Research in the lab centers around the cytomegalovirus, a herpesvirus of the β-herpesvirus subfamily with high seroprevalence in the human population all around the world. This virus is a well-known TORCH pathogen with the ability to cross the placenta and congenitally infect the unborn fetus leading to severe neurological sequelae. Additionally, the virus is a major threat to transplant recipients as reactivation of the latent virus post-transplantation can lead to graft rejection and increase mortality. In the immunocompetent host on the other hand, CMV is generally benign with the most severe indications of disease ranging from light flu-like symptoms to CMV induced mononucleosis in a small minority of cases. CMV biology has been studied for more than a century and has fascinated immunologists and vaccinologist alike as the virus has developed the very unique ability to shape the host immune responses to create an environment optimize for virus persistence and spread. Our work focusses on uncovering the mechanisms the virus uses to evade the intrinsic, innate and adaptive immunity employing the rhesus macaque (RM) in vivo model with the goal to translate our research to construct vaccine vectors based on CMV that can be used to program the host immune response to induce protective immunity against diseases where either no vaccine exists or where presently administered vaccines display unsatisfactory efficacy.

RhCMV as a novel in vivo model system in CMV research

Since CMVs exhibit strict species specificity, animal model using the species specific CMV have to be employed for all examinations of in vivo virus behavior. Over the past decade, we have been able to establish the rhesus macaque model system using RhCMV as a viable, although costly, alternative to rodent models. The biggest advantage of our primate models is that rhesus macaques show a very close evolutionary relationship to humans which is mirrored by their corresponding CMV species, leading to functional conservation of immune evasion strategies in the two virus species which are not conserved in rodent CMVs. Hence, we can use our model system to examine CMV immune evasion strategies in the living host with the potential to extrapolate the achieved data to HCMV behavior in humans. This allows us to test novel vaccine approaches targeting CMV in a highly relevant in vivo system with the ability to potentially translate this work for interventions or preemptive vaccine strategies for human applications.

CMV based vaccine vector development

Primary infections with the human cytomegalovirus have been documented to induce very strong B- and T-cell responses and even after the establishment of viral latency roughly 10% of all T-cells of the memory compartment can indefinitely be CMV specific. Even more amazingly, since the virus will reactivate continuously and by that, will re-challenge the host immune system continuously, the virus specific CD8+ T-cells will always retain effector memory (T_EM) phenotype, enabling them to immediately display cytolytic activity upon encountering their target antigen without the need to differentiate and proliferate first. This intriguing biology makes CMVs ideal vectors for vaccine development and we have been able to show that our experimental constructs can be programmed to prime specific CD8+ T-cell responses against target antigens introduced into the viral backbone by inducing the presentation of target derived peptides on MHC-II alleles as well as unconventional, non-polymorphic HLA-E molecules. This very intriguing ability is unique to CMV and we were able to demonstrate that CMV based vaccine vectors targeting SIV can protect more than half of our test animals from acquiring this chronic infection. Similarly, CMV based vaccine vectors against mycobacterium tuberculosis protected more than 70% of vaccinated animals from Tb related pathology, in many cases with sterilizing immunity. This groundbreaking research has enabled us to propose novel vaccine approaches for human applications and we are attempting to translate our vaccine vectors from the RhCMV/RM model system to HCMV based vaccine constructs for pending human clinical trials.

CMV evolution and species specificity

CMVs have co-evolved with their respective host species for millions of years in a constant battle with the immune system leading to perfect adaptation and control of the host innate and adaptive immune responses. This perfect adaptation to one host has also led to strict species specificity as CMVs of one species are incapable of overcoming the immune defense mechanism in a host of a different species. Given the strict species specificity, HCMV cannot productively infect any animal model and experimental data generated with related CMV species have to be extrapolated to the human virus. By comparing CMV isolates from a wide range of non-human primate species, we are hoping to identify viral factors that confer incompatibility in cross species infection. This research will hopefully enable us to design chimeric vectors based on HCMV supplemented with RhCMV genes with the ability to productively infect rhesus macaques so that they can be immunologically and virologically examined in this in vivo model before use in human clinical trials.

