Animal Replication Flashcards
tropism
specificity of a virus to a particular tissue/cell type
Animal Virus Entry
fusion
some enveloped viruses leave their envelopes at the host cell membrane during entry or at the endosome following receptor mediated endocytosis
Animal Virus Entry
receptor mediated endocytosis
membrane invagination pulls the virus into the cell in an endosome
Animal Virus Entry
uncoating
process of removing the nucleocapsid can occur due to enzymes/pH changes in the endosome or following the escape from the endosome
Animal Virus Release: Budding and lysis
host cell lysis
viral proteins puncture the host plasma membrane
Animal Virus Release: Budding and lysis
budding
often occurs at the same time as envelope formation
Double-Stranded (ds) DNA virus synthesis
tegument
layer of proteins between nucleocapsid and envelope
Double-Stranded (ds) DNA virus synthesis
productive infection
lyse cell releasing 50,000 - 200,000 virions
Double-Stranded (ds) DNA virus synthesis
latent infection
- virions are undetected can be reactivated after months/years
- different than a chronic infection
Double-Stranded (ds) DNA virus synthesis
chronic infection
a slow increase in viral load
Understanding RNA Viruses
Sense (+) RNA strands
can be used as mRNA
Understanding RNA Viruses
Anti-Sense (-) RNA strands
must be transcribed into sense (+) RNA prior to translation, serve as the template for sense (+) synthesis
Understanding RNA Viruses
RNA-dependent RNA polymerase
almost all RNA viruses (except retroviruses) require a virally encoded enzyme to transcribe and replicate RNA
Understanding RNA Viruses
replicase
RdRp that replicates a viral RNA genome (more error prone than DdDp)
Understanding RNA Viruses
transcriptase
an RdRp that synthesizes mRNA
Sense (+) RNA Virus Synthesis
nonstructural proteins (NSP)
include enzymes for viral processes
Sense (+) RNA Virus Synthesis
structural proteins (SP)
include spike proteins
Sense (+) RNA Virus Synthesis
accessory proteins (AP)
involved in interfering with cellular processes and the innate immune response
Sense (+) RNA Virus Synthesis
spike glycoprotein
associates with the ACE2 receptor and is cleaved to induce fusion
Antisense (-) RNA Virus Synthesis
hemagluttinin spikes (HA)
attaches to sialic acid moieties linked to glycoproteins and glycolipids on cells in teh respiratory epithelium
Antisense (-) RNA Virus Synthesis
neuraminidase spike (NA)
facilitates induction of receptor mediated endocytoosis and separation of the virus from the host cell during budding
Retrosviruses
reversetranscriptase (RT)
- converts ssRNA into dsDNA
- functions as RpDp, DdDp, and a ribonuclease
Retroviruses
integrase
inserts viral dsDNA into the host chromosome
dsDNA Virus
Location of Nucleic Acid Synthesis.
nucleus
dsDNA Virus
Steps of viral nucleic acid synthesis.
dsDNA –> dsDNA
dsDNA Virus
Steps of viral protein synthesis.
dsDNA –> mRNA –> protein
dsDNA Virus
Special viral enzymes involved.
N/A (usually)
dsRNA Virus
Location of nucleic acid synthesis.
cytoplasm
dsRNA Virus
Steps of viral nucleic acid synthesis.
dsRNA –> ssRNA –> dsRNA
dsRNA Virus
Steps of viral protein synthesis.
dsRNA –> mRNA –> protein
dsRNA Virus
Special viral enzymes involved.
RNA-dependent RNA polymerase (RdRp)
+ssRNA Virus
Location of nucleic acid synthesis.
cytoplasm
+ssRNA Virus
Steps in viral nucleic acid synthesis.
+RNA –> -RNA –> +RNA
+ssRNA Virus
Steps of viral protein synthesis.
+RNA –> Protein
+RNA –> -RNA –> +RNA –> Protein
+ssRNA Virus
Special viral enzymes involved.
