Richard S. Ginsberg

First Human Trial of a DNA-Based Vaccine for Treatment of Human Immunodeficiency Virus Type 1 Infection: Safety and Host Response

A DNA-based vaccine containing human immunodeficiency virus type 1 (HIV-1) env and rev genes was tested for safety and host immune response in 15 asymptomatic HIV-infected patients who were not using antiviral drugs and who had CD4+ lymphocyte counts of > or = 500 per microliter of blood. Successive groups received three doses of vaccine (30, 100, or 300 microg) at 10-week intervals in a dose-escalation trial. Vaccine administration induced no local or systemic reactions, and no laboratory abnormalities were detected. Specifically, no patient developed anti-DNA antibody or muscle enzyme elevations. No consistent change occurred in CD4 or CD8 lymphocyte counts or in plasma HIV concentration. Antibody against gp120 increased in individual patients in the 100- and 300-/microg groups. Some increases were noted in cytotoxic T lymphocyte activity against gp160-bearing targets and in lymphocyte proliferative activity. The safety and potential immunogenicity of an HIV-directed DNA-based vaccine was demonstrated, a finding that should encourage further studies.

Vaccination of Seronegative Volunteers with a Human Immunodeficiency Virus Type 1 envlrev DNA Vaccine Induces Antigen-Specific Proliferation and Lymphocyte Production of β-Chemokines

There is a pressing need to test novel vaccine concepts in an effort to develop an effective vaccine for human immunodeficiency virus (HIV) type 1. A phase I clinical study was done to test the immunogenicity of an HIV env/rev DNA vaccine, which was administered intramuscularly to HIV-1-seronegative persons. Subjects received 3 doses of vaccine at a single concentration (100 or 300 microgram) at 0, 4, 8, and 24 weeks. In at least 1 of multiple assays, the 6 subjects who received the 300-microgram dose had DNA vaccine-induced antigen-specific lymphocyte proliferative responses and antigen-specific production of both interferon-gamma and beta-chemokine. Furthermore, 4 of 5 subjects in the 300 microgram-dose group responded to both the rev and env components of the vaccine. The responses did not persist within inoculated individuals and scored in different individuals at different times in the trial. This study supports that HIV-1 DNA vaccine antigens can stimulate multiple immune responses in vaccine-naive individuals, and it warrants additional studies designed to enhance DNA vaccine immunogenicity.

DNA vaccination with HIV-1 expressing constructs elicits immune responses in humans

Humoral and cellular immune responses have been produced by intramuscular vaccination with DNA plasmids expressing HIV-1 genes, suggesting possible immunotherapeutic and prophylactic value for these constructs. Vaccination with these constructs has decreased HIV-1 viral load in HIV-1-infected chimpanzees. In addition, naive (i.e. non-HIV-1-infected) chimpanzees were protected against a heterologous challenge with HIV-1. Ongoing phase I clinical trials show that therapeutic vaccinations indeed boost anti-HIV-1 immune responses in humans. A therapeutic phase I trial on humans with these constructs induced a good safety profile and also demonstrated an immunological potentiation. These findings indicate that further studies with these constructs in humans are warranted.

T-cell responses induced in normal volunteers immunized with a DNA-based vaccine containing HIV-1 env and rev.

Objective: An effective HIV-1 vaccine will likely need to induce strong cell-mediated immunity in humans. Therefore, we examined the ability of a DNA HIV-1 vaccine to induce a T-cell response in HIV-1 seronegative humans. Design: Individuals were enrolled in a phase I clinical trial of safety and immune responses to an env/rev-containing plasmid at doses of 100, 300 or 1000 μg. Peripheral blood mononuclear cells (PBMC) samples were analyzed by standard lymphocyte proliferation, cytotoxic T lymphocyte (CTL) and ELISPOT techniques. Results: PBMCs from subjects immunized with doses as low as 300 μg proliferated in vitro to env (four of six) or rev (three of six) proteins. Importantly, when the dose of vaccine was increased to 1000 μg of DNA, lymphocytes secreted IFN-gamma in an ELISPOT assay following in vitro stimulation with env (three of six) or rev (four of six) proteins. Conclusion: We observed HIV-1 DNA plasmid vaccines induce CD4 T-helper cell responses in humans. We observed a discrepancy in the CD4 versus CD8 response suggesting the importance of analyzing both compartments in clinical evaluation. Furthermore, this report demonstrates the high level of immunogenicity of rev and its importance as a component of a prophylactic vaccine for HIV-1.

