Chapter #5 Virology Basics Brock 16th edition

capsid

protein coat that surrounds the nucleic acid in a viral particle (#2 on the figure)

negative stranded

single stranded (DNA or RNA) virus whose genetic code is the complement of the coding strand, not directly encoding proteins

transduction

Most common means of horizontal gene transfer in between bacterial cells. This method uses a virus to move genes from one cell to another

smallpox

highly infectious and deadly viral disease. it was the first virus immunized against and the first viral disease eradicated.

polio

viral disease that leads to temporary paralysis with potential for permanent damage to the body. it was widely vaccinated against and is no longer present in the US, but has not been eradicated.

viral nucleic acids

can be DNA, RNA, single stranded or double stranded

envelope

outer layer that some viruses have, made of lipids and proteins (typically derived from the host cell's cytoplasmic membrane)

positive stranded

single stranded (DNA or RNA) virus whose genetic code is the coding strand, directly encoding proteins

reverse transcriptase

virally encoded enzyme responsible for using an RNA template to make DNA

lysins

viral enzyme class (similar to lysozyme) that breaks down peptidoglycan by disrupting links between sugars

hemagglutinin

protein embedded in the envelope used by influenza to enter a cell (this is the H of H1N1)

neuraminidase

protein embedded in a viral envelope that is used by influenza to leave a cell (this is the N of H1N1)

RNA replicase

Enzyme present in RNA viruses that creates the dsRNA intermediate they need for proceeding through cycle (RNA-dependent RNA polymerase)

Tamiflu

antiviral flu drug that treats flu by blocking virus from exiting the cell (neuraminidase inhibitor)

Ribavirin

antiviral drug that induces extra mutations, which are already common, in RNA viruses during replication

bacteriophage

viruses which infect bacteria. they do not enter a bacterial cell, just inject their genetic material.

lytic life cycle

attachment, penetration, synthesis, assembly, release

attachment

virion fastens itself to bacterial cell

penetration

virion nucleic acid is injected into the cell

synthesis

virus nucleic acids and proteins are made by the host cell metabolism, which is being redirected by the virus

assembly

capsid forms and viral genome is packaged into new virions

release

mature virions exit the host cell

eclipse period

a period of time in which, if the infected cells are lysed, no viral particles will be found because all viruses are disassembled. (AKA latent period)

early enzymes

enzymes made at the beginning of the latent period that take over host cell machinery to facilitate viral reproduction

burst size

the number of viral particles that emerge upon release, assuming one virus acted per cell.

temperate phage

viruses that infect bacteria. These viruses insert their genome into the host chromosome as a prophage.

lysogenic conversion

Alteration of a bacterial cell's phenotype by the insertion of a prophage into its genome. This is responsible for several different bacterial species' ability to produce toxin (e.g. cholera, tetanus, etc. )

lambda repressor protein

protein that causes repression of lytic events, represses cro protein

lysogeny

most viral genes aren't transcribed but viral genome is replicated with host chromosome and passed to daughter cells

RecA

protein activated by cell stress that cleaves the lambda repressor protein, allowing balance to be tipped towards lysis

virulent

viruses that always lyse and kill host after infection

species specificity

a particular virus infects only particular species (based on presence of receptor for entry)

temperate

viruses that integrate and replicate their genomes with the host genome and without killing the host, establishing a long, stable relationship

Cro protein

protein that activates lytic events and represses lamba repressor protein

induction

the process causing a prophage to become virulent

prophage

viral DNA integrated into host DNA

tissue tropism

a particular virus targeting a particular tissue (based on presence of receptor for entry)

late proteins

head and tail proteins, enzymes required to release mature phage particles

ICAM-1

immune protein found on surface of cells. receptor for the common cold.

CD4

molecule found on T-cells. receptor for HIV.

CCR5

co-receptor for HIV. people with very few of these are less susceptible to HIV.

HAART

highly active antiretroviral therapy- use of combinations of drugs (e.g. RT, protease, integrase inhibitors) that are effective against AIDS

PrEP

Pre-exposure prophylaxis: can reduce the risk of HIV BEFORE exposure (RT inhibitors are particularly effective for this)

norovirus

naked ssRNA virus (positive strand) that causes the 24-48 hour stomach flu (diarrhea, vomiting, cramps). Very contagious (feared on cruise ships and other enclosed areas)

papillomavirus

Naked dsDNA virus that causes cervical cancer and warts. Sexually transmitted infections common prior to creation of HPV vaccine

cytokine storm

A potentially fatal immune reaction caused by highly elevated levels of pro-inflammatory cytokines

TMV

Virus affecting plants causing a mosaic pattern on leaves. This was the first virus ever discovered, using a filtration experiment - the disease was transmitted in the filtrate (too small to be bacteria)

vector

Something that transfers things from one place to another, for example an organism that carries a pathogen from one infected person to another, such as the mosquito that carries the malaria protist.

influenza

Segmented RNA virus (enveloped) made up of 8 segments (10 genes) that causes a lung infection (may lead to a cytokine storm). Key proteins are hemagglutinin and neuraminidase. (1918 H1N1 flu = 50 million dead in 2 years of the pandemic)

SARS-CoV2

Single stranded (+ strand) RNA virus that is the causative agent of COVID-19. This virus uses ACE2 as a receptor and infects lungs, causing pneumonia in severe cases.

COVID-19

Pandemic disease caused by SARS-CoV2. Symptoms are mild in 80% of the cases, severe in ~10%, with a 2-3% case fatality rate (due to pneumonia and multi-organ failure)

plasmodesma

An open channel in a plant cell wall through which strands of cytoplasm connect from adjacent cells. This is a typical route viruses use to move from one cell to the next