Production and Immunogenicity of Soluble Plant-Produced HIV-1 Subtype C Envelope gp140 Immunogens.

Emmanuel Margolin,Edward P Rybicki,Brandon Weber,Ann E Meyers,Phindile Ximba,Lynn Morris,Tandile Hermanus,Rosamund Chapman,Michiel T Van Diepen,Anna-Lise Williamson,Carol Crowther

doi:10.3389/fpls.2019.01378

Abstract

The development of effective vaccines is urgently needed to curb the spread of human immunodeficiency virus type 1 (HIV-1). A major focal point of current HIV vaccine research is the production of soluble envelope (Env) glycoproteins which reproduce the structure of the native gp160 trimer. These antigens are produced in mammalian cells, which requires a sophisticated infrastructure for manufacture that is mostly absent in developing countries. The production of recombinant proteins in plants is an attractive alternative for the potentially cheap and scalable production of vaccine antigens, especially for developing countries. In this study, we developed a transient expression system in Nicotiana benthamiana for the production of soluble HIV Env gp140 antigens based on two rationally selected virus isolates (CAP256 SU and Du151). The scalability of the platform was demonstrated and both affinity and size exclusion chromatography (SEC) were explored for recovery of the recombinant antigens. Rabbits immunized with lectin affinity-purified antigens developed high titres of binding antibodies, including against the V1V2 loop region, and neutralizing antibodies against Tier 1 viruses. The removal of aggregated Env species by gel filtration resulted in the elicitation of superior binding and neutralizing antibodies. Furthermore, a heterologous prime-boost regimen employing a recombinant modified vaccinia Ankara (rMVA) vaccine, followed by boosts with the SEC-purified protein, significantly improved the immunogenicity. To our knowledge, this is the first study to assess the immunogenicity of a near-full length plant-derived Env vaccine immunogen.

Highlights

Prophylactic vaccines are urgently needed to combat human immunodeficiency virus type 1 (HIV-1), in Sub-Saharan Africa which remains disproportionately affected by the pandemic and accounts for the majority of new infections and AIDS-related deaths (Shao and Williamson 2012)
We report the development of an Agrobacteriummediated transient expression system for the production of cognate soluble HIV-1 subtype C gp140 antigens in N. benthamiana plants, and immunological studies of these proteins in rabbits
Given the reduced infrastructure requirements and the potential for rapid scalability of plant production systems for recombinant proteins, we have investigated the feasibility of a transient expression platform in N. benthamiana plants for the production of a HIV Env-derived candidate vaccine antigen

Summary

Introduction

Prophylactic vaccines are urgently needed to combat HIV-1, in Sub-Saharan Africa which remains disproportionately affected by the pandemic and accounts for the majority of new infections and AIDS-related deaths (Shao and Williamson 2012). It is estimated that ~1.8 million new infections and ~1 million deaths from AIDS-related illnesses occurred in 2016 alone (www.unaids.org). Sub-Saharan Africa accounted for 64% of new infections during this period. None of the candidate vaccines evaluated in clinical trials have achieved the level of efficacy required for licensure, recent insights into the development of broadly crossneutralizing antibodies during natural infection and advances in the rational design of immunogens have renewed interest in the development of prophylactic vaccines (Stephenson et al, 2016; McCoy and McKnight 2017; Sanders and Moore, 2017). It is evident that non-neutralizing antibodies against Env contribute to protection against HIV infection by means of Fc-mediated effector functions (Rerks-Ngarm et al, 2009; Haynes et al, 2012; Barouch et al, 2015; Alter and Barouch 2018)

Objectives

Methods

Results

Conclusion