Biomedical subjects

R F Schell

Publications and source records attributed to R F Schell.

At least 55 records · Page 3Linked to original sources

PubMed1993

Induction of interleukin-1 release by high- and low-passage isolates of Borrelia burgdorferi.

Low-passage isolates of Borrelia burgdorferi induced arthritis when injected into the hind paws of irradiated hamsters, while high-passage isolates did not. To examine a possible mechanism for induction of arthritis, peritoneal exudate cells were coincubated with high- and low-passage isolates of B. burgdorferi, and the resultant conditioned medium was assayed for interleukin-1 (IL-1) activity. Comparable amounts of IL-1 activity were detected in culture supernatants generated by high- and low-passage spirochetes and were dependent on the number of spirochetes added. Live B. burgdorferi stimulated greater release of IL-1 activity than did heat-killed organisms. No evidence of release of IL-1 due to shedding of soluble components from spirochetes was obtained. A recombinant human IL-1 receptor antagonist blocked the proliferative activity of conditioned medium in a murine thymocyte assay for IL-1 activity. The greater ability of low-passage spirochetes to survive in vivo may be more important than the ability to induce IL-1 production in the pathogenesis of Lyme arthritis.

Animals↗

PubMed1993

Seroprotective groups among isolates of Borrelia burgdorferi.

We demonstrated that different seroprotective groups exist among isolates of Borrelia burgdorferi and Borrelia garinii. The major group was composed of isolates 297, B31, S-1-10, MMTI, IPT, and ATCC 35211 and 21 isolates obtained from California, Illinois, New York, Texas, and Wisconsin. A second group was composed of European isolates PBi and G25. A third group was composed of a single isolate, C-1-11. These groupings were supported by Western immunoblot findings. In addition, the seroprotective groups were confirmed by passive transfer of immune sera and challenge of recipient hamsters with the homologous isolate or other isolates of B. burgdorferi or B. garinii. These studies demonstrate that a monovalent vaccine will not provide complete protection against infection with all isolates of B. burgdorferi.

Animals↗

PubMed1993

Recovery of Borrelia burgdorferi by filtration.

Bacterial contamination frequently interferes with successful recovery of the Lyme spirochete from cultures of tissue from Borrelia burgdorferi-infected humans, rodents, or ticks. We used 0.20- and 0.45-microns-pore-size syringe-tip filters to recover spirochetes from cultures contaminated with other bacteria. Low concentrations (1 to 10/ml) of B. burgdorferi organisms could be recovered from cultures seeded with 1 x 10(8) to 4 x 10(8) Staphylococcus aureus, Streptococcus faecium, Escherichia coli, or Bacillus subtilis organisms per ml. We also used this technique to recover B. burgdorferi from contaminated environmental and clinical cultures of B. burgdorferi. We conclude the filtration is an efficient method for recovering Lyme spirochetes from contaminated samples and increasing the number of successful isolations of B. burgdorferi.

Bacteria↗

PubMed1992

Performance of 45 laboratories participating in a proficiency testing program for Lyme disease serology.

OBJECTIVE: We show that significant interlaboratory and intralaboratory variations exist in Lyme disease proficiency testing. DESIGN: Six case-defined Lyme serum samples and three serum samples from individuals with no history of Lyme disease were randomized in four shipments and distributed to 45 participating laboratories. RESULTS: Interlaboratory and intralaboratory performances were highly variable. Approximately 4% to 21% of laboratories failed to identify correctly positive serum samples with titers of 512 or more using polyvalent serum or immunoglobulin G conjugates. With lower levels of anti-Borrelia burgdorferi antibody in the serum sample, approximately 55% of participating laboratories did not identify a case-defined serum. There was also a striking inability of many laboratories to reproduce their results on split samples from the same individual. In addition, 2% to 7% of laboratories identified serum samples from individuals with no known exposure to B burgdorferi as positive using polyvalent serum. The false positivity rate increased to 27% with the use of immunoglobulin G conjugate. CONCLUSIONS: Our results indicate that there is an urgent need for standardization of current testing methodologies. Until a national commitment is made, serological testing for Lyme disease will be of questionable value for the diagnosis of the disease.

Antibodies, Bacterial↗

PubMed1992

Evaluation of C. diff.-CUBE test for detection of Clostridium difficile-associated diarrhea.

