Christian Willberg - Academia.edu (original) (raw)

Papers by Christian Willberg

We measured CD8+ T cell responses in 12 potentially exposed but uninfected men who have sex with ... more We measured CD8+ T cell responses in 12 potentially exposed but uninfected men who have sex with men (MSM) using cytokine flow cytometry (CFC). Four of the individuals screened exhibited polyfunctional immune responses to HIV-1 Gag or Vif. The minimum CTL epitope was mapped in one Gag responder.

Cell host & microbe, Jan 10, 2014

Macrophages contribute to HIV-1 pathogenesis by forming a viral reservoir and mediating neurologi... more Macrophages contribute to HIV-1 pathogenesis by forming a viral reservoir and mediating neurological disorders. Cell-free HIV-1 infection of macrophages is inefficient, in part due to low plasma membrane expression of viral entry receptors. We find that macrophages selectively capture and engulf HIV-1-infected CD4+ T cells leading to efficient macrophage infection. Infected T cells, both healthy and dead or dying, were taken up through viral envelope glycoprotein-receptor-independent interactions, implying a mechanism distinct from conventional virological synapse formation. Macrophages infected by this cell-to-cell route were highly permissive for both CCR5-using macrophage-tropic and otherwise weakly macrophage-tropic transmitted/founder viruses but restrictive for nonmacrophage-tropic CXCR4-using virus. These results have implications for establishment of the macrophage reservoir and HIV-1 dissemination in vivo.

PLoS Pathogens, 2014

The ability of innate immune cells to sense and respond to impending danger varies by anatomical ... more The ability of innate immune cells to sense and respond to impending danger varies by anatomical location. The liver is considered tolerogenic but is still capable of mounting a successful immune response to clear various infections. To understand whether hepatic immune cells tune their response to different infectious challenges, we probed mononuclear cells purified from human healthy and diseased livers with distinct pathogen-associated molecules. We discovered that only the TLR8 agonist ssRNA40 selectively activated liver-resident innate immune cells to produce substantial quantities of IFN-γ. We identified CD161(Bright) mucosal-associated invariant T (MAIT) and CD56(Bright) NK cells as the responding liver-resident innate immune cells. Their activation was not directly induced by the TLR8 agonist but was dependent on IL-12 and IL-18 production by ssRNA40-activated intrahepatic monocytes. Importantly, the ssRNA40-induced cytokine-dependent activation of MAIT cells mirrored responses induced by bacteria, i.e., generating a selective production of high levels of IFN-γ, without the concomitant production of TNF-α or IL-17A. The intrahepatic IFN-γ production could be detected not only in healthy livers, but also in HBV- or HCV-infected livers. In conclusion, the human liver harbors a network of immune cells able to modulate their immunological responses to different pathogen-associated molecules. Their ability to generate a strong production of IFN-γ upon stimulation with TLR8 agonist opens new therapeutic opportunities for the treatment of diverse liver pathologies.

Proceedings of the National Academy of Sciences, 2010

PLoS Pathogens, 2008

Unprotected sexual intercourse between individuals who are both infected with HIV-1 can lead to e... more Unprotected sexual intercourse between individuals who are both infected with HIV-1 can lead to exposure to their partner's virus, and potentially to super-infection. However, the immunological consequences of continued exposure to HIV-1 by individuals already infected, has to our knowledge never been reported. We measured T cell responses in 49 HIV-1 infected individuals who were on antiretroviral therapy with suppressed viral loads. All the individuals were in a long-term sexual partnership with another HIV-1 infected individual, who was either also on HAART and suppressing their viral loads, or viremic (.9000 copies/ml). T cell responses to HIV-1 epitopes were measured directly ex-vivo by the IFN-c enzyme linked immuno-spot assay and by cytokine flow cytometry. Sexual exposure data was generated from questionnaires given to both individuals within each partnership. Individuals who continued to have regular sexual contact with a HIV-1 infected viremic partner had significantly higher frequencies of HIV-1-specific T cell responses, compared to individuals with aviremic partners. Strikingly, the magnitude of the HIV-1-specific T cell response correlated strongly with the level and route of exposure. Responses consisted of both CD4 + and CD8 + T cell subsets. Longitudinally, decreases in exposure were mirrored by a lower T cell response. However, no evidence for systemic super-infection was found in any of the individuals. Continued sexual exposure to exogenous HIV-1 was associated with increased HIV-1-specific T cell responses, in the absence of systemic super-infection, and correlated with the level and type of exposure. Citation: Willberg CB, McConnell JJ, Eriksson EM, Bragg LA, York VA, et al. (2008) Immunity to HIV-1 Is Influenced by Continued Natural Exposure to Exogenous Virus. PLoS Pathog 4(10): e1000185.

