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Biomedical subjects

T B Nutman

Publications and source records attributed to T B Nutman.

At least 73 records · Page 4Linked to original sources
PubMed1996

In utero exposure to Onchocerca volvulus: relationship to subsequent infection intensity and cellular immune responsiveness.

Afro-Ecuadorian individuals from an area where Onchocerca volvulus is hyperendemic have been monitored for infection over the past 16 years. To determine whether in utero exposure to O. volvulus biases a child's subsequent immune responses, children (9 to 16 years old) for whom the mother's infection status was known were chosen for study. Children of infected mothers (n = 19) had significantly higher levels of skin microfilariae than children of uninfected mothers (n = 13; P = 0.021). While the serum levels of O. volvulus-specific immunoglobulin G (IgG), IgG subclasses, and IgE showed no significant differences between the two groups of children, peripheral blood mononuclear cells of children of infected mothers produced higher levels of Th2-type cytokines to several parasite antigens and lower levels of Th1-type cytokines to nonparasite antigens than those of children of uninfected mothers. Thus, in utero exposure to O. volvulus has a long-term effect on the child's subsequent cellular immune response that may render the child more susceptible to O. volvulus infection postnatally.

Adolescent↗
PubMed1996

A polymerase chain reaction assay for detection of the parasite Wuchereria bancrofti in human blood samples.

To identify Wuchereria bancrofti DNA sequences that could be used as the basis for a simple and rapid parasite detection assay, a genomic library of W. bancrofti was constructed and screened for highly repeated DNA. The repeat found with the highest copy number was 195 basepairs (bps) long, 77% AT, and 300 copies per haploid genome. This sequence was designated the Ssp I repeat because it has a unique recognition site for that restriction endonuclease in all or most of the repeat copies. The Ssp I repeat DNA family is dispersed, genus-specific, and exists in all of the different geographic isolates of W. bancrofti tested. Based on DNA sequence analysis of this repeat, we have developed an assay to detect very small quantities of W. bancrofti DNA using the polymerase chain reaction (PCR). With this PCR assay, the Ssp I repeat was detected in as little as 1 pg of w. bancrofti genomic DNA (about 1% of the DNA in one microfilaria) added to 100 microliters of human blood. The PCR assay also amplified Ssp I repeat DNA from geographic isolates of W. bancrofti from around the world but not from other species of filariae or from human or mosquito DNA. Microfilaria-positive human blood samples collected in Mauke, Cook Islands were shown to be Ssp I PCR-positive, while microfilaria-negative samples were PCR-negative. The specificity and sensitivity of the Ssp I PCR assay indicates that this approach has significant potential for improved screening of large human populations for active W. bancrofti infection.

Animals↗
PubMed1996

A major allergen of lymphatic filarial nematodes is a parasite homolog of the gamma-glutamyl transpeptidase.

BACKGROUND: Bm2325, a major IgE-inducing antigen of the filarial parasite Brugia malayi has been implicated in the pathology of tropical pulmonary eosinophilia (TPE), a pulmonary syndrome thought to result from hypersensitivity to microfilariae. MATERIALS AND METHODS: Affinity-purified IgE to Bm2325 from patients with TPE was used to identify a complementary DNA (cDNA) from a B. malayi expression library. Sequence analysis of the cDNA revealed a hitherto unknown parasite protein. Immunoblotting of the recombinant filarial protein using sera of patients with TPE determined its IgE-binding capacity. Reactivity to human lung epithelial cell proteins was analyzed using murine anti-Bm2325 antibodies and serum from patients with TPE. RESULTS: The predicted protein is a homolog of the entire precursor of the gamma-glutamyl transpeptidase (gamma-GT), a key enzyme in the synthesis and degradation of glutathione. The filarial precursor encodes both the heavy (H) and the light (L) chain subunits and shares structural similarities with the mammalian enzymes. The Bm2325 allergen was identified as the homolog of the enzyme light chain subunit. Murine antibodies against the recombinant parasite gamma-GT cross-reacted with the human enzyme present in human airway epithelial cells, and human gamma-GT is a target of antibodies present in the serum of patients with TPE. CONCLUSION: Molecular mimicry between the parasite gamma-GT homolog and the host membrane-bound gamma-GT present in lung epithelial cells likely contributes to the pathogenesis observed in tropical pulmonary eosinophilia.

