Virus structure, Baltimore classification, replication cycles, lysogeny, viral evolution.
Virology
Virus
Obligate intracellular replicating entity: nucleic-acid genome (DNA or RNA, ss or ds) in protein capsid, optionally enveloped. Encode <…
Viral capsid
Protein shell enclosing viral genome. Icosahedral (adenovirus, HIV matrix) or helical (TMV, Ebola) symmetry; assembled from identical…
Baltimore classification
Seven groups based on genome + replication strategy: (I) dsDNA, (II) ssDNA, (III) dsRNA, (IV) +ssRNA, (V) -ssRNA, (VI) ssRNA-RT…
Retrovirus
+ssRNA virus using reverse transcriptase to integrate DNA copy into host genome. HIV, HTLV, endogenous retroviruses (~8% of human genome).…
Lytic cycle
Viral replication culminating in host-cell lysis + progeny release. Phage T4 reference: adsorption → injection → replication → assembly →…
Lysogeny
Temperate-phage integration into host genome (prophage) with latent carriage, until SOS-induction triggers lytic switch. λ repressor-Cro…
Viral quasispecies
RNA-virus population concept (Eigen): swarm of related variants generated by high mutation rate (~10⁻⁴-10⁻⁵ per base). Natural-selection…
Viral envelope
Host-cell-derived lipid bilayer studded with viral glycoproteins (HA-NA, spike, gp120). Enveloped viruses enter by membrane fusion;…
Viral entry
Receptor binding (ACE2 for SARS-CoV-2, CD4 for HIV, sialic acid for influenza) + fusion or endocytosis. Antiviral target (fusion…
Vaccine platforms
Live-attenuated, inactivated, subunit, toxoid, viral-vector (Ad26, ChAd), mRNA-LNP (Pfizer, Moderna). mRNA platform transformed COVID-19…
Viral dynamics (Nowak-May) target-cell ODE
Nowak-May target-cell-limited ODE: dT/dt = λ - dT - βTV; dI/dt = βTV - δI; dV/dt = pI - cV. Yields R_0 = βλp/(dδc); in HIV/HBV/HCV the…
Eigen quasispecies error threshold
Eigen 1971 quasispecies model: replicator-mutator dynamics on Hamming-cube genome space. Master sequence persists only if μ < ln(s)/L…
Virus discovery (Beijerinck 1898)
M Beijerinck 1898 'contagium vivum fluidum' tobacco mosaic virus; modern virosphere + Earth-Virome metagenomics.
Baltimore class (1971)
D Baltimore 1971 classification 7 groups by genome + replication-strategy; modern ICTV taxonomy + viral-realms.
HIV (Barre-Sinoussi-Montagnier 1983)
Barre-Sinoussi-Montagnier 1983 (Nobel 2008) HIV-1 isolation; modern HAART + PrEP + CRISPR-cure trials.
Influenza (Shope-Andrews 1931-1933)
Shope 1931 swine + Andrews-Smith-Laidlaw 1933 human influenza; modern WHO-GISRS surveillance + reassortment.
SARS-CoV-2 (Zhou 2020)
Zhou-Yang-Wang 2020 SARS-CoV-2 sequence Wuhan; modern Omicron + XBB + JN.1 variants 2024; pandemic-preparedness reform.
Phage (Twort-d Herelle 1915)
Twort 1915 + d Herelle 1917 bacteriophage; modern phage-therapy + Felix-Cocktail 2024 FDA AMR-rescue therapy.
Ivanowski (1892)
D Ivanowski 1892 + Beijerinck 1898 tobacco-mosaic-virus; modern modern foundational text + electron-microscopy Ruska 1939 first virus.
Hershey-Chase (1952)
A Hershey-M Chase 1952 (Nobel 1969) DNA-is-genetic-material; modern modern foundational text in molecular-biology + 2024 SARS-CoV-2…
Reverse transcriptase (Temin-Baltimore 1970)
H Temin-D Baltimore 1970 (Nobel 1975) RT; modern modern HIV-PCR + 2024 Mu-mediated retro-transposition + LINE-1 active-transposon.
PCR (Mullis 1985)
K Mullis 1985 (Nobel 1993) PCR; modern modern qPCR + dPCR + ddPCR + 2024 single-molecule + isothermal LAMP / NEAR.
HCV (Houghton 1989)
M Houghton-Q-L Choo 1989 (Nobel 2020) HCV-cloning; modern modern DAA-cures sofosbuvir + ledipasvir 2014 + 2024 elimination targets.
CRISPR-virology (Mojica 2005)
F Mojica 2005 + Marraffini 2008 + Doudna-Charpentier 2012 (Nobel 2020); modern modern phage-defense + base / prime-editor 2024.