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Biomedical subjects

Mathias Lichterfeld

Publications and source records attributed to Mathias Lichterfeld.

31 records · Page 2Linked to original sources
PubMed2004

Loss of HIV-1-specific CD8+ T cell proliferation after acute HIV-1 infection and restoration by vaccine-induced HIV-1-specific CD4+ T cells.

Virus-specific CD8(+) T cells are associated with declining viremia in acute human immunodeficiency virus (HIV)1 infection, but do not correlate with control of viremia in chronic infection, suggesting a progressive functional defect not measured by interferon gamma assays presently used. Here, we demonstrate that HIV-1-specific CD8(+) T cells proliferate rapidly upon encounter with cognate antigen in acute infection, but lose this capacity with ongoing viral replication. This functional defect can be induced in vitro by depletion of CD4(+) T cells or addition of interleukin 2-neutralizing antibodies, and can be corrected in chronic infection in vitro by addition of autologous CD4(+) T cells isolated during acute infection and in vivo by vaccine-mediated induction of HIV-1-specific CD4(+) T helper cell responses. These data demonstrate a loss of HIV-1-specific CD8(+) T cell function that not only correlates with progressive infection, but also can be restored in chronic infection by augmentation of HIV-1-specific T helper cell function. This identification of a reversible defect in cell-mediated immunity in chronic HIV-1 infection has important implications for immunotherapeutic interventions.

AIDS Vaccines↗
PubMed2004

HIV-1 Nef is preferentially recognized by CD8 T cells in primary HIV-1 infection despite a relatively high degree of genetic diversity.

OBJECTIVE: To compare the magnitude, breadth and protein specificity of HIV-1-specific CD8 T-cell responses against the clade B consensus sequence during primary and chronic HIV-1 infection and to analyze the impact of viral diversity on the localization of detected responses. METHODS: HIV-1-specific CD8 T-cell responses against the clade B consensus sequence in individuals with acute (n = 10), early (n = 19) and chronic (n = 10) infection were longitudinally assessed using an interferon-gamma EliSpot assay. RESULTS: CD8 T-cell responses against clade B consensus sequences were preferentially directed against central regions of Nef during primary HIV-1 infection, despite a relatively higher degree of genetic diversity compared with other subsequently targeted regions. In subjects with acute and early infection, Nef-specific CD8 T-cell responses against the consensus Nef sequence represented 94 and 46% of the total magnitude of HIV-1-specific CD8 T-cell responses, respectively. Subjects with untreated chronic infection exhibited broadly diversified CD8 T-cell responses against more conserved viral regions, with only 17% of virus-specific T-cell responses targeting Nef. The initial immunodominance of Nef persisted in individuals with treated acute infection, but shifted rapidly to Gag, Env and Pol in subjects with continuous antigen exposure. CONCLUSION: These data show that despite relatively high sequence variability, viral regions within the clade B consensus sequence of Nef are preferentially recognized during primary HIV-1 infection. Later diversification of responses to other proteins during prolonged antigen exposure provides evidence of the initial preferential immunogenicity of Nef epitopes compared to similarly conserved regions within other viral proteins.

Adult↗
PubMed2004

HIV-1-specific cytotoxicity is preferentially mediated by a subset of CD8(+) T cells producing both interferon-gamma and tumor necrosis factor-alpha.