Amino Acid Sequence↗
PubMed1995

Differential regulation of alternative 3' splicing of epsilon messenger RNA variants.

Alternative 3' splicing of the one active human epsilon heavy chain gene results in variants of epsilon mRNA encoding distinct IgE proteins. The same relative amounts of these epsilon mRNA variants were produced by non-atopic donor B cells when driven in a variety of T-dependent or T-independent systems. The most abundant variants were those for classic secreted epsilon a novel secreted form (CH4-M2"). In contrast, cells from subjects with high levels of serum IgE secondary to parasitic infection or atopy spontaneously produced higher relative levels of the CH4-M2' epsilon mRNA variant, lower relative amounts of both the membrane and CH4-M2" secreted variants, and very low levels of the CH4'-CH5 variant. The existence of and corresponding changes in levels of the CH4-M2'-encoded secreted protein were demonstrated. IL-10 induced this same differential expression of epsilon splice variants in vitro when used to costimulate IL-4 plus CD40-driven B cells and could differentially enhance the production of CH4-M2' protein by established IgE-secreting cell lines. Inhibition of IgE by cross-linking the low affinity IgE receptor (CD23) decreased the levels of epsilon mRNA and resulted in a distinct pattern of epsilon mRNA characterized by a dramatic decrease in CH4-M2' splice variant. IL-6, IL-2, or IFN-gamma did not change the epsilon mRNA pattern. Overall, the absolute and relative amounts of the different epsilon mRNA splice variants produced appear to be controlled in a differentiation-related fashion.

Adult↗
PubMed1995

Interferon-gamma in the management of infectious diseases.

Interferon-gamma has pleiotropic adjuvant effects on host defenses. These effects have made interferon-gamma particularly useful for enhancing host defenses in patients with chronic granulomatous disease of childhood and thus for reducing the incidence of life-threatening infections in these patients. Increasingly, data suggest that interferon-gamma will be useful for treating infections characterized by intracellular persistence in macrophages, such as toxoplasmosis, leishmaniasis, and mycobacteriosis. Interferon-gamma is emerging as an important cytokine for use in the treatment of infectious diseases.

Amino Acid Sequence↗
PubMed1995

Identification of recombinant filarial proteins capable of inducing polyclonal and antigen-specific IgE and IgG4 antibodies.

Filarial infection is characterized by an immune response associated with the production of Ag-specific IgG4 and IgE and IL-4 and IL-5. To identify filarial Ags capable of inducing such responses and to analyze the role Ags themselves play in sustaining it, 24 recombinant filarial parasite proteins were screened for their ability to be recognized by sera from 67 individuals with tissue-invasive filarial infections. Among the recombinant proteins that were recognized by IgG4 or IgE Abs in 25% of the sera or more, two were selected on the basis of their ability to elicit polyclonal and Ag-specific IgE/IgG4 Abs in vitro. Ov27 (analogous to Ov7/cystatin, a cysteine protease inhibitor) and OvD5B (analogous to Ov33, an aspartyl protease inhibitor) induced both a polyclonal and Ag-specific IgE/IgG4 response that was blocked by neutralizing Abs to IL-4 and to IL-13 or by soluble IL-4 receptors. Recombinant human IFN-gamma and IL-12 also led to a decrease in the production of polyclonal and Ag-specific IgE/IgG4 Abs. In addition, these two recombinant proteins preferentially stimulated the secretion of IL-4, IL-5, and IL-10 (in contrast to IFN-gamma). The data suggest that certain epitopes on filarial Ags preferentially elicit a Th2-type response and provide an in vitro model for dissecting the mechanisms underlying this preferential response.

Animals↗
PubMed1995

Flow cytometric analysis for cytokine production identifies T helper 1, T helper 2, and T helper 0 cells within the human CD4+CD27- lymphocyte subpopulation.

