Seroprevalence taken as more coherent for the

Seroprevalence of 30.76%
as estimated by ESA in the present investigation was on lower side compared
with Sahu et al. (2015) who found 45% seropositivity against ESA among ocular
CC cases. In another study Sahu et al.
(2009) observed diagnostic level of antibodies against ES antigen to be present
in 88.2% sera samples taken from 34 confirmed NCC patients from Pondicherry.
Atluri et al. (2014) observed
antibody response to ES antigen in 22 (66.6%) out of 36 clinically confirmed
and radiologically proven NCC children in Chandigarh during a cohort study. Further
Molinari et al. (2002) observed 24.17
% seropositivity taking CSF of 91 patients with neurological disorder. In a
study conducted by Sailaja et al.
(2015), the researchers stated that the ES antigen was able to detect 4 out of
9 live cysts, 18 out of 61 degenerated cysts and 1 out of 6 calcified cysts in
human patients.

Comparison of the 15.38%
seroprevalence by MBA as
obtained in the present study was much less with that of 82% observed by Shukla
et al. (2008) who worked on 50
confirmed NCC patients at Lucknow.

In the present investigation also, the
seroprevalence of 30.76% as estimated by ESA could be
taken as more coherent for the reason that the ESA is being metabolite of the
live cyst(s) which reflects active infection of NCC in human patients
exhibiting clinical manifestations like epilepsy supported by investigation
reports. The use of ES antigens from heterologous sources (antigens prepared
from cysts other than that of Taenia
solium) in diagnosing NCC cases using serum and (or) CSF were documented
(Espindola et al., 2002; Molinari et al., 2002; Lopez et al., 2004).  Although
different levels of sensitivity and specificity were reported in various
studies (D’Souza and Hafeez, 1999; Arruda et al., 2005; Espindola et al., 2000,
2002, 2005; Atluri et al., 2009; Sahu et al, 2009), the scenario addressing the
number of patients with single/multiple lesions were not mentioned and it
should be evaluated in the Asian subcontinent where single cystic granuloma is
the commonest manifestation in NCC cases.

The observations on the
immunodominant bands against the antigens under study in SA could be compared
with Cho et al. (1987) who showed
that 1-11 (avg 6.3) bands exhibited by 20 out of 24 patients for SA. Shukla et al. (2008)
who observed prominent bands between 60 to 70 kDa and 40 to 45 kDa to be common
to membranes and scolices with 60% of patients’ sera recognized low molecular
weight immunoreactive bands between 18 to 25 kDa. Similarly, Neto
et al. (2007) observed that the
proteins with molecular weights of 200, 180, 120, 100, 95, 68, 65 and 26kDa
were the most reactive using SA. While the results obtained by Lisiane et al. (1999) showed bands of proteins
with molecular weights ranging from 97 to 13 kDa were recognized by
IgG-antibodies of patients with neurocysticercosis using SA. Barcelos et al. (2007) stated that, higher molecular
weight bands possess strong cross reaction and must not be used in the
immunodiagnosis of NCC cases.

Sahu et
al. (2010) observed the 43 kDa ES antigen to be reactive with CSF and serum
specimens from confirmed NCC patients with absolute specificity and a high
sensitivity (88.23% in serum and 89.28% in CSF), Ko and Ng (1998) observed 43,
58 and 66 kDa proteins of ES antigen to be more specific, Molinari et al. (1993) observed 22, 64 and 70 kDa
of ES antigen to be immunodominant. In our study also, the lower and medium
molecular weight proteins were recognized with a greater frequency. Reaction
to different antigenic fragments in the EITB from different studies may be due to host’s immune
response to the parasite, stages of development of the parasite in the brain,
localization and number of parasites in the CNS, persistency of the parasite,
existing immune evasive mechanisms, complex and diverse core epitopes of the
parasite, variation in the
preparation protocol of antigens, difference in their electrophoretic mobility
in the gel, higher molecular weight antigens maybe dimmers or trimers of lower
fragments, varied levels of glycosylation and sometimes the active sites might
have been cleaved off during antigen preparation leading to their non-detection
(Sciutto et al., 2007;
Flisser, 2002; Sahu et al., 2010). The variation can
be explained on the basis of animal models (pigs or mice) by experimentally
infecting them with eggs of Taenia solium
and observing for development of cysts and the variation in the antibody response
(Aluja et al, 1996).

In
our study, all the cases showed intraparenchymal lesions and the patients with
multiple lesions were found to be more seropositive than those with single
lesions. In general, extraparenchymal NCC is associated with high parasite antigen
levels and strong antibody reactions (Fleury et al.,
2011; Rodriguez et al., 2012). Wilson et al. (1991) observed undetectable
level of antigen and antibody in up to 40% of individuals with a single
degenerating parasite, while those with multiple viable cysts were consistently
seropositive. Low antibody titers were detected in serological tests employed
for patients with solitary lesions (Prabhakaran et al., 2007). In another study
from North India, ELISA was found to be more sensitive in paediatric NCC cases
with multiple lesions (Mandal et al., 2006). However in our study, no correlations
were found between seropositivity and location of lesions in different parts of
brain.