Tackling Viral Epidemics & Neglected Diseases - Viral Infections & Antiviral Drugs

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  • Created by: LBCW0502
  • Created on: 11-04-21 12:31
What is a virus? (1)
Non-cellular infectious agent which take over a host cell in order to survive and multiply. Make by genomic material, capsid, RNA or DNA, surrounded by membranes, virus is not able to self-replicate (no two daughter viruses).
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What is a virus? (2)
Different types of viruses. DNA, protein coat, tail to infect bacteria. Genomic material, capsid, protein on surface of membrane. Some viruses have filamentous spore
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Viruses are responsible for which diseases?
Flu, rubella, measles, mumps, viral pneumonia, smallpox, yellow fever, AIDS, Hepatitis, poliomyelitis, ebola, dengue and zika fever
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How are viruses transmitted?
Transmitted through the air by an infected host sneezing or coughing. Dengue fever and Zika Fever: viruses transmitted by mosquitoes. Virus transmitted through physical contact (e.g. HIV)
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Describe how viral infections have proven to
affect human populations
Smallpox – Roman Empire, European colonization of South America. Influenza pandemia – Spanish Flu, Hong Kong Flu. HIV/AIDS pandemia (– now have drugs to contain the pandemic but virus is affecting lots of people in the world). Ebola
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Describe the structure of a virus
A protein package transmitting foreign nucleic acids between host cells. Most viruses have the same structure. Genomic material – RNA or DNA. Protein coat - capsid. Phospholipid membrane. Protein to infect cell.
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What are the classifications of viruses?
ssRNA and dsRNS (less common). ssDNA and dsDNA
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Outline the replication of a virus
Virus uses protein, interacts with receptor on host cell (e.g. human cell), link to cell, endocytosis, penetrate inside cell, capsid is broken and destroyed, genomic material is released, goes to nucleus of cell or directly creates proteins using ribosome
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What is a vaccination? (1)
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins
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What is a vaccination? (2)
A biological preparation to improve immunity to a particular disease. Contains an antigen to stimulate immune system of body to respond against that antigen to induce an immune response. Immune body memorises antigen, able to start immune response
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What are the limitations of vaccination?
Rapid gene mutations. Constant changes to the aminoacid composition of glycoproteins present on the viral surface. Vaccine is not effective, immune system cannot recognise virus. Influenza – vaccine developed annually, changing strains
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How do vaccinations help to fight viral infections? (1)
After you have been vaccinated, some of the cells that are responsible for protecting you against disease — your B lymphocytes — detect the antigens in the vaccine. The B lymphocytes will react as if the real infectious organism was invading your body.
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How do vaccinations help to fight viral infections? (2)
The plasma cells produce antibodies (Y- or T-shaped molecules), which are trained specifically to attach to and inactivate the organism you are being vaccinated against. This response from your immune system, generated by the B lymphocytes
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How do vaccinations help to fight viral infections? (3)
Your body continues making antibodies and memory B cells for a couple of weeks after vaccination. Over time, the antibodies will gradually disappear, but the memory B cells will remain dormant in your body for many years.
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How do vaccinations help to fight viral infections? (4)
The memory B cells (as the name implies) keep a memory of the organism that you were vaccinated against. If you are ever exposed to that organism, the dormant memory cells will recognise it straight away, and rapidly start multiplying and developing
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What are the types of vaccines?
Live attenuated vaccines, which contain a living, but weakened, form of the germ (organism). Inactivated vaccines, which contain a killed form of the organism. Subunit vaccines, which contain just the part of the organism that stimulates an immune respons
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Describe features of DNA and RNA vaccines
This vaccine uses DNA or RNA molecules to teach the immune system to target key viral proteins. Easy and quick to design. But never been done before (currently, no licensed DNA or RNA vaccines being used). Moderna is testing an RNA vaccine for COVID-19.
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Describe features of live attenuated vaccines
This is a weakened version of the actual virus. Stimulated a robust immune response without causing serious disease. But might not be safe for those with immunocompromised systems. Examples include MMR and chickenpox vaccines. Codagenix
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Describe features of inactivated vaccines
An inactivated vaccine uses the whole virus after it has been killed with heat or chemicals. Safe because the virus is already dead and is to make. But not as effective as a live virus. Some previous inactivated vaccines have made disease worse.
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Describe features of subunit vaccines
This vaccine uses a piece of a virus' surface to focus the immune system on a single target. Focuses the immune response on the most important part of the virus for protection and cannot cause infection. May not stimulate a strong response.
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Describe features of viral vector vaccines
This approach takes a harmless virus and uses it to deliver viral genes to build immunity. Live viruses tend to elicit stronger immune responses than dead viruses or subunit vaccines. Important to pick a viral vector that is truly safe.
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What is the main advantage of live vaccines?
While the live vaccines can provide lifelong immunity after only one or 2 doses, periodic booster doses are needed to maintain immunity with some of the other types of vaccines.
