BIOL124 - L4-5

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  • Created by: Katherine
  • Created on: 02-06-16 11:07
Where do viruses reproduece?
In host cells
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What do viruses consit of?
Genome and capsule
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What do viruses lack?
Metabolic enzymes, ribosomes.
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It is in the interest of the virus not to cause death of host, therefore it needs to have:
Have long latency period/ easy tansmissio.
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What does the influenza virus do?
Infects upper respiratory tract and major central airways.
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When were the flu pandemics?
1918, 1957, 1968 and 2009.
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What are the different classes of flu?
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What is the shape of the influenza virus?
Ovoid/spherical 90-100nm in diameter. It is a single stranded RNA genome virus (ssRNA)
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What does it look like?
The virus has a lipid bilayer, derived from the last cell infected. It has single stranded RNA where the sequence to make new copies are help. It has neuraminidase .and hemagglutinin
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What does the neuraminidase allow us to do?
Denote it
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What are the structural details of influenza?
Haemagluttinin, neuraminidase, nucleocapsid.
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What does Haemagglutinin do?
The virus attaches to the cell using these.
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What do neuraminidase do?
Helps viral budding from the host cell
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What do the nucleocapids do?
Contain 8 different single strands of RNA (ssRNA), protein + polymerase.
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How does binding occur in the virus?
Capsid and genoem enter cell, genome is released. RNA is copied into RNA and more is made. RNA translated into capsid and envelope proteins. Transport of enevelope proteins into plasma membrane. Capsule surrounds genome.
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What leads to new infectious strains?
Alteration of HA and NA antigens - RNA polymerase does not proofread.
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What are the types of immune response against influenz?
Humoral and cell mediated
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What is the humoral response to influenza?
Secreted IgA, IgG, Igm - block binding and fusion of virus to host and allow opsonisation (aids phagocytosis) and complement mediated killling.
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What is the cell mediated response to influenza?
Interferon secreted by T cells has antiviral activity. Cytotoxic T cells and Nk cells kill vurus infected cells.
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What are the effects of the disease?
Fever, cough and sore throat but most people recover within 1-2 weeks. Evasion = the disease can occur in epidemics or pandemics.
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Pandemics are caused by...
Antigenic shifts. The majority of the public are not immune to new strains and a pandemic resutls.
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What is antigenic shift?
Sudden emergence of new antigenic subtype - Influence A only - HA and/or NA are very altered. It is caused when two different strains infect the same cell. RNA is exposed and mixes up.
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What is antigenic drift?
Caused by minor changes in protein structure. Results in epidemics. It is caused by lack of viral RNA polymerase proofreading point mutations. Occurs in influenza A,B and C.
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What is the treatment for influenza?
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How many people have died from AIDS related causes
39 million
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When did AIDs emerge?
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What are the symptoms of AIDs?
Pneumonia, Kaposi's sarcoma, reduced levels of CD4 (fewer than 200cd4)+ helper T cells.
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How is AIDS transmitted?
Through bodily fluids
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What is a retrovirus?
Any of a group of RNA viruses which insert a copy of their genome into the host cell in order to replicate. It has a lipid bilayer, it is derived from the last cell that the HIV infected. The genome is made of 2 single stranded RNA. The gp120 togethe
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What does HIV infect?
Cells that are CD4+, especially helper T cells and MCHII APC, but also macrophages. The entry of the virus requires CD4 which binds to gp120 on the virus. but also a coreceptor (CXCR4) which binds to gp41 on the surface of the HIV virus.
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What does the binding of CXCR4 and gp41 do?
Mediates fusion of the virus with the target cell. Some people are resistant to HIV 1 becuase they have a defective co-receptor which prevents HIV infection of the cell.
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What happens to HIV once it is inside the cell?
It is reverse transcribed, and the DNA is integrated into the host genome. In this provirus form (hidden from the immune system), the viral genome directs the production of new virus particles. Not eradicated by body.
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What is the Immune response to HIV?
After initial peak, virus levels in the blood fall as anti-HIV antibodies, produced 1-12 months after infection, rise, HIV continues to replicated in lymphatic tissue.
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What is seroconversion?
It is the time at which HIV antibodies devlop and become detectable.
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What happens after the initial drop in HIV levels in the the blood?
The virus ontinues to be produced by cells in the lymph nodes, causing structural and functional damage. In time, the concentraiton of HIV in the blood icnreases as a result of the breakdown of lymphatic tissue function.
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What does the breakdown of lymphatic tissue function and release of virus from these tissue result in?
Extensive loss of humoral and cell mediated immunity. The time required for an HIV infection to progress to severe helper T cell depeltion and AIDS varies greatly, but it currently averages about 10 years.
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Can HIV be cured?
No, and AIDS cannot be prevented. New, expensive drug therapies can slow this progession by inhibiting reverse transcriptase (rescriptor), by inhibiting proviral cDNA formation (AZT) and protease (Indinavir/crixidan).
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HIV treatment?
Combinations of Indinar/Crixidan can help helper T cell numbers to rise. Other drugs may treat the opportunistic diseases as the develop.
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What is the acute phase of HIV?
Initially high levels of virus in the blood. There is a drop in CD4+ t cell numbers, activation of vigorous immune response. Antibodies to virus are generated (1-12 post infection) Tc cells against virus generated.
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What is the chronic phase?
Virus continues to be made in lymph node. HIV load increases. Damage to lymphatic tissues. Depletion of CD4+ T cell numbers leading to extensive loss of humoral and cell mediated immunity.
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What are the stages of untreated HIV infection?
The T cell concentraiton drops with passing years, HIV conc increases, antibody conc decreases.
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Why does the immune system not beat HIV?
High mutation rate, helper T cell population depleted. Breakdown of lymphatic tissue. Provirus hides from immune system.
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Card 2


What do viruses consit of?


Genome and capsule

Card 3


What do viruses lack?


Preview of the front of card 3

Card 4


It is in the interest of the virus not to cause death of host, therefore it needs to have:


Preview of the front of card 4

Card 5


What does the influenza virus do?


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