Virology Introduction (Exam 2) Flashcards
viral genome
released inside the cytoplasm of the host cell
what are genomes made up of?
DNA or RNA; not both, either or. single stranded (ss) or double stranded (ds)
what do viruses need to survive?
a living cell to latch onto and leverage
virus
Consists of a single nucleic acid surrounded by a protein coat and capable of replication only within the living cells of bacteria, animals, or plants. “obligate intracellular parasite”
capsid
protein coat that surrounds viral nucleic acid. repeating subunits -capsomeres. helical or icosahedral symmetry.
nucleocapsid
protein nucleic acid complex
viroids
smallest known autonomously replicating molecule
prions
infectious protein molecules; contain no definable nucleic acid
viridae
family
virinae
subgroup
virus
genus
parvoviridae
family
parvovirinae
subgroup
parvovirus
genus
erythrovirus
genus
how are viruses classified?
they are grouped into families, subgroups, and genera
how are viruses grouped?
grouped into families according to
1. nucleic acid (ds/ss RNA, ds/ss DNA)
2. morphology of virion
3. strategy of viral replication
reverse transcription
retroviruses use RNA as a template to make DNA - used by HIV
Non-enveloped DNA viruses
Parvovirus - ss DNA
Papovavirus - ds DNA
Adenovirus - ds DNA
Iridovirus - ds DNA
Enveloped DNA viruses
Hepadnavirus - partially ds DNA
Poxvirus - ds DNA
Herpesvirus - ds DNA
Non-enveloped RNA viruses
Picornavirus - ss RNA
Reovirus - ds RNA
Enveloped RNA viruses
all ss RNA
Rhabdovirus
Togavirus
Orthomyxovirus
Coronavirus
Bunyavirus
Arenavirus
Retrovirus
Paramyxovirus
Difference between nonenveloped and enveloped viruses
enveloped viruses have a coating and spikes; nonenveloped do not
components of the virion structure
(outside going in)
spike projections
lipid envelope
protein capsid
virion associated polymerase
nucleic acid
virion morphology
simple structure
repetitive structure
high level of redundancy
virus replication
replicate within a host cell while utilizing the host cell’s nucleic acids
steps of virus replication
- virus attachment and entry
- uncoating of virion
- migration of genome nucleic acid to nucleus
- transcription
- genome replication
- translation of virus mRNAs
- virion assembly
- release of new virus particles
viral life cycle
attachment
penetration
un-coating
multiplication
assembly
release
virus cultivation
complex and includes:
chicken egg culture
cell culture
animal inoculation
what causes sickness?
pathogens; viruses, bacteria, parasites
adenovirus
cause of common cold
poxviridae
smallpox, cowpox, monkeypox
herpesviridae
cold sores (HHV-1)
genital herpes (HHV-2)
chickenpox (HHV-3 or varicella zoster)
papovaviridae
papillomavirus -warts
hepadnaviridae
cause of Hepatitis B
piconaviridae
causes polio
togaviridae
west nile encephalitis
rhabdoviridae
rabies
reoviridae
cause respiratory and intestinal tract infections
retroviridae
HIV
what is a viruses inner core?
nucleic acid surrounded by protein coat known as an envelope
size range of viruses
20-250 nanometers (nm)
how to diagnosis viral infections?
- clinical syndrome
- specimen
- methodologies
- antigen detection
- nucleic acid detection
- antibody detection
- microscopic: viral induced cytopathology
elements of interaction
viral stain
inoculum size
route of exposure
susceptibility of host (pre-existing immunity)
immune status/age of host
result of interaction
no infection
abortive infection
asymptomatic infection
symptomatic infection
abortive infection
you get infected, fight the infection, but there is not tract of you ever having the infection
latent infections
infection is followed by symptom-less period, then reactivation, particles not detected until reactivation, symptoms of reactivation and initial disease may differ.
chronic infections
can be detected at all times, disease maybe present or absent during extended times or may develop late.
latent infections example
herpes simplex viruses 1 and 2 (HSV1 and HSV2) and shingles (zoster, chicken pox). after initial infection, virus replicates in neurons in non-infectious state. Virus activated to produce new disease symptoms
chronic infections example
hepatitis B aka serum hepatitis
after initial infection with or without disease symptoms, infectious virus is released from host with no symptoms
slow infections
agent gradually increases in amount over long period of time; two groups of infectious agents cause this infection (retroviruses which include HIV, prions); similar to the lysogenic cycle of gamma-phage
what are viruses capable of?
