Strategies for the Improvement of HIV Envelope Protein Expression and Yield (R41/R42)

The purpose of this Funding Opportunity Announcement (FOA) is to encourage Small Business Technology Transfer (STTR) grant applications from Small Business Concerns (SBCs) and non-profit research institutions that will focus on innovative technologies and strategies to improve HIV envelope protein expression, yield and rapid universal purification platforms that would meet the requirements of regulatory agencies for clinical research use. Such technologies should have commercial potential.

There is an urgent need to have multiple HIV envelope immunogen components for use in HIV vaccine clinical studies.  Results of the RV144 vaccine clinical trial indicated that antibody responses to the gp120 B/E envelope proteins were the major components of the vaccine that contributed to the efficacy signal. 

In addition, the discovery of both broad and potent neutralizing antibodies against the HIV envelope in HIV infected individuals, provides additional evidence that the human immune system can respond effectively to the HIV envelope and so envelope could be the major component of an effective HIV vaccine. 

Results of contract manufacturing organizations (CMOs) efforts to produce envelope proteins using pre-existing platforms developed for Chinese hamster ovary (CHO)-based monoclonal antibody production have been disappointing. The use of CHO-based protein expressions systems previously used for the generation of monoclonal antibodies (mAbs) have resulted in significantly lower yields of HIV envelope proteins (100-1000x fold lower) compared to mAb expression (mgs/l of envelope product compared to the typical g/l yield of mAb).

Beyond issues of primary yield of the expression system, subsequent purification schemes for mAbs are not readily transferrable to HIV envelope purification and often result in 80-90% losses of envelope material; moreover purification schemes developed for one HIV envelope are not necessarily suitable for another HIV envelope due to the potentially large differences in post-translational modifications. Monoclonal antibodies are also able to withstand harsh viral clearance procedures whereas HIV envelopes are more delicate glycoproteins. These problems demonstrate the need for new approaches to enhance the production and purification of HIV envelope proteins.

This FOA will support research to improve the expression yield in a specific cell culture system (i.e. CHO), and the purification yield using specific purification regimens designed for HIV envelope protein suitable for use as clinical immunogens.  Projects may focus on any step of envelope expression and yield, improvement of substrates (i.e. CRISPR/Cas9 editing) or development of purification platforms.

Improved HIV envelope expression and yield may be explored by evaluation of approaches such as (but not limited to):

• codon usage;
• epigenetic targets that modulate expression;
• enhancement of transcription or of mRNA sequence and structure;
• enhancement of post-transcription processing,
• translation, or post-translational modifications (including glycosylation or disulfide composition); and
• the production of intracellular, membrane-associated, or secreted protein.

Projects may focus on (but not limited to):

• improving existing cell substrates
• development of novel cell substrates
• enhancement of cellular processes (e.g. chaperonins)
• removal of deleterious proteases
• addition or removal of enzymes involved in glycosylation
• alteration in epigenetic targets
• removal of endogenous retroviruses

Projects may develop universal HIV envelope protein purification methodologies including (but not limited to):

• affinity purification approaches
• other highly novel strategies

Research areas NOT supported by this FOA:

• Non-Envelope protein vaccines
• Lectin-based purification schemes
• Approaches proposing clinical trials

It is important to emphasize that the topics listed above are only meant to be illustrative, and not a comprehensive list of appropriate topics, or exclusive of other appropriate topics. Applications may propose projects that are highly innovative or that are enhancements of current approaches. In either case, studies must significantly advance the current state of the art and have commercial potential.    

See Section VIII. Other Information for award authorities and regulations.