Group A Streptococcal Antibodies in Subjects with or without Rheumatic Fever in Areas with High or Low Incidences of Rheumatic Fever

The levels of streptococcal antibody titers in populations with or without rheumatic fever from an area with a relatively high incidence of rheumatic fever and an area with a low incidence of this disease were compared. Streptococcal antibody titers were determined for two populations, each of which included children without rheumatic fever (nonrheumatic children) and rheumatic fever patients. The two populations were derived from two separate geographic areas, one with a high incidence of rheumatic fever (Grenada) and another with a low incidence of this disease (central Florida). The results revealed an absence of consistent differences in the geometric mean antibody titers between the nonrheumatic subjects and the rheumatic fever patients from Grenada. In the population from Grenada, the mean anti-streptolysin O and anti-DNase B titers were higher in the nonrheumatic controls (P of 0.085 and 0.029, respectively). However, the mean titer of the antibody to the group A streptococcal cell wall carbohydrate was higher in the rheumatic fever patients than in the nonrheumatic controls (P = 0.047). This finding contrasted with the finding that the means of all three streptococcal antibody titers in the patients with rheumatic fever were significantly higher than those in the nonrheumatic subjects from Florida (P = 0.01-<0.001). The reason for this paradoxical finding became evident when the streptococcal antibody titers of the nonrheumatic subjects from Grenada and Florida were compared, revealing significantly higher levels of all three antibodies in the nonrheumatic subjects from Grenada than in the nonrheumatic subjects from Florida (P < 0.001). These results suggest that nonrheumatic individuals in an area with a high incidence of rheumatic fever have inordinately elevated levels of streptococcal antibodies in serum. The presence of elevated streptococcal antibody titers in such a population, which probably reflects a high background prevalence of streptococcal infections, should be taken into consideration when evaluating the role of the group A streptococcus in nonpurulent complications of infections.     

Characteristics of the 19S and 7S response to bacteriophage ΦX174 in the fowl

After intravenous injection of 10¹⁰ plaque forming particles of ØX174 bacteriophage into White Rock fowls, immune elimination began at 30 hours and viable phage was cleared from the circulation by 50–52 hours, the approximate time at which detectable antibody appeared. Little change was noted in the serum neutralizing activity in the interval from 44 to 217 days after injection, at which time the birds were reinjected with ØX174.

Sephadex Peak I (19S globulin) accounted for most of the early activity of the primary response. By Day 9 most of the activity had shifted to Peak II (7S globulin). In the secondary response, the shift had occurred by Day 4. Both 19S and 7S globulin fractions showed an increase in activity when compared to the same days of the primary response, but the 7S increase was proportionately greater.

All sera and serum fractions (whether 19S or 7S) were sensitive to reduction with 2-mercaptoethanol, but became, less sensitive during the course of immunization.

With regard to the production of 19S antibody, White Rock fowls showed a different response to the particulate antigen ØX174 compared with the response to injection of the soluble antigen, bovine serum albumin. There is evidence of immunological memory in the 19S response to ØX174.

     

Listeria monocytogenes Cell Walls Induce Decreased Resistance to Infection

A significant decrease in murine resistance to Listeria monocytogenes was induced by using crude Listeria cell wall fraction (LCWF) and purified Listeria cell walls (PF). When equal amounts of these materials were injected, PF was more effective than LCWF in decreasing resistance. The PF effect was dose dependent when measured either as a decrease in 50% lethal dose of the Listeria challenge or as a decrease in survival time of the infected mice. PF apparently does not act directly on the Listeria since it (i) did not cause a change in in vitro growth of Listeria and (ii) did not increase the virulence of Listeria passaged in vivo or in vitro. The greatest decrease in resistance was observed when both PF and the Listeria challenge were injected intraperitoneally, which may suggest a localized effect. A decrease in resistance was seen when PF was given as early as 3 days before challenge. There was little or no decrease in resistance when PF was given 2 days after the Listeria challenge. Mice previously immunized with live Listeria were immune to Listeria challenge. However, after PF injection the immune mice showed a decreased resistance which was of the same order of magnitude as that seen in unimmunized mice. The effect of PF seems to be at least partially nonspecific, since a decrease in resistance to Salmonella typhimurium could also be demonstrated in PF-treated mice. Phagocytosis of Listeria both in vivo and in vitro did not appear to be inhibited by PF, although the ability of PF-treated mice to kill Listeria in the peritoneal cavity was inhibited.     

Crosslink formation in porcine valves stabilized by dye-mediated photooxidation

Bovine pericardial and porcine valve materials stabilized by dye-mediated photooxidation have shown potential for bioprosthetic valve use. Previously, in vitro and in vivo stability of these materials was demonstrated through enzymatic, chemical, extraction, rat subcutaneous, and functional challenges. Here, we examine the stability of photooxidized porcine aortic valves through amino acid, crosslink, and hydrothermal isometric tension analysis. Photooxidation reduced intact histidine residues from 17.0 to 0 residues per 1000, indicating the photooxidative alteration of this amino acid. Diphenyl borinic acid-derivitized hydrolyzates of proteins were separated by high-performance liquid chromatography, which identified several amino acid crosslinks that appeared with photooxidation that were absent in untreated controls. Thermal relaxation analysis indicated a significantly higher (p < 0.0002) thermal stability for photooxidized porcine cusps than that of untreated controls, with mean relaxation times for untreated cusps of 14,000 +/- 4650 versus 22,900 +/- 2480 s for photooxidized cusps. In summary, porcine aortic valve tissue treated by dye-mediated photooxidation contains new chemical species and exhibits properties consistent with intermolecular crosslink formation, which explain the increased biostability of this material and its potential for use in bioprosthetic devices.     

