Pathogenesis of Viral Diseases Flashcards
Expression of the viral replicative cycle (partial or complete) in a host cell
Viral infection
May range from no apparent effect to cytopathology with accompanying cell death to hyperplasia or cancer
Cellular response
9 Effects of Virus Infection on the Host Cell
- Cytopathic effects
- Inhibition of host macromolecular biosynthesis
- Changes in regulation of gene
- Appearance of new antigenic determinants on the cell surface
- Cell fusion
- Concept of Permissiveness
- Latency
- Inapparent Infections
- Modification of Cellular Permissiveness
Most easily detected effects of infection with lytic viruses
- Plaque formation
- Inclusion bodies
- Cell degeneration
- Viral proteins has the ability to fuse membranes
3 Macromolecular biosynthesis that is inhibited:
- host protein synthesis
- host DNA replication
- host RNA synthesis
Example of host genome expression
Inducing synthesis of a new protein, interferon
Cellular genes that may be expressed in uninfected cells
- Large T-antigen of papovaviruses
- Adenovirus EIA protein
Modifications of the outer cell membrane
- Cellular morphology changes
- Cells become more agglutinate
- Cell membrane permeability increases
- Antigenic determinants appear on the cell surface
Masses of cytoplasm bounded by one membrane containing hundreds or thousands of nuclei
Giant syncithia
Cell fusion is caused by?
- Glcoproteins in viral envelopes ( glyco P;glyco B and glyco D) in herpes virus envelopes
- F spike glyco P of pamyxovirus
2 concepts of permissiveness
site of predilection
certain viruses can grow only in a few types of cells
2 examples of cells affected by abortive infection
Hela cells
Dog kidney cells
Name the infection. Viruses cannot multiply because some essential step of the multiplication cycle cannot proceed
Abortive infective
Name the infection. Stable relationship between cell growth and virus multiplication
Persistent infections
An effect of virus infection. Persistently infected cells in which no infectious virus formed because the multiplication cycle is completely rested at some stage
Latency
In the latency effect of virus infection what may resume after a period of several weeks to many years, and infectious virus may then be formed and released
Multiplication cycle
Examples of viruses of latency effect
Herpesviruses: HSV 1 & 2, Varicella Zoster, EBV, CMV
Multiplication and gene expression occur at so low level that their presence can only be detected by a very special measure
Inapparent infections
Example of virus in inapparent infections
papovirus BKV, papovirus JCV
Infects most individuals by adolescence and sets up minute and inapparent foci of infection in kidneys and in cells lining the urinary tract
Papovavirus BKV
What inaparent infection is caused by measles
Subacute sclerosing panencephalitis (SSPE)
What inapparent infection is caused by papovavirus JCV
Progressive multifocal leukoencephalopathy (PML)
HSV grow on neuroblastoma cells >1000x if the cells are treated by what?
sodium butyrate
What virus multiply only in the cells infected with adenovirus?
Adenoaasociated virus (AAV)
What enables adenovirus to grow in monkey cells?
SV40
Examples of poxvirus that enable VSV to multiply in rabbit cells
- vaccinia
- fibromavirus
What is the host response when there is lysis of cell?
death of organism
What is the cell response when there is exposure without infection
Exposure without attachment and/or cell entry
Abnormality that results from viral infection of the host organism
Viral disease
With overt signs and symptoms
Clinical disease
Fail to produce any symptoms in the host
Subclinical infection
True or false. Many viral infections are clinical.
False
True or false. The disease bears a relationship to viral mophology.
False
Interaction of viral host factors that leads to disease production
Viral pathogenesis
If it can infect and cause signs of disease in the host
Pathogenic
Fifth step in viral pathogenesis
Host immune response
First step in viral pathogenesis
Viral entry into the host
Last step step in viral pathogenesis
Viral shedding
Second step in viral pathogenesis
Primary viral replication
Third step in viral pathogenesis
Viral spread
Sixth step in viral pathogenesis
Viral clearance/establishment of persistent infection
Fourth step in viral pathogenesis
Cellular injury
Viruses that cause local symptoms at the respiratory tract
Adenovirus, Corona virus, HSV, Parainfluenza, EBV, Influenza virus, Rhinovirus
2 most viruses that produce symptoms at the respiratory tract:
Adenovirus
Corona virus
Viruses producing generalized infection + specific organ disease
B19 (Parvovirus), Varicella virus, Smallpox virus, some Enterovirus, Rubella virus, Mumps virus, Measles virus
Viruses found in the mouth, intestinal tract
Adenovirus, EBV, Herpes simplex virus, Rotavirus
Viruses that enter in the mouth, intestinal tract and produce generalized infection + specific organ disease
Cytomegalovirus, Enteroviruses (some) [poliovirus, hepatitis A]
Name the viruses. Route of entry is in the skin and mild trauma.
Papillomavirus (most), Herpes simplex virus, Molluscum contagiosum virus, Orf virus
Name the virus. Route of entry is in the skin and through injection producing generalized infection + specific organ disease
Hepatitis B, Epstein-Barr virus, Cytomegalovirus, Human immunodeficiency virus
Name the viruses. Route of entry is the skin and through bites producing generalized infection + specific organ disease
Togavirus (many), Flavivirus, Rabies virus
Togavirus in skin and bites causes what disease?
Eastern equine encephalitis
Flavivirus in skin and bites causes what disease?
Yellow fever
True or false. Viruses produce disease at sites distant from their point of entry.
True
Example of virus that produce disease at sites distant from its point of entry.
Enterovirus
Presence of virus in the blood
Viremia
Virus spread via the ____________?
bloodstream
Cell type associated: Lymphocytes. Give the DNA viruses.
EBV, CMV, Hepatitis B, JC virus, BK virus
Cell type associated: Lymphocytes. Give the RNA viruses.
Mumps, measles, rubella, HIV
Cell type associated: Monocytes-macrophages. Give the DNA virus.
cytomegalovirus
Cell type associated: Monocytes-macrophages. Give the RNA viruses.
Poliovirus, HIV, measles
Cell type associated: Neutrophils. Give the DNA virus.
Influenza virus
Cell type associated: Red blood cells: Give the DNA viruses.
Parvovirus B19
Cell type associated:Red blood cells. Give the RNA virus.
Colorado tick fever virus
Cell type associated: None(free in plsma). Give the RNA viruses.
Togavirus, Picornavirus
True or false. All physiologic effects may result from nonlethal impairment of specialized functions of cells.
False. (Only some physiologic effects…)
Example of physiologic effects that may result from nonlethal impairment of specialized functions of cells
Loss of hormone production
Recovery from infection is through?
- Humoral and cell-mediated immunity
- Interferon and other cytokines
Reason for virus shedding
To maintain a viral infection in populations if hosts
True or false. Virus shedding usually occurs from the body surfaces involved in the viral entry.
True
Virus may be replicating but not producing any symptoms
Subclinical disease
Lasts for at least one week to two weeks
Acute infection
