in vivo T-cell subset deletion. Thus, IL-8 and RANTES cDNAs used as DNA vaccine adjuvants drive antigen-specific Th1 type CD4(+) T-cell responses, which result in reduced HSV-2-derived morbidity, as well as reduced mortality. However, coinjection with DNAs expressing MCP-1, IP-10, and MIP-1 alpha increased mortality in the challenged mice. Chemokine DNA coinjection also modulated its own production as well as the production of cytokines. These studies demonstrate that chemokines can dominate and drive immune responses with defined phenotypes, playing an important role in the generation of protective antigen-specific immunity.

Herpes simplex virus DNA vaccine efficacy: effect of glycoprotein D plasmid constructs.

The impact of vaccination with plasmid DNA encoding full-length glycoprotein D (gD) from herpes simplex virus (HSV) type 2 (gD2), secreted gD2, or cytosolic gD2 was evaluated in mice and guinea pigs. Immunization with plasmids encoding full-length gD2 or secreted gD2 produced high antibody levels, whereas immunization with DNA encoding cytosolic gD2 resulted in significantly lower antibody titers in both species (P<.001). Vaccination with DNA encoding full-length or secreted gD2 significantly reduced acute disease in mice and guinea pigs (both P<.001) and subsequent recurrent disease in guinea pigs (P<.05). In guinea pigs, immunization with DNA encoding cytosolic gD2 did not protect from acute or recurrent disease, whereas in mice it did protect, but not as well as DNA encoding full-length or secreted gD2. None of the vaccines resulted in improved virus clearance from the inoculation site, and none significantly reduced recurrent disease when used as a therapeutic vaccine in HSV-2-infected guinea pigs.

Plasmid DNA-expressed secreted and nonsecreted forms of herpes simplex virus glycoprotein D2 induce different types of immune responses.

Herpes simplex viruses (HSVs) are significant pathogens and major targets of vaccine development. Several attempts have been made to develop prophylactic and therapeutic vaccines for HSV types 1 and 2. Although these vaccines elicit strong humoral responses, the overall impact on pathology has been disappointing. An effective vaccine for HSV must induce both humoral and cellular immune responses. DNA vaccines are ideal candidates for HSV vaccines because they induce both types of immune responses. This study showed that the type of immune response generated by immunization with DNA vaccines is modulated by expression of various forms of an antigen, each with a different cellular localization. Expression of cell-associated forms of HSV-2 glycoprotein D (gD) induces primarily a Th1 response, whereas expression of secreted gD results in a Th2 response. Immunization with plasmids expressing different forms of the antigen may increase the efficacy of a vaccine.

Characterization of a new class of DNA delivery complexes formed by the local anesthetic bupivacaine.

Bupivacaine, a local anesthetic and cationic amphiphile, forms stable liposomal-like structures upon direct mixing with plasmid DNA in aqueous solutions. These structures are on the order of 50-70 nm as determined by scanning electron microscopy, and are homogeneous populations as analyzed by density gradient centrifugation. The DNA within these structures is protected from nuclease degradation and UV-induced damage in vitro. Bupivacaine:DNA complexes have a negative zeta potential (surface charge), homogeneous nature, and an ability to rapidly assemble in aqueous solutions. Bupivacaine:DNA complexes, as well as similar complexes of DNA with other local anesthetics, have the potential to be a novel class of DNA delivery agents for gene therapy and DNA vaccines.

Interleukin 7 can enhance antigen-specific cytotoxic-T-lymphocyte and/or Th2-type immune responses in vivo.

