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| Frage | Antworten |
| What is one of the smallest human viruses? | Poliovirus |
| Do viruses contain ADP or ATP? | No, they must use the host machinery to carry out protein synthesis and replication |
| What is special about Cytomegalovirus? | It contains both RNA and DNA |
| What are the four categories of viral genomes? | ssDNA, ssRNA, dsDNA, dsRNA |
| What are the 3 things encoded by a viral genome? | Enzymes for replication, proteins for assembly of progeny, proteins that defend against host immune system (only in larger viruses) |
| What is the important difference between a regular virus and a retrovirus? | Retroviruses are diploid whereas the rest of viruses are haploid (only contain one copy of their genome) |
| What is Tropism? | When the virus can only infect a limited number of cell types but there are viruses out there for almost every cell |
| All viruses except retroviruses are ______________ | Haploid |
| What main features are used to classify viruses? (3) | 1) what type of host they infect 2) virus morphology 3) genome type |
| What are the viral suffixes for Order, Family, Subfamily, Genera, and Species? | O: virales, F: Viridae, SF: Virinae, G: Virus, S: Virus |
| If a viral genome is segmented then what type of genome must it be? | RNA |
| Define Retrovirus | Any virus that inserts its DNA in the host cell DNA to be replicated by the host machinery eg. HIV |
| What is the largest human virus? | Pox Virus |
| What is a capsomere? | It is a subunit of a capsid |
| What are the 2 most common types of symmetrical arrangements of the capsid? (and what are 2 exceptions) | Helicle (goes around the genome), and Icosahedral (20 triangles forming a sphere) - Pox and Reovirus are neither |
| Virus has a very small genome so how does it deal with having to code for a capsid? | Codes for a small subunit and just produces mass amounts of that. and the subunit is thermodynamically favorable to be in the capsid formation. |
| Why are viruses one of the most genetically diverse groups of organisms? | This is because they lack mutation repair enzymes, their genomes replicate quickly, and they interact with other viruses (reassortment, recombination) |
| What is a viral strain? | it is the same virus but it is isolated from certain geographical regions and therefore may show different infection level or pathogenicity |
| What is a viral Type? | Same virus, but responds differently to antibody detection |
| What is a Viral Variant? | A virus whose phenotype is different from the wildtype |
| When comparing viral genomes which are typically more prone to mutations? DNA or RNA genomes? | RNA |
| Define Recombination | Genetic information is exchanged between 2 distinct adjacent genomes |
| What type of polymerase is in a Retrovirus that uses reverse transcriptase? | RNA dependent DNA polymerase |
| What is a point mutation? | Single base change |
| Intramolecular recombination by "copy-choice" occurs only in... | RNA viruses - a viral polymerase switches template strand during replication. |
| What is homologous recombination? | This is when similar strands of DNA "cross over" and are incorporated into the other virus's genome |
| What are some consequences of genetic changes in viruses? | Antiviral drugs become ineffectice, host antibodies no longer recognize the virus, virus develops a new host range |
| What are the 6 steps of Viral Multiplication? | 1) Absorption 2) Penetration 3) Uncoating 4) Synthesis 5) Assembly 6) Release from host cell |
| How do NAKED Viruses enter the cell? | - direct penetration, only the genome enters, capsid stays outside |
| How do ENVELOPED viruses enter the host cell? | - by fusion - the lipid bilayer fuses with the virus envelope |
| Where does the Pox virus genome undergo translation? | In the cytoplasm (this is an important exception!) BECAUSE: they have a large genome and can encode for most components necessary for their own replication |
| Where do most viruses assemble? | In the host nucleus |
| How do NAKED viruses get released from the cell? | Lysis (death of the cell- not advantageous because this alerts the immune system) OR Exocytosis |
| What are the different severities of viral infections? (poorly worded) | Acute, Chronic, Latent |
| What is a transforming infection? | Virus causes the cell to loose growth control - could lead to tumor formation. |
