Stuart J. Kahn

A clinical trial to evaluate the safety and immunogenicity of the LEISH-F1 + MPL-SE vaccine for use in the prevention of visceral leishmaniasis

Healthy Indian adult volunteers, with or without a history of leishmaniasis, were evaluated for evidence of previous infection with Leishmania donovani based on the direct agglutination test (DAT). Three cohorts of 6 DAT-negative and 6 DAT-positive subjects were enrolled in an open-label, dose-escalating, uncontrolled clinical trial and received three injections of the LEISH-F1+MPL-SE vaccine (consisting of 5μg, 10μg, or 20μg recombinant Leishmania polyprotein LEISH-F1 antigen+25μg MPL®-SE adjuvant). The study injections were given subcutaneously on days 0, 28, and 56, and the subjects were followed through day 168 for safety and immunological endpoints. The vaccine was safe and well-tolerated in DAT-negative and DAT-positive subjects and induced T-cell production of IFN-γ and other cytokines in response to stimulation with the LEISH-F1 antigen. This clinical trial shows that the LEISH-F1+MPL-SE vaccine is safe and immunogenic in healthy subjects with and without history of previous infection with Leishmania donovani.

A clinical trial to evaluate the safety and immunogenicity of the LEISH-F1+MPL-SE vaccine when used in combination with meglumine antimoniate for the treatment of cutaneous leishmaniasis.

Forty-four adult patients with cutaneous leishmaniasis (CL) were enrolled in a randomized, double-blind, controlled, dose-escalating clinical trial and were randomly assigned to receive three injections of either the LEISH-F1+MPL-SE vaccine (consisting of 5, 10, or 20 μg recombinant Leishmania polyprotein LEISH-F1 antigen+25 μg MPL-SE adjuvant) (n=27), adjuvant alone (n=8), or saline placebo (n=9). The study injections were given subcutaneously on Days 0, 28, and 56, and the patients were followed through Day 336 for safety, immunological, and clinical evolution endpoints. All patients received chemotherapy with meglumine antimoniate starting on Day 0. The vaccine was safe and well tolerated. Nearly all vaccine recipients and no adjuvant-alone or placebo recipients demonstrated an IgG antibody response to LEISH-F1 at Day 84. Also at Day 84, 80% of vaccine recipients were clinically cured, compared to 50% and 38% of adjuvant-alone and placebo recipients. The LEISH-F1+MPL-SE vaccine was safe and immunogenic in CL patients and appeared to shorten their time to cure when used in combination with meglumine antimoniate chemotherapy.

A Clinical Trial to Evaluate the Safety and Immunogenicity of the LEISH-F1+MPL-SE Vaccine When Used in Combination With Sodium Stibogluconate for the Treatment of Mucosal Leishmaniasis

Adult patients with mucosal leishmaniasis (ML) were enrolled in a randomized, double-blind, placebo-controlled, dose-escalating clinical trial and were randomly assigned to receive three injections of either the LEISH-F1+MPL-SE vaccine (consisting of 5, 10, or 20 μg recombinant Leishmania polyprotein LEISH-F1 antigen+25 μg MPL(®)-SE adjuvant) (n=36) or saline placebo (n=12). The study injections were given subcutaneously on Days 0, 28, and 56, and the patients were followed through Day 336 for safety, immunological, and clinical evolution endpoints. All patients received standard chemotherapy with sodium stibogluconate starting on Day 0. The vaccine was safe and well tolerated, and induced both humoral and cell-mediated immune responses. Furthermore, intracellular cytokine staining showed an increase in the proportion of memory LEISH-F1-specific IL-2(+) CD4 T-cells after vaccination, which was associated with clinical cure. This clinical trial shows that the LEISH-F1+MPL-SE vaccine is safe and immunogenic in patients with ML.

