An Ecological Framework of the Human Virome Provides Classification of Current Knowledge and Identifies Areas of Forthcoming Discovery

Parker, Michael T.

Some commensal viruses can infect human cells and use the human as a vessel for transmission. These viruses establish asymptomatic infections that do not result in a change in host health or behavior. This represents a veritable antithesis to the strategy of parasitic human viruses (see The Parasitic Virome, above), wherein viruses have prioritized trade-offs other than pathogenicity to ensure their transmission to a new host. The most well documented examples of asymptomatic infection of humans by commensal viruses are the rhinoviruses and other infections of the nasopharynx and upper respiratory tract [80, [101] [102] [103] [104] . Many of the Human Papilloma Viruses (HPVs) interact with human cells as an asymptomatic infection of mucous membranes or skin [105] . Anelloviruses are also well described human commensals [106] [107] [108] [109] [110] . While immune detection of non-human tropic commensal viruses is avoided by physical separation, the human-tropic commensal viruses assuredly engage with host innate and adaptive immune responses, and so must avoid or subvert these mechanisms to maintain their immunological silence. Description of the viral techniques enabling this evasion is an important direction for future research on these viruses, as this may point to novel avenues of therapeutic intervention for suppression or activation of immune responses.