Human antibody responses to Wuchereria bancrofti infective larvae

Abstract

Human IgG antibody responses to Wuchereria bancrofti third stage infective larvae (L3) surface and somatic antigens were studied by indirect immunofluorescence (IFA) and immunoblot with endemic Egyptian sera (n = 115) with the aim of identifying targets of protective immunity. Human sera variably recognized 14 major bands in L3 by immunoblot. The statistical significance of group differences in antibody prevalence was assessed by the chi-squared test. Children and young adults (aged 10-20 years) tended to have antibodies to more L3 somatic antigens than older adults, with significant differences for bands at 66, 60 and 5 kDa. Infected subjects had more consistent antibody responses to antigens at 55, 50 and 6 kDa than endemic normal subjects with negative serum filarial antigen tests, who are presumed to be uninfected. A 5 kDa antigen was preferentially recognized by the latter group. Antibodies to L3 surface antigens were equally prevalent in uninfected children (75%) and adults (90%) but less prevalent in people with microfilaremia (38%) than in amicrofilaremic subjects with or without filarial antigenemia (81%) (P < 0.001). IFA-positive sera showed significantly enhanced recognition of antigens at 66, 40 and 14 kDa in immunoblots relative to IFA-negative sera. Additional studies are needed to further characterize antigens identified in this study and to establish whether they are indeed targets of protective immunity in humans.

Differential Cytokine and Antibody Responses to Adult and Larval Stages ofOnchocerca volvulusConsistent with the Development of Concomitant Immunity

“…The total level of binding was determined initially for 20 individuals and later against L3 only for an additional 14 individuals. Scoring the intensity of the fluorescence was done in a semiquantitative manner as described by Kurniawan-Atmadja et al (27) and Helmy et al (22). Briefly, 25 to 50 live L3 parasites or 100 mf were incubated with sera at a 1:20 dilution for 1 h in PBS, followed by washing and incubation with a 1:15 dilution of fluorescein isothiocyanate-conjugated rabbit anti-human immunoglobulins (Dako; F200).…”

Novel Phage Display-Based Subtractive Screening To Identify Vaccine Candidates ofBrugia malayi

“…In the areas of endemicity, some individuals are naturally immune to the disease (endemic normal; EN), whereas some carry the infection (microfilaremics; MF) and others exhibit chronic pathology (CP). Although the nature of protective immune responses is highly debated (38,34), the general consensus is that the host immune responses play a major role in determining clinical manifestations of various groups (20,13). In this respect, subjects in the "EN" group, which are constantly exposed to the infection without showing any symptoms of parasitemia (20,13), are probably the most interesting group to study since they may carry circulating protective antibodies.…”

“…Using these approaches several potential vaccine candidates have been identified and reported to have varying degrees of protection in animal models (1,20,24,28,29,33,37,50). Although there are effective drugs available for the control of filariasis, developing a vaccine remains a promising strategy for mass control of this mosquito-borne infection in areas of endemicity (24,29,28,50).…”

Cloning and characterization of a novel immunogenic protein 3 (NIP3) from Brugia malayi by immuno screening of a phage-display cDNA expression library

“…In the endemic areas, some individuals are naturally immune to the disease (Endemic Normal, EN); whereas, some carry the infection and show acute symptoms (Microfilaremics, MF) and others exhibit morphological evidence of lymph edema in the dependable parts as the infection becomes chronic (Chronic Pathology, CP). Although the nature of protective immune responses is highly debated over several years, (Peralta et al 1999;Ravindran et al 2000) the consensus is that the host immune responses play a major role in determining clinical manifestations of various groups (Helmy et al 2000;Frank et al 1996). In this respect the "EN" group, which resides in the endemic area and are constantly exposed to the infection without showing any symptoms of parasitemia (Helmy et al 2000;Frank et al 1996) are probably the most attractive group since they carry circulating antibodies that may be host-protective.…”

“…Although the nature of protective immune responses is highly debated over several years, (Peralta et al 1999;Ravindran et al 2000) the consensus is that the host immune responses play a major role in determining clinical manifestations of various groups (Helmy et al 2000;Frank et al 1996). In this respect the "EN" group, which resides in the endemic area and are constantly exposed to the infection without showing any symptoms of parasitemia (Helmy et al 2000;Frank et al 1996) are probably the most attractive group since they carry circulating antibodies that may be host-protective. Therefore, there has been considerable interest in identifying the parasite antigens that generated the host protective antibodies in EN individuals.…”