Evaluation of Streptococcus pneumoniae type XIV opsonins by phagocytosis-associated chemiluminescence and a bactericidal assay

The relative roles of serum factors required for opsonization of type XIV Streptococcus pneumoniae were investigated by means of luminol-enhanced chemiluminescence (CL), bactericidal, and immunofluorescence assays employing adult sera containing high (>1,000 ng of antibody nitrogen per ml) or low (<200 ng of antibody nitrogen per ml) antibody concentrations as determined by radioimmunoassay. Specific antibody concentration correlated directly with both total and heat-labile CL activity (P < 0.005) and with the bactericidal index (P < 0.05) at a serum concentration of 10%. The importance of specific antibody as an opsonin was confirmed by the abolition of CL activity and immunoglobulin immunofluorescence observed after absorption of heated sera with type XIV pneumococcal cells and by the dose response in CL and bactericidal activity observed with the addition of immunoglobulin G to hypogammaglobulinemic serum. A role for the classical complement pathway in opsonization was indicated by significantly greater CL integrals for high-antibody sera than for low-antibody sera depleted of factor D and by the bactericidal activity noted for untreated, but not magnesium ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid-chelated low-antibody sera. The alternative pathway contributed more than half of the CL activity of both high- and low-antibody sera. However, after magnesium ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid chelation, only sera with high antibody concentrations or agammaglobulinemic serum reconstituted with immunoglobulin G with high specific antibody levels supported significant bactericidal activity. Therefore, type-specific antibody and complement promote opsonization of type XIV S. pneumoniae, and this may occur via either complement pathway. These results suggest that CL is a suitable tool to delineate serum factors and their contribution to opsonization, but results must be related to other functional assays.

Humoral-phagocyte axis of immune defense in burn patients. Chemoluminigenic probing

Both serum opsonic capacity and granulocyte oxygenation activity were measured in 35 burn patients during their course of therapy. The microbicidal action of granulocytes is effected via the metabolic generation of oxygenating agents; introduction of chemoluminigenic substrates, such as luminol or dimethyl biacridinium dinitrate, allows ultrasensitive measurement of phagocyte oxygenation activity. Serum opsonic capacity can also be assayed by measuring the rate of activation of phagocyte oxygenation activity. Alterations in granulocyte oxygenation activity were observed in individuals patients in temporal association with changes in clinical condition, and sepsis was associated with a marked decrease in activity. An initial depression in opsonic capacity was noted at the time of admission of patients with major burns, more than 40% total body surface. Thereafter, depression of opsonic capacity was temporally associated with sepsis in individual patients. Chemoluminigenic probing provides a rapid, sensitive, and objective method for assessing the status of the humoral-phagocyte axis, and as a clinical laboratory technique is particularly applicable for monitoring patient populations in which sepsis is prevalent.

Functional bacterial opsonic activity of human amniotic fluid

There are some data to suggest that amniotic fluid protects the fetus from invasion by pathogenic bacteria. To examine methods by which amniotic fluid may offer such protection, quantitative antibody, complement activity, and functional opsonic capacity were measured. Immunoglobulins were measured by laser nephelometry and total hemolytic complement was determined by radial diffusion; results suggested activity adequate for bactericidal capacity. The chemiluminescence assay was used to quantitate the functional interaction between polymorphonuclear leukocytes and E. coli, group B streptococci (GBS), or zymosan particles preopsonized with amniotic fluid obtained at different stages of gestation. Results were compared to those for normal serum. Data were analyzed by evaluation of the initial slope, area under the curve, and peak chemiluminescence response. Opsonic activity of amniotic fluid for E. coli and GBS was demonstrated, with E. coli showing greater reactivity (maximum = 15,000 to 25,000 cpm) than GBS (10,000 to 20,000 cpm). Specific, as well as nonspecific, opsonic activity was demonstrated by absorption of amniotic fluid with killed bacteria. Concentration of amniotic fluid did not result in an increase in chemiluminescent activity, which demonstrates that optimal opsonic activity already exists. The classical and alternate pathways of complement were assessed for E. coli and GBS. Preterm amniotic fluid did not differ in response from that of amniotic fluid obtained from term pregnancies. This study demonstrates that amniotic fluid can provide the fetus with protection from bacterial pathogens and delineates mechanisms for such protection.

