positive strand RNA viruses

positive strand RNA

• genome +RNA (5’ to 3’)= mRNA

• can be used immediatly for translation

negative strand RNA

• genome -RNA (3’ to 5’) = complementary to mRNA

• a direct translation is not possible

• trnascription to mRNA is necessary

Order: Nidovirales - coronaviruses

Order: Picornavirales - Norov., hepatitis A v, RHDV, Foot-and-mouth disease v

Order: Tymovirales - plant viruses, e.g. Turnip yellow mosaic virus

several viral families without any order

• genome size (27,6 - 31kb)

• recombination via template switch

• mutations, error rate of the viral RNA-Pol.

-> new strains and genotypes of already existing virus species

-> novel virus species

• enveloped

• diameter 80-120nm

• pleomorph

• spike protein (S)

• matrix protein (M)

• membrane protein (E, envelope)

• hemagglutinin-esterase (HE), some ßCoV (similar to neuraminidase)

• nuceloprotein (N)

genome

• RNA genome

• ss, unsegemented, positive polarity

• 5’ End: cap strucutre; 3’Poly-A tail

The S protein determines cell, organ and host tropism

• deletion within the N-terminal RBD

• -> loss of the ability to bind to sialic acids

• inhibtion of cellular proteases involved in S activation, maily TMPRSS2

• prevent S mediated fusion

• alternative routes of entry

  -> can just adapt to usage of another receptor

-> viral protein

• target viral Mpro

• inhibit cleavage of polyporus. 1a and 1b

• Nirmatrevir (Paxlovid)

• target viral proteins involved in replication

• inhibit viral replication by binding to RdRp

• Remdesivir, Molnupiravir

• -> no complete genome generated

• —>not as promising as monoresavir or others

• worldwide circulation

• 10-30% of common colds in winter

• mainly mild disease, headache, rhinitis, coughing

• severe illness may occur (pneumonia, bronchitis) in young, or ols immunocompromised persons

• secondary infections (e.g. influenza A)

• Initial cases: Animal traders, slaughterhose workers, cook

• antibody prevalence on animal markets

  • animal trader: 40% seropositive

  • slaughterhouse workers: 20% seropositive

  • greengrocers: 5% seropositives

• detection of antibodies and viral RNA in civet cats

• susceptibel to SARS CoV infections

• no AB or viral RNA in wild civet cats

  • civet cats are not the reservoir of SARS CoV

  • intermediate hosts

• detection of SARSCoV related viruses in horsehoe bats

  -> horseshoe bats are the reservoir of SARSCoV

Hypothesis 1: SARS-related bat viruses cannot bind to the human receptor ACE2

-> mutations in the spike protein have been detcted in civet cat virus

-> these mutations might enable a more efficient interaction with the human receptor

Hypothesis 2: SARS-related bat viruses can bind to the human receptor ACE2

-> multiple transmissions between civet cats and humans led to genetic variations

-> increased human-human trnasmissability

• detection of closely related viruses in bats

  -> reservoir of MERS-CoV

• but: A direct contact between humans and bats is very are

• AB is dromedars camels : Oman 100%positive, Egypt 98,2%

• MERS-CoV circulates in dromedary camels since more than 30 years

• high number of viruses in nasal tract

  -> camel easy transmitted

  -> high number of viruses in alveolar tract = different to spread

• replication of intestine or deeper parts of the lung => no transmission from camel to human