Viral Disease Flashcards
viruses damage host cells by
entering the cell and replicating at the host expense
Steps in virus infection and replication
- attachment to host cell
- host cell penetration
- viral uncoating
- viral replication
- re-assembly of virions
Attachment to host cell involves
viral tropisms
special enzymes or promotor elements in host cells
Examples of viral tropisms
HIV - CD4
EBV - complement CD21 receptor on macrophages
rabies - acetylcholine receptor
rhinoviruses - ICAM-1
types of viral infections
abortive; latent; persistent
Mechanisms of host cell death
- inhibition of host RNA, DNA, protein synthesis
- viral proteins damage host membrane integrity or promote cell fusion
- replicate and lyse host cells
- antiviral host responses with recognition of viral antigens on infected host cell
- secondary infections due to suppression of host immune response
- secondary loss of cells dependent on infected cells
- transformation by oncogenic virus resulting in neoplasia
Acute viral infections are generally controlled by
cell-mediated (CD8) responses to virally infected cells; restricted to viral antigen + MHC class I molecules
antibody serves two purposes
- to control blood borne dissemination (viremia)
2. control reinfection (protective immunity) - often by interfering with attachment or viral release
Vaccination can induce
either a humoral or cell-mediated response
antigenic shift
recombination of RNA segments with those of animal viruses to cause changes in hemagglutinin and neuraminidase (pandemics)
antigenic drift
mutations of hemagglutinin and neuraminidase that allow virus to escape host antibodies (epidemics)
isotype shift of antibody from IgM to IgG is indicative of
prior infection with or without current infection
IgM = recent infection
IgG = prior infection
antiviral functions of antibody
neutralization (prevent attachment/interfere with viral uncoating)
opsonization
complement-mediated cell and/or virion lysis
role of antibody in disease states
- immune complex reactions - arthralgias/glomerulonephritis
2. may enhance cell uptake and promote infection
epithelial necrosis and sloughing
influenza
inclusion bodies
CMV, adenovirus
syncytial cells
measles, herpes viruses, retroviruses
blisters
discohesion of epithelial cells as with herpes virus, varicella-zoster
dysplastic changes to neoplastic transformation
papillomavirus
CMV inclusions
distinct intranuclear and ill-defined cytoplasmic inclusions
Herpes, varicella inclusions
Cowdry type A intranuclear inclusion bodies
Rabies
Negri bodies; cytoplasmic inclusion bodies
Papillomavirus
koilocytes
Hepatitis
Councilman bodies (necrotic cells)
Measles
Warthin-Finkeldey giant cells with intracytoplasmic and intranuclear inclusion bodies
Adenovirus
smudge cells and Cowdry type A intranuclear inclusion bodies
reactive lymphoid hyperplasia
EBV (B cells), measles (giant cells), mumps
infection spread by food/water
Hepatitis A
infection spread by aerosolized droplets
influenza, adenovirus, rhinovirus
infection spread by cells or body fluids
EBV, HIV, herpes etc
Respiratory viruses
- adenovirus
- rhinovirus
- influenza
- measles
- RSV
- coronavirus
- CMV
GI viruses
- poliovirus
- coxsackie
- echovirus
- rotavirus
- Hep A/B/C
- Norwalk agent
Encephalitis/Hemorrhagic fever viruses
- Rubella
- Yellow Fever
- Dengue
- Hanta
- Mumps