Immunodiagnosis of bancroftian filariasis—Problems and progress

The immunodiagnosis of bancroftian filariasis is a major challenge to the immunoparasitologist. Significant progress is yet to be made in developing convenient laboratory animal model and inin vitro cultivation of filarial parasites making it very difficult to obtain required amount of parasite material for research. Parasitological examination techniques are not useful in low microfilaraemia, occult or chronic.filarial infections. A precise and accurate immunodiagnostic technique is very much needed for successful filaria control programmes. Such a test will also avoid the need for laborious night blood examination in bancroftian filariasis. Due to comparatively easy availability, a good amount of work has been done to explore immunodiagnostic potential of heterologous filarial antigens isolated fromLitomosoide carinii, Dirofilaria immitis, Brugia malayi, Setaria digitata, Setaria cervi and number of other filarial species. However, there has been limited or no significant success due to number of false negative and false positive reactions. Extensive study has also been made with antigens isolated fromWuchereria bancrofti microfilariae. Soluble antigens of microfilariae have been used in different immunological techniques such as skin test, counter immuno electrophoresis, indirect haemagglutination test, indirect fluorescent antibody test and enzyme linked immunosorbent assay. Fractionation of Wuchereria bancrofti microfilarial soluble antigens yielded mfS3e antigen fraction which was found to be highly reactive in microfilaraemia by enzyme linked immunosorbent assay, but the yield of the purified antigen was not sufficient enough to make it a practical proposition for large scale isolation of antigen. Wuchereria bancrofti microfilarial excretory-secretory antigens were found to be specific and highly sensitive requiring as little as 0.35 ng antigen protein per well in penicillinase enzyme linked immunosorbent assay for detection of filarial antibody. One ml of culture fluid was found to be sufficient for 400,000 tests. Field evaluation of this test showed that it can replace laborious night blood examination. Assay systems have been developed for detection of filarial antigen in serum, urine, hydrocele fluid and immune complexes using immunoglobulins from chronic filarial sera and antisera to excretory filarial antigens. Further purification of excretory-secretory antigens by affinity chromatography and production of monoclonal antibodies should hopefully give suitable reagents for use in sensitive assays such as enzyme immuno assay and immuno radiometric assay, providing an ideal assay system for detection of active filarial infection in the not too distant future.     

Isolation, purification and characterization of surface antigens of the bovine filarial parasite Setaria digitata for the immunodiagnosis of bancroftian filariasis

The surface antigens of the bovine filarial parasite Setaria digitata were isolated by EDTA extraction and purified by affinity chromatography using sepharose bound human filarial (Wuchereria bancrofti) antibodies obtained from chronic human filarial sera. The purified and crude antigens were used in enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies in bancroftian filariasis. The purified antigen showed sensitive and specific reactions in ELISA for the detection of antibodies in filarial sera and showed least cross reactivity with other parasitic infections. The crude and purified antigens showed about 18 and 6 peptide bands respectively in SDS-PAGE and about 11 and 6 antigenic bands respectively in enzyme-linked immunoelectrotransfer blot (EITB). The purified antigen was observed to be glycoprotein in nature. It was possible to identify the stage-specific infection in human filariasis by using the crude and purified antigens in EITB.     

Development of antigen detection ELISA for the diagnosis of brugian and bancroftian filariasis using antibodies to recombinant filarial antigens Bm-SXP-1 and Wb-SXP-1

Antibodies specific to recombinant filarial antigens Wb-SXP-1 and Bm-SXP-1 have been used to develop a sandwich ELISA for the detection of circulating filarial antigen (CFA) in sera from patients with lymphatic filariasis caused by Wuchereria bancrofti of Brugia malayi. In patients with W. bancrofti infections, a high proportion of microfilaria (mf) positive (MF) and low proportions of patients with chronic pathology (CP) and endemic normals (EN) showed the presence of CFA. Similarly in patients with brugian infections a high proportion of mf positive individuals contained CFA while none of the patients with chronic pathology or endemic normals showed the presence of CFA. Sera from patients with other parasitic infections (OPI) like O. volvulus, Loa loa, Ascaris lumbricoides and from individuals residing in areas non-endemic to filariasis did not exhibit any reactivity. This assay shows promise for the detection of microfilaremic infections in lymphatic filariasis and its usefulness as a diagnostic tool especially in B. malayi infections, needs to be further evaluated.     

