Biomedical subjects

L A Mitchell

Publications and source records attributed to L A Mitchell.

At least 55 records · Page 3Linked to original sources

PubMed1993

Chronic rubella vaccine-associated arthropathy.

Rubella immunization or infection is an uncommonly recognized cause of acute, recurrent, or persistent musculoskeletal manifestations. After routine rubella immunization, two women presented with the onset of polyarthralgia, arthritis, maculopapular rash, fever, paresthesia, and malaise with persistent or recurrent manifestations lasting longer than 24 months after vaccination. The patients expressed rubella virus RNA in peripheral-blood leukocytes 10 and 8 months after vaccination, respectively, in contrast to repeated negative results in asymptomatic rubella-immunized controls. One patient developed significantly depressed antibody responses to rubella virus after vaccination and experienced a prolonged clinical improvement after a 3-month course of intravenous immune globulin. The second patient had normal antibody responses to rubella virus and underwent no clinical improvement during or after intravenous immune globulin therapy. Rubella immunization or infection should be considered as additional causative factors in evaluation of acute and continuing musculoskeletal syndromes.

Adult↗

PubMed1993

Selective tolerance to the E1 protein of rubella virus in congenital rubella syndrome.

Rubella virus (RV) infection of the fetus in the first trimester of pregnancy usually results in severe birth defects collectively termed Congenital Rubella Syndrome (CRS) and is frequently associated with prolonged RV persistence in the infant. Immunological tolerance to RV is believed to contribute to viral persistence, but the mechanism for this is unknown. In this study, RV-specific antibody responses in CRS patients and healthy controls who had experienced Rubella infection postnatally were compared to determine if there were differences that might account for RV persistence in the former group. Levels and functional affinities of IgG specific for individual RV proteins (E1, E2, and C) were measured by enzyme immunoassay (EIA). Relative amounts of RV protein-specific IgG directed to linear and topographic epitopes were compared by immunoblots run under reducing or nonreducing conditions, respectively, and biological activity was determined by hemagglutination inhibition (HAI) assay. Results showed that both CRS patients and control subjects had comparably high levels of IgG directed to whole RV and to RV E2 and C proteins as measured by EIA. However, in contrast to the controls, CRS patients were found to have significantly reduced levels of antibodies directed to RV E1 protein and its linear (but not topographic) epitopes. Also, functional affinities of specific IgG directed to whole RV and E1 protein, as well as hemagglutination inhibition titers, were found to be significantly lower in CRS patients than in controls. The data suggest that intrauterine exposure to RV may result in selective immunological tolerance to the RV E1 protein. A model is presented that accommodates the serological findings of this investigation within a proposed mechanism of RV persistence resulting from selective immunological tolerance to RV E1 protein.

Antibodies, Viral↗

PubMed1993

Identification of immunoreactive regions of rubella virus E1 and E2 envelope proteins by using synthetic peptides.

Relatively large (16-33 aa) synthetic peptides (SPs) representing defined sequences of rubella virus (RV) E1 and E2 envelope proteins were used in lymphocyte stimulation and enzyme immunoassays to map immunoreactive regions recognized by peripheral blood mononuclear cells (PBMNC) and serum antibodies from healthy RV-seropositive, RV-seronegative, and RV-vaccinated adults. Five distinct immunoreactive regions were identified in RV E1 protein, spanning residues (11-39), (154-179), (199-239), (226-277), and (389-412), which stimulated cellular responses in 29-83% of the subjects tested. Two SPs, E1(213-239) and E1(258-277) containing previously-identified virus neutralizing antibody domains, reacted with serum antibodies and also stimulated lymphoproliferation suggesting that these E1 sequences contain linked or overlapping B-and T-cell antigenic sites. The frequency and magnitude of cellular responses to E2 SPs were somewhat lower. SPs encompassing E2 residues (50-72), (140-199), and (244-263) stimulated lymphocyte responses in 28-64% of the subjects tested, while to a lesser degree, SPs within residues (1-36) were also stimulatory. E2 SPs within the regions (1-36), (151-170), and (244-263) also showed low levels of antibody reactivity with sera from RV-seropositive subjects. E2(244-263) which induced the highest level of response among the E2 SPs tested, was of interest due to previous reports of sequence homology of this RV region with human myelin and its potential immunopathogenic role in demyelinating autoimmune diseases. Identification of these potentially immunodominant regions of RV envelope proteins is an important first step in the rational design of new RV vaccines.

