Cystic fibrosis pseudomonas opsonins. Inhibitory nature in an in vitro phagocytic assay.

Abstract

A B S T R A C T Pseudomonas aeruginosa infection plays a primary pathogenetic role in the chronic respiratory tract disease of cystic fibrosis (CF) patients. Despite pronounced humoral immune responses, reflected by high levels of antibodies against Pseudomonas in serum and in sputum, the antibodies do not eliminate this bacterium. In the present study we have used affinity chromatography with a lipopolysaccharide substituted immunoadsorbent gel to isolate high titers (meanCF = 1:256) of immunotype specific Pseudomonas IgG antibodies from the sera of nine CF subjects, and have evaluated the functional ability of these antibodies to promote phagocytosis and intracellular killing of P. aeruginosa in an in vitro human alveolar macrophage culture system.The phagocytic and intracellular bactericidal kinetics revealed that CF IgG antibodies function in an inhibitory fashion. Both the rate of phagocytosis (rateCF = 204 cpm/unit time) and absolute bacterial uptakes maximal at 120 min (uptakecF = The cellular and humoral immune systems in subjects with CF appear to function normally (1, 3-5) with one major exception: whole serum appears to interfere with the phagocytic function of alveolar macrophages (AM). Whole serum from homozygous CF patients inhibits the ability of rabbit and human AM to ingest and destroy Pseudomonas bacteria (6-9). This effect has been variously attributed to a serum deficiency, to a heat-labile factor, or more recently, to a heat-stable inhibitory factor in CF sera (6-9). "Bactericidal blocking" antibodies have been suggested as an explanation for the selective inability of CF whole serum to support Pseudomonas bactericidal activity (10).Optimal phagocytosis of Pseudomonas by polymorphonuclear leukocytes (PMN) or AM requires the presence of heat-stable opsonins (11,12), and of the heat-stable opsonins IgG has superior protective activity when compared with secretory IgA or . Murphy et al. (15) have studied the role of complement in the phagocytosis of Pseudomonas by rabbit AM. These authors concluded that specific antibody is required for efficient phagocytosis but that in the presence of an excess amount of antibody (as in CF) complement was not essential to maximize phagocytosis. Similarly, IgG antibodies in convalescent sera have been shown to augment phagocytosis of Pseudomonas even in the absence ofheat-labile (complement) opsonins (16,17). Because of the importance of immune IgG in the phagocytic process, and special constraints in antibody binding to macrophages imposed by specific cell surface receptors (18), it is likely that such an opsonic antibody deficiency would be in the IgG class.While CF patients have a generous antibody response in serum, sputum, and to a lesser degree, in lung lavage fluid to P. aeruginosa somatic antigens, the functional capacity of these specifically purified antibodies has not been studied directly. To investigate the opsonic, phagocytic, and bactericidal properties of P. aeruginosa lipopolysaccharide type-specific IgG opsonins (Pseudomonas antibodies), w...

Affinity Constants of Naturally Acquired and Vaccine-Induced Anti-Pseudomonas aeruginosa Antibodies in Healthy Adults and Cystic Fibrosis Patients

“…Several possible mechanisms have been proposed to explain the CF opsonic defect. Fick et al [29] have proposed that opsonization is compromised by a weak interaction between antibody and Fe receptors expressed by phagocytic cells. Moss and coworkers [30,31] have noted an altered antibody isotype distribution in CF patients.…”

“…This may be of considerable significance since opsortophagocytic killing ofmucoid and nonmucoid P. aeruginosa is a complement-dependent process [34,35]. Previous data suggesting that anti-P. aeruginosa antibodies from CF patients may not interact properly with Fe receptors on phagocytic cells [29] prompted us to investigate the affinity ofanti- aeruginosa and elected to be vaccinated -.. 5 months later (figure 1). Anti-LPS IgG antibody titer did not increase during the first 5 months of colonization, although nonmucoid P. aeruginosawas repeatedly obtained from sputum cultures during this time.…”

Pseudomonas-Infected Cystic Fibrosis Patient Sputum Inhibits the Bactericidal Activity of Normal Human Serum

“…In addition, it will be of interest to determine if this blocking factor can also interfere with the opsonization and/or phagocytosis of P. aeruginosa by alveolar macrophages. Several investigators have previously described such blocking activity in CF sera (2, 3,5,21,23).…”

“…Alveolar macrophages isolated from CF patients appear normal (B), but CF senun appears to interfere with the ability of rabbit and human alveolar macrophes to ingest and destroy Pseudomonas (2, 3,5,21,23). This effect has been attributed to either a serum deficiency (2), or a serum inhibitory factor (3,21,23 In addition to intdering with phagocytais, CF senun has also been found to block scnun bactericidal activity for P. aetuginosa.…”

Effect of Pseudomonas-induced chronic lung inflammation on specific cytotoxic T-cell responses to adenoviral vectors in mice

“…15,16,19 These immune responses are of sufficient importance, even in previously healthy lungs, that a number of strategies to limit these specific responses have been explored [20][21][22][23][24] in attempts to improve Admediated gene transfer and/or transgene expression. Chronic infection and inflammation in the CF lung has been associated with abnormal and exaggerated local and systemic humoral responses to Pseudomonas antigens, [25][26][27] although these responses do not assist the CF host in clearance of this chronic infection. It has been proposed that high concentrations of IL-6 in this environment, a cytokine known to stimulate B-cell differentiation and antibody production, may be partly responsible for this exaggerated response, 18 but this remains speculative.…”