-
Virus
Non-cellular entities which consist mainly of protein and nucleic acid (DNA or RNA) and which can replicate only after entry into specific living cells
-
Host range
The spectrum of host cells that each type of virus can infect. it is determined by specific host attachment sites and cellular factors
-
Virion
a complete viral particle
-
Phage
virus that infects a bacterial cell
-
General Characteristics of Viruses
- Obligatory intracellular parasites
- Contain DNA or RNA
- No ribosomes
- No ATP-generating mechanism
- Contain a protein coat
- No metabolism and, few or no enzymes of their own.
- No intrinsic motility.
- Cannot grow on artificial lab media.
- Do not respond to physical stimuli in their environment
- Some viruses are enclosed by an envelope
- Some viruses have spikes
- Most viruses infect only specific types of cells in one host
-
General Structural Properties of Viruses
- Polyhedral (many sided) Viruses
- Helical Viruses
- Enveloped Viruses
- Complex Viruses
- Bacterial viruses
-
Polyhedral (many sided) Viruses
Many animal, plant, and bacterial viruses are icosahedron (with 20 faces and 12 corners).
-
Helical Viruses
Resemble long rods that may be rigid or flexible.
-
Enveloped Viruses
Have a roughly spherical but somewhat variable shape even though their nucleocapsid can either be icosahedral or helical
-
Complex Viruses
Many bacterial viruses have capsid symmetry that is neither purely icosahedral nor helical. They may possess tails and other structures or have complex, multilayered walls surrounding the nucleic acid
-
Virion Structure
- Virion is an infectious viral particle
- Nucleic acid
- DNA or RNA Never both
- Circular or linear DNA
- Or single or double stranded RNA
- Capsid
- Capsomeres
- Envelope
- Spikes
-
DNA viruses
- Papillomavirus
- Adenovirus
-
RNA Viruses
- Influenza virus
- Paramyxoviruses -Mumps
-
Capsid
(nucleocapsid) is composed of protein subunits called Capsomeres
-
envelope
consists of combination of lipids, proteins, and CHO, an outer membranous layer surrounding the nucleoapsid
-
naked virus or nonenveoped virus
virus without envelope
-
Capsomeres
protein subunits that make capsids
-
Spikes
A receptor on the surface of certain enveloped viruses that facilitates specific attachment to the host cellAre CHO and protein complex Can be used as means of identification.Cause clumping of RBC called Hemagglutination
-
Plaques
a visible structure formed within a cell culture, such as bacterial cultures within some nutrient medium (e.g. agar). The bacteriophage viruses replicate and spread, thus generating regions of cell destructions
-
Oncogenes
A gene that when activated can transform normal cells into cancerous cells
-
Agents that can activate oncogenes
- high-energy radiation
- mutagenic chemicals
- some viruses
-
Protooncogenes
Normal cellular genes that regulate cell proliferation and differentiation that can become oncogenes.
-
Growing Viruses
Viruses must be grown in living cellsBacteriophages form plaques on a lawn of bacteriaAnimal viruses may be grown in living animals or in embryonated eggs or in cell cultures (continuous cell lines)
-
multiplication of viruses
- lytic cycle
- lysogenic cycle
-
Lytic cycle
lysis and death of host cell
-
Lysogenic cycle
- Host cell does not die
- Viral DNA incorporates into host cell DNA
- Virus remains latent
-
steps of lytic cycle (lysogenic cycle)
- Attachment
- Penetration
- Biosynthesis -production of phage or viral DNA and proteins
- Maturation - DNA and capsids are assempled
- Release - plasma membrane breaks open releasing virions
-
Release of Bacteriophages
- Eclipse period
- Burst size
- Burst time
-
Virus species
- Adenovirus
- Papillomavirus
- Paramyxoviruses
- Influenza virus
- Bacteriophages
- herpesvirus
-
Prions
tiny pieces of protein (infecious protein)
-
Disease by prions are caused by
Inherited and transmissible by ingestion, transplant, and surgical instruments
-
Diseases caused by prions
- Spongiform encephalopathies: sheep scrapie
- Creutzfeldt-Jakob disease
- Gerstmann-Sträussler-Scheinker syndrome
- Fatal familial insomnia
- Mad cow disease
- - there is no treatment
-
Susceptibility
lack of resistance to disease
-
Immunity
ability to ward off disease
-
Innate
nonspecific or any pathogen
-
Adaptive
specific pathogen & long lasting
-
Innate Physical Factors
epidermis, keratin, mucous membranes, ciliary escalator
-
Chemical Factors
