CD5+B lymphocytes are the main source of antibodies reactive with non-parasite antigens in Trypanosoma congolense infected cattle

Mice infected with African trypanosomes produce exceptionally large amounts of serum IgM, a major part of which binds to non-trypanosome antigens such as trinitrophenol and single-strand DNA. In this paper, we describe that in cattle infected with Trypanosoma congolense and T. vivax, similar antibodies are found, although they bind mainly to protein antigens, such as Beta-galactosidase, ovalbumin and ferritin. The parasite non-specific IgM antibodies appear around the same time as the parasite-specific antibodies, but their origin and function are not clear. We tested the hypothesis that CD5+ B cells (or B-1 cells), which increase during trypanosome infections in cattle, are responsible for production of antibodies to non-trypanosome antigens. Splenic CD5+ and CD5- B cells from infected cattle were sorted and tested in a single cell blot assay. The numbers of immunoglobulin-secreting cells were similar in both B-cell populations. However, antibodies with reactivity for non-trypanosome antigens were significantly more prevalent in the CD5+ B-cell fraction and were exclusively IgM. The preference for production of these antibodies by CD5+ B cells and the expansion of this subpopulation during infections in cattle, strongly suggest that CD5+ B cells are the main source of trypanosome non-specific antibodies. We propose that these antibodies are natural, polyreactive antibodies that are predominantly secreted by CD5+ B cells. Since B-1 cells are up-regulated in many states of immune insufficiency, the immunosuppression associated with trypanosome infections may be responsible for the increase of this subset and the concomitant increase in trypanosome non-specific antibodies

Escherichia coli 0157: H7 reservoir, transmission, diagnosis and the African situation: a review

Objectives: To provide an overview of the current understanding of verotoxigenic Escherichia coli 0157:H7 (VTEC) and to describe clinical picture, reservoir, transmission and diagnosis and African situations of VTEC. Data source: A literature review was performed of major published series between 1980 and 2001 inclusive, using the PUB MED and MEDLINE search. Some earlier published series were also reviewed in instances where they directly led to the understanding of current review. Study selection: Data from laboratory studies on cultural and isolation, serological and molecular techniques are summarised in this review. Results: Verotoxigenic Escherichia coli 0157:H7 (VTEC) is an important cause of uncomplicated diarrhoea, bloody diarrhoea (BD) and haemolytic uremic syndrome (HUS) in developed countries. The incidence and importance of 0157: H7 (VTEC) infections in most developing countries are not known; however, 0157: H7 (VTEC) cases have been isolated from many sporadic cases of diarrhoea, BD and HUS, while several cases have also been associated with diarrhoeal disease outbreaks in Africa. Conclusion: The morbidity and mortality associated with several recent outbreaks of VTEC disease have highlighted the threat these organisms pose to public health. For this reason, there is an increasing demand for improved diagnostic procedures for detection of VTEC in clinical specimen and in particular, in foods such as meat and dairy products in developing countries. (East African Medical Journal: 2003 80(5): 271-276

Inference of population of origin of individual animals from different Small East African goat populations using microsatellite markers

A study was conducted to determine the population membership of individual goats from seven Small East African goat strains using microsatellite genotype information. The populations were Maasai, Ugogo, Sukuma, Ujiji, Coastal, Mbeya and Newala goats. The number of individuals per population ranged from 40 to 50 and for each individual, 19 microsatellite loci were analysed. Three approaches were used to determine the affiliation of individuals to their source populations: an allele sharing distance matrix which was used to construct a phylogenetic tree of individual animals based on inter-individual genetic distances, individual assignment tests using a Bayesian statistical approach and maximum likelihood approach. The phylogenetic tree with individual animals as the taxonomic units showed that only individuals from Coastal (83%) and Newala (94%) goats were assigned to their own population cluster. Individuals from Maasai, Ujiji, Ugogo, Sukuma, and Mbeya populations did not show population-specific clusters. For the Bayesian method, the proportion of individuals assigned into their correct population of origin ranged from 85.5% (for Sukuma and Ugogo) to 100% (for Newala and Mbeya). For the maximum likelihood method, the proportion of individuals correctly assigned to their source populations ranged from 64.6% (Ugogo goats) to 100% (Newala goats). The breed assignment test based on the Bayesian method was found to be more efficient in allocating individuals to their source populations, followed by the maximum likelihood method