Acanthamoeba polyphaga mimivirus, the first discovered giant virus with genome size and particle size much larger than previously discovered viruses, possesses several genes for translation and CRISPER Cas system-like defense mechanism against virophages, which co-infect amoeba cells with the giant virus and which inhibit giant virus proliferation. Mimiviruses infect amoeba cells by phagocytosis and release their DNA into amoeba cytoplasm through their stargate structure. After infection, giant virion factories (VFs) form in amoeba cytoplasm, followed by DNA replication and particle formation at peripheral regions of VF. Marseilleviruses, the smallest giant viruses, infect amoeba cells by phagocytosis or endocytosis, form larger VF than Mimivirus's VF in amoeba cytoplasm, and replicate their particles. Pandoraviruses found in 2013 have the largest genome size and particle size among all viruses ever found. Pandoraviruses infect amoeba cells by phagocytosis and release their DNA into amoeba cytoplasm through their mouth-like apical pores. The proliferation of Pandoraviruses occurs along with nucleus disruption. New virions form at the periphery of the region formerly occupied by the amoeba cell nucleus.
Feline morbillivirus (FeMV) is an emerging virus that was first discovered in Hong Kong in 2012. FeMV is epidemiologically associated with kidney and other lower urinary tract diseases in cats. Phylogenetic analysis of its genome sequence indicates that FeMV is the most closely related to the members of genus morbillivirus, although FeMV is relatively distant in the phylogenetic analysis, and its target tissues and pathogenicity are different from the other members of the genus. The origin and routes of dissemination of FeMV are not clear since genetic types are not always correlated to the geographical distribution of the isolates. Since the discovery of the virus, several reports showed the epidemiological association of FeMV infection with kidney and lower urinary tract diseases in cats. However, the pathogenicity of FeMV is not clear yet due to paucity of the isolated virus strains and chronic nature of the subjected diseases. Diagnosis of FeMV infection has been performed using both nucleic acid and serological methods. However, there are no standard diagnostic methods to detect antibodies against FeMV, which will be useful to study epidemiology and pathogenicity of FeMV. Besides FeMV is an interesting subject as an additional member to the morbilliviruses possessing unusual characteristics comparing to the other morbilliviruses, further studies of FeMV is important in the veterinary field since it may lead to new therapies or prevention of chronic kidney diseases of cats.
Special Issue 1: Introduction of “Neo-virology”, the new Grant-in-Aid for Scientific Research on Innovative Areas
An ecosystem is a complex network of interactions among living organisms and the nonliving components of their environment. Generally, a living organism is defined as belonging to one of three domains of life: the archaea, bacteria, and eukaryote domains. Therefore, viruses are not considered living components of the global ecosystem. Given that approximately 1031 viruses exist on Earth and all of them are parasitic in living organisms, it is not hard to imagine how virus infection might affect the physiological functions of both hosts and the ecosystem. However, since traditional virology research tends to focus on viral pathogenicity, the significance of viruses and viral-mediated processes in the global ecosystem are poorly understood. To identify previously unrecognized roles of the virus per se in nature, here we propose to establish a new academic field designated as 'Neo-virology'. In this research field, we define a virus as a component of the global ecosystem and aim to elucidate its key roles in host organisms as a part of the global ecosystem.
Special Issue 2: Viruses in the environment of modern society
Development of PCR method had a great impact on studies on viruses in water environment, and now it makes possible to determine various kind of viruses from river, marine water and water/wastewater treatment systems, though there are still needs to improve accuracy of quantification. Now we know that river water may contain 1000copy/L of norovirus. The infectious risk management for recreational water has been left and not updated, hence we need develop better management system based on scientific knowledge.
Environmental DNA analysis for micro- and macro-organisms is rapidly developing. Environmental DNA means total DNA present in environmental media such as water or soil, and includes DNA contained in the organisms themselves and extra-organism DNA of macro-organisms. Analysis of environmental DNA can be divided into two methods, species-specific detection and meta-barcoding, which can be used according to each purpose. Applicable subjects are all organisms (including viruses in this case) with DNA as genes, and application to rivers, ponds, lakes and marines has been reported. In this paper, the present situation of environmental DNA analysis of macro organisms is described, and the possibility of application to infectious disease studies and the problems to be solved are discussed.
Gastroenteritis virises, including human norovirus and rotavirus, are transmitted not only through humans but also via contaminated water, foods and environmental fomites such as door knob. It is thus important to disinfect these contaminated stuffs for controlling infectious diseases caused by gastroenteritis viruses. The author of this article has been investigating histo-blood group antigen (HBGA)-positive bacteria as a possible environmental vehicle of human norovirus and rotavirus. In this article, recent publications related to the effect of HBGA-positive bacteria on the life cycles of gastroenteritsi viruses are introduced.