Immunogenicity of a new purified fusion protein vaccine to respiratory syncytial virus: A multi-center trial in children with cystic fibrosis

A third generation, purified fusion protein (PFP-3) vaccine was developed to prevent severe respiratory syncytial virus (RSV) disease in high-risk groups. A phase II, multi-center, adjuvant-controlled trial was performed in RSV seropositive children with cystic fibrosis (CF); 151 received the adjuvant-control and 143 received the vaccine. Details of the vaccine-induced immune response are presented. At enrollment, RSV-specific, serum antibodies were comparable between both groups. A highly sensitive and specific serum antibody vaccine profile was established for the PFP-3 vaccine. At post-vaccination and end-of-study, RSV-specific, neutralizing antibody (Nt Ab) and binding antibody (Bd Ab) to the fusion (F) protein were significantly higher in PFP-3 vaccinees. After 28 days post-vaccination, Nt Ab and Bd Ab to F protein titers declined slowly at rates of 0.23 and 0.37 log2 per month, respectively. The PFP-3 vaccine-induced a robust immune response that lasted throughout the RSV season.

Safety and immune responses to a DNA-based human immunodeficiency virus (HIV) type I env/rev vaccine in HIV-infected recipients: follow-up data.

To the Editor—We recently reported the safety and immunologic response to a DNA vaccine containing env/rev in a group of untreated healthy human immunodeficiency virus (HIV)– infected subjects with CD4 lymphocyte counts 1500 cells/mL [1]. No significant adverse experiences occurred, with some evidence for antibody responses and occasional cell-mediated immune responses. We now report an additional cohort immunized with a 300-mg dose by jet injection (JI) or by needle (N), follow-up safety data over 12.5 years for the whole cohort, and results of boosting with 1 mg of vaccine. The safety profile for the vaccine continues to be excellent. No participant experienced a significant adverse response requiring interruption or withdrawal from study. Anti-DNA antibody was detected in 1 subject with a borderline antinuclear antibody level before vaccination, and 2 others had transient chemistry abnormalities immediately before boosting, with resolution 2 weeks later. Local mild-to-moderate reactions were noted with 9 of 17 JI injections, compared with 4 of 54 with N injections. We compared the immune responses to primary vaccine series (300 mg 3 3) administered by JI versus N, measured at entry, week 21 (1 week after 3d dose), and week 36 (4 months after 3d dose). Responses were defined as in our original paper [1]. No subject in either 300-mg group had a >20% increase or decrease in CD4 lymphocyte count, compared with the value at entry. No subject had a >0.5 log change in viral titer in plasma, compared with the value at entry. For lymphoproliferative response, we defined response as stimulation index (SI) >4 above baseline value. Four subjects in the JI group were studied: 1/4 responded to gp120 and rev antigens; 1/4 responded only to rev. Three patients in the N group were studied: 3/3 responded to gp120; none responded to rev. We defined an antibody response as a geometric mean titer >23 the baseline value. After JI, 0/5 responded, whereas 3/5 immunized by N responded. For immune responses to 1 mg boosting, we compared values at time of boost (>6 months after primary immunization series) with those 2 and 4 weeks later. Five of the 12 subjects available for boosting had begun antiretroviral therapy. No subject had a >20% increase or decrease in CD4 lymphocyte count, compared with the value at boost. For HIV quantitation in plasma, no subject had a >0.5 log change in viral titer, compared with titer at boost. When stimulated with gp160, none of 12 subjects showed a rise in SI (range, 0.8–5.1 before boost and 0.8–4.5 after boost); SIs increased in 3 of 12 subjects in response to rev (range, 0.5–5 before and 0.7–6.1 after). The responders were not receiving antiretroviral therapy. Three of 10 assessable subjects had a >2-fold geometric mean titer rise, compared with levels at boost; none had been receiving antiretroviral therapy. There were no clear differences in CD4 cell count, viral load, or immunologic responses between patients immunized by JI and those immunized by N, although more lymphoproliferative activity (LPA) and antibody increases were seen in the N-injected cohort. Boosting of all cohorts (30 mg-, 100 mg-, and both 300-mg groups) with 1 mg of the construct resulted in occasional LPA and antibody responses (without regard to whether they had initiated antiretroviral therapy) and no significant changes in CD4 cell counts or viral loads. Adverse experiences were minor, although more local tenderness was seen after JI. No subject withdrew because of toxicity. Safety monitoring for 12.5 years did not reveal any adverse events that were interpreted as related to the vaccine. The study began in 1994, before the dynamic daily turnover in CD4 lymphocyte counts and viral load was recognized [2, 3]. It is now theorized that viral replication and CD4 turnover must be suppressed to elicit a potentially protective immune response to HIV vaccine [4, 5]. We are currently conducting such a trial, using env/revand gag/pol-containing constructs in patients whose viral production is maximally suppressed with highly active antiretroviral therapy [6].

