iPS cell serves as a source of dendritic cells for in vitro dengue virus infection model

Dendritic cell differentiation from human induced pluripotent stem cells: challenges and progress

Dendritic cells (DCs) are the major antigen-presenting cells of the immune system responsible for initiating and coordinating immune responses. These abilities provide potential for several clinical applications, such as the development of immunogenic vaccines. However, difficulty in obtaining DCs from conventional sources, such as bone marrow (BM), peripheral blood (PBMC), and cord blood (CB), is a significantly hinders routine application. The use of human induced pluripotent stem cells (hiPSCs) is a valuable alternative for generating sufficient numbers of DCs to be used in basic and pre-clinical studies. Despite the many challenges that must be overcome to achieve an efficient protocol for obtaining the major DC types from hiPSCs, recent progress has been made. Here we review the current state of developing DCs from hiPSCs, as well as the key elements required to enable the routine use of hiPSC-derived DCs in pre-clinical and clinical assays.

The potential of COVID-19 patients' sera to cause antibody-dependent enhancement of infection and IL-6 production

Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), many vaccine trials have been initiated. An important goal of vaccination is the development of neutralizing antibody (Ab) against SARS-CoV-2. However, the possible induction of antibody-dependent enhancement (ADE) of infection, which is known for other coronaviruses and dengue virus infections, is a particular concern in vaccine development. Here, we demonstrated that human iPS cell-derived, immortalized, and ACE2- and TMPRSS2-expressing myeloid cell lines are useful as host cells for SARS-CoV-2 infection. The established cell lines were cloned and screened based on their function in terms of susceptibility to SARS-CoV-2-infection or IL-6 productivity. Using the resulting K-ML2 (AT) clone 35 for SARS-CoV-2-infection or its subclone 35–40 for IL-6 productivity, it was possible to evaluate the potential of sera from severe COVID-19 patients to cause ADE and to stimulate IL-6 production upon infection with SARS-CoV-2.

Dengue virus susceptibility in novel immortalized myeloid cells

Human dendritic cells (DCs) are the main target cells of dengue virus (DENV). Because humans injected with even a small volume of DENV from mosquito saliva display a high level of viremia, DCs are expected to be highly susceptible to DENV. In the present study, we assessed the efficiency of DENV infection using the novel immortalized human myeloid cell lines iPS-ML and iPS-DC. To prepare the DC-like myeloid cell line (iPS-DC), iPS-ML cells were cultured in the presence of IL-4 for 72 h. iPS-DC cells were the most susceptible to DENV, followed by iPS-ML, Vero and K562 cells. In contrast, the highest infective yield titer was observed in Vero cells. To investigate further uses of iPS-ML and iPS-DC, these cells were applied to an assay measuring antibody-dependent enhancement (ADE) activity in DENV infection. Serum samples collected from healthy Thai participants and mouse monoclonal antibodies displayed similar ADE activity patterns when examined with iPS-ML, iPS-DC, or K562 cells, the last of which are usually used in conventional ADE assays. Interestingly, iPS-ML cells showed greater susceptibility to ADE activity than iPS-DC and K562 cells. Here, we demonstrated the potential utility of the novel immortalized human myeloid cell lines iPS-ML and iPS-DC in future research on DENV.