Onchocerca volvulus and Wuchereria bancrofti: fluorescent antibody staining of frozen homologous sections for diagnosis

Antibody responses to two filarial diseases of man, onchocerciasis and bancroftian filariasis, were evaluated with the indirect fluorescent antibody technique (IFAT), using antigens derived from the appropriate etiologic agent. Antigenic preparations consisted of frozen cut sections of the adult Onchocerca volvulus and stage III larvae of Wuchereria bancrofti fixed to glass slides. Little difference between the preparations was demonstrated in tests for the diagnosis of onchocerciasis. Of 105 sera from individuals with biopsy-proven infections, 102 (97%) reacted with homologous O. volvulus antigen, and 19 of 22 (86%) with W. bancrofti antigen. In bancroftian filariasis, however, the homologously derived antigen was superior for diagnosis, and the highest seropositive rates occurred in acute, symptomatic infections. All such sera (8) reacted with homologous antigen. In contrast, only 75% (6) reacted with onchocercal antigen. Of those with chronic disease, characterized by long-standing elephantiasis or lymphedema without microfilaremia, 79% (22) were reactors to homologous antigen and 32% (9) to heterologous. The lowest seropositive rates occurred where microfilaremia was unaccompanied by local or systemic symptoms: 38% (3) were positive to homologous antigen and none to onchocercal antigen.Of sera from seven individuals apparently free of bancroftian filariasis, but living in a hyperendemic area, five reacted with bancroftian antigen and four with onchocercal antigen. These reactions could be attributed to occult infections, but more likely resulted from repeated exposure to nondeveloping infective larvae.Cross-reactions in nonfilarial infections were rare with either antigen, and no positive reactions occurred in sera from healthy controls.     

Homologs of the Brugia malayi diagnostic antigen BmR1 are present in other filarial parasites but induce different humoral immune responses

BACKGROUND: The recombinant antigen BmR1 has been extensively employed in both ELISA and immunochromatographic rapid dipstick (Brugia Rapid) formats for the specific and sensitive detection of IgG4 antibodies against the lymphatic filarial parasites Brugia malayi and Brugia timori. In sera of individuals infected with Wuchereria bancrofti the IgG4 reactivity to BmR1 is variable, and cross-reactivity of sera from individuals infected with Onchocerca volvulus or Loa loa was observed only in single cases. In order to characterize the homologs of the BmR1 antigen in W. bancrofti (Wb-BmR1), O. volvulus (Ov-BmR1) and L. loa (Ll-BmR1) the cDNA sequences were identified, the protein expressed and the antibody reactivity of patients' sera was studied. METHODS: PCR methodology was used to identify the cDNA sequences from cDNA libraries and/or genomic DNA of W. bancrofti, O. volvulus and L. loa. The clones obtained were sequenced and compared to the cDNA sequence of BmR1. Ov-BmR1 and Ll-BmR1 were expressed in E. coli and tested using an IgG4-ELISA with 262 serum samples from individuals with or without B. malayi, W. bancrofti, O. volvulus and L. loa infections or various other parasitic infections. BmR1, Ov-BmR1 and Ll-BmR1 were also tested for reactivity with the other three IgG subclasses in patients' sera. RESULTS: Wb-BmR1 was found to be identical to BmR1. Ov-BmR1 and Ll-BmR1 were found to be identical to each other and share 99.7% homology with BmR1. The pattern of IgG4 recognition of all serum samples to BmR1, Ov-BmR1 and Ll-BmR1 were identical. This included weak IgG4 reactivities demonstrated by L. loa- and O. volvulus-infected patients tested with Ov-BmR1 and Ll-BmR1 (or BmR1). With respect to reactivity to other IgG subclasses, sera from O. volvulus- and L. loa-infected patients showed positive reactions (when tested with BmR1, Ov-BmR1 or Ll-BmR1 antigens) only with IgG1. No reactivity was observed with IgG2 or with IgG3. Similarly, ELISAs to detect reactivity to other anti-filarial IgG subclasses antibodies showed that sera from individuals infected with B. malayi or W. bancrofti (active infections as well as patients with chronic disease) were positive with BmR1 only for IgG1 and were negative when tested with IgG2 and with IgG3 subclasses. CONCLUSIONS: This study demonstrates that homologs of the BmR1 antigen are present in W. bancrofti, O. volvulus and L. loa and that these antigens are highly conserved. Recognition of this antigen by patients' sera is similar with regard to IgG1, IgG2 and IgG3, but different for IgG4 antibodies. We conclude that the BmR1 antigen is suitable for detection of IgG4 antibodies in brugian filariasis. However, its homologs are not suitable for IgG4-based diagnosis of other filarial infections.     

