Convalescent Plasma: An Evidence-Based Old Therapy to Treat Novel Coronavirus Patients

Novel Coronavirus (nCoV-2019) is a highly infectious viral outbreak that has so far infected more than 110 million people worldwide. Fast viral transmission and high infection rates have severely affected the entire population, especially the old aged and comorbid individuals leaving significantly less time to find some effective treatment strategy. In these challenging times, convalescent plasma (CP) therapy came as a ray of hope to save humankind. It is a form of passive immunization that has been used to treat various infectious diseases since 1890, including the 1918 Spanish flu, 2002/03 SARS-CoV, 2009 H1N1, 2012 MERS-CoV, and 2014 Ebola outbreak. The transfusion includes administration of CP containing a high value of neutralizing antibodies against the virus in hospitalized patients. This chapter summarizes the potential outcome of CP therapy in the treatment of nCoV-2019 patients.


Introduction
Convalescent plasma (CP) is defined as a blood plasma that is withdrawn from an individual who had encountered some infectious disease and had recovered with a required amount of antibodies against the disease [1].It is a way of passive immunization [2].The concept has been widely used in medical sciences, especially in the case of infectious disease outbreaks.It is an old therapy used since late 1800 [3].In Germany (1890), researchers treated diphtheria patients with sera from immunized animals.Afterward, the patients were treated with the sera from the recovered ones [4,5].The wide use of CP therapy was established during the Spanish influenza outbreak between 1918 to 1920 [6].Humanity faces a great survival challenge when a new infectious disease emerges and becomes a pandemic.We do not have much to do in such cases, and we mostly rely on our scientific or medical fraternity.Therefore, during such a pandemic/epidemic, there is an urgent need to have a quick, available therapeutic option [3].A study estimates that on an average basis, there have been 5.3 newly emerged viruses between 1940 to 2004, which includes 60-70% of viruses having an animal origin and have potential to the infect humans [7].In such circumstances where there are very few options available for the treatment, and when a patient condition is worsening, CP therapy has always been an excellent choice for clinicians.Humans can get exposed to these viruses by different means of exposure, and generally, these are considered "unavoidable or by chance."In viruses, the major therapeutic challenges arise because of the high degree of genetic changes, which may be due to mutation or genomic instability [8].
In December 2019, a new virus emerged in the Huanan Seafood market and resulted in a dreadful outbreak in China, and the virus rapidly spread to more than 200 countries globally [9].Further sequence-based analysis of respiratory tract samples identified a novel strain, which was distinct from the other known coronavirus strains, subsequently named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the disease caused by SARS-CoV-2 infection was designated as novel coronavirus-2019 (nCoV-2019) by the World Health Organization (WHO) [10].The emergence of novel coronavirus came up as a big challenge for the concerned authorities of the various country [11].Clinicians had no clue regarding its treatment approaches that made the situation even worse [12].Soon, on March 11, 2020, WHO declared it a pandemic.In its initial days, the unavailability of any potential drug/therapy resulted in an exponential increase in infections.
For more than a century, this therapy has been widely explored against various outbreaks.During the 2002/3 SARS-CoV outbreak, 2012 Middle East Respiratory Syndrome (MERS-CoV) outbreak, and H1N1 pandemic (2009), CP therapy was successfully explored [13][14][15][16].Similarly, for the 2013/14 Ebola virus infection treatment, CP therapy was recommended as an empirical treatment approach [17].Based on previous experiences and similarities in terms of virological and clinical characteristics among the SARS-CoV, MERS-CoV, and nCoV-2019 [18], CP therapy was explored for its efficacy in the battle against newly emerged (nCoV-2019) pandemic.In February 2020, for the first time, a group of researchers from China reported and published the usefulness of CP in nCoV-2019 severe patients in Journals like JAMA [17] and PNAS [16].CP therapy can be used as a prophylaxis for various infectious diseases, primarily when an outbreak occurs.
Many studies showed a significant correlation between CP therapy and improved clinical symptoms.In a preliminary study involving 5 critically ill nCoV-2019 patients, 400 mL CP administration (high neutralizing antibody (NAb) titer >40) resulted in improved clinical characteristics [17].A similar study with 10 critically ill patients who received 200 mL of CP (one dose; NAb>1:640) significantly improved clinical symptoms within 3 days and viremia resolution within 7 days [16].Altuntas et al. carried out a CP-based study on 888 patients, reported that CP administration reduced the ICU stay (p = 0.001) and MV support (p = 0.02) [19].However, there is some uncertainty with large-scale CP transfusion.A PLACID trial published on 464 patients found that CP therapy did not reduce the progression to severe illness or 28-day mortality (19% treatment Vs. 18% control group) [20].A clinical trial on 228 patients reported no significant benefits in symptoms and overall mortality between the intervention (10.93%) and the placebo group (11.43%) [21].Similarly, a review article that studied 20 articles reflected that the efficacy of CP therapy in nCoV-2019 patients is uncertain [22].Therefore, the US FDA recommended the use of CP as an investigational product [23].Here, in this chapter, we have explored CP therapy potentials on nCoV-2019 based on available literature.

