ANTIBODY RESPONSES

• Antibody binding increased rapidly after first vaccination, and dose-dependent responses were evident

NEUTRALIZATION RESPONSES

• PsVNA (lentivirus reporter single-round-of-infection neutralization assay) was used to determine the presence of vaccine-induced neutralizing activity. This procedure basically identifies the presence of neutralizing antibodies.
• After the first vaccination, PsVNA was detected in less than half of the participants. However, after the second vaccination PsVNA was identified in all participants, with the lowest responses being from the 25-μg group, and the higher responses in the 100-μg and 250-μg groups. Both the 100-μg and 250-μg groups were similar in magnitude.
• Live wild-type SARS-CoV-2 PRNT (plaque-reduction neutralization testing) was also used to identify the efficiency of the neutralizing antibodies to prevent viral activity. At day 43, “wild-type virus–neutralizing activity was capable of reducing SARS-CoV-2 infectivity by 80% or more” and before the vaccination, “no participant had 80% detectable live-virus neutralization” even at the highest concentration tested.

T-CELL RESPONSES

• The 25-ug and 100-ug doses elicited CD4 T-cell responses as expected after the first vaccination.
• CD8 T-cell responses were detected at low levels after the second vaccination in the 100-ug dose group.