Adjuvants Differentially Modulate the Immunogenicity of Lassa Virus Glycoprotein Subunits in Mice.

Albert To,Chih-Yun Lai,Michael M Lieberman,Madhuri Namekar,Teri Ann S Wong,Axel T Lehrer

doi:10.3389/fitd.2022.847598

Abstract

Lassa Fever (LF) is an acute viral hemorrhagic fever caused by Lassa virus (LASV) that is primarily transmitted through contact with wild rodents in West Africa. Although several advanced vaccine candidates are progressing through clinical trials, some effective vaccines are virally vectored and thus require a stringent cold-chain, making distribution to rural and resource-poor areas difficult. Recombinant subunit vaccines are advantageous in this aspect as they can be thermostabilized and deployed with minimal storage and transportation requirements. However, antigen dose and adjuvant formulation must be carefully selected to ensure both the appropriate humoral and cell-mediated immune responses are elicited. In this study, we examine the immunogenicity of a two-step immunoaffinity-purified recombinant LASV glycoprotein (GP) with five clinical- and preclinical-grade adjuvants. Swiss Webster mice immunized intramuscularly with 2 or 3 doses of each vaccine formulation showed complete seroconversion and maximal GP-specific antibody response after two immunizations. Formulations with GPI-0100, LiteVax, Montanide™ ISA 51, and Montanide™ ISA 720 induced both IgG1 and IgG2 antibodies suggesting a balanced Th1/Th2 response, whereas formulation of LASV GP with Alhydrogel elicited a IgG1-dominant response. Splenocytes secreting both Th1 and Th2 cytokines i.e., IFN-γ, TNF-α, IL-2, IL-4 and IL-5, were observed from mice receiving both antigen doses formulated with ISA 720, LiteVax and GPI-0100. However, robust, multifunctional T-cells were only detected in mice receiving a higher dose of LASV GP formulated with GPI-0100. Our results emphasize the importance of careful adjuvant selection and lay the immunological basis for a recombinant subunit protein LF vaccine formulation.

Highlights

Lassa Virus (LASV) is a highly pathogenic species of Old-World Arenavirus endemic to West Africa causing Lassa fever (LF), a potentially acute hemorrhagic disease, in infected individuals
Drosophila S2 cell-produced LASV GP purified by immunoaffinity chromatography (IAC) using a GP1-specific monoclonal antibody, followed by a secondary size-exclusion step to remove smaller subunits (Supplementary Figure 1A), appeared as intact GP-complex (GPC) or higher oligomers on Coomassie-stained SDS-PAGE, on a western blot, additional lower molecular bands representing GP1 and GP2 subunits appeared
We have shown that robust humoral and cellular immunity in outbred Swiss Webster (SW) mice can be generated using insect-cell derived, recombinant LASV GP purified using IAC and size exclusion chromatography (SEC), when paired with the appropriate adjuvant

Summary

Introduction

Lassa Virus (LASV) is a highly pathogenic species of Old-World Arenavirus endemic to West Africa causing Lassa fever (LF), a potentially acute hemorrhagic disease, in infected individuals. LF is a zoonotic disease transmitted by direct or indirect contact with rodent hosts. It results in approximately 300,000– 500,000 infections and nearly 5,000 deaths annually in West Africa, primarily documented throughout. Around 80-90% of infections are asymptomatic or mild, the mortality rate in hospitalized patients can reach 15% to 20% and upwards of 50% during epidemics [4]. Of the 6252 suspected LF cases, 1138 have been laboratory confirmed with 235 deaths, a case fatality rate (CFR) of 20.7% [5]. Neurological sequelae, including encephalopathy and aseptic meningitis, and sensorineural hearing loss is common in recovered patients [6, 7]

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