PLoS ONE, 2010

Background: The HLA-B*35-Px allele has been associated with rapid disease progression in HIV-1 in... more Background: The HLA-B*35-Px allele has been associated with rapid disease progression in HIV-1 infection, in contrast to the HLA-B*35-Py allele. Methodology/Principal Findings: Immune responses to two HLA-B*35 restricted HIV-1 specific CTL epitopes and their variants were followed longitudinally during early HIV-1 infection in 16 HLA-B*35+ individuals. Subjects expressing HLA-B*35-Px alleles showed no difference in response to the consensus epitopes compared to individuals with HLA-B*35-Py alleles. Surprisingly, all the HLA-B*35-Px+ individuals responded to epitope-variants even in the absence of a consensus response. Sequencing of the viral population revealed no evidence of variant virus in any of the individuals. Conclusions/Significance: This demonstrates a novel phenomenon that distinguishes individuals with the HLA-B*35-Px rapid progressing allele and those with the HLA-B*35-Py slower progressing allele.

New England Journal of Medicine, 2014

Liver International, 2005

Patel AH. Liver cell lines for the study of hepatocyte functions and immunological response. Live... more Patel AH. Liver cell lines for the study of hepatocyte functions and immunological response. Liver International 2005: 25: 389-402. r Blackwell Munksgaard 2005

PloS one, 2012

In the USA, most HIV-1 infected children are on antiretroviral drug regimens, with many individua... more In the USA, most HIV-1 infected children are on antiretroviral drug regimens, with many individuals surviving through adolescence and into adulthood. The course of HIV-1 infection in these children is variable, and understudied.

Journal of Virology, 2005

infections. The effects of virus persistence on innate immunity, including NK cell responses, and... more infections. The effects of virus persistence on innate immunity, including NK cell responses, and the underlying mechanisms are not fully understood. We examined the frequency, phenotype, and function of peripheral blood CD3 ؊ CD56 ؉ NK subsets in HIV ؉ and HCV ؉ patients and identified significantly reduced numbers of total NK cells and a striking shift in NK subsets, with a marked decrease in the CD56 dim cell fraction compared to CD56 bright cells, in both infections. This shift influenced the phenotype and functional capacity (gamma interferon production, killing) of the total NK pool. In addition, abnormalities in the functional capacity of the CD56 dim NK subset were observed in HIV ؉ patients. The shared NK alterations were found to be associated with a significant reduction in serum levels of the innate cytokine interleukin 15 (IL-15). In vitro stimulation with IL-15 rescued NK cells of HIV ؉ and HCV ؉ patients from apoptosis and enhanced proliferation and functional activity. We hypothesize that the reduced levels of IL-15 present in the serum during HIV and HCV infections might impact NK cell homeostasis, contributing to the common alterations of the NK pool observed in these unrelated infections.

Journal of Viral Hepatitis, 2007

CD4 + T-cell responses are important for the outcome of hepatitis C virus (HCV) infection. Howeve... more CD4 + T-cell responses are important for the outcome of hepatitis C virus (HCV) infection. However, the functional status of HCV-specific CD4 + T cells in persistent infection is poorly understood. It is generally recognized that proliferative capacity of HCV-specific CD4 + T cells is weak or absent in persistent infection, but whether this results from deletion of antigen-specific cells or represents maintenance of antigen-specific but poorly proliferative populations is not defined. We used a set of ex vivo assays to evaluate the functionality of HCV specific CD4 + T cells in persistent and resolved infection. Peripheral blood mononuclear cells (PBMC) from 24 prospectively recruited HCV polymerase chain reaction (PCR) positive individuals, 12 spontaneously resolved individuals (i.e. anti-HCV+, PCR)) and 11 healthy controls were analysed for interferon-c (IFN-c) and interleukin 2 (IL-2) secretion by enzyme linked immunospot assays (ELISpot). HCV-specific CD4 + proliferative responses of carboxy fluorescein succinimidyl ester-labelled PBMC were assessed using a sensitive single cell flow cytometric assay.

Journal of Neuroimmunology, 1998

Group B streptococci are the most important bacteria inducing neonatal septicemia and meningitis.... more Group B streptococci are the most important bacteria inducing neonatal septicemia and meningitis. The aim of this study was to assess the role of IFNgamma in the induction of anti-microbial effector mechanisms in human brain tumor cells. Different human glioblastoma/astrocytoma cell lines, stimulated with IFNgamma, restricted the growth of group B streptococci. In addition, we found that TNF alpha is able to enhance the IFNgamma-mediated anti-microbial effect. In contrast to group B streptococci, other bacteria which are also capable of inducing meningitis, like E. coli and all but one of the tested Streptococcus pneumoniae strains, were not influenced by the IFNgamma treated cells. We found that the IFNgamma or the IFNgamma/TNF alpha induced activation of indoleamine 2,3-dioxygenase is responsible for the inhibition of streptococcal growth, since the addition of supplemental L-tryptophan completely blocks the IFNgamma induced bacteriostasis.