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Describe features of antiviral drugs (1)
Most viral diseases, with the exception of those caused by human immunodeficiency virus (HIV), are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 4 main groups of viruses
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Describe features of antiviral drugs (2)
Designing safe and effective antiviral drugs is difficult, because viruses use the host's cells to replicate. This makes it difficult to find targets for the drug that would interfere with the virus without also harming the host organism's cells.
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Describe features of antiviral drugs (3)
Need to develop new antiviral drugs. Lots of antibiotics, easy to produce, distinct from other cells. Viral cells – infect host cells. Need to find a drug that only kills the infected cells without killing healthy cells – difficult to identify molecule
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Give examples of DNA viruses
Herpes Simplex virus-1 and -2 (cold sores, genital herpes, mononucleosis, Kaposi’s sarcoma), Varicella-Zoster, Cytomegalovirus. Double-stranded genome, inside phospholipid membrane, glycoprotein to bind to cells to initiate replication.
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Describe features of acyclovir (1)
Zovirax. It was the first non-toxic herpes drug to be used systemically. It is used for the treatment of infections due to both HSV-1 and HSV-2. Acyclovir interferes with DNA synthesis but must first become activated.
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Describe features of acyclovir (2)
Similar structure to guanosine – but sugar group is absent . Replicate DNA, nucleoside are phosphorylated then assembled to growing DNA, release of group. Inject acyclovir – recognised as potential nucleoside, phosphorylated by viral protein
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Describe features of influenza
Spread through air (coughs/sneezes) and touching surfaces/mouth/eyes. Two influenza viruses are epidemic in humans (H1N1 and H3N2). Bird flu is H1N5
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What is antigenic drift?
Mutations in genes leading to changes in HA and NA when the virus replicates
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What is antigenic shift?
Major change in a virus, reuslting in new HA and NA proteins that infect humans
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State drugs used against influenza
Amantadine (M2 ion channel disrupters, inhibit penetration and uncoating of virus). Rimantidine. Zanamivir. Oseltamivir
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What is HIV? (1)
Human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) is a disease spectrum of the human immune system caused by infection with human immunodeficiency virus (HIV).
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What is HIV? (2)
HIV primarily infects components of the human immune system such as CD4+ T cells, macrophages and dendritic cells. It directly and indirectly destroys CD4+ T cells. HIV1/2 (contains 2 identical strands of +ssRNA). Two main proteins are reverse transcripta
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What are the roles of reverse transcriptase and integrase?
Reverse transcriptase is a polymerase (uses RNA strands as template to synthesise new DNA). Integrase incorporates proviral DNA into host cell DNA
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State anti-HIV drugs
Nucleoside RT inhibitors (abacavir, lamivudine, AZT). Non-nucleoside RT inhibitors (nevirapine). Integrase inhibitors (raltegravir). Protease inhibitors (saquinavir). Entry inhibitors (maraviroc). HAART
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What is HCV?
Hepatitis C virus (HCV) is a small plus-strand RNA virus responsible for a significant proportion of acute and chronic hepatitis in humans. +ssRNA
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What is the therapy for HCV?
Ribavirin and interferons. Protease inhibitors. Polymerase inhibitors (sofosbuvir)
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What is the arbovirus?
Viruses maintained in nature through biological transmission between susceptible vertebrate hosts by blood feeding arthropods (mostly mosquitoes)
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What is the flavivirus?
Flavivirus is a genus of viruses in the family Flaviviridae. This genus includes the West Nile virus, dengue virus, Zika virus and several other viruses (i.e. yellow fever virus, Japanes encephalitis virus). The virus is generally transmitted to humans by
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What is dengue?
Dengue fever is a mosquito-borne tropical disease caused by the dengue virus (DENV).
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What is the dengue therapy? (1)
Febrile phase: Bed rest, Paracetamol – 4 times/day, Avoid aspirin & ibuprofen, Avoid antibiotics, Oral rehydratation therapy –
fluid loss due to vomiting/high temperature.
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What is the dengue therapy? (2)
Hemorragic fever and shock syndrome: Supportive measures, Fluid reuscitations - replenishing bodily fluid lost, Blood component therapy – blood transfusion, Oxygen therapy, Others: epinephrine, dopamine, dobutamine
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What is the dengue therapy? (3)
Ribavirin and celgosivir
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What is the zika virus?
Zika virus (ZIKV), like other flaviviruses, is a positive-sense RNA genome can be directly translated into viral proteins.
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What is the treatment for ebola?
IV fluids, oxygen, BP, lamivudine
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What are coronaviruses?
Coronaviruses are enveloped RNA viruses. Two coronaviruses, MERS-CoV and SARS-CoV, cause much more severe respiratory infections in humans than other coronaviruses.
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What is the treatment for SARS and MERS?
Assisting with breathing using a ventilator to deliver oxygen, antibiotics to treat bacteria that cause pneumonia, antiviral medicines, high doses of steroids to reduce swelling in the lungs. Remdesivir, hydroxychloroquine, tocilizumab, vaccines for SARS-
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Different types of viruses. DNA, protein coat, tail to infect bacteria. Genomic material, capsid, protein on surface of membrane. Some viruses have filamentous spore

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Describe how viral infections have proven to
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