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Virulence factors are molecules produced by pathogens (bacteria, viruses, fungi and protozoa) that contribute to the pathogenicity of the organism and enable them to achieve the following: * colonization of a niche in the host (this includes attachment to cells) * immunoevasion, evasion of the host's immune response * immunosuppression, inhibition of the host's immune response * entry into and exit out of cells (if the pathogen is an intracellular one) * obtain nutrition from the host Specific pathogens possess a wide array of virulence factors. Some are chromosomally encoded and intrinsic to the bacteria (e.g. capsules and endotoxin), whereas others are obtained from mobile genetic elements like plasmids and bacteriophages (e.g. some exotoxins). Virulence factors encoded on mobile genetic elements spread through horizontal gene transfer, and can convert harmless bacteria into dangerous pathogens. Bacteria like ''Escherichia coli O157:H7'' gain the majority of their virulence from mobile genetic elements. Gram-negative bacteria secrete a variety of virulence factors at host-pathogen interface, via membrane vesicle trafficking as bacterial outer membrane vesicles for invasion, nutrition and other cell-cell communications. It has been found that many pathogens have converged on similar virulence factors to battle against eukaryotic host defenses. These obtained bacterial virulence factors have two different routes used to help them survive and grow: * The factors are used to assist and promote colonization of the host. These factors include adhesins, invasins, and antiphagocytic factors * The factors, including toxins, hemolysins, and proteases, bring damage to the host ==Attachment, immunoevasion, and immunosuppression== Bacteria produce various adhesins including lipoteichoic acid, trimeric autotransporter adhesins and a wide variety of other surface proteins to attach to host tissue. Capsules, made of carbohydrate, form part of the outer structure of many bacterial cells including ''Neisseria meningitidis''. Capsules play important roles in immune evasion, as they inhibit phagocytosis, as well as protecting the bacteria while outside the host. Another group of virulence factors possessed by bacteria are immunoglobulin (Ig) proteases. Immunoglobulins are antibodies expressed and secreted by hosts in response to an infection. These immunoglobulins play a major role in destruction of the pathogen through mechanisms such as opsonization. Some bacteria, such as ''Streptococcus pyogenes'', are able to break down the host's immunoglobulins using proteases. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Virulence factors are molecules produced by pathogens (bacteria, viruses, fungi and protozoa) that contribute to the pathogenicity of the organism and enable them to achieve the following:* colonization of a niche in the host (this includes attachment to cells) * immunoevasion, evasion of the host's immune response* immunosuppression, inhibition of the host's immune response* entry into and exit out of cells (if the pathogen is an intracellular one)* obtain nutrition from the hostSpecific pathogens possess a wide array of virulence factors. Some are chromosomally encoded and intrinsic to the bacteria (e.g. capsules and endotoxin), whereas others are obtained from mobile genetic elements like plasmids and bacteriophages (e.g. some exotoxins). Virulence factors encoded on mobile genetic elements spread through horizontal gene transfer, and can convert harmless bacteria into dangerous pathogens. Bacteria like ''Escherichia coli O157:H7'' gain the majority of their virulence from mobile genetic elements. Gram-negative bacteria secrete a variety of virulence factors at host-pathogen interface, via membrane vesicle trafficking as bacterial outer membrane vesicles for invasion, nutrition and other cell-cell communications. It has been found that many pathogens have converged on similar virulence factors to battle against eukaryotic host defenses. These obtained bacterial virulence factors have two different routes used to help them survive and grow:* The factors are used to assist and promote colonization of the host. These factors include adhesins, invasins, and antiphagocytic factors* The factors, including toxins, hemolysins, and proteases, bring damage to the host==Attachment, immunoevasion, and immunosuppression==Bacteria produce various adhesins including lipoteichoic acid, trimeric autotransporter adhesins and a wide variety of other surface proteins to attach to host tissue. Capsules, made of carbohydrate, form part of the outer structure of many bacterial cells including ''Neisseria meningitidis''. Capsules play important roles in immune evasion, as they inhibit phagocytosis, as well as protecting the bacteria while outside the host.Another group of virulence factors possessed by bacteria are immunoglobulin (Ig) proteases. Immunoglobulins are antibodies expressed and secreted by hosts in response to an infection. These immunoglobulins play a major role in destruction of the pathogen through mechanisms such as opsonization. Some bacteria, such as ''Streptococcus pyogenes'', are able to break down the host's immunoglobulins using proteases.」の詳細全文を読む スポンサード リンク
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