Question

currently we are dealing with Corona virus pandemic. Let's explore about Corona virus through this discussion.

Describe structure, classification, mode of viral replication, cultivation techniques, prevention and treatment of this virus. (Make sure you answer for all of these characteristics)

Answer 1

• Corona virus disease 2019 ( COVID-19) is defined as illness caused by a novel corona virus now called severe acute respiratory syndrome coronavirus 2.
• First identified in Wuhan city, Hubei province China.
• On 11th march 2020 WHO declared as pandemic.

STRUCTURE:

• It belongs from the family of Coronoviridae of the order Nidovirales.
• Large single stranded RNA.
• Spherical to pleomorphic particles of size varying from 80-160nm in length.
• It has four structural protein called envelope(E), spike (S) , membrane (M) and nucleocapsid (N).
• ProteinS,M and E form envelope of virus .
• M protein is responsible for shape of envelope.
• S and M protein are transmembrane protein and are responsible for replication.
• Protein N is associated with RNA.
• S protein embedded in the envelope making a crown like structure so called corona virus.
• Spike protein binds to human ACE-2 receptor which are present in respiratory tract.
• ​​​​​​​

CLASSIFICATION:

• ​​​​​​​There are four types of covid-19 seen :

1. Alpha corona virus ( alpha CoV)
2. Beta corona virus ( beta CoV)
3. Delta corona virus ( delta CoV)
4. Gamma corona virus ( gamma CoV)

( Cascella M. Features, evaluation and treatment of corona virus (Covid-19). Stat pearls.2020)

• Beta CoV divides in five sub genera or leneages.
• Other types of strains are four:

1. HCoV- 229E
2. HCoV - OC43
3. HCoV - HKU1
4. HCoV - NL63.

MODE OF VIRAL REPLICATION:

• Infection is through exposure to respiratory secretion.
• Corona virus attach their glycoprotein receptor of host cell through S protein.
• Entry is mediated by receptor mediated endocytosis.
• Group 1 corona virus bind with metalloproteases and angiotensin converting enzyme 2.
• When RNA of virus is released into the cytoplasm, then translation of RNA gives polyprotein that went proteolytic process to form RNA dependent RNA polymerase.
• Translation gives rise to viral protein.
• M pritein embedded in endoplasmic reticulum and anchores with golgi apparatus to gorm golgi ER complex.
• E and M protein trigger budding of virion.
• These virion are transported to plasma membrane where released by exocytosis via golgi apparatus.

CULTIVATION TECHNIQUE:

• VIRUS isolated from oropharyngeal and nasopharyngeal specimen.
• For isolation , limiting dilution 50ml pipette of serum free DMEM ( Dulbeco minimal eventual medication) into column 2-112of 96 wellbtissue culture plate.
• Pipette 100 micro litre of clinical specimens and dilluted 2 fold across plates.
• Then trysinized and ressured in Vero cells in DMEM containing 10% fetal bovine serum, 2× penicillin/ streptomycin, 2× antibiotics and 2× amphotericin B at concentration 2.5 ×10 to the power 5 cells m/L.
• Innoculate in humified 37°C incubator at 5 atm CO2 .
• Standard plaque assay for SARS COV 2 .
• CPE ( cyto pathic effect) checked daily.
• To confirm PCR and full genome sequencing done.

​​​​​​​PREVENTION:

• A distance of at least 1 meter (3feet) should be maintained between people.
• Cover your mouth and nose with tissue or elbow while sneezing and discard the tissue in the coverd bin.
• Use of face mask.
• Perform hand hygeine for 30sec with soap.
• Alcohol based hand disinfectant is effective in destroying the virus.
• Preventing control and transmission from object and surfaces .
• Personnel protective equipment for the dentala and the medical professionals.

​​​​​​​TREATMENT:

• EVEN THOUGH there is no Covid-19 special treatment currently available so we use Drug repurposing strategy.
• Some of the drugs used are :
  • Chloroquine : obtained from cinchona plant and used in treatment of malaria. It slows down entry and replication of covid-19.
  • Hydroxychloroquine.
  • Combination of lopanavir and ritonavir.

Vacvine is skill under trial so orevention is the only key to fight this battle.