Treatment with α-Galactosylceramide Before Trypanosoma cruzi Infection Provides Protection or Induces Failure to Thrive

Trypanosoma cruzi, a protozoan parasite, chronically infects many mammalian species and triggers a chronic inflammatory disease. Invariant Vα14 NK T (iNKT) cells are a regulatory subset of T cells that can contribute to protection against pathogens and to control of chronic inflammatory diseases. α-Galactosylceramide (α-GalCer) is an iNKT cell-specific glycolipid Ag: a single immunization with α-GalCer stimulates robust IFN-γ and IL-4 production by iNKT cells, while multiple immunizations stimulate IL-4 production, but limited IFN-γ production. We recently demonstrated that iNKT cells help control T. cruzi infection and affect the chronic Ab response. Therefore, α-GalCer treatment might be used to increase protection or decrease chronic inflammation during T. cruzi infection. In this report, we show that a single dose of α-GalCer before T. cruzi infection decreases parasitemia. This protection is independent of IL-12, but dependent upon iNKT cell IFN-γ. In addition, α-GalCer treatment of the IFN-γ−/− mice exacerbates parasitemia through IL-4 production. Furthermore, a multiple dose regimen of α-GalCer before T. cruzi infection does not lower parasitemia and, surprisingly, after parasitemia has resolved, causes poor weight gain. These data demonstrate that during T. cruzi infection glycolipids can be used to manipulate iNKT cell responses and suggest the possibility of developing glycolipid treatments that can increase protection and possibly decrease the chronic inflammatory pathology.

During acute Trypanosoma cruzi infection highly susceptible mice deficient in natural killer cells are protected by a single α-galactosylceramide treatment

The protective immune response against Trypanosoma cruzi is improved by treatment with the natural killer (NK) T‐cell glycolipid antigen α‐galactosylceramide (α‐GalCer). A single α‐GalCer treatment of mice before T. cruzi infection decreases parasitaemia and prolongs survival. This protection is dependent on CD1d‐restricted NKT cells and interferon‐γ (IFN‐γ) suggesting that α‐GalCer‐activated NKT cells produce IFN‐γ, which stimulates the cells of the innate and adaptive immune responses to provide protection. To learn which cells provide protection we investigate here α‐GalCer treatment of mice deficient in different immune cells. Surprisingly, although NK cells provide protection against T. cruzi, and are a major source of IFN‐γ following α‐GalCer treatment, NK cells are not required for the α‐GalCer‐induced protection. The α‐GalCer treatment of NK‐cell‐depleted mice controlled parasitaemia and prevented death. In contrast, phagocytes, helper T cells and cytotoxic T cells are required. Furthermore, α‐GalCer treatment of MHC II–/– or CD8α–/– mice exacerbated the infection, demonstrating that α‐GalCer treatment induces some responses that favour the parasite. In summary α‐GalCer protection against T. cruzi required multiple cellular responses, but not the response of NK cells. These results provide useful information because α‐GalCer is being developed as therapy for infections, autoimmune diseases, allergy and cancers.

The SA85-1.1 Protein of the Trypanosoma cruzi trans-Sialidase Superfamily Is a Dominant T-Cell Antigen

ABSTRACT Trypanosoma cruzi currently infects 18 million people, and 30% of those infected develop a chronic inflammatory process that causes significant morbidity or mortality. The major histocompatibility complex class II (MHC-II)-restricted T-cell response is critical to the control of the infection and to the ensuing inflammatory pathology. The specific epitopes or major antigens of this response have not been identified. The parasite simultaneously expresses variant members of the trans-sialidase superfamily. To begin to analyze the MHC-II response to these variant proteins, the response to a single surface protein, SA85-1.1, was initiated. These studies have demonstrated that a biased gamma interferon (IFN-γ) response to the SA85-1.1 protein develops during T. cruzi infection. In addition, adoptive transfer of a CD4 clone that recognizes an SA85-1.1 epitope, named epitope 1, and immunization with a peptide encoding epitope 1 were protective and suggested that epitope 1 may be immunodominant. In this report IFN-γ intracellular staining demonstrated that splenocytes from acutely and chronically infected mice, incubated with SA85-1.1 protein or peptides that encode epitope 1, result in IFN-γ synthesis by 4 to 6% of the splenic CD4 cells. These data indicate that during T. cruzi infection epitope 1 is a major epitope and that 4 to 6% of the CD4 cells are stimulated by a single trans-sialidase superfamily epitope and suggest that a combination of trans-sialidase superfamily proteins combines to stimulate a majority of CD4 cells. These data suggest that during T. cruzi infection the CD4 response to thetrans-sialidase superfamily is critical to the protective response and to the ensuing chronic inflammatory pathology.