Term
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Definition
-small infectious agents
-can infect most living things
-bacteriophages attack bacteria
-reproduce at high rate (require host)
-can mutate
-acellular (no cytoplasm or organelles)
-no metabolism of their own
-replicate using hosts machinery
-possess DNA or RNA never both |
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Term
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Definition
-in 1892 shows that the tobacco mosaic disease is caused by an agent
that passes through a porcelain filter |
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Term
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Definition
-Single or segmented, circular or linear molecule of nucleic acid functioning as
the genetic material of the virus
-Can be single-stranded or double-stranded DNA or RNA (but never both)
-Codes for the synthesis of viral components and viral enzymes for replication |
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Term
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Definition
-Protein shell surrounding the genome
-Usually composed of protein subunits called capsomeres
-Protect and introduce the genome into host cells. |
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Term
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Definition
-Composed of phospholipids and glycoprotein
-Derived from host cell membranes by a process called budding
-Depending on the virus, envelopes may be covered by spikes made of
carbohydrates-protein complexes that helps the virus to attach to the
host cell |
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Term
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Definition
-Nucleic acid surrounded by either a
helical or polyhedral core and covered by an envelope (herpes) |
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Term
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Definition
Pleomorphic (irregular shape), or
have complex structures |
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Term
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Definition
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Term
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Definition
nucleic acid surrounded by a hollow
protein cylinder or capsid and possessing a helical
structure (tobacco mosaic) |
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Term
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Definition
nucleic acid surrounded by a
polyhedral (many-sided) shell or capsid, usually in the
form of an icosahedron (Mastadenovirus) |
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Term
| classification of viruses |
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Definition
-type of nucleic acid
-shape of capsid
-enveloped or naked |
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Term
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Definition
-the (-) DNA is directly transcribed into viral mRNA
-bacteriophages, papovaviruses, adenoviruses, herpesviruses |
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Term
| viruses with (+) DNA or (-) DNA |
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Definition
-once inside the host, it is converted into ds DNA and the (-) strand is transcribed into viral mRNA
-Phage M13, Parvoviruses |
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Term
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Definition
-a (+) RNA is copied into (-) RNA that is transcribed into viral mRNA
-Picorna viruses, Togaviruses, Corona viruses |
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Term
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Definition
-the (-) RNA is copied into (+) RNA which functions as viral mRNA
-Orthomysoviruses, Paramysoviruses, Rhabdoviruses |
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Term
| viruses with ds RNA (+/-) |
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Definition
-the (+) RNA functions as viral mRNA
-Reoviruses |
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Term
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Definition
-the (+) RNA is reverse transcribed into (-)DNA that makes a complementary copy to become (+/-) DNA
-the DNA is transcribed to make viral mRNA
-Retroviruses |
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Term
| viral replication of bacteriophages |
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Definition
| -lysogenic and lytic cycle |
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Term
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Definition
-attachment
-penetration
-biosynthesis
-maturation
-release |
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Term
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Definition
-by chance, no energy required
-involves attachment site on virus and receptor site on bacteria |
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Term
| penetration (lytic cycle) |
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Definition
-phage lysozyme is released and breaks down a portion of the cell wall
-phage injects DNA |
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Term
| biosynthesis (lytic cycle) |
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Definition
-synthesis of viral nucleic acids and proteins in cytoplasm
-host DNA is degraded
-viral proteins interfere with transcription and it ceases
-translation is repressed
-early phase-many copies of the phage DNA are synthesized using the host's nucleotides and enzymes
-late phase-host's ribosomes, enzymes, and amino acids are used for translation of viral proteins
-during this eclipse period, the virus is not infectious |
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Term
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Definition
-assembly of capsid around genome
-complete virions are produced |
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Term
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Definition
-plasma membrane lyses to to action of phage lysozyme
-virions released to infect other bacteria |
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Term
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Definition
-does not necessarily end with host cell death
-these phages are able to incorporate their DNA into the host cell DNA
-virus remains latent(inactive) |
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Term
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Definition
-lysogenic cells are immune to re-infection of the same phage
-phage conversion (cell exhibits new properties)
-specialized transduction |
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Term
| example of phage conversion |
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Definition
-Corynebacterium diphteriae
-diphteriae caused by toxin
-gene encoding toxin is carried by a phage
-so it only produces toxin when it carries the lysogenic phage
-similar with Clostridrium botulinum |
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Term
| Animal virus infection steps (6) |
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Definition
-attachment
-penetration
-uncoating
-biosynthesis
-maturation
-release and reinfection |
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Term
| attachment (animal virus) |
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Definition
| -binding of attachment sites on viral surface with receptor sites on host cell membrane |
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Term
| penetration (animal virus) |
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Definition
