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A cocktail of recombinant Onchocerca volvulus antigens for serologic diagnosis with the potential to predict the endemicity of onchocerciasis infection.

We report here the evaluation of the potential of a serologic test to determine the endemicity of onchocercal infection in hyper, meso, and hypoendemic communities by the detection of antibodies to a cocktail of recombinant antigens. Parasitologic parameters of infection prevalence and intensity were compared with serologic results. Infection prevalence by serology was consistently but not significantly higher than that defined by parasitology. Differences between the communities defined by microfilarial load (CMFL) and a measurement of Onchocerca volvulus-specific antibody levels (serologic index [SI]) were similar. When stratified by age, differences were more significant in the younger age groups. If a sentinel population of 5-15-year-old individuals was used to compare communities, all could be equally ranked by serologic and parasitologic parameters. The SI of the sentinel population gave a better distinction between each community than the SI of the whole and would be sufficiently sensitive to measure the changes in endemicity that would be required for onchocerciasis control programs.

Adolescent↗

Analysis of Wuchereria bancrofti infections in a village community in northern Nigeria: increased prevalence in individuals infected with Onchocerca volvulus.

Infections with Wuchereria bancrofti causing lymphatic filariasis still represent one of the major health problems in the tropics, with 120 million people infected and over 750 million exposed to this filarial parasite. We have studied lymphatic filariasis infections as part of a multi-parasite survey in a village community in the savannah of northern Nigeria. We analysed serum samples from 341 individuals aged 5-70 years, detecting a W. bancrofti circulating antigen using the commercially available ICT Filariasis card test. The prevalence of infections was 10% and clearly age-dependent, increasing from below 2% in children to over 20% in subjects older than 40 years. Measuring IgG4 antibodies against the recombinant W. bancrofti antigen SXP1 showed that 36% of all tested individuals had been at least exposed to the parasite. Antibody levels also increased very significantly with age. A further analysis measuring Onchocerca volvulus-specific IgG4 antibodies showed a very significant association between infections with O. volvulus and those with W. bancrofti. Our data show that infections with W. bancrofti in Nigeria are still a frequently occurring health problem, since they are more prevalent than previously reported, and that individuals with an O. volvulus infection are more often infected with W. bancrofti than expected statistically.

Aged↗

Patterns of Onchocerca volvulus recombinant antigen recognition in a bovine model of onchocerciasis.

The antibody responses of 8 cattle experimentally infected with Onchocerca ochengi to 18 recombinant O. volvulus antigens were measured by ELISA. In addition to establishing antigenic cross-reactivity between the species, the dynamics of antigen-specific responses were examined to assess how the recognition of the antigens compared to the known stage-specificity of expression. Six cattle responded to all of the antigens and 2 animals responded to all but 1. The dynamics of the recognition of 4 antigens (B20, MOv-2, MOv-14 and OvNHR2 02E1) were characterized by rapid seroconversion following infection. Antibody levels to 2 antigens (Ov7 and OvALT-1) increased gradually over the course of infection. Antibody levels to 4 antigens (OvTPX-2, OvL3Chitinase, Ov103 and Ov9m) reached maximum levels coincident with the onset of patency. The levels to 3 antigens (OvProalf C50, OvAldolase, Ov39) varied little over the course of infection. Responses to antigens with functional similarities (OvSOD1, OvSOD2 and OvSOD3 or OvGST1 and OvGST2) showed comparable temporal profiles. This study demonstrates the high degree of immunological cross-reactivity between the antigens of O. volvulus and O. ochengi. The immunogenicity of antigens varied over the course of infection in an antigen-specific manner, which not always reflected developmentally regulated expression of the corresponding gene, possibly owing to cross-reactive epitopes on distinct parasite products.

Animals↗