Project Lead(s): Karl Riabowol
The United Nations AIDS task force states that 34 million persons are infected with HIV, 24 million of whom are in Sub-Saharan Africa, where treatment with current approaches is challenging.
Natural human neutralizing antibodies block HIV entry into T cells, but such antibody production is very rare in patients, while making conventional antibodies in bulk for treatment is difficult, expensive and inefficient.
There is a need for rapidly and inexpensively producing neutralizing antibodies that recognizes newly identified regions of HIV proteins and can broadly block infection in all known viral subtypes.
Special antibodies, called ‘heavy chain only’ antibodies, produced only in some species, such as camelids (llamas, camels and alpacas) are very stable and would be very useful if they could be isolated and produced.
The major objective of the project was to produce a short peptide corresponding to the membrane proximal external region (MPER) of GP41, to use as an immunizing agent to develop a unique form of antibody made in the camelid family.
Previous studies from other groups identified the MPER region of the HIV glycoprotein as the target of very rare human neutralizing antibodies produced by individuals who show natural immunity to HIV infection.
The team proposed to produce ‘heavy chain only’ antibodies using alpacas, to test them using in vitro HIV infection assays and, if they were able to isolate such neutralizing antibodies, to produce the antibodies in bulk for tests in human subjects.
Six alpacas were purchased and used to produce such antibodies, followed by a number of attempts to produce the MPER peptide.
The project did not achieve proof of concept during the project period.
Several attempts were made to produce the peptide in bacterial and human cells but, whenever a cell produced the MPER, it killed the host cells, indicating that the sequence was very toxic.
After trying a number of strategies, the team was able to produce an MPER sequence biochemically fused to a known immunogenic protein called ING1, using an in vitro transcription-translation system that did not use any form of live cell, but nonetheless made the fusion protein of interest.
They used this to immunize alpacas and followed published protocols for finding cells that produce the antibody that they were trying to isolate.
After several unsuccessful attempts, the project team developed a new strategy for isolating such antibodies, and are now beginning to characterize them regarding exactly what they recognize and how strongly they interact with their target sequences.
The research team is still confirming whether the clones that they isolated are capable of recognizing the MPER in HIV and neutralizing different strains of HIV.
If they do prove effective, the team will proceed to patent the sequences, engineer them into various vectors, and produce these targeting antibodies in amounts sufficient to test in a clinical trial.