Protective Efficacy of Lyophilized Vesicular Stomatitis Virus-Based Vaccines in Animal Model

Abstract

We evaluated the in vitro effects of lyophilization for 2 vesicular stomatitis virus-based vaccines by using 3 stabilizing formulations and demonstrated protective immunity of lyophilized/reconstituted vaccine in guinea pigs. Lyophilization increased stability of the vaccines, but specific vesicular stomatitis virus-based vaccines will each require extensive analysis to optimize stabilizing formulations.

Keywords: Ebola virus; Lassa virus; animal models; glycoproteins; guinea pigs; lyophilized; vaccines; vesicular stomatitis virus; viruses; zoonoses.

Figure 1

Vaccine recovery after lyophilization in study of protective efficacy of lyophilized vesicular stomatitis virus–based vaccines in animal model. A) VSV∆G/LASVGPC vaccine stored at 4°C; B) VSV∆G/EBOVGP vaccine stored at 4°C; C) VSV∆G/LASVGPC vaccine stored at 21°C; D) VSV∆G/EBOVGP vaccine stored at 21°C; E) VSV∆G/LASVGPC vaccine stored at 21°C; F) VSV∆G/EBOVGP vaccine stored at 21°C. VSV∆G/LASVGPC or VSV∆G/EBOVGP vaccines were lyophilized in DMEM containing no excipients or containing combinations of 5% lactalbumin hydrolysate, 10% sucrose, 5% trehalose, or 0.5% gelatin and stored at different temperatures. At the specified time points, vaccines were resuspended in triplicate in normal saline, titered by using standard tissue culture techniques, and the median TCID₅₀ was calculated for each. p values are indicated above brackets. Errors bars are SDs. DMEM, Dulbecco modified Eagle medium; G, gelatin; LS, lactalbumin hydrolysate and sucrose; NC, not calculated; T, trehalose; TCID₅₀, 50% tissue culture infectious dose; VSV-Lassa, vesicular stomatitis virus expressing Lassa virus glycoprotein; VSV-Zebov, vesicular stomatitis virus expressing Ebola virus glycoprotein.

Figure 2

Protective efficacy of lyophilized vesicular stomatitis virus–based vaccines in guinea pig model. A) Body temperatures; B) weight changes; C) survival; D) virus titrations in different tissues. Groups of 10 Hartley guinea pigs each were immunized with VSV∆G/LASVGPC vaccine or lyophilized/reconstituted Ly-VSV∆G/LASVGPC or Ly-VSV∆G/EBOVGP. Ly-VSV∆G/EBOVGP was used as the sham-vaccinated inoculum control group. Animals were challenged 28 days after immunization with a lethal dose of guinea pig–adapted Lassa virus Josiah strain. Disease progression was monitored in 6 animals in each group; the remaining 4 animals per group were euthanized on day 13 postinfection for analysis of infectious Lassa virus in tissues. LOD, limit of detection; Ly-VSV∆G/EBOVGP, lyophilized vesicular stomatitis virus expressing Ebola virus glycoprotein; Ly-VSV∆G/LASVGPC, lyophilized vesicular stomatitis virus expressing Lassa virus glycoprotein; TCID₅₀, 50% tissue culture infectious dose; VSV∆G/LASVGPC, vesicular stomatitis virus expressing Lassa virus glycoprotein.