Recombinant Albumin for Stabilization of Live-Attenuated Viral Vaccines

Published on 16 April 2019

Enhanced liquid-phase stability of live-attenuated Flavivirus vaccines using recombinant albumin

The single-stranded RNA viruses belonging to the genus Flavivirus (family, Flaviviridae) are significant to global public health due to the high rates of morbidity and mortality they cause.¹ For example, Yellow Fever sickens approximately 200,000 people and kills 30,000 annually.² Other viruses belonging to this genus include the mosquito-borne diseases Dengue Fever, Japanese encephalitis, West Nile virus, and Zika virus, and the tick-borne diseases Tick-borne Encephalitis, Kyasanur Forest Disease, Alkhurma disease, and Omsk hemorrhagic fever.

Vaccination strategies for flaviviruses like Yellow Fever and Japanese encephalitis commonly rely on use of live-attenuated viruses (LAV), whereby a modified version of the target virus is produced that can infect the host and express its full complement of viral antigens, but not cause clinically significant disease. The host, in turn, mounts a comprehensive immune response against the LAV, which confers long-term resistance against the target virus.

Technical obstacles to Flavivirus LAVs

While a number of LAV vaccines have successfully been developed against Flaviviruses, some have proven to be highly labile in liquid at ambient temperatures, compromising their viability during transportation and storage. The LAV for Yellow Fever virus, for example, is stable for only one hour on ice after the lyophilized LAV is reconstituted in liquid for injection, severely limiting its utility in developing countries.

A variety of stabilizers, including sugars, proteins, and polymers, have been evaluated for their ability to improve the stability of LAV vaccines. In a paper published in the journal Vaccine, Wiggan et al tested a panel of stabilizers, individually and in combination, for their ability to improve thermal stability of a DEN-2 PDK-53 chimeric LAV against Dengue Fever.³

Recombinant albumin derived from InVitria acts synergistically with other excipients to stabilize liquid-phase LAVs.

Excipients tested by Wiggan at al included block copolymers F127, F68, P85 and P123; blood derived human serum albumin (HSA) and bovine serum albumin; the polysaccharides chitosan, trehalose, sucrose, and lactose; detergents Tween-20 and Tween-80; and DEAE-β-cyclodextran 0.5–5%. They also tested two forms of recombinant albumin (rHSA); one sourced from InVitria and currently marketed as Exbumin and the other from a yeast background.

LAV vaccine stabilization by the individual excipients 15% trehalose, 2% F127, 1% rHSA (InVitria), and 0.05% chitosan was detectable but minimal, whereas others had no beneficial effect at all. In combination, trehalose, F-127, and rHSA (InVitria) conferred the greatest amount of stability (32.7 to 45.3% viral survival after 21 hours at 37°C). The authors noted that the effect was synergistic, in that the ability of these three components to stabilize the LAV vaccine was greater than the sum of the individual components’ thermal stabilizing properties. The authors further tested the efficacy and safety of the Dengue Fever LAV vaccine formulation in mice and found that all excipients were well tolerated, and that all vaccinated animals seroconverted either after first vaccine challenge or the first booster.

InVitria’s Exbumin recombinant HSA is a useful reagent for stabilizing virus expressed in vitro for research and manufacturing use as a formulation excipient in GMP-manufactured vaccine formulations.

For more information about use of InVitria’s Exbumin recombinant HSA in the production and formulation of virus, please refer to the Application Note: Stabilizing Virus with Albumin to Improve Yield, and stay tuned for future updates.