Viruses Flashcards
Viral infection clinical features
- lymphocytosis
- lymphadenopathy
- recurrent viral infections: T-cell deficiency
DNA Viruses
HHAPPPPy:
H - herpes
H - hepadna
A - adeno
P - pox
P - parvo
P - papilloma
P - polyoma
all DNA viruses are icosahedral
enveloped DNA viruses
3 are enveloped: High Profile Hat
H - herpes
P - pox
H - hepadna
non-enveloped DNA viruses
4 are naked: PAPP (pap smear)
P - parvo
A - adeno
P - papilloma
P - polyoma
circular DNA viruses
papilloma
polyoma
hepadna
ssDNA virus
Parvo (smallest DNA virus)
- strand folds over to allow for replication
“Pervo = naked and single”
DNA virus replication
cytoplasm:
- pox (largest DNA virus, already contains all machinery needed for replication)
“Pox, progeny are outside of the box!”
nucleus:
- all other DNA viruses
Herpes classifications
- enveloped, double-stranded, linear
- alpha, beta, gamma
- all herpesviruses induce lifelong latent infection
- oncogenesis
- spread by direct contact
Herpes alpha viruses
alpha:
- herpes simplex virus 1 (HSV-1)
- herpes simplex virus 2 (HSV-2)
- varicella-zoster virus (VZV)
Herpes beta viruses
beta:
- cytomegalovirus (CMV)
- human herpes virus 6 (HHV-6)
- human herpes virus 7 (HHV-7)
HHV-6 and 7 are cause of Roseola Infantum
Herpes gamma viruses
gamma:
- Epstein-Barr virus (EBV)
- human herpes virus 8 (KSHV)
Herpes simplex virus (HSV) clinical manifestations
alpha herpesvirus
HSV-1: gingivostomatitis, cutaneous herpes
HSV-2: genital herpes, cutaneous herpes
Infection & latency:
- mucosa infection ==> moves through neurites ==> latency in sensory ganglia ==> recurrent reactivation
- transmitted through direct contact
- intermittent viral shedding w/o lesions
- lesions can be seen in primary infection and reactivation
Clinical presentation:
- painful papules ==> vesicles ==> pustules ==> ulcers ==> crusted lesions ==> healing
- multinucleated giant cells <- Tzank smear
Herpes simplex virus (HSV) treatment
alpha herpesvirus
genital herpes treatment:
acyclovir or valacyclovir
for recurrent/suppressive genital herpes, same medications but different doses
Varicella zoster virus (VZV) clinical manisfestations
alpha herpesvirus
primary infection: varicella (chickenpox)
- generally benign in children
- diffuse vesicular rash (blisters)
latent infection: zoster (shingles)
- VZV becomes latent in dorsal root or cranial nerve ganglia
- grouped erythematous papules evolve into vesicles or bullae (large fluid-filled blisters)
- painful
Varicella zoster virus (VZV) vaccines
alpha herpesvirus
varicella vaccine: live, attenuated virus vaccine
Shingrix: adult prevention of shingles
cytomegalovirus (CMV) pathogenesis
beta herpesvirus
CMV causes mononucleosis (heterophile-negative type), hepatitis, retinitis, esophagitis
Infection:
- undergoes lytic infection in human fibroblasts, epithelial cells, macrophages <- many organ systems affected
- latency in leukocytes (mononuclear cells) ==> lifelong infection
- high risk of infection in organ & bone marrow transplant recipients, also immunocompromised
- ventricular calcifications in brain
- megalocytes: giant cells with owl’s eye nuclei
Treatment: Ganciclovir
Epstein-Barr virus (EBV) pathogenesis
gamma herpesvirus
Infection:
- initial site of infection: epithelial cells
- latency in B-lymphocytes, using CD21 receptors to infect B-cells ==> oncogenic potential
Clinical presentations:
- primary agent of infectious mononucleosis (atypical CD8+ T cells in blood)
- immunocompromised: oral hairy leukoplakia (cannot be scraped off)
- associated with development of malignancies: nasopharyngeal carcinoma, Burkitt lymphoma
- CT: single ring-enhancing lesion
Infectious mononucleosis
- classical triad: fever, tonsilar pharyngitis, lymphadenopathy (LAD) (swollen lymph nodes)
- peripheral blood lymphocytosis (high WBC count) with atypical lymphocytes
if given antibiotics incorrectly, pts usually develop a morbilliform (measles-like) rash
Epstein-Barr virus (EBV) diagnosis and treatment
- primary infection induces human hterophile antibodies (act against viral antigens & unrelated antigens that can be found on sheep/horse RBCs)
