There have been questions whether humans will develop immunity against SARS-CoV-2, the virus which causes the disease, COVID-19. This question is critical for vaccine developers. Recently, good news came from several immunologists around the world that once our bodies encounter the virus, a protective response to the virus can be achieved.
There are different cell types in our immune system that spring to action when a particular type of virus infects humans. Among these, B-cells produce antibodies, the proteins that bind specifically to the proteins on the outer surface of the virus. T-cells circulate in our bodies to find and kill virus-infected cells. Such B- and T-cells against a particular virus can be stored for later use when re-infection by the same virus occurs in the future. These memory functions are the hallmarks of lasting immunity and the basis for developing vaccines.
The good news is that antibodies to COVID-19 have been found in the blood of people who tested positive for SARS-CoV-21. Moreover, neutralizing antibodies which get in between the virus and the target cells to block the entry of the virus have also been identified2. Furthermore, T-cells were detected in recovering COVID-19 patients3.
Researchers also found long lasting memory T-cells against SARS-CoV-2 in patients who recovered from SARS, which caused a pandemic 17 years ago3. This shows the existence of T-cells with common reactivity to viruses of SARS and COVID-19 in these individuals. In addition, blood collected before the 2019 pandemic from uninfected people contained T-cells against SARS-CoV-23,4. Scientists showed that the reactivity of T-cells was against the parts shared with the common cold viruses. Both SARS and cold viruses are in the coronavirus family as is SARS-CoV-2. This finding may explain in part why some people have mild or no symptoms (protected by antibodies to other corona viruses).
In conclusion, these studies are promising since they show that lasting immune defence can be generated in the general population against SARS-CoV-2 with the help of a potent vaccine before any encounter by the real virus that causes COVID-19 disease with potentially deadly consequences.
- 1. Long, Q.X., Liu, B.Z., Deng, H.J., Wu, G.C., Deng, K., Chen, Y.K., Liao, P., Qiu, J.F., Lin, Y., Cai, X.F., et al. (2020). Antibody responses to SARS-CoV-2 in patients with COVID-19. Nat Med 26, 845-848.
- 2. Ju, B., Zhang, Q., Ge, J., Wang, R., Sun, J., Ge, X., Yu, J., Shan, S., Zhou, B., Song, S., et al. (2020). Human neutralizing antibodies elicited by SARS-CoV-2 infection. Nature 584, 115-119.
- 3. Le Bert, N., Tan, A.T., Kunasegaran, K., Tham, C.Y.L., Hafezi, M., Chia, A., Chng, M.H.Y., Lin, M., Tan, N., Linster, M., et al. (2020). SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls. Nature 584, 457-462.
- 4. Mateus, J., Grifoni, A., Tarke, A., Sidney, J., Ramirez, S.I., Dan, J.M., Burger, Z.C., Rawlings, S.A., Smith, D.M., Phillips, E., et al. (2020). Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans. Science.