Lesson 1 VMCB413 Flashcards
a tissue fragment used to isolate viruses from animals with persistent infection
explant cultures
derived directly from tissues and contain many cell types such as epithelial cells, fibroblasts, keratinocytes, melanocytes
primary cell cultures
retain their characteristic diploid chromosomal constitution and can support the growth of a wide range of viruses
semi continuous
immortal cell lines derived from either normal or neoplastic tissue and can be passaged indefinitely
continuous cell cell culture
induce cell lysis and cellular transformation in cell culture
burster lytic virus
these induce formation of multinucleated giant cells
creeper virus
though no longer extensively used, this remains the preferred method for isolation of influenza A viruses and for many avian viruses
inoculation on embryos
new area of antiviral research wherein those RNA viruses with inherently high mutation rates are administered with mutagenic agents to drive viral extinction through violation of the error threshold and error catastrophe
lethal mutagenesis
is the extinction of an organism as a result of excessive mutations
error catastrophe
a virus mutant which can replicate only under defined permissive conditions
conditional lethal mutants
rendering a virus towards low viral load and low viral fitness by subjecting it to a combination of mutagenic agents and antiviral compounds
viral suppression
variant strains showing differences in the tissue type and species of target cells affected by viruses
host range mutants
viruses that replicate in the presence of antibody
antibody escape mutants
a virus with decreased infectious titer despite a high number of viral particles
defective interfering mutants
variant strains that cause less serious infections in humans and animals
attenuated mutants
exchange or transfer of genetic material between different but closely related viruses infecting the same cell simultaneously, or between virus and host cell
recombination
recombination between positive-sense single stranded RNA viruses and occurs through a template switching mechanism
copy choice or template switching
infectious progeny are produced from parental viruses, of which one or both are non-infectious, following mixed infection of a cell
reactivation
when infectious progeny are produced from related viruses inactivated by lethal mutations at different loci in their genomes
multiplicity reactivation
occurs when an inactivated virus becomes capable of replicating after acquiring genetic material from an infective virus
cross reactivatio or genome rescue
an infectious extracellular virus particle consists of nucleic acid DNA or RNA that is covered by a protein coat
virion
ashell of subunits of proteins called capsomere that encloses the genome of vertebrate viruses
capsid
combined nucleic acid and capsid which can either be naked or covered with a membrane termed an envelope
nucleocapsid
This mutant promote the establishment and maintain persistent infections
defective interfering mutant
proteins that make up the subunit of capsid
structural proteins
a lipid bilayer and associated glycoproteins that cover a nucleocapsid
envelope
proteins encoded by viral nucleic acid for binding to receptors on host cells, membrane fusion, uncoating of the virion and destruction of receptors on host cells
glycoproteins
knob-like projections from the envelope formed from the oligomers of glycoproteins
peplomers or spikes
a layer of protein present between the nucleocapsid and the envelope in some enveloped viruses that provides additional rigidity to the virion
matrix protein
infectious particles, which can transmit a disease, composed mainly of a protein without any detectable nucleic acid
prions
mad cow disease in humans
variant Creutzfeldt Jakob disease
initial stage of virus replication whereby the infecting virus loses its physical identity and most or all of its infectivity
eclipse phase
e replicative cycle of a virus may range from
6 to 40 hrs
naked viruses or non enveloped viruses undergo a receptor based endocytosis also known as
viropexis
method in which the viral envelope fuses with the plasma
membrane and releases the capsid into the cell cytoplasm
fusion
process of separation of viral nucleic acid from its protein core for transcription to take place
uncoating
central event in replication of viruses
biosynthesis or replication of nucleic acid
what enzyme do RNA viruses generate to transcribe and replicate mRNA
polymerase
Where does uncoating take place inside the cell
cell membrane, cytoplasm, nucleus
DNA replication takes place in the host cell nucleus, however synthesis of capsid and other proteins occur in?
cytoplasm
a virus which all components are synthesized in the cytoplasm
poxvirus
first step in viral maturation
assembly of protein capsid
envelope develops around the capsid by a process called
budding
Due to defect during assembly of viral components, some of the daughter virions that are produced may not be infective
incomplete virus
viruses that occasionally enclose host cell nucleic acid instead of viral nucleic acid, therefore, are non infective and lack the capability to replicate
pseudovirus
leads to loss of virus infectivity
uncoating
virus components may be synthesized but the maturation is defective maybe due to infection of the wrong host cells by the virus
abortive infection
viruses that produce fully mature virions only in the presence of helper viruses which supplement the genetic deficiency in the defective viruses
defective viruses
how does nucleoside analogues act against virus
inhibit replication of viral genome
how does interferons inhibit virus
inhibit assembly of virion components
has antiviral activity against influenza A virus by preventing uncoating shortly after endocytosis of virus by the host cell
amantadine
How does neuraminadase interfere with viral infectivity?
interfere with release of virus from host cells
Ribavirin is a drug against which virus
Influenza virus
a nucleoside analogue active against betaherpesviruses
Ganciclovir
nucleoside analogue used against herpesvirus
penciclovir, famciclovir, acyclovir
How does non nucleoside polymerase inhibitors inhibit replication of viruses?
by binding to the pyrophosphate binding site of the DNA polymerase to block binding of nucleotides
A thymidine analogue for treating herpesvirus keratitis in animals
Idoxudirine
which type of microscope can be used for direct examination of nasopharyngeal aspirate for an animal with respiratory disease
EM, IF
which microscope is used for direct examination of ulcer scrapings and vesicular fluids in animals with skin disease
EM, ID
conjunctival scrapings and smears can be directly examined by using what type of microscope
Light microscope and Immunoflourescence
