Successful DNA immunization against measles: neutralizing antibody against either the hemagglutinin or fusion glycoprotein protects rhesus macaques without evidence of atypical measles.

Measles remains a principal cause of worldwide mortality, in part because young infants cannot be immunized effectively. Development of new vaccines has been hindered by previous experience with a formalin-inactivated vaccine that predisposed to a severe form of disease (atypical measles). Here we have developed and tested potential DNA vaccines for immunogenicity, efficacy and safety in a rhesus macaque model of measles. DNA protected from challenge with wild-type measles virus. Protection correlated with levels of neutralizing antibody and not with cytotoxic T lymphocyte activity. There was no evidence in any group, including those receiving hemagglutinin-encoding DNA alone, of 'priming' for atypical measles.

Neutralizing antibody-independent containment of immunodeficiency virus challenges by DNA priming and recombinant pox virus booster immunizations.

Eight different protocols were compared for their ability to raise protection against immunodeficiency virus challenges in rhesus macaques. The most promising containment of challenge infections was achieved by intradermal DNA priming followed by recombinant fowl pox virus booster immunizations. This containment did not require neutralizing antibody and was active for a series of challenges ending with a highly virulent virus with a primary isolate envelope heterologous to the immunizing strain.

A case of paramyotonia congenita in pregnancy.

Paramyotonia congenita is a rare autosomal dominant non-dystrophic myopathy caused by mutations in the SNC4A gene, which encodes for the voltage-gated sodium channel in skeletal muscle. Symptom onset is typically during early childhood and is characterised by myotonia followed by flaccid paralysis or weakness, usually exacerbated by repeated muscle contractions or cold temperatures. Pregnancy has been reported to increase symptoms of myotonia; however, there is limited information in the literature regarding the possible effects of paramyotonia congenita on pregnancy and labour. We present a successful case of a 20-year-old primigravida with confirmed paramyotonia congenita and review the literature regarding paramyotonia congenita during pregnancy.

Unexpectedly high levels of HIV-1 RNA and protein synthesis in a cytocidal infection.

The expression of a laboratory strain of HIV-1 (HTLV-IIIB) has been studied in mitogen-stimulated peripheral blood lymphocytes (PBLs) and in two lymphoid cell lines (CEM cells and C8166 cells). HIV-expressing cells contained from 300,000 to 2,500,000 copies of viral RNA per cell. Near-synchronous expression of an active infection could be achieved in C8166 cells. In these cells, the high copy numbers of viral RNA used as much as 40% of total protein synthesis for the production of viral gag protein, with high levels of viral RNA and protein synthesis preceding cell death by 2 to 4 days.

Correction: copy numbers of HIV-1 RNA.

In Barbara J. Culliton's article "Gore Tex organoids and organoids and genetic drugs" (News & Comment, 10 Nov., p. 747), it should have been noted that the structural analysis of the implant connections, induding the micrographs shown on page 747, were performed by Christian C. Haudenschild at the Mallory Institute of Pathology, Boston University of Medicine, Boston, MA. His name should have been listed in the photo credit. The legend for the bottom photomicrograph should have read, "Below, a view in cross section confirms the presence of abundant vessels lined with endothelial cells and surrounded by several layers of smooth musclc cells. Two profiles without lumen resemble neural structures, but their precise identity remains to be investigated."

New findings on the congenital transmission of avian leukosis viruses.

RAV-0, an endogenous avian leukosis virus, does not undergo congenital transmission in infected K28 chickens. In contrast, avian leukosis viruses of exogenous origin undergo highly efficient congenital transmission. The relative abilities of endogenous and exogenous viruses to undergo congenital transmission appear to be determined by the p27 capsid proteins of these viruses.

Control of a mucosal challenge and prevention of AIDS by a multiprotein DNA/MVA vaccine.

Heterologous prime/boost regimens have the potential for raising high levels of immune responses. Here we report that DNA priming followed by a recombinant modified vaccinia Ankara (rMVA) booster controlled a highly pathogenic immunodeficiency virus challenge in a rhesus macaque model. Both the DNA and rMVA components of the vaccine expressed multiple immunodeficiency virus proteins. Two DNA inoculations at 0 and 8 weeks and a single rMVA booster at 24 weeks effectively controlled an intrarectal challenge administered 7 months after the booster. These findings provide hope that a relatively simple multiprotein DNA/MVA vaccine can help to control the acquired immune deficiency syndrome epidemic.

