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Research Group Prof. Dr. med. Oliver T. Keppler

HIV-host interactions and chemo-sensitization

Areas of investigation

HIV/AIDS has become one of the most devastating pandemics in recorded history. AIDS is the fourth-biggest global killer and the leading cause of death in Africa. HIV/AIDS persists as a major cause of morbidity in Western societies, since currently available pharmacotherapies can only partly control, but not cure this immunodestructive viral infection. Furthermore, these drugs frequently cause severe side effects and HIV drug resistance development is rapidly emerging. Globally, the lack of effective treatment regimens causes immense human suffering and high cost for society.
My laboratory seeks to better understand the pathological interplay of HIV with the host’s immune system and its target cells with the goal of providing new approaches for prophylaxis and therapy.

1. Intrinsic immunity and resting CD4 T-cells

Besides classical innate and acquired immune responses, mammals have evolved a set of genes that are capable of suppressing or preventing virus replication at the cellular level.
These so called restriction factors, which are frequently up-regulated by host cells in response to virus infection, appear to impose particularly effective barriers in the context of cross-species transmission of viruses. Accordingly, they have been classified as “intrinsic” immunity, representing an innate cellular network for the front-line defense in an immunologically naïve host.
SAMHD1 was recently identified as a restriction factor, the expression of which prevents the completion of HIV-1 reverse transcription in macrophages and dendritic cells. Recently, we and others were able to show that SAMHD1 also acts as a restriction factor in resting CD4 T cells, expanding the relevant cell pool from myeloid to lymphoid cells. The mode of action of this deoxynucleotide triphosphohydolase appears to be primarily the depletion of intracellular dNTP pools below a threshold required for reverse transcription of the viral RNA into complementary DNA.
HIV encodes a unique set of accessory gene products (Vif, Nef, Vpr, Vpu, Vpx) to optimize its replication in the human host. Knowledge gained over the last years suggests that this is achieved, in part, by counteracting host restriction factors, including APOBEC3, CD317/Tetherin, SAMHD1 and SerinC5.
Using state-of-the art techniques from molecular virology, cell biology, immunology and biochemistry, our laboratory pursues the following goals:

  • Elucidate the mechanisms by which known and newly identified restriction factors induce a potent block for virus replication of HIV-1 and other pathogenic viruses
  • Decipher how accessory viral proteins mediate their antagonistic function
  • Establish the relevance of restriction factors for HIV transmission and pathogenesis
  • Shed light on the virus-host coevolution and the regulation of cross-species transmission

2. HIV pathogenesis ex vivo

The human lymphoid ex vivo histoculture model, derived from routine tonsillectomy material, is a biologically relevant experimental platform permissive for HIV infection independent of exogenous stimulation by mitogens or interleukin-2. This histoculture maintains the tonsil’s natural cytokine milieu, cellular activation status, and cell-to-cell interactions. In this valuable ex vivo model system to address the following questions:

  • Define differences in replication potential and pathogenesis of primary, patient-derived HIV-1 isolates with respect to their variable coreceptor usage, clinical behavior, and contribution to the HIV pandemic
  • Explore mechanisms of HIV-induced cell death

3. HIV-1 animal models

A major bottleneck for the development of novel therapeutic strategies against HIV is the lack of a highly permissive and readily available small animal model, as normal mice, rats and rabbits cannot be infected with HIV since they impose multiple cellular barriers to HIV replication. Recent scientific advances have demonstrated that specifically engineered transgenic rodents can overcome individual species-specific barriers to HIV replication.

Schematic representation of consecutive steps (1-7) in the HIV replication cycle

Barriers to HIV-1 replication at distinct steps in primary mouse, rat, and rabbit cells, are indicated by X. The major barrier at virus entry is common to all non-human species and can be overcome by transgenic expression of the HIV receptor complex.
Via transgenesis, knock-out approaches and virus adaptation we propose to develop multi-transgenic rat and rabbit models that is highly susceptible to infection by HIV-1 and that recapitulates key aspects of the disease in humans, thus enabling the development of improved pharmacotherapy and possibly vaccines to fight HIV.