Humoral immune function and experimental Escherichia coli infection in splenectomized dogs

Intravenous administration of sheep red blood cells resulted in a deficient initial antibody response and provoked a much lower concentration of plaque forming cells in the blood of splenectomized dogs than in the control group. The in vitro serum opsonizing activity on Escherichia coli M-S-15 remained normal after splenectomy, and no difference was found between the test and the control group in the intravascular clearance rate of bacteria injected intravenously.

Pathogenesis of neonatal group B streptococcal infections

Infections of the neonate due to the group B Streptococcus have been recognized since the 1930s, but it was during the 1970s that their incidence grew alarmingly throughout the world. A research effort stimulated by this problem has yielded significant new information about many facets of the pathogenesis of these infections. Immunologic investigations have pinpointed a lack of transplacentally acquired antibody as a significant risk factor. In the laboratory, assays of antibody which have a functional endpoint have demonstrated that the type-specific carbohydrate antigens play a major role in stimulating the development of protective antibody. These assays have been shown to correlate with certain tests of primary antigen-antibody interaction which do not have a functional endpoint, but are simpler to use in larger scale epidemiologic studies. These tools may be useful in filling the gaps in our current knowledge of the pathogenesis of this infection.

Protective efficacy of a modified immune serum globulin in experimental group B streptococcal infection

In spite of aggressive antimicrobial therapy and extensive support measures, the mortality rate in early-onset group B streptococcal infection continues to be exceedingly high. In previous studies, we have demonstrated that passive immunotherapy with fresh whole blood containing opsonic antibody-improved survival in human neonates with group B disease. Transfusion of whole blood, plasma, or other blood products has a number of drawbacks, however. In the present study, we have evaluated immune serum globulin and a preparation of ISG modified for intravenous use for levels of type-specific antibody, opsonic activity, and protective efficacy against type Ia, II, and III group B streptococci. Type-specific antibody was detected in most of the preparations tested. In general, the level in MISG was less than that in the comparison ISG lot. Opsonic activity was also detected in these preparations against the more antibody-sensitive group B strains but was not present for opsonin resistant strains of type Ia, II, and III. Both ISG and MISG provided protection in neonatal rats infected with group B streptococci; in most cases MISG was more efficacious than the ISG from which it was made. These studies suggest that passive immunotherapy with MISG may be a valuable adjunct to current regimens used in the management of early-onset group B disease. This would be especially so if donors could be selected whose serum or plasma contained high levels of opsonic and protective activity against both antibody-sensitive and antibody-resistant group B strains.

Enzyme-linked immunosorbent assay for the quantitation of immunoglobulin G bound to Escherichia coli

Two strains of Escherichia coli were opsonized by incubation in heat-inactivated bovine blood serum and in whey. The opsonized bacteria were then immobilized by complexing with anti-bovine antibodies previously coated to walls of polystyrene tubes. The amount of bovine immunoglobulin (Ig) G in the immobilized complex was then determined by a direct enzyme-linked immunosorbent assay, using peroxidase as enzyme. Thus, a direct measurement of one class of opsonic substances on the surface of the organisms was determined. The sensitivity for measurement of IgG ranged from nanograms to micrograms. After incubation in blood serum, 500-fold more IgG was found on the surface of the serum-resistant strain. The amount of IgG absorbed from whey in each instance was much less than that absorbed from serum. The number of bound molecules per bacterium ranged between 2,000 and 2,000,000, depending on both the strain and the serum.

