PDF containing information about CoVISHIELD. A recent development in the field of science for battle against coronavirus disease.

1. ChAdOx1 nCoV- 19 Corona Virus
Vaccine (Recombinant)
COVISHIELD
By: Karan kapil
M.Sc Biochemistry (final year)
Roll Number: 1937

2. Recombinant Vaccines
• Vaccines were initially developed on an empirical basis, relying mostly on attenuation or inactivation of
pathogens. Advances in immunology, molecular biology, biochemistry, genomics, and proteomics have added new
perspectives to the vaccinology field.
• The use of recombinant proteins allows the targeting of immune responses focused against few protective
antigens. There are a variety of expression systems with different advantages, allowing the production of large
quantities of proteins depending on the required characteristics.
• Live recombinant bacteria or viral vectors effectively stimulate the immune system as in natural infections and
have intrinsic adjuvant properties.
• DNA vaccines, which consist of non-replicating plasmids, can induce strong long-term cellular immune
responses.

3. • Current vaccination traditionally known to be effective requires immunization of an individual with two or more
doses and this consists of a “prime-boost regime”. As the vaccines used in the prime and boost consist of the same
formulation, such regime is called homologous prime-boost. On the other hand, an immunization regime involving
different formulations used sequentially in more than one administration will be called heterologous prime-boost.
• Research results accumulated over the past decade have shown that heterologous immunization can be more effective
than homologous immunization, especially against intracellular pathogens, the infectious agents of higher complexity
that are currently considered to be more challenging for vaccine development
Fig. Different types of Recombinant vaccines by
Genscript.

4. Vaccine for combating CoVID-19
• The COVID-19 pandemic which probably is the most devastating one in the last 100 years after Spanish flu.
• The novel beta-coronavirus SARS-CoV-2 is believed to have emerged last year in 2019 in Wuhan from Bats.
Crossing the species barrier it entered human beings with furtherance of infection through human to human
transmission.
• The beta-coronaviruses have jumped between the species and have caused three zoonotic outbreaks namely, SARS
CoV (2002-03), MERS-CoV (2012), and SARS-CoV-2 (2019- till date) in the last 2 decades.
• Exposure to SARS-CoV-2 can result in a range of clinical outcomes, varying from asymptomatic infection to severe
acute respiratory distress and death.
• The current COVID-19 pandemic has urged the scientific community internationally to find answers in terms of
therapeutics and vaccines to control SARS-CoV-2. Published investigations mostly on SARS-CoV has taught lessons
on vaccination strategies to this novel coronavirus.
• This is attributed to the fact that SARS-CoV-2 uses the same receptor as SARS-CoV on the host cell i.e. human
Angiotensin Converting Enzyme 2 (hACE2) and is approximately 79% similar genetically to SARS-CoV.

5. • Structurally coronaviruses are pleomorphic, enveloped viruses with a characteristic fringe of projections composed of
S protein on their surface. These viruses are equipped with a positive sense ssRNA genome, which is complexed with
the nucleocapsid (N) protein forming helical nucleocapsids. The genome is both capped and polyadenylated.
• SARS-CoV and SARS-CoV-2 bind a common host receptor, hACE2, to gain entry into the cell but SARS-CoV-2 binds
the receptor with a higher affinity than the SARS-CoV.
• Many efforts have been directed towards the development of the vaccines against COVID-19, to avert the pandemic
and most of the developing vaccine candidates have been using the S-protein of SARS-CoV-2.
• Though the efforts on COVID-19 vaccines started very early, initially in China, as soon as the outbreak of novel
coronavirus erupted and then world-over as the disease was declared a pandemic by WHO.
• Various platforms for vaccine development are available namely: virus vectored vaccines, protein subunit vaccines,
genetic vaccines, and monoclonal antibodies for passive immunization which are under evaluations for SARS-CoV-2,
with each having discrete benefits and hindrances.

6. • As of July 2, 2020, the worldwide SARS-CoV-2 vaccine landscape includes 158 vaccine candidates, out of which 135
are in the preclinical or the exploratory stage of their development.
• Currently, mRNA-1273 (Moderna), Ad5-nCoV (CanSino Biologicals), INO-4800 (Inovio, Inc.), LV-SMENP-DC,
Pathogen-specific aAPC (ShinzenGeno-Immune Medical Institute), and ChAdOx1 (University of Oxford) have entered
the phase I/II clinical trials.
• Our main focus is on chAdOx1 recombinant vaccine, which is in India commercially available as COVISHIELD.
• COVISHIELD is a protein sub-unit vaccine. A subunit vaccine is the one which is based on the synthetic peptides or
recombinant antigenic proteins, which are necessary for invigorating long-lasting protective and/or therapeutic immune
response.
• The subunit vaccine, however, exhibits low immunogenicity and requires auxiliary support of an adjuvant to potentiate
the vaccine-induced immune responses. An adjuvant may enhance the biological half-life of the antigenic material, or it
may ameliorate the immunomodulatory cytokine response.