- Monospot test: heterophile antibodies agglutinate horse RBCs
Treatment: typically supportive, no antivirals (acyclovir can reduce duration of viral shedding)
Human herpes virus (HHV) types
beta and gamma herpesviruses
beta:
- HHV-6: Roseola infantum
- HHV-7: Roseola infantum
gamma:
- HHV-8: Kaposi sarcoma, febrile exanthem
Human herpesvirus-6 (HHV-6)
beta herpesvirus
- most HHV-6 primary infections occur in first 3 years of life: roseola infantum, exanthem subitum
- reactivation in immunocompromised hosts
- roseola infantum: rash starts after high fever breaks
Human herpesvirus-7 (HHV-7)
beta herpesvirus
- less common cause of roseola infantum
Human herpesvirus-8 (HHV-8 aka KSHV)
gamma herpesvirus
causes Kaposi sarcoma (cancer on skin/mucous membranes)
- AIDS-associated KS most common in MSM
- cutaneous lesions: hyperpigmented, painless, non-pruritic
Hepadna
- enveloped, double-stranded, circular
Adeno
- nonenveloped, double-stranded, linear
- cause pharyngitis, conjunctivitis, hemorrhagic cystitis (inflamed urinary bladder lining)
Pox
- enveloped, double-stranded, linear
- largest, most complex DNA viruses
- replicates in cytoplasm, brings its own DNA-dependent RNA polymerase
- smallpox
- Molluscum contagiosum virus: skin infection common in children, flesh-colored domed lesions with central umbilication
Parvovirus B19
- nonenveloped, single-stranded, linear
Infection:
- directly cytotoxic to erythroid precursors in bone marrow ==> inhibition of erythropoiesis
Clinical manifestations:
- erythema infectiosum (“Fifth disease”): slapped cheek rash
- reticulocytopenic anemia in immunocompromised patients (leukemia, HIV/AIDS, organ transplants)
Pervo = naked and single
Papilloma
Human papillomavirus (HPV)
- nonenveloped, double-stranded, circular
- HPV causes almost all cases of cervical cancer and most anal cancer
- types 6 & 11: warts
- types 16& 18: cervical neoplasia (abnormal cell growth on cervix)
- oncogenic types: 16, 18, 31, 33
diagnosis: visual inspection
Polyoma
- nonenveloped, double-stranded, circular
- John Cunningham (JC) virus <- AIDS-defining disease
- immunocompromised patients may develop progressive multifocal leukoencephalopathy (PML) or hemorrhagic cystitis
- MRI: non-enhancing demyelination of white matter
RNA Viruses
mnemonic: CHRP CRFT BADPROF (chirpy crafty bad prof)
(+) sense, icosahedral:
naked: CHRP (“location” viruses)
C - Calici (“Cali”)
H - Hepe (“CA people are hippies”)
R - Reo (“Rio de Janiero”)
P - Picorna (“people in Rio are spicy, like pico de gallo”)
enveloped: CRFT (“party” viruses)
C - Corona (beer) <- helical
R - Retro (themed)
F - Flavi (“flavored” Corona)
T - Toga (costume)
(-) sense, helical:
enveloped: BADPROF
B - Bunya
A - Arena
D - Delta
P - Paramyxo
R - Rhabdo
O - Orthomyxo
F - Filo
positive sense (+ssRNA) vs. negative sense (-ssRNA) RNA
+ssRNA
- a type of viral RNA that can be readily translated into proteins (looks like mRNA)
- does not require RNA-dependent RNA polymerase
-ssRNA
- a type of viral RNA that must be transcribed by RNA-dependent RNA polymerase into +ssRNA before it can be translated into proteins
dsRNA virus
Reo virus
“repeato-virus” has double stranded RNA
circular RNA viruses
mnemonic: BAD
B - Bunya
A - Arena
D - Delta
segmented RNA viruses
mnemonic: BOAR
B - Bunya
O - Orthomyxo
A - Arena
R - Reo
*important for hypermutation (influenza)
RNA virus replication
replicates in cytoplasm - all except OR
replicates in nucleus: OR
O - Orthomyxo
R - Retro <- uses reverse transcriptase (DNA)
Calici
- single-stranded
- (+) sense
- icosahedral
- naked
- linear
- non-segmented
- replicates in cytoplasm
Norovirus
Hepe
- single-stranded
- (+) sense
- icosahedral
- naked
- linear
- non-segmented
- replicates in cytoplasm
Hepatitis E (HEV)
Reo
- double-stranded
- (+) sense
- icosahedral
- naked
- linear
- segmented
- replicates in cytoplasm
Rotavirus
Picorna
- single-stranded
- (+) sense
- icosahedral
- naked
- linear
- non-segmented
- replicates in cytoplasm
PERCH:
