iPS cell-derived model to study the interaction between tissue macrophage and HIV-1.

Despite effective antiretroviral therapy, HIV-1 persists in cells, including macrophages, which is an obstacle to cure. However, the precise role of macrophages in HIV-1 infection remains unclear because they reside in tissues that are not easily accessible. Monocyte-derived macrophages are widely used as a model in which peripheral blood monocytes are cultured and differentiated into macrophages. However, another model is needed because recent studies revealed that most macrophages in adult tissues originate from the yolk sac and fetal liver precursors rather than monocytes, and the embryonic macrophages possess a self-renewal (proliferating) capacity that monocyte-derived macrophages lack. Here, we show that human induced pluripotent stem cell-derived immortalized macrophage-like cells are a useful self-renewing macrophage model. They proliferate in a cytokine-dependent manner, retain macrophage functions, support HIV-1 replication, and exhibit infected monocyte-derived macrophage-like phenotypes, such as enhanced tunneling nanotube formation and cell motility, as well as resistance to a viral cytopathic effect. However, several differences are also observed between monocyte-derived macrophages and induced pluripotent stem cell-derived immortalized macrophage-like cells, most of which can be explained by the proliferation of induced pluripotent stem cell-derived immortalized macrophage-like cells. For instance, proviruses with large internal deletions, which increased over time in individuals receiving antiretroviral therapy, are enriched more rapidly in induced pluripotent stem cell-derived immortalized macrophage-like cells. Interestingly, inhibition of viral transcription by HIV-1-suppressing agents is more obvious in induced pluripotent stem cell-derived immortalized macrophage-like cells. Collectively, our present study proposes that the model of induced pluripotent stem cell-derived immortalized macrophage-like cells is suitable for mimicking the interplay between HIV-1 and self-renewing tissue macrophages, the newly recognized major population in most tissues that cannot be fully modeled by monocyte-derived macrophages alone.

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.

Human metapneumovirus infection in febrile children with lower respiratory diseases in primary care settings in Hiroshima, Japan.

Human metapneumovirus (hMPV) has been shown to be a leading cause of viral lower respiratory tract infections in children. Nevertheless, few reports regarding hMPV infections over consecutive years in children in primary care settings are available. We carried out virologic and clinical studies to determine the role of hMPV in febrile lower respiratory infections in children at a primary care clinic over 3 years and 5 months. Nasopharyngeal aspirates obtained from children with acute respiratory tract infections accompanied by high-grade fever (> or = 39 degrees C) and productive cough were studied for hMPV by reverse transcription-polymerase chain reaction and for other respiratory viruses by viral cultures and immunoassays. Of 379 patients tested, 202 were positive for at least 1 virus, including 98 with hMPV, 69 with respiratory syncytial virus, 18 with adenovirus, 12 with enterovirus, 8 with parainfluenza virus, 3 with rhinovirus, 2 with influenza virus type C, and 1 with herpes simplex virus. The male:female ratio of hMPV-infected children was 0.96:1 with an overall mean age of 3.5 years (range, 2 months to 9 years). These infections occurred predominantly from February to July, and the hospitalization rate was 4%. Of 93 patients infected with hMPV alone, 52 (56%) showed evidence of a lower respiratory tract infection.

Rapid detection of norovirus from fecal specimens by real-time reverse transcription-loop-mediated isothermal amplification assay.

In this study, we developed a one-step, single-tube genogroup-specific reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of norovirus (NoV) genomes targeting from the C terminus of the RNA-dependent RNA polymerase gene to the capsid N-terminal/shell domain region. This is the first report on the development of an RT-LAMP assay for the detection of NoV genomes. Because of the diversity of NoV genotypes, we used 9 and 13 specially designed primers containing mixed bases for genogroup I (GI) and II (GII), respectively. The RT-LAMP assay had the advantages of rapidity, simplicity, specificity, and selectively and could obtain results within 90 min, generally even within 60 min, under isothermal conditions at 62 degrees C. The detection limits for NoV genomes were between 10(2) and 10(3) copies/tube for GI and GII with differentiation by genotype, and no cross-reactions among NoV GI and GII and other gastroenteritis viruses, such as sapovirus, human astrovirus, adenovirus type 40 and 41, and group A and C rotavirus, were found. In the evaluation tests with fecal specimens obtained from gastroenteritis outbreaks, the sensitivity and specificity of the RT-LAMP assay with regard to RT-PCR were 100 and 94% for GI and 100 and 100% for GII, respectively. These findings establish that the RT-LAMP assay is potentially useful for the rapid detection of NoV genomes from fecal specimens in outbreaks of food-borne and person-to-person-transmitted gastroenteritis.