Virology Flashcards
Nucleic acid genome + capsid =
Nucleocapsid
Attachment to host cell receptors
Surface proteins
For replication
DNA or RNA polymerases
Interaction between nucleocapsid and envelope
Matrix protein
Evasion of host defenses
Antigenic (serotypic) variants
Lipid membrane derived from host cell
Viral envelope
Viral envelope is acquired as the virus exits from the cell in a process called
Budding
All enveloped viruses acquire their envelope from plasma membrane EXCEPT
Herpesvirus
True or False: Enveloped viruses are less stable and more easily inactivated
True
Naked Viruses
CaliciPicornaReoParvo AdenoPapillomaPolyoma
Purified nucleic acids of most dsDNA and (+) strand genome ssRNA viruses are ________?
Infectious
dsDNA of Poxviruses and HBV
Not infectious
Naked nucleic acids of (-) strand ssRNA and dsRNA viruses are _____?
Not infectious
Infectious particles composed entirely of protein which cause transmissible spongiform encephalopathies
Prions
Non-pathogenic prions
Alpha helix
Pathogenic prions
Beta-pleated sheet
All viruses are haploid EXCEPT
Retroviruses
Segmented Genome Viruses
BunyavirusesOrthomyxovirusesArenavirusesReoviruses
Negative strand RNA viruses
ArenavirusesBunyavirusesParamyxovirusesOrthomyxovirusesFilovirusesRhabdoviruses
Causes epidemics
Genomic reassortment
One virus produces a protein that can be used by another virus
Complementation
Two different viruses infect the same cell
Phenotypic mixing
Viral Growth Curve: A single virus particle infects a cell
Phase 0: Entry
Viral Growth Curve: Virus decreases in number but continues to function
Phase 1: Decline
Viral Growth Curve: No virus is detectable inside the cell
Phase 2: Eclipse Period
Viral Growth Curve: Dramatic increase in amount of detectable viruses
Phase 3: Rise Period
Viral Growth Curve: Amount of detectable viruses reaches a plateau
Phase 4: Latent Period
Viral Growth Curve: Marked derangement of cell function leading to lysis and cell death; Remarkable amplification in number of viral particles
Phase 5: Cytopathic Effect
Visual or functional change in infected cells
Cytopathic effect
Oncogenic viruses induce transformation and unrestrained growth
Malignant transformation
Infected cells appear normal, but are producing large numbers of progeny viruses
Commensal symbiosis
Bind cytokines and block their ability to interact with receptors on their intended targets
Cytokine decoys
Reduce the expression of antigen presenting cells and inactivate complement
Virokines
Produce virus for long periods of time; Can serve as a source of infection for others
Carrier state
Not producing virus at the present but can be reactivated at a subsequent time
Latent infections
Long incubation period, often measured in years
Slow virus infections
Attachment of RBCs to surface of infected cells
Hemadsorption
Interference with CPE by another virus
Interference
Finding antibody in one who previously had none
Seroconversion
Can be used to diagnose current infection
Presence of IgM
Cannot be used to diagnose current infection; Detect past or chronic infection
Presence of IgG
Gold Standard in Viral diagnosis
Presence of viral DNA or RNA
Induce humoral and cell-mediated immunity but may revert to virulence on rare occasions; Dangerous to give to immunocompromised patients or their close contacts
Live-attenuated Vaccines
The only live-attenuated vaccine that can be given to HIV (+) patients
MMR
Live-attenuated Vaccines
Yellow feverVaricella zosterSabin’s PolioMMR
Induce only humoral immunity but are stable
Killed vaccines
Killed Vaccines
RabiesInfluenzaPolio (Salk’s)Hepatitis A
Recombinant Vaccines (Synthetic)
Hepatitis B (recombinant HBsAg)HPV (types 6,11,16,18)
DNA viruses
HepadnaHerpesAdenoPoxParvoPolyomaPapilloma
All DNA viruses have double-stranded DNA EXCEPT
Parvovirus (single-stranded)
All DNA viruses have linear DNA EXCEPT
PapillomaPolyomaHepadna
All DNA viruses are icosahedral EXCEPT
Poxvirus
All DNA viruses replicate in the nucleus EXCEPT
Poxvirus
Mode of Transmission: Parvovirus B19
RespiratoryTransplacental
Mode of Transmission: Adenovirus
RespiratoryFecal-oral
Mode of Transmission: Human Papillomavirus
SexualSkin contact
Naked virus with icosahedral symmetry; Single stranded DNA genome; One serotype; Transmission: respiratory droplets and transplacental
Parvovirus B19
Bright red cheeks (slapped cheeks) with fever, coryza and sore throat
Erythema infectiosum (Fifth Disease)
Transient but severe aplastic anemia in children; Sickle cell anemia, Thalassemia, Spherocytosis
Aplastic Crisis
Pancytopenia in immunodeficient patients
Chronic B19 Infection
Naked viruses with double-stranded linear DNA and an icosahedral nucleocapsid; Only virus with fiber; 41 antigenic types; Transmission: aerosol droplet, fecal-oral, direct contact
Adenovirus
Spectrum of Disease of Adenovirus: URT
PharyngitisConjunctivitisCoryza
Spectrum of Disease of Adenovirus: LRT
BronchitisAtypical Pneumonia
Spectrum of Disease of Adenovirus: GIT
Acute Gastroenteritis
Spectrum of Disease of Adenovirus: GUT
Hemorrhagic cystitis (Cowdry type B intranuclear inclusions)
Most common cause of Pediatric Viral Gastroenteritis?
