(Eh) y metanólico (Em) de Pera distichophylla sobre un aislado de ...

M. T. GALáN-PUCHADES and A. OSUNA
in an increase of T. cruzi parasitaemia, precisely
one of the risks favouring vertical transmission.
Additionally, helminths can also contribute to a
lower IFN-g production via a predominant Th-2
response in pregnant women. Therefore, it would
be interesting to evaluate the helminthological
status of chagasic pregnant women and its possible
influence on vertical transmission.
10
DISCUSSION
In order to address the questions of whether
helminth infection could affect the susceptibility to
subsequent co-infection with T. cruzi, and whether
a changing environment and cytokine profile
induced by worms may influence the outcome of
CD compared with hosts exclusively infected with
T. cruzi, it was found that the presence of helminths
modifies both the susceptibility and, in most cases,
the course of CD.
Concerning susceptibility, in all the studied hosts
(humans, mice, dogs and primates) the presence
of worms increases the likelihood to acquire CD
mainly in the helminth chronic phase. In addition,
co-infection seems to lengthen survivorship of coinfected
hosts compared with those only harboring
T. cruzi. The presence of helminths also tends to
increase T. cruzi parasitaemia and certain helminths
may even improve the health status of chagasic
hosts.
One of the main implications of these findings
is that helminth co-infections could potentially
modify the course of CD among patients with the
same T. cruzi DTU (discrete typing units) (Monteiro
et al., 2007).
In the last two decades, studies explaining
severe forms of CD have mainly been based on
immunological findings (Dutra et al., 2005, Rodrigues
et al., 2010). Chagasic myocarditis is
thought to be due to the presence of parasites in
the lesions. However, an unbalanced immune homeostasis
can trigger parallel autoimmune phenomena
which increase the immune response,
thus worsening the outcome of the disease (Gutierrez
et al., 2009). Several results evidence that an
exacerbated Th1-like specific immune response
against T. cruzi with high levels of IFN-γ and low
levels of the anti-inflamatory cytokine IL-10 is established
in T. cruzi-infected individuals present-
ing cardiac disease (Gomes et al., 2003). In addition,
there is some limited evidence regarding the
role of Th17-mediated responses to T. cruzi. The
IL-17 produced during the acute phase of CD controls
cardiac inflammation by modulating the Th1
response, and this pro-inflammatory IL-17 is also
required for the elimination of T. cruzi (Guedes et
al., 2010; Miyazaki et al., 2010). In contrast IL-
27, which suppresses Th17 responses, is beneficial
for the host during T. cruzi infection (Yoshida
and Miyazaki, 2008).
Surprisingly, there is no mention in the literature
that evaluates the possible role of helminth
infections in human CD when helminths are able
to suppress all types (Th1, Th2, and Th17) of responses
(see ref Osada and Kanazawa, 2010).
Considering the classical Th1/Th2 paradigm, it is
reasonable to speculate that a helminth-induced
Th2 response with production of IL-4, IL-5, IL-6
and IL-10 skewing with downregulation of Th1
immune responses could result in an amelioration
of Th1 diseases, such as CD. As IL-4 is known to
suppress Th17 development (Romagnani, 2006), a
Th17 response could also be suppressed as well as
Th1 response in helminth-infected hosts. In fact,
certain helminth infections reduce IL-17 mRNA
by MLN cells and inhibit IL-17 production (Elliot
et al., 2008). This is of relevance when considering
persistent parasites such as helminths which
are widely distributed in humans in developing
countries (Maizels et al., 1993), where they coexist
with T. cruzi. Wormy populations are exposed to
two potential risks, namely an increased susceptibility
to T. cruzi and a yet unresearched course of
the disease. All of this should prompt research on
the possible epidemiological relevance of helminth
infections and the impact when controlling them
on the incidence or the pathogenesis of CD. The
presence of helminth co-infections may represent
a much more important challenge for public health
than recognized until now.
In other co-infections of human parasites such
as malaria and hookworms, it has been stated
that it would be possible to define co-infection
as a specific “disease”, separate from malaria by
itself, or hookworm by itself (Payne et al., 2009),
and this may also hold true for CD and helminths.
Thus, gathering more reliable data on the true
parasitological status of all chagasic patients would
be desirable.
Rev. Ibero-Latinoam. Parasitol. (2012); 71 (1): 5-13