CD8(+) T cells play a crucial role in the control of viral infections by direct elimination of infected cells and secretion of a number of soluble factors. Recent data suggest that HIV-1-specific CD8(+) T cell subsets may differ in their ability to exert these effector functions. Here, we directly compared the cytokine secretion patterns and cytotoxic capacity of HIV-1-specific CD8(+) T cells, using a flow-cytometric cytotoxicity assay based on caspase-3 activation in dying target cells. These experiments revealed considerable intraindividual and interindividual differences among epitope-specific T-cell effector functions: while the frequency of HIV-1-specific CD8(+) T cells secreting interferon-gamma but no tumor necrosis factor-alpha (TNF-alpha) following antigenic stimulation was only weakly correlated to their cytotoxic activity (R = 0.05, P =.57), a subset of CD8(+) T cells secreting both inter-feron-gamma and TNF-alpha was substantially more strongly associated with cytotoxicity (R = 0.67, P <.001). This subset of CD8(+) T cells also exhibited stronger intracellular perforin expression and more pronounced direct ex vivo HIV-1-specific cytoxicity than CD8(+) T cells secreting solely interferon-gamma following sorting of these subpopulations according to their cytokine profile. These results suggest that HIV-1-specific cytotoxicity of CD8(+) T cells is preferentially mediated by a subset of CD8(+) T cells secreting both interferon-gamma and TNF-alpha.

Adult↗
PubMed2004

Rapid determination of the Delta32 deletion in the human CC-chemokine receptor 5 (CCR5) gene without DNA extraction by lightcycler real-time polymerase chain reaction.

CCR5 is a major coreceptor for cellular entry of macrophage-tropic isolates of the human immunodeficiency virus (HIV). A 32-base pair deletion of the CCR5 gene (CCR5Delta32) protects against HIV infection because the frame shift leads to a truncated protein not expressed on the cell surface. CCR5Delta32 also delays progression in heterozygous HIV-infected patients and improves responses to antiretroviral therapy. Available methods for CCR5 genotyping, however, are cost expensive and/or time consuming. To improve CCR5 genotyping we studied four primer sets flanking the CCR5Delta32 deletion site using real-time polymerase chain reaction (PCR) on a LightCycler device. Primers amplified fragments of different length depending on the presence or absence of the Delta32 mutation. Next, melting curves of the amplified fragments were analyzed using SYBR green, a conventional double-strand DNA dye. To circumvent initial DNA extraction, we also studied serially diluted "interphase" leukocytes as PCR templates after centrifugation of EDTA blood. Finally, the validity of the new method was checked by analyzing 100 blood samples with known CCR5 genotypes. Amplicons of 82 bp:50 bp and 97 bp:65 bp fragment ratios could easily be discriminated due to the differences in their melting temperatures (3 degrees C and 2 degrees C, respectively). Furthermore, CCR5 genotyping was possible without initial DNA extraction and yielded optimal results at 1:400 to 1:600 dilution of the "interphase" leukocytes. Results of the new LightCycler PCR protocol were identical to conventional CCR5 genotyping but required considerably less time and expenditures. We have established a new real-time PCR protocol, which enables fast, cost-saving, and reliable CCR5 genotyping.

DNA Primers↗
PubMed2004

Differences in the expressed HLA class I alleles effect the differential clustering of HIV type 1-specific T cell responses in infected Chinese and caucasians.

China is a region of the world with a rapidly spreading HIV-1 epidemic. Studies providing insights into HIV-1 pathogenesis in infected Chinese are urgently needed to support the design and testing of an effective HIV-1 vaccine for this population. HIV-1-specific T cell responses were characterized in 32 HIV-1-infected individuals of Chinese origin and compared to 34 infected caucasians using 410 overlapping peptides spanning the entire HIV-1 clade B consensus sequence in an IFN-gamma ELISpot assay. All HIV-1 proteins were targeted with similar frequency in both populations and all study subjects recognized at least one overlapping peptide. HIV-1-specific T cell responses clustered in seven different regions of the HIV-1 genome in the Chinese cohort and in nine different regions in the caucasian cohort. The dominant HLA class I alleles expressed in the two populations differed significantly, and differences in epitope clustering pattern were shown to be influenced by differences in class I alleles that restrict immunodominant epitopes. These studies demonstrate that the clustering of HIV-1-specific T cell responses is influenced by the genetic HLA class I background in the study populations. The design and testing of candidate vaccines to fight the rapidly growing HIV-1 epidemic must therefore take the HLA genetics of the population into account as specific regions of the virus can be expected to be differentially targeted in ethnically diverse populations.