Biography

Publications

• Kolb P.*, Sijmons S.*, McArdle M.R., Taher H.,  Womack J., Hughes C., Ventura A., Jarvis M.A., Stahl-Hennig C., Hansen S., Picker L.J., Malouli D., Hengel H., Früh K. Identification and functional characterization of a novel Fc gamma-binding glycoprotein in Rhesus Cytomegalovirus. J Virol. 2018 Nov 28. pii: JVI.02077-18.
• ChildS.J., Hickson S.E., Bayer A., Malouli D., Früh K., Geballe A.P. Antagonism of the protein kinase R pathway in human cells by rhesus cytomegalovirus. J Virol. 2018 Feb 26;92(6). pii: e01793-17.
• Hansen S.G.*, Zak D.E.*, Xu G.*, Ford J.C., Marshall E.E., Malouli D., Gilbride R.M., Hughes C.M., Ventura A.B., Ainslie E., Randall K.T., Selseth A.N., Rundstrom P., Herlache L., Lewis M.S., Park H., Planer S.L., Turner J.M., Fischer M., Armstrong C., Zweig R.C., Valvo J., Braun J.M., Shankar S., Lu L., Sylwester A.W., Legasse A.W., Messerle M., Jarvis M.A., Amon L.M., Aderem A., Alter G., Laddy D.J., Stone M., Bonavia A., Evans T.G., Axthelm M.K., Früh K., Edlefsen P.T., Picker L.J. Prevention of tuberculosis in rhesus macaques by a cytomegalovirus-based vaccine. Nat Med., 2018 Feb;24(2):130-143.
• Vashee S., Stockwell T., Alperovich N., Denisova E., Gibson D., Cady K., Miller K., Kannan K., Malouli D., Crawford L., Voorhies A., Bruening E., Caposio P., Früh K..  Cloning, assembly and modification of the primary human cytomegalovirus isolate Toledo by yeast-based transformation-associated recombination. mSphere. 2017 Oct 4;2(5). pii: e00331-17.
• Burwitz B.J.*, MalouliD.*, BimberB.N., Reed J.S., Ventura A.B., Hancock M.H., UebelhoerL.S., Bhusari A., Hammond K.B.,Espinosa TrethewyR.G., Klug A., Legasse A.W., Axthelm M.K., Nelson J.A., Park B.S., Streblow D.N., Hansen S.G., Picker L.J., Früh K., Sacha J.B. Cross-species rhesus cytomegalovirus infection of cynomolgus macaques. PLoS Pathog. 2016 Nov 9;12(11):e1006014.
• Sturgill E.R., Malouli D., Hansen S.G., Burwitz B.J., Seo S., Schneider C.L., Womack J.L., Verweij M.C., Ventura A.B., Bhusari A., Jeffries K.M., Legasse A.W., Axthelm M.K., Hudson A.W., Sacha J.B., Picker L.J., Früh K. Natural Killer Cell Evasion is Essential for Primary Infection by Rhesus Cytomegalovirus. PLoS Pathog. 2016 Aug 31;12(8):e1005868.
• Hansen S.G.*, Wu H.L.*, Burwitz B.J., Hughes C.M., Hammond K.B., Ventura A.B., Reed J.S., Gilbride R.M., Ainslie E., Morrow D.W., Ford J.C., Selseth A.N., Pathak R., Malouli D., Legasse A.W., Axthelm M.K., Nelson J.A., Gillespie G.M., Walters L.C., Brackenridge S., Sharpe H.R., López C.A., Früh K., Korber B.T., McMichael A.J., Gnanakaran S., Sacha J.B.^#, Picker L.J.^#Broadly targeted CD8⁺ T cell responses restricted by major histocompatibility complex E. Science. 2016 Feb 12;351(6274):714-20.
• Malouli D.*, Hansen S.G.*, Nakayasu E.S., Marshall E.E., Hughes C.M., Ventura A.B., Gilbride R.M., Lewis M.S., Xu G., Kreklywich C., Whizin N., Fischer M., Legasse A.W., Viswanathan K., Siess D., Camp D.G. 2nd, Axthelm M.K., Kahl C., DeFilippis V.R., Smith R.D., Streblow D.N., Picker L.J.^#, Früh K.^# Cytomegalovirus pp65 limits dissemination but is dispensable for persistence. J Clin Invest. 2014 May 1;124(5):1928-44.
• Hansen, S.G., Sacha, J.B., Hughes, C.M., Ford, J.C., Burwitz, B.J., Scholz, I., Gilbride, R.M., Lewis, M.S., Gilliam, A.N., Ventura, A.B., Malouli D., Xu G., Richards R., Whizin N., Reed J.S., Hammond K.B., Fischer M., Turner J.M., Legasse A.W., Axthelm M.K., Edlefsen P.T., Nelson J.A., Lifson J.D., Früh K., Picker L.J. Cytomegalovirus vectors violate CD8+ T cell epitope recognition paradigms. Science. 2013 May 24; 340:1237874.
• Malouli D., Nakayasu E.S., Viswanathan K., Camp D.G. 2nd, Chang W.L., Barry P.A., Smith R.D., Früh K., Reevaluation of the Coding Potential and Proteomic Analysis of the BAC-Derived Rhesus Cytomegalovirus Strain 68-1. J Virol. 2012 Sep;86(17):8959-73.

*shared first authorship, ^#shared corresponding authorship