| What are Cytopathic Effects? | Virus induced damage. |
| What is a common portal of entry into the host for a virus? | Mucosal surface |
| Define Reassortment | exchange of genetic material between 2 segmented genomes (RNA) - commonly happens in Influenza, and this is why we get vaccinated each year |
| What type of molecules are usually the receptor molecules? | glycoproteins |
| Naked viruses penetrate through _____________ whereas enveloped viruses penetrate through ____________, but they can both enter by _________________ | Direct Penetration (capsid remains extracellular), Fusion (capsid and genome enter the cell), Endocytosis |
| What is an advantage of being a +RNA virus? | Genome can be used directly as mRNA |
| What do progeny virus particles need to contain before they can leave the infected cell? | 1) Viral nucleic acid 2) Accessory Proteins 3) Viral Enzymes |
| What is an inclusion body? | compact masses of viruses that could be found in the nucleus or cytoplasm of the host cell |
| What happens during maturation of the virus progeny? | Processing of protein precursors into their final products through protease (any enzyme that performs proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in a polypeptide chain) activity. |
| How does an enveloped virus get released from the host cell? | Budding, therefore the envelope is comprised of both viral and host proteins |
| Define Pathogenesis | the disease process occurring as a result of the interaction of the host and the infectious organism |
| Define Tropism... again | establishes the nature of a disease |
| What are the 4 types of Viral Infections? | Abortive, Lytic, Persistent, Slow |
| Define Abortive infection | muture virions are not produced |
| Define Acute/ Lytic Infections | rapid onset, period of disease, followed by clearance of the virus - usually death of host cell by lysis |
| Define Persisten Infection | linger and are not readily cleared by the immune system - host survives and harbors the virus |
| What are the 3 types of Persistent Infections? | Chronic, Latent, Transforming |
| Chronic Infection... | Can be lifelong, continuous production and shedding of virions |
| Latent Infection... | intermittent periods of viral replication and shedding with long periods of dormancy when the virus is not replicating |
| Transforming... | the virus causes the cell to lose growth control - overexpression of growth factors - resulting in uncontrolled growth and division of that cell - can cause tumor |
| Define Syncytium Formation... | this is when the membrane of a virally infected cell fuses with neighboring (infected or non infected) cells producing a giant multi-nucleated cell |
| What type of viruses usually have syncytium formation? | Enveloped viruses because the glycoproteins play a role in the attachment and are inserted into the host cell membrane |
| What are the non cytopathic effects of viruses? | altered shape, detachment from substrate, transformation |
| Every viral infection follows these same 6 basic steps... | 1) Entry into host 2) Immune Evasion 3) Entry into cells and primary replication 4) Spread within the host 5) Cell injury and clinical illness 6) Shedding |
| What are mechanisms of immune evasion? | Inhibiting Antigen Presentation, change or remove surface proteins, molecular mimicry, or entering immunologically priviledged sites (eye or brain) |
| Define Viremia... | the presence of the virus in the bloodstream which allows for very effective means of spreading |
| What is primary viremia? | when the virus gets transfered to a specific organ that in turn leads to secondary viremia |
| Define Virulence... | the relative capacity of a pathogen to infect and cause harm to a host cell |
| 6 approaches to control and prevention of viral disease... | Quarantine, hygiene and sanitation, vector control, change of lifestyle, immunization, antiviral chemotherapy |
| Define Passive Immunization | Administration of antibodies - immune serum or immunoglobulin |
| Define Active Immunization | administration of an antigen (naturally or in artificial preparations of vaccines) |
| Define Live attenuated vaccine | mutant organisms that possess a growth characteristic that prevents the organism from replicating like the wild type that causes disease |
| What type of immune response is induced by a live attenuated vaccine? | humoral and cell-mediated protection (identical to that of a natural infection) |