RNA-dependent RNA polymerase (RdRp)
-ssRNA Virus
Location of nucleic acid synthesis
cytoplasm
- influenza goes into the nucleus
-ssRNA Virus
Steps of viral nucleic acid synthesis.
-RNA –> +RNA –> -RNA
-ssRNA Virus
Steps of viral protein synthesis.
-RNA –> mRNA –> protein
-ssRNA Virus
Special viral enzymes involved.
RNA-dependent RNA polymerase (RdRp)
Retrovirus
Location of nucleic acid synthesis.
RNA –> DNA = cytoplasm
DNA integration = nucleus
Retrovirus
Steps of viral nucleic acid synthesis.
+RNA –> ssDNA –> dsDNA –> +RNA
Retrovirus
Steps of viral protein synthesis.
DNA –> mRNA –> protein
Retrovirus
Special viral enzymes involved.
- reverse transcriptase
- integrase
Detrimental Outcomes of Viral Infection in Animals
cytocidal infection
disease in which some of the symptoms result from cell death
Detrimental Outcomes of Viral Infection in Animals
persistent/chronic infection
the cell is not lysed but instead remains a viral factory
Detrimental Outcomes of Viral Infection in Animals
cytopathic effects (CPEs)
micorscopic or macroscopic changes or abnormalities in host cells and tissues that are distinct from lyses
Detrimental Outcomes of Viral Infection in Animals
latency
viral genomes can be maintained in cells without virion production as proviruses or extrachromasomal elements
Detrimental Outcomes of Viral Infection in Animals
oncogenic
capable of inducing cancer
Detrimental Outcomes of Viral Infection in Animals
cytokines
soluble, low molecular weight protein or glycoprotein that acts as an intercellular signaling molecule
Detrimental Outcomes of Viral Infection in Animals
cytokine storms
proinflammatory cytokines cause dilation of blood vessels that cause a rapid drop on blood pressure leading to shock
How Do We Fight Viral Infections?
innate immunity
parts of the immune response that:
- has no memory
- is non-specific
- doesn’t improve due to previous infection
How Do We Fight Viral Infections?: Innate Immunity
complement proteins
can surround viruses in a process called opsonization promoting phagocytosis and disrupt viral enzymes
How Do We Fight Viral Infections?: Innate Immunity
Natural Killer (NK) cells
destroy virally infected cells by inducing apoptosis
- looks for absence of MHC I self-recognition signal on cells
How Do We Fight Viral Infections?: Innate Immunity
Interferons
cytokines produced by infected cells which induce expression of anti-viral pathways in neighboring cells
How Do We Fight Viral Infections?
adaptive immunity
parts of the immune response that:
- are specific to a particular pathogen
- induce memory response
- improve due to previous infection
How Do We Fight Viral Infections?: Adaptive Immunity
neutralizing antibodies
proteins that bind to antigens, can block attachment of a virus to host cells and tag the cirus for destruction by phagocytes
How Do We Fight Viral Infections?: Adaptive Immunity
cytotoxic T cells
interact with MHC I self recognition signals to ‘check’ cellular trash for signs of abnormalities, inducing apoptosis in infected and cancerous cells
How Do We Fight Viral Infections?
neuraminidase inhibitors
treat influeanze by inhibiting the enzymatic activity of NA spikes, which aid in envelop separation
How Do We Fight Viral Infections?
nucleoside or mononucleotide analogues
inhibit DNA viruses which use their own enzyme to phosphorylate nucleotides
How Do We Fight Viral Infections?
Nucleoside reverse transcriptase inhibitors (NRTIs)
inhibit retroviruses through incorporation into DNA during reverse transcriptase which halts synthesis
How Do We Fight Viral Infections?
Nonnucleotide reverse transcriptase inhibitors (NNRTIs)
prevent DNA synthesis by binding to and inhibiting reverse transcriptase
How Do We Fight Viral Infections?
protease inhibitors
block HIV protease which is required for viral protein production
How Do We Fight Viral Infections?
integrase inhibitors
inhibit DNA incorporation into genome
How Do We Fight Viral Infections?
fusion inhibitors
prevent entry
