Broadly Neutralizing Antibodies for Human Immunodeficiency Virus Treatment: Broad in Theory, Narrow in Reality.

In this viewpoint, we briefly review the status of antiretroviral therapy (ART), its unmet needs, and the role that broadly neutralizing antibodies (bNAbs) might have in the near future for the treatment of human immunodeficiency virus (HIV). We summarize advances in the development of bNAbs as antiretroviral therapy, the results of main clinical trials of bNAbs for HIV treatment and prevention, and its role in cure trials. The limitations of broadly neutralizing antibodies are the current need for primary resistance testing, the still unclear number of antibodies that must be combined, the lack of penetration in anatomical reservoirs, and the role they might play in cure studies. We compare the advantages and disadvantages of "classical ART" and therapy based on broadly neutralizing antibodies. We conclude that broadly neutralizing antibodies still need considerable improvements before they can be considered an alternative to classical ART.

To bnAb or Not to bnAb: Defining Broadly Neutralising Antibodies Against HIV-1.

Since their discovery, antibodies capable of broad neutralisation have been at the forefront of HIV-1 research and are of particular interest due to in vivo passive transfer studies demonstrating their potential to provide protection. Currently an exact definition of what is required for a monoclonal antibody to be classed as a broadly neutralising antibody (bnAb) has not yet been established. This has led to hundreds of antibodies with varying neutralisation breadth being studied and has given insight into antibody maturation pathways and epitopes targeted. However, even with this knowledge, immunisation studies and vaccination trials to date have had limited success in eliciting antibodies with neutralisation breadth. For this reason there is a growing need to identify factors specifically associated with bnAb development, yet to do this a set of criteria is necessary to distinguish bnAbs from non-bnAbs. This review aims to define what it means to be a HIV-1 bnAb by comparing neutralisation breadth, genetic features and epitopes of bnAbs, and in the process highlights the challenges of comparing the array of antibodies that have been isolated over the years.

Expressing anti-HIV VRC01 antibody using the murine IgG1 secretion signal in Pichia pastoris.

The use of the recombinant expression platform Pichia pastoris to produce pharmaceutically important proteins has been investigated over the past 30 years. Compared to mammalian cultures, expression in P. pastoris is cheaper and faster, potentially leading to decreased costs and process development times. Product yields depend on a number of factors including the secretion signal chosen for expression, which can influence the host cell response to recombinant protein production. VRC01, a broadly neutralising anti-HIV antibody, was expressed in P. pastoris, using the methanol inducible AOX1 promoter for both the heavy and light chains. Titre reached up to 3.05 µg mL-1 in small scale expression. VRC01 was expressed using both the α-mating factor signal peptide from Saccharomyces cerevisiae and the murine IgG1 signal peptide. Surprisingly, using the murine IgG1 signal peptide resulted in higher yield of antibody capable of binding gp140 antigen. Furthermore, we evaluated levels of secretory stress compared to the untransformed wild-type strain and show a reduced level of secretory stress in the murine IgG1 signal peptide strains versus those containing the α-MF signal peptide. As bottlenecks in the secretory pathway are often the limiting factor in protein secretion, reduced levels of secretory stress and the higher yield of functional antibody suggest the murine IgG1 signal peptide may lead to better protein folding and secretion. This work indicates the possibilities for utilising the murine IgG1 signal peptide for a range of antibodies, resulting in high yields and reduced cellular stress.