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Biomedical subjects

T B Nutman

Publications and source records attributed to T B Nutman.

At least 55 records · Page 3Linked to original sources
PubMed1997

Degenerate cytotoxic T cell epitopes from P. falciparum restricted by multiple HLA-A and HLA-B supertype alleles.

We recently described human leukocyte antigen (HLA) A2, A3 and B7 supertypes, characterized by largely overlapping peptide-binding specificities and represented in a high percentage of different populations. Here, we identified 17 Plasmodium falciparum peptides capable of binding these supertypes and assessed antigenicity in both vaccinated and naturally exposed populations. Positive cytotoxic T lymphocyte recall and cytokine (interferon-gamma and tumor necrosis factor alpha) responses were detected for all peptides; all were recognized in the context of more than one HLA class I molecule; and at least 12 of the 17 were recognized in the context of all HLA alleles studied. These data validate the concept of HLA supertypes at the biological level, show that highly degenerate peptides are almost always recognized as epitopes, and demonstrate the feasibility of developing a universally effective vaccine by focusing on a limited number of peptide specificities.

Alleles↗
PubMed1997

Elevated IL-10 mRNA expression and downregulation of Th1-type cytokines in microfilaraemic individuals with Wuchereria bancrofti infection.

To understand the molecular basis of parasite-specific anergy in human lymphatic filariasis caused by the nematode Wuchereria bancrofti, parasite antigen-dependent cellular proliferation and cytokine gene expression were investigated. By reverse transcriptase polymerase chain reaction (RT-PCR), the levels of cytokine mRNA were determined in the peripheral blood mononuclear cells (PBMCs) of different clinical groups of filariasis patients. This includes individuals with circulating microfilariae (MF), patients with chronic lymphatic obstruction (CP), and exposed but uninfected individuals (EN). Those with CP exhibited both a Th2 and a Th1 parasite antigen-driven response. In PBMCs from those with MF, there was a marked downregulation of cellular response to parasite antigens, with lowered expression of Th1-specific cytokines (IFN-gamma and IL-2) and this was paralleled by increased IL-10 expression. The EN individuals had a purely Th1-type pattern with absence of IL-4 and IL-5 expression. Further, the mRNA expression of the costimulatory surface marker, CD80 (B7-1), was not associated with either disease status or IL-10 expression. There was a significant negative correlation between IL-10 mRNA expression and PBMC proliferation in the MF individuals, thus indicating the possible role of IL-10 in antigen-specific hyporesponsiveness.

Animals↗
PubMed1997

Regulation of parasite antigen-driven immune responses by interleukin-10 (IL-10) and IL-12 in lymphatic filariasis.

We investigated the mechanisms by which interleukin-10 (IL-10) regulates antigen-specific hyporesponsiveness in asymptomatic microfilaremic (MF) individuals. Peripheral blood mononuclear cells from MF individuals (n = 11) were stimulated in vitro with Brugia malayi antigen (BMA) or mycobacterial purified protein derivative (PPD) in the presence of neutralizing anti-IL-10 or isotype control monoclonal antibodies. As expected, BMA stimulated little or no gamma interferon (IFN-gamma) secretion in MF individuals, whereas PPD stimulated IFN-gamma in all but one. Neutralization of endogenous BMA-driven IL-10 secretion led to augmentation of IFN-gamma in seven of nine MF individuals (1.5- to 10-fold) and did so in a BMA-specific manner (PPD-driven IFN-gamma was augmented in only two of eight MF individuals and only 1.5- to 2-fold), indicating that IL-10 downregulates type 1 responses in these individuals. Type 2 responses (IL-5 secretion) were unaffected by the IL-10 blockade. To assess whether IL-12 could reverse the type 1 downregulation observed, the effect of recombinant human IL-12 (rhIL-12) on BMA-driven IL-5 and IFN-gamma production was also evaluated. rhIL-12 augmented both BMA- and PPD-driven IFN-gamma production 5- to 10-fold in six of nine MF individuals. These data demonstrate that IL-10 downregulates BMA-driven type 1 responses and that IL-12 can overcome downregulation of Th1 responses associated with MF but does so in a non-antigen-specific manner.

