Effects-Responses (Ex1) Flashcards
What is Cytopathic effect?
damage or morphological changes to host cells during virus invasion
What are some Cytopathic effects?
- complete destruction of cells (all cells shrink, become dense, and detach from glass) - subtotal destruction of cells (detachment of some cells) - focal destruction of cells (localized areas of infection)
What is Pykonosis?
a degenerative condition of a cell nucleus marked by clumping of the chromosomes, hyperchromatism, and shrinking of the nucleus
Explain Cell Fusion
- fusion of plasma membranes of four or more cells
- fusion of infected cell with adjacent infected or non-infected cells
- prone to premature cell death
General Mechanisms of Virus-Induced Cell Injury and Death (4)
- inhibition of host-cell nucleic acid synthesis
- inhibition of host-cell RNA transcription
- inhibition of host-cell protein synthesis
- interference with cellular membrane function
Describe the Intrinsic Pathway of apoptosis
- Mitochondrial pathway
- activated as a result of increased permeability of mitochondrial membranes
Describe the Extrinsic Pathway of apoptosis
- Death receptor pathway
- activated by engagement of specific cell membrane receptors
What is Cell Transformation?
the changing of a normal cell into a cancer cell
What is Neoplasia?
denotes an abnormal tissue overgrowth that may be either localized or disseminated
What is a Malignant Neoplasm?
locally invasive and may also spread to other parts of the body
- cancer
What are Oncogenic Viruses?
viruses that cause or give rise to tumors
What do Proto-oncogenes do?
- encode proteins that function in normal cellular growth and differentiation
- often involved in growth signaling and anti-apoptotic pathways
What are Oncogenes?
- mutated forms of proto-oncogenes
- function in an unregulated manner
What happens to a DNA tumor virus when it enters a permissive cell?
Non-permissive cell?
P: virus completes its replication cycle, and releases progeny virions
NP: virus does not complete replication, transforms the cell into cancer cell
Describe Retinoblastoma Protein
- un-phosphorylated Rb is active, and binds to transcription factor E2F, stopping cell division
- phosphorylated Rb is inactive, and releases E2F from its inhibition
What is the function of p53 Protein?
looks for cells with genetic defects and makes them undergo apoptosis
How do papillomas become malignant?
- integration of viral genome into host DNA disrupts viral repressor gene E2
- E6 and E7 are not regulated, so they cause the malignant transformation
Acutely Transforming Retrovirus
- host proto-oncogene becomes integrated into the viral DNA (v-onc)
- no longer paired with suppressor gene, there is no regulation
Slow/Chronic Transforming Retrovirus
- integration of viral genome at promoter or enhancer sites
- increase proto-oncogene expression
How do Innate Immune cells respond when their PRRs attach to PAMPs?
- express IFNs or cytokines
- activate phagocytic cells and endothelial cells with increased production of inflammatory mediators and expression of adhesion molecules
- macrophages initiate chemotaxis, bringing in neutrophils
Actions of Type-1 Interferons
- inhibit protein synthesis and DNA replication
- increase MHC 1 expression
- activate NK cells
- maturation of dendritic cells
- stimulate memory T cell proliferation
Actions of Type-2 Interferons
- immunoregulatory
- macrophage activation
- isotype switching
- development of TH1 effector cells
- increased MHC expression
Action of Type-3 Interferons
- immunoregulator
Describe Gene Silencing
- RNA is chopped into small pieces called short interfering RNA
- RNA-silencing complex is formed, containing endonuclease
- parts of the mRNA that are complementary to the RNAi bind, and are chopped off by the endonuclease
- so no protein synthesis and replication stops
What is virus neutralization?
antibodies prevent virus attachment and entry into host cells
What is opsonization?
antibodies coat the virions so they are recognized and phagocytosed by macrophages
What happens in Antibody-Dependent Cell-Mediated Cytotoxicity?
- antibodies bind to viral antigens expressed on surface of host cells
- host cells destroyed
What is Antigen Plasticity?
- rapid changes in the structure of the viral antigen
- virus may become resistant to immunity
- antigenic drift, shift
What is Antigen Multiplicity?
- antigenic variants with little or no cross-reactivity
- multiple serotypes, immunity may not work against all of them
What is Negative Cytokine Regulation?
- blocking interferon receptor signal
- virokines: homologs of cytokines produced by virus
- viroreceptors: homologs to cytokine receptors, act as competitive antagonist
