Worm burden and host responsiveness in Wuchereria bancrofti infection: use of antigen detection to refine earlier assessments from the South Pacific.

Abstract

Abstract. A population from the Wuchereria bancrofti-endemic island of Mauke was reevaluated retrospectively by use of the Og4C3 circulating antigen (CAg) enzyme-linked immunosorbent assay to assess active infection in relation to host responses by age and gender. Use of microfilaremia (Mf) alone misclassified ϳ 50% of infected people, although CAg and Mf levels were positively correlated. Levels of CAg peaked between those aged 31-60 years; men aged Ͼ 60 years had a significantly higher CAg prevalence (Ͼ 90%) than women. Filaria-specific immunoglobulin (Ig) G4 reached maximum levels in both genders at age 51-60 years. By analysis of variance, both age and gender significantly influenced CAg and IgG4, with men having higher levels of both in the total population. Individuals positive for CAg had significantly lower lymphocyte proliferation responses to parasite antigen than did CAg-negative people, regardless of clinical status. This study reemphasizes the importance of CAg measurements for accurately assessing filarial prevalence and clinical status and demonstrates the relationship between active infection and immune responsiveness.

Rapid Wuchereria bancrofti-Specific Antigen Wb123-Based IgG4 Immunoassays as Tools for Surveillance following Mass Drug Administration Programs on Lymphatic Filariasis

“…To determine how the Wb123 IgG4 rapid ELISA compares with platforms used in other studies (12)(13)(14)17), subsets of samples previously tested by these methods in this laboratory were compared with the current ELISA results. The primary comparison was to the recently described Wb123-GST LIPS assay (13).…”

Heritable Factors Play a Major Role in Determining Host Responses toWuchereria bancroftiInfection in an Isolated South Pacific Island Population

“…CAg levels, which correlate directly with adult worm burdens [38] and Mf levels [31], are influenced by host genetics, and this demonstrates that the burden of infection in individuals is not simply a result of transmission intensity.…”

“…Second, circulating Mf levels were quantified by filtration of 1 mL of whole blood through a Nucleopore 3-mm polycarbonate filter (Whatman). Third, a quantitative measure of active infection (ie, related to the adult worm burden) was assessed by the level of circulating filarial antigen (CAg) in serum for all samples collected in 1992 and for 361 (81%) of 448 samples collected in 1974 [31]; for this CAg, the Og4C3 enzyme-linked immunosorbent assay (ELISA) (TropBio) was used in accordance with the manufacturer's instructions. Filarial antigen positivity status was also recorded as a binary variable (noted as positive or negative) for each individual, with positive values defined as 132 U/mL in the Og4C3 ELISA, as recommended by the manufacturer.…”

Sex ratio ofWuchereria bancroftiin surgical specimens from an endemic area of Brazil

“…Age and gender of the host may influence the clinical manifestations of bancroftian filariasis, women seeming to be more resistant to filarial infection and clinical disease than men, especially during their reproductive years (Steel et al, 2001). In some hypo-endemic areas, the prevalence of circulating filarial antigenaemia peaks between 21-60 years; above 60 years of age, men have a significantly higher prevalence of such antigenaemia than women (Steel et al, 2001). It is possible that the parasite sex ratio reported here would have differed if the present series had included specimens from women and older individuals.…”