Methods
Relevant review search was done using keywords "nCoV-2019 or COVID-19, Convalescent Plasma or Plasma therapy".The search engine included electronic databases like PubMed, Google Scholar, and ClinicalTrials.gov.

History of convalescent plasma
This therapy is not new for nCoV-2019, as physicians used this therapy more than a century ago [24].Convalescent plasma has been used historically for a long time to develop passive immunity in patients suffering from various bacterial and viral diseases such as measles [25], mumps [26], and poliomyelitis [27] by transferring plasma carrying NAb from previously recovered patients.Although antibiotics have replaced CP usage in bacterial diseases, it remains a useful tool for novel viral infections for which the vaccine is not available.
A literature study reported that serotherapy was used during the Spanish flu (influenza A) pandemic in 1918-1920 for the first time, but this therapy was also used before the Spanish flu pandemic [3].Serotherapy was tried as a therapeutic treatment in a poliomyelitis outbreak in New York in 1916 [28].In 1916 (Tunis), some researchers again performed this therapy for the measles [6].Hess AF in 1915 applied serotherapy to treat mumps and successfully prevented the testicular complications in the affected patients [29].However, the credit goes to the Italian Francesco Cenci, who for the first time used convalescent serum as a therapeutic means to save the children that were exposed to measles [30].Cenci performed this experiment by withdrawing 600 mL blood from a patient who recovered from measles after 21 days.After that, he administered this therapy to four children aged 4-8 years [30].The results were overwhelming as the children did not contract measles following the treatment.Since the mortality rate in measles was high, ranging from 6-7%, this prophylactic therapy lasted for a long time [31].There was again a measles outbreak in December 1906 in Italy where this therapy was administrated in forty sick children, and all the patients recovered successfully.One children had severe symptoms, but after therapy, the child showed milder symptoms.Luigi Concetti performed a similar therapy in 1900 on two children affected with diphtheria in Rome, Italy [6,32].After that, CP therapy was used for treating many diseases like MERS, Ebola, SARS etc. (Table 1) [33].
During H1N1 influenza epidemics in 2009, CP therapy was given to the patients who were in critical conditions and were presented to the hospitals with severe respiratory problems.The patients showed reduced viral load in the respiratory system and there was also decreased cytokine response and mortality rate [14].CP therapy was also used in the Ebola epidemic in 2013 in West Africa regions [34] high mortality occurred in early 21st century [35].In South Korea, MERS became endemic, and there was an urgent need for CP therapy as the mortality rate was very high, and there was no effective treatment available [35].Eighty patients of SARS-CoV in Hong Kong were given early administration of convalescent plasma, and they demonstrated an increased prognosis and got early discharge from the hospital [15].A study in Taiwan showed that the administration of CP in 3 patients reduced the viral load [36].

Significance of convalescent plasma therapy during SARS-CoV and MERS-CoV outbreaks
Earlier, CP therapy was used to treat similar coronavirus outbreaks, i.e., SARS and the MERS in the last two decades (Table 2).