Towards this goal, we have pioneered the generation of rats transgenically expressing human CD4 and human CCR5 (together referred to as the HIV receptor complex) and human Cyclin T1 in relevant target cells. Transgenic Sprague-Dawley rats display a high proviral load in lymphatic organs early after intravenous HIV-1 challenge, while viremia in plasma is low and transient.  These animals allow a rapid and predictive preclinical testing of antiviral compounds targeting virus entry, reverse transcription, and integration and have contributed to the in vivo-evaluation of a novel, semen-derived pathogenicity factor as well as vaccine candidates.

Our goals in projects involving these multi-transgenic small animals are:

  • Characterize and overcome remaining barriers to efficient HIV-1 replication
  • Conduct studies on viral transmission and pathogenesis
  • Validate and mechanistically dissect novel antiviral strategies, including pharmacotherapy, vaccines and gene therapy approaches, prior to advancement to phase I clinical trials

More recently, Dr. Hanna-Mari Baldauf, nee Tervo, has identified rabbits as a species with even fewer intrinsic barriers to HIV replication. Based on this work, she is currently advancing the development of genetically modified rabbits to serve as a more permissive model for lentiviral infection in her newly established research group (Research Group Baldauf).

Furthermore, we are currently establishing a cutting-edge humanized mouse model employing gene edited hematopoietic precursors as a platform to study the biology of HIV infection ex vivo and in vivo.

4. Novel cellular interactors of HIV

HIV consists of a small genome and thus relies heavily on the host cellular machinery for production of viral progeny. To exploit cellular proteins for replication and to overcome host cellular factors with antiviral activity, HIV has evolved a set of accessory and regulatory proteins that apparently shape an optimized environment for its replication and facilitate evasion from innate immunity, respectively. We seek to identify new interactors of the HIV-host interplay, which are required for the HIV replication cycle. A particular focus lies on resting CD4 T-cells. By using techniques ranging from classical cell biological and biochemical methods to state-of-the art analysis by e.g. mass spectrometry we try to identify new cellular interaction partners. Identified candidates are analyzed in more detail to understand their function within the context of HIV infection in primary target cells.

5. SAMHD1’s role in oncology

Nucleoside analogs frequently constitute the backbone of chemotherapy regimens in malignant diseases, however success is variable and often unpredictable. The identification of biomarkers to guide treatment decisions as well as novel therapeutic interventions to overcome chemoresistance are urgently needed. Together with the group of Prof. J. Cinatl in Frankfurt we recently discovered that expression of SAMHD1 hydrolyzes and thus inactivates important metabolites of several of these nucleoside analogs and, importantly, predicted therapeutic success in patients with acute myeloid leukemia (AML). Our major goals are (i) to develop SAMHD1-centered metabolic biomarker panels for treatment stratification, (ii) explore the breadth of this mode of action, and (iii) to advance the optimization and preclinical assessment of intervention approaches targeting SAMHD1.

For details see also Schneider et al., Nature Medicine 23, 250–255 (2017)

Current Group Members

Oliver T. Keppler, MD, Professor, chair of virology
Email: keppler(at)mvp.uni-muenchen.de

Arne Auste, Veterinarian
Email: auste(at)mvp.uni-muenchen.de
Phone: +49 89-2180-76850

Malin Bigos, MD student
E-Mail: malin.bigos(at)med.uni-heidelberg.de
Phone: +49 6221-56-1326

Rebecca van Dijk-Blom, PhD
Email: vandijk(at)mvp.uni-muenchen.de
Phone: +49 89-2180-76850

Project Management
Natascha Grzimek-Koschewa, PhD
Email: koschewa(at)mvp.uni-muenchen.de
Phone: +49 89-2180-72901

Ina Koeva-Slancheva, technician
Email: koeva@mvp.uni-muenchen.de
Phone: +49 89-2180-76863

Maximilian Münchhoff, MD
Email: muenchhoff(at)mvp.uni-muenchen.de
Phone: +49 89-2180-72901

Stephanie Schneider, technician
Email: schneider(at)mvp.uni-muenchen.de
Phone: +49 89-2180-76850

