Neurocysticercosis (NCC), the infection of the central nervous system (CNS) caused by the
metacestode larva of Taenia solium, the pork tapeworm, is endemic in most developing
countries and identified as the most common cause of acquired epilepsy worldwide. The
parasites cause a chronic neuroinflammation and pathological studies reveal reactive
astrogliosis, fibrosis, angiogenesis, alteration of the brain blood barrier permeability and
overexpression of both inflammatory and anti-inflammatory cytokines. Yet to this end we poorly
understand the mechanisms underlying the pathology in NCC patients, and have minimal
clinical means to prevent neurological complications in these patients. Effective treatment for
NCC remains a challenge, as the severity of disease symptoms is thought to be a result of
pathologic inflammatory response induced by the degenerating larvae.
We have pioneered an in vitro model of T. solium larval development, from the infectious stage
(the oncosphere), through large 60-day post-oncospheres. During these stages and until the
parasite reaches a mature larva or cysticerci, the parasite itself changes its protein expression
profile, however we have little to no information on the molecules secreted by each stage.
TGF-β plays a pivotal role in a large spectrum of infections with protozoa and helminths.
Besides the importance of host TGF-β signaling in the regulation of host-parasite interactions,
much evidence has shown that helminth parasites might directly influence the TGF-β dependent
pathway via the expression of TGF-β receptor and ligand homologues. Based on these studies,
we will take advantage of our in vitro model and examine the excretory/secretory (E/S) products
of the different larval stages of development of T. solium to test for immunomodulatory
functions, starting with TGF-β. E/S from the five different stages of T. solium larval development
(oncosphere, postoncospheres at 15, 30 and 60 days of growth and mature cysts), to proteomic
analysis by mass spectrometry, characterize each stage’s secretome and compare the
spectrum of secreted molecules between the stages. We will interrogate this new resource to
identify homologues of members of the TGF-β superfamily. Additionally, E/S proteins from the
different development stages of the larvae will be fractionated using both gel filtration and anion
exchange Fast Protein Liquid Chromatography to provide a resource for use in subsequent in
vitro assays in order to functionally test for and identify new immunomodulators.
We will then test T. solium E/S for TGF-β like activity utilizing in the first instance a sensitive
TGF-β reporter cell line. Positive E/S will then have its fraction profile tested to narrow down the
identification of candidate molecules to screen in vitro, and the active fraction(s) will be subject
to mass spectrometry. Subsequently, E/S will be tested in in vitro cultures of naïve CD4+ Tcells
with IL-2 and anti-CD3 in order to assess the induction of the transcription factor Foxp3, that
indicates that these cells have been induced to Tregs by a TGF-β homologue or mimic.
Molecules with positive activity will be identified and recombinantly expressed, their activity will
be characterized using the reporter MFB-F11 bioassay and in in vitro regulatory T cell induction
assays.
To identify TGF-β mimic proteins in the T. solium larvae has the potential both to change our
understanding of parasite adaptation to the host and to develop possible therapies for immune
mediated disease. In addition, understanding developmental signals required for parasite
maturation may open new avenues for pharmaceutical treatment of infection.
