Gammadelta-T cell-targeted therapy on the formation of adaptive immunity against influenza virus infection
Dr Zheng, Jian (Principal investigator)
gammadelta-T, influenza virus, adaptive immunity, pamidronate
Block Grant Earmarked for Research (104)
HKU Project Code
Seed Fund for Basic Research
Influenza virus infection consistently represents for a global threaten on human health, while the novel avian H7N9 influenza virus [1-3] and the drifted H3N2 influenza virus  occurring in 2013 and 2015 respectively caused severe respiratory situation and hundreds of deaths in Hong Kong and mainland of China. Currently, the most effective strategy on preventing influenza virus infection and limiting the spread of influenza virus is still vaccination. However, the frequent mutations of influenza virus often caused the effort of vaccine scheme in vain . Although the commercially available antivirals such as oseltamivir and zanamivir are generally effective in reducing viral load and improving clinical outcome if initiated within 48 hours of symptom onset, these antivirals are less effective in severe cases who often presented late , never mentioning the occurrence of oseltamivir-resistant H7N9  and H3N2  strains further worsened the situation. Thus, the next-generation therapeutic strategy against novel influenza virus is urgently required. Gammadelta-T cells represents for a minor subpopulation (1~3%) of human peripheral blood T cells but a major components of mucosal immune system. Being an important member of innate immunity, gammadelta-T cells are capable of recognizing multiple dangerous signals  caused by infectious pathogens such as respiratory syncytial virus (RSV), Mycobacterial bovis, and cytomegalovirus (CMV) derived signals [10-12], extrinsic or intrinsic signal substances such as phosphoantigens , ligands for toll like receptor (TLR)  and hot shock protein (HSP)-related signals , and tumors [16-19] and response as cytolytic or cytokine-secreting cells, thus play important roles in immune defense and surveillance [20, 21]. Apart from direct pathogen or malignant cells-targeted functions, gammadelta-T cells also exhibit some regulatory capabilities on both innate immunity [22, 23] and adaptive immunity including T cell- and B cell-mediated immune responses [18, 24-26] through multiplex pathways , even being able to play as regulatory T cells [27-29] or potent antigen presenting cells (APC) [28, 30]. The percentage of gammadelta-T cells in the elderly were found to decrease with the aging , which might represent for one of crucial factors in their susceptibility to osteoporosis and other infectious or malignant diseases. On the other hand, the studies on applying human gammadelta-T cells in treating human diseases were blocked by their relatively scarcity in peripheral blood and the lack of appropriate animal models because the T cell receptors (TCR) diversity of murine gammadelta-T cells show great difference compared to that of human gammadelta-T cells [32, 33]. Recently, the usage of phosphoantigens and the establishment of immunodeficient mice reconstituted with human immune system shed the light in this field [34, 35]. Using phosphoantigens (IPP, HMBPP or Pamidronate) with or without IL-2, Vgamma9Vdelta2-T cells (Vγ9Vδ2-T), the main subset of human peripheral blood gammadelta-T cells, could be specifically expanded and activated both in vitro and in vivo at a large scale [36-38], and this favors their future application in treating human diseases in clinic. In our previous investigations, we used Pamidronate to expand Vγ9Vδ2-T cells for treating influenza virus infection and Epstein Barr virus (EBV)-induced B cell lymphoproliferative disease in humanized mice and obtained exciting outcomes [35, 39]. We also demonstrated that the therapeutic effects of pamidronate in treating influenza virus infection models were dependent on the expansion of Vγ9Vδ2-T cells, which not only limited the replication of influenza virus but also ameliorate the inflammation in respiratory tracts through down-regulating the accumulation of immune effector cells and the secretion of pro-inflammatory soluble factors in infected lungs . Most importantly, the safe use of pamidronate in treating osteoporosis in the elderly has been confirmed for decades  and the use of this "old drug" undoubtedly bring new hopes for those patients suffered from drug-resistant influenza virus infection. However, how the treatment of pamidronate affect the dynamics and composition of other immune cells and whether its effects will influence the generation of adaptive immunity against influenza virus remain unknown. Since the Phase I clinical trial of applying pamidronate in treating influenza virus-infected patients is to be carried out soon, the knowledge on the homeostasis of immune system following the treatment of pamidronate will be crucial and undoubtedly accelerate the clinical application of this novel therapy. Aims and Hypotheses to be Tested: Aim 1. To compare the dynamics and homeostasis of immune system in influenza virus-infected humanized mice receiving pamidronate treatment. We hypothesize that the treatment of pamidronate on influenza virus-infected humanized mice might modify the dynamics and homeostasis of local and systemic immune systems of sub-lethal influenza virus-infected humanized mice during the progress and recovery of diseases in a human Vγ9Vδ2-T cell-dependent manner. Aim 2. To compare the adaptive immunity against influenza-derived antigen in influenza virus-infected humanized mice receiving oseltamivir and pamidronate. We hypothesize that both treatments of pamidronate and oseltamivir on sub-lethal influenza virus-infected humanized mice might modify the generation of adaptive immunity specific for antigen derived from influenza virus used for primary infections compared to untreated mice, while the adaptive immunity generated under the treatments of pamidronate and oseltamivir might demonstrate distinct characteristics.