| Define Innactivated vaccine... | killed organism or just parts of the organism, innactivated by heat or chemical treatment |
| Can you give an innactivated vaccine to an immunocompromised individuals? | Yes! |
| What are the three types of innactivated vaccines? | Killed Whole Cell (dead bacteria or viruses), Fractional Protein based (parts of the organism), Fractional Polysaccharide-based (only bacterial, NOT viral) |
| What is a recombinant/ hybrid vaccine? | insert the vaccine antigen in an organism that is not pathogenic to humans |
| What type of vaccines can be given to infants less than 6 months of age? | Inactivated, because they arent affected by circulating antibodies |
| Can you use simultaneous vaccines at once? | yes, it does not increase the potential for adverse affects, or decrease the efficacy of the vaccines |
| What is the main goal of antiviral chemotherapy? | to inhibit viral replication |
| What are strategies of antiviral chemotherapy drugs? | they aim to target a viral function or structure, have to interfere with a cellular function so that the virus cannot replicate, important that it only kills virus infected cells |
| What are 4 limitations of Antiviral drugs? | 1) really hard to target virus specific processes or structures 2) if theres already too many virions then the drug wont work 3) the virus can become latent 4) emergence of drug resistance |
| What does Acyclovir act against? | Various herpes viruses |
| What is the mode of action of Acyclovir? | It get phosphorylated to triphosphate which lets it integrate into viral DNA and inhibit DNA replication |
| If an immunocompromised individual develops resistance to Acyclovir during a drug regimen which drug do you suggest instead? | Foscarnet - this has a different mode of action and prvents the cleavage of phosphate from new deoxynucleoside triphosphate |
| What are 2 important uses of Acyclovir? | 1) treat HSV1, HSV2 in immunocompromised patients, VZV patients, and HSV encephalitis. 2) treats shingles and chickenpox |
| What is the mode of action of Valacyclovir? | Converted to acyclovir and then acts the same as acyclovir |
| What do you use Valacyclovir for? | 1) HSV1, 2 and VZV 2) Shingles, herpes labialis and genital herpes in immunocompetent adults |
| What is the advantage of Valacyclovir over Acyclovir? | Can use less dose and a higher plasma concentration is attained |
| What is a disadvantage to using Valacyclovir? | There is no IV form |
| What is the mode of action of Famiclovir? | phosphorylated by viral thymidine kinase to penciclovir - this inhibits viral DNA polymerase and DNA replication |
| What is Famciclovir used for? | HSV1, HSV2, and VZV |
| What is an advantage of Famciclovir? | treatment is only for 5-7 days |
| What is the mode of action of Foscarnet? | binds to DNA polymerase and prevents it from cleaving phosphate from newly added deoxynucleoside triphosphate, also inhibits HIV1 reverse transcriptase. |
| When do you use Foscarnet instead of Acyclovir? | When there is resistance to acyclovir |
| What is treated by Foscarnet? | 1) HSV1, HSV2, VZV, CMV, HIV1 2) CMV in immunocompromised patients 3) Mucocutaneous HSV infections in immunocompromised patients |
| What is a special feature of Foscarnet | It can cross the blood brain barrier |
| What is the mode of action of Trifluidine/ Viroptic? | Its a fluorinated pyrimidine nucleoside - not sure of how it works, but results in non functional viral proteins |
| What are the uses of Trifluridine? | Treats Keratoconjunctivitis, HSV1, HSV2, Vaccinia Virus, CMV, and some adenovirus |
| What are some risks of using Trifluridine? | 1) 4% have burning or stinging in the eyes 2) some have palpebral edema 3) superficial punctuate keratopathy (disease of the eye) |
| Ganciclovir is the most effective drug against? | CMV |
| What is the mode of action of Ganciclovir? | Same as Acyclovir! |
| What can we treat with Ganciclovir? | HSV1, HSV2, VZV, EBV, CMV |
| Even though Ganciclovir treats CMV what cant it do to resolve CMV | IT cant resolve CMV infection of the CNS even though it penetrates the CNS |
| What is the mode of action of valganciclovir? | Works like ganciclovir |
| What can we treat with Valganciclovir? | CMV in AIDS patients |
| What is the mode of action of Cidofovir? | inhibits viral DNA synthesis |
| What do we treat with Cidofovir? | It is used to treat CMV infections in AIDS patients (like valganciclovir) |
