Genetically delivered antibody protects against West Nile virus

Therapeutic Efficacy of Vectored PGT121 Gene Delivery in HIV-1-Infected Humanized Mice

Broadly neutralizing antibodies (bNAbs) are being explored for HIV-1 prevention and cure strategies. However, administration of purified bNAbs poses challenges in resource-poor settings, where the HIV-1 disease burden is greatest. In vivo vector-based production of bNAbs represents an alternative strategy. We investigated adenovirus serotype 5 (Ad5) and adeno-associated virus serotype 1 (AAV1) vectors to deliver the HIV-1-specific bNAb PGT121 in wild-type and immunocompromised C57BL/6 mice as well as in HIV-1-infected bone marrow-liver-thymus (BLT) humanized mice. Ad5.PGT121 and AAV1.PGT121 produced functional antibody in vivo. Ad5.PGT121 produced PGT121 rapidly within 6 h, whereas AAV1.PGT121 produced detectable PGT121 in serum by 72 h. Serum PGT121 levels were rapidly reduced by the generation of anti-PGT121 antibodies in immunocompetent mice but were durably maintained in immunocompromised mice. In HIV-1-infected BLT humanized mice, Ad5.PGT121 resulted in a greater reduction of viral loads than did AAV1.PGT121. Ad5.PGT121 also led to more-sustained virologic control than purified PGT121 IgG. Ad5.PGT121 afforded more rapid, robust, and durable antiviral efficacy than AAV1.PGT121 and purified PGT121 IgG in HIV-1-infected humanized mice. Further evaluation of vector delivery of HIV-1 bNAbs is warranted, although approaches to prevent the generation of antiantibody responses may also be required.

IMPORTANCE Broadly neutralizing antibodies (bNAbs) are being explored for HIV-1 prevention and cure strategies, but delivery of purified antibodies may prove challenging. We investigated adenovirus serotype 5 (Ad5) and adeno-associated virus serotype 1 (AAV1) vectors to deliver the HIV-1-specific bNAb PGT121. Ad5.PGT121 afforded more rapid, robust, and durable antiviral efficacy than AAV1.PGT121 and purified PGT121 IgG in HIV-1-infected humanized mice.

State of play and clinical prospects of antibody gene transfer

Recombinant monoclonal antibodies (mAbs) are one of today's most successful therapeutic classes in inflammatory diseases and oncology. A wider accessibility and implementation, however, is hampered by the high product cost and prolonged need for frequent administration. The surge in more effective mAb combination therapies further adds to the costs and risk of toxicity. To address these issues, antibody gene transfer seeks to administer to patients the mAb-encoding nucleotide sequence, rather than the mAb protein. This allows the body to produce its own medicine in a cost- and labor-effective manner, for a prolonged period of time. Expressed mAbs can be secreted systemically or locally, depending on the production site. The current review outlines the state of play and clinical prospects of antibody gene transfer, thereby highlighting recent innovations, opportunities and remaining hurdles. Different expression platforms and a multitude of administration sites have been pursued. Viral vector-mediated mAb expression thereby made the most significant strides. Therapeutic proof of concept has been demonstrated in mice and non-human primates, and intramuscular vectored mAb therapy is under clinical evaluation. However, viral vectors face limitations, particularly in terms of immunogenicity. In recent years, naked DNA has gained ground as an alternative. Attained serum mAb titers in mice, however, remain far below those obtained with viral vectors, and robust pharmacokinetic data in larger animals is limited. The broad translatability of DNA-based antibody therapy remains uncertain, despite ongoing evaluation in patients. RNA presents another emerging platform for antibody gene transfer. Early reports in mice show that mRNA may be able to rival with viral vectors in terms of generated serum mAb titers, although expression appears more short-lived. Overall, substantial progress has been made in the clinical translation of antibody gene transfer. While challenges persist, clinical prospects are amplified by ongoing innovations and the versatility of antibody gene transfer. Clinical introduction can be expedited by selecting the platform approach currently best suited for the mAb or disease of interest. Innovations in expression platform, administration and antibody technology are expected to further improve overall safety and efficacy, and unlock the vast clinical potential of antibody gene transfer.

Development of a human live attenuated West Nile infectious DNA vaccine: Identification of a minimal mutation set conferring the attenuation level acceptable for a human vaccine

For the development of a human West Nile (WN) infectious DNA (iDNA) vaccine, we created highly attenuated chimeric virus W1806 with the serological identity of highly virulent WN-NY99. Earlier, we attempted to utilize mutations found in the E protein of the SA14-14-2 vaccine to bring safety of W1806 to the level acceptable for human use (Yamshchikov et al., 2016). Here, we analyzed effects of the SA14-14-2 changes on growth properties and neurovirulence of W1806. A set including the E138K, K279M, K439R and G447D changes was identified as the perspective subset for satisfying the target safety profile without compromising immunogenicity of the vaccine candidate. The genetic stability of the attenuated phenotype was found to be unsatisfactory being dependent on a subset of attenuating changes incorporated in W1806. Elucidation of underlying mechanisms influencing selection of pathways for restoration of the envelope protein functionality will facilitate resolution of the emerged genetic stability issue.

