Delhi–With the announcement of COVAXIN by Bharat Biotech and ZyCov-D
Vaccine by Zydus Cadila the proverbial silver line in the dark clouds
of COVID19 appears at the horizon. Now the nod was given by the Drug
Controller General of India CDSCO (The Central Drugs Standard Control
Organisation) for the conduct of the human trial for the vaccines,
marks the beginning of the end.
In the past years, India has emerged as one of the significant vaccine
manufacturing hubs. Indian manufacturers account for 60% of vaccine
supplies made to UNICEF. The vaccine for novel coronavirus may be
developed anywhere in the world, but without Indian manufacturers
involved the production of required quantity is not going to be
feasible.
Vaccine race:
More than 140 candidate vaccines are under various stages of
development. One of the leading candidates is AZD1222 developed, Jenner
Institute of University of Oxford and licenced to AstraZeneca
British-Swedish multinational pharmaceutical and biopharmaceutical
company headquartered in Cambridge, England. The MRNA-1273 vaccine
developed by Kaiser Permanente Washington Health Research Institute,
Washington and taken up for production by the US-based Moderna
pharmaceutical is just a step behind. Both these firms have already
inked an agreement with Indian manufacturers for production of the
COVID vaccines.
Parallelly Indian institutions have also engaged in R&D for the
development of vaccines in India. With the primary scientific inputs
coming from institutions like Pune based ICMR institution National
Institute of Virology and Hyderabad based CSIR institution Center for
Cellular and Molecular Biology, six Indian companies are working on a
vaccine for COVID-19. Along with the two Indian vaccines, COVAXIN and
ZyCov-D, the world over, 11 out of 140 vaccine candidates have entered
the human trials.
Immune system:
Antigen from the pathogen and antibodies produced by the human immune
cells can be thought of as matching the compatible pair. Every
pathogen has specific molecular structures called as antigen. They are
like the surface with a particular hue and design. Once infected by
the germ, the human immune system develops antibodies that match the
antigen.
Just as the retailer of design matching material stockpile hundreds of
design pieces of riots of colours and hues, our immune system has ten
thousand types of antibodies. If the pathogen is a known enemy, the
immune system can pull the matching design piece from the stock. Once
the match is made the pathogen is inactivated. No longer it can
infect.
However, if the microorganism is unfamiliar, and mainly when it has
evolved for the first time, there is no matching colour and hue in the
repertoire. Nonetheless, unlike the textile, the antibody can evolve.
At first, near matches are tried. After various cycles of antibody
development, the best fit matures. The time lag between the
identification of the main surface colour that is an antigen, and
finding a pairing design piece, that is antibodies, is what makes the
infection mild or severe. If only the immune system can neutralise the
germ instantly, the infection can be prevented.
Immune System memory and vaccine :
Like a new hue of design piece once acquired is stocked for future,
once the new antibody matching the antigen evolves, it is retained in
the immunological memory. Next time the same pathogen invades,
immunological memory gets activated, and twinned antibody is released.
The infection is nipped in the bud. We acquire immunity.
A vaccine is a method to artificially inducing the immunological
memory. Once the antigens of the nasty pathogen are introduced, the
immune system is triggered into developing pairing antibodies and
immunological memory.
There are many ways in which one can artificially stroke the immune
system to develop antibodies and memory. The bottom line is presenting
the antigens of the novel coronavirus to the human immune system. From
adenovirus-based live-attenuated virus to recombinant genetic
technology is used to develop several types of vaccines. Two among the
various possibilities produced in India are inactivated virus vaccine
and DNA plasmid vaccine.
How these vaccines work
We can inactivate a whole virus with heat or formaldehyde (that is
‘killed’), yet keep the antigen molecular structures still intact.
However, the inactivated virus will not be able to infect or cause
disease, as it is no longer functional. The Bharat Biotech’s COVAXIN
uses the virus isolated from an Indian patient by the National
Institute of Virology to develop the inactivated virus vaccine.
Novel coronavirus infects the human cells with the help of its spike
proteins. The spike protein of the virus binds with the ACE2 receptors
on the surface of the human respiratory tract cells. Once the virus
fuse, the viral genome is slipped into the human cell where around a
thousand copies of the virus are made in just ten hours. These baby
viruses emigrate to nearby cells. Infection can be arrested if only we
can deactivate the spike protein of the novel coronavirus. Thus the
antigen on the spike protein is a crucial vaccine target. If the
antibody blocks the spike protein, then the virus cannot bind the cell
and multiply.
The genomic code of the spike protein is spliced into a harmless DNA
plasmid. This modified plasmid DNA with the genetic code of viral
spike protein is introduced into the host cells. The cellular
machinery translates the DNA and produces the viral protein encoded in
the genome. The human immune system recognises the alien protein and
develops a matching antibody. After this vaccination, if at any time,
we are infected by the novel coronavirus, then sensing the spike
protein antibodies are released instantly. The immune killer cells
seize deactivated viruses. Contagion is arrested even before infection
sets in.
By: Dr TV Venkateswaran :