Exam #2 Flashcards
Define in simple terms what is a virus.
A virus is made up of nucleic acids. They infect ALL groups of living cells. They do not exhibit the characteristics of a living organism, but they can regulate life functions of their host cells.
What are the characteristics of viruses. (6)
Viruses are filterable agents
Viruses are obligate intracellular “nucleic acid parasites”
Viruses can’t make energy or proteins without the host cell
Virus genomes can be DNA or RNA but NOT both
Viruses can have a capsid or capsid + envelope
Viral components are assembled and don’t replicate by division
How are viruses classified or named? (6)
1) Structure: size, morphology, and nucleic acid
2) Biochemical characteristics:
3) Disease
4) Means of transmission
5) Host cell (host range)
6) Tissue or organ (tropism)
Mode of transmission for virus?
Enteric
Respiratory
Zoonotic
Sexually Transmitted
Enteric mechanism & examples
Fecal-Oral Route
Wide-spectrum of activity
Enteroviruses (polio, coxsackie B); rotaviruses (diarrhea)
Respiratory mechanism & examples
Respiratory or salivary route
Influenza, measles, rhinovirus (colds)
Zoontoic mechanism & examples
vector (usually an insect); animal to human directly
rabies, cowpox, dengue
Sexually Transmitted mechanism & examples
sexual contact
herpes simplex virus-2, HIV
Structure of Naked Viruses & 2 examples
Capsid ( made up of capsomers/protein coat) + Nucleic acid
Examples = Adeno & Papilloma
Structure of Enveloped Viruses & 2 examples
Naked virus (Capsid +Nucleic Acid) + Envelope (lipid bilayer) Examples = Pox & Herpes
Naked Viruses are released by the cell via______ and are stable to….. (5)
(lysis) Temperature Acid Proteases Detergents Drying
Enveloped Viruses are released by the cell via ______ and _______and are unstable to….(4)
(lysis & budding) Acid Detergents Drying Heat
Naked Viruses Consequences (5)
Can be spread easily (on fomites, from hand to hand, by dust, by small droplets)
Can dry out and retain infectivity
Can survive the adverse conditions of the gut
Can be resistant to detergents and poor sewage treatment
Antibody may be sufficient for immunoprotection
Enveloped Viruses Consequences (6)
Must stay wet
Cannot survive the gastrointestinal tract
Spreads in large droplets, secretions, organ transplants, and blood transfusions
Does not need to kill the cell to spread
May need antibody and cell-mediated immune response for protection and control
Elicits hypersensitivity and inflammation to cause immunopathogenesis
DNA viruses & examples
Enveloped:Pox (smallpox), Herpes(HSV1), & Hepadna (Hep B)
Naked: Polyoma (JC Virus), Papilloma (HPV), Adeno (adenovirus)
RNA virus & examples (7)
Paramyxovirida (measles) Orthomyxovirida (influenza) Coronaviridae (SARS) Rhabdoviridae (Rabies) Filoviridae (Ebola) Bunyaviridae (Hantavirus) Retroviridae (HIV)
Mode of infection of Viruses? (8)
Recognition of the target cell Attachment Penetration Uncoating Macromolecular (Gene Expression) synthesis Assembly of virus Budding of enveloped viruses Release of virus
Where do RNA viruses grow in the cell ,where do DNA viruses grow?
DNA: nucleus
RNA: cytoplasm
*Where does the flu virus grow?
nucleus
*Where does the pox virus grow?
cytoplasm
Viral acute vs. Chronic vs. Persistent vs. Latent diseases. Give 2 examples for each.
- Acute: rapid onset of disease, brief period of symptoms, & resolution within days (influenza & rhinovirus)
- Chronic: a type of persistent infection that is eventually cleared, cells are not killed OR the cells are killed so slowly that there is no net cell death (Hep B & Hep C)
- Persistent: last for long periods, occurs when the primary infection is not cleared by the adaptive immune response (measles & HIV-1).