Journal of Hepatology, 2006

attributable to down-modulation of the CD3? chain. This reversible defect could contribute to bot... more attributable to down-modulation of the CD3? chain. This reversible defect could contribute to both the T cell hyporesponsiveness and the inflammatory milieu characteristic of the HBV-infected liver.

Expert Review of Vaccines, 2010

The development of the fluorescently labeled tetrameric MHC-peptide complex has enabled the direc... more The development of the fluorescently labeled tetrameric MHC-peptide complex has enabled the direct visualization, quantification and phenotypic characterization of antigen-specific T cells using flow cytometry and has transformed our understanding of cellular immune responses. The combination of this technology with functional assays provides many new insights into these cells, allowing investigation into their lifecycle, manner of death and effector function. In this article, we hope to provide an overview of the techniques used in the construction of these tetramers, the problems and solutions associated with them, and the methods used in the study of antigen-specific T cells. Understanding how the antigen-specific cells develop and function in different circumstances and with different pathogens will be key to understanding natural host defense, as well as vaccine design and assessment.

European Journal of Immunology, 2004

The recognition of MHC class I molecules by killer cell immunoglobulin-like receptors (KIR) is ce... more The recognition of MHC class I molecules by killer cell immunoglobulin-like receptors (KIR) is central to the control of NK cell function and can also modulate the CTL activation threshold. Among KIR receptors, KIR3DL2 is thought to interact with HLA-A3 and -A11, although direct evidence has been lacking. In this study, we show that HLA-A3 and -A11 tetramers specifically bind to KIR3DL2*001 transfectants and that this recognition is peptide-specific. Single amino acid substitutions in the nonamer peptide underline a critical role for residue 8 in recognition of KIR3DL2. However, the role of this interaction in vivo still remains to be established.

European Journal of Immunology, 2014

show the CD161 ++ CD8 + T-cell population is the primary T-cell population triggered by this mech... more show the CD161 ++ CD8 + T-cell population is the primary T-cell population triggered by this mechanism. Both CD161 ++ Vα7.2 + and CD161 ++ Vα7.2 − T-cell subsets responded to IL-12+IL-18 stimulation, demonstrating this response was not restricted to the MAIT cells, but to the CD161 ++ phenotype. Bacteria and TLR agonists also indirectly triggered IFN-γ expression via IL-12 and IL-18. These data show that CD161 ++ T cells are the predominant T-cell population that responds directly to IL-12+IL-18 stimulation. Furthermore, our findings broaden the potential role of MAIT cells beyond bacterial responsiveness to potentially include viral infections and other inflammatory stimuli.

Current Opinion in HIV and AIDS, 2007

This review sets out to overview treatment interruption in chronic HIV-1 infection: what treatmen... more This review sets out to overview treatment interruption in chronic HIV-1 infection: what treatment interruption promised, results from recent trials, and what the future holds. Recent studies have produced mixed results; several trials have been prematurely halted, whereas others have reported more positive outcomes. One consistent finding has been the identification of the CD4 T-cell count nadir as a critical parameter in determining the outcome of treatment interruption. The use of treatment interruption is still controversial, but it is becoming clear that certain individuals could benefit, and partial treatment interruption strategies warrant further investigation.

Clinical and Vaccine Immunology, 2008

We measured CD8 ؉ T-cell responses in 12 potentially exposed but uninfected men who have sex with... more We measured CD8 ؉ T-cell responses in 12 potentially exposed but uninfected men who have sex with men by using cytokine flow cytometry. Four of the individuals screened exhibited polyfunctional immune responses to human immunodeficiency virus type 1 Gag or Vif. The minimum cytotoxic T lymphocyte epitope was mapped in one Gag responder.

Clinical and Vaccine Immunology, 2007

Understanding human immunodeficiency virus type 1 (HIV-1)-specific cytotoxic T-lymphocyte respons... more Understanding human immunodeficiency virus type 1 (HIV-1)-specific cytotoxic T-lymphocyte responses is important for the development of vaccines and therapies. We describe a novel method for the rational selection of peptides that target stable regions of the HIV-1 genome, rich in epitopes specifically recognized by the study population. This method will be of particular use under resource/sample-limited conditions.