Recombinant Virus Platforms are Out in Front in the Race to Develop Vaccines Against SARS-CoV-2 and COVID-19 Disease

Published on 12 June 2020

SARS-CoV-2 continues to circulate the globe, causing widespread illness, loss of life , and far-reaching societal and economic disruption. Public health measures like stay-at-home and safer-at-home have been successful in checking the virus’s geometric growth curve, and treatments are in development. However, epidemiologists generally agree that achieving “herd immunity” through a safe and effective vaccine is indispensable to overcoming this challenge to humanity’s social, mental, and economic health and wellbeing.

The development of vaccines under such urgent circumstances faces monumental scientific, technical, ethical, and political challenges from start to finish. Accordingly, the world’s governments are pouring enormous resources into parallel efforts to overcome barriers to rapid vaccine design, validation, clinical testing, production, and distribution.

In the US, for example, the $13 billion Operation Warp Speed (OWS) initiative has identified five programs for fast-track development, including candidates from AstraZeneca and Oxford University, Johnson & Johnson, Merck, Moderna, and Pfizer and BioNTech.

Merck’s approach is of particular interest because it leverages the same platform behind ERVEBO, a vaccine the company launched in response to the worst outbreak of Ebola virus  in history.

ERVEBO is an attenuated, replication-competent, recombinant vesicular stomatitis virus  (rVSV) in which the VSV surface glycoprotein has been replaced with one from the Ebola virus. In humans, the ERVEBO vaccine replicates within the body, producing non-virulent viral particles that present the Ebola surface glycoproteins and elicit a neutralizing immune response. While ERVEBO was not available soon enough to prevent 28,600 Ebola cases, 11,325 deaths, and a terrifying spread beyond the borders of the epicenter in Guinea into bordering countries and even Europe and the US, it is now being used as an effective tool for saving lives and managing transmission in more recent Ebola outbreaks.

In addition to the five groups selected by OWS, many other groups in and outside of the US are also working on vaccines to prevent COVID-19 disease. Another example of a virus-based vaccine is a collaboration between UW–Madison, FluGen, and Bharat Biotech. These collaborators are developing CoroFlu, a coronavirus vaccine based on the flu-vaccine candidate M2SR, a self-limiting version of the influenza virus that has been shown to safely elicit an immune response against the flu in human clinical trials.

Live-virus programs like those from Merck and the FluGen collaboration typically rely on large-scale production of recombinant viruses in mammalian cell culture.

One of the most common and preferred cellular substrates for virus production is VERO, an immortalized line of kidney epithelial cells derived from the African green monkey). Current regulatory guidance and Good Manufacturing Practice (GMP) standards for manufacturing of cell-based, advanced therapy medicinal products (ATMPs) state that alternatives to fetal bovine serum should be used in cell culture due to poor reproducibility, safety concerns, and potential disruptions in the supply chain for animal serum.

InVitria has a long history of supporting VERO cell-culture and vaccine studies with safe, pure, and reliable serum-free reagents for research, cell culture, and commercial-scale virus production.

Among our specialty media formulations for cell culture is our OptiVERO product, specifically optimized for VERO-based virus production in both 2D (tissue culture flask) and 3D (microcarrier) culture formats. Because its individual components are produced using a non-mammalian recombinant protein expression system, OptiVERO is considered to be a chemically defined medium, free of blood-derived components, animal components, and plant hyrdosylates that may interfere with safe and reliable production.

In addition to pre-formulated media, InVitria also produces individual cell-culture components and excipients that are routinely used for vaccine research and production.

Examples include Cellastim S, a blood-free, recombinant form of human albumin that has been specifically optimized to enhance mammalian cell performance in animal-free cell-culture media, and Exbumin, an excipient-grade form of blood-free, recombinant human albumin that improves viral stability for vaccines and gene therapies and has been approved for this use by FDA and EMA.

The race to produce a safe and effective vaccine against SARS-CoV-2 is playing out in real time and, no matter which platform is ultimately successful, the unprecedented pace of research promises both to make history, and to generate science that will positively impact public health for generations to come. We’re glad to be able to contribute to the effort and will watch the continued development of virus-based vaccine platforms with great interest.