A novel small heat shock protein 12.6 (HSP12.6) from Brugia malayi functions as a human IL-10 receptor binding protein

Abstract

Phage display cDNA expression library of the third stage larvae (L3) of Brugia malayi was screened for identifying target(s) that bound to the human interleukin-10 receptor (huIL10R). This iterative screening identified an insert that showed significant homology to Caenorhabditis elegans HSP12.6. The gene was designated B. malayi HSP12.6 (BmHSP12.6) and has orthologues in several gastrointestinal nematode genome (Ancylostoma caninum, Ascaris lumbricoides and Ascaris suum) but the gene or gene product has not been studied further in these parasites. Structural analyses of BmHSP12.6 showed that it has a highly conserved alpha-crystallin central domain that is characteristic of other small heat shock proteins (HSPs). BmHSP12.6 has a short N-terminal domain and an unusually small C-terminal domain flanking the crystallin domain suggesting that this protein belongs to a novel class of small HSPs. BmHSP12.6 appears to be differentially transcribed with highest expression in the vertebrate stages of the parasite (L4, adult and mf) compared to its mosquito vector stage (L3). More importantly recombinant BmHSP12.6 bound to huIL10R in a dose dependent fashion and inhibited the binding of human IL-10 (huIL10) to huIL10R in vitro. rBmHSP12.6 also enhanced the growth and proliferation of MC/9 mast cells in vitro similar to huIL10. This study thus describes a novel small HSP from B. malayi that has the capacity to bind to huIL10R, block binding of huIL10 to huIL10R and function similar to huIL10.

Biochemical Characterization and Evaluation of a Brugia malayi Small Heat Shock Protein as a Vaccine against Lymphatic Filariasis

“…Similar motifs were also observed in human IL-10 further confirming the previous findings that BmHsp12.6 may mimic human IL-10 function [10].…”

“…These functions may be critical for survival of the parasite in the vertebrate host. Our previous studies reported that BmHsp12.6 can bind to human IL-10R and activate IL-10 mediated effects in vitro [10]. In the present study we show that the IL-10R binding region of BmHsp12.6 resides in its N-terminal sequences.…”

“…However, we did not identify the peptide sequence of BmHsp12.6 that binds to IL-10R. Nevertheless, our studies showed that rBmHsp12.6 can induce IL-10-like proliferative effects in vitro in MC/9 cell lines [10]. In the present study we mapped the IL-10R binding region of BmHsp12.6 and evaluated if this binding region has IL-10 like activity.…”

The role of small heat shock proteins in parasites

“…Finally, in vitro studies of the BmHSP12.6 protein of B. malayi have demonstrated that this protein binds to the human IL-10 receptor (huIL10R) in a dose-dependent manner, thus inhibiting the binding of human interleukin-10 (huIL10) to its receptor. In addition, rBmHSP12.6 stimulated the in vitro growth and proliferation of MC/9 mast cells in a manner similar to hulL10, the native inducer of mast cells (Gnanasekar et al 2008).…”

“…In Schistosoma mansoni, the p40 protein is expressed abundantly in eggs and miracidia and at low levels in adult males or females (Nene et al 1986). In B. malayi, the mRNA of the BmHSP12.6 gene can be detected in all developmental stages, but its transcription was predominant in postinfective stages; indeed, the highest expression levels were found in microfilariae, L4 larvae, and adult parasites (Gnanasekar et al 2008). In O. ostertagi, the highest levels of transcription of the Oo-HSP18 gene were detected in adult parasites and were found to be 170, 757, and 413 times higher than the levels detected in L3 larvae, non-enveloped L3, and L4 larvae, respectively.…”