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COPY FDN3 By Nathan and Minnie > Viruses > Flashcards

Viruses Flashcards

1
Q

What are the steps in the productive replicative cycle?

A
  1. Attachment
  2. Penetration
  3. Uncoating and disassembly
  4. Transcription
  5. Translation
  6. Replication
  7. Assembly
  8. Release from cell
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2
Q

Where do most RNA viruses release their genome during the disassembly stage of the viral productive replicative cycle?

A

Cytoplasm (as ribonucleoprotein)

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3
Q

Where do most DNA viruses release their genome during the disassembly stage of the viral productive replicative cycle?

A

Nucleus

(May require microtubules or other molecular motors to translocate nucleocapsid from cell periphery to nuclear core)

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4
Q

What converts negative sense single stranded viral RNA to positive sense RNA prior to translation?

A

RNA-dependent RNA polymerase (encoded by the viral genome)

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5
Q

What are the four characteristics of the genomes of RNA viruses?

A
  • Smaller genome sizes (higher error rate when replicating)
  • Maximum upper size limit
  • Often exist as quasispecies
    • Quasispecies = swarms of viruses of the same species with slightly different genome nucleotide sequence
    • Creates a target for natural selection
  • Segmented genomes
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6
Q

What is the relationship between genome size and error rate in replication for viral genomes?

A

Inversely related

(smaller genome associated with higher error rate)

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7
Q

Give 2 examples of viral proteins mediating attachment during the attachment stage of the viral productive replicative cycle

A
  • Influenza - hemagglutinin
  • HIV - gp120 (outer envelope protein)
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8
Q

Give 2 examples of viruses utilizing existing cell surface molecules in the attachment stage of the viral productive replicative cycle

A
  • Influenza - sialic acid oligosaccharides
  • HIV - CD4, CXCR4, CCR5
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9
Q

What do ss(–)RNA viruses use to convert ss(–)RNA to mRNA and genomic ss(+)RNA?

A

Viral RNA-dependent RNA polymerase

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10
Q

In the replication cycle of a DNA virus, what do early mRNAs typically encode?

late mRNAs?

A

early: regulatory proteins and proteins important for DNA replication, to take over host cell machinery
late: structural proteins

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11
Q

What do retroviruses use to convert ss(+)RNA to dsDNA?

A

Viral RNA-dependent DNA polymerase (reverse transcriptase)

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12
Q

What is the most important determinant of the type of cells viruses infect (tropism)?

A

Surface glycoprotein

(Must have cell surface receptors for the virus)

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13
Q

What is episomal latency?

A

Extrachromosomal viral genes floating in the cytoplasm or nucleus

Herpesviruses (HSV, EBV, VZV, CMV)

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14
Q

Which family of viruses exhibits episomal latency?

A

Herpesviruses (HSV, EBV, VZV, CMV)

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15
Q

What is proviral latency?

A

Viral genome integrated into DNA of host cell (provirus)

Ex: HIV

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16
Q
  • An epidemic of gastroenteritis is traced to a malfunction at a local water treatment plant. A viral pathogen is identified. What can you likely predict about this virus?
A

It is likely a non-enveloped virus

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17
Q

What is the most common viral infective agent in humans?

A

Rhinovirus

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18
Q

Human rhinovirus is a [family, genetic material/sense, shape, portion of virus]

A

Human rhinovirus is a picornavirus that has (+)ssRNA and an icosahedral capsid

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19
Q

How does rhinovirus cause rapid onset of infection?

A
  • Rhinovirus adheres to surface receptors within 15 minutes of entering respiratory tract
  • Binds to ICAM-1 receptors on respiratory epithelial cells -> infected cells release cytokines and chemokines -> activate inflammatory mediators -> upper respiratory epithelial cell lysis
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20
Q

What is the optimal temperature for replication of rhinovirus?

Where is this temperature found?

A

32oC

Nose and large airways

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21
Q

Human Metapneumovirus is [family, genetic material/sense]

A

Human Metapneumovirus is a member of the pneumoviridae family and uses (–)ssRNA

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22
Q

Human metapneumovirus may be the _____ most common cause of lower respiratory tract infection in young children (after RSV) and causes a _____ severe disease than RSV

A

Human metapneumovirus may be the second most common cause of lower respiratory tract infection in young children (after RSV) and causes a less severe disease than RSV

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23
Q

Human coronavirus is [envelope status, genetic material/sense, shape, structure]

A

Human coronavirus is an enveloped (+)ssRNA virus that has a helical nucleocapsid

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24
Q

Who is the mortality risk from human parainfluenza virus limited to?