- Latent: a type of persistent infection, last through the life of the host, acute infection followed by period of no/little virus production, it is usually re-activated (Varicella-zoster & HSV-1 & 2)
Innate Immunity
Innate
§ Fast but non-specific; fast way to suppress infections & prevent disease
§ No memory
§ Resistance not improved by repeated contact
§ Phagocytes & NK cells
§ Soluble factors = lysozyme, complement, & acute phase proteins
Adaptive Immunity
Adaptive
§ Antigen-specific immune response
§ Produces recovery & a specific immunological memory
§ Specific memory
§ Resistance improved by repeated contact
§ B& T lymphocytes
§ Soluble factors = antibodies
Penetration of Viruses (Naked vs Enveloped)
o Naked
§ Endocytosis (enter by receptor-mediated endocytosis)
§ Viropexis (slip through; direct penetration; picornavirus & papovavirus). Hydrophobic structures of capsid proteins are exposed after virus binds to cells. This allows the virus and its genome to slip through the membrane.
o Enveloped
§ Fuse their membrane with cellular membrane
§ Endocytosis
Uncoating of Viruses (Naked vs. Enveloped)
§ Initiated by attachment to receptor or by acidic environment or proteases in an endosome or lysosome
§ DNA genome taken to nucleus while RNA genome stays in cytoplasm
o Naked
§ Nucleocapsid delivered to the site of replication & the capsid is removed
o Enveloped
§ Uncoating occurs during fusion.
Macromolecular Synthesis of Viruses
§ Early mRNA & nonstructural protein synthesis
§ Genome Replication
§ Late mRNA & structural protein synthesis
§ Post-translational modification of protein
Define First– line defense (3 Types)
Defense against entry into the body
Physical Barriers – skin, sweat
Antimicrobial substances – lysozymes (tears, saliva), lactoferrin (saliva), mucus (respiratory and geneital tract)
Normal Flora – normal flora crowds the intestines making it harder for pathogens to attach, if the pathogen cannot attach, it cannot infect the cell.
Humoral Adaptive Immunity
Involves B Cells
§ Antibody- Mediated Response
§ Involved B cells that recognize pathogens (antigens) in the lymph
§ Antigen binds to B cell
§ Helper T cell co stimulates B cell
§ B cells proliferate & make plasma cells. Plasma cells release antibodies specific to the antigen
§ B cells produce memory cells
Cell Mediated Adaptive Immunity
Involves T cells
§ This response occurs when cells display MHC markers
§ APC displaying foreign antigens bind to T cells
§ Interleukins costimulates T cell activation
§ If MHC-I & endogenous antigens are displayed, T cells proliferate producing cytotoxic T cells. CYT T cells destroy cells that present antigens
§ If MHC-II & exogenous antigens are displayed, T cells proliferate producing helper T cells. HTC release interleukins that stimulate B cells to make antibodies that bind to antigens & stimulate NK and macrophages to destroy the antigen.
List five mechanical and five chemical factors that are involved in preventing the attachment and invasion of microorganisms through the skin and mucous membranes
Mechanical – peeing, bowel movement, skin, removal of inhaled particles, cilia
Chemical – lysozymes, lactoferrin, lactoperoxidase, B-lysin, properdin
Which of the following is not a granulocyte?
a. eosinophil b. macrophage c. basophil d. neutrophil
Macrophages
All blood cells originate from the
a. erythrocyte. b. leukocytic stem cell. c. eosinophilic stem cell. d. hematopoietic stem cell.
hematopoietic stem cell
The leukocyte that contains histamine is the
a. lymphocyte. b. monocyte. c. macrophage. d. basophil.
Basophils
The defense system utilizing highly specialized cells and chemicals that develop in response to specific organisms and foreign materials is the
a. generalized defense system. b. innate immune system. c. adaptive immune system. d. autoimmunity.
adaptive immune system
Allergic reactions mainly involve
a. macrophages. b. monocytes. c. neutrophils. d. mast cells.
