Virology Final Part 5 Flashcards
What is antigenic drift?
Minor changes in glycoproteins due to the accumulation of changes in the amino acid sequence and result in minor antigenic differences
What is antigenic shift?
If two different influenza strains infect the same cell, the genes re-assort and can result in a strain that no one has immunity to
How do NA inhibitors work and what are two examples of them?
-
- tamiful and relenza
How do ion channel inhibitors work and what are two examples?
- block the release of influenza by blocking the M2 protein
- symmetrel and flumadine
How does influenza develop drug resistance?
A mutation in the gene that codes for the ion channel M2– it could change such that the drug no longer interacts with the protein
How are retroviruses characterized?
A long interval between the initial infection and the onset of serious clinical symptoms
Where was the origin of the two types of HIV?
HIV-1: North America
HIV-2: isolated from AIDS patients in West Africa
What are the four groups of HIV-1?
M,N,O and P
What are CRFs?
Circulating recombinant forms
What is the structure of HIV?
- Enveloped, spherical to pleomorphic, matrix layer, spike proteins gp120 and gp41
- inside: nucleocapsid + genome= 2 strands of ssRNA (+), RT, integrase, Vif, Vpr, Nef, p7, protease,
Where does the tRNA associated with HIV come from?
The host cell from the previous infection
Is the first step in HIV replication translation on a ribosome?
No— the virus is not completely uncoated, and the RT happens in the core fo the virus
How does HIV cleave its polyprotein?
- it cleaves the polyprotein using a protease, but there is never gag-env-pol, it’s either gag or gag-pol
What are the functions of the gag, pol, and env genes?
Group specific antigen gene: capsid, nucleocapsid, matrix, protease
Polymerase gene: RT, integrase
Env: encodes the envelope GlycoProteins— gp120, gp41
What are the HIV regulatory genes?
Tat, rev, nef, vif, vpr, Vpu
- control the ability of HIV to infect a cell, produce new copies of the virus, or cause disease
What converts RNA genome into a dsDNA genome?
RT
How does RT work?
- RT acts as an RDRP and synthesizes the complementary strand of DNA
- RT acts as RNase and degrades the RNA strand
- DNA dependent DNA POL reads the DNA template, and makes dsDNA
- Results in dsDNA that is slightly longer than the original RNA
What is the best target for the RT enzyme for an anti-viral therapy?
RDRP
Where does the RT step (RNA to DNA) happen? Why can’t this happen until the virus enters the host cell?
In the virus’ core in the cytoplasm; there is no source of nucleotides without being in the host cell
What is the function of gp120?
Docking glycoprotein
What is the function of gp41?
Transmembrane glycoprotein
What is the first step in the HIV genome replication cycle?
RT transcribes the RNA genome into dsDNA, and it is integrated into the host cell DNA
What are the three activities of the RT enzyme?
- RNA dependent DNA polymerase
- RNase H
- DNA dependent DNA polymerase
How does HIV attach to the host cell?
- HIV binds to receptor CD4 with gp120, and this triggers a conformational change in gp120 and allows it to bind to the co-receptor, either CCR5 or CXCR4
- triggers conformational change in gp41 and results in a fusion peptide inserting in the cell membrane and fuses with the cell membrane
What is the mutation that causes HIV resistance?
CCR5-Δ32
What are the packaged tRNAs for?
A primer for reverse transcription
What transcribes the integrated virus dsDNA genome?
Host cell RNA polymerase
Can there be damage to the host cell when HIV is integrated?
It depends on if it is integrated in a gene or regulatory sequences
What are the steps of HIV genome integration?
- Recognition of the target site by the integrase
- Staggered cutting of host cell DNA at target site, making short stretches of ssDNA
- Ligating DNA into host cell DNA
- Repair of ssDNA resulting in duplication of target
What proteins does Gag produce?
NC (nucleocapsid), CA (core), MA (matrix), PR (protease)
What proteins does Pol make?
RT and IN
What proteins does env make?
Gp120 and 140
How does HIV transcribe Gag AND Pol?
Ribosome frameshift— skips over the gag stop codon by shifting 1 nucleotide back at the slippery sequence towards the 5’ end
When does HIV virus maturation happen? What does it look like?
Gag and Gag-Pol are still intact and the RT and IN are non functional; after the virus egresses
