Antibody gene transfer with adeno-associated viral vectors as a method for HIV prevention

Broadly neutralizing antibodies (bNAbs) against human immunodeficiency virus (HIV) show great promise in HIV prevention as they are capable of potently neutralizing a considerable breadth of genetically diverse strains. Passive transfer of monoclonal bNAb proteins can confer protection in animal models of HIV infection at modest concentrations, inspiring efforts to develop an HIV vaccine capable of eliciting bNAb responses. However, these antibodies demonstrate high degrees of somatic mutation and other unique characteristics that may hinder the ability of conventional approaches to consistently and effectively produce bNAb analogs. As an alternative strategy, we and others have proposed vector-mediated gene transfer to generate long-term, systemic production of bNAbs in the absence of immunization. Herein, we review the use of adeno-associated virus (AAV) vectors for delivery of HIV bNAbs and antibody-like proteins and summarize both the advantages and disadvantages of this strategy as a method for HIV prevention

Broad protection against influenza infection by vectored immunoprophylaxis in mice

Neutralizing antibodies that target epitopes conserved among many strains of influenza virus have been recently isolated from humans. Here we demonstrate that adeno-associated viruses (AAV) encoding two such broadly neutralizing antibodies are protective against diverse influenza strains. Serum from mice that received a single intramuscular AAV injection efficiently neutralized all H1, H2 and H5 influenza strains tested. After infection with diverse strains of H1N1 influenza, treated mice showed minimal weight loss and lung inflammation. Protection lasted for at least 11 months after AAV injection. Notably, even immunodeficient and older mice were protected by this method, suggesting that expression of a monoclonal antibody alone is sufficient to protect mice from illness. If translated to humans, this prophylactic approach may be uniquely capable of protecting immunocompromised or elderly patient populations not reliably protected by existing vaccines

Vectored antibody gene delivery protects against Plasmodium falciparum sporozoite challenge in mice

Malaria caused by Plasmodium falciparum kills nearly one million children each year and imposes crippling economic burdens on families and nations worldwide. No licensed vaccine exists, but infection can be prevented by antibodies against the circumsporozoite protein (CSP), the major surface protein of sporozoites, the form of the parasite injected by mosquitoes. We have used vectored immunoprophylaxis (VIP), an adeno-associated virus-based technology, to introduce preformed antibody genes encoding anti-P. falciparum CSP mAb into mice. VIP vector-transduced mice exhibited long-lived mAb expression at up to 1,200 µg/mL in serum, and up to 70% were protected from both i.v. and mosquito bite challenge with transgenic Plasmodium berghei rodent sporozoites that incorporate the P. falciparum target of the mAb in their CSP. Serum antibody levels and protection from mosquito bite challenge were dependent on the dose of the VIP vector. All individual mice expressing CSP-specific mAb 2A10 at 1 mg/mL or more were completely protected, suggesting that in this model system, exceeding that threshold results in consistent sterile protection. Our results demonstrate the potential of VIP as a path toward the elusive goal of immunization against malaria

Durable Suppression of Established Transmitted Founder Replication in Infected BLT Humanized Mice by Vectored Immuno Therapy

Recent reports in humanized mice and monkeys have found that broadly neutralizing antibodies (bNAbs) can suppress the replication of laboratory strains of HIV and SHIV while bNAb concentration remains high. Vectored ImmunoProphylaxis (VIP) results in long-lived bNAb expression following a single intramuscular {IM) injection of a specialized viral vector, and this approach has been demonstrated as a means of durably suppressing viral load. However, previous reports of VIP-delivered bNAbs for HIV therapy required prior antiretroviral drug therapy to reduce viral load to prevent escape. Methods: Humanized BLT mice were infected IV with the REJO.c transmitted molecular founder strain of HIV. A low dose of combination antiretroviral therapy (ART) was administered to these animals for 5 weeks, followed by a single IM injection of VIP expressing VRC07 or luciferase. Mouse plasma was analyzed by ELISA to determine antibody concentration and by qPCR to determine viral load. Cellular fractions were analyzed by flow cytometry to quantify human CD4 cells over time. After sacrifice, plasma was subjected to a clinically validated ultrasensitive PCR-based viral load assay. Results: We detected viral loads of 10^5 copies/mL in infected mice prior to low-dose ART treatment, which resulted in a transient reduction and rebound to pre-therapy loads. Following VIP administration, we observed a rapid increase in the blood concentration of VRC07. Mice expressing VRC07 exhibited a sharp decline in viral load to undetectable levels and an increase in CD4 cells over four weeks and this effect was sustained for the remaining 8 weeks of the study. In contrast, mice expressing luciferase exhibited increasing viral loads with concomitant decreases in CD4 cells throughout the study. Conclusions: Our results demonstrate that VIP expressing VRC07 is sufficient to suppress actively replicating transmitted founder virus at high viral load and support efforts to move Vectored Immuno Therapy into clinical trials with infected patients

Generation and characterization of infectious molecular clones of transmitted/founder HIV-1 subtype C viruses

The genetic diversity of HIV impedes vaccine development. Identifying the viral properties of transmitted/founder (T/F) variants may provide a common vaccine target. To study the biological nature of T/F viruses, we constructed full-length clones from women detected during Fiebig stage I acute HIV-1 infection (AHI) from heterosexual male-to-female (MTF) transmission; and clones after one year of infection using In-Fusion-based cloning. Eighteen full-length T/F clones were generated from 9 women and six chronic infection clones were from 2 individuals. All clones but one were non-recombinant subtype C. Three of the 5 T/F clones and 3 chronic clones tested replicated efficiently in PBMCs and utilised CCR5 coreceptor for cell entry. Transmitted/founder and chronic infection clones displayed heterogenous in vitro replicative capacity and resistance to type I interferon. T/F viruses had shorter Env glycoproteins and fewer N-linked glycosylation sites in Env. Our findings suggest MTF transmission may select viruses with compact envelopes

Broadly neutralizing antibodies abrogate established hepatitis C virus infection

In most exposed individuals, hepatitis C virus (HCV) establishes a chronic infection; this long-term infection in turn contributes to the development of liver diseases such as cirrhosis and hepatocellular carcinoma. The role of antibodies directed against HCV in disease progression is poorly understood. Neutralizing antibodies (nAbs) can prevent HCV infection in vitro and in animal models. However, the effects of nAbs on an established HCV infection are unclear. We demonstrate that three broadly nAbs—AR3A, AR3B, and AR4A—delivered with adeno-associated viral vectors can confer protection against viral challenge in humanized mice. Furthermore, we provide evidence that nAbs can abrogate an ongoing HCV infection in primary hepatocyte cultures and in a human liver chimeric mouse model. These results showcase a therapeutic approach to interfere with HCV infection by exploiting a previously unappreciated need for HCV to continuously infect new hepatocytes to sustain a chronic infection