Rotavirus
Naked viruses with double-stranded circular DNA and an icosahedral nucleocapsid; at least 100 types; Transmission: direct contact or sexually
Human Papilloma Virus
Infect squamous cells and induce formation of cytoplasmic vacuole
Koilocytes
Encode proteins that inactivate tumor suppressor genes
Genes E6 and E7
Skin and plantar warts
HPV 1-4
Genital warts and respiratory tract papillomas; Most common viral STD
HPV 6-11
Carcinoma of cervix, penis, and anus
HPV 16, 18, 31, 33
Gold Standard for diagnosis of HPV
PCR
Treatment for Genital warts
Podophyllin
Treatment for Skin warts
Liquid nitrogen
Treatment for Plantar warts
Salicylic acid
Only causes disease in immunocompromised hosts; Causes progressive multifocal leukoencephalopathy (PML) in pts with AIDS
JC Polyoma Virus
Most common Demyelinating disease
Multiple sclerosis
Only causes disease in immunocompromised hosts; Causes hemorrhagic cystitis and nephropathy in patients with solid organ and bone marrow transplants
BK Polyoma Virus
Most common cause of Adult Viral Gastroenteritis?
Norwalkvirus
Herpes Viruses
CMVHSVEBVVZV
Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA; Multinucleated giant cells on Tzanck smear; Large, pink to purple intranuclear inclusions (Cowdry type A)
Herpes Simplex Viruses
Transmission of HSV 1
Saliva or direct
Transmission of HSV 2
Sexual or transvaginal
Site of latency of HSV 1
Trigeminal ganglia
Site of latency HSV 2
Lumbosacral ganglia
Spectrum of Disease of HSV 1
GingivostomatitisHerpes labialis (lips)KeratoconjunctivitisTemporal lobe encephalitisHerpetic whitlow (fingers)Herpes gladiatorum (trunk)
Spectrum of Disease of HSV 2
Genital herpesNeonatal herpesAseptic meningitis
DOC of HSV
Acyclovir
Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA; Transmission: Respiratory droplets and by direct contact with lesions; Multinucleated giant cells with intranuclear inclusions
Varicella zoster virus
Incubation period: 14-21 days; Vesicular centrifugal rash (dewdrop on a rose petal appearance); Complication: pneumonia, encephalitis, Reye’s Syndrome
Varicella
Reye’s Syndrome
FeverVomitingFatty liverKidney swellingBrain swelling
Uses of Aspirin in Pediatric Diseases
KawasakiARFJRA
Painful vesicles along dermatomal distribution; Debilitating pain (Postherpetic neuralgia)
Zoster
Involvement of geniculate ganglion causes facial nerve paralysis
Ramsay Hunt Syndrome
Treatment of VZV
Acyclovir
Enveloped virus with icosahedral nucleocapsid and linear dsDNA; Cultured in shell tubes; Negative heterophil test; Transmission: human body fluids, across the placenta, organ transplantation; Giant cells with owl’s-eye nuclear inclusions
Cytomegalovirus
Most common cause of Congenital abnormalities; Microcephaly, seizures, deafness, jaundice, purpura; Most common when mother infected in 1st trimester
Congenital CMV infection
Fever, lethargy, and abnormal lymphocytes in peripheral blood smears
Heterophil-negative Mononucleosis
Pneumonitis, Hepatitis, colitis, retinitis in immunocompromised patients
Systemic CMV infections
DOC of CMV
Ganciclovir (CMV is largely resistant to acyclovir)
Enveloped virus with icosahedral nucleocapsid and linear ds-DNA; Transmission: saliva; Infects mainly lymphoid cells, primarily B lymphocytes; Elicits EBV-specific antibodies and non-specific heterophil antibodies
Epstein-Barr Virus
“Kissing disease”; Fever, sore throat, lymphadenopathy, and splenomegaly; Splenic rupture is a rare complication
Infectious mononucleosis
Malignancies associated with EBV
Burkitt’s Lymphoma in African peopleB cell LymphomasNasopharyngeal carcinoma in Chinese peopleHairy leukoplakia in AIDS patients
Malignancy of vascular endothelial cells; Skin lesions: dark purple, flat to nodular, and often appear at multiple sites
Kaposi’s Sarcoma (Human Herpesvirus - 8)
Only disease that has been eradicated from the face of the earth; Largest viruses; Brick-shaped poxvirus containing linear dsDNA; Transmission: aerosol or contact; Prodrome of fever and malaise followed by centrifugal rash
