In vitro responses of guinea pig peritoneal macrophages to Legionella pneumophila.

Transmission and scanning electron microscopy were used to study the phagocytosis of virulent and avirulent strains of Legionella pneumophila. The interaction between L. pneumophila and peritoneal macrophages from normal guinea pigs or from animals that had survived infection was studied. The virulent strains survived and proliferated within the phagocyte after ingestion by either type of macrophage, whereas the avirulent strain of bacteria was killed by normal macrophages. Although the addition of immune serum enhanced phagocytosis, the outcome was the same as with normal serum.

Mechanisms of protective immunogenicity of microbial vaccines: effects of cyclophosphamide pretreatment in Venezuelan encephalitis, Q fever and tularaemia.

Administration of high-dose (250 mg/kg) cyclophosphamide (CY) to guinea-pigs and mice 3 days prior to immunization with inactivated vaccine derived from Venezuelan encephalitis virus (VE), Coxiella burnetii and Francisella tularensis resulted in accentuated and prolonged delayed-type hypersensitivity (DTH) and in vitro cellular immunity (CMI) to specific antigen. Humoral antibody were either absent or significantly lower in CY-pretreated animals compared to immunized non-pretreated controls. CY pretreatments precluded protection in the VE virus model, suggesting that resistance is related to antibody. In the Q fever model, the protective immunogenicity of vaccine was preserved or increased by CY pretreatment suggesting that cell-mediated immunity is the important factor. In the tularaemia bacterial system, there was a complex effect of CY pretreatment on the low-grade protection afforded by killed vaccine against virulent infection. These findings suggest that the inability of killed vaccines to induce high-grade resistance against tularaemia and Q fever may be due in part to a suppressive B cell response which is eliminated by CY. These studies have given useful information on the relative significance of components of the specific immune response and may lead to an increased understanding of the mechanisms of action of vaccines and adjuvants.

In vitro interaction between normal cynolmolgus monkey alveolar macrophages and Legionnaires disease bacteria.

The interaction between normal cynomolgus monkey alveolar macrophages and Legionnaires disease bacteria was studied by transmission electron microscopy. After ingestion of Legionnaires disease bacteria, the organisms replicated within macrophages and destroyed the phagocytic cell.

Immunologic protection against the Legionnaires' disease bacterium in the AKR/J mouse.

Female AKR/J mice were challenged with the Washington strain of Legionnaires' disease (LD) bacteria. Nonimmunized mice inoculate intraperitoneally with 2 x 10(8) colony forming units became ill within 4 h and died within 24 h. Progressive histopathologic changes initiated as early as 2 h after inoculation involved the lymphoid organs, the crypts of the small intestine, and the liver. Necrosis with minimal inflammatory cell reaction was the primary lesion. Immunization with a soluble LD bacterial antigen failed to prevent illness but protected against death and development of abnormal histologic changes.

Sequential changes in the concentration of specific serum proteins during typhoid fever infection in man.

An automated immunoprecipitin system has been utilized to quantitate the concentration of 10 specific proteins in the plasma of man. Values obtained by this technique are in agreement with the published concentrations for these specific plasma proteins. This technique was utilized to determine the sequential change s in 10 individual plasma proteins of volunteers exposed to Salmonella typhi. In those volunteers who developed typical typhoid fever, plasma concentrations of the acute phase proteins, alpha1-acid glycoprotein, alpha1-antitrypsin, and haptoglobin, as well as C3 complement were significantly increased with the onset of febrile illness. In contrast, the concentration of plasma albumin and tranferrin were depressed while plasma IgM became elevated during early convalescence from this infection. No significant changes were observed in the plasma concentrations of alpha2-macroglobulin, IgG, or IgA. In the exposed volunteers who did not become ill, the only significant change was a brief depression of alpha1-antitrypsin. During typhoid fever the patterns of change for individual plasma acute-phase globulins were different from those reported for patients with hepatitis, myocaridal infarction, or surgery.

Immunogenicity of formaldehyde-inactivated enterotoxins A and C1 of Staphylococcus aureus.

Quantitative precipitation of antisera specific for native enterotoxin revealed that 70% and 60%, respectively, of the antigenic determinants of enterotoxins A and C1 of Staphylococcus aureus were inactivated by formaldehyde at pH 5.0 or 7.5 contained large polymers (excluded by Sepharose 2B) and induced strong humoral immune responses in rhesus monkeys. Enterotoxin A inactivated at pH 5.0 or 7.5 was composed mostly of small polymers (excluded by Sephadex G-100 but included by Sepharose 2B); it provoked a poor immune response in monkeys (about equivalent to the response obtained with weakly reactive toxin inactivated at alkaline pH). It was concluded that potent enterotoxoids were formed by extensive cross-linking of enterotoxin C1 into large polymers in acidic or neutral formaldehyde solution.

Temporal appearance of opsonizing antibody to Francisella tularensis: detection by a radiometabolic assay.

The burst in oxidative metabolism that is mediated through activation of the hexose monophosphate shunt and accompanies particle ingestion by polymorphonuclear leukocytes was used as the indicator in an in vitro radiometabolic assay for detection of specific opsonizing antibody to Francisella tularensis. Release of 14CO2 from radiolabeled glucose was increased significantly when specific immune serum added to suspensions of monkey polymorphonuclear leukocytes and F. tularensis. With this method, opsonizing antibodies to F. tularensis were detected in monkey serum 3 days after vaccination. Significantly increased opsonic activity in these monkeys preceded the appearance of, and persisted longer than, antibody activity as determined by conventional serological techniques. In addition, sera from 11 of 12 humans that were immunized 1 month to 13 years previously and had nondiagnostic agglutinating antibody titers demonstrated significant opsonizing activity.

Altered immune function in hypercholesterolemic monkeys.

Humoral and cellular immune responses to several antigens were compared in control and hypercholesterolemic groups of monkeys. Chronic hypercholesterolemia, with concomitant hyperphospholipidemia and hypotriglyceridemia, was produced experimentally by feeding monkeys a high-fat, high-cholesterol diet. When studied prior to infection, hypercholesterolemic monkeys exhibited impaired development of precipitating antibodies against ovalbumin, enhanced sensitivity to tuberculin antigen (stimulated apparently by mycobacterial components in complete Freund adjuvant), and an increased rate of clearance of colloidal carbon from blood. During pneumococcal infection the ability of neutrophiles from hypercholesterolemic monkeys to reduce nitroblue tetrazolium dye showed an increase greater than that of control monkeys; both groups exhibited increased but comparable final clearance rates of colloidal carbon, although the increment of increase was smaller in hypercholesterolemic monkeys.