Using three-color flow cytometric analysis for the detection of intracellular cytokines, we have been able to determine the exact combination of cytokines produced by individual T lymphocytes. Because CD4+CD27- lymphocytes have been shown to produce more IL-4 and IL-5 than CD4+CD27+ lymphocytes, cells from normal individuals (n = 4) and helminth-infected patients (n = 4) were sorted magnetically for the CD4+CD27+ and the CD4+CD27- subpopulations. Intracellular staining for IL-4, IL-5, and IFN-gamma subsequent to mitogen stimulation for 6 h revealed that although almost no CD4+CD27- lymphocytes produce both IL-5 and IFN-gamma (0.03-1.4%), a distinct proportion produce both IL-4 and IFN-gamma (0.1-8.0%), and 66% to 84% of IL-5-producing cells also produce IL-4. Patients and normal individuals had the same functional T cell subsets, but the CD4+CD27- lymphocytes from patients had higher frequencies of cells producing IL-4 (geometric mean (GM), 24.3% vs 16.4%) or IL-5 (GM, 10.2% vs 2.9%), whereas those of normal individuals had higher frequencies of cells producing IFN-gamma (GM, 44.5% vs 17.2%; p = 0.043). These analyses also revealed that the CD4+CD27- population included significantly higher frequencies of cells that were IL-5+IFN-gamma- (GM, 4.9% vs 1.5%; p = 0.025), IL-4+IFN-gamma- (GM, 13.8% vs 3.5%; p = 0.025), and IFN-gamma+IL-4-IL-5- (GM, 27.3% vs 12.0%; p = 0.011) than the CD4+CD27+ population. Thus, we have clearly demonstrated Th1, Th2, and Th0 cell subsets within the CD4+-CD27- population of human lymphocytes.

Antibodies, Monoclonal↗
PubMed1995

Migration of a novel DQA1* allele (DQA1*0502) from African origin to North and South America.

A PCR-based strategy termed DHDA has recently been developed which reveals DQA1 and DQB1 allelic polymorphism through gel retardation following electrophoresis. This HLA-typing strategy improves the efficiency of identifying previously undetected DNA sequence polymorphisms. DHDA has been utilized to perform DQA1 genotypic analysis in non-Caucasian populations and has resulted in the identification of a novel allele, DQA1*0502 (designated by the WHO nomenclature committee). This new allele has been found in Africans and South and North Americans of black racial ancestry and is geographically consistent with the African diaspora during the 15th-19th centuries. DQA1*0502 represents a single C-to-G transversion in codon 59 (exon 2) and results in an amino acid change from proline to arginine. Although MHC genes are highly polymorphic, this DQA1*0502 substitution is unique, as it represents an amino acid change at a position assessed previously to be conserved in the human DQ alpha polypeptides.

Africa↗
PubMed1995

Immunity to onchocerciasis: putative immune persons produce a Th1-like response to Onchocerca volvulus.

Immunity to Onchocerca volvulus (Ov) infection is suggested by the presence of putatively immune (PI) subjects in a region of Ecuador in which Ov is endemic. PI subjects were identified by traditional diagnostic methods combined with a polymerase chain reaction-based assay for Ov DNA in skin snips. Responses of peripheral blood mononuclear cells (PBMC) from the PI group (n = 16) were compared with those of persons with active infection (microfiladermic [MF] subjects; n = 51). PBMC of PI subjects proliferated significantly more to Ov antigen (OvAg; P < .009) than did PBMC of MF persons but less to streptolysin-O (P < .001). Cytokine analysis of PBMC culture supernatants revealed that PI subjects (n = 11) produced significantly more interferon-gamma to OvAg than did those in the MF group (n = 18; P = .018), less interleukin (IL)-5 to nonparasite antigen (P = .003) and mitogen (P = .012), and less IL-10 spontaneously (P = .016). Thus, immunity to Ov may in part be mediated by an antigen-specific Th1-type response.

Adolescent↗
PubMed1995

Resistance to Onchocerca volvulus: differential cellular and humoral responses to a recombinant antigen, OvMBP20/11.

Persons putatively immune (PI) to Onchocerca volvulus (Ov) infection were identified in Ecuador on the basis of epidemiologic, clinical, and parasitologic findings. Immune responses of PI subjects to a recombinant onchocercal protein, OvMBP20/11, were determined and compared with those of a comparable infected (INF) group from the same Ov-endemic area. PI subjects had significantly less antibody reactivity to this molecule; however, not all INF subjects had an antibody response. IgG1 and IgG4 were the predominant IgG subclasses induced to this molecule, and the amount of IgG1 produced was the only significant difference between the PI and INF groups. In contrast to the antibody responses, proliferative responses to OvMBP20/11 were significantly higher in PI than in INF subjects. Cytokine analysis of peripheral blood mononuclear cell culture supernatants revealed that INF subjects produced significantly more interleukin-10 in response to OvMBP20/11 than did PI subjects. This antigen induced few other cytokines, and there were no differences between study groups.