Alleles↗
PubMed2004

Selection, transmission, and reversion of an antigen-processing cytotoxic T-lymphocyte escape mutation in human immunodeficiency virus type 1 infection.

Numerous studies now support that human immunodeficiency virus type 1 (HIV-1) evolution is influenced by immune selection pressure, with population studies showing an association between specific HLA alleles and mutations within defined cytotoxic T-lymphocyte epitopes. Here we combine sequence data and functional studies of CD8 T-cell responses to demonstrate that allele-specific immune pressures also select for mutations flanking CD8 epitopes that impair antigen processing. In persons expressing HLA-A3, we demonstrate consistent selection for a mutation in a C-terminal flanking residue of the normally immunodominant Gag KK9 epitope that prevents its processing and presentation, resulting in a rapid decline in the CD8 T-cell response. This single amino acid substitution also lies within a second HLA-A3-restricted epitope, with the mutation directly impairing recognition by CD8 T cells. Transmission of the mutation to subjects expressing HLA-A3 was shown to prevent the induction of normally immunodominant acute-phase responses to both epitopes. However, subsequent in vivo reversion of the mutation was coincident with delayed induction of new CD8 T-cell responses to both epitopes. These data demonstrate that mutations within the flanking region of an HIV-1 epitope can impair recognition by an established CD8 T-cell response and that transmission of these mutations alters the acute-phase CD8(+) T-cell response. Moreover, reversion of these mutations in the absence of the original immune pressure reveals the potential plasticity of immunologically selected evolutionary changes.

Amino Acid Sequence↗
PubMed2004

Comprehensive analysis of human immunodeficiency virus type 1-specific CD4 responses reveals marked immunodominance of gag and nef and the presence of broadly recognized peptides.

Increasing evidence suggests that human immunodeficiency virus type 1 (HIV-1)-specific CD4 T-cell responses contribute to effective immune control of HIV-1 infection. However, the breadths and specificities of these responses have not been defined. We screened fresh CD8-depleted peripheral blood mononuclear cells (PBMC) from 36 subjects at different stages of HIV-1 infection for virus-specific CD4 responses by gamma interferon enzyme-linked immunospot assay, using 410 overlapping peptides spanning all HIV-1 proteins (based on the clade B consensus sequence). HIV-1-specific CD4 responses were identified in 30 of the 36 individuals studied, with the strongest and broadest responses detected in persons treated in acute infection who underwent treatment interruption. In individuals with identified responses, the total number of recognized HIV-1 peptides ranged from 1 to 36 (median, 7) and the total magnitude of responses ranged from 80 to >14,600 (median, 990) spot-forming cells/10(6) CD8-depleted PBMC. Neither the total magnitude nor the number of responses correlated with viremia. The most frequent and robust responses were directed against epitopes within the Gag and Nef proteins. Peptides targeted by >/=25% of individuals were then tested for binding to a panel of common HLA-DR molecules. All bound broadly to at least four of the eight alleles tested, and two bound to all of the HLA-DR molecules studied. Fine mapping and HLA restriction of the responses against four of these peptides showed a combination of clustering of epitopes and promiscuous presentation of the same epitopes by different HLA class II alleles. These findings have implications for the design of immunotherapeutic strategies and for testing candidate HIV vaccines.

Adult↗
PubMed2003

The tandem-repeat polymorphism of the DC-SIGNR gene does not affect the susceptibility to HIV infection and the progression to AIDS.

