A factor VIII-deficient knockout mouse was used as a model for severe hemophilia A to characterize the immune response to recombinant human factor VIII (fVIII) and to study new approaches for induction of immune tolerance to fVIII. Mice initially received periodic injections of fVIII in doses similar to those used for the treatment of human hemophilia A. To induce immune tolerance, a hamster monoclonal antibody specific for murine CD40 ligand (CD40L or CD154) was injected with fVIII. Control mice received fVIII alone or fVIII and hamster immunoglobulin G. After treatment, humoral and cellular immune responses were evaluated. Ninety-five percent of anti-CD40L-treated mice had lower titers of anti-fVIII antibody (less than 1 g/mL) compared with fVIII-injected control mice (mean, 18 g/mL). To determine whether anti-CD40L treatment induces long-term immune tolerance, mice were rechallenged 3 times with fVIII alone. At 150 days after treatment, 12 of 22 anti-CD40L-treated mice remained tolerant to fVIII (anti-fVIII antibody titers less than 1 g/mL). However, tolerant mice immunized with tetanus toxoid (TT) developed high anti-TT antibody, demonstrating that tolerance is fVIII specific. T cells from tolerant mice showed impaired proliferative responses after stimulation with fVIII in vitro and lack of production of the cytokines interleukin-2 (IL-2), IL-4, interferon ␥, and IL-10. These results demonstrate that long-term immune tolerance to fVIII was effectively induced after early blockade of CD40-CD40L interaction. In addition, the lack of tolerance in this model was associated with the expression of a Th2 phenotype.

Our findings suggest that the polymorphism of metalloproteinases-1 might have a role in mediating susceptibility to pelvic organ prolapse.

The hyperacute immune response in humans is a potent mechanism of xenograft rejection mediated by complementfixing natural antibodies recognizing A(1,3)-galactosyl epitopes (AGal) not present on human cells. We exploited this immune mechanism to create a whole cell cancer vaccine to treat melanoma tumors. B16 melanoma vaccines genetically engineered to express AGal epitopes (B16AGal) effectively treated preexisting s.c. and pulmonary AGal-negative melanoma (B16Null) tumors in the A(1,3)-galactosyltransferase knockout mouse model. T cells from mice vaccinated with B16AGal recognized B16Null melanoma cells measured by detection of intracellular tumor necrosis factor-A. We showed successful adoptive transfer of immunity to recipient mice bearing lung melanoma metastasis. Mice receiving lymphocytes from donors previously immunized with B16AGal had reduced pulmonary metastases. The transfer of lymphocytes from mice vaccinated with control vaccine had no effect in the pulmonary metastasis burden. This study unequivocally establishes for the first time efficacy in the treatment of preexisting melanoma tumors using whole cell vaccines expressing AGal epitopes. Vaccination with B16Agal induced strong long-lasting cell-mediated antitumor immunity extended to B16Null. These data formed the basis for the testing of this therapeutic strategy in human clinical trials currently under way. (Cancer Res 2005; 65(22): 10555-61)

The excretory-secretory antigen of Fasciola hepatica (ESA) is involved in the suppressive phenomena of cellular immune responses in rats. The ESA can depress the proliferative response of spleen mononuclear cells and inhibit nitric oxide (NO) production by peritoneal cells. In the present study we identified ESA proteins of ca 24 kDa, which shared significant sequence homology to glutathione-S-transferase (GST) obtained from homogenates of F. hepatica adults, other helminths and different mammals. When the dimeric form of these proteins ca 48 kDa was cultured with rat spleen cells, a significant decrease of proliferative response to Con A was detected, starting from 20 micrograms/ml of ESA protein (P < 0.03). We also observed a significant inhibition of nitrite production by incubation with the dimeric form in normal peritoneal macrophages (P < 0.04). These results indicated that the GST secreted by the parasite could be involved in evasion of the parasite from the host immune response.