Development of a human live attenuated West Nile infectious DNA vaccine: Suitability of attenuating mutations found in SA14-14-2 for WN vaccine design

Direct attenuation of West Nile (WN) virus strain NY99 for the purpose of vaccine development is not feasible due to its high virulence and pathogenicity. Instead, we created highly attenuated chimeric virus W1806 with the serological identity of NY99. To further attenuate W1806, we investigated effects of mutations found in Japanese encephalitis virus vaccine SA14-14-2. WN viruses carrying all attenuating mutations lost infectivity in mammalian, but not in mosquito cells. No single reversion restored infectivity in mammalian cells, although increased infectivity in mosquito cells was observed. To identify a subset of mutations suitable for further attenuation of W1806, we analyzed effects of E138K and K279M changes on virulence, growth properties, and immunogenicity of derivatized W956, from which chimeric W1806 inherited its biological properties and attenuation profile. Despite strong dominant attenuating effect, introduction of only two mutations was not sufficient for attenuating W1806 to the safety level acceptable for human use.

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.

Vaccines and immunotherapeutics for the prevention and treatment of infections with West Nile virus

The emergence of West Nile virus (WNV) in North America in 1999 as a cause of severe neurological disease in humans, horses and birds stimulated development of vaccines for human and veterinary use, as well as polyclonal/monoclonal antibodies and other immunomodulating compounds for use as therapeutics. Although disease incidence in North America has declined since the peak epidemics in 2002-2003, the virus has continued to be annually transmitted in the Americas and to cause periodic epidemics in Europe and the Middle East. Continued transmission of the virus with human and animal disease suggests that vaccines and therapeutics for the prevention and treatment of WNV disease could be of great benefit. This article focuses on progress in development and evaluation of vaccines and immunotherapeutics for the prevention and treatment of WNV disease in humans and animals.

Engineering human cells for in vivo secretion of antibody and non-antibody therapeutic proteins

Purified proteins such as antibodies are widely used as therapeutic agents in clinical medicine. However, clinical-grade proteins for therapeutic use require sophisticated technologies and are extremely expensive to produce. In vivo secretion of therapeutic proteins by genetically engineered human cells may advantageously replace injection of highly purified proteins. The use of gene transfer methods circumvents problems related to large-scale production and purification and offers additional benefits by achieving sustained concentrations of therapeutic protein with a syngenic glycosylation pattern that make the protein potentially less immunogenic. The feasibility of the in vivo production of therapeutic proteins by diverse cells/tissues has now been demonstrated using different techniques, such as ex vivo genetically modified cells and in vivo gene transfer mediated by viral vectors.

Human Monoclonal Fab Antibodies Against West Nile Virus and its Neutralizing Activity Analyzed in Vitro and in Vivo

The disease progression with West Nile virus (WNV) infection in humans leads to meningitis or encephalitis and may cause death, particularly among elderly and immunocompromised individuals. Passive immunity using immunoglobulins has shown efficacy in treating some patients with WNV infection, which makes the development of human anti-WNV antibodies significant. The goal of this study was to construct a Fab-specific phage display library against WNV, and to identify and select clones with neutralizing activities. Total RNA was extracted from peripheral blood lymphocytes (PBLs) of two immunized individuals, and RT-PCR was used to amplify the Fab fragments containing the heavy (V(H)) and light (V(L)) chains. The amplified genes were sequentially cloned into the recombinant antibody expression vector pComb3-H, and the Fab-specific phage display library was packaged with helper phage VCS-M13. Five rounds of panning were carried out with WNV E protein domain III, and then binding antibodies were selected by ELISA. Antigen binding specificity, complementarity determining region (CDR) sequence of V(H) and V(L), and neutralizing activity against WNV were analyzed in vitro and in vivo. Eight Fab monoclonal antibodies recognized E protein domain III from a library of 7×10(7) clones/ml. Of the eight, one (Fab 1), exhibited significant neutralizing activity, and completely blocked 100 pfu WNV infection in Vero cells at a concentration 160 μg/ml. In contrast, Fab 13 and Fab 25, showed weaker neutralizing activities, and modestly blocked 100 pfu WNV infections at concentrations of 320 μg/ml and 160 μg/ml, respectively. However, animal studies showed that Fab 1 failed to protect mice from death at the concentration of 160μg/ml indicating that the neutralizing potential of an antibody in vivo is determined by the strength of binding and the abundance of its epitope for the virion.

Vector-mediated gene transfer engenders long-lived neutralizing activity and protection against SIV infection in monkeys

The holy grail for HIV vaccine development is an immunogen that elicits persisting antibodies with broad neutralizing activity against field strains of the virus. Unfortunately, very little progress has been made in finding or designing such immunogens. Using the SIV model, we have taken a markedly different approach: delivery of an adeno-associated virus (AAV) gene transfer vector to muscle for the expression of antibodies or antibody-like immunoadhesins having predetermined anti-SIV specificity. With this approach, anti-SIV molecules are endogenously synthesized in myofibers and passively distributed to the circulatory system. Using such an approach in monkeys, we have now generated long-lasting neutralizing activity in serum and observed complete protection against intravenous challenge with virulent SIV. In essence, this strategy bypasses the adaptive immune system and holds significant promise as a novel approach to an effective HIV vaccine.