4.3 Convalescent Plasma
Convalescent plasma refers to the plasma collected from patients recovered from an infection and the development of the corresponding antibodies. The plasma is infused into patients with the disease. This passive antibody administration may provide immediate immunity to susceptible individuals (Bloch et al., 2020). The unique characteristic of convalescent plasma is that it does not only contain antibodies but instead has all the ”molecular tools” extracted from the COVID-19 healer. The repertoire of plasma-based factors that are infused with neutralizing antibodies include anti-inflammatory cytokines, anti-clotting factors, natural antibodies, specialized pro-resolving mediators (e.g., resolvins, protectins, maresins), defensins, pentaxins, collectins, plus an undefined number of unknown mediators (Rojas et al., 2020). This molecular arsenal can play a role in improving virus clearance, participating in B and T lymphocytes, limiting the cascade of inflammation, preventing microembolism and promoting tissue repair (Rojas et al., 2020). Anti-SARS-CoV-2 non-neutralizing antibodies that bind to the virus without hindering virus replication can still promote recovery by recruiting innate immune cells (Rojas et al., 2020). Convalescent plasma has aroused great interest for prophylaxis in health care workers and other caregivers while no other treatment for virus infections is available or in an emergency (Jahrling, Frame, Rhoderick, & Monson, 1985; Jahrling & Peters, 1984). Historical data have reported the safety and effectiveness of convalescent plasma in other infectious diseases. Spanish flu was the first viral infection that is effectively responded to convalescent plasma in clinical studies. A meta-analysis of 8 studies on Spanish influenza (1703 patients) showed that treatment with convalescent plasma can reduce mortality (Luke, Kilbane, Jackson, & Hoffman, 2006). There are studies on the treatment of SARS-CoV (Cheng et al., 2005), MERS-CoV (Ko et al., 2018), and H1N1 (Hung et al., 2011) with convalescent plasma. Prior studies reveal that three infected healthcare workers recovered from SARS-CoV infection after administration of convalescent plasma from three recovered SARS-CoV patients, and there was no residual virus from the convalescent plasma as determined using RT-PCR. The ultimate results of no viral load and increased anti-SARS-CoV IgM and IgG indicated that efficacy of convalescent plasma and it can be a potential treatment for virus infections. One of the healthcare workers got pregnant later and positive anti-SARS-CoV IgG was detected in the newborn, which indicated a possibility that anti-SARS-CoV antibody can transfer from mother to newborn passively (Yeh et al., 2005).
There is new data on convalescent plasma used to treat COVID-19 in the current pandemic. Mechanical ventilation was given to five crucially ill COVID-19 patients (age range, 36-65 years; 2 women); all had received antiviral agents and methylprednisolone concurrently. The patients recovered from SARS-CoV-2 infection after plasma transfusion from donors (age range, 18-60 years) and continuously improved as follows; 4 of 5 patients got their body temperatures normalized within 3 days. The viral loads declined and became negative within 12 days after the transfusion, while SARS-CoV-2–specific ELISA and neutralizing antibody titers increased after the transfusion. 3 patients was released from the hospital (hospitalization time : 53, 51, and 55 days), and 2 were in stable condition 37 days after transfusion (Shen et al., 2020). The administration of convalescent plasma was monitored in this preliminary uncontrolled case series, and improved the patient’s clinical status. However, the limited sample size cannot effectively demonstrate the efficacy and safety of convalescent plasma. Therefore, clinical trials of COVID-19 patients treated with convalescent plasma are needed. A pilot study on 10 patients with severe COVID-19 showed that the tolerance is good and clinical symptoms improved with the increase of oxyhemoglobin saturation after a single dose of 200 mL convalescent plasma transfusion (K. Duan et al., 2020). The advantages of convalescent plasma include potencial clinical efficacy, easier accessibility from a large donor pool, prophylactic benefits for healthcare workers, short-time (Casadevall & Pirofski, 2020), and low-cost over some experimental antivirals (Leider, Brunker, & Ness, 2010). However, there are risks of passive administration of convalescent plasma, including identification of ideal donors due to the lack of widely available and validated SARS-CoV-2 antibody assays, finding donors with a robust humoral response, consenting, collecting, and testing donors (Arabi et al., 2016; Park et al., 2015; Sullivan & Roback, 2020). There are known risks concerning blood substances transferation. One among the risks is that convalescent sera administration could imbue individuals with pulmonary disease, which would cause plasma infusion and pose certain risks for transfusion-related acute lung injury (TRALI) (Gajic et al., 2007). The phenomenon of antibody-dependent enhancement of infection (ADE) is another theoretical risk. Evidence from 245 COVID-19 patients who take the treatment of convalescent plasma suggests that it is safe (Viswanathan et al., 2020). Therefore, the advantages and disadvantages of convalescent plasma therapy must be weighed through the data in the literature review and specific patient situation.