RNA viruses Flashcards
What makes up an influenza virus?
single stranded sense RNA
segmented RNA
envelope glycoproteins HA and NA critical for entry and egress of virus into host cell
What HA and/or NA are a major human IVA?
H1, H2 and H3
What new IVA virus has recently moved from birds to human?
H7N9 influenza virus A
How did the H7N9 virus come about?
via re-assortment, where 2 or more infleunza viruses co-infect a single host and exchange genes
How can influenza antigenic change?
structure of hemagglutinin (H) and neuraminidase (N) change
What is a shift influenza change?
major change, new subtype
exchange of gene segment = no existing immunity
may result in pandemic
What is a drift influenza change?
minor change, same subtype
point mutations in HA and NA genes
may result in epidemic
What is a SARS-CoV-2 lineage?
phylogenetic cluster
associated with an epidemiological event
What is the Middle East Respiratory Syndrome Coronavirus (MERS-CoV)?
camels may not show signs of infection however they may secrete MERS-CoV in nasal discharges, faeces, milk and urine
What is the shape of Human immunodeficiency virus (HIV)?
icosahedral, enveloped ss(+) RNA
What does HIV infect?
CD4+ cells by binding of viral gp120
How does HIV replicate?
conversion of viral RNA to complementary DNA, which then integrates into host cell genome
What are the two major forms of HIV?
HIV-1 and HIV-2
What does HIV-1 cause?
almost all human infections
What does HIV-2 cause?
less aggressive disease progression
What is the most dominant HIV-1 group?
Group M
How is HIV transmitted?
percutaneous and permucosal
What happens in the early phase of HIV infection?
initial viruses are M-trophic (macrophage-trophic)
envelope glycoprotein gp120 is able to bind to CD4 and chemokine receptors called CCR5
What happens in late phase HIV infection?
most cells are T-tropic (T-cell-tropic) having gp120 binding to CD4 and CXCR4 found on T4-lymphocytes
virulent and induce syncytia
How do we diagnose AIDS?
CD4+ T cells <200 cells /μl
pneumocystis jiroveci pneumonia or one defining illnesses
What is a long term non-progressers (LTNP)?
individuals who have attenuation of the HIV-1 genome, specifically the nef gene, which interferes with viral replication and can influence disease outcome
What attribute in the CCR5 gene that causes a resistance to infection of HIV-1?
32bp deletion in the CCR5 gene
What is the CCR5 gene?
is a 7-tm G protein-coupled chemokine receptor expressed on T cells, macrophages, dendritic cells and microglia