Animals↗
PubMed1995

Isotype-specific characterization of antibody responses to Onchocerca volvulus in putatively immune individuals.

Isotype/subclass-specific antibody responses to adult Onchocerca volvulus extract (OvAg) were assessed by both ELISA and immunoblotting for a group of putatively immune individuals (PIs, n = 29) from a hyperendemic area in Ecuador and for a group of infected individuals (INFs, n = 470) from the same regions. As a group, the PIs have been previously shown to possess lower levels of OvAg specific IgG1, IgG2, IgG3 and IgG4 than INF's but semi-quantitative analysis revealed that the relative proportions of these subclasses differs between the two groups. The IgG of the PI group contained a higher proportion of IgG3 and a lower proportion of IgG4 than the INF group. The frequency distribution of IgG3 responses was similar for the PI and INF groups. The frequency distributions for IgG1, IgG4 and IgE were significantly different between the PI and INF groups. A subgroup of the PIs were identified from frequency distributions and multivariate plots of individual isotype responses as having antibody responses (mainly IgG4) possibly indicative of cryptic infection. High IgE responses were exclusive to INF individuals, and a rare response type of high IgG3 with negligible levels of other isotypes/subclasses was seen only in the PI group. However, the majority of the PIs had negligible responses for all antibody classes. Immunoblots demonstrated no obvious differences in qualitative recognition between the PIs and INFs.

Adult↗
PubMed1995

Immunoregulation in human lymphatic filariasis: the role of interleukin 10.

In humans with lymphatic filariasis microfilaremia is associated with a parasite antigen-specific hyporesponsiveness when assessed by cell proliferation and secretion of interleukin-2 and interferon-gamma. Hyporesponsiveness in these individuals is not only parasite antigen-specific but appears to be limited to Th1-type responses. Th2 mediated responses such as IL-5 secretion and IgE antibody production to parasite antigens are generally strong and usually no different than those seen in immunologically more reactive amicrofilaremic individuals with chronic lymphatic pathology. The mechanisms by which Th1 responses are inhibited have not yet been elucidated, but some studies suggest that down-regulatory cytokines such as IL-10 may be involved in this process. Mononuclear cells from microfilaremic individuals have been found to secrete greater quantities of IL-10 spontaneously and in response to parasite antigens. In this review, mechanisms by which IL-10 may be induced by the parasite and the mode by which IL-10 may regulate parasite antigen-specific Th1 responses in these individuals are discussed.

Elephantiasis, Filarial↗
PubMed1995

Immunoglobulin kappa chain allotypes (KM) in onchocerciasis.

GM and KM allotypes, powerful tools for genetic characterization of human populations, have been shown to play an important role in genetic predisposition to some infectious diseases. Two diverse racial groups--Afro-Ecuadorians and Amerindians--living in a single restricted geographical area of Ecuador, appear to have different risk factors for acquisition and clinical expression of onchocerciasis, a disease caused by the filarial parasite Onchocerca volvulus. In this study, GM and KM allotypes were determined in 25 Afro-Ecuadorians and 24 Amerindians infected with Onchocerca volvulus (INF) and in putative immune individuals (PI). In Afro-Ecuadorians, the frequency of the homozygous KM 3 phenotype was significantly decreased in INF as compared with the PI group (20 vs. 68%; P= 0.0012), while the frequency of the heterozygous KM 1,3 phenotype was increased in INF as compared with the PI subjects (48 vs. 9%; P= 0.0044). These results suggest that in Afro-Ecuadorians KM 3 is associated with a lower relative risk (resistance), whereas KM 1,3 is associated with an increased risk (susceptibility) of onchocerciasis.

Africa↗
PubMed1995

Technical report. Optimizing probe selection in directed heteroduplex analysis using HDprobe 1.1.