Influence of serotype of group B streptococci on C3 degradation.

Serotype III strains of group B streptococci (GBS) are isolated from the majority of young infants with bacteremia or meningitis. We hypothesized that serotype-associated differences in structure of the type-specific capsular polysaccharide or the presence of c protein would influence the extent to which C3 degradation occurs on GBS and that type-specific antibody would alter C3 deposition or degradation patterns. When clinical isolates of GBS representing serotypes Ia, Ib/c, II (with or without c protein) and III were employed with hypogammaglobulinemic serum as an opsonic source, a remarkable similarity was observed in patterns of C3 deposition and degradation for each of the four GBS serotypes and between strains with or without c protein. Both C3b and iC3b were detected by 5 min and throughout a 90-min opsonization interval. Less deposition occurred at 5 min on serotypes Ia and Ib/c than on types II and III GBS. Minimal degradation to C3d or smaller fragments was observed. Type-specific antibody facilitated C3b deposition on GBS and C3b degradation to iC3b early in opsonization. Possibly, accessibility of C3 fragments to neutrophil receptors, rather than the extent to which the surface permits C3 degradation, accounts for differential virulence among GBS serotypes.     

Use of buccal cells collected in mouthwash as a source of DNA for clinical testing

CONTEXT: To maximize the participation rate in population genetic studies, alternatives to invasive whole blood collection are increasing. One such alternative is buccal epithelial cell collection, which, in contrast to venipuncture and finger sticks, is painless. Buccal cells, if collected and purified efficiently, offer an acceptable source for DNA to be used in research and clinical applications. OBJECTIVE: To develop a noninvasive sampling method for collecting cells for routine DNA testing in a clinical laboratory setting. DESIGN: Five factors were used to evaluate several brands of mouthwash: (1) compatibility with the DNA purification chemistry, (2) DNA yield, (3) DNA quality, (4) DNA stability at room temperature, and (5) mouthwash taste. Next, an optimization study was undertaken to maximize DNA yield. Finally, a validation study was undertaken with the optimized protocol to test a panel of 14 donors for DNA yield and performance and to test for the stability of DNA held in mouthwash. SETTING: Industrial research and development laboratory. RESULTS: Of 5 mouthwashes tested, Scope brand mouthwash received the highest overall ranking. The addition of proteinase K and glycogen to the protocol significantly enhanced DNA yields, with a test panel (n = 14) giving a range of 12 to 60 microg of DNA per donor. In a 4-week room temperature stability study, the DNA in mouthwash samples was found to be stable for at least 2 weeks. CONCLUSION: A clinically validated DNA purification chemistry was adapted to a noninvasive specimen collection method. This method used a commercially available mouthwash, Scope, to collect buccal epithelial cells for the preparation of high-quality DNA in high yield.     

Outer membrane and porin characteristics of Serratia marcescens grown in vitro and in rat intraperitoneal diffusion chambers.

The composition and antibiotic permeability barrier of the outer membrane of Serratia marcescens were assessed in cells grown in vivo and in vitro. Intraperitoneal diffusion chambers implanted in rats were used for the in vivo cultivation of bacteria. Outer membranes isolated from log-phase bacterial cells recovered from these chambers were compared with membranes isolated from cells grown in vitro. Analysis revealed that the suspected 41-kilodalton porin and the OmpA protein were recovered on sodium dodecyl sulfate-polyacrylamide gels in equal quantities. Several high-molecular-weight proteins, thought to be iron starvation induced, appeared in the diffusion chamber-grown cells. The outer membrane permeability barriers to cephaloridine were similar in in vivo- and in vitro-grown cells based on permeability coefficient calculations. The permeability coefficient of cephaloridine in S. marcescens cells (30.3 x 10(-5) to 38.9 x 10(-5) cm s-1) was greater than that obtained for an Escherichia coli strain expressing only porin OmpC but smaller than those obtained for the E. coli wild type and a strain expressing only porin OmpF. Functional characterization of the suspected porin was performed by using the planar lipid bilayer technology. The sodium dodecyl sulfate-0.4 M NaCl-soluble porin from both in vitro- and in vivo-grown cells showed an average single-channel conductance in 1 M KCl of 1.6. A partial amino acid sequence (19 residues) was obtained for the S. marcescens porin. The sequence showed a very high homology to the E. coli OmpC porin. These data identified the S. marcescens outer membrane 41-kilodalton protein as a porin by both functional and amino acid analyses. Also, the methodology used allowed for efficient growth and recovery of diffusion chamber-grown bacterial cells and permitted identification of specific in vivo-induced changes in bacterial cell membrane composition.     

The effects of undernutrition during early life on spatial learning

Recent research has shown that a lengthy period of undernutrition during early postnatal life can cause alterations in the morphological structure of the dentate gyrus. As this region is involved in the control of spatial memory, we decided to investigate whether undernourished rats also showed any deficits in this aspect of behaviour. Rats were undernourished from about birth until either 30 or 60 days of age and then nutritionally rehabilitated for a lengthy period before testing. There were significant differences in the body weight of control and undernourished rats in each experiment. The testing procedure involved rats being placed in a large pool of opaque water. They were required to swim to find a hidden platform located just below the water surface onto which they could escape. Each rat had to perform this test 20 times over a period of 3 days. The time taken and the total distance swum by each rat during each trial was measured. In Experiment 1, rats were familiarised with the water before testing took place, whereas in Experiment 2 they were not. There were no significant differences in the latency to find the platform or the distance swum between well-fed control and previously undernourished rats in either experiment. In conclusion, in our experiments we could not demonstrate that undernutrition during early life caused any deficits in spatial memory performance.