The effect of partial splenectomy on experimental pneumococcal bacteremia in an animal model

The effect of total and partial splenectomy on the blood stream clearance of type 23B Streptococcus pneumoniae was studied in chinchillas 2 wk and 2 mo following surgery to determine the amount of splenic tissue necessary for protection against overwhelming sepsis. Significantly more pneumococci were found in the blood of totally splenectomized chinchillas than in the blood of sham-operated animals throughout the 6-hr sampling period after intravenous inoculation of pneumococci. Animals that had two-thirds of their spleen removed demonstrated a significant delay in clearance of pneumococci compared with sham-operated and hemisplenectomized animals. The rate of pneumococcal clearance was similar for the sham-operated and the hemisplenectomized group, and was significantly prolonged but similar among totally splenectomized and two-thirds splenectomized animals. Pneumococcal opsonic activity was reduced only in the sera of totally splenectomized chinchillas 2 mo after surgery. There was no positive relationship between pneumococcal clearance and change in pneumococcal opsonic activity. These results suggest that the impaired clearance of circulating pneumococci in splenectomized animals is due to the loss of splenic reticuloendothelial cells as a mechanical filter, rather than deficient serum opsonic activity. There appears to be a critical splenic mass required for optimal bacterial clearance, and hemisplenectomy may protect against overwhelming postsplenectomy sepsis.

Serum antibody and opsonic responses after immunization with pneumococcal vaccine in kidney transplant recipients and controls

We immunized 31 renal transplant patients and 6 control subjects with a pneumococcal vaccine containing 14 capsular polysaccharides. Antibody levels to Streptococcus pneumoniae types 3 and 6A were measured by a radioimmunoassay, and opsonic activity to S. pneumoniae types 3 and 6B was determined by using a luminol-enhanced chemiluminescence phagocytic assay on serum samples obtained before and 1 month after immunization. There was a 10.2-fold and a 2.9-fold increase in antibody to S. pneumoniae type 3 (P less than 0.005) and type 6A (P less than 0.01), respectively, but only a 1.3-fold (P greater than 0.05) and 1.1-fold (P greater than 0.05) increase in opsonic activity. For S. pneumoniae type 3, changes in opsonic activity correlated well with antibody concentration (P less than 0.05). However, for S. pneumoniae type 6, these two tests correlated poorly (P greater than 0.05). This poor correlation suggests that concentrations of antibody to type 6A polysaccharide which are achieved after immunization may not be opsonically active in vitro against S. pneumoniae type 6B.

Epidemiologic studies of Streptococcus pneumoniae in infants: antibody response to nasopharyngeal carriage of types 3, 19, and 23

The relationship between nasopharyngeal carriage of Streptococcus pneumoniae types 3, 19, and 23 and the development of homotypic serum antibody was examined in 17 infants followed prospectively from birth. Serially drawn sera from these children and single serum samples from 18 normal adolescents were assayed for opsonizing antibody using reduction of nitroblue tetrazolium to measure phagocytosis of killed whole pneumococci. Selected sera were also tested for quantitative antibody level by a radioimmunoassay, which correlated quite well with the nitroblue tetrazolium assay. All but one of the adolescents had antibody to type 19, and all 18 had antibody to type 23. None of the 12 infants tested for antibody to type 19 pneumococci showed evidence of an antibody response. Two of 10 infants responded to type 23 pneumococci, as did two of three infants tested to type 3 pneumococci.

Immunocytochemical demonstration of a humoral defense factor in blood cells (Amoebocytes) of the pond snail, Lymnaea stagnalis

Monolayers of blood cells (amoebocytes) and sections of connective tissue and of amoebocyte pellets of the freshwater pulmonate gastropod Lymnaea stagnalis were stained immunocytochemically with antisera to snail agglutinin/opsonin. The presence of this substance was demonstrated light microscopically both in the cytoplasm and on the cell membrane of amoebocytes. This suggests that amoebocytes synthesize agglutinin/opsonin, and bear it at their surface as receptors for foreign materials.

