A single-dose amber codon carrying live attenuated vaccine elicits pan-sarbecovirus immunity and blocks SARS-CoV-2 transmission

New publication in npj Vaccines from C2i's Managing Director Professor Leo Poon's team describing an innovative approach to developing a live attenuated SARS-CoV-2 vaccine candidate.

The study demonstrates a novel approach to engineering a highly attenuated yet fully immunogenic SARS-CoV-2 vaccine candidate, showing:

• Near-sterile immunity in mice under stringent challenge conditions

• Broad protection against antigenically distinct variants and even SARS-CoV

• Complete block of onward transmission to naïve animals following challenge

• Strong mucosal and systemic antibody responses after a single intranasal dose

These findings highlight the potential of whole-virus vaccine platforms for preparedness against current and future threats.

Abstract

Existing COVID-19 vaccines exhibit clear limitations against the continuous emergence of variants of concern (VoCs), as their efficacy is challenged by the cumulative mutations in the spike or its RBD, which is the primary antigenic target. In addition, the intramuscular route of administration is suboptimal for inducing robust mucosal immunity, which is an important factor for preventing infection and transmission in the respiratory tract. To overcome these hurdles, we developed a live attenuated mucosal vaccine by introducing amber stop codons into the accessory genome of SARS-CoV-2, resulting in a highly attenuated yet immunogenic phenotype. A single intranasal vaccination induced broad-spectrum neutralizing antibodies against diverse VoCs. A single dose of this live attenuated vaccine can confer near-sterile immunity in mice against a greater than tenfold lethal SARS-CoV-2 challenge, eliciting high levels of both mucosal and systemic antibodies. Critically, vaccine-mediated protection also extended to antigenetically distinct VoCs and even SARS-CoV. Furthermore, vaccinated and subsequently challenged cohorts failed to transmit the virus to naïve animals, demonstrating a complete block of onward transmission. These findings establish our candidate as a true pan-sarbecovirus mucosal vaccine, offering a promising strategy to provide broad immunity and will likely defend against future sarbecovirus-driven pandemics.

>>> A single-dose amber codon carrying live attenuated vaccine elicits pan-sarbecovirus immunity and blocks SARS-CoV-2 transmission