Adolescent↗
PubMed1997

Inherited resistance to HIV-1 conferred by an inactivating mutation in CC chemokine receptor 5: studies in populations with contrasting clinical phenotypes, defined racial background, and quantified risk.

BACKGROUND: CC chemokine receptor 5 (CCR5) is a cell entry cofactor for macrophage-tropic isolates of human immunodeficiency virus-1 (HIV-1). Recently, an inactive CCR5 allele (designated here as CCR5-2) was identified that confers resistance to HIV-1 infection in homozygotes and slows the rate of progression to AIDS in heterozygotes. The reports conflict on the effect of heterozygous CCR5-2 on HIV-1 susceptibility, and race and risk levels have not yet been fully analyzed. Here we report our independent identification of CCR5-2 and test its effects on HIV-1 pathogenesis in individuals with contrasting clinical outcomes, defined race, and quantified risk. MATERIALS AND METHODS: Mutant CCR5 alleles were sought by directed heteroduplex analysis of genomic DNA from random blood donors. Genotypic frequencies were then determined in (1) random blood donors from North America, Asia, and Africa; (2) HIV-1+ individuals; and (3) highly exposed-seronegative homosexuals with quantified risk. RESULTS: CCR5-2 was the only mutant allele found. It was common in Caucasians, less common in other North American racial groups, and not detected in West Africans or Tamil Indians. Homozygous CCR5-2 frequencies differed reciprocally in highly exposed-seronegative (4.5%, n = 111) and HIV-1-seropositive (0%, n = 614) Caucasians relative to Caucasian random blood donors (0.8%, n = 387). This difference was highly significant (p < 0.0001). By contrast, heterozygous CCR5-2 frequencies did not differ significantly in the same three groups (21.6, 22.6, and 21.7%, respectively). A 55% increase in the frequency of heterozygous CCR5-2 was observed in both of two cohorts of Caucasian homosexual male, long-term nonprogressors compared with other HIV-1+ Caucasian homosexuals (p = 0.006) and compared with Caucasian random blood donors. Moreover, Kaplan-Meier estimates indicated that CCR5-2 heterozygous seroconvertors had a 52.6% lower risk of developing AIDS than homozygous wild-type seroconvertors. CONCLUSIONS: The data suggest that homozygous CCR5-2 is an HIV-1 resistance factor in Caucasians with complete penetrance, and that heterozygous CCR5-2 slows the rate of disease progression in infected Caucasian homosexuals. Since the majority (approximately 96%) of highly exposed-seronegative individuals tested are not homozygous for CCR5-2, other resistance factors must exist. Since CCR5-2 homozygotes have no obvious clinical problems, CCR5 may be a good target for the development of novel antiretroviral therapy.

Adult↗
PubMed1996

Identification of surface molecules associated with physiologic activation of eosinophils. Application of whole-blood flow cytometry to eosinophils.

Activation is central to the eosinophil's functional role as an immune responder cell. To evaluate such activation in cells freshly isolated from peripheral blood, a method for whole-blood immunostaining and flow cytometry-based eosinophil selection was developed. Simultaneous comparison of purified eosinophils and whole-blood cells revealed significant differences in the levels of expression of various surface molecules, which suggested that the purification process activated the eosinophils. Subsequent analyses were conducted with the whole-blood assay. When eosinophils from helminth-infected persons (n = 18) were compared with those from normal individuals (n = 10), the early activation marker CD69 was found to be significantly increased (geometric mean (GM) = 4.3 vs. 1.0%, p = 0.04). The granulocyte activation marker CD66 was also up-regulated on eosinphils from helminth patients (GM = 53.3 vs. 31.0%, p = 0.044), as was the tetraspan family molecule CD81 (TAPA-1; GM = 79.4 vs. 48.2%, p = 0.02). Conversely, in vivo CD23 (FcepsilonRII) expression on eosinophils was decreased in the presence of parasitic infection (GM = 0.9 vs. 5.7%, p = 0.02). Expression of the eosinophil surface molecules CD69, CD81, and CD23 was significantly enhanced after cytokine stimulation in vitro with IL-3 or GM-CSF. In vivo, specific anthelmintic therapy resulted in decreased CD66 and CD25 expression (p < 0.05 compared with pretreatment) to levels approaching those seen in uninfected normal individuals. These findings indicate the dynamic nature of eosinophil surface molecules and demonstrate an important role for whole-blood staining in developing an understanding of the nature of eosinophil activation and of their role in inflammatory reactions to helminth parasites.