7. • The S protein of the SARS-CoV-2 is the most suitable antigen to induce the neutralizing antibodies against the pathogen.
The S Protein consists of two subunits. The S1 subunit has the NTD, RBD, and RBM domains while the S2 subunit
comprises of FP, HR 1, &2.
• The virus enters into the cell via endocytosis by utilizing the S-Protein mediated binding to the hACE2 receptor.
• Therefore, the S-Protein and its antigenic fragments are the prime targets for the institution of the subunit vaccine.
• The S glycoprotein is a dynamic protein, possessing two conformational states i.e. pre-fusion and post-fusion state.
Therefore, the antigen must maintain its surface chemistry and profile of the original pre-fusion spike protein to preserve
the epitopes for igniting good quality antibody responses.
• Coronaviruses are enveloped, positive sense single-stranded RNA viruses with a glycoprotein spike on the surface, which
mediates receptor binding and cell entry during infection. The roles of the spike protein in receptor binding and
membrane fusion make it an attractive vaccine antigen.
• COVISHIELD as we know that is a recombinant adenovirus vaccine was developed using codon optimized S
glycoprotein and synthesized with the tissue plasminogen activator (tPA) leader sequence at 5’ end. The sequence of
SARS-CoV-2 coding for amino acids (2 to 1273) and the tPA leader and was propagated in the shuttle plasmid.

8. • This shuttle plasmid is responsible for encoding the major immediate early genes of the human cytomegalovirus (IE
CMV) along with tetracycline operator (TetO) sites and polyadenylation signal from bovine growth hormone (BGH)
between the Gateway recombination cloning site.
• The Adenovirus vector genome is constructed in the Bacterial Artificial Chromosome by inserting the SARS-CoV-2 S
gene into the E1 locus of ChAdOx1 adenovirus genome.
• The virus was then allowed to reproduce in the T-Rex 293 HEK (Human Embryonic Kidney 293) cell lines and purified
by the centrifugation (CsCl gradient ultracentrifugation).
• The absence of any sub-genomic RNA (sgRNA) in the intra-muscularly vaccinated animals from the pre-clinical trials is
indicative of the escalated immunity against the virus.
• COVISHIELD is for intramuscular (IM) injection only, preferably in the deltoid muscle.
• One dose (0.5 ml) contains: 5 × 10 viral particles.
• Both COVISHIELD (manufactured by Serum Institute of India Pvt Ltd) and COVID-19 Vaccine AstraZeneca
(manufactured by AstraZeneca) are ChAdOx1 nCoV- 19 Corona Virus Vaccines (Recombinant).

9. • The ChAdOx1 nCoV-19 vaccine (AZD1222) consists of the replication-deficient simian adenovirus vector ChAdOx1,
containing the full-length structural surface glycoprotein (spike protein) of SARS-CoV-2, with a tissue plasminogen
activator leader sequence. ChAdOx1 nCoV-19 expresses a codon-optimised coding sequence for the spike protein.
• In rhesus macaques, a single vaccination with ChAdOx1 nCoV-19 induced humoral and cellular immune responses.
Protection against lower respiratory tract infection was observed in vaccinated non-human primates after high-dose
SARS-CoV-2 challenge.
• ChAdOx1 nCoV-19 is safe, tolerated, and immunogenic, while reactogenicity was reduced with paracetamol. A single
dose elicited both humoral and cellular responses against SARS-CoV-2, with a booster immunisation augmenting
neutralising antibody titres. Some side effects are also there that can not be ignored. All possible side effects are listed in
the last slide.

10. • Pharmaceutical Form of COVISHIELD is colourless to slightly brown, clear to slightly opaque and particle free with a
pH of 6.6.
• COVISHIELD vaccination course consists of two separate doses of 0.5 ml each. The second dose should be
administered between 4 to 6 weeks after the first dose. However, there is data available for administration of the second
dose up to 12 weeks after the first dose from the overseas studies.
• Efficacy and safety data are currently limited in individuals ≥ 65 years of age, No dosage adjustment is required in
elderly individuals ≥ 65 years of age.
• The safety and efficacy of COVISHIELD in children and adolescents (aged >18) is not yet established.
Special warnings and special precautions for use:
• Hypersensitivity: As with all injectable vaccines, appropriate medical treatment and supervision should always be
readily available in case of an anaphylactic event following the administration of the vaccine.

11. • Concurrent illness: As with other vaccines, administration of COVISHIELD™ should be postponed in individuals
suffering from an acute severe febrile illness. However, the presence of a minor infection, such as cold, and/or low-
grade fever should not delay vaccination.
• Thrombocytopenia and coagulation disorders: As with other intramuscular injections, COVISHIELD™ should be
given with caution to individuals with thrombocytopenia, any coagulation disorder or to persons on anticoagulation
therapy, because bleeding or bruising may occur following an intramuscular administration in these individuals.
• Immunocompromised individual: It is not known whether individuals with impaired immune responsiveness,
including individuals receiving immunosuppressant therapy, will elicit the same response as immunocompetent
individuals to the vaccine regimen. Immunocompromised individuals may have relatively weaker immune response
to the vaccine regimen.
• Fertility: Preliminary animal studies do not indicate direct or indirect harmful effects with respect to fertility.

12. References:
1.WHO
Coronavirus disease (COVID-19) situation report—181.
World Health Organization, Geneva2020.
2.van Doremalen N, Haddock E, Feldmann F et al.
A single dose of ChAdOx1 MERS provides protective immunity in rhesus macaques.
Sci Adv. 2020; 6eaba8399.
3.van Doremalen N et al.
ChAdOx1 nCoV-19 vaccination prevents SARS-CoV-2 pneumonia in rhesus macaques.
BioRxiv. 2020; (published online May 13.) (preprint).
4.Folegatti PM, Bellamy D, Roberts R et al.
Safety and immunogenicity of a novel recombinant simian adenovirus ChAdOx2 as a vectored vaccine.
Vaccines (Basel). 2019.
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