Viral Pathogens Flashcards
Describe virus coat/capsid, nucleocapsid, nucleocapsid symmetry, virus particle/virion, enveloped virus and envelope-free viruses.
Capsid: protein shell
Nucleocapsid: nucleic acid plus the capsid
Nucleocapsid symmetry: virus capsids have symmetrical faces (ex. icosahedral, helical or complex)
Virion: virus particle (virus outside of a host cell)
Enveloped Virus: a virus with nucleocapsid surrounded by a glycoprotein lipid bilayer
Envelope-free virus: virus without lipid bilayer and glycoproteins
Explain routes by which viruses enter the body and the most common forms of virus transmission.
Inhalation, orally, sexually, direct skin contact, trans placental. Most common infections from digestive, respiratory, and reproductive mucosa.
Explain key elements in virus infection of host cells including virus attachment/adsorption, virus receptors, host specificity and viral entry.
Viral ligands bind to host cell receptors. Viruses can induce endocytosis and then fuse with endosomal bilayer, fuse directly to the membrane lipid bilayer or (nucleic acid translocation) inject nucleic acid into the cell while leaving capsid outside
Explain the process of virus replication including synthesis of virus mRNA, translation and processing of virus proteins, replication of virus nucleic acid and the assembly and release of virus particles.
Viruses first begin transcription of their nucleic acid and then translation. They bring some of their own proteins that are needed. They have one promoter site thus make one large poly peptide segment and cleave it into individual proteins. The capsid is then assembled around the newly formed proteins and nucleic acid and leave the cell either through lysis or budding which takes a piece of the cells membrane with it as an envelope only after the glycoproteins are inserted.
Compare and contrast the mechanisms by which dsRNA viruses, positive and negative sense ssRNA viruses and retroviruses synthesize mRNA and replicate genomic RNA.
A DNA virus has to have the negative strand transcribed into a positive mRNA strand. dsRNA viruses have their negative strand transcribed into a positive strand. ssRNA viruses only transcribe if they contain a negative strand into a positive strand. Retroviruses have to transcribe their positive strand to a negative DNA strand then replicating a complimentary DNA positive strand the negative strand is then transcribed to a positive mRNA.
Compare and contrast lytic, persistent and latent viral infections.
Lytic: cell dies
Persistent: cell enslaved by virus
Latent: dormant viral genome-no viral replication
Explain the mechanisms of viral oncogenes and the process by which viruses can transform host cells into cancer cells.
Oncogenes are proto-oncogenes that are mutated by removal of a stop signal in the genome. Viruses do this to keep the cell in active mitosis
Explain latent infection of herpesviruses
Herpesvirus hides in the trigeminal cranial nerve and is constantly suppressed. However, when host is immunocompromised it is able to make its way down the nerve and infect cells of the lips.
Identify the clinical and laboratory manifestations of HSV
HSV: clinically seen as cold sores, laboratory can be seen in Tzanck test
