Virology Flashcards
Adenovirus
DNA Naked Double stranded
Most common cause of TONSILLITIS
•Hemorrhagic cystitis
•Viral conjunctivitis
Transmission: Respiratory droplet, Feco-oral route
Vaccination: Live attenuated
BK Virus
Naked
double stranded
CIRCULAR
Hemorrhagic cystitis
Nephropathy
Transplant patients
JC Virus
Naked
DOUBLE STRANDED
CIRCULAR
Area: Oligodendrocytes
Progressive Multifocal LEUKOEncephalopathy - demyelinating
NON ENHANCING lesions on CT and MRI
CD4 <200
The protein shell, or coat that encloses the nucleic acid genome
Capsid
Morphologic units seen in the electron microscope on the surface of icosahedral virus particles
Capsomeres
A virus particle that is functionally deficient in some aspect of replication
Defective virus
Ex Hepa D
A lipid-containing membrane that surrounds some virus particles
Envelope
The protein nucleic acid complex representing the packaged form of viral genome
Nucleocapsid
The complete virus particle
Virion
Hepatitis B virion
Dane
Modes of Viral Multiplication
The host cell is absolutely necessary for viral multiplication
Multiplication cycles in animal viruses
Adsorption Penetration Uncoating Synthesis Assembly Release
Virus encounters susceptible host cells
Adsorbs specifically to receptor sites on the cell membrane
Because of the exact fit required, viruses have a limited host range
Adsorption
Flexible cell membrane of the host is penetrated by the whole virus or its nucleic acid
Penetration
Entire virus engulfed by the cell and enclosed in a vacuole or vesicle
Endocytosis
Form ofPenetration
The viral envelope can also directly fuse with the host cell membrane
Penetration
Enzymes in the vacuole dissolve the envelope and capsid
The virus is now uncoated
Uncoating
Free viral nucleic acid exerts control over the host’s synthetic and metabolic machinery
DNA viruses enter host cell’s nucleus where they are replicated and assembled
DNA enters the nucleus and is transcripted into RNA
The RNA becomes a message for synthesizing viral proteins (translation)
New DNA is synthesized using host nucleotides
RNA viruses recplicated and assembled in the cytoplasm
Synthesis
Only DNA virus that replicates in cytoplasm
Pox virus
Mature virus particles are constructed from the growing pool of parts
Assembly
Nonenveloped and complex viruses are released when the cell lyse or ruptures
Enveloped viruses are liberated by budding or exocystosis
Anywhere from 3,000 to 100,000 virions may be released, depending on the virus
Entire length of cycle - anywhere from 8 to 36 hours
Release
Stages of Viral Infection in the Cellular Level
Viral interactions with a host’s cell surface
Viral entry into a host cell
Viral gene expression and replication
Viral assembly and release
Only DNA Hepadna virus
Hepa B
Single stranded DNA
Parvoviridae
Circoviridae
Picornaviridae
Polio
Hepatitis A
Bullet-shaped virus
Rhabdoviridae
Crown-shaped spike
Corona virus
Viruses can directly damage host cells by entering them and replicating at the host’s expense
Viruses may inhibit host cell DNA, RNA or protein synthesis
Viral proteins may directly damage host cell’s plasma membrane
Viruses may lyse host cells
Viruses may manipulate programmed cell death
Viruses nay cause malignant transformation
Mechanism of viral injury
Viruses that lead to malignant transformation
Hep B, Hep C
HPV
EBV (NPC, Burkitt’s, Hodgkin)
Oncogenic virus
Four main morphological virus types
Helical virus
Icosahedron virus
Enveloped virus
Complex virus
Iceberg concept of infection
Base: exposure without attachment (below visual change) or entry; exposure without infection (subclinical)
Viral multiplication without visible change or incomplete viral maturation (below visual change) or infections without clinical illness (asymptomatic infection)
Discernible effect/Apex: inclusion body formation, cell transformation, cell dysfunction
Clinical disease/Apex: moderate severity, mild illness; classic and severe disease (clinical disease)
RBC viral predilection
Parvo B19 (DNA) Pure red cell aplasia
Colorado tick fever virus (RNA)
Monocyte-macrophages predilection
CMV (DNA)
Poliovirus, HIV, measles (RNA)
No cell associated type but bloodstream
Togavirus
Picornavirus
Lymphocyte predilection
EBV, CMV, Hepa V, JC, BK (DNA)
Common cold viral cause
Rhinovirus
Adeno (infant and children)
Corona (adult)
Pharyngitis viral cause
Adenovirus
HSV (infant)
Coxsackie A (children, adult)
Laryngitis or croup viral cause
Tracheobronchitis
Hoarseness “barking” cough
Parainfluenza
Influenza
Bronchiolitis viral cause
Pneumonia
RSV
Subtypes of inlfuenza
A, B, C
2 major influenza antigens
Hemagluttinin (H)
Neuramidase (N)
16 H And 9 N
Influenza A virus subtype H5N1
Avian flu
Influenza A virus subtype H1N1
Swine flu
Most famous segmented virus
Influenza an orthomyxovirus
8 segments that can reassort antigenic drifts and shifts
Influenza A
The two surface antigens of influenza undergo antigenic variation independent of each other
Minor antigenic change is termed
Causes seasonal variation
Antigenic drift
Major antigenic change in HA or NA is called
Results in appearance of a new subtype as in epidemic
Antigenic shift
Antigenic drift is caused by
Accumulation of point mutations in gene
Resulting in amino acid changes in the protein
Sequence changes can alter antigenic sites
Reflects drastic changes in the sequence of a viral surface protein, changes too extreme to be explained by mutation
The segmented genomes of influenza viruses reassort readily in double infected cells
Antigenic shift
All three types of influenza exhibit antigenic drift
Only this type that undergoes antigenic shift because the other types are restricted to humans
Influenza A circulate in animal and bird populations
Account for antigenic shift by genetic reassortment of the glycoprotein genes
Influenza A
Family Parvoviridae
Affects RBCs
Parvo virus
4 Syndromes Associated with Parvo viridae
Erythema infectiosum (Fifth disease)
Transient aplastic crisis (underlying hemolysis)
Pure red cell aplasia (immunodeficiencies)
Hydrops fetalis
Slapped cheek appearance
Lacy appearing rash
Erythema infectiosum
Fifth’s disease
Parvo B19
Causes of hemorrhagic fever
Filovirus
Marburg virus
Ebola virus
Flu like symptoms
Stomach ache
Impaired kidney and liver function
Both internal and external bleeding
Rash, red eyes, hiccup
Ebola virus
Acute febrile illness associated with abrupt onset of headache, myalgia, fever leading to -> rash, shock and bleeding
Ebola virus