Induction of a TH1 type cellular immune response to the human immunodeficiency type 1 virus by in vivo DNA inoculation

DNA inoculation is capable of producing antigens intracellularly for ultimate presentation to the cellular and humoral components of the immune system and has potential for vaccine strategies against a number of infectious pathogens including HIV-1. It is well documented that the antigenic diversity of HIV-1 and its high level of nucleotide mutations during reverse transcription can lead to escape from immune surveillance. However, data suggest that a CD8-mediated cytotoxic T lymphocyte response may be less susceptible to escape mutants. We have shown previously that in vivo inoculation of rodents and non-human primates with plasmid expression vectors encoding HIV-1 gene products leads to production of HIV-1 antigens and results in the production of both cellular and humoral immune responses. In addition we have also demonstrated previously that these responses lead to protection in several in vivo models. We further demonstrate here that the cellular response induced is a type TH1 response and specific lysis of HIV-infected targets is CD8-mediated.

Mucosal immunization with a DNA vaccine induces immune responses against HIV-1 at a mucosal site

Mucosal immunity is the first defense system in protection against mucosal infection by sexually transmitted diseases and subsequent systemic dissemination of infection. Development of vaccines which can induce protective mucosal immunity would have great promise for preventing sexually transmitted diseases including AIDS. DNA vaccines have recently shown certain advantages over other types of vaccines in safety and elicitation of specific immune responses. We have hypothesized that direct delivery of a DNA plasmid coding the HIV-1 envelope (pcMN160) via mucosal routes will stimulate mucosal immunity against HIV-1. The expression of DNA plasmid inoculated intravaginally was detected in various tissues. Intravaginal inoculation of pcMN160 elicits production of vaginal immunoglobulins which specifically bind to the HIV-1 envelope and neutralize HIV-1 infectivity in vitro. These results indicate the feasibility of inducing mucosal immunity following mucosal inoculation of DNA vaccines. When coupled with systemic inoculation of appropriate DNA constructs, effective mucosal and systemic immunity may be generated.

Phenylmercury and its mobilization in the organism by a metal complex-forming substance: 2,3-dimercapto-1-propane sodium sulfonate

Workers handling dressing machines for seed treatment with the product Agronal, containing a phenylmercury chloride fungicide, were exposed to high concentrations of phenylmercury dust in the working environment. Urine analyses for mercury result in concentration of up to 0.1 mg Hg/l of urine. After administration of a complex-forming substance-Unitol (2,3-dimercapto-1-propane sodium sulfonate)-a higher urinary excretion of mercury occurred. The amount of mercury excreted confirmed its deposit in the organism. It was speculated that subjective complaints by workers handling dressing machines could be caused by high exposure to phenylmercury. This suggestion cannot, however, be fully accepted because the complaints were not necessarily specific for mercury only, but could also have been caused by factors of nontoxic origin, such as stress at the workplace, discontent with work and environmental hygiene conditions, conflicts and alcoholism. Most probably, it was a case of interpotentiation of the effects of toxic and non-toxic nature.

DNA inoculation induces cross clade anti-HIV-1 responses

Nucleic acid or DNA immunization represents a novel approach to vaccine and immune therapeutic development. The direct injection of expression cassettes into a living host results in in vivo gene expression and immune activation. In the case of HIV-1 it has been shown by our laboratory that facilitated injection mimicks aspects of live attenuated vaccines and that both humoral and cellular responses can be induced upon injection of a nucleic acid sequence directly into a host target tissue. Antisera from HIV-1 plasmid expression cassette-immunized animals contain anti-HIV envelope glycoprotein immune responses. The antiserum neutralizes HIV-1 infection and inhibits cell to cell infection in vitro. Cellular immune responses have also been evaluated. We observed both T cell proliferation and isotype switching consistent with the production of relevant T helper immune responses in immunized animals. Furthermore it was demonstrated that CTL lysis of relevant env-expressing targets was similarly induced. These studies further define the importance of evaluating this new technology for vaccine and immune therapeutic development for HIV-1 as well as for other human viral pathogens.

Induction of humoral and cellular immune responses to the human immunodeficiency type 1 virus in nonhuman primates by in vivo DNA inoculation

DNA inoculation has the potential to produce antigens in a native as well as a host-"customized" form for presentation to the immune system. As such this technology may have relevance for vaccine/immune therapeutic strategies for a variety of infectious pathogens. In rodents in vivo inoculation of plasmid expression vectors encoding HIV-1 gene products leads to production of HIV-1 antigens in vivo, resulting in the production of both cellular and humoral immune responses. In primates only preliminary studies of serology have been reported. Here we report further evaluation of this new technology as a method to induce humoral and particularly cellular immune responses against a human pathogen, the HIV-1 virus, in nonhuman primates. Following inoculation and boosting of animals with an HIV gp160 plasmid expression vector we observed the induction of neutralizing responses against two diverse HIV-1 isolates in 2 of 3 vaccinated animals. T cell proliferative responses to HIV antigens were also observed in all plasmid-inoculated animals and specific cross-reactive cytotoxic T lymphocyte responses were developed in vaccinated animals. This report establishes the ability of DNA inoculation to induce cellular immune responses in nonhuman primates and suggests that further investigation of this technology with regard to human vaccine or immune therapeutic development is therefore warranted.

