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Virology Flashcards

1
Q

Viral Recombination

A

Exchange of gene between 2 viral genetic sequences of one virus by crossing over within regions of significant base sequence homology

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2
Q

Viral Reassortment

A

Exchange of segments between two viruses with different segmented genomes (ex influenza virus), usually happens when the two viruses infect the same cell. High frequency recombination

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3
Q

Complementation

A

When 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein. The non mutated virus “complements” the mutated one by making a functional protein that serves both viruses

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4
Q

Phenotypic mixing

A

Occurs when simultaneous infection of a cell with 2 viruses

Genome of virus A can be partially or completely coated w/ the surface proteins of virus B

Type B protein coat determines the tropism or infectivity of the hybrid virus.

Progeny from this hybrid infection have type A coat that is encoded by its type A genetic material

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5
Q

Live attenuated vaccines

A

Induce humoral AND cell-mediated immunity

Can revert to virulence on rare occasions

No boosters needed for live attenuated vaccines

Dangerous to give live vaccines to immunocompromised patients or their close contacts (except for MMR)

Ex: smallpox, yellow fever, chicken pox (VZV), polio virus (Sabin), MMR, influenza (nasal)

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6
Q

Killed vaccines

A

Induce ONLY humoral immunity but are stable and will not revert to virulence

Ex: rabies, influenze (injected), polio (Salk) –> RIP

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7
Q

Recombinant

A

Uses recombinant virus

Ex: HBV (antigen = recombinant HBsAg), HPV (recombinant of type 6, 11, 16, 18)

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8
Q

DNA viral genomes

A

All DNA viruses except the Parovirus (part of a virus, ssDNA) are dsDNA

All are linear except papilloma, polyma, and hepadnaviruses (all 3 are circular)

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9
Q

RNA viral genome

A

All RNA viruses are ssRNA except Reovirus (repeato-virus, dsRNA)

Positive stranded RNA viruses: I went to a retro (retrovirus) toga (togavirus) party, where i drank flavored (flavivirus) Corona (coronavirus) and ate hippy (hepevirus) Californian (calicivirus) pickles (picornavirus)

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10
Q

Naked viral genome infectivity

A

Purified nucleic acids of most dsDNA (except poxvirus and HBV) and positive strand ssRNA (like mRNA) viruses are infectious

Naked nucleic acids of negative strand ssRNA and dsRNA viruses are not infectious and require polymerases contained in the complete virion to function and replicate

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11
Q

Viral replication

A

DNA viruses: all replicate in the nucleus (except poxvirus)

RNA viruses: all replicate in the cytoplasm (except influenza virus and retrovirus)

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12
Q

Viral envelopes

A

Naked (nonenveloped) viruses include: papillomavirus, adenovirus, parovirus, polymomavirus, calicivirus, picornavirus, reovirus, and hepevirus
–> give PAPP smear and CPR to naked Heppy

Enveloped viruses generally acquire their envelopes from plasma membranes, but herpesvirus acquire from nuclear membrane

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13
Q

Hepadnavirus

A

DNA virus, enveloped, partially ds and circular

HBV: acute or chronic hepatitis, vaccine available, not a retrovirus but has reverse transcriptase

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14
Q

Adenovirus

A

DNA virus, naked, ds and linear

Causes febrile pharyngitis, pnemonia, conjunctivitis (pink eye)

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15
Q

Parovirus

A

DNA virus, naked, ss and linear (negative strand), smallest DNA virus

B19 virus: aplastic crisis in sickle cell disease, “slapped cheeks” rash in children (erythema infectiosum, 5th disease), rheumatoid arthritis-like symptoms in adults

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16
Q

Papillomavirus

A

DNA virus, naked, ds, circular

HPV: warts (1,2,6,11), CIN, cervical cancer (16,18)

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17
Q

Polyomavirus

A

DNA virus, naked, ds, circular

JC virus: progressive mutlifocal leukoencephalopathy (PML) in HIV

BK virus: transplant patients, commonly target kidneys

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18
Q

Poxvirus

A

DNA virus, enveloped, ds, linear, largest DNA virus

Smallpox, cowpox, molluscum contagiosum (flesh-colored dome lesions with central umbilicated dimple)

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19
Q

HSV1

A

DNA virus, enveloped, ds, linear

Gingivostomatitis, keratoconjunctivitis, temporal lobe encephalitis, herpes labialis (lips), latent in trigeminal ganglia

Transmitted by respiratory secretions, saliva

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20
Q

HSV2

A

Herpes genitalis, neonatal herpes, latent in sacral ganglia

Transmitted by sexual contact or perinatally

Tzanck test (genital herpes): smear of opened skin vesicle to detect multinucleate giant cells