Verena Siegert, MD student
Email: verena.siegert(at)kgu.de
Phone: +49 69-6301-7162

Marcel Stern, PhD student
Email: stern(at)mvp.uni-muenchen.de
Phone: +49 89-4140-9271

Paul Robin Wratil, MD
Email: wratil(at)mvp.uni-muenchen.de
Phone: +49 89-2180-76850

Qianhao Xiao, PhD student
Email: qianhao(at)mvp.uni-muenchen.de
Phone: +49 89-2180-76863

Former lab members

Tarek Adam (visiting medical student)
Ina Ambiel (technician)
Julia Bitzegeio (Diploma student)
Paul Burda (Master student)
Elina Erikson (PhD student)
Michael Färber (PhD student)
Kerstin Ganter (technician)
Silvia Geuenich (PhD student)
Christine Goffinet (PhD student, postdoctoral fellow)
Ebrahim Hassan (Master student)
Nikolas Herold (MD)
Verena Jakobi (technician)
Klara Kaaden (Master student)
Christian Kern (Bachelor student)
Margarethe Martin (technician)
Nico Michel (postdoctoral fellow)
Lena Oberbremer (technician)
Katharina Pauli (MD student)
Claudia Rückert (Master student)
Daniel Rupp (MD student)
Kristina Schenkova (postdoctoral fellow)
Sarah Schmidt (PhD student, postdoctoral fellow)
Lismarie Schüller (technician)
Sarah-Marie Schwarz (PhD)
Lena Stegmann (technician)
Stephanie Venzke (PhD student)
Xaver Sewald (PhD)
Ariane Zutz (PhD)
Christian Schölz (PhD)
Helena Lejk (technician)
Hanna-Mari Baldauf (PhD)
Patricia Pereira (PhD student)

Awards and Honours

  • AIDS Forschungspreis 2007 (Deutsche Gesellschaft für Infektiologie): Christine Goffinet and Oliver T. Keppler
  • Innovationspreis 2007 der BioRegionen Deutschlands: Oliver T. Keppler
  • Hygiene-Preis 2007 der Rudolf Schülke Stiftung: Christine Goffinet, Ina Ambiel (née Allespach), Oliver T. Keppler
  • Loeffler-Frosch-Preis 2008 der Gesellschaft für Virologie: Oliver T. Keppler
  • Nachwuchsforscherpreis 2009 der Deutschen AIDS Gesellschaft: Hanna-Mari Baldauf (née Tervo)
  • Wolfgang-Stille Preis 2010 der Paul-Ehrlich-Gesellschaft f. Chemotherapie: Oliver T. Keppler and Christine Goffinet
  • Postdoktoranden-Preis 2012 der Robert-Koch-Stiftung: Christine Goffinet (since 2010 in Ulm)
  • Heinz-Ansmann-Preis für AIDS-Forschung 2012: Oliver T. Keppler
  • AIDS-Forschungspreis der H.W. & J. Hector-Stiftung 2013: Oliver T. Keppler
  • Postdoktoranden-Preis 2013 der Robert-Koch-Stiftung: Hanna-Mari Baldauf
  • AIDS Forschungspreis 2017 der Deutschen Gesellschaft für Infektiologie (DGI): Maximilian Münchhoff

Publications

Follow this link to Pubmed.

Contact

Prof. Oliver T. Keppler
Max von Pettenkofer Institute, Virology
National Reference Center for Retroviruses
Faculty of Medicine
LMU München
Pettenkoferstr. 9a
80336 Munich, Germany

Gene Center, LMU München
Feodor-Lynen-Str. 25
81377 Munich, Germany

Tel.: 089-2180-72901
Fax: 089-2180-72902
keppler(at)mvp.uni-muenchen

 

Administration
Mrs. Brigitte Held
Assistant to the Director
Max von Pettenkofer Institute, Virology
National Reference Center for Retroviruses
Faculty of Medicine
LMU München
Pettenkoferstr. 9a
80336 Munich, Germany

Tel.: 089-2180-72901
Fax: 089-2180-72902
held(at)mvp.uni-muenchen.de