A
  • Very young children
  • Elderly
  • Immunocompromised
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25
Q

Human adenovirus is [envelope status, genetic material/sense]

A

Human adenovirus is a nonenveloped dsDNA virus

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26
Q

What allows prolonged survival of human adenovirus outside the body?

A

Human adenovirus is unusually stable to chemical or physical agents and adverse pH conditions

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27
Q

What illnesses does human adenovirus cause?

A

URI, pneumonia, conjunctivitis, tonsilitis, croup, gastroenteritis, cystitis, meningitis, encephalitis

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28
Q

What are the symptoms of measles virus?

A
  • Fever
  • Cough
  • Coryza
  • Conjunctivitis
  • Koplick’s spots
  • Morbilliform rash
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29
Q

Complications of measles are common and most severe in ____. They include:

A

Complications with measles are common and most severe in adults

They include diarrhea, pneumonia, encephalitis (SSPE: subacute sclerosing panencephalitis), and corneal ulceration leading to corneal ulceration and blindness

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30
Q

What is the clinical presentation of human mumps virus?

A

Human mumps virus presents with parotitis, orchitis, meningitis/encephalitis (rare)

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31
Q

Rubella is [family, genetic material/sense, envelope status, shape]

A

Rubella is a togavirus that has (+)ssRNA and an enveloped icosahedral capsid

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32
Q

What is the clinical presentation of rubella?

A
  • Usually mild and subclinical
  • Low grade fever
  • Rash appearing first on face then moving across body
  • Congenital rubella syndrome in neonates (cardiac, cerebral, ophthalmic, auditory defects)
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33
Q

Does rubella still exist in the U.S.?

A

No, rubella was eliminated from the U.S. in 2004

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34
Q

How are enveloped viruses typically transmitted?

A

Respiratory, parenteral, sexual routes

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35
Q

How are non-enveloped viruses typically transmitted?

A

Fecal-oral route

Viruses that can be transmitted through contaminated water are typically non-enveloped

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36
Q

Suppose you know that a virus has helical symmetry

What is the likely makeup of the viral genome?

A

ssRNA

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37
Q

Describe the clinical manifestations of influenza

A
  • Fever
  • Chills
  • Cough
  • Nasal congestion
  • Myalgia
  • Headache
38
Q

How is flu treated?

A

Antiviral therapy

  • Most effective if started within 24 hours of onset
  • Very important for elderly or immunocompromised patients
  • Leading treatment: Oseltamivir (Tamiflu)
    • Neuraminidase inhibitor
    • Works against influenza A and B
  • Alternatives: Zanamivir, Baloxavir
39
Q

What is Palivizumab?

What is it used for?

Who should receive it?

A
  • Palivizumab (synagis) is a monoclonal antibody directed against respiratory syncytial vurus fusion protein
  • It is used to prevent RSV infection (not to treat)
  • High risk infants should receive palivizumab
    • Premature infants
    • Infants with cardiopulmonary disease (especially those on ECMO)
40
Q

What is the pathogenesis of Parvovirus B19?

A
  • The virus targets erythrocyte progenitors, preventing the synthesis of new red blood cells
  • The virus is mild or benign in healthy children
    • The 5th disease (Erythema infectiosum)
    • “Slapped cheek”
    • Quick recovery without complications
  • However, it has more severe effects in anyone with a shorter red blood cell lifespan
    • ​Aplastic crisis in persons with hemolytic anemia
    • Chronic aplastic anemia in AIDS patients
    • Hydrops fetalis (heart failure) in fetuses
41
Q

Vitamin A can decrease the mortality of which viral disease by 50%?

A

Measles

42
Q

What are the 7 most common causes of the common cold?

A

RIP-RACH (Basicaly what people sound like with a cold?)

  • Rhinovirus
  • Influenza
  • Parainfluenza
  • Respiratory syncytial virus
  • Adenovirus
  • Coronavirus
  • Human metapneumovirus
43
Q

What is rotavirus resistant to?

A
  • Low pH
  • Concentrations of chlorine typically used to treat sewage and drinking water
44
Q

What cell components does rotavirus infect?

A

Intestinal villi

45
Q

Where does transcription of rotavirus occur?

A

Inside the double-layered particle

46
Q

What does NSP4 of rotavirus do?

A

an enterotoxin that stimulates anion movement across membranes and promotes diarrhea

47
Q

What does poliovirus bind?

A

CD155 cell surface receptor found in humans and some non-human primates

48
Q

Where does poliovirus replicate?

A

GI tract

49
Q

What is the distribution in the severity of symptoms in people infected with poliovirus?

A
  • ~95% have transient viremia
  • ~5% have sustained viremia w/ fever, headache, sore throat
  • <1% of cases are neuroinvasive
    • 0.1% of cases cause frank paralysis
50
Q

Which viruses cause acute flaccid myelitis?