Immunization by direct DNA inoculation induces rejection of tumor cell challenge

Direct DNA inoculation is the basis for a new technology that has been successfully used for in vivo induction of both humoral and cellular immune responses. However, the immunological parameters of this new approach remain to be evaluated in detail. We report here that direct DNA inoculation can induce protection from malignant tumor cell challenge through the generation of specific immune responses directed against antigens displayed on the tumor cells. The protected mice remain tumor-free for more than 1 year post-challenge. Memory responses upon tumor rechallenge were observed for both humoral and cellular immunity. Inoculated animals were able to reject otherwise lethal tumors several months following the original DNA inoculation protocol. These in vivo protective responses suggest that further analysis of this technology for vaccine development or immune therapeutic strategies is warranted.

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.

DNA inoculation as a novel vaccination method against human retroviruses with rheumatic disease associations

There are a number of rheumatologic manifestations of human retroviral infections associated with human immunodeficiency virus type I (HIV-I) and the human T-cell leukemia virus type I (HTLV-I) including arthritis, Sjøgren's syndrome-like symptoms as well as other varied autoimmune phenomena. Infection with HTLV-1 may be directly involved in the etiology and/or pathogenesis of an arthritic condition similar to rheumatoid arthritis. We have been characterizing a new vaccination strategy against human retroviral infections, designated DNA inoculation. This procedure involves the intramuscular injection of DNA plasmids which express specific human retroviral antigens. This technique results in the development of humoral and cellular immune responses against these proteins. Specifically, this method has been successfully used to develop immune responses against HIV-I and HTLV-I. The availability of rat and rabbit infection models for HTLV-I, coupled with the successful development of immune responses in these animals after DNA inoculation with an HTLV-I envelope expressing plasmid, will allow the efficacy of this vaccination technique to be evaluated with protection against in vivo viral challenge as an endpoint.

DNA inoculation induces neutralizing immune responses against human immunodeficiency virus type 1 in mice and nonhuman primates

DNA, or genetic, inoculation mimics aspects of attenuated vaccines in that synthesis of specific foreign proteins is accomplished in the host. These proteins can be processed and presented on the relevant major histocompatibility complex (MHC) antigens and ultimately become the subject of immune surveillance. Very recently, we have described the use of the new technology to generate immune responses in mice against the human immunodeficiency virus type 1 (HIV-1) envelope using a gp160 DNA construct. Further analysis of this technology specifically in regard to HIV vaccine design is clearly important. In this report, we describe the analysis of additional HIV constructs as immunogens in both mice and report the use of this genetic immunization technology in nonhuman primates. In these studies, successful seroconversion occurs in more than 70% of the mice following the second immunization with 100 micrograms of construct DNA; three and four immunizations result in routinely 100% seroconversion of the mice. Furthermore, the same strategy has successfully seroconverted primates following their second inoculation, resulting in the generation of both antiviral and neutralizing antibodies in this animal species. These studies are the first report of which we are aware that demonstrate successful immunization of nonhuman primates through genetic vaccination technology and the first to describe genetic immunization of primates against HIV antigens. This technology has relevance for the development of safe and efficacious immunization strategies against HIV because it provides for relevant antigen production in vivo without the use of infectious agents.

Genetic infection induces protective in vivo immune responses

Drug-induced abortive retroviral infection has been reported to induce both T-cell and B-cell immunity in vivo. We sought to analyze if replication-incompetent retroviruses could induce the development of similarly protective in vivo immune responses in a more desirable fashion. To evaluate retroviral transduction vaccination (genetic infection), a plasmid encoding human CD4 in a retroviral vector was transfected into the pA317 amphotropic retroviral packaging system. The resulting replication defective retrovirus was used to transduce BALB/c mice prior to tumor challenge with human CD4. Immunization elicited specific humoral and cellular anti-human CD4 responses. We evaluated anti-cell responses using a tumor model system. We observed that BALB/c mice challenged with SP2/0 lymphoma cells develop lethal tumors and die within 7 weeks of challenge. Cloned SP2/0 cells stably transfected with the human cell-surface antigen CD4 also develop tumors in naive mice and succumb to the tumors in a similar manner to SP2/0 inoculated animals. In contrast, CD4 retrovirus-transduced animals, when challenged with the CD4-expressing SP2/0 cells, demonstrated a low incidence of tumors and significantly enhanced survival compared to the mice immunized similarly with human CD8 retrovirus. These results establish an in vivo tumor challenge system with relevance to the development of protective in vivo immune responses, and indicate that genetic infection is a useful technique for inducing protective immunity.