P - Polio
E - Echo
R - Rhino
C - Coxsacki
H - Hepatitis A (HAV)
Enteroviruses (GI tract):
- Polio
- Echo
- Coxsacki
Rhinovirus
- # 1 cause of common cold
- infects the nose because it cannot survive in stomach acid (acid-labile)
- runny nose, sniffles for 3-4 days, maybe posterior throat discomfort and redness, NO FEVER
- transmission: aerosols and fomites (inanimate objects)
Corona
- single-stranded
- (+) sense
- helical
- enveloped
- linear
- non-segmented
- replicates in cytoplasm
Corona, SARS-CoV, MERS-CoV, SARS-CoV2
- 2nd most frequent cause of common cold
Coronavirus pathogenesis
- spike (S) glycoprotein on envelope recognizes target cell ==> binds Angiotensin Converting Enzyme 2 (ACE2) ==> endocytosis
Retro
- single-stranded
- (+) sense
- icosahedral
- enveloped
- linear
- non-segmented
- replicates in nucleus
HIV, HTLV (human T-cell lymphotropic viruses)
Flavi
- single-stranded
- (+) sense
- icosahedral
- enveloped
- linear
- non-segmented
- replicates in cytoplasm
WSHDY (“flavor town is washed up”)
W - West Nile Virus (WNV)
S - St. Louis encephalitis
H - Hepatitis C (HCV)
D - Dengue
Y - Yellow fever
Toga
- single-stranded
- (+) sense
- icosahedral
- enveloped
- linear
- non-segmented
- replicates in cytoplasm
beautiful girl (bella) in a toga riding a horse:
Rubella (aka German measles or three-day measles),
Eastern Equine Encephalitis virus (EEEV), Western EEV
Bunya
- single-stranded
- (-) sense
- helical
- enveloped
- circular
- segmented
- replicates in cytoplasm
CCHRS (“bun catcher”):
C - California encephalitis
C - Crimean-Congo
H - Hanta
R - Rift Valley
Arena
- single-stranded
- (-) sense
- helical
- enveloped
- circular
- segmented
- replicates in cytoplasm
Lassa, Lymphocytic choriomeningitis virus (LCMV)
Delta
- single-stranded
- (-) sense
- helical
- enveloped
- circular
- non-segmented
- replicates in cytoplasm
Hepatitis D (HDV)
Paramyxo
- single-stranded
- (-) sense
- helical
- enveloped
- linear
- non-segmented
- replicates in cytoplasm
PRM:
P - Parainfluenza
R - Respiratory syncytial virus (RSV)
M - Measles (aka Rubeola) and mumps
Mumps
Paramyxovirus
“Mumps has bumps”
- fever, headache, malaise
- parotitis (inflammation of parotid salivary glands accompanied with lateral cheek/jaw swelling)
- orchitis (swelling of testicles)
Vaccine:
- live viral vaccine (MMR)
Paramyxovirus pathogenesis
- Fusion protein (F protein) on surface of capsid
- F protein fuses with respiratory epithelial cells ==> formation of multinucleated cells
Measles
Paramyxovirus
- maculopapular (flat & raised) rash on face -> neck -> trunk
- 3 C’s: cough, conjunctivitis, coryza (sniffling)
- Koplik spots: blue-white spots with red halo on inner cheek
Rhabdo
- single-stranded
- (-) sense
- helical
- enveloped (bullet-shaped)
- linear
- segmented
- replicates in cytoplasm
Rabies
Orthomyxo
- single-stranded
- (-) sense
- helical
- enveloped
- linear
- segmented
- replicates in nucleus
- Types A, B, C (determined by cell surface antigen)
Influenza
Influenza virus pathogenesis
Orthomyxovirus
2 spike protein subtypes:
1. Hemagglutinin (H): facilitates viral entry by binding sialic acid residues; first step in viral infection
2. Neuraminidase (N): cleaves sialic acid residues on infected host cells and virions, preventing aggregation of virions <- aids in release from host cells
ex: H1N1, H3N3
influenza antigenic drift vs. shift
Antigenic drift:
- epidemics (contained)
- minor antigenic changes due to point mutations
- changes to “H” and/or “N”
Antigenic shift:
- pandemics (uncontrolled)
- major antigenic changes due to genetic reassortment
- 2 different viral strains infect the same host (e.g., pig infected with human and avian influenzas)
*segmented virus allows for more reassortment
Filo
- single-stranded
- (-) sense
- helical
- enveloped
- linear
- non-segmented
- replicates in cytoplasm
Ebola, Marburg
Prions
- irreversibly misfolded protein particle derived from normal body protein
- do NOT contain DNA or RNA
- prions force normal proteins to misfold ==> accumulation in cells ==> cell death
