Increased ShTAL1 IgE responses post- Praziquantel treatment may be associated with a reduced risk to re-infection in a Ghanaian S. haematobium-endemic community
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Date
2022
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Journal ISSN
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Publisher
PLOS NEGLECTED TROPICAL DISEASES
Abstract
Background
Evidence from recent studies in Schistosoma mansoni-endemic areas show an age-associated
immunity that is positively correlated with IgE titres to Schistosoma mansoni-specific
tegumental allergen-like protein 1 (SmTAL1). The structural homology between SmTAL1
and the S. haematobium-specific TAL1 (ShTAL1) has been verified, yet it remains unclear
whether similar age- and immune-associated trends characterize ShTAL1. This communitybased
intervention study was conducted to assess whether ShTAL1IgE responses posttreatment
with praziquantel (PZQ) might be associated with a reduced risk to re-infection
with S. haematobium.
Methodology/Principal findings
This study was conducted at Agona Abodom, Central Region, Ghana, and involved 114 participants
aged 6 to 55 years. EDTA blood samples were collected at baseline and 7 weeks
after PZQ treatment (Follow-up). Baseline and Follow-up titres of specific IgG1, IgG4, and
IgE antibodies to the S. haematobium-specific adult worm antigen (ShAWA), the Sh-specific
soluble egg antigen (ShSEA), and the Sh-specific tegumental-allergen-like 1 protein
(ShTAL1) in plasma samples were measured using sandwich ELISA. Participants at both
time points also provided stool and urine for helminth egg detection by microscopy. Prevalence
of S. haematobium at baseline was 22.80%, and decreased to 3.50% at Follow-up.The egg reduction rate (ERR) was 99.87%. Overall plasma levels of ShTAL1-IgE increased
7 weeks post-PZQ treatment, and with increasing age; whiles S. haematobium infection
prevalence and intensity decreased. For S. haematobium-infected participants who were
egg-negative at Follow-up (N = 23), minimal median levels of ShTAL1-IgE were observed
for all age groups prior to treatment, whilst median levels increased considerably among
participants aged 12 years and older at Follow-up; and remained minimal among participants
aged 11 years or less. In the univariate analysis, being aged 12 years or older implied
an increased likelihood for ShTAL1-IgE positivity [12–14 years (cOR = 9.64, 95% CI = 2.09–
44.51; p = 0.004); 15+ years (cOR = 14.26, 95% CI = 3.10–65.51; p = 0.001)], and this
remained significant after adjusting for confounders [12–14 years (aOR = 22.34, 95% CI =
2.77–180.14; p = 0.004); 15 years (aOR = 51.82, 95% CI = 6.44–417.17; p < 0.001)]. Conversely,
median ShTAL1-IgG4 titres were hardly detectible at Follow-up.Conclusions/Significance
These findings demonstrate that increased IgE levels to ShTAL1 7 weeks after PZQ treatment
could be associated with a reduced risk to re-infection, and adds to the large body of
evidence suggesting a protective role of the treatment-induced ShTAL1 antigen in schistosomiasis
infections. It was also quite clear from this work that apart from being persistently
S. haematobium-positive, elevated ShTAL1-IgG4 levels at Follow-up could be indicative of
susceptibility to re-infection. These outcomes have important implications in vaccine development,
and in shifting the paradigm in mass chemotherapy programmes from a ‘one-sizefits-
all’ approach to more sub-group-/participant-specific strategies in endemic areas.
Description
Research Article
Keywords
Schistosoma mansoni-specific tegumental allergen-like protein 1 (SmTAL1), re-infection, immunity, EDTA blood, Ghana