Inactivated and mRNA vaccines trigger distinct populations of immune cells when administered.
Unlike mRNA vaccines, which induce a SARS-CoV-2-spike-specific immune response in two key types of immune cells, namely T cells that remove infected cells and B cells that trigger an antibody response, the inactivated vaccines elicited a broader immune response targeting different proteins from the virus but in T cells only, reported Professor Antonio Bertoletti and his team from Duke-NUS’ Emerging Infectious Diseases Programme in Cell Reports Medicine.
“mRNA vaccines induced a strong T- and B-cell response against the spike protein. However, inactivated vaccines elicit a T-cell response against different viral proteins. The combination of membrane, nucleoprotein and spike-specific T-cell response is quantitatively comparable to the sole spike T-cell response induced by the mRNA vaccine. It also effectively tolerates the mutations characterising the Omicron lineage,” explained Ms Joey Lim, a second-year PhD student from Bertoletti’s lab in a statement.
“Since inactivated SARS-CoV-2 vaccines can generate T-cell responses towards other viral proteins, this more heterogenous response could be beneficial, in comparison to the current spike targeting strategy of other vaccines,” added Bertoletti.
However, the inactivated virus vaccines also did not stimulate cytotoxic CD8 T cells which kill and clear virus-infected cells in the body. Instead, only CD4 T helper cells that recruit other immune cells to clear an infection were found to be activated.
“Larger studies are needed to clarify the impact of these T-cell responses in SARS-CoV-2 infection to better design vaccines for controlling severe COVID-19 after infection by Omicron or future variants,” concluded Bertoletti.