Directed heteroduplex analysis (DHDA) has proven to be a powerful technique for rapid geotyping in human populations. This strategy should also have widespread utility in differentiating closely related organisms of medical and public health importance through identification of DNA sequence polymorphisms. Identifying an optimal probe sequence for use in DHDA has required empirical testing of both the positive and negative strands of a number of potential probes. To identify optimal probes more efficiently, a computer program has been developed that predicts the number of potential stable and unstable mismatches between a probe and its target sequences in DHDA. This information can then be used to predict--from among a group of potential probes--which one will be the most successful in differentiating closely related homologues of a targeted gene sequence. This approach was tested on a number of probe and target sequences derived from the mitochondrial NADH dehydrogenase subunit 4 gene of the West African black fly, Simulium damnosum sensu lato. The number of unstable mismatches predicted to occur in a given heteroduplex by the computer program was found to be important in differentiating closely related species. Therefore, this strategy is useful in identifying informative probes in the development of new DHDA-based assays.

Animals↗
PubMed1994

Costimulation by purified intercellular adhesion molecule 1 and lymphocyte function-associated antigen 3 induces distinct proliferation, cytokine and cell surface antigen profiles in human "naive" and "memory" CD4+ T cells.

Activation of resting human CD4+ "naive" (CD45RA+CD45RO-) and "memory" (CD45RA-CD45RO+) T cells requires costimulatory signals in addition to engagement of the T cell receptor/CD3 complex (TCR/CD3). The adhesion pathways mediated by lymphocyte function-associated antigen 1/intercellular adhesion molecule 1 (LFA-1/ICAM-1) and CD2/LFA-3 are capable of providing such costimulatory signals. Our work shows that these costimulatory adhesion pathways are critically involved in regulation of T cell differentiation/maturation. Evidence for subset-specific costimulatory requirements is demonstrated by the finding that only memory CD4+ T cells were costimulated by LFA-3, whereas both naive and memory CD4+ T cells were costimulated by ICAM-1. In addition, these costimulatory adhesion pathways regulated reciprocal cytokine secretion patterns for interleukin 5 (IL-5) and granulocyte/macrophage colony-stimulating factor (GM-CSF). Repeated costimulation of CD4+ memory T cells with LFA-3 led to secretion of high levels of IL-5, while repeated costimulation with ICAM-1 induced high levels of secreted GM-CSF. Significant interferon gamma (IFN-gamma) production was observed with either of the costimulatory ligands. Extensive cell surface analysis of these in vitro cultures of peripheral blood derived memory CD4+ T cells, with monoclonal antibodies obtained from the 5th Leucocyte Typing Workshop, revealed differential expression of a singular antigen, CD60. This antigen was preferentially expressed on LFA-3-costimulated cells suggesting a positive correlation between CD60 expression and a T helper type 2-like cytokine profile. In conclusion, this report demonstrates a new functional role for costimulatory adhesion molecules in regulating differential cytokine secretion in human memory CD4+ T cells.

Antibodies, Monoclonal↗
PubMed1994

CD45RB expression defines two interconvertible subsets of human CD4+ T cells with memory function.

Reciprocal expression of CD45RA and CD45RO in human CD4+ T cells defines populations understood to be naive cells (CD45RA+CD45RO-) and memory cells (CD45RA-CD45RO+). We investigate two subsets of CD45RA-CD45RO+ CD4+ human T cells which differ by fourfold in their expression of the CD45RB isoform; one is CD45RBbright and the other is CD45RBintermediate. In contrast, CD45RA+ naive cells are all CD45RBbright. Both subsets of CD45RA- cells proliferate in response to recall antigens so we designate them MEM 1 (CD45RO+RBbright) and MEM 2 (CD45RO+RBintermediate). CD45RA and CD45RB expression are regulated independently during in vitro activation of naive cells. When MEM 1 cells are activated they tend to down-regulate CD45RB expression, whereas activated MEM 2 cells tend to up-regulate CD45RB expression. Thus, in contrast to the stability of the CD45RA-CD45RO+ phenotype, the MEM 1 and MEM 2 phenotypes are labile and may interconvert. MEM 1 and MEM 2 cells produced comparable amounts of interleukin(IL)-2, IL-4, and IL-5 though MEM 1 cells produced slightly more interferon(IFN)-gamma (mean 1.7-fold more). MEM 1 cells consistently proliferated more (mean 2.3-fold more) than MEM 2 cells early during in vitro activation. Thus, differential expression of CD45RB within CD45RA- cells defines two subsets that have similar properties except for somewhat greater IFN-gamma production and proliferative responses by MEM 1 cells. Variability in CD45RB expression may represent a mechanism for fine-tuning the responsiveness of memory cells in vivo.

CD4-Positive T-Lymphocytes↗