-fusion with the host membrane
-endocytosis |
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Term
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Definition
-capsid is digested
-release of viral genome |
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Term
| biosynthesis (animal virus) |
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Definition
-viral genome directs the host cell's metabolic to synthesize viral enzymes and viral parts
-early phage- viral genome replicates thousands of times
-late phase-viral structural proteins and enzymes involved in maturation are produced
-during uncoating and replication, virus is not infectious |
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Term
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Definition
-capsid and matrix proteins
-envelope glycoproteins |
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Term
| maturation (animal phase) |
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Definition
| assembly of capsid around genome |
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Term
| release and reinfection (animal virus) |
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Definition
| -virus obtains envelope by budding |
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Term
| number of viruses that can be made from one host cell |
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Definition
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Term
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Definition
-some ds DNA viruses like herpes virus and retrovirus are able to remain latent for long periods of time without replicating or causing harm
-some remain latent in cytoplasm
-others are able to integrate their DNA into host cell chromosomes(provirus)
-results from the lack of production of specific host cell proteins that are required for activation of viral genes
-activation of host cellls DNA in response to extracellular stimuli can lead to synthesis of specific host cell proteins required by virus
-these proteins now activate viral genes leading to burst of replication via the productive life cycle |
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Term
| examples of latent viruses |
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Definition
-herpes simplex virus (HSV) (oral, genital)
-Epstein-Barr virus (EBV)-replicate in epithelial cells, latent in B lymphocytes, mononucleosis |
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Term
| persistent (chronic) viral infections |
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Definition
-occur gradually over a long period rather than appearing suddenly
-cervial cancer (HPV), AIDS-HIV-1, liver cancer HBV |
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Term
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Definition
-large genome 120kb, linear, ds
-among most widespread of all infections
-can establish latent infections which can reactivate years later producing acute infections
-100 herpesviruses identified from oysters to humans
-8 infect humans |
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Term
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Definition
-disease is initiated by direct contact (oral genital brain)
-cause cytopathologic effects (degenerative changes in cells)
-avoids antibodes by cell to cell spread
-establishes latency in neurons (hides from immune system)
-activated from latency by heat, cold, UV, stress, or immune suppression |
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Term
| Herpes Simplex Virus (HSV) |
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Definition
-common human pathogen
-cause painful by benign lesions and recurrent disease
-both type 1 and type 2 cause cause significant mortality when infecting eye or brain, in immunosupressed person, or newborn |
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Term
| Varicella Zoster virus (VZV) |
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Definition
-causes chicken pox (varicella)
-when reactivated causes herpes zoster or shingles (rash along entire skin)
-establish latent infections of neurons
-characteristic blister-like lesions
-spread predominantly by respiratory route
-smallest genome of herpesvirus |
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Term
| Hepatitis A virus (Acute Viral Hepatitis A) |
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Definition
-common in US
-30% of population show evidence of past infection due to anti-HAV antibodies
-most infections are asympotomatic-confers lifelong immunity
-long incubation period (15-50 days) before symptoms |
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Term
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Definition
-during incubation period, virus replicates in intestinal cells and shed in high concentrations in stools
-transmitted via fecal-oral route (water, food, dirty hands)
-outbreaks usually originate from common source (water supplies, restaurant, daycare) |
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Term
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Definition
-one of the most frequently reported vaccine preventable diseases in US
-HBV causes acute and chronic hepatitis
-spread though sexual contact, blood transfusion, exposure to blood via open cuts, opens spores, needle/razor sharing, ear piercing |
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Term
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Definition
-can be spread from mother to child from birth
-incubation period 4-25 weeks
-90% are considered acute
-10% chronic may progress to cirrhosis, liver failure or liver cancer |
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Term
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Definition
-33 people worldwide living with HIV/AIDS
-14 million AIDS deaths since beginning of epidemic
-close to 1 million US AIDS cases
-caused by HIV-1 or HIV-2 |
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Term
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Definition
-enveloped RNA
-2 copies of (+) RNA genome
-9 viral genes
-encodes viral proteins (gp41, gp120)
that mediate infection of target cells |
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Term
| human cells possessing CD4 |
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Definition
-T4 helper lymphocytes
-monocytes
-macrophages
-dendritic cells |
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Term
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Definition
-results in progressive immune deterioration due to decreased number and function of CD4+ T lymphocytes (helper T-cells)
-initial infection of dendritic cells or other macrophages in epithelium
-moves to lymphoid regions where replication reaches critical levels
-macrophages are persistently infected creating a major reservoir and means of distribution |
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Term
| more on HIV disease mechanism |
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Definition
-CD8 T cells can kill infected cells but CD8 T cells require activation of CD4 T cells
-as CD4 decreases, CD8 decreases
-reduction of CD8 correlates to disease progression to AIDS |
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Term
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Definition
-very common infection
-20 million people infected
-at least 50% of sexually active people acquire genital HPV at some pt in their lives
-by age 50, 80% of women will have acquired genital HPV infection
-6.2 million get a new genital HPV each year |
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Term