Smallpox (Variola virus)
Intracytoplasmic eosinophilic inclusions of Variola virus
Guarnieri bodies
Pinkish, papular skin lesions with an umbilicated center; Transmission: direct contact
Molluscum contagiosum
Intracytoplasmic eosinophilic inclusions of Molluscum contagiosum
Henderson-Peterson bodies
Treatment of Molluscum contagiosum
Cifodovir
Enveloped virus with incomplete circular double-stranded DNA; Transmission: blood, during birth, sexual
Hepatitis B virus
HBsAg
Surface antigen
HBcAg
Core antigen
HBeAg; marker of viral replication
E antigen
IgM HBcAg
Acute infection
IgG HBcAg
Chronic infection
Only DNA virus that produces DNA by reverse transcription with mRNA as the template; No cytopathic effect; Incubation period: 10-12 weeks; Fever, anorexia, jaundice, dark urine, pale feces, elevated transaminase levels
HBV
HBV associated with autoimmune vasculitides
Polyarteritis Nodosa (PAN)
Associated malignancy with HBV
Hepatocellular carcinoma
HBV Complication: Functional renal failure without renal pathology
Hepatorenal Syndrome
HBV Complication: Vascular dilatations cause overperfusion relative to ventilation, leading to VQ Mismatch and Hypoxemia
Hepatopulmonary Syndrome
Treatment of HBV
Interferon-alphaLamivudine
All RNA viruses have single-stranded RNA EXCEPT
ReovirusRotavirus
All RNA viruses replicate in the cytoplasm EXCEPT
InfluenzaRetrovirus
Picornaviridae
PoliovirusEchovirusRhinovirusCoxsackievirusHepatitis A virus
Naked nucleocapsid with single-stranded, positive polarity RNA; Oral-fecal transmission; replicates in motor neurons in anterior horn of spinal cord causing paralysis
Poliovirus
Most common clinical form of Poliovirus; Mild, febrile illness with headache, sore throat, nausea, and vomiting
Abortive Poliomyelitis
Aseptic meningitis of Poliovirus
Nonparalytic Poliomyelitis
Flaccid paralysis; Permanent motor nerve damage; Most severe
Paralytic Poliomyelitis
Intranuclear inclusions of Poliovirus
Cowdry Type B
Naked nucleocapsid with single stranded, positive polarity RNA; Transmission: oral-fecal
Coxsackie virus
Fever, sore throat, and tender vesicles in oropharynx
Herpangina
Vesicular rash on hands and feet and ulcerations in the mouth
Hand-foot-and-mouth Disease
Fever and severe pleuritic-type chest pain
Pleurodynia
Most common cause; Fever, chest pain, and signs of congestive failure
MyocarditisPericarditis
Most common cause of Aseptic Meningitis
Coxsackie Virus
Enteroviruses
Coxsackie virusPoliovirusEchovirus
Called “orphans” because they were not initially associated with any disease; Now known to cause aseptic meningitis, URTI, febrile illness with or without rash, infantile diarrhea, hemorrhagic conjunctivitis; Transmitted by fecal-oral route
Echovirus (Enteric Cytopathic Human Orphan)
Naked nucleocapsid viruses with single-stranded, positive-polarity RNA; More than 100 serotypes; Transmitted by aerosol droplets and hand to nose contact
Rhinovirus (Common colds)
Naked nucleocapsid virus with a ss-positive-RNA; Fecal-oral transmission; Children most frequently infected; Self limited hepatitis; 1 serotype; no antigenic relationship to HBV or other hepatitis
Hepatitis A aka Enterovirus 72
Most important test for HAV
Anti-HAV IgM
Fecal-oral route; No chronic carrier state; No cirrhosis; No hepatocellular carcinoma; high mortality in pregnancy women
Hepatitis E virus
Non enveloped virus with icosahedral nucleocapsid and one piece of single-stranded, positive-polarity RNA; Oral-fecal transmission; Most common cause of nonbacterial diarrhea in adults; sudden onset of vomiting and diarrhea accompanied by fever and abdominal cramping
Viral Gastroenteritis (Norwalk virus)
Enveloped virus with a helical nucleocapsid and segmented, ss-negative RNA; Major antigens are hemagglutin (H) and neuraminidase (N); Respiratory droplet transmission
Influenza virus
Worldwide epidemics (pandemics) each year; Most common cause of respiratory tract infections