Adult↗

PubMed1993

Immunogenicity of Haemophilus influenzae type b conjugate vaccine in children with congenital asplenia.

The immunogenicity of Haemophilus influenzae type b polysaccharide-protein conjugate vaccines in congenitally asplenic children is unknown. The short-term immunogenicity of the H. influenzae type b polysaccharide-diphtheria toxoid conjugate vaccine was therefore assessed in 10 children with congenital asplenia by measuring antipolyribosyl-ribitol phosphate antibody titers. An excellent antibody response was seen in 9 children (mean geometric titer in responders after immunization 44.7 micrograms/mL; range, 2.59-402). The remaining child responded to a booster dose. Further studies are required to assess whether H. influenzae type b conjugate vaccines are immunogenic in infancy in the presence of congenital asplenia.

Adolescent↗

PubMed1993

Cellular hyperimmunoreactivity to rubella virus synthetic peptides in chronic rubella associated arthritis.

OBJECTIVES: Immune recognition of the major structural proteins of rubella virus by peripheral blood mononuclear cells and synovial inflammatory infiltrates of a patient with documented chronic rubella associated arthritis was compared with responses of normal healthy rubella virus immunoreactive subjects to establish if there were unusual response patterns associated with rubella associated arthritis in this subject. METHODS: Synthetic peptides (16-33 amino acids in length) representing selected amino acid sequences of the rubella virus envelope (E1 and E2) and capsid (C) proteins were used in lymphocyte stimulation assays with peripheral blood mononuclear cells or synovial inflammatory infiltrates to determine T lymphocyte recognition of antigenic sites within the synthetic peptides. A rubella virus specific polymerase chain reaction was used to determine the persistence of rubella virus in the patient's cells. RESULTS: The patient's peripheral blood mononuclear cells showed abnormally increased lymphoproliferative responses to three E1 synthetic peptides encompassing residues 219-234, 389-411, and 462-481, and one E2 synthetic peptide containing the sequence 50-72, of which the last three were predicted to contain T cell antigenic sites. Although the patient's peripheral blood mononuclear cells showed positive proliferative responses to C synthetic peptides, these were not unusual. The number of synthetic peptides within the E1, E2, and C panels recognised by the patient's peripheral blood mononuclear cells was greater than was previously observed in normal healthy subjects. The recognition of synthetic peptides by synovial inflammatory infiltrates was similar to peripheral blood mononuclear cells but the responses measured were lower. The polymerase chain reaction was negative for rubella virus detection in peripheral blood mononuclear cells and synovial inflammatory infiltrates. CONCLUSIONS: Abnormally increased T cell recognition of antigenic sites within rubella virus E1 and E2 proteins observed in this patient with rubella associated arthritis suggests chronic antigenaemia due to persistent rubella virus in tissue sites other than peripheral blood mononuclear cells or synovial inflammatory infiltrates.

Aged↗

PubMed1992

Quantitation of human IgG subclass antibodies to Haemophilus influenzae type b capsular polysaccharide. Results of an international collaborative study using enzyme immunoassay methodology.

