viruses Flashcards
non- enveloped vs enveloped?
NAKED (non-enveloped):
- survive well
- may be bile resistant
- tougher capsid - harder to disinfect
- faecal oral route transmission
ENVELOPED:
- survive transiently outside
- spread by close contact/intimacy/blood/sneezes and coughs etc…
- capsid can dry out
what are the envelopes made of?
lipid bilayer of host origin
PLUS viral-encoded glycoprotein spikes that:
- have receptors to target next cell to attack
- help attach to new cell and facilitate entry
- are the targets for antibodies of host
Pox virus - capsid symmetry? and is it enveloped?
COMPLEX enveloped
describe the 3 capside symmetries
Complex, helical and icosahedral. They can all be DNA strands and can all be enveloped.
COMPLEX can only be DNA strand and can ONLY be enveloped
HELICAL can be DNA or RNA but ONLY enveloped also
ISOHEDRAL can be anything.
HIV virus? enveloped? capsid? RNA/DNA?
retrovirus so - enveloped + ICOSAHEDRAL + RNA strand
how do retroviruses work?
use reverse transcriptase to turn their RNA strand into cDNA and then integrate that into host DNA using integrase before transcribing itself again and reproducing and releasing itself out to infect more cells - a process requiring protease to cleave GAG into matrix, capsid and nucleocapsid (enabling it to be infectious)
(3 enzymes to rmb: reverse transcriptase, integrase, protease)
what does HIV require to get into the cell?
CD4 and chemokine receptors either CCR5 or CXCR4
What are the important viral load figures to remember?
less than 50 means it’s very controlled and AIDS free. Over 200 = AIDS.
TAT?
activator of viral transcription
REV?
mediates RNA nuclear export
VIF?
works against APOBEC to ensure virus not too mutated and still functional
what is APOBEC?
protein that mutates virus by changing C to U on DNA strand - can be both good and bad (APOBEC3 is host protein that also inhibits RT), but mutations can also cause virus to evade immune system
NEF?
removes CD4 from surface of cell - stops T-cells from working
VPU
destroys tetherin
What’s tetherin?
protein that inhibits release of virus from cell surface
SERIN C?
interferes with viral entry
SAMHD1
suppresses RT in myeloid cells by hydrolyzing dNTPs
what cells are affected by HIV?
Mainly CD4 depletion, loss of memory t-cells,
DC, macrophages also affected and can enhance t-cell infectivity
GALT also affected and can never recover even with therapy
which cell controls the acute infection phase of HIV?
CD8 cells
How is HIV diagnosed?
ELISA to look for anti-p24 (capsid) antibodies IF already seroconverted (usually after 3 months)
pre conversion must use RT-PCR - blood test to confirm (pinprick needed)
List some opportunistic infections that are associated w HIV
Kaposi's sarcoma CMV pneumococi jirovecii candida pneumocystis carinii toxoplasmosis reactivation of herpes simplex MCB TB MCB avium complex
Describe HAART
combination of 3 HIV drugs used to fight mutation
Usually 2 NRTI (nucleoside reverse transcriptase inhibitors) + 1 NNRT (non-NRTI) OR 1 protease inhibitor
positive RNA strands means? negative strand means?
positive RNA strands are equivalent to mRNA strand so can immediately be translated, unlike negative strands that must first be converted to positive strands. cells with negative RNA strands need replicative polymerase enzyme to make new negative strands from positive strands because cells don’t contain that enzyme
In any lymphoma/ see lymph nodes what virus should you suspect?
EBV
also in nasopharyngeal carcinoma
what cancers can HPV cause?
cervical carcinoma
anogenital & vulvo-perineal tumours
What is the body’s first line of defence against viruses?
interferon
DNA viruses are HHAPPPPy
Herpes, Hepad, Adeno, Papilo, Parvo, Polyoma, Pox
Hs and Pox have envelope
What is the name of the stage for the time between exposure and onset of a specific clinical sign?
Incubation period
What is the name of the stage where non-specific symptoms like fever and loss of appetite occur?
Prodrome