Anthelmintics↗
PubMed1996

Stage-specific induction of cytokines regulates the immune response in lymphatic filariasis.

Parasite stage-specific T cell responses were studied in Indians with lymphatic filariasis manifesting as elephantiasis (CP, n = 11) and asymptomatic microfilaremia (MF, n = 8), using antigens derived from the microfilarial, adult male only, and mixed adult male and female worms. Proliferative responses to microfilarial and mixed (male-female adult worm) antigens in MF individuals were markedly impaired compared to corresponding responses in individuals with CP. In contrast, T cell proliferative responses to adult male-derived antigens were not statistically different between the two groups. Analysis of antigen-driven cytokine secretion by peripheral blood mononuclear cells from MF and CP individuals revealed significantly lower IL-2 and IFN-gamma production by MF in response to microfilarial and mixed antigens (but not to adult male antigen) compared to CP individuals. No differences were observed between MF and CP in parasite antigen-driven IL-4 or IL-5 production. Spontaneous and parasite-specific IL-10 secretion was also measured to determine if cytokine cross-regulation of Th1 responses may be a mechanism underlying the observed Th1 suppression. Spontaneous and microfilarial antigen-driven IL-10 was found to be significantly higher in MF than in CP individuals. These data indicate that MF individuals exhibit preferentially impaired Th1-type responses to microfilarial antigens and that microfilarial-induced IL-10 may be critical in the downregulation of specific Th1 responses.

Adolescent↗
PubMed1996

RANTES in onchocerciasis: changes with ivermectin treatment.

Adverse reactions are seen relatively frequently after treatment of onchocerciasis patients with ivermectin. The chemokines RANTES and IL-8, which have both chemotactic and activation properties for eosinophils and neutrophils, respectively, may have a role in the pathogenesis of post-treatment reactions. Circulating levels of the chemokines and the cytokines tumour necrosis factor-alpha (TNF-alpha) and IL-6 were measured in the plasma of 22 Onchocerca volvulus-infected subjects. Peaks of mean circulating levels of RANTES and TNF-alpha were seen at 6 h after ivermectin administration. Peripheral eosinophil counts declined at 36 h post-treatment and an early peak in RANTES levels was associated with a delay in peripheral eosinopenia. RANTES levels were negatively correlated with severity of rash (P < 0.001) and lymphoedema (P < 0.05), suggesting that high circulating levels of RANTES may inhibit eosinophil sequestration. No changes in circulating levels of IL-8 were seen. These findings suggest a possible role of circulating RANTES in modulating eosinophil sequestration in vivo.

Adolescent↗
PubMed1996

Diethylcarbamazine-induced reversal of early lymphatic dysfunction in a patient with bancroftian filariasis: assessment with use of lymphoscintigraphy.

Exposure of expatriates to the infective larvae of Wuchereria bancrofti can result in the early development of signs of lymphatic obstruction. The findings on the clinical presentation of expatriates are distinct from the chronic pathological findings seen among the native population and are similar to the findings in experimentally infected persons. We report the case of a Peace Corps volunteer who developed acute lymphatic dysfunction within 3 months of arriving in an area that was endemic for filariasis. The diagnosis was established clinically and by demonstrating the presence of antibodies to recombinant proteins specific for patients with lymphatic filariasis. Lymphatic flow was markedly abnormal when assessed with use of 99mTc-lymphoscintigraphy. Treatment with diethylcarbamazine reversed both the physical and lymphoscintigraphic abnormalities.