An international collaborative study was conducted at ten sites to examine the performance of enzyme immunoassays (EIAs) for the quantitation of IgG1, IgG2, IgG3, IgG4 and total IgG anti-Haemophilus influenzae type b (Hib) capsular polysaccharide in human serum. All groups used the same reagents: microtiter plates coated with polyribosylribitol phosphate (PRP) conjugated to poly-L-lysine (PLL), reference, control and test human sera, biotin-conjugated International Union of Immunological Societies (IUIS)-documented monoclonal anti-human IgG1-4 and IgG Pan detection antibodies, avidin-peroxidase and TMB substrate. Initial mixing of soluble PRP antigen or an equal volume of buffer with the 20 test sera prior to analysis confirmed PRP antigen specificity in all five EIAs with greater than 80% competitive inhibition at most sites. Positive correlation between the total IgG anti-Hib and sum of IgG1-4 anti-Hib was demonstrated (r2 = 0.99, Y = 1.13X -0.15). Good agreement was shown between the total IgG anti-Hib as measured by EIA and the total Hib-specific antibodies measured by the current radiolabeled antigen binding assay (r2 = 0.97, Y = 4.6X -5.8). Assay parallelism was demonstrated with an average interdilutional %CV of 22% and parallel dose-response curve slopes. The interdilutional %CVs were calculated as an average per sample of the variation of microgram/ml (corrected for dilution) at different dilutions per laboratory for all participating sites. The interlaboratory variation was the only performance parameter studied that exceeded the target level of 35% CV in all IgG1-4 and total IgG anti-Hib assays. IgG subclass distributions in the test sera demonstrated a predominance of IgG1 anti-Hib in the pediatric serum pools and IgG2 anti-Hib in the adult sera, with low but detectable levels of IgG3 and IgG4 anti-Hib in each group.

Adult↗

PubMed1992

Differential IgG avidity to rubella virus structural proteins.

Avidity maturation of IgG antibody responses directed against the structural proteins of rubella virus (E1, E2, and C) as well as whole rubella virus (RV) was assessed at sequential time intervals in 7 individuals following serologically confirmed wild rubella infection. Individual structural proteins were purified from tissue culture supernatants by differential centrifugation, followed by preparative SDS-PAGE under non-reducing conditions. Avidity of IgG anti-rubella responses was measured by using the 8 M urea elution technique and results expressed as an elution ratio [ER(%)]. A low mean ER(%) of 23% was determined for E1-specific IgG responses during the 10-20 day period following onset of clinical rubella, with subsequent maturation of avidity ER(%) values to 52%, 75%, and 84% at 3 months, 1 year, and 2 years, respectively, post-rubella. In contrast, IgG anti-E2 responses showed minimal avidity maturation with ER(%) values of 20%, 29%, 30%, and 31% over the same time intervals. Similarly, responses to the capsid protein (C) remained at low avidity ER(%) values of 21%, 29%, 36%, and 35% over the 2 year follow-up period. The avidity maturation values for IgG directed against whole RV preparations paralleled observations for E1-specific responses with ER(%) values of 23%, 52%, 85%, and 87%, respectively. These data support the need to assess individual protein-specific antibody avidities in order to more fully understand viral-specific immune responses.

Antibodies, Viral↗

PubMed1992

Case report: CT and MRI of the cauda equina syndrome in ankylosing spondylitis.

The clinical and radiological findings in a patient with long-standing ankylosing spondylitis who developed the clinical features of a cauda equina syndrome are presented. CT and MRI revealed characteristic expansion of the lumbar spinal canal with scalloping of the laminae and spinous processes related to the presence of dorsal dural diverticulae. MRI permitted confident exclusion of other intradural pathology without recourse to invasive investigations.

Cauda Equina↗

PubMed1992

Genetic influences upon eosinophilia and resistance in mice infected with Trichinella spiralis.

