Antibody Preparations from Human Transchromosomic Cows Exhibit Prophylactic and Therapeutic Efficacy against Venezuelan Equine Encephalitis Virus.

Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne RNA virus that causes low mortality but high morbidity rates in humans. In addition to natural outbreaks, there is the potential for exposure to VEEV via aerosolized virus particles. There are currently no FDA-licensed vaccines or antiviral therapies for VEEV. Passive immunotherapy is an approved method used to protect individuals against several pathogens and toxins. Human polyclonal antibodies (PAbs) are ideal, but this is dependent upon serum from convalescent human donors, which is in limited supply. Non-human-derived PAbs can have serious immunoreactivity complications, and when "humanized," these antibodies may exhibit reduced neutralization efficiency. To address these issues, transchromosomic (Tc) bovines have been created, which can produce potent neutralizing human antibodies in response to hyperimmunization. In these studies, we have immunized these bovines with different VEEV immunogens and evaluated the protective efficacy of purified preparations of the resultant human polyclonal antisera against low- and high-dose VEEV challenges. These studies demonstrate that prophylactic or therapeutic administration of the polyclonal antibody preparations (TcPAbs) can protect mice against lethal subcutaneous or aerosol challenge with VEEV. Furthermore, significant protection against unrelated coinfecting viral pathogens can be conferred by combining individual virus-specific TcPAb preparations. IMPORTANCE With the globalization and spread or potential aerosol release of emerging infectious diseases, it will be critical to develop platforms that are able to produce therapeutics in a short time frame. By using a transchromosomic (Tc) bovine platform, it is theoretically possible to produce antigen-specific highly neutralizing therapeutic polyclonal human antibody (TcPAb) preparations in 6 months or less. In this study, we demonstrate that Tc bovine-derived Venezuelan equine encephalitis virus (VEEV)-specific TcPAbs are highly effective against VEEV infection that mimics not only the natural route of infection but also infection via aerosol exposure. Additionally, we show that combinatorial TcPAb preparations can be used to treat coinfections with divergent pathogens, demonstrating that the Tc bovine platform could be beneficial in areas where multiple infectious diseases occur contemporaneously or in the case of multipathogen release.