HIV-1 DNA vaccines and chemokines

DNA vaccines have a demonstrated ability to induce humoral and cellular immune responses in animal models and humans. The technology, although it dates back to the 1950s, has had an insurgence of interest within the past few years following concurrent research papers. The basic technology is being applied broadly to viral, bacterial and parasitic infections. It has also been demonstrated that genes delivered via plasmid expression vectors result in expression of functional proteins in the inoculated host. Further, injection of plasmids encoding cytokine, chemokine or co-stimulatory molecules, also referred to as immunomodulatory plasmids can lead to the further expansion of this technology to include directed immunology. We have been developing DNA technology specifically with a focus as a vaccine against HIV-1 infection. We report that such vaccines can stimulate immune responses in a variety of relevant animal systems including humoral and cellular responses as well as the production of beta-chemokines. We describe that the beta-chemokines can both modulate the immune response induced by DNA vaccines and be modulated by the DNA vaccines in the murine and chimpanzee models as well as in humans.

Phase I Study of a Herpes Simplex Virus Type 2 (HSV-2) DNA Vaccine Administered to Healthy, HSV-2-Seronegative Adults by a Needle-Free Injection System

ABSTRACT We conducted a double-blind, vehicle-controlled, dose escalation safety and immunogenicity trial of a candidate herpes simplex virus type 2 (HSV-2) surface glycoprotein D2 (gD2) DNA vaccine administered by use of a needle-free device. Sixty-two healthy adults were randomized using a 4:1 vaccine-to-placebo ratio. Half of the participants were HSV-1 seronegative, and all were HSV-2 seronegative. Vaccine doses included 100 μg, 300 μg, 1,000 μg or 3,000 μg of a plasmid expressing the gD2 protein. Subjects received vaccine at 0, 4, 8, and 24 weeks. Some subjects received an additional 1,000-μg boost at 52 weeks. We found that the vaccine was safe and well tolerated, with most adverse events being local site reactions. No dose-limiting toxicities were observed. gD2-specific cytotoxic T-lymphocyte and lymphoproliferation responses were detected 2 weeks after the third vaccine injection in one of four HSV-1-seronegative, HSV-2-seronegative participants who received 3,000 μg of vaccine. A DNA-based vaccination strategy against HSV-2 appears to be safe and may generate a vaccine-specific cellular immune response, but high vaccine doses are likely needed to elicit an immune response in most vaccinees.