SARS-CoV outbreak
The first outbreak of the twentieth century that surfaced from China in 2002 led to severe respiratory illness and pneumonia-like symptoms in patients.A case study published in 2003 reports that CP administration as an adjunctive treatment alongwith ribavirin and prednisolone in a 57-year-old SARS patient on Day 14 reduces the viral load and fever within a few days.Further, a better resolution of a basal lung infiltrate was seen in chest X-ray post-convalescent plasma treatment [40].A group of Hong-Kong-based researchers, Soo et al. (2004) and Cheng et al. (2005), first reported using convalescent plasma as an emergency therapy to contain this outbreak.They found that patients treated with steroids and CP had low mortality and got early discharge from the hospitals compared to patients treated with steroids alone [15,37,41].
Further, they have found that patients with early administration of convalescent plasma (before 14 days of symptoms onset) have shorter hospital stay and have less mortality (p = 0.08) than those who received convalescent plasma after 14 days [15].A similar study by Yeh et al. reports about the beneficial effect of CP administration in SARS infected Health-workers who were severely ill and showed no response to available antiviral treatments.The CP administration in them resulted in a reduced viral load and fever within a day, followed by resolution of pulmonary infiltrates and a time-dependent increase in anti-SARS-CoV IgM and IgG antibodies [36].In conclusion, early administration of convalescent plasma led to better patient outcomes in terms of fast recovery, short hospital stays, reduction in viral load, and improvement in clinical symptoms.

MERS-CoV outbreak
This outbreak took place due to another strain of respiratory illness causing coronaviruses, referred to as MERS, pointing to its origin from central-east Asia (Arabian countries).From the prior experience of using CP during SARS-CoV outbreak, passive immunotherapy by administering NAb in patients serves as a vital tool in battle with this disease.Chan et al. in 2012, found that convalescent sera of previously recovered SARS patients have cross-reactive NAb that can work effectively against novel coronavirus strains [42].Corti et al. in 2015, based on anecdotal evidence, studied the prevalence of MERS specific antibodies in dromedary camels from the middle east (Oman) and European countries (Netherland and Chile).They found that all Omanian camels in their study group had MERS-CoV-specific NAb in their serum compared to European animals, highlighting the importance of passive immunotherapy upon successfully detecting the transmission source.These antibodies of CP have the potential to neutralize the MERS-CoV if administered in the patients [38].The effectiveness of CP was also reported by van Dorelman et al. in 2017, in common marmosets infected with MERS-CoV.They found that marmosets treated with hyperimmune plasma and m336 (monoclonal antibodies) showed a reduction in viral load and overall severity [39].However, the use of MERS-CoV antibodies is very challenging, as some studies report that they are produced at a low level and are short-lived in mild infections [43,44].

Mechanism of action of convalescent plasma
Convalescent plasma to be donated contains specific antibodies for particular infectious diseases or pathogens.These antibodies possess neutralization activity.This activity is achieved in different ways: either by impeding the binding of viral  particles with the endosomes, by hindering the viral protein proteolytic cleavage, by blocking the release of viral progeny, or by inhibiting the viral surface glycoproteins from invading the human cells [45].A report published by Lu et al. suggests that when a neutralizing antibody (NAb-3BNC117) was passively administered on mice model, it helped block NAb helped block the new infection, enhanced clearance of the infected cells, and accelerated the HIV-1 infected cell clearance [46].The other mode of action includes antibody-dependent-cellular-phagocytosis (ADCP), complement system activation, and antibody-dependent cellularmediated cytotoxicity (ADCC).CP antibodies induce clearance of virusinfected cells by ADCP.A cross-talk is established among the CP antibodies, which helps in eliciting the Fc-dependent effector functions.The activated complement system helps eliminate the virus by two means.First, by direct means i.e., through complement dependent cytotoxicity.Second, indirect means, i.e., by phagocytosis, help clear the associated complement targets.In the case of nCoV-2019, the recovered patients may develop serum antibody response (IgG) against various virus epitopes [1].This IgG competes with the angiotensin-converting enzyme-2 receptor (ACE-2) to bind with the virus receptor-binding domain (RBD) and may neutralize the nCoV-2019 infection.Therefore, in this case, the binding domain acts as both, i.e., the epitope for antibody and a binding site for the receptor enzyme [2].Literature suggests that when CP therapy is administered at an early stage of nCoV-2019 infection, the therapeutic effect may be more effective [47].In most viral infections, the peak of viremia starts appearing in the early first week of the illness.However, between days 10-14 or early in some cases, the host primary immune response starts exerting its potential effect [47].

