Trehalose-6-phosphate-potent anti-onchocerciatic agent.

Onchocerciasis is a disease that engages the attention of most researchers. Presently, there is not an ideal onchocerciatic agent, hence the search must continues. Consequently alpha, alpha-trehalose-6-phosphate was synthesised and assessed for onchocerciatic activity against O. volvulus; using diethylcarbamizine citrate as the control drug. Results from this study showed that alpha, alpha-trehalose-6-phosphate is a glucose analogue with effective micro and macro-filaricidal agent, better than that of the control drug. The inhibitory action of this compound on enzyme trehalase is a postulate for the mechanism of action of trehalose-6-phosphate. The structure-activity relationship of this new compound is fully discussed. This study postulates that this compound could be used to eradicate onchocerciasis both in man and animals.

Elevated serum angiotensin-converting enzyme activity in onchocerciasis.

Our objective was to measure serum angiotensin-converting enzyme (ACE) activity in patients with onchocerciasis. Serum ACE activity is commonly used in the diagnosis and follow-up of patients with sarcoidosis. However, serum ACE activity can also be elevated in a number of other granulomatous disorders. In onchocerciasis, a parasitic disease affecting millions of people in Africa and Central and South America, granulomatous tissue around adult worms has been identified, yet raised serum ACE activity has not been reported so far. We measured serum ACE activity in serum samples from 42 onchocerciasis patients and 39 endemic controls previously enrolled in two studies concerning the side effects after invermectin treatment in Sierra Leone, West Africa. The mean ACE activity in the patient group was 53.8 units/liter (S.D. 19.8) compared with 35.2 units/liter (S.D. 14.0) in the control group (p < 0.0001). Nine of 42 patients had elevated ACE activity (mean of the endemic controls +/- 2 S.D.) compared with 1 of 39 controls (p = 0.01). Sensitivity and specificity of elevated ACE in serum from onchocerciasis patients from Sierra Leone was 21 and 97%, respectively. ACE activity was not related to the microfilarial skin load or development of side effects after ivermectin treatment. Serum ACE activity can be elevated in onchocerciasis. Clinicians should be aware of this phenomenon when determining serum ACE activity in persons from endemic areas.

Pathogenesis of onchocercal dermatitis: possible role of parasite proteases and autoantibodies to extracellular matrix proteins.

We examined the immunogenicity of various connective tissue proteins in patients with chronic onchocercal dermatitis and the effect of filarial proteases on this host-parasite interaction. Sera from patients with onchocerciasis reacted strongly with cuticular collagens from filarial parasites and with mammalian laminin. Some sera also contained antibodies to elastin and collagen type IV, but none reacted with collagen types I-III or fibronectin. This pattern of reactivity was characteristic for onchocerciasis: sera from patients with mansonellosis reacted strongly with collagen type IV but only weakly with laminin. Reactivity with mammalian laminin or collagen could not be absorbed with cuticular proteins from filarial worms and vice versa. Digestion fragments of laminin treated with filarial proteases retain antigenic determinants recognized by sera from patients with onchocerciasis. In contrast, proteases from Onchocerca volvulus adults and microfilariae drastically decreased the reactivity of the same sera with collagen type IV. These results indicate that filarial proteases may contribute to the pathogenesis of chronic onchocercal dermatitis, directly, by enzymatically destroying connective tissue of the skin, and indirectly, by triggering autoimmune responses to self-determinants on connective tissue proteins that are normally hidden within the supramolecular structure of the extracellular matrix complex.

Identification of circulating parasite acetylcholinesterase in human and rodent filariasis.

In the present study, the enzyme acetylcholinesterase (AChE) from filarial parasites was identified in sera from humans infected with Onchocerca volvulus as well as in Mastomys natalensis infected with Brugia pahangi. The enzyme was present in immune complexes precipitated with cold 4% polyethylene glycol. The infected sera showed 3-4 times more AChE activity than did normal sera, and enzyme activity could be demonstrated in 5% polyacrylamide gels by specific staining. The enzyme from infected serum showed 3 times more activity when acetylthiocholine was used as the substrate as compared with butyrylthiocholine, whereas the enzyme activity present in normal serum was low and did not show this substrate specificity. Immunoprecipitation assays confirmed the presence of anti-AChE antibodies in the infected serum. The enzyme was further analysed by enzyme-linked immunosorbent assay and immunoblotting with rabbit antibodies to B. malayi AChE. Immunoblotting of the B. pahangi-infected serum revealed two closely located bands at about 200 kDa and one 95-kDa band, whereas in O. volvulus-infected serum, only one specific band was observed at about 200 kDa. The identification of parasite AChE may be particularly useful for diagnosis of the disease or for the study of the involvement of this enzyme in the host-parasite relationship.

Hydrolytic activity of an onchocercoma.

The onchocercoma or nodule produced by the nematode Onchocerca volvulus (Filarioidea) in the skin of patients suffering from onchocerciasis has not been examined by histochemical techniques. In this work we have used histochemical techniques to evaluate 5 hydrolytic enzymes, namely phosphatases, esterases and beta-glucuronidase. The results show increased enzymatic activity at the sites of major metabolic activity and within reactive cells including macrophages (mc) and giant cells (gc) of the onchocercoma.

Hydrolytic activity of an onchocercoma

The onchocercoma or nodule produced by the nematode Onchocerca volvulus (Filarioidea) in the skin of patients suffering from onchocerciasis has not been examined by histochemical techniques. In this work we have used histochemical techniques to evaluate 5 hydrolytic enzymes, namely phosphatases, esterases and beta-glucuronidase. The results show increased enzymatic activity at the sites of major metabolic activity and within reactive cells including macrophages (mc) and giant cells (gc) of the onchocercoma

Serum aspartate and alanine aminotransferase in filariasis.

Serum aspartate aminotransferase level in filarial patients was estimated. The level was compared against the level of the same enzyme in non-filarial patients. Similarly estimated and compared was the level of serum alanine aminotransferase in the same groups of subjects. It was found that there was a mild but significant elevation of aspartate aminotransferase level above the normal level, in filarial patients in Nigeria. However, no concomitant elevation of alanine aminotransferase level was observed.

Histochemical enzyme variation in Onchocerca volvulus microfilariae from rain-forest and Sudan-savanna areas of the Onchocerciasis Control Programme in West Africa.

Histochemical staining methods for acid phosphatase were used to study the differences among microfilariae of various West African strains of Onchocerca volvulus in both forest and Sudan-savanna onchocerciasis zones. The results have shown statistically significant differences in the staining patterns of microfilarial populations in the two zones. In the rain-forest areas, where onchocerciasis is transmitted by Simulium yahense, S. sanctipauli, S. soubrense and S. squamosum, there were no significant differences of microfilarial staining patterns in patients, by age and sex, between the three Simulium-Onchocerca complexes studied. There was a close relationship between the "strain differences", as revealed morphoenzymatically, and the clinical picture of the disease in both the forest and the Sudan-savanna zones. The present findings are in favour of the hypothesis that there are intrinsic differences in the strains of the parasite occurring in the two areas. The application of the histochemical means of parasite characterization appears to be a useful tool in differentiating strains of O. volvulus and could contribute towards a better understanding of the epidemiology of human onchocerciasis in different bioclimatic zones where the disease is endemic.