ID Lecture 20: Intro to Virology & Viral Pathogens | Quizlet

How do viruses contradict the central dogma?

RNA --> DNA or RNA --> protein

What are the different components of a virus?

Nucleic acid genome

Capsid

Envelope

Capsid

protein shell that encloses the viral genome

can be helical or icosahedral

Envelope

lipid-containing membrane that surrounds some viruses

Nucleocapsid

capsid and nucleic acid together

Zoonotic viruses

viruses that jump from animal to human

Arbovirus

viruses spread by arthropods (mosquitos and ticks)

Central dogma

DNA -> RNA -> Protein

How is a + sense ss RNA virus replicated?

can be immediately translated into protein in the cytoplasm by host machinery upon entry because it is practically already mRNA

How is a - sense ss RNA virus replicated?

has to be copied into ds RNA so the + sense strand can serve as template before it can be translated into a protein through its own machinery

How is a ds RNA virus replicated?

has both + and - sense strands so it is able to follow the central dogma

How is a + ds DNA virus replicated?

Follows the central dogma

Transcription and replication happens in the nucleus

Translation occurs in the cytoplasm

How is a - ss RNA retrovirus replicated?

must go through a ds DNA intermediate first, then it follows the central dogma

How is a ss DNA virus replicated?

Gets copied to ds DNA in the nucleus first, then it goes to the cytoplasm for translation

What are the general steps of viral replication?

1. Attachment/Entry

2. Replication

3. Release

Describe the steps of viral entry.

Attachment

Endocytosis/Fusion

Uncoating/Penetration

Viral attachment

ALL VIRUSES bind to cell surface receptors

What happens during Endocytosis of viral entry?

cell-mediates the uptake of the virus

What happens during fusion of viral entry?

virus fuses with the host's cell membrane before, during, or after endocytosis

What happens during uncoating/penetration of viral entry?

removal of the viral genome from its capsid

Which types of viruses undergo fusion when entering a cell?

enveloped viruses

Where are DNA viruses replicated?

Nucleus for transcription and cytoplasm for translation

Where are RNA viruses replicated?

everything occurs in the cytoplasm

How does a ss RNA retrovirus replicate?

Could translate immediately in the cytoplasm or nucleus and code for its own DNA-dependent RNA polymerase

Describe the process of viral replication once it enters the host cell.

capsid releases genes, which typically gene for structural proteins to make more capsids via polyprotein processing

What is polyprotein processing?

virus mRNA is translated into a single giant polypeptide that is post-translationally cleaved by proteases into several smaller mature polypeptides

How are enveloped viruses released from a host cell?

the nucleocapsid will "bud" through the host membrane where virus-specific proteins have been placed during replication

How are naked viruses released from a host cell?

lysis

Viral load

how much virus an infected individual produces

low load = low transmission

What are the general steps of viral pathogenesis?

1. Infection

2. Virus travels to lymph nodes

3. Virus goes into the bloodstream to travel to bone marrow, liver, spleen, or blood vessles (primary viremia)

4. Virus returns to the blood stream to an area it is able to be shed (mucous membranes, skin, lungs, etc) (secondary viremia)

How do viruses evade the host immune response?

Mutations

Recombination

Latent infections

Target the host's cytokines

What is the general approach to viral chemotherapy?

Target processes in the virus that are NOT present in the host cell

OR

Target a mechanism that is significantly increased by viral infection

What are the different antiviral drug targets?

Viral polymerase inhibitors

Reverse transcriptase inhibitors

Protease inhibitors

Integrase inhibitors

Fusion inhibitors

Inhibitors or viral uncoating

Inhibitors of viral relase

True or false: A (+) ssRNA virus must enter the nucleus to initiate viral replication.

False

True or false: A dsDNA virus must enter the nucleus to initiate viral replication.

True

All the following are ways the viruses evade the immune system EXCEPT:

A. Interfere with the host's ability to secrete IFNs

B. Antigenic shift

C. By integrating their viral genomes into host RNA

D. By mutating proteins that are part of the nucleocapsid

C. By integrating their viral genomes into host RNA

Which part of the viral infection life cycle would most likely be affected by an inhibitor that targets V-ATPses involved in endosome fusion?

Viral entry (attachment and uncoating)

Picornavirus

Polio virus

Flavivirdae

Zika virus

Rhabdoviridae

Rabies virus

Filoviridae

Ebola virus

Paramyxoviridae

Measles and mumps virus

Orthomyxoviridae

Influenza virus

Retroviridae

HIV

Papillomaviridae

HPV

Hepadnaviridae

Hepatitis B virus

Herpesviridae

Chicken pox virus

Poxviridae

small pox virus