Influenza A
Major outbreaks of influenza; Does not lead to pandemic
Influenza B
Mild respiratory tract infections but does not cause outbreaks of influenza
Influenza C
Binds to the cell surface receptor (neuraminic acid, sialic acid) to initiate infection of the cell; The target of neutralizing antibody; Infective
Hemagglutinin
Cleaves neuraminic acid (sialic acid) to release progeny virus from the infected cell; Also degrades the protective layer of mucus in the respiratory tract which enhances access to the respiratory epithelial cells
Neuraminidase
Major changes based on the reassortment of segment of the genome RNA
Antigenic Shifts (Pandemics)
Minor changes based on mutations in the genome RNA
Antigenic Drifts
DOC of Influenza
Oseltamivir or Zanamivir(Amantadine or Rimantadine for Influenza A only)
Paramyxoviruses
ParainfluenzaRSVMeasles Mumps
Enveloped virus with helical nucleocapsid and one piece of single stranded, negative polarity RNA; Respiratory droplet transmission
Measles virus
Multinucleated giant cells of Measles virus
Warthin-Finkeldey bodies
Bright red lesions with a white, central dot on buccal mucosa; Pathognomonic
Koplik’s spots
Complications of Measles virus
EncephalitisPneumoniaSubacute sclerosing panencephalitis (SSPE) or Damson Disease
Cardinal manifestations of Measles
Cough CoryzaConjunctivitisKoplik spots
Enveloped virus with a helical nucleocapsid and one piece of single-stranded, negative-polarity RNA; Respiratory droplet transmission; initially infects URT; tender swelling of parotid glands (parotitis)
Mumps virus
Most common benign Parotid Tumor
Pleomorphic adenoma
Surface spikes (fusion proteins); Causes cells to fuse, forming mutinicleated giant cells (syncytia), which give rise to the name of the virus; human host
Respiratory Syncitial Virus
Most important cause of Pneumonia and Bronchiolitis in infants; Severe disease in infants due to immunologic cross reaction with maternal antibodies
RSV pneumonia
Treatment of RSV Pneumonia
Ribavirin
Characterized by inspiratory stridor, cough and hoarseness; Steeple sign on x-ray
Laryngotracheobronchitis (Croup)
Treatment of Croup
Racemic Epinephrine
Bullet-shaped enveloped virus with helical nucleocapsid and one piece of single-stranded, negative-polarity RNA; Animal reservoir; Transmission: animal bite
Rabies virus
Intracytoplasmic histologic presentation
Negri bodies
WHO Guidelines for Post Exposure Prophylaxis: Category I
No treatment
WHO Guidelines for Post Exposure Prophylaxis: Category II
Vaccine
WHO Guidelines for Post Exposure Prophylaxis: Category III
Vaccine + Immunoglobulin
Enveloped virus with helical nucleocapsid and one piece of single-stranded, Positive-polarity RNA; Prominent club-shaped spikes form a “corona”; 2 serotypes; respiratory droplet transmission
Coronavirus (Common colds)
Atypical pneumonia rapidly progressing to ARDS; Virus binds to ACE-2 receptor; Chest x-ray: non-cavitary “ground-glass” infiltrates
Severe Acute Respiratory Syndrome (SARS)
Enveloped virus with icosahedral nucleocapsid and one piece of single-stranded, positive-polarity RNA; 4 serotypes; transmitted by Aedes aegypti; Diagnosed using dengue IgM; Leukopenia, Thrombocytopenia, increased hematocrit
Dengue virus
Influenza-like syndrome with maculopapular rash and severe pains in muscles and joints
Breakbone Fever
Enveloped virus with one piece of single-stranded, positive-polarity RNA; hypervariable region in envelope glycoprotein; 6 serotypes; Most prevalent blood-borne pathogen
Hepatitis C virus
Replication of HCV in liver is enhanced by
Liver-specific micro-RNA
HCV is the main cause of
Essential mixed cryoglobulinemia
Treatment of Acute Hepatitis C
Interferon
Treatment of Chronic Hepatitis
Peg-interferon and Ribavirin
Most common indication for _____ for severe cirrhosis
Liver Transplantation
Enveloped virus with an icosahedral nucleocapsid and one ss-positive-RNA; Respiratory droplet or transplacental transmission
Rubella Virus
