Research roadmap for coronavirus vaccine development

• Identification of the appropriate vector for different animal species to express animal coronavirus antigens to develop vaccines

• Appropriate vector: Several viral vectors have successfully been used in the past for various viruses to develop vaccines (e.g., paramyxoviruses, canarypox, adenoviruses, VSV [summarised in 7]), but understanding which vector would be most suitable for the target antigen is also important e.g., do the viral vectors have the same route of entry and replication?
• Immunity: Viral vectored vaccines are effective at generating cellular immune responses, but this may come at the expense of a strong antibody response. Therefore, understanding the CoP for an animal coronavirus is important, and how both the humoral and cellular immune response can be maximized. Also, whether boosters will be required
• Contraindications: Does the viral vector itself induce any immune response in the host? Is there any pre-existing immunity in the host against the suggested vector that may mean it is ineffective at delivering the target antigen?
• Production: What is the efficiency of the production methods? How expensive are viral vectors compared to recombinant proteins? Do you want to use a non-replicating or replicating vector?

• Cost: Could bivalent vaccines be produced that cover multiple animal pathogens, and that make the vaccine more cost effective and favourable to vets/farmers etc. for immunisation of their animals?
• Targeted modulation of viruses: Either by targeting host factors (cellular factors and pathways that are essential for the virus to survive) or by targeting the virus itself by developing compounds that selectively bind to the virus capsid – ensure vector is safe for use in animals

• Routes of administration: Which route of administration will deliver the most robust immune response? Will one route hinder the effectiveness of a vector?
• Vector biology: Understanding the route of entry and replication of the vector, and mechanisms of action that would then impact the immune response triggered when used as a vaccine delivery system

Imbokodo phase II/b HIV vaccine clinical trial (ClinicalTrials.gov Identifier: NCT03060629) ChAdOx1 for SARS-CoV-2, MERS-CoV VSV for SARS