Several countries, including India, are seriously looking
at plasma therapy as a potential treatment for Covid-19, the disease caused by
the novel coronavirus. Plasma therapy uses blood donated by recovered patients
to introduce antibodies in those under treatment. We take a look at what
convalescent plasma therapy is, the benefits and risks involved in the
potential treatment, what past research says about it, and more.
Science academy
New Delhi
UPDATED:
Sept 23, 2020
The convalescent plasma therapy uses
antibodies developed within an infected person while he/she is infected with
the novel corona virus. (Photo)
As Covid -19 continues to wreck havoc across
the globe, scientists are racing to develop antidotes for the new corona virus,
which began infecting humans late last year. Scientists and researchers are
exploring various avenues to come up with medical treatments that can fight the
novel corona virus. One such treatment that's in focus right now is Convalescent
Plasma Therapy.
After China and the US, India has given a go
ahead for framing a protocol to conduct a clinical trial for convalescent
plasma therapy. The therapy has been used experimentally in the past and so has
become a ray of hope in the fight against the novel corona virus pandemic.
In this report, we explain what the
convalescent plasma therapy is, the benefits and risks involved, what past
research says and more.
WHAT IS
CONVALESCENT PLASMA THERAPY?
The convalescent plasma therapy aims at using
antibodies from the blood of a recovered Covid-19 patient to treat those
critically affected by the virus. The therapy can also used to immunise those
at a high risk of contracting the virus -- such as health workers, families of
patients and other high-risk contacts.
This therapy's concept is simple and is based
on the premise that the blood of a patient who has recovered from Covid-19
contains antibodies with the specific ability of fighting novel corona virus.
The theory is that the recovered patient's antibodies, once ingested into
somebody under treatment, will begin targetting and fighting the novel corona virus
in the second patient.
The convalescent plasma therapy is akin to
passive immunisation as, according to researchers, it is a preventive measure
and not a treatment for the Covid-19 disease.
HOW
CONVALESCENT PLASMA THERAPY WORKS?
The convalescent plasma therapy uses
antibodies developed within an infected person while he/she is infected with
the novel corona virus.
These antibodies are developed in a patient
as part of the body's natural immune response to a foreign pathogen or in this
case, the novel corona virus. These antibodies are highly specific to the
invading pathogen and so, work to eliminate the novel corona virus from the
patient's body.
Once the patient has recovered, they donate
their blood so that their antibodies can be used to treat other patients. The
donated blood is then checked for the presence of any other disease-causing
agents such as Hepatitis B, Hepatitis C, HIV etc.
If deemed safe, the blood is then taken through a process to extract 'plasma', the liquid part of the blood that contains antibodies. The antibody-rich plasma, once extracted, is then ingested into the body of a patient under treatment.
Speaking about the process the plasma therapy involves, John Hopkins University immunologist Arturo Casadevall, who is spearheading a project to use the therapy, has said, "The concept is simple. Patients who recover from an infectious disease often produce antibodies that can protect against later infections with the same microbe. This immunity can be transferred by giving serum to those at risk of infection."
In a study
co-authored by Casadevall and immunologist Liise-anne Pirofski, the authors write that for effective therapy "a
sufficient amount of antibody must be administered. When given to a susceptible
person, this antibody will circulate in the blood, reach tissues, and provide
protection against infection. Depending on the antibody amount and composition,
the protection conferred by the transferred immunoglobulin [antibodies] can
last from weeks to months."
Besides speaking about the success of the
convalescent plasma therapy, the study by John Hopkins immunologists stated
some of the risks associated with it:
1.
Transfer of blood substances: As the
blood transfusion takes place, there are risks that an inadvertent infection
might get transferred to the patient.
2.
Enhancement of infection: The
therapy might fail for some patients and can result in an enhanced form of the
infection.
3.
Effect on immune system: The
antibody administration may end up suppressing the body's natural immune
response, leaving a Covid-19 patient vulnerable to subsequent re-infection.
This is not the first time convalescent
plasma therapy is being considered as a treatment for viral infections.
1. In 2014, the World Health Organisation (WHO) had
recommended the use of convalescent plasma therapy to treat patients with the
antibody-rich plasma of those who had recovered from the Ebola virus disease.
2. For the treatment of people infected with Middle East respiratory syndrome (MERS), which is also caused by a coronavirus, a protocol for
use of convalescent plasma was established in 2015.
3. During the 1918 H1N1 influenza virus (Spanish flu) pandemic, the therapy was used experimentally.
4. The plasma therapy was used as a treatment during
the H1N1
infection of 2009.
Others serious outbreaks that have seen the
use of this therapy are the SARS outbreak, Measles, HIV, polio and mumps.
PAST
RESEARCH
>>> During the SARS outbreak in 2002, various studies
came to a conclusion that convalescent plasma therapy resulted in earlier
recoveries in patients compared to regular drugs. Under one trial conducted
by Hong Kong University scientists during the SARS outbreak, 80 people were administered convalescent plasma. It was
found that "people treated with it [the therapy] within two weeks of
showing symptoms had a higher chance of being discharged from hospital than did
those who weren't treated [sic]".
>>> In 2009, during the H1N1 outbreak, a
study conducted to analyse the impact of the plasma therapy found that it helped reduce respiratory troubles
and lowered the risk of mortality. The study also concluded that patients
treated with the therapy were discharged within 22 days of treatment.
Ninety-three patients requiring intensive care were part of this study. Out of
them 20 patients were administered the plasma therapy. This treatment group of
20 people showed significant lower mortality than in the non-treatment group,
the study said.
>>> At the time of the outbreak of Ebola Virus Disease
(EVD) in West Africa, the World Health Organization (WHO) had prioritised the
evaluation of the convalescent plasma therapy. A study
conducted in Guinea with
84 Ebola-infected patients revealed that "the transfusion of up to 500 ml
of convalescent plasma with unknown levels of neutralizing antibodies was not
associated with a significant improvement in survival". Essentially, that
convalescent plasma therapy did not turn out to be of much help in the case of
Ebola virus.
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convalescent plasma therapy. The trial showed some improvement in patients' condition.
"No severe adverse effects were
observed. This study showed CP [convalescent plasma] therapy was well tolerated
and could potentially improve the clinical outcomes through neutralizing
viremia [the presence of viruses in the blood] in severe Covid-19 cases,"
the researchers who conducted the trial said.
Another trial conducted by
researchers in Shenzhen,
China treated five critically-ill Covid-19 patients with the plasma therapy and
found "improvement in [their] clinical status".
RAY OF
HOPE
These studies have sparked a ray of hope.
However, researchers caution that it's too early to think of plasma therapy as
an effective treatment. For example, the sample sizes in the Covid-19 plasma
therapy trials are too small to arrive at definite conclusions.
According to a report published in Mayo Clinic's
Research Magazine, the researchers across the world have also
raised the point that there are too many unknowns right now. For instance, what
is the optimal dose of antibodies? At what point during a patient's illness
should treatment be given? Which patients will benefit? These are some that
need to be addressed before reaching concrete conclusions.
The researchers also noted that "some
participants had also received other experimental drugs, such as antivirals,
making it hard to tease out the precise effect of convalescent plasma".
So while plasma therapy remains a ray of hope, we will only know the treatment's efficacy once more studies and trials are conducted.


