Protein tyrosine kinase activities of the epidermal growth factor receptor and ErbB proteins: correlation of oncogenic activation with altered kinetics.

We have compared the protein tyrosine kinase activities of the chicken epidermal growth factor receptor (chEGFR) and three ErbB proteins to learn whether cancer-activating mutations affect the kinetics of kinase activity. In immune complex assays performed in the presence of 15 mM Mn2+, ErbB proteins and the chEGFR exhibited highly reproducible tyrosine kinase activity. Under these conditions, the ErbB and chEGFR proteins had similar apparent Km [Km(app)] values for ATP. The ErbB proteins appeared to be activated, as they had at least 3-fold-higher relative Vmax(app) for autophosphorylation and approximately 2-fold higher relative Vmax(app) for the phosphorylation of the exogenous substrate TK6 (a bacterially expressed fusion protein containing the C-terminal domain of the human EGFR). The ErbB kinases had both higher Km(app) and higher Vmax(app) for the phosphorylation of the exogenous substrate TK6 than did the chEGFR. The ratios of the Vmax(app) to the Km(app) for TK6 phosphorylation suggested that the ErbB proteins had lower catalytic efficiencies for the exogenous substrate than did the chEGFR. The three tested ErbB proteins had cytoplasmic domain mutations that conferred distinctive disease potentials. These mutations did not affect the kinetics for the phosphorylation of the exogenous substrate TK6. Two of the ErbB proteins contained all of the sites used for autophosphorylation. In these, a mutation that broadened oncogenic potential to endothelial cells caused an additional increase in Vmax(app) for autophosphorylation. Thus, mutations that change the EGFR into an ErbB oncogene cause multiple changes in the kinetics of protein tyrosine kinase activity.

Role of methylation in the induced and spontaneous expression of the avian endogenous virus ev-1: DNA structure and gene products.

The endogenous avian provirus ev-1 is widespread in white leghorn chickens. Although it has no major structural defects, ev-1 has not been associated with any phenotype and is ordinarily expressed at a very low level. In this report, we describe a chicken embryo (Number 1836) cell culture containing both ev-1 and ev-6 which spontaneously expressed the ev-1 provirus. This culture released a high level of noninfectious virions containing a full complement of virion structural (gag) proteins but devoid of reverse transcriptase activity or antigen. These virions contained 70S RNA closely related to the genome of Rous-associated virus type 0, but identifiable as the ev-1 genome by oligonucleotide mapping. A fraction of the RNA molecules in the 70S complex were unusual in that they were polyadenylated 100 to 200 nucleotides downstream of the usual polyadenylation site. Eight sibling embryo cultures did not share this unusual phenotype with 1836, indicating that it was not inherited. However, an identical phenotype was inducible in the sibling cultures by treatment with 5-azacytidine, an inhibitor of DNA methylation, and the induced expression was stable for more than 10 generations. Analysis of chromatin structure and DNA methylation of the ev-1 provirus in 1836 cells revealed the presence (in a fraction of the proviruses) of both DNase I hypersensitive sites in the long terminal repeats and in gag and a pattern of cleavage sites for methyl-sensitive restriction endonuclease not found in a nonexpressing sibling. These results lend strong support to the role of DNA methylation in the control of gene expression. Additionally, they explain the lack of phenotype associated with ev-1 as due to a combination of its low expression and defectiveness in pol and env.

Apoptosis-mediated enhancement of DNA-raised immune responses by mutant caspases.

Apoptotic bodies can be used to target delivery of DNA-expressed immunogens into professional antigen-presenting cells (APCs). Here we show that antigen-laden apoptotic bodies created by vectors co-expressing influenza virus hemagglutinin (HA) or nucleoprotein (NP) genes and mutant caspase genes markedly increased T-cell responses. Both CD8 and CD4 T-cell responses were affected. The adjuvant activity was restricted to partially inactivated caspases that allowed immunogen expression before the generation of apoptotic bodies. Active-site mutants of murine caspase 2 and an autocatalytic chimera of murine caspase 2 prodomain and human caspase 3 induced apoptosis that did not interfere with immunogen expression. The adjuvant activity also enhanced B-cell responses, but to a lesser extent than T-cell responses. The large increases in T-cell responses represent one of the strongest effects to date of a DNA adjuvant on cellular immunity.

Excellent safety and tolerability of the human immunodeficiency virus type 1 pGA2/JS2 plasmid DNA priming vector vaccine in HIV type 1 uninfected adults.