Mast cells
Which of the following are referred to as mononuclear phagocytes?
a. lymphocytes and basophils b. mast cells and eosinophils c. basophils and eosinophils d. monocytes and macrophages
monocytes and macrophages
Macrophages form giant cells and granulomas in response to
a. leprosy. b. tuberculosis. c. cholera. d. AIDS.
Tuberculosis
Which of the following are antigen-presenting cells?
a. dendritic cells b. T cells c. erythrocytes d. basophils
Dendritic cells
The leukocyte responsible for adaptive immunity is the
a. lymphocyte. b. monocyte. c. eosinophil. d. neutrophil.
lymphocyte
Skin and mucous membranes
a. are the first line of innate immunity. b. are the first line of adaptive immunity. c. act as physical barriers to infection. d. contain antimicrobial secretions. e. a, c and d
act as physical barriers to infection
are the first line of innate immunity
contain antimicrobial secretions
Interferons, complement, lysozyme, and lactoferrin are all examples of
a. specific antimicrobial factors. b. immune enzymes. c. nonspecific antimicrobial factors. d. cytokines.
nonspecific antimicrobial factors
A group of interacting serum proteins that provide a nonspecific defense mechanism is
a. complement. b. interferon. c. glycoprotein. d. lysozyme
complement
C3a and C5a are involved in
a. inflammation. b. interferon production. c. properidin activation. d. enhancement of phagocytosis. e. a and d
inflammation & enhancement of phagocytosis
C3b is involved in
a. opsonization. b. interferon production. c. properidin activation. d. endotoxin production
opsonization
The complex resulting from complement activity that leads to cell lysis is the
a. prostaglandin complex. b. leukotriene activating complex. c. membrane attack complex. d. histamine complex.
membrane attack complex
Which of the following are most susceptible to complement lysis?
a. Gram-positive bacteria b. Gram-negative bacteria c. bacteriophages c. prions
Gram negative bacteria
The low molecular weight glycoprotein produced by animal cells in response to viral infections is a. complement. b. lysozyme. c. histamine d. interferon.
interferon
The cytokine produced by animal cells in response to viral infections is
a. complement. b. lysozyme. c. histamine. d. interferon.
interferon
Interferons function to make cells
a. resistant to viral replication. b. lyse when exposed to virus. c. non-motile when infected with virus. d. resistant to phagocytosis.
resistant to viral replication
Which of the following cytokines is most antiviral in its action?
a. interleukin-1 b. interleukin-2 c. interferon d. lysozyme
interferon
Which of the following statements about interferon is incorrect?
a. It only works on a few specific types of virus. b. It makes cells resistant to viral infection. c. It is a species specific molecule. d. It does not directly inactivate viruses.
It only works on a few specific types of virus
Which activity of the virally-invaded cell triggers production of interferon?
a. activation of rRNA b. movement of nuclear proteins to the cytoplasm c. production of glycolipids d. production of dsRNA
production of dsRNA
The four cardinal signs of inflammation are:
a. flare, wheals, fever, cough b. rash, pus, heat, rubor c. heat, pain, vesicles, fever d. redness, heat, swelling, pain
redness, heat, swelling, pain
The first host response to a nonspecific tissue injury is described as
a. inflammation. b. reaction. c. antibodies. d. trauma.
inflammation
The first kind of leukocyte lured to the site of inflammation is the
a. neutrophil. b. monocyte. c. macrophage. d. basophil.
neutrophil
The attraction of leukocytes to the area on inflammation is referred to as
a. parasitism. b. infection. c. phototaxis. d. chemotaxis.
chemotaxis
The cellular organelle responsible for the digestion of ingested infectious agents is the
a. endoplasmic reticulum. b. Golgi apparatus. c. phagolysosome. d. lysosome.
phagolysosome
Following digestion of a microorganism by phagocytes, the debris is excreted by
a. ingestion. b. exocytosis. c. extrusion. d. budding.
exocytosis
One of the strongest indications of infectious disease is
a. a rash. b. nausea c. headache. d. fever
fever
Pyrogens are
a. fever-inducing substances. b. fever-inhibiting substances. c. phagocytosis-enhancing substances. d. complement activators.
fever-inducing substances