No abstract

The treatment of asthma and allergic rhinitis using unique, humanized anti-IgE monoclonal antibodies with very particular binding specificities is now supported by the results of multiple phase II and III human clinical studies. The therapeutic efficacy of this approach is attributable to several pharmacological mechanisms. In addition to the expected effects of these monoclonal antibodies in neutralizing free IgE and inhibiting IgE production by B cells, several indirect biochemical and cellular effects have been uncovered during the course of the clinical trials. These include the accumulation of potentially beneficial IgE-anti-IgE immune complexes and the downregulation of the high-affinity IgE Fc receptors (FcvarepsilonRI) on basophils and mast cells. This article analyzes the structural basis of the specificity of the anti-IgE antibodies and pertinent results from in vitro experiments, animal model studies, and human clinical trials in an attempt to provide a cogent pharmacological interpretation of the therapeutic effects of anti-IgE therapy in both the near- and long term. The development of anti-IgE therapy over the past 10 years provides an interesting example of the emergence of a conceptually new, biotechnology-produced pharmaceutical.

It is generally believed that the gag gene product of human immunodeficiency virus type 1 (HIV-1) is processed into several core proteins by a virus-specific protease. We used deletion mutation analysis to study the role of HIV-specific protease in the processing of core proteins and its requirement for viral infectivity. Several mutant genomes with deletions in the protease gene were constructed. A mammalian cell line, COS-M6, transfected with the wild-type viral genome was shown to produce virions containing processed core proteins, while COS-M6 cells transfected with two mutated genomes could express only the core protein precursor, Pr56gag. The wild-type transfectant produced infectious virus; both transfectants expressing the mutated genomes also produced virions, and one of them still retained reverse transcriptase activity. However, the mutant viral particles were devoid of infectivity. Virions with a distinct central core and an electron-dense nucleoid budded out from the plasma membrane of COS-M6 cells transfected with the wild-type genome. In contrast, noninfectious virions that budded either into cytoplasmic vacuoles or out from the plasma membrane of COS-M6 cells transfected with mutant genomes contained ring-shaped nucleoids. These results indicate that the HIV-1 protease plays a role not only in the maturation of the core proteins but also in the assembly of the virus and thus is required for viral infectivity.

To define the domains in the envelope glycoprotein important for antibody neutralization of the human immunodeficiency virus type 1 (HIV-1), monoclonal antibodies (mAbs) were generated by immunizing mice with purified glycoprotein gpl20 of the MB isolate. One mAb, G3-4, reacted with the gpl20 of homologous ('fB) and heterologous (RF) isolates. In addition, mAb G3-4 efficiently neutralized both