The relationship between Trichuris trichiura transmission intensity and the age-profiles of parasite-specific antibody isotypes in two endemic communities.

The present study compares parasite-specific antibody responses in two Caribbean communities with high and low levels of Trichuris trichiura transmission. The age-dependency of antibody levels suggest that IgG1 and IgG2 levels relate to the current intensity of infection (as assessed by density of eggs in stool (e.p.g.) and reflect the age-intensity profile at the population level. IgG4, IgE and IgA levels persist into early adulthood and the subsequent decline is gradual. In the low transmission area, lower infection levels are reflected in lower parasite-specific antibody levels (of all isotypes) in the community as a whole. Despite a significantly greater past experience of infection in the high transmission area, antibody levels are not maintained at significantly higher levels throughout adulthood. The production of IgA appears to require a threshold for triggering, and a vigorous IgA response is maintained into early adulthood only in the high transmission village where peak intensity is greatest and the age-convexity of intensity is most marked. Experimental and theoretical studies focusing on the dynamic nature of host-helminth interactions in hosts exposed to high and low infection levels, and the putative role of acquired immunity, are discussed in relation to the data presented.

Age-dependency of infection status and serum antibody levels in human whipworm (Trichuris trichiura) infection.

This study examines the age-dependency of the relationships between human infection with whipworm (Trichuris trichiura) and parasite-specific antibody level measured by ELISA against an extract of adult worms after preincubation of the sera with Ascaris lumbricoides adult worm extract. The convex age-profile of parasite infection intensity is shown to be mirrored by an age-dependent change in age-class mean levels of IgG (all subclasses except IgG3), IgA, IgM and IgE. Mean antibody levels rise with increasing acquisition of infection in childhood and decline as the intensity of infection falls in adulthood. Immunoblot analysis of selected sera from different age-classes indicates that antigen recognition is similarly dependent on infection intensity. In individual children, antibody levels correlate positively with acquisition of infection, consistent with a simple model of antigen dosage specifying the magnitude of the humoral immune response. In adults, IgG4 correlates positively and IgA negatively with intensity of infection, suggesting involvement of these isotypes in functional roles of immune blockade or effector mechanisms, respectively.

Vitamin E, lipid fractions, and fatty acid composition of colostrum, transitional milk, and mature milk: an international comparative study.

Triglycerides, cholesterol, fatty acid composition, and tocopherols were determined in colostrum, transitional milk, and mature milk in St Lucia. With progress of lactation, triglycerides and percentage medium-chain fatty acids increased whereas tocopherols, cholesterol, and percentage long-chain polyunsaturated fatty acids decreased. These changes reflect augmented de novo synthesis of fatty acids (8:0, 10:0, 12:0, and 14:0) in the mammary gland and a tendency of increasing fat-globule size as milk matures. Transitional and mature milks, but particularly colostrum, contained higher concentrations of components considered to be derived from the fat-globule membrane (cholesterol, tocopherols, percentage long-chain polyunsaturated fatty acids) compared with those reported for Western countries. Percentage medium-chain fatty acids in mature milk was two to three times higher than in developed countries. Differences from data from studies in Western countries are discussed in relation to analytical methods and possible consequences for lipid digestion, lipid absorption, growth, and brain development.

Seroepidemiological study of the transmission of the mumps virus in St. Lucia, West Indies.

A seroepidemiological study of the prevalence of mumps virus specific antibodies reveals a pattern of endemic persistence on the island of St Lucia in the West Indies. In the unvaccinated population the proportion seropositive rose rapidly in the child age classes to attain a stable plateau close to unity in value in the teenage and adult age groups. The average age at infection was estimated to be between 3 and 4 years of age and the average duration of detectable levels of maternally derived antibodies was approximately 3 months. Analyses based on mathematical models of the transmission dynamics of the virus suggest that in excess of 75% of each cohort of 1- to 2-year-old children must be effectively immunized to eliminate mumps virus transmission. A mumps radial haemolysis test, developed for quantitative measurements of antibody, is discussed.

Predisposition to Trichuris trichiura infection in humans.

The study examines the distribution of Trichuris trichiura infection in a village community in St Lucia, West Indies. The infection intensity of the same age-stratified population was assessed (by drug expelled worm burden and faecal egg count) at the initiation of the study, and after 17 months of reinfection following treatment. The frequency distribution of worm numbers per person was similar at both periods of sampling. There was a significant correlation between the initial infection intensity of an individual, and the intensity acquired by the same individual following the 17 month period of reinfection. This relationship was observed in a broad range of host age classes. The study provides firm evidence that individuals are predisposed to heavy (or light) T. trichiura infection.

Epidemiology and population dynamics of Ascaris lumbricoides and Trichuris trichiura infection in the same community.

The gastrointestinal helminth infection status of an age-stratified sample from a single Caribbean community was assessed using anthelmintic expulsion techniques. The same sample was re-assessed in a similar manner after a 17 month period of re-infection. The age-prevalence profile of Ascaris lumbricoides was convex while that of Trichuris trichiura was asymptotic. The age-intensity profiles of both species were convex. These differing patterns are attributed to differences in the absolute worm burdens of the 2 species. The frequency distributions of infection intensity were similar for both species, and largely independent of host age. The basic reproductive rate of A. lumbricoides (Ro = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (Ro = 4-6), implying that the latter is intrinsically more resistant to control. Individual hosts were predisposed to high (or low) intensity infection with either species, although predisposition to both species simultaneously was not conclusively demonstrated. Further studies are required to determine the cause of these observations.