Insights into the L3 to L4 developmental program through proteomics

The establishment of infection with the lymphatic dwelling filarial parasites is dependent on the infectivity and subsequent development of the infective larvae (L3) within the human host to later stages (L4, adults) that require several developmental molts. The molecular mechanisms underlying the developmental processes in parasitic nematodes are not clearly defined. We report the proteomic profiles throughout the entire L3 to L4 molt using an established in vitro molting process for the human pathogen B. malayi. A total of 3466 proteins of B. malayi and 54 from Wolbachia were detected at one or more time points. Based on the proteomic profiling, the L3 to L4 molting proteome can be broadly divided into an early, middle and late phase. Enrichment of proteins, protein families and functional categories between each time point or between phases primarily relate to energy metabolism, immune evasion through secreted proteins, protein modification, and extracellular matrix-related processes involved in the development of new cuticle. Comparative analyses with somatic proteomes and transcriptomes highlighted the differential usage of cysteine proteinases (CPLs), BmCPL-1, -4 and -5 in the L3-L4 molt compared to the adults and microfilariae. Inhibition of the CPLs effectively blocked the in-vitro L3 to L4 molt. Overall, only 4 Wolbachia proteins (Wbm0495, Wbm0793, Wbm0635, and Wbm0786) were detected across all time points and suggest that they play an inconsequential role in the early developmental process. ImportanceThe neglected tropical diseases of lymphatic filariasis, onchocerciasis (or river blindness), and loiasis are the three major filarial infections of humans that cause long-term disability, impaired childhood growth, reduced reproductive capacity. Global efforts to control and/or eliminate these infections as a public health concern are based on strategies and tools to strengthen the diagnostics, therapeutic and prophylactic measures. A deeper understanding of the genes, proteins and pathways critical for the development of the parasite is needed to help further investigate the mechanisms of parasite establishment and disease progression, because not all the transmitted infective larvae get to develop successfully and establish infections. The significance of this study is in identifying the proteins and the pathways that are needed by the parasite for successful developmental molts, that in turn will allow for investigating targets of therapeutic and prophylactic potential.