A
  • Poliovirus
  • Non-polio enteroviruses
  • West Nile viruses and related viruses such as Japanese encephalitis virus and Saint Louis encephalitis virus
  • Adenovirus
51
Q

Hepatitis A Virus is [family, genetic material, envelope/non]

A

Hepatitis A virus is a picornavirus that has ssRNA and is nonenveloped

52
Q

Why can Hepatitis A survive under harsh conditions?

A
  • Resistant to detergent, acid, solvents, drying, high temperatures
  • Can survive in fresh and salt water
53
Q

Why can the Hepatitis A vaccine be given as postexposure prophylaxis?

A

Hepatitis A has a long incubation period (30 days)

54
Q

What is the relationship between jaundice and age in people infected with Hepatitis A virus?

A

Jaundice occurrence increases with age

55
Q

Describe the important characteristics of Hepatitis E virus

(transmission, incubation, tissues affected, fatality, how to diagnose/treat)

A
  • Fecal-oral transmission
  • Common in places with poor sanitation
  • Long incubation period (40 days)
  • Liver tropism
  • No chronic infection
  • Overall case fatility rate higher than Hep A (especially high in pregnant women, particularly in third trimester)
  • Diagnosed by HEV antibody or HEV RNA
  • Effective vaccine developed but stopped b/c not profitable
56
Q

Which enteric virus generates novel strains by gene segment reassortment?

A

Rotavirus

57
Q

During herpesviruses latency, how does the viral genome persist in the cell nucleus?

A

As an autonomous episome

58
Q

During herpesvirus latency, how are viral genomes partitioned to daughter cell nuclei of dividing host cells?

A

Virus expresses EBNA1, which attaches the episomes to cell chromosomes

(examples: B lymphocytes infected with EBV)

59
Q

What is acyclovir?

A

A nucleoside analogue used to treat herpesviruses, specifically HSV

60
Q

What testing can distinguish acute EBV infection from past EBV infection?

A

Acute EBV infection is often associated with positive heterophile antibody test (monospot), elevated anti-EBV IgM, and a negative anti-EBNA IgG

Development of positive anti-EBNA IgG is correlated with resolution of acute EBV infection

61
Q

What are the clinical manifestations of CMV infections in immunocompetent vs immunocompromised hosts?

A

Immunocompetent hosts present with infectious mononucleosis-like syndrome (heterophile mononucleosis)

Immunocompromised hosts typically present with colitis, hepatitis, and retinitis

62
Q

What are the causes of heterophile-negative mononucleosis?

A
  • False negative (in which case EBV is the cause)
  • CMV
  • Toxoplasmosis
  • HHV-6
  • HIV
63
Q

Which virus has this characteristic “scalloped” border?

A

Norovirus, of the calicivirus family

64
Q

Which virus is known for its “wheel-like appearance” en electron micrographs?

A

Rotavirus

(wheels rotate)

65
Q

Which virus is known for its characteristic star shape?

A

Astrovirus (HAstV)

69
Q

Which virus its the most common cause of acute gastroenteritis in young children?

A

Rotavirus

(Adults are rarely infected because there is a lot of cross-coverage if you are immune to one serotype)

vs norovirus is most common cause of acute gastroenteritis overall

70
Q

Why is norovirus more likely to affect adults than rotavirus?

A

Norovirus mutates quickly and does not establish a good protective immunity in the host.

  • There is no cross-protection between serogroups
  • Re-infections are possible

Rotavirus establishes immunity in the host. Most people get one bout of rotavirus as a child, and then are protected for the rest of their life

  • There is cross-protection between serogroups
  • Re-infection is very rare
71
Q

What are the most common causes of aseptic meningitis?

A

Aseptic = viral (no bacteria in CSF)

  • Enteroviruses
    • Coxsackie A
    • Coxsackie B
    • EV-71
72
Q

Which enterovirus can cause an infected individual to require a heart transplant?

A

Coxsackie B

It can cause severe heart damage

73
Q

List the important herpesviruses, grouped by family

A

Alpha herpes viruses (neurotropic, broad host range)

  • HSV-1
  • HSV-2
  • VZV

Beta herpes viruses (slow growing, affect more in immunocompromised, cause enlarged cytoplasm aka cytomegaly)

  • CMV
  • HHV6
  • HHV7

Gamma herpes viruses (oncogenic, lymphotropic)

  • EBV
  • HHV8 (KSHV)
74
Q

Which herpes virus is associated with oral/labial lesions and can infect a broad host range?

A

HSV-1, also known as herpes labialis

75
Q

What complications can arise from HSV-1?

