The role of mucosal immunity in development of an acquired immunodeficiency syndrome (AIDS) vaccine: workshop summary.

As the AIDS pandemic spreads, the importance of developing effective vaccines against the human immunodeficiency virus (HIV) assumes increasing importance. Since prevention of any disease is a preferred goal, extensive efforts are being devoted to development of an effective vaccine capable of preventing HIV infection and/or disease. Although many investigators are studying the systemic immune response to HIV, relatively little is known about the mucosal immune response to HIV. A workshop was held to identify the basic research issues in mucosal immunity which need to be addressed in order to rationally design an effective vaccine against HIV. This summary emphasizes the salient points of the papers presented and identifies the unanswered questions.

Immunohistochemical localization of histamine-stimulated increases in cyclic GMP in guinea pig lung.

A significant number of asthmatic subjects are provoked by allergic reactions. The underlying pathophysiologic event is mast cell degranulation with the release and generation of the mediators of anaphylaxis. Histamine, one of the major mast cell mediators, causes 10- to 50-fold increases in guinea pig lung cyclic 3',5'-guanosine monophosphate (cyclic GMP) through H1 receptor stimulation. Employing monoclonal antibodies directed at cyclic GMP, immunocytochemical techniques were used to identify those specific cells in lung responding to histamine stimulation with increases in cyclic GMP. The most responsive cells were alveolar and parenchymal macrophages, pleural lining cells, and endothelial and epithelial cells. Little or no increases in bronchial or vascular smooth muscle cyclic GMP was noted. At the height of the reaction, a generalized increase in cyclic GMP staining of all alveolar cells was observed. These findings suggest that the lining cells of the lung including macrophages, mesothelial, endothelial, and epithelial cells may be the most responsive cells to histamine released during allergic responses. The absence of muscular staining suggests that cyclic GMP does not participate in histamine-stimulated muscle contraction.

Production of monoclonal cyclic GMP and cyclic AMP antisera.

In order to facilitate the in situ localization of cyclic nucleotides, a large supply of high-titer anti-sera for immunohistologic analyses would be valuable. Therefore, monoclonal antibodies (Mab) directed at 2'-0-succinyl cyclic GMP (s-cGMP) or 2'-0-succinyl cyclic AMP (s-cAMP) were generated. Immunized mice developed polyclonal antibodies of high titer to either cyclic nucleotide as reflected in an enzyme-linked immunosorbent assay (ELISA) employed to monitor these anti-sera. With the use of standard hybridoma technology and ELISA to monitor anti-cyclic nucleotide antibody production from positive clones, several Mab-producing clones were grown to large volume in tissue culture and ascites fluid. The anti-cGMP and anti-cAMP anti-sera, which demonstrated significant ELISA titers at greater than 1:2,000,000 dilutions, are monospecific and can be employed for radioimmunoassays, ELISA, or immunohistologic localization of cyclic nucleotides in situ.

Histamine H-1 receptors on rat peritoneal mast cells.

In order to characterize the receptor subtype involved in histamine stimulation of increased cyclic AMP levels in rat mast cells with consequent impairment of anaphylactically induced mediator release, the binding of the H-1 receptor antagonist [3H]pyrilamine to mast cells was examined. Pyrilamine bound rapidly, in a saturable and reversible fashion, and with increased binding at 4 degrees C as compared with 21 degrees C and 37 degrees C. [3H]Pyrilamine binding was displaced by H-1 antagonists (tripelennamine greater than pyrilamine greater than or equal to diphenhydramine) greater than histamine greater than the H-2 antagonist, cimetidine. H-1 agonists displaced pyrilamine binding less efficiently than histamine but better than H-2 agonists. Rat mast cells have a single homogeneous population of low affinity (KD = 222 +/- 33 nM) H-1 receptors with a Bmax of 9.7 +/- 2.3 pm/10(6) mast cells and 5.4 +/- 0.92 x 10(6) binding sites per mast cell. Thus, the mast cell has an H-1 type histamine receptor which is probably involved in histamine-induced cyclic AMP increases.