Interleukin 7 (IL-7) protein has been reported to be important in the development of cytotoxic-T-lymphocyte (CTL) responses. However, other studies also support a partial Th2 phenotype for this cytokine. In an effort to clarify this unusual conflict, we compared IL-7 along with IL-12 (Th1 control) and IL-10 (Th2 control) for its ability to induce antigen (Ag)-specific CTL and Th1- versus Th2-type immune responses using a well established DNA vaccine model. In particular, IL-7 codelivery showed a significant increase in immunoglobulin G1 (IgG1) levels compared to IgG2a levels. IL-7 coinjection also decreased production of Th1-type cytokine IL-2, gamma interferon, and the chemokine RANTES but increased production of the Th2-type cytokine IL-10 and the similarly biased chemokine MCP-1. In herpes simplex virus (HSV) challenge studies, IL-7 coinjection decreased the survival rate after lethal HSV type 2 (HSV-2) challenge compared with gD plasmid vaccine alone in a manner similar to IL-10 coinjection, whereas IL-12 coinjection enhanced the protection, further supporting that IL-7 drives immune responses to the Th2 type, resulting in reduced protection against HSV-2 challenge. Moreover, coinjection with human immunodeficiency virus type 1 env and gag/pol genes plus IL-12 or IL-7 cDNA enhanced Ag-specific CTLs, while coinjection with IL-10 cDNA failed to influence CTL induction. Thus, IL-7 could drive Ag-specific Th2-type cellular responses and/or CTL responses. These results support that CTLs could be induced by IL-7 in a Th2-type cytokine and chemokine environment in vivo. This property of IL-7 allows for an alternative pathway for CTL development which has important implications for host-pathogen responses.

LFA-3 plasmid DNA enhances Ag-specific humoral- and cellular-mediated protective immunity against herpes simplex virus-2 in vivo: involvement of CD4+ T cells in protection.

Adhesion molecules are important for cell trafficking and delivery of secondary signals for stimulation of T cells and antigen-presenting cells (APCs) in a variety of immune and inflammatory responses. Adhesion molecules lymphocyte function-associated antigen (LFA)-1 and CD2 on T cells recognize intercellular adhesion molecule (ICAM)-1 and LFA-3 on APCs, respectively. Recent studies have suggested that these molecules might play a regulatory role in antigen-specific immune responses. To investigate specific roles of adhesion molecules in immune induction we coimmunized LFA-3 and ICAM-1 cDNAs with a gD plasmid vaccine and then analyzed immune modulatory effects and protection against lethal herpes simplex virus (HSV)-2 challenge. We observed that gD-specific IgG production was enhanced by LFA-3 coinjection. However, little change in IgG production was observed by ICAM-1 coinjection. Furthermore, both Th1 and Th2 IgG isotype production was driven by LFA-3. LFA-3 also enhanced Th cell proliferative responses and production of interleukin (IL)-2, interferon-gamma, IL-4, and IL-10 from splenocytes. In contrast, ICAM-1 showed slightly increasing effects on T-cell proliferation responses and cytokine production. beta-Chemokine production (RANTES, MIP-1alpha, and MCP-1) was also influenced by LFA-3 or ICAM-1. When animals were challenged with a lethal dose of HSV-2, LFA-3-coimmunized animals exhibited an enhanced survival rate, as compared to animals given ICAM-1 or gD DNA vaccine alone. This enhanced protection appears to be mediated by CD4+ T cells, as determined by in vitro and in vivo T-cell subset deletion. These studies demonstrate that adhesion molecule LFA-3 can play an important role in generating protective antigen-specific immunity in the HSV model system through increased induction of CD4+ Th1 T-cell subset.

Chain reaction cloning: a one-step method for directional ligation of multiple DNA fragments.

A novel DNA assembly method, chain reaction cloning (CRC), is described. CRC enables the ordered assembly of multiple DNA fragments in a single step. The power of the technique was demonstrated by the directed in vitro assembly of a plasmid comprised of six DNA fragments from a pool of 12 available fragments. The odds of obtaining the correct plasmid clone in a single step, using conventional techniques, is less than 1 in 191000000. Using CRC, the desired plasmid was recovered at a frequency of one in two. Ligation is no longer the rate limiting step in cloning, and limitless possibilities exist for the reconstruction of complex genomes.

DNA vaccines--challenges in delivery.

DNA vaccines are typically comprised of plasmid DNA molecules that encode an antigen(s) derived from a pathogen or tumor cell. Following introduction into a vaccine, cells take up the DNA, where expression and immune presentation of the encoded antigen(s) takes place. DNA can be introduced by viral or bacterial vectors or through uptake of 'naked' or complexed DNA. Vaccination with DNA is a recent technology possessing distinct advantages over traditional vaccines (killed or attenuated pathogens) and the more recently developed subunit vaccines. Unlike most subunit vaccines, DNA vaccines induce both the humoral and cellular arms of the immune response. The stimulation of both arms of the immune system is important not only for the prevention of many diseases including AIDS, but also allows the use of a vaccine for therapeutic purposes. While the traditional attenuated pathogen vaccines are also able to elicit both cellular and humoral immune responses, there is a risk of reversion from the attenuated state to the virulent state. This risk does not exist with DNA vaccines. DNA vaccines can be manufactured and formulated by generic processes. DNA vaccine technology, however, is still in its infancy and much research needs to be done to improve the efficiency with which these vaccines work in humans. While continued efforts toward improving both DNA expression and DNA delivery are equally important for increasing the utility of DNA vaccines, this review will focus both on non-viral delivery of plasmid DNA and delivery methods for the encoded antigen.

