NK cells are a relatively rare cell population in peripheral lymphoid organs but are abundant in the liver, raising questions as to their function in immune responses to infections of this organ. To investigate this, cell-mediated immunity to viral liver infection induced by a type 5, replication-defective, adenovirus was examined. It is shown that NK cells in the absence of T cells cause hepatocyte apoptosis in virus-infected livers associated with an increase in liver enzymes in the serum. Concomitantly, NK cells induce production of IFN-γ, inhibitable by their elimination before infection. NK cells are shown to be necessary for optimal priming of virus-specific T cells, assessed by delayed-type hypersensitivity response and CTL activity, consistent with their ability to secrete IFN-γ. The conclusion is drawn that NK cells mediate two important functions in the liver: they induce cell death in the infected organ and concomitantly stimulate the induction of T cell-mediated immunity by release of IFN-γ.

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The apparent worldwide resurgence of invasive Streptococcus pyogenes infection in the last two decades remains unexplained. At present, animal models in which toxic shock-like syndrome or necrotizing fasciitis is induced after S. pyogenes infection are not well developed. We demonstrate here that infection with a nonlethal dose of influenza A virus 2 days before intranasal infection with a nonlethal dose of S. pyogenes strains led to a death rate of more than 90% in mice, 10% of which showed necrotizing fasciitis. Infection of lung alveolar epithelial cells by the influenza A virus resulted in viral hemagglutinin expression on the cell surface and promoted internalization of S. pyogenes. However, treatment with monoclonal antibodies to hemagglutinin markedly decreased this internalization. Our results indicate that prior infection with influenza A virus induces a lethal synergism, resulting in the induction of invasive S. pyogenes infection in mice.

The swabbing and tape-stripping methods have traditionally been used for collecting skin microbiome samples for skin bacterial analysis, although no reports have compared the outcome of these methods for collecting skin bacteria. Our purpose was to show the differences in microbial composition between samples collected using the swabbing and tape-stripping methods, by both the next generation sequencing and culture studies. The skin microbiome was collected by both methods, and the samples were processed for a sequence-based microbiome analysis and culture study. The next-generation sequencing results showed that skin bacteria collected using the tape-stripping method were comparable to those collected using the swabbing method. In the culture study, the tape-stripping method collected a greater number and wider variety of viable skin bacteria than the swabbing method. These results suggest that the tape-stripping method is comparable to the swabbing method for collecting viable skin bacteria, without losing fidelity to the composition of skin microbiome.

Cell-mediated immunity (CMI) has been shown to be critical for the prevention and control of varicella-zoster virus (VZV)-related diseases. Because a large population-based study has revealed that diabetes mellitus is a risk factor for herpes zoster, we studied VZV-specific immune responses of patients with diabetes mellitus and compared them with those of healthy individuals. In this study, we found that patients with diabetes mellitus had significantly lower CMI to VZV than did healthy individuals. These results suggest that the increased risk for herpes zoster among patients with diabetes mellitus may be related to decreased VZV-specific CMI.