Venom diversity in Naja mossambica: Insights from proteomic and immunochemical analyses reveal intraspecific differences

Background Intraspecific variations in snake venom composition have been extensively documented, contributing to the diverse clinical effects observed in envenomed patients. Understanding these variations is essential for developing effective snakebite management strategies and targeted antivenom therapies. This study was prompted by the observations made by clinicians, who have noted significant variations in clinical outcomes among patients bitten by Naja mossambica in different regions of Africa, which links to the phenomenon of intra-species venom variability. We aimed to comprehensively investigate venoms from three distinct populations of N. mossambica from Eswatini, Limpopo, and KwaZulu-Natal regions in Africa in terms of their protein composition and reactivity with three commercial antivenoms (SAIMR polyvalent, EchiTAb+ICP, and Antivipmyn Africa). Methodology/Principal Findings In contrast to previous reports, we discovered an unexpectedly high concentration of neurotoxic proteins in N. mossambica venoms (approximately 15%). The Eswatini population of Mozambique spitting cobra exhibited an increased abundance and diversity of neurotoxic proteins, including neurotoxic 3FTxs, kunitz-type inhibitors, vespryns, and mamba intestinal toxin 1. Immunochemical assessments of venom-antivenom reactivity unveiled differences, primarily related to low-abundance proteins. Notably, the reactivity of EchiTAb+ICP antivenom surpassed that of the widely used SAIMR polyvalent in serial dilution ELISA assays. Conclusions/Significance Our findings reveal a substantial presence of neurotoxic proteins in N. mossambica venoms, challenging previous understandings of their composition. Additionally, the detection of numerous peptides aligning to uncharacterized proteins or proteins with unknown functions underscores a critical issue with existing venom protein databases, emphasizing the substantial gaps in our knowledge of snake venom protein components. This underscores the need for enhanced research in this domain. Significantly, our research highlights the superior reactivity of EchiTAb+ICP antivenom compared to SAIMR polyvalent, providing another compelling argument for its potential as an alternative to the commonly used SAIMR antivenom. Author Summary Snakebite envenoming is a pervasive global health concern, posing substantial risks, particularly in less developed regions. The intricate variations in venom composition within a single species have been well-documented, contributing significantly to the varied clinical effects experienced by envenomed patients. It is imperative to unravel these variations, as they are pivotal in the formulation of effective snakebite management strategies and the development of targeted antivenom therapies. In this study, our focus rested on the venom of the Naja mossambica species, dwelling in diverse African regions. Our objective was to delve into the toxin composition of these venoms and understand how these toxins interact with commercially available antivenoms. This exploration was aimed to uncover which toxins, despite antivenom application, evade neutralization. This information becomes a cornerstone in the design of more potent and efficacious antivenoms, contributing to a nuanced approach in combating the complex landscape of snakebite envenoming.