envelopevirukset

Enveloped viruses, or envelopeviruses, are a broad group of viruses that possess a lipid envelope surrounding their protein capsid. The envelope is derived from host cell membranes during budding and contains viral glycoproteins essential for attachment to and entry into susceptible cells. The envelope’s lipid nature makes these viruses sensitive to desiccation, heat, and detergents, affecting their environmental stability and modes of transmission.

The genome of enveloped viruses is contained within a nucleocapsid that lies inside the envelope. The envelope is studded with glycoproteins that mediate receptor binding and membrane fusion. Entry typically occurs by attachment to a cellular receptor followed by fusion of the viral envelope with the host membrane, either at the plasma membrane or after endocytosis and acid-triggered fusion. After uncoating, the viral genome is replicated and expressed using the host cell machinery, and new virions assemble at cellular membranes and bud through the envelope, acquiring their outer layer.

Because of their lipid envelopes, enveloped viruses are generally more susceptible to environmental inactivation than non-enveloped viruses, but many spread efficiently through respiratory secretions, blood, or body fluids, and some employ arthropod vectors. Antiviral strategies often target envelope proteins to block attachment or fusion, and vaccines frequently aim to elicit neutralizing antibodies against envelope glycoproteins.

Examples of enveloped viruses include influenza viruses (orthomyxoviruses), coronaviruses, herpesviruses, flaviviruses such as dengue and Zika, and retroviruses such as HIV. The diversity of envelope viruses reflects a common strategy of using a host-derived membrane to enter cells, with varying receptor specificities and replication strategies.