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21
Q

HHV3, VZV

A

Chicken pox, shingles, encephalitis, pneumonia, latent in trigeminal ganglia

Transmitted by respiratory secretions

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22
Q

HHV4, EBV

A

Mononucleosis, characterized by fever, hepatosplenomegaly, pharyngitis, and lymphadenopahty (posterior cervical nodes)

Transmitted by respiratory secretions and saliva (kissing disease)

Infects B cells, atypical reactive cytotoxic T cells seen on blood smear

Detect by positive monospot test (heterophile antibody)

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23
Q

HHV5, CMV

A

Congenital infection, mononucleosis (negative monospot), pnemonia, retinitis

Infected cells have characteristic “owl eye” inclusions

Latent in mononuclear cells

Transmitted congenitally and by transfusion, sexual contact, saliva, urine, transplant

24
Q

HHV6

A

Causes Roseola

High fevers for several days that can cause seizures, followed by diffuse macular rash

Transmitted by saliva

25
Q

HHV7

A

Less common cause of Roseola

26
Q

HHV-8

A

Causes Kaposi sarcoma, a neoplasm of endothelial cells

Seen in HIV/AIDS and transplant patients

Dark/violaceous flat and nodular skin lesions representing endothelial growths. Can also affect GI tract and lungs

Transmitted by sexual contact

27
Q

Reoviruses

A

RNA virus, naked, DS segmented, linear, icosahedral

Rotavirus:
The most important global cause of infantile gastroenteritis
Causes villous destruction with atrophy leads to decreased absorption of Na+ and loss of K+
CDC recommends vaccination of all infants

28
Q

Picornaviruses

A

RNA virus, naked, SS positive, linear, icosahedral

RNA is translated into 1 large polypeptide that is cleared by proteases into functional viral proteins.
All are fecal-oral spread except for rhinovirus

PERCH
Poliovirus
Echovirus: aseptic meningitis
Rhinovirus: “common cold”, destroyed by stomach acid
Coxsackievirus: aseptic meningitis, myocarditis, hand/foot/mouth disease, pericarditis
HAV: acute viral hepatitis

29
Q

Hepevirus

A

RNA virus, naked, SS positive, linear, icosahedral

HEV: hepatitis E

30
Q

Calicivirus

A

RNA virus, naked, SS positive, linear, icosahedral

Norovirus: viral gastroenteritis

31
Q

Flavivirus

A

RNA virus, enveloped, SS positive, linear, icosahedral

Yellow fever: transmitted by Aedes mosquitoes, symptoms include high fever, black vomits, and jaundice

HCV: chronic hepatitis

West Nile virus

32
Q

Togavirus

A

RNA virus, enveloped, SS positive, linear, icosahedral

Rubella:
Once known as German measles
Fever, postauricular lymphadenopathy, fine rash
Causes mild disease in children but serious congenital disease (blueberry muffin appearance signifying extra medullary hematopoiesis)

33
Q

Retrovirus

A

RNA virus, enveloped, SS positive, linear, icosahedral

Have reverse transcriptase
HTLV (human T lymphotrophic virus): T cell leukemia
HIV

34
Q

Coronavirus

A

RNA virus, enveloped, SS positive, linear, helical

“Common cold” and SARS

35
Q

Orthomyxovirus (influenza virus)

A

RNA virus, enveloped, SS negative, linear 8-segmented, helical

Contain hemagglutinin (promotes viral entry) and neuraminidase (promotes proven virion release) antigens

Patients at risk for fatal bacterial superinfection

Rapid genetic changes

36
Q

Genetic shift vs genetic drift

A

Sudden Shift is more deadly than graDual Drift

Genetic shift: causes pandemics. Reassortment of viral genome, segments undergo high-frequency recombination, such as when human flu virus recombines w/ swine flu virus

Genetic drift: causes epidemics. Minor changes based on random mutation

37
Q

Rhabdovirus

A

RNA virus, enveloped, SS negative, linear, helical

Rabies virus:
Bullet-shaped virus
Negri bodies commonly found in Purkinje cells of cerebellum and in hippocampal neurons
Travels to the CNS by migrating in a retrograde fashion up nerve axons
Long incubation period (weeks to months)
Progression of disease: fever, malaise –> agitation, photophobia, hydrophobia –> paralysis, coma –> death
Post-exposure treatment is wound cleansing and vaccination +/- rabies immunoglobulin treatment
More commonly found in bats, raccoons, and skunks bites

