viruses and their classifications

what are the main components of the viral structure?

1. nucleocapsid

2. envelope or naked

nucleocapsid

nucleic acid and capsid in virus

what are the components of a virus?

1. capsid

2. nucleic acid

3. sometimes an envelope

inert

not biologically active

what are viruses obligated to?

parasite cells in order to multiple since they are inert outside the host

what can good viruses help fight?

antibiotic resistant bacteria and cancer

what are bacteriophages?

viruses that infect bacteria and archaea with very narrow specificity

why is it good that bacteriophages have narrow specificity?

only kills the bacteria you are targeting

why is it bad that bacterias have narrow specificity?

since each are so specific, cannot use as broad spectrum treatment

capsid

protein shell that protects the nucleic acid

what part of the virus does the immune system recognize the best?

the proteins (capsid) of the virus

what composes the capsid?

1. capsomeres

2. enzymes

3. structural proteins

what will never be present in the viral capsid?

cell organelles

epitope

part of an antigen on the virus that is recognized by the immune system

what specific structures in the immune system will recognize the epitope?

1. antibodies

2. B cells

3. T cells

how are enveloped viruses transmitted?

through direct contact or vectors

how are naked viruses transmitted?

through the environment

what are enveloped viruses more sensitive to?

alcohol and detergents

what is the composition of the envelope in a virus?

lipid bilayer

where does the lipid bilayer of the viral envelope ALWAYS derive from and why?

the host cell; viruses can only code for proteins not lipids

where can the lipid bilayer originate from in the host cell?

1. nucleus envelope

2. golgi

3. RE

4. cytoplasmic membrane (budding)

what are examples of some of the proteins embedded in the viral envelope?

1. virus receptors

2. co receptors

3. peplomers (some)

peplomers

spikes embedded in the viral envelope that are glycosilated proteins

what is the only way to see peplomers?

electron microscopy

what are the spikes of peplomers often used in?

vaccines to train the immune system to recognize if encountered in the future

what is a characteristic of enveloped with regards to disinfection?

they are generally less resistant to disinfectants then naked viruses

enveloped viruses are...

1. more sensitive to some disinfectants

2. less resistant in the environment

why is it important to know the type of viral genome?

impacts how viruses behave and evolve

the viral genome is either...

1. DNA or RNA

2. segmented or non-segmented

what viral component is most antigenic?

the proteins forming the capsid or the viral receptors embedded in the envelope

prion

abnormally folded protein

what are prions resistant to?

proteases

proteases

enzyme that degrades protein

what happens because prions are resistant to proteases?

proteins accumulate into fibrils and plaques leading to increased pressure on neurons and eventual death of neurons creating vacuoles

what do prions cause?

1. spongiform

2. encephalopathies

are all prions zoonotic?

not all, some can be transmitted via vertical transmission making them hereditary rather than infectious

what are examples of prion diseases in veterinary medicine?

1. Scrapie (sheep)

2. BSE (cattle)

3. CWD (deer)

what type of protein structures are more abundant in "normal" proteins and what does that mean?

more alpha helices allowing more openess

what type of protein structures are more abundant in prions and what does that mean?

more beta sheets making the space more compact

what structures do prions NOT have?

1. nucleic acid

2. envelope

would you be able to perform a PCR on a prion?

no, they do not have a nucleic acid

what characteristics do viruses and prions share?

1. submicroscopic

2. infectious

3. inert outside the host

4. protein structure

what is the purpose of classifying viruses?

to predict their behavior

what is the classification of viruses based on?

evolutionary relationships when comparing their genomic sequences

what dictates a viruses behavior?

their genome

what is the genus for viruses?

-virus

what is the family for viruses?

-viridae

what do all viruses, no matter their host, share?

all viruses share properties within a family

true or false: not all viruses are derived from a common ancestor

true

virus taxonomy is...

continuously changing due to reclassification of existing viruses

different genera may have

different behavior (transmission, tropism, etc.)

as a general rule, where do DNA viruses tend to replicate?

in the nucleus

what is the exception of a DNA virus that does not replicate in the nucleus?

pox, it replicates in the cytoplasm

which type of virus (DNA or RNA) is more species-specific (narrow host range)?

DNA

why are vaccines against DNA viruses effective at prevention and do not require frequent updates?

DNA viruses have a much slower rate of mutation

what type of virus is quite effective at disease prevention and does not need frequent updates?

DNA viruses

as a general rule, where do most RNA viruses replicate?

in the cytoplasm

are most RNA viruses of veterinary importance naked or enveloped?

enveloped

epidemiology of disease

1. host

2. agent

3. environment

does only having the virus automatically mean infection?

no, just the agent does not always equate to infection

pathogen spillover

occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population

what is important about the transmission when discussing spillover?

the pathogen is transmitted from the reservoir population and may OR may no be transmitted within the new host population

zoonosis

any disease or infection that is naturally transmissible from vertebrate animals to humans

arboviruses

both transmit and replicate in arthropod vectors (biological vectors)

what is a specific virus that remains and transmits through the environment in veterinary medicine?

canine parvovirus

what are the characteristics of canine parvovirus?

1. DNA

2. naked

what is an example of a disease that utilize insect vectors in veterinary medicine?

encephalitis viruses

what is an example of a disease that spillover from reservoirs in veterinary medicine?

hendra and nipah viruses

what are the characteristics of hendra and nipah viruses?

1. RNA

2. enveloped

3. zoonotic and zoonotic potential

what are the characteristics of encephalitis viruses?

1. RNA

2 enveloped

3. zoonotic arbovirus

what are ways prions can enter an animal?

1. inhalation

2. ingestion of contaminated food or water

3. in utero

4. lesions to skin or mucus membranes

what are ways prions can exit an animal?

1. nasal secretions

2. saliva

3. secretion in milk and colostrum

4. placental or gestational fluids

5. feces or urine

what are the characteristics of coronaviruses?

1. RNA

2. enveloped

3. zoonotic or potentially zoonotic

what type of influenza virus is the most widespread amongst hosts?

influenza A

what are the characteristics of influenza viruses?

1. RNA segmented

2. enveloped

3. zoonotic or potentially zoonotic

what feature is extremely important for viruses to replicated amongst different species?

having similar receptors

which species acts as the "mixing vessel" for avian and human influenza?

pigs

how does herpesviridae avoid the immune system response?

changes latency to avoid recognition

what are the characteristics of herpesviridae?

1. DNA

2. enveloped

3. species specific