The poly-␥-D-glutamic acid (PGA) capsule is one of the major virulence factors of Bacillus anthracis, which causes a highly lethal infectious disease. The PGA capsule disguises B. anthracis from immune surveillance and allows its unimpeded growth in the host. The PGA capsule recently was reported to be associated with lethal toxin (LT) in the blood of experimentally infected animals (M. H. Cho, et al., Infect. Immun. 78:387-392, 2010). The effect of PGA, either alone or in combination with LT, on macrophages, which play an important role in the progression of anthrax disease, has not been thoroughly investigated. In this study, we investigated the effect of PGA on LT cytotoxicity using the mouse macrophage cell line J774A.1. PGA produced a concentrationdependent enhancement of the cytotoxicity of LT on J774A.1 cells through an enhancement in the binding and accumulation of protective antigen to its receptors. The increase of LT activity was confirmed using Western blot analysis, which showed that the combination of PGA and LT produced a greater degree of degradation of mitogen-activated protein kinase kinases and an increased level of the activation of the proform of caspase-1 to its processed form compared to the effects of LT alone. In addition, mice that received a tail vein injection of both PGA and LT had a significantly increased rate of death compared to that of mice injected with LT alone. PGA had no effect when added to cultures or administered to mice in the absence of LT. These results emphasize the importance of PGA in the pathogenesis of anthrax infection.

Although the conditions for inducing virulence protein expression in vitro are different, both classical and El Tor biotypes of Vibrio cholerae have been reported to regulate the expression of virulence proteins such as cholera toxin (CT) and toxin-coregulated pili (Tcp) through the ToxR/S/T system. The transcription activator ToxR responds to environmental stimuli such as pH and temperature and activates the second transcriptional regulator ToxT, which upregulates expression of virulence proteins. In addition to the ToxR/S/T signalling system, V. cholerae has been proposed to utilize another two-component system VarS/VarA to modulate expression of virulence genes. Previous study has shown that VarA of the VarS/VarA system is involved in the regulation of virulence proteins in the classical V. cholerae O395 strain; however, no further analysis was performed concerning VarS. In this study, we constructed varS mutants derived from the classical O395 and El Tor C6706 strains and demonstrated that VarS is also involved in the expression of the virulence proteins CT and Tcp from the V. cholerae classical and El Tor strains. This expression is through regulation of ToxT expression in response to environmental changes due to different toxin-inducing conditions.

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Zika virus (ZIKV) (genus Flavivirus, family Flaviviridae) is an emerging pathogen associated with microcephaly and Guillain-Barré syndrome. The rapid spread of ZIKV disease in over 60 countries and the large numbers of travel-associated cases have caused worldwide concern. Thus, intensified surveillance of cases among immigrants and tourists from ZIKV-endemic areas is important for disease control and prevention. In this study, using Next Generation Sequencing, we reported the first whole-genome sequence of ZIKV strain AFMC-U, amplified from the urine of a traveler returning to Korea from the Philippines. Phylogenetic analysis showed geographic-specific clustering. Our results underscore the importance of examining urine in the diagnosis of ZIKV infection.