Incubation period: 14-21 days; Prodrome followed by 3-day maculopapular rash and posterior auricular LAD; immune-complex polyarthritis in adults
German Measles
Infected during the 1st trimester; Associated abnormalities: patent ductus arteriosus, congenital cataracts, sensorineural deafness, mental retardation
Congenital Rubella Syndrome
5 Bs of Congenital Rubella Syndrome
Bulag (cataracts)Bingi (sensorineural deafness)Bobo (mental retardation)Butas ang puso (PDA)Blue berry muffin baby
Distinguished from all other RNA viruses by the presence of an unusual enzyme, reverse transcriptase which converts a single-stranded RNA viral genome into double-stranded viral DNA
Retroviridae
Enveloped virus with two copies (diploid) of a single-stranded, positive-polarity RNA genome; most complex of the known retroviruses; many serotypes
Human Immunodeficiency Virus
Fusion protein of HIV; Mediates the fusion of the viral envelope with the cell membrane at the time of infection
gp41
Attachment protein of HIV; Interacts with CD4 receptor; Gene mutates rapidly (many antigenic variants); High mutation rate may be due to lack of an editing function in the reverse transcriptase
gp120
Capsid protein of HIV; Group-specific antigen, located in the core, not known to vary, antibodies against p24 do not neutralize HIV infectivity but serve as important serologic markers of infection
p24
Outer matrix protein of HIV
p17
Nucleoprotein of HIV
p7
Gene that encodes p24, p7, p17
gag Gene
Gene that encodes reverse transcriptase, protease, integrase
pol Gene
Gene that encodes gp120 and gp41
env Gene
Most immunogenic region of gp120
V3 loop
Activation of transcription of viral genes
tat Gene
Transport of late mRNAs to cytoplasm
rev Gene
Decreases CD4 and Class I MHC proteins
nef Gene
Enhances hypermutation
vif Gene
Transport in non-dividing cells
vpr Gene
Enhances virion release
vpu Gene
Preferentially infects and kills helper (CD4+) T lymphocytes; Loss of cell-mediates immunity; High probability of opportunistic infections; Main immune response consists of cytotoxic (CD8+) lymphocytes
HIV
Stages of HIV Infection: HIV acquired through sexual intercourse, blood, or perinatally
Phase 0: Infection
Stages of HIV Infection: Rapid biral replication but HIV test is negative
Phase 1: Window Period
Stages of HIV Infection: Peak of viral load, positive HIV test, mild flu-like illness, lasting 1-2 weeks
Phase 2: Seroconversion
Stages of HIV Infection: Asymptomatic, CD4 goes down, lasts 1-15 years
Phase 3: Latent Period
Stages of HIV Infection: CD4 500-200, lasts 5 years, mild mucocutaneous, dermatologic and hematologic illness
Phase 4: Early Symptomatic
Stages of HIV Infection: CD4
Phase 5: AIDS
AIDS-defining Illness: CD4
M. tuberculosis (dissiminated tuberculosis)HSV (HSV esophagitis)C. albicans (esophageal candidiasis)HHV-8 (Kaposi’s sarcoma)
AIDS-defining Illness: CD4
P. jiroveci (PCP pneumonia)T. gondii (cerebral toxoplasmosis)C. neoformans (meningoencephalitis)C. immitis (coccidiomycosis)C. parvum (chronic diarrhea)
AIDS-defining Illness: CD4
M. avium (invasive pulmonary disease)H. capsulatum (histoplasmosis)CMV (CMV retinitis)
Screening test for HIV
ELISA
Confirmatory test for HIV (For Definitive Diagnosis)
Western blot Analysis
Used for Prognostication of HIV
PCR
Treatment of HIV
Highly active antiretroviral therapy (HAART)
Retrovirus causing Adult T-cell leukemia and HTLV-associated myelopathy; HP: malignant T cell with flower-shape nucleus
Human T-cell Lymphotropic Virus (HTLV)
Thread-like viruses; Longest viruses; Outbreak of hemorrhagic fever; 100% mortality
Ebola Virus (Ebola Hemorrhagic Fever)
Flavivirus; Bird-mosquito-man cycle; Initial self limited febrile illness with progression to neuroinvasive disease
West Nile Virus (West Nile Fever)
Membrane of flavivirus; Most common cause of epidemic encephalitis; most prevalent in SEA; Transmitted by Culex mosquitoes; Thalamic infarcts on CT Scan
Japanese B Virus (Japanese B Encephalitis)