fungistatic sebum-oily skin, low pH, lysozyme, gastric juice, vaginal secretions
-
antagonism
compete with pathogens
-
commensal
one microbe benefits and the other is unharmed
-
Neutrophils Macrophages
phagocytosis
-
Basophiles
Histamine, triggers inflammation
-
Eosinophils
kill parasites
-
-
-
natural killer cells
targeted, cancerous tissue
-
T-cells
cell mediated immunity, supress or amplify
-
-
-
lymphatic
source of T cell creation
-
-
acute phase proteins
complement, kinins
-
vasodilation
prostaglandins
-
phagocyte migration
inflammatory response allows phagocytic wbc's to leave vessels and attack pathogens
-
Complement system
serum proteins, antigen antibody reaction, C3b opsonization
-
opsonization
makes the antigen more susceptible to phagocytosis
-
cytolsis
bursting of cells
-
-
Evade Complement
capsules, surface lipid carbs, enzymatic digestion
-
Interferons (IFNs)
IFN-a and IGN-B, antiviral proteins
-
Gamma IFN
phagocytize bacteria
-
Physical Factors
lacrimal, saliva, urine, vaginal secretions
-
-
saliva
washes microbes off
-
Epidermis
consist of tightly packed cells with keratin
-
keratin
a protective main component in hair
-
-
Ciliary escalator
microbes trapped in mucus are transported away from the lungs
-
Lysozyme
in perspiration and urine
-
Adaptive Immunity
acquired naturally or artificially specific and have memory
-
Natural Adaptive Immunity
an organism or toxin enters the body and produces an immune response
-
Artificial Adaptive Immunity
results from immunization by a vaccine
-
Specific Component
protects against one pathogenonly exception when two are closely related
-
Memory Component
much stronger immune response upon reexposurelong term immunity
-
Two AI Responses
- Antibody mediated responses
- Cell Mediated Response
-
Antibody Mediated Response
- AKA: Humoral Response
- Ab specifically bind to and inactivate foreign particles
-
Cell Mediated Response
trigger T lymphocytesrecognize and destroy abnormal/infected host cells
-
antigen
foreign particle that enters the bodycan be broken into epitopes
-
antibodies
- Protein produced in response to Ag
- like lock and key
- 2 light chains and 2 heavy chains
- 2 antigen bonding sites
-
-
IgG
- most common
- found in blood and can enter tissues
- can cross the placenta: confers passive immunity to fetus
- binds antigens very strongly
-
IgM
- pentamer
- stay in blood
- aggregate antigens
- 1st produced
-
IgA
- dimer
- found in body secretions
- protects gastrointestinal tract of newborns
-
IgE
- found on mast cells and basophils
- triggers release of histamine
-
Antibody involved in allergies
Immunoglobulin E
-
Functions of Antibodies
- Agglutination
- Neutralization Complement
- Activation
- Opsonization
- Ab Dependent Cytotoxicity
-
Agglutination
Ag stuck togetherreduces number of infectious units to be dealt with
-
Neutralization
Ab binds to Ag and inactivates itprevents it from adsorbing to host cells
-
Complement Activation
Ab binds bacteria and starts complement pathway(MAC Attack)
-
Opsonization
flags down phagocytes to destroy cell
-
Ab Dependent Cytotoxicity
flags down immune system cells to destroy antigens too big for phagocytosis
-
Types of Lymphocytes
- B- Lymphocytes
- T-Lymphocytes
-
B-Lymphocytes
- Ab producing cells
- involved in humoral response
-
T-Lymphocytes
- Helper T-cells
- Cytotoxic T-cells-destroy abnormal body cells
- cell mediated response
-
Antigen Presenting Cells
macrophages, B cells, dendritic cells
-
Major Histocompatibilty Complex
antigens presented to MHC to decide if they are dangerous or not
-
Clonal Selection
- B cells circulate until they find antigenspresent to MHC
- MHC says its dangerous
- Th cells activate B cells- which undergo clonal expansion
-
Clonal Expansion
- B cell differentiates into plasma cells(Ab cells) and memory cells
- memory cell are long living and if they encounter the antigen again will initiate a quick response
-
Primary Response
- B cells produce low levels of Ab
- 7-14 days
- IgM first, then IgG and IgA
- memory built
-
Secondary Response
- 2nd encounter
- high levels of Ab1-2 days
- memory cells replenished
-
Cytotoxic T Cells
destroy abnormal human cells
-
Dendritic Cells
engulfs foreign antigens and present to a different MHC
-
Active Immunization
- long lasting immunity
- natural- body encounters Ag
- Artificial- Ag as a vaccine
-
Passive Immunization
- temporary immunity
- Natural- mother to infant
- Artificial- Ab injected(for life threatening situations snakebite)
|
|