Adult↗
PubMed1996

High levels of spontaneous and parasite antigen-driven interleukin-10 production are associated with antigen-specific hyporesponsiveness in human lymphatic filariasis.

To determine whether counterregulation by interleukin (IL)-10 plays a role in the generation or maintenance of the antigen-specific hyporesponsiveness seen in asymptomatic microfilaremic (MF) patients, parasite antigen (PAg)- and nonparasite antigen (NPAg)-driven IL-10 production by peripheral blood mononuclear cells (PBMC) was studied in 10 MF patients and in ll patients with chronic lymphatic pathology (CP). PBMC from MF patients spontaneously secreted 10-fold more IL-10 than did PBMC from patients with CP. PAg also induced significantly more IL-10 production by PBMC from CP patients. There was a negative correlation between PAg driven IL-10 production by PBMC and PAg-specific T cell proliferation in the MF group. IL-10 secretion by plastic adherent cells from MF persons was higher in response to PAg than NPAg, whereas IL-6 and tumor necrosis factor-alpha secretion were equivalent for PAg and NPAg, suggesting that PAg preferentially induces IL-10 secretion in these cells. Thus, PAg-induced IL-10 likely plays an important role in down-regulating antigen-specific proliferative responses in MF patients.

Adolescent↗
PubMed1996

Polymerase chain reaction-based assessment after macrofilaricidal therapy in Onchocerca volvulus infection.

A recently developed polymerase chain reaction (PCR)-based assay is significantly more sensitive than current methods for diagnosing Onchocerca volvulus infection, and it overcomes many difficulties in identifying active onchocerciasis. Since chemotherapy is widely used to treat onchocerciasis, the utility of PCR in assessing responses to treatment and in predicting recrudescence is important. Twenty-eight patients who had skin snips positive for microfilariae (Mf) were studied 120 days after receiving amocarzine, when each was negative for Mf: 16 (57%) were positive for O. volvulus DNA in the PCR-based assay. Of these, 14 (88%) were Mf positive when reassessed parasitologically on day 240, and all were Mf positive on day 365. Equally important was the finding that 12 patients had cleared both Mf and Mf DNA; only 1 was Mf positive at day 240. This suggest that the PCR-based assay provides a sensitive means assessing infection status after macrofilaricidal chemotherapy and is an early predictor of persons likely to have a recurrence of Mf.

Animals↗
PubMed1996

Elevations in granulocyte-macrophage colony-stimulating factor and interleukin-5 levels precede posttreatment eosinophilia in onchocerciasis.

The eosinophil survival assay was used to quantitate cytokines in 17 serial serum samples from 10 patients treated for onchocerciasis with diethylcarbamazine. Eosinophils isolated from normal donors were cultured for 4 days in the presence of patients' sera, and cell viability was determined. Serum specimens from 9 of 10 patients enhanced eosinophil survival from 4.8% +/- 2.2% (mean +/- SE) before treatment to 50.0% +/- 6.4% after treatment. Survival enhancement activity peaked before posttreatment eosinophilia. Antibodies to interleukin (IL)-5, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-3 were used to block cytokine activity in 22 serum samples. Antibodies to IL-5 blocked survival in 5 samples, antibodies to GM-CSF blocked survival in 6 samples, and a combination of antibodies to IL-5 and GM-CSF blocked survival in 8 additional samples. Overall, posttreatment sera from patients treated for onchocerciasis enhanced eosinophil survival; both GM-CSF and IL-5 may promote the posttreatment eosinophilia in filarial infection.

Antibodies, Monoclonal↗
PubMed1996

Evaluation of a polymerase chain reaction-based assay for diagnosis of Wuchereria bancrofti infection.