A vaccine consisting of DNA priming followed by recombinant modified vaccinia Ankara (rMVA) boosting has achieved long-term control of a pathogenic challenge with a chimera of simian and human immunodeficiency viruses (SHIV-89.6P) in rhesus macaques. Based on these results, clade B HIV-1 DNA and rMVA immunogens have been developed for trials in humans. We conducted a first-time in humans phase I safety trial using the pGA2/JS2 (JS2) HIV-1 DNA priming vector expressing Gag, Pol, Env, Tat, Rev, and Vpu. Thirty HIV-uninfected adults were vaccinated with 0.3 or 3 mg of JS2 DNA, or a saline placebo, by intramuscular injection at months 0 and 2. Both doses of DNA were safe and well-tolerated with no differences between the control, 0.3 mg, or 3 mg groups (n = 6, 12, and 12, respectively) through 12 months of postvaccination follow- up. A chromium-release assay using fresh peripheral blood mononuclear cells (PBMCs) and a validated IFN-gamma ELISpot assay with frozen PBMCs failed to detect CD4(+) or CD8(+) HIV-1-specific T cell responses. HIV-specific neutralizing antibodies were also not detected. The vaccine is being further developed as a priming vector for a combined DNA plus rMVA prime/boost HIV vaccination regimen.

Characterization of an angiosarcoma-inducing mutation in the erbB oncogene.

The erbB oncogenes of two transducing viruses that arose in chicken 5005 have been molecularly characterized. One of these viruses, AEV-5005, caused erythroblastosis. The other, AAV-5005, caused angiosarcoma. Both viruses had identical 5' junctions of viral and host sequences, indicating that both arose from the same proviral insertion. The erbB oncogenes of both viruses encoded transmembrane, kinase and C-terminal domains of the chicken epidermal growth factor receptor. The C-terminal domain of the AEV-5005 erbB was complete, whereas that of AAV-5005 contained a 59 amino acid internal deletion (amino acids 993-1051 of the chicken epidermal growth factor receptor). Oncogenicity tests using retroviral constructs containing the erbB sequences from AEV-5005 and AAV-5005 demonstrated that both erbB genes caused erythroblastosis and that the 59 amino acid deletion conferred the ability to induce angiosarcoma. The 59 amino acid deletion also caused increased levels of erbB autophosphorylation in cells grown in the presence of sodium orthovanadate.

Enhanced avidity maturation of antibody to human immunodeficiency virus envelope: DNA vaccination with gp120-C3d fusion proteins.

DNA vaccination can elicit both humoral and cellular immune responses and can confer protection against several pathogens. However, DNA vaccines expressing the envelope (Env) protein of human immunodeficiency virus (HIV) have been relatively ineffective at generating high titer, long-lasting, neutralizing antibodies in a variety of animal models. In this study, we report that fusion of Env and the complement component, C3d, in a DNA vaccine, enhances the titers of antibody to Env. Plasmids were generated that expressed a secreted form of Env (sgp120) from three isolates of HIV and these same forms fused to three tandem copies of the murine homologue of C3d (sgp120-3C3d). Analyses of titers and avidity maturation of the raised antibody indicated that immunizations with each of the sgp120-3C3d-expressing DNAs accelerated both the onset and the avidity maturation of antibody to Env.

Immunogenicity of DNA vaccines expressing human immunodeficiency virus type 1 envelope glycoprotein with and without deletions in the V1/2 and V3 regions.

DNA vaccines that express the human immunodeficiency virus type 1 HXB-2 envelope glycoprotein (Env) with or without deletions of the major variable regions V1/V2 and V3 were tested for the ability to raise enzyme-linked immunosorbent assay (ELISA) and neutralizing antibody in New Zealand White (NZW) rabbits. Three forms of the Envs were examined: gp120, the surface (SU) receptor-binding domain; gp140, the entire extracellular domain of Env; and gp160, the complete form of Env. For the forms of Env containing the variable regions, the gp120-expressing DNA plasmid was more immunogenic than the gp140- or gp160-expressing DNA plasmids. Removing the V1/2 and V3 variable regions increased the immunogenicity of the gp140- and gp160-expressing DNAs. Deletion of the variable regions also resulted in antibody responses against determinants that were not presented by the forms of Env containing the variable regions. Despite the improved immunogenicity, removing the V1/V2 and V3 domains did not improve the ability of Env to raise neutralizing antibodies. These results suggest that increasing the exposure of internal structures of Env that include the CD4-binding site does not necessarily result in the generation of better neutralizing antibody.

