BBV152

BBV152 vaccine formulations generated significantly high antigen-binding and neutralizing antibody titers

The candidate vaccine elicited potent humoral immune response in a Syrian hamster model. In a SARS-CoV-2 challenge, the hamsters were protected from pneumonia and had shortened time to lower respiratory tract viral clearance.

In the participants of the phase I study, neutralising antibody response was still present 3 months after the second dose administration. In the phase II study, the individuals vaccinated with 6 μg doses adjuvanted with Algel-IMDG had higher neutralizing antibody titres and seroconversion rates compared to the “3 μg” group. The T cell response in the vaccinated subjects was Th1-biased. The solicited adverse events were mild of moderate, the vaccine was generally well tolerated. Sample size: 184 (“3 μg” group) + 177 (“6 μg” group). Dosage: 2 doses 28 days apart (3 μg each, with Algel-IMDG (phase I and II); 6 μg each, with Algel-IMDG (phase I and II); or 6 μg each, with Algel (phase I) (+ Algel-only control in phase I)). Primary outcomes: Neutralising antibody titres and seroconversion rates at 4 weeks post second dose (phase II).

No serious (only temporary mild and moderate) adverse events causally associated with the vaccine were noted. The vaccination elicited anti-Spike, RBD, and Nucleocapsid IgG responses which were Th1 biased. After the second dose, seroconversion (MNT50) was observed in 82.8% (6 μg Algel (alum) group) to 91.2% (6 μg Algel-IMDG group).  Seroconversion (PRNT50) ranged from 86.4% (6 μg Algel-IMDG group) to 93.4% (3 μg Algel-IMDG group). In some of the Algel-IMDG group patients' blood samples but almost none of the Algel/Algel control group samples there were CD3+, CD4+, and CD8+ T-cell responses (with IFN-γ) observed. Sample size: 99 (3 μg Algel-IMDG group) + 99 (6 μg Algel-IMDG) + 93 (6 μg Algel) + 73 control. Dosage: Two IM doses of 3 μg with Algel-IMDG or 6 μg with Algel-IMDG, or 6 μg with Algel 14 days apart. Endpoints: Safety (primary outcome), seroconversion, and cell-mediated responses.

The best outcomes were observed in animals vaccinated with 3 μg doses (adjuvanted with Algel 2) (“group III”). SARS-CoV-2-challenged (14 days after the second vaccine dose) rhesus macaques were protected from interstitial pneumonia. By day 7 post viral challenge, viral genomic RNA was detectable in none of the vaccinated animals. No clinical or radiographic abnormalities were observed in animals from the group III. RBD-specific IgGs were detectable in the vaccinated macaques from the third week after the first immunization and were high at 28th day after immunization and 7th day post viral challenge. The presence of neutralizing antibodies positively correlated with the IgGs. Compared to placebo, significantly lower levels of IL-6 and higher levels of IL-8 were observed in group III.

In vitro, the sera of individuals vaccinated with two doses of the vaccine (collected 4 weeks after the second dose) potently neutralized a SARS-CoV-2 strain carrying the B.1.1.7 hallmark mutations.