To assess the utility of a polymerase chain reaction (PCR)-based method for diagnosis of Wuchereria bancrofti infection, blood, plasma, and paraffin-embedded tissue samples were tested using a PCR-based assay that detects a W. bancrofti-specific repetitive DNA sequence. The assay was positive in 100 microL of blood from 40 of 42 microfilaria-positive subjects, the 2 subjects with negative assays having microfilarial counts of 1. Samples from 127 uninfected subjects were PCR-negative. The assay was also positive in 7 of 10 daytime samples in regions where infection is nocturnally periodic; PCR amplification from paraffin-embedded sections established the diagnosis of W. bancrofti infection in another 2 cases. A microtiter ELISA plate-based method was developed for rapid evaluation of large numbers of samples. These results suggest that this PCR-based assay will be useful in diagnosis of W. bancrofti infection in a variety of clinical settings.

Adult↗
PubMed1996

Differential regulation of antigen-specific IgG4 and IgE antibodies in response to recombinant filarial proteins.

Having identified two recombinant filarial proteins (Ov27 and OvD5B) that induced patient peripheral blood mononuclear cells to produce antigen-specific IgG4/IgE antibodies in vitro, we assessed the role these filarial antigens play in inducing antigen-specific isotype switching (gamma 4 and epsilon) in the absence of T cells. Purified CD19+ s gamma-/s epsilon- B cells were cultured with either of these antigens in the presence of anti-CD40 mAb and human IL-4. Both antigen and polyclonal signals delivered by IL-4 (or IL-13) were necessary for the induction of specific IgG4/IgE antibodies. To assess the role played by cytokines produced by B lymphocytes in antigen-driven selection of the gamma 4 or epsilon isotype, neutralizing anti-cytokine antibodies were used in vitro. While anti-IL-12 antibodies did not alter the antigen-specific IgG4/IgE production, anti-IL-6, anti-IL-13 and anti-tumor necrosis factor-alpha antibodies significantly inhibited the production of IgG4/IgE. Anti-IL-2 and anti-IL-10 antibodies appeared to down-regulate antigen-specific IgG4 antibodies without affecting antigen-specific IgE antibodies. Although anti-CD21 antibodies had no effect on specific IgE antibodies, they up-regulated specific IgG4 antibodies, a finding paralleled by anti-CD23 antibodies. These data suggest that certain filarial antigen-specific IgG4/IgE responses can be differentially regulated and that certain endogenously produced molecules from B cells-such as IL-2, IL-10, CD23 and CD21-play a significant role in the induction of specific isotypes of antigen-specific antibodies.

Animals↗
PubMed1996

Immunoglobulin G subclass responses of children during infection with Onchocerca volvulus.

To characterize the patterns of immunoglobulin G (IgG) subclass and IgE reactivity during the early stages of onchocerciasis, sera were collected from 224 children (age groups, 2 to 5, 6 to 10, and 11 to 15 years) residing in a region of Sierra Leone where Onchocerca volvulus is endemic, and these samples were tested by enzyme-linked immunosorbent assay for their reactivity to adult antigens (OvAg) and against four recombinant proteins (OV11, OV27, OV29, and OV16). Over 88% of the samples contained detectable levels of anti-OvAg IgG. In samples from microfilaria (MF)-positive children, IgG4 responses were significantly elevated and constituted on average 39, 35 and 28% of the total IgG responses for the age groups of 2 to 5, 6 to 10, and 11 to 15 years, respectively. For MF-negative individuals, the mean contributions of IgG4 to the total IgG response were 11% (2 to 5 years), 27% (6 to 10 years), and 56% (11 to 15 years). OvAg-specific IgE was detectable in the sera from both MF-negative and MF-positive individuals. To increase the specificity of the response, recombinant antigens OV11, OV27, and OV29 were tested individually or as a cocktail. Nearly 50% of the MF-negative children and 85% of the MF-positive children had detectable levels of IgG against at least one of the recombinant antigens. Only a small portion of the IgG against the recombinant peptides was IgG4. The prevalence of IgG against OV16 in samples from MF-negative children was 51%, and that for MF-positive children was 75%. The general profile of the humoral immune responses mounted by both MF-positive and a large percentage of the MF-negative children during the initial phases of infection with O. volvulus is similar to the profile reported for adults harboring chronic O. volvulus infections. These results suggest that very quickly after infection, the interactions between parasite and host result in an immunological environment that may contribute to the maintenance of a long-term, chronic infection.

Adolescent↗