Genetic influences upon host variation in eosinophilia and resistance to helminth infection, and the relationship between these parameters, were investigated in 7 inbred and 1 hybrid strains of mice infected with Trichinella spiralis. Clear strain-dependent variations were observed in the maximum peripheral blood, bone marrow and spleen eosinophilia attained in infected animals. SWR, NIH and SJL strains of mice all gave high responses to infection; four congenic strains sharing the B10 background (C57BL10 [B10], B10.S, B10.G and B10.BR) were low responders. Some of the genes for high responsiveness appeared to be dominant, as F1 hybrids from high- and low-response phenotype parental strains showed intermediate to high responses to infection. Intestinal eosinophilia showed no correlation with either peripheral blood or bone marrow responses (NIH and B10 strains having similar levels of eosinophil response in gut tissue) and was unrelated to the level of resistance to infection. Whereas NIH were highly resistant, with adult worm burdens at 13 days post-infection and muscle larval burdens at 35 days post-infection significantly lower than all other strains, B10 were quite susceptible, retaining substantial worm burdens at day 13 and harbouring large numbers of muscle larvae. Measurements of the level of the eosinophilopoietic cytokine IL-5 in sera during infection showed that the two strains differed in the kinetics of release but not in their absolute capacity to produce this cytokine. NIH mice released high levels during a primary infection, B10 released high levels during a secondary infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Differential antibody responses to rubella virus infection in males and females.

Specificities of human rubella virus (RV)-specific IgG, IgM, and IgA antibodies for RV structural proteins (envelope E1 and E2 and capsid) and an E1 domain represented by a synthetic peptide (BCH-178) were determined by immunoblot and ELISA techniques in sera from rubella-infected individuals. Sequential sera were obtained from 67 females and 32 males during acute and convalescent infection phases. Males and females had differences in all antibody classes, especially during the early acute infection phase. At no time during follow-up were IgA anti-E2 antibodies detected in males, in contrast to the case in females. Significantly lower levels of IgG antibody directed to E2 were also observed in males. Males had earlier onset of E1-specific IgG and IgM antibodies with a greater proportion of total RV antibody response directed to E1 (IgG) or E1 peptide (IgM). These differences suggest there are hormonal and genetic influences on immune recognition of RV proteins that may be related to the increased incidence of rubella-associated arthropathy in females.

Adolescent↗

PubMed1992

Detection of rubella virus-specific immunoglobulin G (IgG), IgM, and IgA antibodies by immunoblot assays.

Immunoblot (IB) assays were developed for detection of rubella virus (RV)-specific immunoglobulin G (IgG), IgM, and IgA antibodies in human serum following natural infection or immunization. IB assays performed under nonreducing conditions were compared with those performed under reducing conditions and with immunoprecipitation assays. Significant loss of antigenicity (greater than 90%) of RV E1 and E2 proteins was observed when IB assays were performed in the presence of 2-mercaptoethanol as compared with assays under nonreducing conditions. In contrast, the antigenicity of RV capsid protein was not influenced by reducing agents. Sensitivity of IB for RV-specific IgG antibodies was determined to be 0.01 IU/ml under nonreducing conditions. In the determination of RV-specific IgM and IgA antibodies by IB, pretreatment of serum with protein G to remove competing high-affinity RV-specific IgG or rheumatoid factor significantly improved assay sensitivity. IB assays were observed to be superior to immunoprecipitation assays in their ability to better define the specificities of RV-specific antibodies and to detect antibodies of all immunoglobulin classes. However, the conformational sensitivity of RV protein antigenicity should be an important consideration in the interpretation of RV-specific antibodies by IB assays.

Adult↗

PubMed1992

Characterization of rubella virus-specific antibody responses by using a new synthetic peptide-based enzyme-linked immunosorbent assay.

