MMR Vaccine and COVID-19: Measles Protein Homology May Contribute to Cross-Reactivity or to Complement Activation Protection
Е. С. Маракасова, Ancha Baranova
Abstract
A recently published study by Jeffrey E. Gold et al. (1) presents data that strongly suggest that measles-mumps-rubella (MMR) vaccination negatively correlates with the severity of coronavirus disease 2019 (COVID-19)-related symptoms. Another study by Alba Grifoni et al. (2) demonstrated that antibody titers to spike protein in some unexposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) subjects may reach substantial levels, thus suggesting preexisting immunity to the coronavirus. This preexisting immunity may be due to the cross-reactivity with other antigens, for example the ones resulting from previous immunizations. Other studies reported that COVID-19 mortality is higher in countries where Mycobacterium bovis BCG vaccination is not routinely administered (3). Why previously received MMR vaccine may aid in reducing the severity of coronavirus infection symptoms is not clear, but it is tempting to speculate that one or more of the MMR components may be structurally similar to SARS-CoV epitopes recognized by the immune system and may contribute to cross-immunity. Hence, we performed homology analysis between the receptor binding domain (RBD) of the spike protein and the nucleocapsid protein of SARS-CoV-2 to measles, mumps, and rubella proteomes using BLAST (4). A similarity between the RBD of the surface glycoprotein of COVID-causing coronavirus and the measles fusion glycoprotein (chain B) was evident (Fig. 1).