Pathogenicity of SARS-CoV-2 and Development of vaccines and therapeutic agents for COVID-19
Since 2020, we have been conducting research for the emerging coronavirus, SARS-CoV-2 that causes COVID-19 spreading all over the world. We have shown that SARS-CoV-2 causes pneumonia and thrombus in a nonhuman primate model. The nonhuman primate model of COVID-19 has a lot of similarities to the human disease. Therefore, we use the model for the development of vaccines and therapeutic medicines against COVID-19. Using the nonhuman primate model, we analyze not only viral propagation and genes of SARS-CoV-2 but also pneumonia in X-ray imaging and pathological diagnosis and immune responses against COVID-19.
Development of vaccines, therapeutic agents, and a novel immunotherapy against influenza virus infection
Using cynomolgus monkeys, we firstly clarified the pathogenicity of the pandemic H1N1 influenza virus that was prevalent worldwide in 2009. We have also clarified the pathogenicity of highly pathogenic avian influenza virus (HPAIV) infection since HPAIV infection in birds is sporadically detected in Japan. Therefore, we have established an animal experiment system in which cynomolgus macaques become a severe disease after HPAIV infection. Using this system, the cause of the aggravation in cynomolgus monkeys after HPAIV infection is becoming clear. Based on the results, we are looking for a novel immunotherapy to prevent a death from HPAIV infection.
We verify the efficacy and safety of the whole-particle vaccine against influenza virus with improved inactivation method, which were developed in collaboration with Professor Hiroshi Kida in Hokkaido University using not only mice but also cynomolgus monkeys. In addition, we are analyzing specimens from clinical trials inoculated with whole particle vaccine.
In the research on treatments for influenza virus infection, we use the monkey model to verify the efficacy of existing and newly developed drugs. Furthermore, using animal models, we predict the frequency of drug-resistant viruses and analyze the properties of resistant viruses.
Antimicrobial Agents and Chemotherapy 58: 4795-4803, 2014. doi: 10.1128/AAC.02817-14.
Antimicrobial Agents and Chemotherapy 55: 4961-4970, 2011. doi: 10.1128/AAC.00412-11.
Cancer and Transplantation immunology
We conduct a research on cancer and transplantation immunology using cynomolgus monkeys.
Research Center for Animal Life Science in Shiga University of Medical Science breeds a large number of cynomolgus monkeys. Furthermore, cynomolgus monkeys carrying a specific major histocompatibility antigen complex genes (MHC, a kind of blood type) that cause rejection after transplantation are also maintained. Cells from monkeys that have an identical MHC type on both chromosomes (MHC homozygous monkeys) could be transplanted to monkeys that have the identical MHC on only one chromosome (MHC heterozygous monkeys) with less immunological rejection (Figure 1). Using the monkeys, we plan to create a monkey cancer model, perform cell transplantation and organ transplantation to develop anti-cancer drugs and drugs to reduce rejection. We also analyze immune responses in the transplantations.
We try to create a cancer model of cynomolgus monkeys. Using induce pluripotent stem cells (iPSCs) prepared from MHC homozygous monkey cells, we made cancer cells and transplanted them into MHC heterozygous monkeys. The MHC heterozygous monkeys transplanted with embryonal cancer cells derived from the MHC homozygous monkey iPSCs developed antibodies against GRP94 on the surface of the transplanted cells, and the cancer cells were rejected with in 4 weeks (Cancer Res. 77; 6001-, 2017; Figure 2). We also found that cancer cell-specific killer T cells (TILs) infiltrated into the transplanted cancer (Sci Rep. 21: 8414, 2020 / unpublished data).
Currently, we have generated tumor antigen-specific T cells artificially transduced the antigen-specific T cell receptor (TCR) gene of the TILs that attack the embryonal cancer cells, and plan to inject them into the cancer bearing monkey as cell therapy, which are conducted in collaboration with the Department of Molecular Physiological Chemistry.
We also perform transplantation therapy using cells derived from iPSCs of MHC homozygous monkeys into MHC heterozygous monkeys. We analyze function of the transplanted cells and host immune responses against the cells. In the collaboration with Dr. Jun Takahashi and Dr. Asuka Morizane in CiRA, Kyoto University, dopamine-producing cells derived from iPSCs were transplanted into the brain of a cynomolgus monkey with Parkinson's disease. MHC-matched cell transplantation showed better survival of the dopamine-producing cells and a less inflammatory response than MHC-mismatched transplantation (Nat Commun. 30: 385, 2017). Based on this result, preparations for clinical trials are in progress.
Since the transplantation of cells derived from iPSCs may contain some undifferentiated cells, there is a concern that tumor (teratomas) will develop from the undifferentiated cells in the transplanted host. Therefore, we transplanted a number of iPSCs into MHC-matched cynomolgus monkeys and observed the development of teratomas. As a result, teratomas developed in a cynomolgus monkey transplanted with autologous iPSCs (Figure. 3), not in cynomolgus monkeys transplanted with allogenic iPSCs with the identical MHC. Based on the results, it is considered that the risk of teratoma development is low in MHC-matched allogeneic transplantation of iPSCs-derived cells (Cell Transplant 30: 963689721992066, 2021).
Regarding organ transplantation, we conducted a uterine transplantation experiment using cynomolgus monkeys in collaboration with Dr. Iori Kisu, the Department of Obstetrics and Gynecology, Keio University. There is no clinical practice of uterus transplantation to women who have no uterus by birth or who have lost their uterus for some reasons such as Rokitansky syndrome in Japan, while uterus transplantation has already been attempted in humans in the world. About 40 babies have been reported to be born from mothers who received uterine transplantation in more than 10 countries. To move the uterine transplantation to clinical therapy in Japan, we performed uterine transplantation using MHC-identified cynomolgus monkeys as pre-clinical studies assuming uterine transplantation between mother and her daughter. In the end, we succeeded in pregnancy and childbirth in the non-human primate uterus transplantation, which was the first case in the world (J Clin
Med 8, pii: E1572, 2019 / J Obstet Gynaecol Res 46: 2251, 2020). Furthermore, we currently analyze the difference in immune responses between MHC-matched and unmatched transplantations using a skin graft model of cynomolgus monkeys.