Third generation antivenomics: Pushing the limits of the in vitro preclinical assessment of antivenoms

Abstract

Second generation antivenomics is a translational venomics approach designed to complement in vivo preclinical neutralization assays. It provides qualitative and quantitative information on the set of homologous and heterologous venom proteins presenting antivenom-recognized epitopes and those exhibiting impaired immunoreactivity. In a situation of worrying antivenom shortage in many tropical and sub-tropical regions with high snakebite mortality and morbidity rates, such knowledge has the potential to facilitate the optimal deployment of currently existing antivenoms and to aid in the rational design of novel broad specificity antidotes. The aim of the present work was to expand the analytical capability of the immunoaffinity second-generation antivenomics platform, endowing it with the ability to determine the maximal binding capacity of an antivenom toward the different toxins present in a venom, and to quantify the fraction of venom-specific antibodies present in a given antivenom. The application of this new platform, termed third generation (3G) antivenomics, in the preclinical evaluation of antivenoms is illustrated in this paper for the case of antivenom EchiTAb-Plus-ICP ® reactivity towards the toxins of homologous (B. arietans) and heterologous (N. melanoleuca) venoms.Toxins 2017, 9, 158 2 of 12 launch by the WHO of a prequalification scheme of antivenoms for sub-Saharan Africa, a programme also supported by the Global Snakebite Initiative and Médecins Sans Frontières [5,[16][17][18].The shortage of antivenoms can be in part counteracted by designing improved polyspecific antivenoms with a broad neutralizing spectrum, but also by a more rational use of existing antivenoms, i.e., through a systematic and detailed study of their paraspecificity. However, defining the venom cross-reactivity landscape of an antivenom is not a trivial matter, given the well-documented occurrence of venom variability in space (intra-and interpopulation) and time (ontogenetic) within and between all taxonomic levels [19][20][21][22]. This circumstance prevents the use of phylogenetic distance as a measure of venom compositional relatedness, even between closely-related species [23]. To assess the paraspecificity of antivenoms to the level of species-specific toxins, a proteomics-based protocol coined "antivenomics" was introduced in 2008, designed to quantify the extent of cross-reactivity of an antivenom against homologous and heterologous venoms at toxin resolution [24]. The initial protocol, which was based on the in-solution immunoprecipitation of antigen-antibody complexes followed by the chromatographic quantification of the free antigen present in the supenatant, was only suitable for whole IgG antivenoms. This "first generation" approach was subsequently re-designed for the assessment of F(ab') 2 and Fab antivenoms [25]. Key to this update was the immobilization of the antivenom molecules on a chromatographic matrix to generate an immunoaffinity column [25]. Among the most relevant advantages of this immunoaffinity-bas...

Venomics and antivenomics of the poorly studied Brazil’s lancehead, Bothrops brazili (Hoge, 1954), from the Brazilian State of Pará

“…Third-generation antivenomics [40,41] was applied to compare the immunoreactivity of the Brazilian pentabothropic antivenom (SAB) towards the venoms of B. brazili and B. jararaca from the southeastern clade population within the Brazilian Atlantic forest [42] (used as reference venom). To this end, one vial of antivenom was dialyzed against MilliQ® water, lyophilized, and 150 mg of total lyophilizate weight were reconstituted in 6 mL of 0.2 M NaHCO 3 , 0.5 M NaCl, pH 8.3 (coupling buffer).…”

“…In Brazil, envenomings by bothropic species are clinically treated with equine polyspecific pentabothropic (SAB) or antibothropiclachetic F(ab') 2 antivenoms. Queiroz et al [55] Here, we have applied third-generation antivenomics [40,41] to compare the qualitative and quantitative immunorecognition capability of the SAB antivenom produced at Butantan Institute (SP, Brazil) toward the venom toxins of B. brazili (Pará) and B. jararaca (reference venom). Analysis of the concentrationdependent immunocapturing profile of the SAB antivenom affinity columns showed paraspecific immunoreactivity against all the toxin classes of B. brazili venom (Fig.…”

Antibody Cross-Reactivity in Antivenom Research

“…In 2017, a further updated protocol was developed for antivenomics, “third generation (3G) antivenomics”, as seen in Figure 2 , 3G [ 72 ]. This methodology was designed to enable the determination of the maximal binding capacity of an antivenom against each toxin in a venom, as well as the quantification of the fraction of toxin-specific antibodies present in the antivenom.…”

“…This methodology was designed to enable the determination of the maximal binding capacity of an antivenom against each toxin in a venom, as well as the quantification of the fraction of toxin-specific antibodies present in the antivenom. This permitted improved estimates of the quantities of antivenom required to neutralize a certain amount of venom [ 72 ]. These improvements were achieved through the application of size exclusion HPLC, which can be advantageous compared to other chromatographic methods, as it conserves the native structure and binding characteristics of venoms and antivenoms [ 72 ].…”

“…This permitted improved estimates of the quantities of antivenom required to neutralize a certain amount of venom [ 72 ]. These improvements were achieved through the application of size exclusion HPLC, which can be advantageous compared to other chromatographic methods, as it conserves the native structure and binding characteristics of venoms and antivenoms [ 72 ]. This advancement in the analytical capabilities of antivenomics allows for a more functional and direct in vitro comparison of different antivenoms raised against venoms of the same species [ 72 ].…”