Use of CP therapy on nCoV-2019 patients
In the absence of any specific treatment of nCoV-2019 and vaccines with proven long-term results, CP administration comes to the rescue for an effective treatment for critically ill nCoV-2019 patients (Tables 3 and 4).This is a kind of passive immunization method where CP from a recovered nCoV-2019 individual is obtained and uses them on diseased individuals to resolve the symptoms and reduce disease course by suppressing the viremia [18].The use of passive immunotherapy is a widely used approach to combat various infectious diseases, which consisted of various formulations such as whole blood, pooled human sera containing immunoglobulin and convalescent plasma.Plasma collected through apheresis with subsequent CP transfusion is the most commonly used passive immunotherapy approach to battle against pandemics happened earlier [24].Theoretically, a person who got infected from an infectious disease, upon recovery, blood is screened for NAb specific to the causative pathogen suffered earlier.The convalescent plasma containing a high-titer NAb is used as a therapy to maximize the capacity to neutralize an infecting pathogen (Figure 1) [56].
Studies from the current nCoV-2019 pandemic suggested that it elicits a robust immune response resulting in cytokine storm which generates high levels of IgM and IgG mostly that persists for months even after the symptom disappears.Thus, a large window period and maximum chances of successful extraction of high titer anti-SARS-CoV-2 immunoglobulins act as a boon to utilize it as passive immunotherapy [57,58].Further studies have elaborated on NAb response.More severe disease may lead to higher antibody response levels [58], and antibody level decreases considerably within the first 90 days after symptom start among individuals suffered from the mild disease [59].

Source/donor requirement
In order to overcome various challenges for enrolment of successful plasma donors during the outbreak different strategies such as social distancing, travel restrictions, and imposed lockdowns have been implemented.To recruit possible plasma contributors, this includes donor self-identification, social awareness utilizing social/formal/e-media outlets and clinician referral of individuals got previous exposure to the infection [60].NAb titres can be examined in possible donor or CP units through ELISA/chemiluminescence assay or pseudovirus neutralization assays which are known as indirect methods or directly under biosafety level 3 conditions by using live SARS-CoV-2 neutralization assays.USFDA has permitted the use of CP therapy under the clause of EUA for hospitalised nCoV-2019 infected patients [61].CP units were categorized as lower or higher antibody titre based on qualitative chemiluminescent immunoassay for detection of neutralizing IgG against SARS-CoV2 spike protein [60].The collected plasma is treated for pathogen inactivation to avoid the risk of transfusion transmitted infections.A donor can donate CP weekly for several months till the antibody titers are high.There are several factors that restrict the donation, including the individuals who already received the CP for their nCoV-2019 treatment (minimum of 90 days) are not allowed to donate blood products.

Who can donate CP
• Person who has confirmed validated diagnostic record of SARS-CoV-2 infection.
• Physical examination, including the absence of fever and respiratory symptoms.Minimum of 14-day post-recovery with no symptoms.
• A person who meets the standard routine blood donation criteria.The donor and recipient should be ensured for ABO compatibility • CP must be free of HIV, HCV, HBV syphilis, human T-cell lymphotropic virus 1 and 2, and Trypanosoma cruzi and any other transfusion/locally transmitted infections.
• CP from either male donors or from female donors with no pregnancy history is preferentially used to avoid any risk of TRALI (Transfusion Related Acute Lung Injury) [62].
• For retrospective testing and scientific investigations, donors blood products (serum, plasma, whole blood) should be saved at −80 0 C.