Rubella virus (RV)-specific immunoglobulin G antibodies were studied by enzyme-linked immunosorbent assay (ELISA) techniques in sera from RV (RA 27/3)-vaccinated individuals, patients experiencing natural RV infection, congenital rubella syndrome patients, and individuals failing to respond to repeated RV immunization. Results obtained by using whole-RV ELISAs (detergent-solubilized M33 strain or intact Gilchrist strain) and hemagglutination inhibition (HAI) and neutralization (NT) assays were compared with results obtained with the same sera by using ELISAs employing a synthetic peptide, BCH-178, representing a putative neutralization domain on the RV E1 protein. Murine RV E1-specific monoclonal antibodies with HAI and NT activities exhibited strong reactivity in ELISAs with BCH-178 peptide. In sera from RA 27/3-vaccinated individuals collected at 0 (prevaccine), 1, 2, 3, 4, 5, 6, 12, and 24 to 52 weeks postvaccine, the development of E1-peptide-reactive antibodies closely paralleled increases in RV-specific antibodies measured by whole-RV ELISAs and HAI and NT assays. Similarly, sequential serum samples obtained from patients during acute and convalescent phases of natural RV infection showed a coordinate increase in RV-specific antibodies as measured by whole-RV and peptide ELISAs. Conversely, congenital rubella syndrome patient sera, although exhibiting high levels of antibody in whole-RV ELISAs, had little or no antibody directed to the neutralization domain peptide. Sera from patients failing to respond to repeated RV immunization contained very low levels of RV-specific antibody in all ELISAs. Our results that the sequence represented by BCH-178 peptide may be a previously unidentified neutralization epitope for human antibodies on the RV E1 protein and may prove useful in determining effective RV immunity.

Adolescent↗

PubMed1992

Sequential follow up observations of a patient with rubella associated persistent arthritis.

In 1985 a patient was described whose persistent polyarthritis was found to be aetiologically linked to rubella virus infection through the detection of repeated maximal synovial lymphocyte proliferative responses to rubella virus antigen and by isolation of rubella virus from her synovium. Follow up over the succeeding seven years has shown continuing chronic polyarthritis and persistent synovial lymphocyte responses to rubella virus antigen with the additional observation that she has a defective humoral immune response against rubella virus.

Adult↗

PubMed1991

Reduction of rubella ELISA background using heat denatured sample buffer.

During the analysis of rubella-specific antibodies in sera from adult vaccinees, it was observed that the inclusion of heat-denatured blocking proteins in the sample dilution buffer substantially reduced non-specific binding of serum IgG to microtitre plates. Results suggest that this modification to standard ELISA technique may reduce the incidence of false positive results in these assays.

Bacterial Proteins↗

PubMed1991

A Chevron-Akin double osteotomy for correction of hallux valgus.

Chevron osteotomy of the distal metatarsal combined with Akin osteotomy of the proximal phalanx is described for treatment of painful hallux valgus. Sixteen patients (24 feet) who underwent the Chevron-Akin osteotomy were retrospectively reviewed by questionnaire, physical examination, and comparison of preoperative and postoperative standing X-rays. After a mean follow-up of 29 months, there was 95% satisfaction with regard to pain relief and appearance of the foot. Good postoperative range of motion of the great toe was recorded subjectively and objectively. Mean improvement of the first intermetatarsal angle was 4.1 degrees (P = 0.05). The average preoperative hallux valgus angle was 27 degrees (range 13-40 degrees). Mean improvement with the double osteotomy was 14.3 degrees (P = 0.05). There was no significant shortening of the first ray with the double osteotomy. Degenerative changes of the first metatarsophalangeal joint were seen in two feet with intra-articular extension of the Akin osteotomy. One malunion occurred with shifting of the Chevron osteotomy after pin removal. The Chevron-Akin osteotomy compares favorably with the isolated distal Chevron osteotomy. In this series there was no compromise of joint motion, and a superior correction of the hallux valgus deformity was obtained.

Adult↗

PubMed1990

Genetic influences upon eosinophilia and resistance in mice infected with Mesocestoides corti.

