Turk J Immunol. 2022; 10(3): 134-148 | DOI: 10.4274/tji.galenos.2022.55264

The Rationale Behind the Effectiveness of COVID-19 Vaccines and Associated Immunological Mechanisms

Sami El Khatib
Lebanese International University, Department of Biomedical Sciences, Beirut, Lebanon

The basic concept of vaccination has been based on engendering an adaptive immune response armed with effective immune cells, memory cells, and cytokines. These elements cooperate to mount either a humoral or a cell-mediated response. Coronavirus disease-2019 vaccines, although diversified, adapted the same objective with the previous vaccines prepared since Edward Jenner’s work. The spike surface protein (S) and the receptor binding domain constituted the main antigenic determinants for which the binding antibodies as well as the neutralizing antibodies were secreted. The unprecedented use of mRNA vaccines represented an unmatched breakthrough, which paved the road for a new era of vaccine generation. They showed a substantial ability to elicit antibody secretion with a moderate helper T cell response just after inoculation of the first dose. Besides, the adenoviruses-shuttled vaccines were able to engender a spectrum of polyclonal antibodies including neutralizing antibodies apt to drive a multitude of antibodies-mediated functions and activate T cell immune responses. In either case, the antibody titers as well as lymphocytes-mediated responses were significantly intensified. Deciphering the mechanisms of immune response activation by the inoculated vaccines in addition to the elaboration of innate elements involvement should open the door for a better decryption of the induced immune protection and pave the road for the formulation of a more effective vaccine that surmounts the incessant mutational variation of the viral antigenic attributes.

Keywords: SARS-CoV-2 vaccines, mRNA vaccines, adenovirus-shuttled vaccine, whole-virion inactivated vaccine, protein subunit vaccine, spike protein, receptor binding protein

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COVID-19 Aþýlarýnýn Etkililiðinin ve Ýliþkili Ýmmünolojik Mekanizmalarýn Arkasýndaki Gerekçe

Sami El Khatib
Lebanese International University, Department of Biomedical Sciences, Beirut, Lebanon

Aþýlamanýn temel konsepti, etkili baðýþýklýk hücreleri, bellek hücreleri ve sitokinlerle donanmýþ adaptif bir baðýþýklýk tepkisi oluþturmaya dayanmaktadýr. Bu ögeler, bir hümoral ya da hücre aracýlý bir tepki oluþturmak için iþ birliði yaparlar. Koronavirüs hastalýðý-2019 aþýlarýnda, çeþitlendirilmiþ olmasýna raðmen, Edwards Jenner’ýn çalýþmasýndan bu yana hazýrlanan önceki aþýlarla ayný amaç benimsenmiþtir. Spike yüzey proteini (S) ve reseptör baðlanma alaný, nötralize edici antikorlarýn yaný sýra baðlayýcý antikorlarýn salgýlandýðý ana antijenik belirleyicileri oluþturmuþlardýr. mRNA aþýlarýnýn benzeri görülmemiþ kullanýmý, yeni bir aþý üretimi çaðýnýn yolunu açan eþsiz bir baþlangýcý temsil etmiþtir. Ýlk dozun uygulanmasýndan hemen sonra orta derecede yardýmcý T hücre yanýtý ile antikor sekresyon yeteneði gözlenmiþtir. Ayrýca, adenovirüs-shuttle aþýlar, çok sayýda antikor aracýlý iþlevi yürütmeye ve T hücrelerinin baðýþýklýk tepkilerini aktive etmeye uygun nötralize edici antikorlar da dahil olmak üzere bir poliklonal antikor spektrumu oluþturabilmiþtir. Her iki durumda da lenfositlerin aracýlýk ettiði tepkilerin yaný sýra antikor titreleri de önemli ölçüde yoðunlaþmýþtýr. Doðuþtan gelen unsurlarýn ayrýntýlandýrýlmasýna ek olarak inoküle aþýlar tarafýndan baðýþýklýk tepkilerinin aktivasyon mekanizmalarýnýn deþifre edilmesi, indüklenen baðýþýklýk korumasýnýn daha iyi bir þekilde çözülmesinin ve viral antijenik özelliklerin sürekli mutasyonel varyasyonunun üstesinden gelen daha etkili bir aþý formülasyonunun yolunu açmalýdýr.

Anahtar Kelimeler: SARS-CoV-2 aþýlarý, mRNA aþýlarý, adenovirüs-shuttle aþý, whole-virion inaktive aþý, protein altbirim aþýsý, spike proteini, reseptör baðlayýcý protein

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