Genetic vaccination targeting T-cell receptors.

T-cell antigen receptor (TCR) genes (which consist of variable (V), diversity (D), joining (J) and constant (C) segments) undergo rearrangement during T-cell development and result in the expression of a disulfide linked heterodimer (α and ß chains) on the surface of mature T-cells (1,2). The TCR confers specificity to each T-cell for antigen recognition (in the context of major histocompatibility (MHC) molecules (1,3). Clonal TCR-ß chain gene rearrangements have been demonstrated in DNA samples derived from cutaneous tumors, peripheral blood lymphocytes and lymph nodes of patients with cutaneous T cell lymphomas (CTCL) (4-6). Together with immunohistologic data (7), these findings indicate that CTCL is a clonal disease of malignant T cells that express α/ß-TCR.

Preclinical safety of DNA vaccines : a method to analyze the distribution of plasmid DNA in animal models.

DNA or genetic vaccines are currently being evaluated for safety and efficacy in human clinical trials in the areas of infectious disease and cancer. Since DNA vaccines induce antibodies and cytotoxic T lymphocytes (CTLs), they are currently being evaluated in humans for both prevention and therapy of HSV-2, HIV-1, and HBV infections, for prevention of influenza and malaria, and therapy of cutaneous T-cell lymphoma (CTCL) and colorectal cancer.

Induction of HSV-gD2 specific CD4(+) cells in Peyer's patches and mucosal antibody responses in mice following DNA immunization by both parenteral and mucosal administration.

A DNA vaccine encoding glycoprotein D (gD) of herpes simplex virus type 2 (pHSV-gD2) was injected via parenteral and mucosal routes to determine the optimal route of delivery for immune stimulation. Generation of distal mucosal immunity following parenteral vaccination was also evaluated. While all routes of DNA vaccine administration resulted in systemic cellular and humoral responses, the intra-muscular (i.m.) and intra-dermal (i.d.) routes of delivery produced the highest responses. Furthermore, i.m. and i.d. routes produced mucosal humoral responses that were comparable to those obtained via mucosal routes. Specific pHSV-gD2 PCR signals were detected in the Peyer's patches (PP) within hours following vaccination and antigen specific IgA was detected in secretions and supernatants from gut fragment cultures. Furthermore, antigen specific CD4(+) cells were found in PP. Collectively these results suggest that the DNA vaccine stimulated a response in the PP, a major inductive site for mucosal responses.

DNA priming-protein boosting enhances both antigen-specific antibody and Th1-type cellular immune responses in a murine herpes simplex virus-2 gD vaccine model.

It has previously been reported that herpes simplex virus (HSV)-2 gD DNA vaccine preferentially induces T-helper (Th) 1-type cellular immune responses, whereas the literature supports the view that subunit vaccines tend to induce potent antibody responses, supporting a Th2 bias. Here, using an HSV gD vaccine model, we investigated whether priming and boosting with a DNA or protein vaccine could induce both potent antibody and Th1-type cellular immune responses. When animals were primed with DNA and boosted with protein, both antibody and Th-cell proliferative responses were significantly enhanced. Furthermore, production of Th1-type cytokines (interleukin-2, interferon-gamma) was enhanced by DNA priming-protein boosting. In contrast, protein priming-DNA boosting produced antibody levels similar to those following protein-protein vaccination but failed to further enhance Th-cell proliferative responses or cytokine production. DNA priming-protein boosting resulted in an increased IgG2a isotype (a Th1 indicator) profile, similar to that induced by DNA-DNA vaccination, whereas protein priming-DNA boosting caused an increased IgG1 isotype (a Th2 indicator) profile similar to that seen after protein-protein vaccination. This result indicates that preferential induction of IgG1 or IgG2a isotype is determined by the type of priming vaccine used. Thus, this study suggests that HSV DNA priming-protein boosting could elicit both potent Th1-type cellular immune responses and antibody responses, both of which likely are important for protection against HSV infection.

