The maturation of antibody technology for the HIV epidemic

Exploration of broadly neutralizing antibody fragments produced in bacteria for the control of HIV

While broadly neutralizing antibodies (bnAbs) are a promising preventative and therapeutic tool for HIV infection, production is difficult and expensive. Production of antibody-like fragments in bacterial cytoplasm provides a cheaper alternative. This work explored the transplantation of the complementarity determining regions of the anti-HIV bnAbs PGT121 and 10E8 onto a single-chain variable fragment (scFv) scaffold, previously discovered through a novel screening platform. The scaffolded 10E8 scFv, but not the scaffolded PGT121 scFv, was soluble in bacterial cytoplasm, enabling efficient production in bacteria. Three additional multimeric constructs employing the scaffolded 10E8 scFv were also generated and soluble versions produced in bacteria. However, the constructs were found to have substantially lost anti-HIV binding function and had completely abrogated neutralizing activity. Overall, while this study provides a proof-of-concept for anti-HIV bnAb construct production in bacterial cytoplasm, future refinement of these technologies will be required to realize the goal of producing inexpensive and effective bnAb-like tools for the control of HIV.

Bispecific antibodies for viral immunotherapy

Bispecific antibody engineering, in which binding specificities toward 2 distinct epitopes are combined into a single molecule, can greatly enhance immunotherapeutic properties of monoclonal antibodies. While the bispecific antibody approach has been applied widely to targets for indications such as cancer and inflammation, the development of such agents for viral immunotherapy is only now emerging. Here, we review recent advances in the development of bispecific antibodies for viral immunotherapy, highlighting promising in vitro and in vivo results.

Towards an HIV cure based on targeted killing of infected cells: different approaches against acute versus chronic infection

PURPOSE OF REVIEW

Current regimens of combination antiretroviral therapy (cART) offer effective control of HIV infection, with maintenance of immune health and near-normal life expectancy. What will it take to progress beyond the status quo, whereby infectious virus can be eradicated (a 'sterilizing cure') or fully controlled without the need for ongoing cART (a 'functional cure')?

RECENT FINDINGS

On the basis of therapeutic advances in the cancer field, we propose that targeted cytotoxic therapy to kill HIV-infected cells represents a logical complement to cART for achieving an HIV cure. This concept is based on the fact that cART effectively blocks replication of the virus, but does not eliminate cells that are already infected; targeted cytotoxic therapy would contribute precisely this missing component. We suggest that different modalities are suited for curing primary acute versus established chronic infection. For acute infection, relatively short-acting potent agents such as recombinant immunotoxins might prove sufficient for HIV eradication, whereas for chronic infection, a long-lasting (lifelong?) modality is required to maintain full virus control, as might be achieved with genetically modified autologous T cells.

SUMMARY

We present perspectives for complementing cART with targeted cytotoxic therapy, whereby HIV infection is either eradicated or fully controlled, thereby eliminating the need for lifelong cART.

In situ production of therapeutic monoclonal antibodies

The use of antibodies as a treatment for disease has it origins in experiments performed in the 1890s, and since these initial experiments, monoclonal antibodies (mAbs) have become one of the fastest growing therapeutic classes for the treatment of cancer, autoimmune disease, and infectious diseases. However, treatment with therapeutic mAbs often requires high doses given via long infusions or multiple injections, which, coupled with the prohibitively high cost associated with the production of clinical-grade proteins and the transient serum half-lives that necessitate multiple administrations to gain therapeutic benefits, makes large-scale treatment of patients, especially patients in the developing world, difficult. Due to their low-cost and rapid scalability, nucleic acid-based approaches to deliver antibody gene sequences for in situ mAb production have gained substantial traction. In this review, we discuss new approaches to produce therapeutic mAbs in situ to overcome the need for the passive infusion of purified protein.