Immunity to schistosomiasis before puberty: humeral or cell mediated.

To determine if the cell mediated immunity, induced by T-helper type-1 lymphocytes (Th1) response, during schistosomiasis mansoni has the potential to protect against infection, intensities of infections and re-infections, reflected in the egg count were followed up to 20 months among 119 individuals aged 5-22 years (Ys) with different number of previous infections whose yearly levels and pattern of water contact were similar. They were classified into 5 groups. Delayed hypersensitivity skin tests (DHT) to adult schistosome excretory-secretary antigens (ESAgs) and anti-schistosomula (ESAgs) isotypes were measured on detecting re-infection. The group with a mean age of (8.6 +/- 2.6 Ys) and infected less than 5 times showed only 6.5 percentage reduction of the egg count (PREC) and low cellular and humoral responses. Th1-associated cellular (DHT) and antibody responses (IgG2, IgG3) to the five infections were significantly higher in the (13.5 +/- 1.4 Ys) than in (18 +/- 2.2 Ys) age group. This was reflected in significant difference in PREC; being 41.5% among the first and 13.5% among the second. Th2-associated antibody responses (IgG1, IgG4, IgE) went on rising as patients allowed for age and number of infections increased over 5, being significantly higher in the (19 +/- 1.8 Ys) than in (14 +/- 1.1 Ys) age groups with PREC 45.5% and 12.9% respectively. These results imply a substantial protective role for cell mediated immunity in the pre-puberty stage and provide evidence that Th1-based vaccination strategy can work if augmented.

Diagnosis of early pre-patent schistosomiasis by cystatin capture enzyme-linked immunosorbent assay.

To test the efficacy of detecting anti-Schistosoma mansoni cysteine proteinase antibodies (CP Abs) by cystatin capture (CC) ELISA in the diagnosis of prepatent schistosomiasis (before egg passing); 253 schistosome negative individuals were selected and divided into two groups. The first comprised 118 children whose first water contact occurred in March and April 1999 (primarily infected), and the second 135 individuals were previously treated for schistosomasis (re-infected). All the individuals were followed up triweekly by stool for detecting schistosome eggs and by serological tests for detecting antibodies against CP and anti-soluble egg antigens (SEA) by ELISA technique. CP seropositivity was detected in 92 from all examined individuals, out of them 38 were primarily infected (PI) children (20 of them were pre-patently treated), the rest; 54 were re-infected patients (28 out of them were pre-patently treated). The untreated (44) individuals from both groups were followed up till they passed eggs within 4 weeks and then were treated (post-patent). CP Abs were reassessed for the 92 patients after treatment, only 11 (12%) were still seropositive with marked decrease in optical density (O.D.) level than before treatment. Anti-SEA IgM Abs were sought in the 92 CP seropositive sera, and the seropositivity rate was lower in 38 PI children (5.3%) than in the 54 re-infected individuals (92.6%). The anti-SEA seropositivity rate in the PI children was 5% in the pre-patent and was 94.4% in the post-patent. None of the 161 CP seronegative individuals passed eggs up to 12 weeks.

Value of estimating intraocular antibody production in diagnosis of typical and atypical lesions of ocular toxoplasmosis.

Serum and aqueous humor (AH) samples were collected from 45 patients: 20 with typically active or reactivated retinal lesions of Toxoplasma (Group I), 16 with atypical lesions (Group II) and 9 with old quiescent scars (Group III). Also, serum and AH samples were collected from 10 patients with chronic toxoplasmosis without any ocular manifestation (Group IV). T. gondii specific IgG, IgA and IgM antibodies were measured by ELISA in AH and serum and the intraocular (local) antibody production was determined by calculating Goldman-Witmer coefficient (G.W.C.). IgG antibodies were the only class detected in all sera of patients with ocular and nonocular toxoplasmosis. An intraocular IgG antibody synthesis was confirmed in 95% and 37.5% of patients with typical (Group I) and atypical (Group II) posterior uveitis respectively and in none of either patients with quiescent scars (Group III) or the ophthalmologically free patients (Group IV). As regard the typical active lesions, the sensitivity of the IgG assay (95%) was higher than that of IgA (60%) and IgM (5%) assays. Beside the conclusion that AH analysis to detect local antibody production is more reliable than the estimating of serum antibodies for the diagnosis of ocular toxoplasmosis, the detection of AH specific antibodies in 6 atypical cases, who were treated successfully by antitoxoplasmic therapy, represent a help to increase the number of uveitis cases in which specific treatment can be established.

Evaluation of the role of Ancylostoma caninum in humans as a cause of acute and recurrent abdominal pain.

Ancylostoma caninum is responsible for cases with eosinophilic enteritis (EE) and unexplained abdominal pain with peripheral eosinophilia in man. Ninety-five patients with obscure acute or recurrent abdominal pain and ten asymptomatic healthy parasite free were subjected to thorough history taking, clinical examination, sonography, routine laboratory investigations and serotesting by IgG ELISA to detect antibodies to excretory/secretory (ES) antigens of adult A. caninum and by IgG and IgG4 Western blot (W.B.) to detect antibodies to Ac68 antigen. Eleven male patients (11.6%) (5 with acute abdomen, 3 diagnosed as appendicitis and 3 had recurrent mild to moderate abdominal pain) fulfilled the criteria of case definition of human enteric infection with A. caninum (G.I). The study also detected human hookworm infection in 14 patients (G.IIb) other parasites in 34 patients (GIIc) and 36 patients had no parasites (G.IIa). Although 3 patients from group I were diagnosed as appendicitis and were dealt with surgically, the pain recurred and mebendazole only put an end to the patient's complaints. The obtained appendices of these operated cases showed marked eosinophilic infiltration but no adult canine hookworms were detected. IgG ELISA was positive in 72.7%, 8.3%, 100%, 23.5% and 0% in groups and control respectively. IgG and IgG4 W.B. did not increase the sensitivity but IgG4 W.B. elevated specificity to 100% excluding those with HH infection (Group Iib) who showed 100% cross-reactions. Stool analysis was the only differentiation between these two types of hookworms. These findings confirmed the presence of human enteric infection with A. caninum as clinical entity in the study community and referred to its value in differential diagnosis of the obscure abdominal pain.