A third dose of the unmodified COVID-19 mRNA vaccine CVnCoV enhances quality and quantity of immune responses.

Lenart K, Hellgren F, Ols S, Yan X, Cagigi A, Cerveira RA, Winge I, Hanczak J, Mueller SO, Jasny E, Schwendt K, Rauch S, Petsch B, Loré K

Mol Ther Methods Clin Dev 27 (-) 309-323 [2022-12-08; online 2022-10-06]

A third vaccine dose is often required to achieve potent, long-lasting immune responses. We investigated the effect of three 8-μg doses of CVnCoV, CureVac's severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine candidate containing sequence-optimized unmodified mRNA encoding the spike (S) glycoprotein, administered at 0, 4, and 28 weeks, on immune responses in rhesus macaques. After the third dose, S-specific binding and neutralizing antibodies increased 50-fold compared with post-dose 2 levels, with increased responses also evident in the lower airways and against the SARS-CoV-2 B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta) variants. Enhanced binding affinity of serum antibodies after the third dose correlated with higher somatic hypermutation in S-specific B cells, corresponding with improved binding properties of monoclonal antibodies expressed from isolated B cells. Administration of low-dose mRNA led to fewer cells expressing antigen in vivo at the injection site and in the draining lymph nodes compared with a 10-fold higher dose, possibly reducing engagement of precursor cells with the antigen and resulting in the suboptimal response observed after two-dose vaccination schedules in phase IIb/III clinical trials of CVnCoV. However, when immune memory is established, a third dose efficiently boosts the immunological responses and improves antibody affinity and breadth.

Affinity Proteomics Stockholm [Service]

Affinity Proteomics Uppsala [Service]

PubMed 36217434

DOI 10.1016/j.omtm.2022.10.001

Crossref 10.1016/j.omtm.2022.10.001

pmc: PMC9535876
pii: S2329-0501(22)00143-7