The hyperimmune plasma is the plasma obtained from people with a high amount of antibodies (hyperimmune immunoglobulins) against a specific microorganism or antigen (substance recognized by the immune system that causes the formation of antibodies). It is present in people subjected to vaccination against the specific microorganism or convalescing from the disease it causes.
Typical hyperimmune immunoglobulins are those towards tetanus, towards some viruses or towards the antigens present on the red blood cell membrane (Rh factor). In the latter case they determine thematernal-fetal incompatibility, a complication of pregnancy that occurs when the fetus's blood type is incompatible with that of the mother.
The hyperimmune immunoglobulins they carry out their protective action through effects that neutralize or make any toxins, viruses or bacteria visible to the immune system.
Antiviral immunity is mainly linked to the action of antibodies that neutralize the infectious capacity of the virus, preventing its entry into the target cell.
Hyperimmune plasma therapy has been used extensively in the past for the treatment of numerous infectious diseases. In 1890, Emil Adolf von Behring and Shibasaburo Kitasato to treat diphtheria and tetanus exploited passive immunity, obtained with the serum of healthy animals exposed to the infection. Since then, the treatment with hyperimmune serum has been used successfully for the treatment of a a range of diseases, including rheumatic fever, scarlet fever, mumps, measles, chicken pox, and pneumococcal and meningococcal infections.
Over the years, the use of plasma from convalescent people has been significantly increased, especially in the course of epidemics caused by emerging viruses.
The first application of hyperimmune plasma therapy took place between 1918 and 1920 during the pandemic caused by the Spanish flu virus (H1N1). This use was renewed in 1976 during the Ebola virus epidemic in the Democratic Republic of the Congo and, in 1979, in people with the Argentine hemorrhagic fever virus. In the following decades, hyperimmune plasma therapy was used successfully during the swine flu (H1N1) pandemic in 2009, during the avian flu (H5N1) outbreak in 2003 and during the Ebola outbreak in West Africa in 2013. .
Plasma taken from convalescent people was also used in the two previous SARS-CoV epidemics, in 2003, and MERS, in 2012, to treat people affected by the two viruses with good clinical results.
In the light of previous experiences, the use of plasma from convalescent people has also been tested during the current SARS-CoV-2 epidemic. The clinical studies conducted to date, however, do not report clear evidence on its therapeutic efficacy.Bibliography
Montelongo-Jauregui D, Vila T, Sultan A, Jabra-Rizk M. Convalescent serum therapy for COVID-19: A 19th century remedy for a 21st century disease. PLoS Pathogens. 2020; 16: e1008735
Al-Omari A. MERS coronavirus outbreak: Implications for emerging viral infections. Diagnostic microbiology and infectious disease. 2019; 93: 265–285In-depth link
National Order of Biologists. Delegation of Puglia and Basilicata. Immunoprophylaxis and hyperimmune plasma: the state of the art at the time of Covid
National Blood Center. Hyperimmune plasma: what it is for and how to donate it
Ministry of Health. Donate blood. Questions and Answers - FAQ