Pulmonary opsonins in Klebsiella pneumoniae pneumonia in rats

Klebsiella pneumoniae was inoculated intrabronchially into rats, and bronchoalveolar lavage fluid and sera were obtained during the ensuring pneumonia. Klebsiellae recovered by lavage were not maximally coated with C3, as judged by studies with fluorescent antibody, whereas the organisms could be coated fully with C3 by a brief incubation in rat serum. The levels of C1 and C3 in lavage fluid obtained during infection were only a small fraction of the levels in the serum, and klebsiellae were not opsonized during incubation with concentrated lavage fluid. Systemic decomplementation did not affect the severity of K. pneumoniae pneumonia, as judged by the measurement of lung weight or by the numbers of klebsiellae in the lungs, but decomplemented rats had a larger number of klebsiellae in the blood at 24 h of infection than did controls. There were fewer klebsiellae in the lungs 4 h after inoculation of preopsonized organisms than after inoculation of organisms which were incubated in control (heat-inactivated) sera. These studies indicate that the concentration of complement and heat-labile opsonins within the alveoli is lower than that in the systemic circulation and is not adequate for effective opsonization of klebsiellae.

Functions of granulocytes after allogeneic bone marrow transplantation

The phagocytosis and intracellular killing by granulocytes as well as the opsonizing capacity of the serum were studied in 13 patients who had undergone allogeneic bone marrow transplantation. Phagocytosis was normal in all patients. A moderately impaired opsonic activity of the serum was found in two patients, who were investigated within 30 days after the transplantation. The intracellular killing was less than control values in two patients. In one patient this was probably due to the existence of a split chimerism.

Complement and opsonins in alveolar secretions and serum of rats with pneumonia due to Streptococcus pneumoniae

Complement appears to have an important role in the early defense against Streptococcus pneumoniae, but the role of complement as a defense mechanism within the lung is not well defined. Complement and heat-labile opsonins in pneumococcal pneumonia were studied by analysis of bronchoalveolar lavage fluid (BALF) of rats inoculated intratracheally with type 3 S. pneumoniae. BALF and serum were obtained at 0, 6, and 24 hr after infection. Leukocyte counts in BALF and histologic studies revealed an acute inflammatory response in the lung at 6 hr; this inflammation progressed for 24 hr. Levels of C1, C2, C3, and alternative pathway activity in pooled, concentrated (20X) BALF of normal and infected rats varied according to the stage of infection and the complement parameter studied, but in all cases the levels were only a small fraction of the levels in serum. Concentrated BALF had measurable levels of pneumococcal heat-labile opsonins, but these were also low as compared with serum levels. A small amount of C3 was detected by immunofluorescence on pneumococci recovered from BALF of infected animals, but these same organisms could be coated much more fully with C3 by brief incubation in serum. The milieu in the lung during bacterial infection is very different from that in serum and may be marginally suitable for effective opsonization of successful pulmonary pathogens such as type 3 S. pneumoniae.

Assessment of Haemophilus influenzae type b opsonins by neutrophil chemiluminescence

A luminol-enhancement chemiluminescence assay and a radiolabeled uptake assay were developed to assess opsonins for Haemophilus influenzae type b. Opsonins in acute and convalescent sera from 17 children with H. influenzae type b meningitis, along with pooled normal human sera, were evaluated and compared with anti-polyribosephosphate antibody concentrations. Five children had a rise in the chemiluminescence-area under the curve for convalescent compared with acute sera. Patient chemiluminescence--area-under-the-curve values were significantly (P less than 0.05) more likely to exceed 50% of normal human serum values if sera contained greater than or equal to 0.1 microgram of anti-polyribosephosphate antibody per ml. Magnesium ethylene glycol tetraacetic acid chelation and heat inactivation of patient and normal human sera significantly (P less than 0.05) reduced chemiluminescence--area-under-the-curve activity. Thus, complement appears to contribute significantly to the opsonization of H. influenzae type b in sera of children. Two of nine children had increases in opsonins as assayed by 3H-labeled H. influenzae type b uptake. After natural systemic H. influenzae type b infection, young children are unable to respond acutely with an increase in anti-polyribosephosphate antibody or serum opsonic activity.