The toxin B assay was used to evaluate C. diff.-CUBE, a new dot-immunobinding assay (DIA) for the laboratory diagnosis of Clostridium difficile-associated diarrhea. The widely used latex agglutination test was also included for comparison. Stools from 100 patients suspected of having C. difficile-associated diarrhea were tested. The toxin B assay, latex agglutination, and DIA tests were positive for 12%, 9%, and 22% of the specimens, respectively. The sensitivity, specificity, and positive and negative predictive values of the DIA test were 67%, 84%, 36%, and 95%, respectively, compared with the toxin B assay. The specificity (98%) and positive predictive value (78%) for the latex agglutination test were significantly higher than those of the DIA test. Of 13 specimens solely positive by the DIA test, 11 were cultured and none were positive. Clinical assessment supported only two of the 13 positive DIA results. When clinical assessment was included in the analysis, the DIA positive predictive value rose to 45%. Although the sensitivity and negative predictive values of the DIA test are comparable to the latex agglutination test, the low specificity and positive predictive values of the DIA test make it an inappropriate method to use for screening in a population with a low prevalence of true positives.

Bacterial Toxins↗

PubMed1992

Immunoglobulin G2 confers protection against Borrelia burgdorferi infection in LSH hamsters.

We showed that immune serum and its immunoglobulin fractions, specifically immunoglobulin G2 (IgG2), could confer complete protection to irradiated hamsters challenged with the Lyme disease spirochete. Immune serum and its immunoglobulin fractions also killed Borrelia burgdorferi in vitro. Depletion of complement in vivo abrogated the ability of IgG2 to confer complete protection against B. burgdorferi. Furthermore, the majority of antibody reactivity directed against B. burgdorferi was found in the IgG2 fraction. These findings demonstrate that IgG2 plays an important role in acquired resistance against infection with B. burgdorferi. Additional studies are needed to determine the mechanism(s) by which B. burgdorferi evades host defenses despite the development of an effective borreliacidal antibody response.

Animals↗

PubMed1992

Borrelia burgdorferi stimulates release of interleukin-1 activity from bovine peripheral blood monocytes.

Infection with Borrelia burgdorferi is suspected to be a cause of lameness and arthritis in cattle. Interleukin-1 (IL-1) activity has been detected in joint fluids from human patients affected by various arthritides, including Lyme arthritis. In addition, human monocytes and murine macrophages have been reported to release IL-1 activity when incubated with B. burgdorferi in vitro. To address a possible mechanism by which B. burgdorferi might cause a bovine arthritic syndrome, we determined whether bovine peripheral blood monocytes released IL-1 activity when coincubated with B. burgdorferi in vitro. High-passage and low-passage isolates of B. burgdorferi stimulated release of IL-1 activity from bovine monocytes. The amount of IL-1 activity released was dependent on the number of borreliae added to the monocyte cultures. In addition, live and heat-killed B. burgdorferi cells stimulated release of similar amounts of IL-1. We also obtained no evidence that soluble components released from in vitro-cultured B. burgdorferi stimulated IL-1 release from bovine monocytes. A recombinant IL-1 receptor antagonist blocked the proliferative activity of monocyte-conditioned medium in a thymocyte costimulation assay, thus demonstrating that the costimulatory activity detected was due to IL-1.

Adult↗

PubMed1992

Detection of borreliacidal antibodies in hamsters by using flow cytometry.

Flow cytometry can be used to detect antibody that kills Borrelia burgdorferi. Borreliacidal activity was detected within 3 h of incubating B. burgdorferi with immune serum and complement. Right-angle light scatter and propidium iodide fluorescence were the cytometric parameters which correlated best with in vitro killing of B. burgdorferi. Flow cytometry is a rapid method for determining the presence of borreliacidal activity and may lead to a better serodiagnostic test for the detection of Lyme disease.

Animals↗

PubMed1991

Depletion of complement and effects on passive transfer of resistance to infection with Borrelia burgdorferi.

When irradiated hamsters are passively immunized with immune serum before challenge with Borrelia burgdorferi, they are completely protected from arthritis and infection. The complement dependency of this protection was addressed by treating hamsters with cobra venom factor. Depletion of complement abrogated the ability of immune serum obtained 1 and 10 weeks after infection to confer complete protection. By contrast, depletion of complement had no effect on the ability of 3-week immune serum to confer protection. These results suggest that complement-dependent, and possibly complement-independent, antibodies are important for preventing the induction of Lyme arthritis.

Animals↗

PubMed1991

Role of L3T4+ and 38+ T-cell subsets in resistance against infection with Treponema pallidum subsp. pertenue in hamsters.

