Viral Diseases
TFC, P.346, Black’s 2nd, p. 266- , Alcamo 323-, Campbell 6th: , Black’s 6th: 264-294, tbl: 270
DISCOVERY:
Chamberland 1884 developed porcelain filter to remove bacteria
Iwanowski 1892 used filter to try to remove tobacco mosaic disease, “filterable virus”
Beijerinck 1898 showed could be diluted out, destroyed by heat
Forsh & Loeffler 1898 foot and mouth disease caused by filterable agent
Walter Reed 1901 yellow fever also filterable disease (in Cuba)
Twort & d’Herrelle 1917 bacteriophage
TRAITS: All viruses posses: (p 266)
capsid protein coat composed of capsomeres, can contain penetration enzymes
genome may be DNA or RNA, double stranded , single stranded, (+ = mRNA) or (-)
Spikes: glycoprotein for attachment, enzymes to assist attachment
Host range = which species infected
specificity = which tissue affected, determined by ability to attach, multiply and release
three morphologies: icosahedral (20 faces) herpes, polio, cytomegaly
(p 267 for sizes and shapes) helical rabies, TMV
complex small pox, coronavirus, influenza
VARIETY OF VIRUSES, p 270, characterized by comp of genome, enveloped or not, geometry, size
VIRAL REPLICATION:
Obligate Intracellular parasites, replicate inside absorption
Penetration
Synthesis
Maturation
Release
Bacteriophage parts (p 279): capsid, genome, tail assembly, tail piece, tail fibers, tail sheath, tailcore
bacteriophage replication: p 280
lysogeny: p 283 (lysogen. In mammalian cells, called provirus)
enveloped viruses: upon release by budding from host. replication of enveloped virus, p 284
Enveloped viruses are inactivated by hi temp, hi or lo pH, lipid solv, some disinfectants (Cl, H2O2, phenol)
Naked viruses lack an envelope, resist many of the above
EXAMPLES (perhaps not presented during this lecture?)
COMMON COLD: caused in decreasing frequency by : rhinoviruses, paramyxoviruses, enteroviruses, corona viruses, reoviruses, adenoviruses. Can be mixed infection. Portal of Entry: mucous membrane of nose and eyes.
Influenza: H = hemagglutanin, N = neuraminidase
Alterations in H and N make virus undetected by immune system until after infection
1918: Change to H3N2, killed 20 million world wide. More troops died of flu than combat
Herpes form provirus, integrated for life into your DNA: Chicken Pox, Herpes simples I and II
HIV Primarily parenteral POE, through wound or sore. Infects T cells.
TABLE SUMMARIZING MAJOR CLASSES OF VIRUSES
Cls | genome | env?, shape | example | diseases |
RNA VIRUSES: | ||||
Ia | positive (mRNA)ssRNA, smallest rna |
naked
polyhedral |
Picornavirus |
enteroviruses: repl. 1st in mucous, then GI: polio (70+) rhinoviruses: cannot surv in GI tract, 100+, most Hepatoviruses: hepatitis A (fecal/oral) |
Ib | positive (mRNA)ssRNA |
enveloped polyhedral |
Togavirus |
rubella german measles many arboviruses (arthropod borne viruses): EEE, St. |
II | negative ssRNA |
Enveloped helical |
Paramyxovirus |
measles rubeola mumps infection of salivary glands, testes viral pneumonia upper resp and bronchitis |
negative
ssRNA |
Enveloped
helical |
Rhabdovirus | some arboviruses, only rabies infects man
newcastle virus in chickens |
|
III | negative ssRNA |
enveloped helical |
Orthomyxovirus | influenza A, B, C, can agglutinate RBC typed
H: hemagglutinin, N: neuraminidase (H1N1, etc) |
IV | pos ssRNA | envel, | Coronavirus | helical, 2nd cause, Common Cold, “infectious bronchitis” |
V | positive ssRNA |
enveloped helical |
Retroviruses | requires reverse transcriptase, becomes provirus: leukemia, Human Immunodeficiency Virus (AIDS) |
DNA VIRUSES: | ||||
Ia | dsDNA linear |
naked polyhedral |
Adenovirus | 40+: respiratory
GIitis (20% severe diarrhea in children) |
Ib | dsDNA linear |
Enveloped polyhedral, |
Herpesvirus | 80+, latency characteristic, usually nerves:
simplex 1: oral,, fever blisters, simplex 2: genital, Varicella zoster: chicken pox, shingles, cytomegalovirus (leading teratogenic virus) Epstein-Barr: infectious mononucls. |
Ic | ds DNA linear |
Enveloped largest, mst complex, |
Poxvirus | brick shaped, cause inclusion bodies
small pox cowpox = vaccinia certain warts (molluscum contagiosum) |
II | dsDNA circular |
naked polyhedral |
Papovavirus | papilloma: 25+ in humans: strain 18 connected cerv CA
polyoma: 2 in humans, vasculating. Warts (SV-40 : simian virus) |
ssDNA | linear, naked polyhedral |
Parvovirus | parvo (“small”) |