IL-12 gene as a DNA vaccine adjuvant in a herpes mouse model: IL-12 enhances Th1-type CD4+ T cell-mediated protective immunity against herpes simplex virus-2 challenge.

IL-12 has been shown to enhance cellular immunity in vitro and in vivo. Recent reports have suggested that combining DNA vaccine approach with immune stimulatory molecules delivered as genes may significantly enhance Ag-specific immune responses in vivo. In particular, IL-12 molecules could constitute an important addition to a herpes vaccine by amplifying specific immune responses. Here we investigate the utility of IL-12 cDNA as an adjuvant for a herpes simplex virus-2 (HSV-2) DNA vaccine in a mouse challenge model. Direct i.m. injection of IL-12 cDNA induced activation of resting immune cells in vivo. Furthermore, coinjection with IL-12 cDNA and gD DNA vaccine inhibited both systemic gD-specific Ab and local Ab levels compared with gD plasmid vaccination alone. In contrast, Th cell proliferative responses and secretion of cytokines (IL-2 and IFN-gamma) and chemokines (RANTES and macrophage inflammatory protein-1alpha) were significantly increased by IL-12 coinjection. However, the production of cytokines (IL-4 and IL-10) and chemokine (MCP-1) was inhibited by IL-12 coinjection. IL-12 coinjection with a gD DNA vaccine showed significantly better protection from lethal HSV-2 challenge compared with gD DNA vaccination alone in both inbred and outbred mice. This enhanced protection appears to be mediated by CD4+ T cells, as determined by in vivo CD4+ T cell deletion. Thus, IL-12 cDNA as a DNA vaccine adjuvant drives Ag-specific Th1 type CD4+ T cell responses that result in reduced HSV-2-derived morbidity as well as mortality.

Expression and immune response to hepatitis C virus core DNA-based vaccine constructs.

Hepatitis C virus (HCV) is a major worldwide cause of acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The development of vaccines against HCV have been complicated by the high variability of the envelope region, and it is likely that the cellular immune responses to viral structural proteins may be important for eradicating persistent viral infection. Recently, it was reported that the injection into muscle cells of plasmids encoding viral genes resulted in the generation of strong cellular immune responses. We constructed vectors that express the highly conserved HCV core gene. In this regard, the pHCV 2-2 construct contained the entire HCV core region and pHCV 4-2 contained both the 5' noncoding region and the core gene. Cellular expression of HCV core protein was assessed following transfection into human and murine cell lines, and higher intracellular levels of the 21-kd core protein were observed with pHCV 2-2. These HCV core DNA constructs were used to immunize BALB/c mice and produced low-level anti-HCV core humoral immune responses. To assess cytotoxic T-lymphocyte (CTL) activity generated in vivo, a cloned syngeneic SP2/O myeloma cell line constitutively expressing HCV core protein was established and inoculated into BALB/c mice to produce growth of plasmacytomas. Strong CTL activity was generated because the tumor size and weight in pHCV 2-2-immunized mice were remarkably reduced compared with mice injected with mock DNA. Spontaneous CTL activity was also exhibited by splenocytes in an in vitro cytotoxicity assay. These investigations demonstrate that plasmid constructs expressing HCV core protein generate strong CTL activity, as assessed both in vivo and in vitro, and are promising candidates as antiviral agents.

Facilitated DNA inoculation induces anti-HIV-1 immunity in vivo.

Vaccine design against HIV-1 is complicated both by the latent aspects of lentiviral infection and the diversity of the virus. The type of vaccine approach used is therefore likely to be critically important. In general, vaccination strategies have relied on the use of live attenuated material or inactivated/subunit preparations as specific immunogens. Each of these methodologies has advantages and disadvantages in terms of the elicitation of broad cellular and humoral immune responses. Although most success has been achieved with live attenuated vaccines, there is a conceptual safety concern associated with the use of these vaccines for the prevention of human infections. In contrast, subunit or killed vaccine preparations enjoy advantages in preparation and conceptual safety; however, their ability to elicit broad immunity is more limited. In theory, inoculation of a plasmid DNA that supports in vivo expression of proteins, and therefore presentation of the processed protein antigen to the immune system, could be used to combine the features of a subunit vaccine and a live attenuated vaccine. We have designed a strategy for intramuscular DNA inoculation to elicit humoral and cellular immune responses against expressed HIV antigens. Uptake and expression are significantly enhanced if DNA is administered in conjunction with the facilitating agent bupivacaine-HCl. Using this technique we have demonstrated functional cellular and humoral immune responses against the majority of HIV-1 encoded antigens in both rodents and non-human primates.