The protective immunity conferred by T-cell subsets against infection with Treponema pallidum subsp. pertenue was studied. We demonstrated that hamster T cells can be separated into two subsets by monoclonal antibody (MAb) GK 1.5 (anti-L3T4) and MAb 38. Eighty-five percent of hamster thymocytes were L3T4+ and 87% were 38+ cells; 84% were dual positive for MAbs anti-L3T4 and 38. In the peripheral lymph nodes, however, the L3T4+ and 38+ T cells were mutually exclusive according to two-color immunofluorescence analysis. The two T-cell subsets were found to be functionally distinct according to their secretion of interleukin 2 (IL-2) when stimulated with concanavalin A. The L3T4+ cells secreted IL-2 and had characteristics of T helper cells, while the 38+ cells did not secrete IL-2 and appeared to be T cytotoxic-suppressor cells. Transfer of 4 x 10(6) helper or cytotoxic-suppressor T lymphocytes from T. pallidum subsp. pertenue-immune hamsters protected irradiated naive hamsters against challenge with this subspecies. IL-2 production could still be detected in the irradiated recipients 12 days after irradiation of naive recipients, although at a low level. This suggests that the remaining lymph node cells could support the survival and expansion of the infused cytotoxic-suppressor T cells. No accumulation of macrophages was observed in regional lymph nodes of immune T-cell recipients within 10 days of infection. Instead, there was an influx of polymorphonuclear neutrophils in all animals injected with T. pallidum subsp. pertenue. This report demonstrates that hamster T cells can be separated into two phenotypically and functionally distinct subsets and that both T-cell subsets confer protection against challenge with T. pallidum subsp. pertenue.

Animals↗

PubMed1991

Characterization of the protective antibody response to Borrelia burgdorferi in experimentally infected LSH hamsters.

We show that serum obtained from normal hamsters infected with Borrelia burgdorferi can confer complete protection on irradiated recipients challenged with the Lyme spirochete. Borreliacidal activity was detected 7 days after infection, peaked at weeks 3 to 5, and thereafter decreased. Relatively high borreliacidal activity was detected in immune serum at weeks 3 and 5 of infection. The borreliacidal activity did not correlate with antibody used for the serodiagnosis of Lyme disease, which remained elevated throughout experimental infection. Our results also demonstrated that blocking antibody and antigenic variation in B. burgdorferi did not account for the decreasing titer of protective antibody. These findings indicate that protection against reinfection gradually wanes.

Animals↗

PubMed1991

Borreliacidal activity of sera from hamsters infected with the Lyme disease spirochete.

An in vitro borreliacidal assay that accurately reflects the levels of protective antibody determined by passive transfer of immunity studies was developed. Borreliacidal antibody in sera obtained from normal hamsters infected with Borrelia burgdorferi was readily detected. When immune serum containing complement was incubated with B. burgdorferi organisms, spirochetes were killed within 2 h. Treating immune serum with anti-hamster immunoglobulin G abrogated the borreliacidal activity. Killing of B. burgdorferi in serum was detected 1 week after infection; it peaked at week 3 and gradually declined. Relatively high levels of borreliacidal antibody were found, especially in week 3 immune serum, which could be diluted 1,280-fold. The decrease in borreliacidal antibody after infection may account for occurrences of reinfection and the remitting course of Lyme disease.

Animals↗

PubMed1991

Survey for Ixodes spp. and Borrelia burgdorferi in southeastern Wisconsin and northeastern Illinois.

Forested areas adjacent to Milwaukee, Wis., and Chicago, Ill., were investigated for rodents and ticks infected with Borrelia burgdorferi, the causative agent of Lyme disease. White-footed mice (Peromyscus leucopus or Peromyscus maniculatus), meadow voles (Microtus pennsylvanicus), and eastern chipmunks (Tamias striatus) were captured; and specimens from these animals were cultured for B. burgdorferi to define whether the midwestern Lyme disease area currently encompasses these large metropolitan centers. During 1988, B. burgdorferi was successfully cultured from the tissues of two M. pennyslvanicus voles captured from the Chicago area. However, no Ixodes spp. ticks were captured. None of 274 animals captured from sites I3 and 12 additional sites in Wisconsin and Illinois during the summer of 1989 were infected with B. burgdorferi or Ixodes spp. In addition, no ticks were recovered when the underbrush in 11 contiguous areas was flagged. Apparently, B. burgdorferi is rarely found in these areas because of the absence of the appropriate tick vectors. Further studies are needed to monitor the dispersal of B. burgdorferi-infected Ixodes dammini into this heavily populated midwestern region.

Animals↗

PubMed1991

Detection of bacteria in blood by centrifugation and filtration.

Culture of blood is the most frequent means of diagnosing bacteremia. However, conventional blood culturing methods are slow in isolating bacteria. We developed a method for isolation of bacteria by centrifugation and filtration. Fresh human whole blood was inoculated with facultatively anaerobic and aerobic microorganisms (3 to 172 microorganisms per 5 ml). Seeded blood was then mixed with Ficoll-Hypaque (density, 1.149 +/- 0.002 g/ml) and centrifuged (386 x g) for 30 min at ambient temperature. The entire gradient (plasma, leukocytes, and Ficoll-Hypaque) was removed and filtered through a 0.22-micron membrane filter (Millipore). The filters were then placed on chocolate agar plates and incubated at 35 degrees C in a humidified atmosphere containing 5% CO2. For each bacterium tested, approximately 35 to 100% of the viable microorganisms were recovered when compared with control cultures (pour plates of seeded blood). All bacteria produced isolated colonies on filters after overnight incubation (18 h). This procedure may prove to be a more rapid method for isolating bacteria from clinical blood samples than the blood culture bottle technique.

