PHSC1312 Microbiology/Immunology Lecture 11 Intro to Viruses

virion

another name for a viral particle

nucleic acids, proteins, possibly an envelope

What does a virion contain inside a nucleocapsid?

virus

nonliving, obligate intracellular parasites

need host cells for replication

What makes viruses obligate intracellular parasites?

wide host range

characteristic of viruses where there is a diversity of species they can infect

nucleic acids, spike glycoproteins, capsid, nucleocapsid

parts of a virus structure

spike glycoproteins

help with attachment and entry of host by viruses

which cell types can be infected

What do spike glycoproteins tend to limit for viruses?

protective coat

What is the viral capsid?

nucleocapsid

part of a virus made up of nucleic acid and the capsid proteins around it

nucleic acid and the capsid proteins around it

What makes up a nucleocapsid?

nucleic acid, envelope, shape of nucleic acid

three main parts to general viral classification

DNA or RNA, single or double stranded

How can viral nucleic acid be classified?

linear or circular, positive or negative sense

How can the shape of viral nucleic acid be classified?

single stranded RNA

What is positive and negative sense exclusively describing?

5' to 3'

What direction does +sense single-stranded RNA go?

3' to 5'

What direction does -sense single-stranded RNA go?

nucleus

Where do DNA viruses have to go inside a host cell?

cytosol

Where do RNA viruses have to go inside a host cell?

attachment, penetration, uncoating, early transcription, early translation, DNA synthesis and late transcription, late translation, assembly, release and lysis

9 steps to viral pathogenesis

virus enters host cell

What happens during viral penetration?

proteins disassemble for nucleic acid accessibility

What happens during uncoating?

synthesis of early mRNA

What happens during early transcription?

synthesis of early proteins

What happens during early translation?

enzymes such as DNA polymerase

What might be synthesized as an early protein during early translation?

synthesis of progeny viral DNA and late mRNA

What happens during viral DNA synthesis and late transcription?

synthesis of late proteins like capsid proteins

What happens during late translation?

respiratory tract, mouth, intestinal tract, skin including mild trauma, injection, and bites

routes of viral infection

mild trauma, injection, bites

three types of routes of viral infection using the skin

halt new virus production and spread

goal of antiviral agents

nucleoside and nucleotide analogs, non nucleoside reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors

four examples of antiviral mechanisms

nucleoside and nucleotide analogs

synthetic, modified molecules that mimic natural building blocks of DNA and RNA; work by interfering with viral or cancer cell replication

non nucleoside reverse transcriptase inhibitors

a class of antiretroviral drugs used to treat HIV by directly binding to and blocking the action of the HIV reverse transcriptase enzyme

protease inhibitors

a class of drugs that inhibit the activity of enzymes to prevent viral protein synthesis

integrase inhibitors

a class of antiviral medications used to treat HIV infection; work by inhibiting an enzyme essential for the replication of HIV in host cells

virostatic

antiviral drugs are _____________

sub clinical levels of virus below a defined threshold without symptoms

What are we trying to achieve with antiviral agents?

viral attachment and entry

blocked by fusion and attachment inhibitors (HIV), docosanol (HSV), and palivizumab (RSV)

penetration

blocked by interferon (HBV, HCV)

uncoating

blocked by amantadine and rimantadine (influenza)

nucleic acid synthesis

blocked by NRTIs, NNRTIs (HIV), and nucleoside/nucleotide analogs (HSV, HBV)

integration transcription

blocked by INSTIs (HIV) and endonuclease inhibitors (influenza)

viral protein synthesis

blocked by PIs (HIV, HCV)

viral release

blocked by neuraminidase inhibitors (influenza)

primary and secondary

two types of immune response

first exposure

produces primary response, 7-10 days after activation, antibody titer measurable, class switching and plasma cell formation

primary response

What response does first exposure produce?

7-10 days after activation

How soon does the primary response occur?

amount of antibody in circulation

What can an antibody titer measure?

class switching and plasma cell formation

What happens with IgM and IgG and B cells in primary response?

second exposure

triggers secondary response 36-48 hours after activation, more extensive and prolonged, memory cells already primed

secondary response

What response does second exposure produce?

36-48 hours after activation

How soon does the secondary response occur?

more extensive and prolonged, memory cells already primed

What is different about second exposure and the secondary immune response?

active and passive

two types of immunity

active immunity

induced after contact or exposure to foreign antigens; full immune system activation; host actively produces antibodies; memory formation

passive immunity

administration of preformed antibodies; administration of antivenom, limited period of efficacy or protection, no long term memory

contact or exposure to foreign antigens

What induces active immunity?

host cells

produce antibodies in active immunity

full immune system activation and memory formation

stimulated in active immunity, but not in passive

preformed antibodies

What is administered to induce passive immunity?

artificial passive

What type of immunity does antivenom induce?

period of efficacy or protection

What is limited with passive immunity?

natural passive

What type of immunity is involved with antibodies from pregnancy or breast milk?

primary

What type of response is the goal with a vaccine?

IgM

first antibody

IgG

most abundant antibody in circulation

class switching

when B cells are changing and begin producing IgG in addition to IgM