Plasma donation
Convalescent plasma donors may be identified during national disease-specific cohorts, during hospitalization of the patient, by the practitioners treating outpatients, and through various specific online/social helpline-networks.

FDA guidelines
The FDA recommends three approaches for the administration of CP.First is directed for the treatment of patients of nCoV-2019 through EUA.Second, patients with severe nCoV-2019 illness who are unable to participate in RCT through expanded access protocol.The third one involves clinical trials where clinicians are advised to enroll patients in the trials to examine the effectiveness of CP therapy in nCoV-2019 [63].

Dosage
Various dosage regimens were utilized in various hospital setups for the management of SARS-CoV2 infected patients.Universally 200 ml of convalescent plasma in 1 or 2 doses with an infusion rate of 100 to 200 ml/h are administered with an interval of 12 hr.apart.The dosage regimen is decided according to body weight and antibody titer [64].Standard hospital procedures and recommendations should be followed for thawing and transfusion of plasma through a peripheral or central venous catheter.

Follow up
CP therapy is still an experimental model.For future scientific investigations and correlations, the blood products of the recipient should be stored (prior and after transfusion).As per published trials, the response post CP therapy is mainly assessed i.e., PaO2/FiO2 ratio clinically or through Ct scan or X-ray (radiological) of the infected organ.However, elicitation of nCoV-2019 antibody titer or increased ALC in recipients, as well as a decline in SARS-CoV2 viral load either in terms of absolute quantification or increase of cycle threshold (Ct) value, could be considered as surrogate endpoints [65].

Risk associated with the use of CP therapy
Major adverse events associated with CP transfusion are not much evident so far.However, risk assessment before/after the transfusion is important.Several studies/clinical trials have shown that the use of CP therapy in severely ill nCoV-2019 patients is safe and early administration with adequate anti-SARS-CoV-2-NAb titer is helpful in faster recovery and survival of nCoV-2019 patients [18,66].CP therapy is contraindicated in certain individuals such as those who are allergic to plasma protein or sodium citrate, patients with selective IgA deficiency (70 mg/ dl in patients four years old or older), or the ones who received treatment with immunoglobulins in the last 30 days as it could lead to the development of serum sickness [67].
However, large U.S. national registry, through its interim report, showed that among over 100,000 hospitalized adults that had nCoV-2019 infection, low incidences of transfusion reactions were documented in the first 5,000, and 20,000 patients transfused with nCoV-2019 CP therapy, which is suggestive of the fact that transfusion of convalescent plasma is safe and poses no additional risk of complications among hospitalized patients with nCoV-2019 [52,68].An RCT compared the safety of convalescent plasma transfusion with fresh frozen plasma transfusion documented a comparatively less rates between the controls (7%) and CP (4%) group of patients and highlighted the safety profile of CP transfusion [69].

Conclusions
In the absence of any effective antiviral drug and vaccine (long term effect is not yet established) to prevent the infection, several approaches have been explored to reduce the duration of the disease course.One therapeutic approach that is being utilized globally is convalescent plasma therapy against nCoV-2019.Once the person recovers from nCoV-2019, the blood contains antibodies against the causative virus.In emergency situations, these antibodies can be given to other affected people to provide immediate immunity against the virus, reducing the severity and helping in faster recovery.FDA has not yet approved the use of CP as a treatment of nCoV-2019.It is administered under the EUA or an IND.However, further largescale, world-wide controlled clinical trials are needed to prove the efficacy of the CP therapy for the current pandemic.
© 2021 The Author(s).Licensee IntechOpen.This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Figure 1 .
Figure 1.Diagrammatic representation of the use of CP in nCoV-2019 patients.

Table 1 .
Use of CP therapy during various diseases outbreak.

Table 2 .
List of studies describing the significance of CP therapy during SARS-CoV and MERS-CoV outbreaks.

Table 3 .
List of completed CP based Clinical trials registered on ClinicalTrial.gov nCoV-2019 patients.