Development and pre-clinical evaluation of Newcastle disease virus-vectored SARS-CoV-2 intranasal vaccine candidate

Abstract

The COVID-19 pandemic has claimed the lives of millions of people worldwide and threatens to become an endemic problem, therefore the need for as many types of vaccines as possible is of high importance. Because of the millions of doses required, it is desirable that vaccines are not only safe and effective, but also easy to administer, store, and inexpensive to produce. Newcastle Disease Virus (NDV) is responsible for a respiratory disease in chickens. It has no pathogenic homologue in humans. NDV is recognized as an oncolytic virus, and its use in humans for oncological treatment is being evaluated. In the present work, we have developed two types of NDV-vectored candidate vaccines, which carry the surface-exposed RBD and S1 antigens of SARS-CoV-2, respectively. These vaccine candidates were produced in specific-pathogen-free embryonating chicken eggs, and purified from allantoic fluid before lyophilization. These vaccines were administered intranasally to three different animal models: mice, rats and hamsters, and evaluated for safety, toxicity, immunogenicity, stability and efficacy. Efficacy was evaluated in a challenge assay against active SARS-CoV-2 virus in the Golden Syrian hamster model. The NDV-vectored vaccine based on the S1 antigen was shown to be safe and highly immunogenic, with the ability to neutralize SARS-CoV-2 in-vitro, even with an extreme dilution of 1/640. Our results reveal that this vaccine candidate protects the lungs of the animals, preventing cellular damage in this tissue. In addition, this vaccine reduces the viral load in the lungs, suggesting that it may significantly reduce the likelihood of transmission. Being lyophilized, this vaccine candidate is very stable and can be stored for several months at 4-8°C. In conclusion, our NDV-based vaccine candidate has shown a very favorable performance in the pre-clinical study, serving as evidence for a future evaluation in a Phase-I human clinical trial. This candidate represents a promising tool in the fight against COVID-19.

A recombinant SARS-CoV-2 RBD antigen expressed in insect cells elicits immunogenicity and confirms safety in animal models

“…The membranes were blocked with 5% (w/v) non-fat milk in PBS with 0.1% of Tween 20 at pH 7.4 and incubated overnight at room temperature. Then, membranes were washed three times for 5 minutes each with Tris-buffered saline containing 0.1% (v/v) Tween 20 (TBS-T) and incubated for two hours at room temperature with serum of a hamster immunized with a New Castle disease virus expressing the S1 sub-unit of SARS-CoV-2 [19] (1:250) in 5% non-fat milk. After three washes with TBS-T, anti-Hamster IgG antibody conjugated to HRP (Abcam, USA) was added to the membrane at 1:5000 dilution in 5% non-fat milk and incubated for two hours at room temperature.…”

“…The importance of disulfide bonds for the correct folding of the RBD sub-domain is known. Therefore, an additional way to verify the correct folding of the recombinant RBD was evaluating its detection under reducing and non-reducing conditions using a serum from a hamster immunized with a New Castle Disease virus (NDV) expressing the S1 Domain [19] (Fig 4B). In this way, by Western blot RBD could be detected by the serum only under non-reducing conditions, demonstrating that it conserves the folding of the RBD sub-domain occurring in the Spike protein.…”