Basic mechanisms of DNA-raised antibody responses to intramuscular and gene gun immunizations.

DNA-raised antibody (Ab) responses have been compared for the dependence on CD4+ and CD8+ cells, the longevity of functional antigen (Ag) expression, and the nature of the Ag-presenting cell after intramuscular (i.m.) and gene gun inoculations. A plasmid expressing the hemagglutinin (HA) glycoprotein of influenza virus was used for immunizations of BALB/c mice. Intramuscular and gene gun-raised Abs had similar dependencies on CD4+ and CD8+ cells but different temporal patterns of functional Ag expression. The two methods of DNA immunization also appeared to have different frequencies or types of Ag-presenting cells in the draining lymph nodes and spleen. For both methods of DNA delivery, Ab was independent of CD8+ cells but dependent on CD4+ cells. The CD4 dependence occurred at priming but not booster immunizations and resulted in a 1-month delay in the Ab response. Temporal T-cell transfers from TCR+/+ mice into immunized TCR-/- mice revealed the persistence of DNA-expressed Ag for up to 1 month after both i.m. and gene gun inoculations. For gene gun, but not i.m. immunizations, approximately 90% of the functional Ag expression was lost by 1 week, consistent with the sloughing of the epidermal target site. Despite similar titers of raised Ab, Ag-presenting dendritic cells could be detected in the draining lymph nodes and spleen of gene gun- but not i.m. DNA-immunized mice. In the gene gun-immunized mice, Ag-presenting dendritic cells appeared in the draining lymph nodes before the spleen.

Effect of CpG methylation on isotype and magnitude of antibody responses to influenza hemagglutinin-expressing plasmid.

We previously showed that intramuscular saline DNA immunizations favor the development of an IgG2a-dominant Th1 immune response, whereas gene gun DNA immunizations stimulate the production of an IgG1-dominant Th2 immune response. Several studies have implicated immunostimulatory CpG sequences as the causative factor in the development of Th1 immune responses to saline DNA immunization. To determine whether the Th1 cytokine-inducing properties of CpG sequences in plasmid DNA (pDNA) were responsible for the induction of a Th1 immune response, in vitro methylated and untreated (nonmethylated) hemagglutinin-expressing pDNA were compared for immunogenicity. Methylation abrogated the immunostimulatory activity of pDNA for cultured splenocytes and significantly reduced antigen expression. However, methylation of pDNA was not associated with a change from the induction of IgG2a to IgG1. After immunization with the methylated plasmid, the magnitude of the immune response was reduced. However, the decline in the total antibody response matched the decline in antigen expression. The dose of DNA or the presence of lipopolysaccharide in pDNA likewise did not affect the preferential development of an IgG2a antibody response. Our findings reveal that high levels of CpG sequences are not required for raising IgG2a-predominant, Thl-biased immune responses to intramuscular injections of hemagglutinin-expressing DNA.

Use of DNA encoding influenza hemagglutinin as an avian influenza vaccine.

Recently, we demonstrated that direct inoculation of a hemagglutinin 7 (H7)-expressing DNA could vaccinate chickens against a lethal H7 influenza virus challenge. These experiments used a defective-retroviral-based vector to express H7 (p188) (Robinson et al., 1993). Here, we report protective immunizations using a non-retroviral-based vector for H7 expression (pCMV/H7). Unlike the previously used retroviral-based vector, this vector cannot be transmitted as an infectious agent (as a consequence of phenotypic mixing with exogenous or endogenous virus proteins). Vaccination was accomplished by inoculating young, immunocompetent chickens by each of three routes (intravenous, intraperitoneal, and intramuscular) with 100 micrograms of cesium chloride-purified pCMV/H7 DNA in saline. After two immunizations, birds were challenged via the nares with a lethal dose of a highly virulent chicken influenza virus of the H7 subtype. The results of five independent vaccine trials demonstrated protective immunizations in approximately 60% of the pCMV/H7 DNA-inoculated chickens. By contrast, only 3% of the chickens inoculated with control DNA survived the lethal challenge.

DNA vaccines against rotavirus infections.

