Rescue of recombinant Newcastle disease virus: a promising vector with two decades of intensive vaccine research

An overview of current COVID-19 vaccine platforms

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic that emerged in December 2019 in Wuhan city, China. An effective vaccine is urgently needed to protect humans and to mitigate the economic and societal impacts of the pandemic. Despite standard vaccine development usually requiring an extensive process and taking several years to complete all clinical phases, there are currently 184 vaccine candidates in pre-clinical testing and another 88 vaccine candidates in clinical phases based on different vaccine platforms as of April 13, 2021. Moreover, three vaccine candidates have recently been granted an Emergency Use Authorization by the United States Food and Drug Administration (for Pfizer/BioNtech, Moderna mRNA vaccines, and Johnson and Johnson viral vector vaccine) and by the UK government (for University of Oxford/AstraZeneca viral vector vaccine). Here we aim to briefly address the current advances in reverse genetics system of SARS-CoV-2 and the use of this in development of SARS-CoV-2 vaccines. Additionally, we cover the essential points concerning the different platforms of current SARS-CoV-2 vaccine candidates and the advantages and drawbacks of these platforms. We also assess recommendations for controlling the COVID-19 pandemic and future pandemics using the benefits of genetic engineering technology to design effective vaccines against emerging and re-emerging viral diseases with zoonotic and/or pandemic potential.

Complete genome sequence of a subgenotype XXI.1.1 pigeon paramyxovirus type 1 virus (PPMV‑1) isolated from Iran in 2018 and phylogenetic analysis of a possible novel, but unassigned, PPMV-1 group isolated in 2014

Newcastle disease (ND) is one of the most serious infectious and contagious viral diseases in avian species. Recently, several ND outbreaks in pigeon caused by pigeon paramyxovirus serotype-1 (PPMV-1) have been reported from Iran, but unfortunately, phylogenetic studies have been mostly conducted on partial sequence of NDV fusion (F) gene. In addition, a complete genome data of Iranian PPMV-1 strains are not available. In the present study, a PPMV-1, named Avian avulavirus 1/pigeon/Iran/UT-EGV/2018, isolated from an infected pigeon, was subjected to whole-genome sequencing. The isolate showed an MDT of 74 h, thus categorizing it as mesogenic. The phylogenetic analysis based on the F gene sequence revealed the isolate belongs to XXI.1.1 subgenotype (min 0.9 % and max 3 %). To our knowledge, our study is the first study to publish the complete genome of a PPMV-1 from Iran. According to BLAST results, the whole genome of UT-EGV had high homology with some Russian, Egyptian and Ukrainian strains (the highest was 96.55 %). Additionally, we conducted a phylogenetic analysis on five PPMV-1 that we isolated in 2014 to find that they may belong to a completely unreported subgenotype (6 % distance when compared as a group). The information obtained from this study can be useful in preventive measures, including constructing an effective vaccine against PPMV-1 in Iran.

Rapid Development of an Effective Newcastle Disease Virus Vaccine Candidate by Attenuation of a Genotype VII Velogenic Isolate Using a Simple Infectious Cloning System

Genotype-matched vaccines provide ideal protection against infection caused by new Newcastle disease virus (NDV) genotypes or variants even in the vaccinated chickens. In this study, we report a protocol for attenuation and rapid development of a velogenic NDV isolate as an effective vaccine candidate, using a simple and reliable infectious cloning platform. Based on DHN3, a genotype VII velogenic NDV isolate, recombinant rDHN3 was rescued by co-transfection of plasmids expressing the genomic RNA, NDV proteins NP, P and L, and the T7 polymerase without using a helper virus. Subsequently, an attenuated strain rDHN3-mF was produced by substitution of residues from amino acids 112 to 117 in the DHN3 F protein with the corresponding sequence from the LaSota strain. Both rDHN3 and rDHN3-mF are genetically stable during propagation in cell culture and chicken embryos. Further characterization through determination of EID₅₀, MDT and clinical assessments confirmed that rDHN3 is velogenic and rDHN3-mF lentogenic. Vaccination of one-week-old SPF chicks with inactivated rDHN3-mF produced much higher anti-DHN3 antibody response and better protection against live DHN3 challenge than did the commercial LaSota vaccine, providing 100% protection and much earlier viral clearance. This attenuated NDV isolate would merit further development into a vaccine product.