| dc.description.abstract | A cross sectional study was undertaken to determine the role
of intestinal immunoglobulin A (IgA) in prevention from, or
limitation of diarrhoea disease among normal, malnourished
and human immunodeficiency virus (HIV) seropositive children.
stools were collected from children aged less than 5 years
old, from which total IgA was determined by radial
immunodifusion and specific IgA by Enzyme-linked
immunosorbent assay (ELISA). Intestinal parasites were
identified by wet preparation and microscopy. Enteric
bacteria namely Salmonella, Shigella, Escherichia coli and
Campylobacter were isolated by culture on selective media
then identified by biochemical tests and slide agglutination
serotyping. Rotavirus was determined by ELISA test. Human
immunodeficiency virus was determined by an ELISA screening
test and confirmed by Western Blot.
Peripheral blood was collected from the children for
determination of T-helper (CD4) and T-suppressor (CD8)
lymphocytes by flow cytometry and phagocytic activity by
killed Candida albicans yeast cells.
A total of 55h children ~ere included in the stUdy, mean aqe
11.5 months, standard deviation 14.8 months and range 5 days
to 60 months. Malnourished children had diarrhoea of longer
duration (p=O.OOl) and more severity (p<0.04) than those well
nourished. Similar results have been reported in other
studies. Apart from total IgA which was higher in marasmic
children (p=O.Ol), specific IgA levels, phagocytic activity
and T-Iymphocyte counts were independent of nutritional
status. While there was no association between severity of
diarrhoea and either total IgA, T-Iymphocytes or phagocytic
activity, Rotavirus specific IgA (p = 0.05) and EPEe 086A:K61
(p = 0.01) was significantly higher in mild compared to
severe diarrhoea. It is therefore probable that prolonged and
severe diarrhoea in malnutrition may be a result of impaired
immune system.
There was a trend for increased total IgA levels (p=0.2) and
T-helper cell count (p=0.06) in breast fed children compared
to those mixed fed or bottle fed. Breast feeding may provide
a direct localized protective function in the gut or via
primed T-cells which regulate committed B-cells to produce
IgA.
When the presence of specific IgA was compared with enteric
pathogens, children had diarrhoea caused by different
organisms other than the one they had intestinal IgA antibody
to (p<0.05). This suggests that intestinal IgA may have a
protective role to play in the host's resistance to diarrhoea
disease. The occurrence of enteropathogens in neonates
suggest that passive immunity may be inadequate.
Total IgA, (p=O.3) and phagocytic activity, (p=O .1) were
reduced, though not significantly in HIV seropositive
children. The occurrence of enteropathogens was independent
of HIV serostatus and CD4 cell depletion. Absolute CD4
lymphocyte counts were low in HIV seropositive children with
severe diarrhoea (p=O.Ol). This suggests that CD4 lymphocytes
may have a role to play in limiting severity of diarrhoea in
HIV infection. Children of HIV seroposi tive mothers had
prolonged diarrhoea than those of HIV seronegative mothers
(p=O.06) regardless of their HIV status, and diarrhoea was
more common among those aged less than six months (p=O.02,
Odds ratio=4. 75). Probably HIV infection prevents passive
transfer of maternal immunity.
The r-esuLt.s cf this st.udy suggest that the presence of
intestinal IgA may have a role to play in protection against
diarrhoea in both normal and malnourished children. The role
of passive transfer of maternal immunity in HIV seropositive
mothers needs further investigation. | en |
