Molecular Definition Of Filarial And Related Nonfilarial Genes And Proteins

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

Having completed the genomes of Loa loa, W. bancrofti, and (most recently) O.volvulus, we have utilized the genomic data as the backdrop for performing a large number of proteomic and transcriptomic studies. We have completed a large-scale proteomic and transcriptomic characterization of almost all the major mammalian stages of O. volvulus, resulting in the identification of more than 85-90% of the products predicted from the O. volvulus genome/putative proteome. The analysis also yielded much of the proteome of Wolbachia, the obligate endosymbiont of O. volvulus. Parasite sex- and stage-specific protein expression identified those pathways related to parasite differentiation. To understand better the developmental programs that underscore the transition between the mosquito-derived infective stage larvae (L3) to mammalian adapted L3s and to L4s following a molt, and the initial week of adaptation to the human host, we adapted an in vitro system that allowed for L3 development and subsequent molting to the L4. Using microarray and proteomic assessments at multiple times through this 9 day process we have not only identified those genes/pathways that are critical for the L3/L4 transition but we have also demonstrated by both pharmacologic inhibition (cysteine protease inhibition) and RNAi (of the critical CPLs) the critical role played by cysteine proteases in the early development of mammalian adapted L3s to L4s. We have recently performed shotgun mass spectroscopy on both human sera of patients with defined filarial infections, excretory/secretory (E/S) products of Loa loa microfilariae, all stages of the O. vovlulus worm, and appropriate controls to identify parasite derived biomarkers of active infection. This has led to identification of molecular targets that have been used d to configure quantitative immunoassays for the rapid detection of active infection for O. volvulus and Loa loa. We have generated a 296 megabase (Mb) reference quality genome comprised of 17902 protein-coding genes derived from a single, representative Ascaris worm collected from 60 human hosts in Kenyan villages where pig husbandry is rare. Notably, the majority of human isolates (63/68) possessed mitochondrial genomes that clustered closer to the pig parasite Ascaris suum than to A. lumbricoides. Comparative phylogenomic analyses identified over 11 million nuclear-encoded SNPs but just two distinct genetic types that had recombined across the genomes analysed. The nuclear genomes had extensive heterozygosity and all samples existed as genetic mosaics with either A. suum-like or A. lumbricoides-like inheritance patterns supporting a highly interbred Ascaris species genetic complex. As no barriers appear to exist for anthroponotic transmission of these hybrid worms, a one-health approach to control the spread of human ascariasis will be necessary. We have exploited informatic pipelines to identify tandomly and/or interspersed repeats within the genomes of Angiostrongylus cantonensis, Loa loa, Wuchereria bancrofti, Strongyloides stercoralis, T.cruzi, and the various Schistoma spp. We have configured qPCR assays for each of these identified targets and have improved the limits of detection in validated assays. Some of these have been shown to be useful for the diagnosis of these infections in appropriate patient samples.