Selective cleavage of bcr-abl chimeric RNAs by a ribozyme targeted to non-contiguous sequences.

Conventionally designed ribozymes may be unable to cleave RNA at sites which are inaccessible due to secondary structure. In addition, it may also be difficult to specifically target a conventionally designed ribozyme to some chimeric RNA molecules. Novel approaches for ribozyme targeting were developed by using the L6 bcr-abl fusion RNA as a model. Using one approach, we successfully directed ribozyme nucleation to a site on the bcr-abl RNA that is distant from the GUA cleavage site. These ribozymes bound to the L6 substrate RNA via an anchor sequence that was complementary to bcr sequences. The anchor was necessary for efficient cleavage as the anchor minus ribozyme, a conventionally designed ribozyme, was inefficient at catalyzing cleavage at this same site. The effect of anchor sequences on catalytic rates was determined for two of these ribozymes. Ribozymes generated by a second approach were designed to cleave at a CUU site in proximity to the bcr-abl junction. Both approaches have led to the development of a series of ribozymes specific for both the L6 and K28 bcr-abl chimeric RNAs, but not normal abl or bcr RNAs. The specificity of the ribozyme correlated in part with the ability of the ribozyme to bind substrate as demonstrated by gel shift analyses. Secondary structure predictions for the RNA substrate support the experimental results and may prove useful as a theoretical basis for the design of ribozymes.

Identification of polypeptides encoded in open reading frame 1b of the putative polymerase gene of the murine coronavirus mouse hepatitis virus A59.

The polypeptides encoded in open reading frame (ORF) 1b of the mouse hepatitis virus A59 putative polymerase gene of RNA 1 were identified in the products of in vitro translation of genome RNA. Two antisera directed against fusion proteins containing sequences encoded in portions of the 3'-terminal 2.0 kb of ORF 1b were used to immunoprecipitate p90, p74, p53, p44, and p32 polypeptides. These polypeptides were clearly different in electrophoretic mobility, antiserum reactivity, and partial protease digestion pattern from viral structural proteins and from polypeptides encoded in the 5' end of ORF 1a, previously identified by in vitro translation. The largest of these polypeptides had partial protease digestion patterns similar to those of polypeptides generated by in vitro translation of a synthetic mRNA derived from the 3' end of ORF 1b. The polypeptides encoded in ORF 1b accumulated more slowly during in vitro translation than polypeptides encoded in ORF 1a. This is consistent with the hypothesis that translation of gene A initiates at the 5' end of ORF 1a and that translation of ORF 1b occurs following a frameshift at the ORF 1a-ORF 1b junction. The use of in vitro translation of genome RNA and immunoprecipitation with antisera directed against various regions of the polypeptides encoded in gene A should make it possible to study synthesis and processing of the putative coronavirus polymerase.

The primary structure and expression of the second open reading frame of the polymerase gene of the coronavirus MHV-A59; a highly conserved polymerase is expressed by an efficient ribosomal frameshifting mechanism.

Sequence analysis of a substantial part of the polymerase gene of the murine coronavirus MHV-A59 revealed the 3' end of an open reading frame (ORF1a) overlapping with a large ORF (ORF1b; 2733 amino acids) which covers the 3' half of the polymerase gene. The expression of ORF1b occurs by a ribosomal frameshifting mechanism since the ORF1a/ORF1b overlapping nucleotide sequence is capable of inducing ribosomal frameshifting in vitro as well as in vivo. A stem-loop structure and a pseudoknot are predicted in the nucleotide sequence involved in ribosomal frameshifting. Comparison of the predicted amino acid sequence of MHV ORF1b with the amino acid sequence deduced from the corresponding gene of the avian coronavirus IBV demonstrated that in contrast to the other viral genes this ORF is extremely conserved. Detailed analysis of the predicted amino acid sequence revealed sequence elements which are conserved in many DNA and RNA polymerases.