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
Vesicular viruses
HSV1
HSV2
Varicella-Zoster
smallpox
Proliferative/Oncogenic viruses
- EBV
- Papillomavirus
- HIV
- HTLV
Neurotropic viruses
- HSV 1
- HSV 2
- Varicella Zoster
- Rabies
DNA viruses
- Herpes (1-8)
- Adenovirus
- hepatitis B
- Pox
- papilloma/JC
- parvovirus
RNA viruses
- Enteroviruses (polio, coxsackie, echo, hep A)
- Reo - rotavirus
- coronavirus
- Toga - rubella
- Flavi - yellow fever, dengue, hep C
- Orthomyxo - influenza
- Paramyxo - measles, mumps, RSV
- Hanta
- Filo - ebola
- Rhabdo - rabies
Retro viruses
HTLV
HIV
polio
enterovirus
infects tissues in oropharynx
secreted into saliva/swallowed
multiplies in intetinal mucosa and lymph nodes
1% invades CNS to replicate in motor neurons of spinal cord/brain stem
Upper respiratory viral syndromes
adenovirus
rhinovirus
echovirus
coronavirus
Lower respiratory viral syndromes (pneumonias)
influenza
parainfluenza
RSV
GI tract/liver viral syndromes
rotavirus
norwalk agent
hepatitis
rhinovirus
binds to ICAM-1
confined to URT, needs cooler environment
hypersecretion due to bradykinins and inflammatory response
over 100 serotypes
echovirus and coxsackie viruses
oral/fecal spread
organisms disseminate in blood stream after proliferation in lymphoreticular tissues
respiratory disorders primarily
coronavirus
second most common cause of common cold
profuse nasal discharge
little effect on lower respiratory tract
hemagglutinin binds
sialic acid-containing proteins and lipids on most cells and mediates entry into cell
neuraminidase plays a role in
releasing virus from host cells
Type A influenza major cause of
pandemic and epidemic flu infections
Type B and C infect
mostly children
pathology of influenzae
mucosal hyperemia with lymphomonocytic and plasmacytic infiltration of submucosa; hypersecretion
influenzae can also cause
interstitial myocarditis
associated with Reye’s syndrome
most deaths with pneumonia are due to
secondary bacterial pneumonias
parainfluenza
effects mostly children; mostly localized to URT except in infants where more serious lower respiratory infections occur
RSV
most common cause of viral pneumonia in children
adenovirus
common cause of acute respiratory disease and pnemonia in military recruits
COWDRY TYPE A INTRANUCLEAR INCLUSIONS
epithelial necrosis with sloughing
other important forms of viral pneumonias
herpes viruses including chickenpox (varicella)
CMV
herpes simplex
rotavirus
usually acute/self-limited, infectious diarrhea
major cause of diarrhea in infants/older children and adults are resistant to infection
Norwalk agent
epidemic viral gastroenteritis
naked icosahedryl nucleocapsids which cannot grow in cultured cells
HSV type I
gingivostomatitis, cold sores
HSV type II
genital herpes
HSV type I is major infectious cause of
corneal blindness
also cause of fatal sporadic encephalitis
causes disseminated disease in immunosuppressed
pathology of HSV I and II
fever blisters and cold sores in skin and mucous membranes
inclusion-bearing multinucleated syncytia (TZANCK PREP)
blisters associated with edema and ballooning degeneration
Congenital infection (TORCH syndrome):
generalized lymphadenopathy, splenomegaly, necrotic foci throughout; corneal lesions, CNS damage (deafness, ataxia)
Epstein-Barr
benign, self-limited, lymphoproliferative disease
fever, generalized lymphadenopathy, splenomegaly, sore throat
atypial lymphocytes on blood smear
EBV binds
to complement receptor on epithelial cells and B cells
When EBV infects B cells it causes
proliferation, lymphadenopathy, and polyclonal non-specific antibody synthesis
EBV immune response involves
heterophil anti-sheep red blood cell Abs used for diagnostic testing
latent EBV infection associated with
Burkitt’s lymphoma and nasopharyngela carcinoma
Diagnosis dependent on
- atyp8ical lymphocytes
- positive heterophil reaction
- specific antibodies for EBV antigens
HTLV associated with
T cell lymphomas
CMV characteristics
disseminated infection in imunosuppressed individuals and neonates characterized by large purple nuclear inclusions; focal necrosis with little inflammation
CMV infections in neonates from
intrauterine, perinatal and mother’s milk
devastating disease in neonates
In infants, CMV manifests as
hemolytic anemia jaundice thrombocytopenia purpura hepatosplenomegaly deafness chorioretinitis brain damage/encephalitis
most common opportunistic viral disease in AIDS patients
CMV
CMV infection in AIDS most always accompanied by
Pneumocystic carinii
HPV
proliferative lesions including common warts, plantar warts and cervical dysplasia
transmitted by direct contact
initially infect basal cells
Rabies
negri bodies, secreted in saliva
yellow fever and dengue
mosquito-borne (aedes aegyptii)
Ebola
filamentous mammalian viruses; neg. sense ssRNA
Manifestations of ebola
multihemorrhagic manifestations with DIC, shock
hepatic involvement
visceral organ necrosis
organ damage not sufficient to kills
Ebola death from
hemorrhage, shock, fluid loss
hanta virus
acute hemorrhagic pulmonary syndrome
fever, acute respiratory distress, hemorrhages, DIC
West Nile Virus
birds serve as major reservoir
transmitted by mosquitoes to birds and mammals
headahce, myalgia
meningitis/encephalitis/meningoencephalitis