| What is the special thing about Formivirsen/ Vitravene? | It is the first anti-sense drug to be FDA approved (a stretch of nucleotides complimentary to CMV that inhibit protein synthesis) |
| What is the mode of action of Fomivirsen/ Vitravene? | Single stranded anti-sense piece of DNA, complimentary to a unique DNA sequence within the CMV mRNA, this inhibits viral protein synthesis |
| What do we treat with Formisen/ Vitravene? | CMV retinitis in AIDS patients |
| What are the 4 important Anti-Influenza Drugs? | Amantadine/ Symmetrel, Rimantadine/ Flumadine, Zanamivir/ Relenza, Oseltamivir/ Tamiflu |
| What is the mode of action of Amantadine/ Symmetrel? | interferes with ion channel function of the M2 protein and acts indirectly on hemagglutinin (the viral protein that facilitates viral absorption and entry) |
| Which strain of Influenza cannot be treated with Amantadine? | Influenza B, becase it doesnt have an M2 protein |
| What is the use of Amantadine? | Preventative treatment of Influenza A |
| What is the mode of action of Rimantadine/Flumadine? | Occurs early during viral replication and might possibly affect viral uncoating |
| What is the use of Rimantadine/ Flumadine? | Preventative treatment of Influenza A |
| What is the mode of action of Zanamivir (relenza)? | Inhibits viral neuraminidase and prevents replication of influenza A and B |
| What is the mode of action of Oseltamivir (tamiflu)? | inhibits viral neuraminidase and prevents replication of influenza A and B |
| What is the mode of action of Anti-Retroviral Drugs? | they inhibit reverse transcriptase and hence lead to termination of nucleic acid synthesis |
| What are the 7 types of Anti-Retroviral Drugs? | 1) Nucleoside Analog 2) Nucleotide Analog 3) Non nucleoside analog 4) Fusion Inhibitor 5) Maraviroc/Selzentry 6) Protease Inhibitor 7) Integrase Inhibitors |
| What do fusion inhibitors act against? | GP41, CCR5, and MAcrophages |
| Maraviroc/ Selzentry mode of action? | It prevents entry of virus into macrophages. It is a CCR5 coreceptor antagonist |
| What is the mode of action of Protease Inhibitors? | inhibit HIV maturation steps by targeting aspartyl protease enzyme essential for cleaving the polyprotein gag-pol into individual proteins which are required for infectivity |
| What is the mode of action of Integrase inhibitors? | blocks the action of integrase, an enzyme that aids in the integration of viral genetic material into the genome of the target cell |
| What is the Standard of Care Regimen? | 1 or 2 protease inhibitors in combination with 2 nucleoside reverse transcriptase inhibitors in order to block viral replication at different stages and avoid resistance |
| Truvada is combination of which 2 types of anti retroviral drugs? | a nucleoside RT inhibitor, and a nucleotide RT inhibitor |
| find out if we have to know about the monoclonal antibodies | . |
| What are 2 methods of direct examination of viruses in lab? | Light microscopy, Electron Microscopy |
| What is a down fall of Direct Examination? | Cant tell exactly what virus it is within a family of viruses. |
| What is the method of virus detection by serology taking advantage of? | the specificity and sensitivity of antigen-antibody interactions |
| What is the difference between Immunofluorescence microscopy and Immunoassays? | Immunofluorescence tags attach to antibodies whereas Immunoassay tags attach to Viral enzymes |
| What is the process of western blotting? | proteins get extracted from a sample and separated in a gel through electrophoresis then from gel onto membrane - colour develops on the membrane where the antibodies have bound |
| What are advantages of using PCR? | 1) only need a bit of DNA 2) can be amplified right from tissue sample 3) can be sequenced to conclusively identify the agent |
| Nucleic acid hybridization is the process of... | using complementary DNA or RNA used as a probe |
| What are the four families of viruses that most commonly cause ocular infections? | Herpesviridae, Adenoviridae, Papovaviridae, Poxviridae |
| What is the family, Subfamily, Genus, and species of HSV 1 and 2... | Herpesviridae, Alphaherpesvirinae, Simplexvirus, Human Herpes Virus 1 and Human Herpes Virus 2 |
| What type of capsid do HSV 1 and 2 have? | Icosahedral |
| What types of genome does HSV have? | dsDNA, linear |
| Is HSV enveloped or not? | Enveloped! |
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