Bacteria↗

PubMed1991

Lyme disease assay which detects killed Borrelia burgdorferi.

We developed an in vitro assay showing that Borrelia burgdorferi organisms were killed by serum from patients with Lyme disease. Twenty of 20 Lyme disease serum samples caused B. burgdorferi killing in a range of 36 to 99% compared with the mean number of viable spirochetes when sera from 10 healthy individuals were used. The percentage of killing of B. burgdorferi increased with convalescent serum from patients with early Lyme disease. The borreliacidal activity was detectable in some sera diluted 640-fold and was abrogated after treatment with anti-human immunoglobulin G. In contrast, pooled or individual normal human serum did not cause a decrease in the number of viable B. burgdorferi. Borreliacidal activity was also not detected in sera from patients with relapsing fever, rocky mountain spotted fever, syphilis, mononucleosis, rheumatoid factor, or DNA antibodies. Our results show that borreliacidal activity can be used as a specific serodiagnostic test for detecting Lyme disease.

Antibodies, Bacterial↗

PubMed1990

Passive immunization prevents induction of Lyme arthritis in LSH hamsters.

We determined that sera obtained from hamsters infected with Borrelia burgdorferi could prevent the induction of Lyme arthritis. When irradiated hamsters were administered immune serum and subsequently challenged with B. burgdorferi, no evidence of infection was detected. Recipients failed to develop swelling of the hind paws, and no histopathologic changes were detected. In addition, B. burgdorferi was not recovered from tissues of hamsters that were passively immunized. By contrast, irradiated hamsters that were administered normal hamster serum or saline and infected with the Lyme spirochete developed arthritis. Extensive histopathologic changes occurred in the hind paws and knee joints, and spirochetes were recovered from most of the tissues examined. These results show that immune serum can confer complete protection on recipient hamsters to challenge with B. burgdorferi.

Animals↗

PubMed1990

Phagocytosis of opsonized Treponema pallidum subsp. pallidum proceeds slowly.

Macrophages were found to phagocytize Treponema pallidum subsp. pallidum attached to polycarbonate filters. This environment simulated the in vivo interaction of surface-adherent treponemes with macrophages. The phagocytosis of T. pallidum subsp. pallidum was found to proceed slowly. Heat-killed T. pallidum subsp. pallidum were susceptible to opsonization with 2% immune serum, whereas live treponemes were resistant to this concentration of antibody. High concentrations of immune serum were found to increase phagocytosis of the spirochetes. Live T. pallidum subsp. pallidum had bound limited quantities of immunoglobulin G in vivo, and only opsonization with 20% immune serum resulted in a detectable increase in surface-bound immunoglobulin in vitro. Kinetic studies suggested a steady rate of phagocytosis that is considerably slower than with other bacteria. Scanning electron microscopy studies of the phagocytizing macrophages showed that the treponemes were detached from the membrane filters and scooped onto the ruffled portion of the macrophage surface. This lengthy physical process, along with the lack of a dramatic increase in ingestion after opsonization, may account for the slow rate of phagocytosis.

Animals↗

PubMed1990

Immune T cells sorted by flow cytometry confer protection against infection with Treponema pallidum subsp. pertenue in hamsters.

The role of cell-mediated immunity against infection with Treponema pallidum subsp. pertenue in humans or experimental animals is unclear. Hamsters injected subcutaneously in the hind paws with 4 x 10(6) unfractionated lymph node cells or enriched lymph node T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters were resistant to challenge with T. pallidum subsp. pertenue. The popliteal lymph nodes of hamsters that received immune cells weighed less and had significantly fewer treponemes than did lymph nodes from hamsters infused with cells from nonimmune donors. Furthermore, recipients of immune T cells failed to develop antitreponemal antibodies 21 days after challenge. Enriched T cells were obtained by flow cytometric separation by using monoclonal anti-Ia antibody 14-4-4s, which identified hamster B cells. Flow cytometric analysis by two-color immunofluorescent staining with anti-hamster-immunoglobulin and monoclonal anti-Ia antibody 14-4-4s confirmed that monoclonal anti-Ia antibody 14-4-4s recognized B cells. In addition, lymph node cells obtained after treatment with anti-Ia monoclonal antibody 14-4-4s and complement were 97% T cells, as determined by monoclonal antibody 20, a hamster T-cell marker. These results demonstrated that highly enriched T cells (immunoglobulin negative, Ia negative) from T. pallidum subsp. pertenue-immune hamsters conferred partial protection on hamsters against infection with T. pallidum subsp. pertenue.

Animals↗