Inhibition of allergic reactions with antibodies to IgE.

Numerous clinical studies show that direct interference with the IgE response leads to a decrease or elimination of allergic symptoms. The aim of these studies was to design a therapy aimed at decreasing IgE levels in order to ameliorate atopic disease. To this end, a murine monoclonal antibody, MAE11, directed against IgE was identified, which had all the properties necessary to interfere with IgE responses, but lacked the harmful side effects of inducing receptor cross-linking. The antibody was selected on the basis of its ability to bind circulating IgE at the same site as the high-affinity receptor, thus blocking the binding of IgE to mast cells and basophils. To allow for possible chronic administration and to avoid the problems of antigenicity, MAE11 was humanized. The best of several humanized variants, version 25 (rhumAb-E25) was selected since it possessed binding affinity and biological activity comparable to MAE11. Clinical studies are underway to determine the safety and efficacy of this treatment for allergic rhinitis and asthma.

A novel bioactivity assay for monoclonal antibodies directed against IgE.

A novel bioactivity assay has been developed to quantitate the biological activity of a humanized, monoclonal anti-IgE antibody (rhuMAbE25) in human whole blood. Heparinized blood specimens from prescreened healthy donors were sensitized for 2 h with a constant amount of human plasma containing IgE specific for ragweed and then challenged with ragweed allergen. Histamine was released in a dose-dependent fashion and reached plateau levels after 30 min. As expected, the release of histamine by ragweed allergen was time, temperature and Ca2+ dependent, and could be enhanced by the presence of 33% deuterium oxide. Allergen-triggered release could be inhibited by rhuMAbE25 with an effective dose range from 0.1 to 1 microgram/ml. Preincubation with other humanized MAbs, which exhibit 95% homology to rhuMAbE25 but differ in epitope specificity, failed to inhibit the ragweed-induced histamine release. Overall, this bioactivity assay has a low interassay variability (%CV) of 17% (n = 23) and can be readily modified to determine if rhuMAbE25 or other anti-allergy therapeutics are capable of blocking histamine release elicited by other allergens. Moreover, the assay can be used to confirm IgE-mediated allergic responses and to provide early information regarding safety and potential efficacy of therapeutics aimed at blocking IgE dependent responses.

Ling Zhi-8: a novel T cell mitogen induces cytokine production and upregulation of ICAM-1 expression.

Ling Zhi-8 (LZ-8) is a protein purified from Ganoderma lucidium, a Chinese medicinal fungus thought to possess potent effects on the immune system. When examined for its effects on lymphocytes, LZ-8 exhibited potent mitogenic effects on human peripheral blood lymphocytes (PBL), inducing a bell-shaped dose-response curve similar to that caused by PHA and other lectin mitogens. Fractionation experiments indicated that the proliferative response in the PBL cultures was primarily due to T cells, but was monocyte dependent. Stimulation of PBL with LZ-8 resulted in the production of IL-2 and a corresponding upregulation of IL-2 receptor expression. In addition to T cell proliferation, microscopic examination of LZ-8-stimulated PBL revealed that LZ-8 induced cellular aggregate formation. The aggregate formation correlated with a dramatic rise in ICAM-1 expression and an increased production of IFN-gamma, TNF alpha, and IL-1 beta, molecules associated with regulation of ICAM-1 expression. Both the aggregate formation and the proliferative effects of LZ-8 were blocked by addition of monoclonal antibody to either CD18 or CD11a, the counterreceptor complex components for ICAM-1. Furthermore, addition of neutralizing antibodies to both IL-2 receptor and TNF alpha blocked aggregate formation, cellular proliferation, and ICAM-1 expression. These findings demonstrate that LZ-8 is a potent T cell activator, mediating its effects via cytokine regulation of integrin expression.