The genetic influences upon host variation in eosinophilia and resistance to helminth infection, and the relationship between these parameters, was investigated in 9 inbred and 3 hybrid strains of mice infected with Mesocestoides corti. Blood, bone marrow, spleen and peritoneal fluid eosinophilia were far higher in SJL mice than in any other inbred strain. SWR, NIH, C3H and BALB/c mice were high responders to M. corti whereas CBA and 3 congenic strains sharing the B10 background (C57BL/10, B10.S, B10.G) were low responders. Some of the genes for high eosinophil responsiveness appeared to be dominant, as F1 hybrids from high and low response parental strains were intermediate to high in response to infection. SJL and NIH strains were highly susceptible to infection with M. corti, larval burdens at 21 days after infection with 100 tetrathyridia being considerably higher (greater than 1000) than all other strains. BALB/c (congruent to 700 larvae) were designated susceptible, SWR (greater than 400 larvae) were resistant and the B10 congenics (less than 400 larvae) were highly resistant. Genes influencing resistance also appeared to be dominant, as F1 hybrids between resistant and susceptible parental strains were intermediate to resistant on infection. The overall response patterns indicate a direct correlation between susceptibility to infection and high eosinophil responsiveness, but this relationship is not consistent in all strains.

Animals↗

PubMed1989

Effect of cancer plasma on skeletal muscle metabolism.

Circulating factors produced by the macrophages mediate skeletal muscle proteolysis in sepsis and trauma. This study was done to determine whether cytokines affect skeletal muscle metabolism in cancer. Using a method initially developed to measure proteolytic factors in sepsis and trauma, plasma from cachectic cancer patients, noncachectic cancer patients, and normal controls was tested for effects on normal rat skeletal muscle (soleus, extensor digitorum longus). The experimental design allows concomitant measurement of protein synthesis, by [14C]phenylalanine uptake, and protein degradation, by tyrosine release. Plasma from cancer patients caused no acceleration of protein degradation. Noncachectic cancer plasma acted synergistically with insulin to increase protein synthesis (P less than 0.05). These results indicate that a growth factor is present in the plasma of cancer patients who have not become cachexic. To our knowledge, this is the first documentation of a cancer plasma growth factor acting at the organ level to induce synthesis. Our data refute the theory that cancer cachexia is mediated by circulating proteolytic factors. In a separate experiment, purified human recombinant tumor necrosis factor (rTNF) was incubated with normal rat skeletal muscle. No changes were seen in synthesis or degradation rates. Skeletal muscle proteolysis does not appear to be directly induced by rTNF.

Animals↗

PubMed1989

Genetic control of eosinophilia. Analysis of production and response to eosinophil-differentiating factor in strains of mice infected with Trichinella spiralis.

Bone marrow cultures were established from mice undergoing parasitic eosinophilia after infection with Trichinella spiralis. In the presence of eosinophil-differentiation factor (EDF/IL-5) eosinophil precursor cells differentiated and could be identified and counted after a 7-day in vitro culture period. The EDF-bone marrow assay system was used to determine differences in bone marrow eosinophil precursor capacity between a number of inbred strains of mice. Bone marrow cultures from high peripheral eosinophil-response phenotype strains of mice (NIH, SWR & SJL) contained significantly greater numbers of eosinophil precursor cells than the low response strain C57BL/10. All congenic strains of mice with the B10 background, i.e. C57BL/10, B10.S, B10.BR and B10.G were found to have low eosinophil precursor capacity. Bone marrow cultures obtained from F1 hybrids (NIH x C57/BL10, SJL x C57/BL10 and SWR x C57BL/10) demonstrated high precursor numbers, indicating that low responsiveness is inherited as a recessive characteristic. When spleen cells from T. spiralis-infected, high and low responder strains of mice were stimulated in vitro with concanavalin A (Con A) or with parasite antigen, it was found that low responder phenotype strains produced quantities of two eosinophilopoietic lymphokines EDF and IL3, which were similar to, if not greater than high responder strains. This suggests that bone marrow precursor capacity and not T cell lymphokine release is an important limiting factor in determining strain-dependent eosinophilia.

Animals↗