A
  • Herpetic keratitis
    • Treatable, infectious blindness
  • Encephalitis
    • Fever, focal encephalopathy (CT/MRI will reveal lesions on one side of frontal temporal lobe), personality changes
    • Can be fatal
    • May occur in primary or reactivation infections if the virus travels to the CNS from the dorsal root ganglia
76
Q

What are the possible complications of herpes zoster virus?

A
  • Zoster opthalmicus
    • Vision loss due to involvement at the first division of the trigeminal nerve
  • Paresis
  • Myelopathy
  • Vasculopathy
  • Post-herpetic neuralgia (PHN)
77
Q

Describe the presentation of HCMV in an immunocompromised patient (HIV/AIDS and Transplant)

A

In general: either primary or reactivation infection can cause colitis, hepatitis, and/or retinitis

78
Q

Describe the presentation of a congenital HCMV infection

A

Can be acquired intra-natally or perinatally

  • Intranatal = more severe
    • Acquired from non-immune mother
    • Jaundice
    • Hepatosplenomegaly
    • Petechial rash
    • Deafness
    • Neurological effects
      • Microcephaly
      • Motor disability
      • Chorioretinitis
      • Cerebral calcifications
  • Perinatal = more subtle effects on hearing and intelligence
79
Q

Which virus represents the leading causes of congenital mental retardation and hearing loss?

A

HCMV

80
Q

What is the site of latency of EBV?

A

B-cells

81
Q

Which 3 cancers are associated with EBV?

A
  • Burkitt’s lymphoma (non-Hodgkin lymphoma)
  • Hodgkin lymphoma
    • Mixed cellularity, lymphocytes depleted
  • Nasopharyngeal carcinoma
82
Q

Describe the clinical presentation of HHV6 in an adult

A

Infectious mononucleosis

(Note: HHV6 causes roseola in young children)

(heterophile/monospot test will be negative)

83
Q

How does HIV adhere to and enter host cells?

A

Early virus: Infects macrophages

  • gp120 on the viral envelope binds to host cell CD4
  • CCR5 coreceptor on host macrophage is activated

Later virus: Infects CD4+ helper T-cells

  • gp120 on the viral envelope binds host cell CD4
  • CXCR4 coreceptor on host T-cell is activated
84
Q

Which HIV proteins are important for entry and infection of host cells?

A
  • gp120: Binds to host CD4
  • RT: Reverse transcriptase - turns ss(+)RNA into DNA
  • IN: Integrase - integrates the DNA transcript into the host genome
  • PR: Protease - cleaves viral polyprotein into funcitonal units

Note: Pol is the HIV gene that encodes RT, IN, and PR

85
Q

Describe the treatment for HIV

A

Combination of drugs to combat rapid mutation rate

  • 2 nucleoside/nucleotide analogs (inhibit reverse transcriptase)
  • 1 integrase inhibitor and/or 1 protease inhibitor
86
Q

How is Dengue fever transmitted?

A

Aedes mosquito

Vertical transmission from mother to fetus is possible

87
Q

Describe the clinical presentation of West Nile Virus

A
  • 1/5 of infected people develop symptoms
    • Flu-like
  • 1% of infected people develop complications
    • Encephalitis (most common)
    • Meningitis
    • Acute flaccid paralysis
88
Q

Describe the clinical presentation of chikungunya virus

A
  • Fever
  • Arthralgias
  • 60% of infected have persistent joint pain for years
89
Q

How is chikungunya virus transmitted?

A

Aedes mosquito

Vertical transmission mother -> fetus

90
Q

List the viruses (discussed in FDN3) that can be transmitted by mosquito.

Identify the type of mosquito

A

Aedes

  • Chikungunya virus
  • Dengue fever
  • Zika Virus

Culex

  • West Nile Virus
91
Q

Describe the clinical presentation of Zika virus

A

Usually mild

  • Symptoms
    • Acute onset
    • Fever
    • Maculopapular rash
    • Arthralgia
    • Conjunctivitis
    • Myalgia
    • Headache
  • Lasts days - 1 week
  • Severe disease is uncommon; case fatality is low
  • Complications are possible
    • Guillan-barre syndrome
    • Infection in pregnancy -> congenital infection
      • Microcephaly
92
Q

Dengue fever, Zika virus, and Chikungunya fever are endemic to similar regions and may present with similar symptoms.

What would you look for to distinguish between them?

A

Look at the most prominent symptom

Dengue: Muscle/bone pain

Chikungunya: Joint pain

Zika: Rash

93
Q

How is SARS-CoV Transmitted?

A

Bats -> Civets -> Humans

Human - Human

Humans are infected by respiratory droplets

94
Q

How is MERS-CoV transmitted?

A

Bats -> Camels -> Humans

Human - Human

Humans are infected by respiratory droplets

COPY FDN3 By Nathan and Minnie (12 decks)

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