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Definition
-more than 100 different types
-some cause benign skin warts or papillomas
-common warts are spread environmentally or skin to skin contact
-seperate group of 30 HPVs are through sexual contact |
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Term
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Definition
-about a dozen can cause cancers (most mostly cervical cancer)
-HPV induced cancers often have viral sequences integrated into the cellular DNA
-some of the HPV "early" genes (E6 and E7) are known to act as oncogenes that tumor growth and malignant transformation |
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Term
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Definition
-modified gene or set of nucleotides that code for a protein that increases the malignancy of a tumor cell
-some usually involved in early stages of cancer increase chance that a normal cell develops into a tumor cell possibly resulting in cancer |
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Term
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Definition
-growing virus in living animals
-growing virus in embryonic egg
-growing virus in cell culture
-growing bacteriophages |
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Term
| growing viruses in living animals |
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Definition
-used to be the only way
-not extensively used anymore except for growth of viruses that develop in an animal
-ex. Coxsackievirus A-painful blisters in mouth, thoat, hands, feet, conjunctivitis (eyelid swelling) |
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Term
| growing virus in embryonic egg |
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Definition
| -viral growth is indicated by damage/death of embryo or lesions on egg membrane |
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Term
| growing virus in cell culture |
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Definition
-a tissue is treated with enzymes to separate the cells
-cells are suspended in culture medium
-normal cells or primary cells grow in a monolayer across glass or plastic container. Transformed or continuous cells do not grow in the monoculture |
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Term
| growing bacteriophages (plaque method) |
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Definition
-a sample of bacteriophage is mixed with host bacteria and melted agar
-mixture is poured into a petri plate containing a layer of agar growth medium
-each virus infects a bacterium, multiply, and release hundreds of new viruses that will infect other bacteria
-destruction of bacteria produces a clearing or a plaqueviro |
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Term
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Definition
-small circular single stranded molecules of infectious RNA lacking a protein coat
-cause of few plant diseases
-viroid RNA does not code for any protein
-usually transmitted by seed or pollen
-infected plants can show distorted growth
-ex. Potato spindle tuber disease-all tomatoes and potatoes are susceptible and there is no natural resistance |
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Term
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Definition
-only known disease to be caused by viroid
-delta agent is a viroid enclosed in a Hep B virus capsid
-there is extensive sequence complementarity between Hep D viroid RNA and human liver cell 7S RNA, a small cytoplasmic RNA
-causes liver death by sequestering 7S RNA of cleaving it
-can only enter human cell if enclosed in a capsid that contains a binding protein (it obtains this from Hep B virus)
-the delta agent that enters blood can be transmitted via blood or serum transfusions |
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Term
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Definition
-small proteinaceous particles
-controversy if it contains nucelic acid (if so, it has very little, not enough to code for protein)
-infect and propagate by refolding into a structure which is able to convert normal protein into abnormally structured protein
-cause neurodegenerative disease by aggregating in CNS to form plaques called amyloids which disrupt normal tissue structure
-this disruption is characterized by holes with spongy architecture due to loss of neurons |
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Term
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Definition
-the proteins that prions are made of
-found throughout body
-prion protein found in infectious material has a different structure and is resistant to proteases |
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Term
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Definition
| -normal protein found on membrane of cells |
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Term
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Definition
-infectious isoform of Prp^c
-able to catalyze formation of other normal proteins into infectious ones by changing conformation |
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Term
| Prp^Sc mechanism of infection |
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Definition
-prp is produced by cells
-prpSc acquired or produced by altered gene
-prpSc reacts with prp on cell surface and converts it to prpSc
-new prpSc converts more prp
-prpSc is takin in cell by endocytosis
-prpSc accululates in endosomes
-prpSc continues to accumulate as it is transfered to lysozomes
-results in cell death |
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Term
| Bovine spongiform encephalopathy (mad cow disease) |
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Definition
-fatal neurodegenerative disease
-transmissions occurs when healthy animals come in contact with infected tissues
-was widespread in Europe in 1987 due to meat and bone meal and animal cadavers used as cattle feed
-can be transferred to human beings who eat or inhale material from infected carcasses (Creutzfeldt-Jakob
disease)(nvCJD or vCJD)
-first symptoms of CJD is rapidly progressive dementia, memory loss, personality changes, hallucinations,
speech impairment, jerky movements, balance and coordination dysfunction (ataxia), rigid posture, seizures |
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Term
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Definition
-laughing sickness
-first noted in New Guinea in 1900s
-by 1950s anthropologists reported that kuru (trembling with fear) was rampant throughout South Fore
-due to ritual acts of mortuary cannibalism |
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Term
| symptoms of kuru first stage |
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Definition
| -ambulant stage-unsteadiness of stance, voice, hands, eyes, deterioration of speech, tremor, shivering, loss of coordination in lower extremities that moves slightly upwards, slurring speech |
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Term
| symptoms of kuru second stage |
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Definition
-sedentary stage
-no longer walk without support, more severe tremors and ataxia, shock-like muscle jerks, outbursts of laughter, depression, mental slowing |
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Term
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Definition
-terminal stage
-inability too sit up without support, severe ataxia, tremor and slurring of speech, urinary and fecal incontinence, difficulty swallowing, deep ulcerations |
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