General Characteristics of Viruses

       Obligatory intracellular parasites

       Contain DNA or RNA

       Contain a protein coat

       Some are enclosed by an envelope

       Some viruses have spikes

       Most viruses infect only specific types of cells in one host

       Host range is determined by specific host attachment sites and cellular factors

 

Virion Structure

       Virion

      Complete virus

       Nucleic acid

      DNA or RNA

       Capsid

      Capsomeres

       Envelope

      Membrane

       Spikes

      Glycoproteins

 

Virus Morphology

      Helical

      Polyhedral

      Enveloped

       Enveloped helical

       Enveloped polyhedral

      Complex

 

Taxonomy of Viruses

       Family names end in -viridae.

       Genus names end in -virus.

       Viral species: A group of viruses sharing the same genetic information and ecological niche (host). Common names are used for species.

       Subspecies are designated by a number.

 

       Herpesviridae

      Herpesvirus

       Human herpes virus; HHV-1, HHV-2, HHV-3

 

       Retroviridae

      Lentivirus

       Human immunodeficiency virus HIV-1, HIV-2

 

Picornaviridae

       Single-stranded RNA,  + strand, nonenveloped

      Enterovirus

       Poliovirus and coxsackievirus

      Rhinovirus

      Hepatitis A virus

 

Orthomyxoviridae

       Single-stranded RNA,  – strand, multiple RNA strands

      Envelope spikes can agglutinate RBCs

      Influenzavirus (influenza viruses A and B)

      Influenza C virus

 

Retroviridae

       Single-stranded RNA, 2 RNA strands, produce DNA

      Use reverse transcriptase to produce DNA from viral genome

      Lentivirus (HIV)

      Oncogenic viruses

       Includes all RNA tumor viruses