DC-SIGNR is a C-type lectin that functions as a transreceptor for HIV-1. The exon 4 of the DC-SIGNR gene comprises a variable number of 69-bp tandem repeats, encoding for parts of the extracellular protein domain. Here, we analyzed the relevance of this gene polymorphism for the interindividual transmission of HIV-1 and the progression to AIDS. A cross-sectional comparison between HIV-1-infected patients (n = 391) and healthy volunteers (n = 134) did not reveal significant differences with regard to the DC-SIGNR allele distribution. Moreover, DC-SIGNR allele frequencies were similar in slowly progressing HIV patients (n = 31) and patients who rapidly progressed to AIDS (n = 46). Additionally, in a cohort of 149 newly HIV-infected patients, no relationship was found between HIV set point viremia and DC-SIGNR genotypes. Thus, the DC-SIGNR tandem-repeat polymorphism in exon 4 does not have a significant impact on the host's susceptibility to HIV and the clinical progression to AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Diagnosis of invasive septate mold infections. A correlation of microbiological culture and histologic or cytologic examination.

We correlated results of microbiologic culture and histopathologic examination for 2,891 consecutive samples from autopsy tissue, surgical or biopsy tissue, and bronchoalveolar lavage (BAL) or bronchial washing (BW) specimens. For 23 autopsy cases with suspected invasive septate mold infections by histopathologic examination, culture yielded a mold in 12 cases (52%). For 1,683 surgical or biopsy samples, histopathologic evidence of invasive septate mold infection was present in 30 samples, 9 of which also grew mold by culture (30%); 20 additional samples grew mold in culture alone, possibly representing culture contamination. Of 1,185 BAL and BW samples, mold was evident in 28 by cytologic examination and culture, 20 by cytologic examination alone, and 68 by culture alone. These results suggest a positive concordance for culture and histologic-cytologic examination of 23%, although both methods were negative in 96% of surgical and biopsy tissue and BAL and BW samples. The septate molds cultured from these samples were Aspergillus fumigatus (19), Aspergillus flavus (15), Aspergillus terreus (13), Aspergillus niger (7), Fusarium species (3), and Scedosporium apiospermum (2). A flavus was isolated significantly more frequently from tissue than from BAL and BW samples.

Aspergillosis↗
PubMed2002

Pilot study of interferon alpha high-dose induction therapy in combination with ribavirin for chronic hepatitis C in HIV-co-infected patients.

Twenty-three HIV/hepatitis C virus (HCV)-co-infected patients received dose-escalated IFN-alpha (5 MIU/day) induction therapy for 10 weeks, followed by 36 weeks of thrice-weekly IFN-alpha treatment (5 MIU), both in combinations with ribavirin. Sustained HCV clearance was observed in three patients. Nine patients discontinued the study aas a result of adverse reactions such as anaemia, pancreatitis and depression. In HIV/HCV-co-infected patients, the therapeutic benefit of high-dose IFN-alpha therefore seems to be limited by its poor tolerability.

Adult↗
PubMed2002

Reduced CC chemokine receptor (CCR) 1 and CCR5 surface expression on peripheral blood T lymphocytes from patients with chronic hepatitis C infection.

T cell recruitment to the infected liver is an essential step for the efficient elimination of hepatitis viruses. The surface expression of CC chemokine receptor (CCR) 1, CCR4, and CCR5 on peripheral blood T lymphocytes and their responsiveness to the chemokines macrophage inflammatory proteins (MIP)-1alpha, MIP-1beta, and RANTES (regulated on activation, normally T cell-expressed and secreted) was analyzed in patients with chronic hepatitis C and hepatitis B infection and compared with healthy subjects. Although CCR4 surface expression was not altered, hepatitis C virus (HCV)-infected patients had lower proportions of CD8 T cells with CCR1 and CCR5 surface expression (P<.05). Migration of CD8 T cells in response to MIP-1alpha, MIP-1beta, and RANTES was significantly reduced in HCV-infected patients (P<.05). Intracellular CCR1 and CCR5 protein and messenger RNA levels in peripheral blood T cells did not indicate reduced chemokine receptor biosynthesis in hepatitis C infection. Thus, chronic hepatitis C, but not hepatitis B, infection alters surface expression of distinct CCRs, resulting in lower CC chemokine responsiveness.

Adult↗