infecting all forms of life like vertebrates, prokaryotes, fungi, algae
most abundant form of life?
viruses, however, bacteriophages are extremely abundant, estimated 10^31 tailed bacteriophages
are all viruses bad?
no silly goose!
bacteriophages
viruses that infect harmful bacteria; hold promise as antibiotics; particularly in antibiotic resistant bacteria, immune reaction to phages remains a serious obstacle
phages
disrupt or kill biofilms made by bacteria
what is in a constant war?
bacteria and bacteriophages (viruses that only infect bacteria)
what has bacteria evolved to do?
remember bacteriophages that have encountered in the past so that they can more quickly destroy them in the future; they save a small segment of the bacteriophage’s DNA in their own genome
Process of inserting the bacteriophage DNA?
once docked, the bacteriophage will insert its genome into the bacteria/ using a family of defensive proteins called Cas, the bacteria will cut a small segment of the bacteriophage’s DNA and insert it into its own genome at a specific spot called the CRISPR Locus
what leads to discovery of promoters for eukaryotic RNA polymerases?
study of small DNA
what leads to discovery of many cellular oncogenes?
study of cancer producing viruses
what was discovered from studying mRNA from DNA viruses?
RNA splicing
what was discovered from studying phages and DNA viral replication?
Understanding of cellular DNA replication
benefit of studying tumor viruses?
clearer understanding of cancer
what can viruses be engineered to do?
carry exogenous genes that can be inserted in host’s genome; referred to as vector virus which holds therapeutic agents; remains an issue
viral vector gene therapy for sickle cell disease
collection of blood forming stem cells - stem cells corrected by beta globin gene transfer from viral vectors - transplantation of corrected stem cells back to pt
cultivation of host
viruses multiple only inside host cell; cultivated in the lab in cell culture or tissue culture
quantitation
TEM direct count
methods of studying viruses
cultivation of host and quantitation
measurement of viruses
plaque forming assay
hemagglutination assay
plaque forming assay
initially done with bacteriophages and bacteria
hemagglutination assay
rapid and convenient, highest dilution showing max agglutination is titer of the virus
transmission of viruses
respiratory (influenza a virus)
fecal-oral (enterovirus)
blood-borne (hep b virus)
sexually (hiv)
animal or insect vectors (rabies)
virus tissue tropism
targeting of the virus to specific tissue and cell types
CD4+
cells infected by HIVC
CD155
acts as the receptor for poliovirus
in vivo disease
cell destruction, virus-induced changes to gene expression, immuno-pathogenic disease
acute virus infections
localized to specific site of body, development of viraemia with widespread infection of tissues
epstein barr virus
burkitt’s lymphoma
human papillomavirus
benign warts, cervical carcinoma
human t cell leukemia virus (HTLV-1)
leukemia
hepatitis c virus
liver carcinoma
virus induced tumors
virus infects uninfected cell, integrated into cellular genome, causes changes in expression resulting in uncontrolled cell multiplication and tumor formation
cytopathic effect (CPE)
structural changes in host cells that are caused by viral infection
what virus causes AIDS?
HIV-1
what virus causes cervical carcinoma?
HPV types 16, 18, 31
what virus causes chickenpox?
varicella virus
what virus causes coldstores?
herpes simplex virus type 1
what viruses cause common cold?
adenovirus, coronavirus, rhinoviruses
what viruses cause diarrhea?
norwalk virus, rotaviruses
what virus cause genital herpes?
herpes simplex virus type 2
what viruses cause hemorrhagic fevers?
dengue virus, ebola and marburg viruses, lassa fever virus
what viruses cause hepatitis?
hep A, B, C virus
what virus causes influenza?
influenza A and B virus
what virus causes measles?
measles virus
what viruses cause mononucleosis?
epstein-barr virus, cytomegalovirus
what virus causes mumps?
mumps virus
what virus causes poliomyelitis?
poliovirus types 1 2 and 3
what virus causes rabies encephalitis?
rabies virus
what virus causes Severe acute respiratory syndrome
SARS coronavirus
what virus causes smallpox?
variola virus
what virus causes warts?
human papillomavirus types 1, 2, 4
what virus causes yellow fever?
yellow fever virus