38
Q

Paramyxovirus

A

RNA virus, enveloped, SS negative, linear, helical

Parainfluenza: croup

RSV: bronchioloits in babies, treat w/ ribavirin, prevent w/ palivizumab

Measles virus: Koplik spots (bright red spots w/ blue-white center on buccal mucosa) followed by descending maculopapular rash, 3 Cs (cough, coryza, conjunctivitis)

Mumps virus: parotitis, orchitis, aspetic Meningitis (POM)

39
Q

Filovirus

A

RNA virus, enveloped, SS negative, linear segmented, helical

Ebola virus

40
Q

Arenavirus

A

RNA virus, enveloped, SS negative, circular segmented, helical

Lymphocytic choriomeningitis virus

41
Q

Bunyavirus

A

RNA virus, enveloped, SS negative, circular segmented, helical

California encephalitis
Congo hemorrhagic fever

42
Q

Delta virus

A

RNA virus, enveloped, SS negative, circular, uncertain capsid shape

HDV: “defective” virus that requires HBV co-infection to function

43
Q

Hepatitis viruses

A

HAV (RNA, picornavirus): fecal oral, short incubation, no HCC risk, asymptomatic, acute

HBV (DNA, hepadnavirus): parenteral, sexual, maternal-fetal, long incubation, can act as oncogene for HCC

HCV (RNA, flavivirus): blood (IVDU), long incubation, HCC from chronic inflammation, cirrhosis, chronic

HDV (RNA, delta virus): parenteral, sexual, maternal-fetal, need HBV to function, superinfection leads to poor prognosis

HEV (RNA hepevirus): fecal-oral (waterborne), short incubation, no risk for HCC, high mortality in pregnant women

44
Q

Anti-HAV IgM

A

IgM antibody to HAV

Best test to detect active hep A

45
Q

Anti HAV IgG

A

IgG antibody

Indicate prior HAV infection and/or prior vaccination

Protects against reinfection

46
Q

HBsAg

A

Antigen found on surface of HBV

Indicates current HBV infection

47
Q

Anti0HBs

A

Antibody to HBsAg

Indicates immunity to hep B

48
Q

HBcAg

A

Antigen associated w/ core of HBV

49
Q

Anti-HBc

A

Antibody to HBcAg
IgM= acute/recent infection
IgG= prior exposure or chronic infection
Positive during window period (period between infection and reliable testing, can present w/ negative test but still be infective)

50
Q

HBeAg

A

A second, different antigenic determinant in the HBV core

HBeAg indicates active viral replication and therefore high transmissibility

51
Q

Anti-HBe

A

Antibody to HBeAg, indicates low transmissibility

52
Q

HIV virus

A

Retrovirus

Diploid genome (2 molecules of RNA)

Three important structural genes and proteins

  1. Env (gp120 and gp41): formed from cleavage of gp160 to form envelope glycoproteins, gp120 attaches to host CD4+ T cells while gp41 is responsible for fusion and entry
  2. Gag (p24): capsid protein
  3. Pol: reverse transcriptase, aspartate protease, integrase

Reverse transcriptase synthesizes dsDNA from RNA, dsDNA integrates into host genome via integrase

Virus binds CCR5 (early) or CXCR4 (late)

Homozygous CCR5 mutation: HIV immunity
Heterozygous CCR5 mutation: slower course

“F”our stages of untreated HIV infection: flu-like (acute), felling fine (latent), falling count, final crisis

53
Q

HIV diagnosis

A

Presumptive diagnosis made with ELISA (sensitive, high false positive, SNNOUT)

Positive ELISA results confirmed w/ Western blot (specific, high false negative, SPPIN)

Both tests look for viral proteins via antibodies and are often falsely negative in the first 1-2 months and falsely positive initially in babies born to infected mother due to placental transfer of proteins

HIV PCR determines viral load in plasma with high viral load associated w poor prognosis. Also used to monitor effect of drug therapy

AIDS diagnosis w/ less than 200 CD4+ (normal 500=1500)

54
Q

Common diseases of HIV patients

A

Systemic: cough, hepatosplenomegaly, tongue ucler (histoplasma)

Dermatologic: hairy leukoplakia (EBV), thrush (candida)

Gastrointestinal: chronic diarrhea (cryptosporidium)

Neurologic: abscess (toxo, CD4 <50)

55
Q

Prions

A

Caused by conversion of a NORMAL protein termed prion protein (PrPc) to a beta pleated form (PrPsc), which is transmissible.

PrPsc resist protease degradation and facilitates conversion of PrPc to PrPsc

Accumulation of PrPsc results in spongiform encephalopathy and dementia, ataxia, and eventually death

Can be sporadic (Creutzfeldt-Jakob disease, rapidly progressive dementia)

Can be inherited (Gerstmann-Straussler-Scheinker syndrome)

Can be acquired (Kuru)

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