Comparative Analysis of Glycosylated and Nonglycosylated Filarial Homologues of the 20-Kilodalton Retinol Binding Protein fromOnchocerca volvulus(Ov20)

Abstract

Ov20 is a structurally novel 20-kDa retinol binding protein secreted by Onchocerca volvulus. Immunological and biological investigation of this protein has been hampered by the inability to maintain O. volvulus in a laboratory setting. In an effort to find a system more amenable to laboratory investigation, we have cloned, sequenced, and expressed cDNA encoding homologues of Ov20 from two closely related filarial species,Brugia malayi (Bm20) and Acanthocheilonema viteae (Av20). Sequence comparisons have highlighted differences in glycosylation of the homologues. We present here an analysis of mouse immune responses to Ov20, Bm20, and Av20. The results suggest a strong genetic restriction in response to native Bm20 that is overcome when recombinant, nonnative material is used. Reactivity of human filarial sera to the three recombinant proteins confirmed previous specificity studies with Ov20 but highlighted important differences in the reactivity patterns of the O. volvulus and B. malayi homologues that may be due to differences in glycosylation patterns. Ov20 is a dominant antigen in infected individuals, while Bm20 is not. The availability of the B. malayi homologue enabled us to use defined murine reagents and inbred strains for genetic analysis of responsiveness in a way that is not possible for Ov20. However, the close sequence similarity between Ov20 and Av20 suggests that the A. viteae model may be more suited to the investigation of the biological functions of Ov20.

Use of the recombinant Onchocerca volvulus protein Ov20/OvS1 for the immunodiagnostic differentiation between onchocerciasis and mansonelliasis and for the characterization of hyperreactive onchocerciasis (sowda)

“…The findings of this study support previous reports on the specificity of Ov20 protein in filarial infections (Bradley et al 1993;Nirmalan et al 1999). Nirmalan et al (1999) reported differences in the reactivity pattern of O. volvulus and Brugia malayi Ov20 homologues that may be due to differences in glycosylation pattern. It may be interesting to establish the possible Ov20 homologues in the Mansonella spp.…”

“…were resident is unlikely because the only vector of O. volvulus in this region is S. neavei with a greatly limited dispersal range (Mpagi et al 2000a). The findings of this study support previous reports on the specificity of Ov20 protein in filarial infections (Bradley et al 1993;Nirmalan et al 1999). Nirmalan et al (1999) reported differences in the reactivity pattern of O. volvulus and Brugia malayi Ov20 homologues that may be due to differences in glycosylation pattern.…”

Immunological genomics of Brugia malayi: filarial genes implicated in immune evasion and protective immunity

“…Surface labelling of adult B.malayi gives weaker and variable iodination of a 20 kDa protein related to Ov20, a much more prominent surface antigen on adult O. volvulus (45). Including the conserved signal sequence, both Bm-FAR-1 and Ov20, are 178 amino acids in length, but the proteins differ in 26/160 amino acids (84% identity) over the mature polypeptide (46). Three of these substitutions replace asparagine residues found in Ov20, nullifying potential glycosylation sites, and although one new site is observed in Bm-FAR-1, this is thought not be used in the native product.…”

Ligand binding properties of two Brugia malayi fatty acid and retinol (FAR) binding proteins and their vaccine efficacies against challenge infection in gerbils

“…As with all parasitic nematodes, the etiological agents of LF such as Wuchereria bancrofti , Brugia malayi and Brugia timori , and that of river blindness, Onchocerca volvulus , possess limited lipid metabolic pathways and hence rely on lipids scavenged from their hosts [ 2 ]. Several structurally novel families of lipid-binding proteins in nematodes have been reported [ 3 ], including the fatty acid- and retinoid-binding protein family (FAR) that have been identified from many species of filarial nematodes including those from the genera Onchocerca , Brugia , Wuchereria , Loa , Acanthocheilonema and Litomosoides [ 4 ]. FAR proteins represent a structurally novel class of approximately 20 kDa lipid-binding proteins that are only found in nematodes [ 5 ], isoforms of which are known to be differentially expressed during development of parasitic and free-living species [ 5 – 7 ].…”