Plasmid DNA vaccines encoding for murine rotaviral proteins VP4, VP6, and VP7 were tested in adult BALB/c mice for their ability to induce immune responses and provide protection against rotavirus challenge. Serum antibodies were measured by virus neutralization and by ELISA. Cellular immunity was assessed by measuring cytotoxic T cell (CTL) responses. The vaccines were administered by inoculation into cells of the epidermis with an Accell gene gun (Auragen, Inc., Middleton, WI, USA). Each of the three vaccines elicited rotavirus-specific serum antibodies as measured by ELISA. Virus neutralizing antibodies were detected in mice receiving DNA vaccines encoding for VP4 and VP7, but not in those which received the plasmid encoding for VP6. Vaccines encoding for VP4, VP6, or VP7 generated virus-specific CTL responses in recipient mice. Efficacy of the vaccines was determined by challenge with homotypic rotaviruses. Each of the three vaccines was effective in protecting mice against infection after rotavirus (100 ID50) challenge. Significant reductions (p < 0.0002, analysis of variance) in viral excretion measured over a 9 day period were seen in mice receiving the DNA vaccines compared with mice that received control plasmids.

DNA vaccines: a review of developments.

Immunisation with purified DNA is a powerful technique for inducing immune responses. The concept is very simple, involving insertion of the gene encoding the antigen of choice into a bacterial plasmid, and injection of the plasmid into the host where the antigen is expressed and induces humoral and cellular immunity. This technology can induce immunity to all antigens that can be encoded by DNA; this includes all protein, but not carbohydrate, antigens. DNA immunisation appears to result in presentation of antigens to the host's immune system in a natural form, similar to that achieved with live attenuated vaccines. The most efficacious routes for DNA immunisation are bombardment with particles coated with DNA (gene-gun), followed by intramuscular and intradermal administration. The efficiency of transfection of host cells is low, but sufficient to induce immunological responsiveness. The DNA plasmid is retained in the transfected cells in an unintegrated form for the life of the cell. The majority of transfected cells are eliminated, but residual expression has been detected for longer periods. In animal model systems, DNA immunisation has been shown to induce protective immunity to influenza, herpes, rabies, hepatitis B and lymphocytic choriomeningitis viruses, and to malaria and mycobacteria. However, strategies to induce protective immunity to HIV and other disease agents remain to be developed. DNA vaccines permit modulation of the immune response by altering the route or method of DNA administration, by including immunostimulatory sequences in the plasmid, and by co-administration of cytokine genes with the gene encoding the antigen of interest. A T helper 1 response provides cell-mediated immune killing of infected cells and neutralising antibody production, while a T helper 2 response induces IgE and allergic responses. The advantages of DNA immunisation are: similarity to live attenuated vaccination but without the possibility of contamination with undesirable agents;correct presentation of antigen;combinations of DNA-encoded antigens and/or cytokines may be administered;genetic stability;potential speed of making new vaccines with genetic identity;development of vaccines for agents that cannot be grown in culture;no need for a cold chain; andpossibility of modulation of the immune response. The perceived risks include: integration of the plasmid into the host genome;induction of anti-DNA antibodies and autoimmunity; andinduction of tolerance. The available information concerning safety is encouraging, with the risk of integration being considered to be orders of magnitude below the spontaneous mutation frequency in humans. DNA immunisation offers the possibility of extending the control of infectious diseases far beyond those that are currently controlled by conventional and recombinant vaccines, to include vaccines for parasites and cancer. However, it is currently too early to predict the future extent of use of DNA vaccines in human immunisation programmes because the initial clinical trials are still in progress.

DNA vaccines: basic mechanism and immune responses (Review).

DNA vaccines raise immune responses by expressing proteins in vaccinated hosts. Responses are raised by nanogram levels of protein expression. Popular methods of DNA delivery include intramuscular (i. m.) injections of DNA in saline and gene gun delivery of DNA-coated gold beads to the epidermis. Professional antigen-presenting cells derived from the bone marrow present DNA-expressed antigens to T-cells. Following gene gun immunizations directly transfected dendritic cells present antigens, whereas following i.m. immunizations both directly transfected dendritic cells and macrophages can present antigen. For both methods of DNA delivery, non-lymphoid cells can serve as factories of antigen for professional antigen presenting cells. Gene gun immunizations depend on antigen expression at the skin target whereas i.m. immunizations are largely independent of DNA expression in the muscle target. For both methods, antigen expression capable of initiating an immune response persists for about one month. intramuscular deliveries of DNA tend to raise type 1 T-cell help for intracellular and plasma membrane antigens but type 2 T-cell help for secreted antigens. Gene gun immunizations tend to raise type 2 T-cell help for both cell-associated and secreted antigens. In mice, DNA-raised immune responses can be equivalent to those raised by viral infections for both the height and longevity of antibody and cytotoxic T-cell responses.