A possible role of Eubacterium and Peptostreptococcus species in the aetiology of Crohn's disease

The faecal flora of patients with Crohn's disease has been found to contain higher numbers of anaerobic gram-negative rods and gram-positive coccoid rods than the flora of healthy subjects. In a considerable percentage of sera from patients with Crohn's disease, agglutinating antibodies were found against four strains of the coccoid rods, in contrast to sera from patients with ulcerative colitis, other diseases and healthy subjects. In the present study, coccoid strains C18, Me46 and Me47 were found to activate complement by the alternative pathway. IgG antibodies to strains Me44, C18 and Me47 had opsonic properties but those to strain Me46 failed to induce phagocytosis. The data suggest an inadequate immune defence against strain Me46 in patients with Crohn's disease. The possible role of strain Me46 in the pathogenesis of Crohn's disease is discussed.

Group B meningococcal opsonins in serum measured by polymorphonuclear leukocyte chemiluminescence

Serum opsonic activity against a strain of group B meningococci was measured by the initial increment in polymorphonuclear leukocyte chemiluminescence. Chemiluminescence was markedly enhanced by serum and was dependent upon both thermostable and thermolabile factors. It was higher in convalescent sera from patients with meningococcal disease than from other patients and normal controls. Absorption of sera with the homologous strain substantially decreased the opsonic activity. Convalescent serum from a patient with group C meningococcal pericarditis showed high opsonic activity towards a group B meningococcal strain. A convalescent serum showed significantly higher activity towards its homologous group B strain than towards another group B meningococcal strain. As measured by chemiluminescence, properties besides group specificity are of importance in opsonization of meningococci. The simplicity and precision of the chemiluminescence measurements seem to offer an improved tool for the study of meningococcal disease immunology.

[Serum opsonic activity in newborns and through the first year of life (author's transl)]

Serum opsonic capacity for "Staph. aureus" was studied in 58 full term infants at birth and through their 1st year of life. The comparison between serum opsonic activity from the infants and their mothers disclosed that infants had a significant decrease of the opsonic activity during the first three months of life. The study of serum levels of C3, C4, IgG and IgM, showed a significant correlation between opsonizationa and low levels of the complement components C3 and C4.

Circulating immunoreactive and bioassayable opsonic plasma fibronectin during experimental tumour growth

Immunoreactive and bioassayable plasma fibronectin (opsonic α(2) surface-binding (SB) glycoprotein) was measured during experimental Sarcoma-180 tumour growth in mice. Male C57BL/6 mice were challenged s.c. with 2 × 10(6) viable Sarcoma-180 tumour cells and evaluated sequentially in parallel with saline-injected controls over a 21-day experimental period. Before challenge, immunoreactive plasma fibronectin was 1050-1150 μg/ml. Minimal tumour growth occurred until 6 days after tumour challenge. There was then a rapid increase in primary tumour size, especially over the 7-14-day interval, with a plateau of growth over the 18-21-day interval. Immunoreactive plasma fibronectin was significantly (P < 0·05) raised at 3 and 7 days after tumour challenge. A rapid rise (P < 0·001) to 2816·6 ± 158·9 μg/ml was observed at 14 days followed by a modest decline at 21 days. Bioassayable opsonic activity increased (P < 0·5) with the rise in immunoreactive fibronectin 3 and 7 days after tumour challenge, but the rapid rise in immunoreactive fibronectin over the 7-14-day interval was associated with a significant (P < 0·5) fall in bioassayable opsonic activity. Thus, the rapid rise in immunoreactive plasma fibronectin parallels the rapid rate of tumour growth, but is associated with a fall in opsonically active plasma fibronectin. Dissociation between immunoreactive and opsonically active plasma fibronectin may be mediated by inhibition and/or alteration of circulating fibronectin during rapid tumour growth. Alternatively, it may reflect increased release of antigenically related protein (i.e. cell-surface fibronectin) during rapid tumour growth, which may have limited biological opsonic activity.