Affiliation:
1. Department
of Medicine
2. School of Public
Health, University of Minnesota, Minneapolis, Minnesota
55455
3. South Africa Medical Research
Council (NATAL), Durban-Overport 4067, South
Africa
Abstract
ABSTRACT
We
followed 93 subjects with amebic liver abscess (ALA) and 963 close
associate controls at 3-month intervals for 36 months to characterize
intestinal and humoral antibody responses to the amebic
galactose-inhibitable lectin and to determine whether immunity
developed to
Entamoeba histolytica
or
Entamoeba
dispar
infection following cure of ALA. We found that ALA subjects
had a higher prevalence and level of intestinal antilectin
immunoglobulin A (IgA) and serum anti-LC3 (cysteine-rich recombinant
lectin protein) IgA and IgG antibodies,
P
< 0.01 and
P
< 0.05, respectively, compared to controls. The
intestinal antilectin IgA antibody response was sustained over a longer
time period in ALA subjects (71.8% remained positive at 18
months and 52.6% at 36 months,
P
< 0.001
compared to 17.6% and 10.3% of controls, respectively).
ALA subjects were highly immune to
E. dispar
infection
throughout the study (0% infected at 6 and 36 months, compared
to 6.5% and 4.9% of control subjects, respectively,
P
< 0.05). Upon entry into the study, 6.3% of
ALA subjects were infected with
E. histolytica;
the incidence
of new
E. histolytica
infections in controls (as determined by
culture) was too low (1.4%) to determine whether ALA subjects
exhibited immunity to new infections. We found that stool cultures
every 3 months markedly underestimated the occurrence of new
E.
histolytica
infections, as 15.3% of controls seroconverted
after 12 months of follow-up. Unfortunately, under the field conditions
present in Durban, South Africa, enzyme-linked immunosorbent assay for
detection of lectin antigen in stool yielded unreliable results. In
summary, subjects cured of ALA exhibited sustained mucosal IgA antibody
responses to the amebic galactose-inhibitable lectin and a high level
of immunity to
E. dispar
infection. Determination of immunity
to
E. histolytica
following cure of ALA will require the use
of more sensitive and reliable diagnostic
methods.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
27 articles.
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