New Approach for Development of Vaccine for Cytomegalovirus Infection (VaccongCMV)

Full title: New Approach for Development of Vaccine for Cytomegalovirus Infection

Grantors: Croatian Science Foundation

Grantor’s website:   http://www.hrzz.hr/

Duration: 2019-2022

Coordinator: Prof. Dr. Astrid Krmpotic

Research team:  doc. dr.sc. Irena Slavuljica dr. med.

                                dr. sc. Mia Cesarec

                                dr. sc. Lea Hirsl

                                dr. sc. Jelena Zeleznjak

                                Mijo Golemac dr. med.

                                Lydia Gacina mag. eksp. biol.

Total funding: 985.620,00 HRK

Brief description:

Human cytomegalovirus (HCMV) is the most common viral cause of congenital infections and frequently leads to long-term neurologic sequelae. Development of an effective HCMV vaccine is a high priority of modern medicine. Cytomegaloviruses (CMVs) are species specific and infection of mice with the murine CMV (MCMV) is frequently used model for HCMV infection. NKG2D is a potent activating receptor on NK cells. The importance of NKG2D in virus control is illustrated by the fact that both HCMV and MCMV developed numerous mechanisms to evade NKG2D-mediated immune control. We characterized MCMV proteins m145, m152 and m155 involved in the downmodulation of the expression of NKG2D ligands MULT1, RAE-1 and H60, respectively. The MCMV mutants lacking any of the NKG2D inhibitors are attenuated in vivo, due to the strong NK cell control. Since NKG2D acts also as a co-stimulatory receptor on CD8 T lymphocytes, there is a possibility that the main function of MCMV inhibitors of NKG2D ligands is actually the regulation of antiviral T cell response. Thus, the insertion of a ligand recognized by the activating receptor on immune cells into the CMV genome could be used as a new approach in designing vaccines that are directed to the induction of CD8 T cell response. We have combined this approach with the deletion of viral gene that subvert the host immune response and constructed recombinant MCMV in which NKG2D ligand RAE-1γ was inserted into the MCMV genome in place of its inhibitor m152 (RAE-1γMCMV) (Slavuljica et al. JCI, 2010). RAE-1γMCMV was highly attenuated in vivo but at the same time induced potent and long-lasting immune response. Encouraged by strong preliminary results, in frame of this project we plan to use recombinant MCMV expressing two other NKG2D ligands, MULT1 and H60, and test whether recombinant CMV expressing various NKG2D ligands could be used as vaccine for congenital CMV infection. Immunogenicity and protective capacity of these recombinant viruses will be determined. Phenotype and functional properties as well as protective capacity of CD8 T cells induced during infection with recombinant MCMV expressing NKG2D ligands will be studied. Humoral immune response will also be analyzed. Special emphasis will be given on safety of their use as vaccines. To that aim in newborn model of CMV infection developmental changes in cerebellum and inflammation in brain will be studied following infection. In addition, replication of recombinant viruses will be tested in immunocompetent as well as in immunodeficient hosts. Potential of recombinant MCMV expressing various NKG2D ligands to establish latency and to reactivate from it will be examined and stability of the NKG2D ligand transgene will be determined. The ultimate goal of this project is to design recombinant CMV vaccine which is safe and strongly attenuated even in immunologically immature hosts, but at the same time able to induce protective and long-lasting immune response.