A 43-kDa circulating filarial antigen fraction of Wuchereria bancrofti in immunoprophylaxis against Brugia malayi in jirds

A 43 kiloDaltan (kDa) antigen fraction (CFA₂-6) isolated from microfilaraemic plasma of bancroftian filarial patients showed selective reactivity with sera samples collected from endemic normals. Antibodies raised against this antigen showed a strong reactivity with the surface of Brugia malayi infective larvae as well as microfilariae. Similar antigenic determinants were detected in the parasite extracts, but not in the excretory–secretory products. Further analysis was done on the immunoprophylactic potential of CFA₂-6 in inducing immunity against Brugia malayi in Meriones unguiculatus (jird) in vivo. A strong protective response of approximately 84% was observed against the development of the filarial parasite in the jirds immunized with CFA₂-6. The immunized jirds also showed a significant clearance (87%) of microfilariae inoculated intravenously. Approximately 65% of infective larvae failed to survive in jirds transferred with anti-CFA₂-6 serum compared to the jirds transferred with sera from the control jirds. Passive transfer of anti-CFA₂-6 antibody to the jirds followed by intravenous inoculation of microfilariae resulted in the reduction of 77% of circulating microfilariae. This study suggests that the 43-kDa CFA₂-6 could stimulate a strong protective immune response against infective larvae and microfilariae in experimental animals.     

Wuchereria bancrofti: cloning and characterization of heat shock protein 70 from the human lymphatic filarial parasite

Heat shock protein 70 (HSP70) was identified as an immunodominant antigen by screening a Wuchereria bancrofti (Wb) microfilarial cDNA library with pooled Wb-infected sera, with 28% of the immunopositive clones coding for Wb-HSP70. The deduced amino acid sequence showed greater than 97 and 85% identity with HSP70 from filarial nematodes and humans, respectively. Recombinant HSP70 (74 kDa) and a recombinant protein from the C-terminal portion (43 kDa) also reacted with pooled Wb-infected sera, suggesting that the C-terminal region of HSP70 contains at least one antibody epitope. Brugia malayi L3 larvae showed increasing levels of HSP70 with increasing temperatures. Further, a polyclonal mouse anti-Wb-HSP70 antibody had reactivity to the HSP70 of cattle filarial parasite Settaria digitata and to human HSP70 derived from a Hep-2 cell line. Immune reactivity to Wb-HSP70 was strong, with uninfected non-endemic normal sera showing significantly greater reactions than sera from filaria-infected individuals. Both immunodominant self-HSP70 and HSP70 from other microbial infections may be primary targets for developing autoantibodies naturally.     

Detection of filarial antigen by inhibition enzyme linked immunosorbent assay using fractionatedBrugia malayi microfilarial excretory secretory antigen

Detection of filarial antigen in blood or urine samples would provide an accurate indication of active infection. The absence of a simple, well established animal model and limitations in getting the required amount of parasite material from human sources have been the main obstacles for the diagnosis ofWuchereria bancrofti infection. An inhibition ELISA has been developed for detection of filarial antigen using a partially purifiedBrugia malayi mf ES antigen (BmE DE1) and its affinity purified antibodies. Filarial antigen was detected in the sera of 88% of microfilaraemic, 60% of chronic filarial, 17% of endemic normal and none of the non- endemic normal subjects. The sensitivity and specificity of the assay were 88% and 89% respectively. Moreover, undiluted urine samples from 82% of microfilaraemic and 17% of endemic normal, but none of the non- endemic normal samples showed the presence of filarial antigen. With the limitations on the availability of sufficient homologous parasite materials, the inhibition ELISA using BmE DE1 and anti BmE DE1 antibodies shows promise for the detection of active infection in bancroftian filariasis in man. Moreover, its detection in urine makes it more possible to test patients in field areas.     

IgE responses in human filariasis. II. Qualitative characterization of filaria-specific IgE

Crossed radioimmunoelectrophoresis (CRIE) was used to characterize human IgE antibody responses to filarial parasites by using antigens derived from Brugia malayi (Bm) adult worms. A reference pool of patient sera was initially used to determine the sensitivity and specificity of CRIE. Because IgG-blocking antibodies interfered with IgE binding in certain sera, all sera were preabsorbed with protein A-Sepharose. As little as 50 ng of specific IgE antibody (determined by quantitative radioallergosorbent test [RAST]) in the reference pool bound to 20 of the 35 antigen precipitates in crossed immunoelectrophoresis. Increasing IgE antibody concentration did not increase the number of IgE-binding precipitates. Six patients from each of the three major clinical groups in lymphatic filariasis (i.e., tropical pulmonary eosinophilia [TE], chronic lymphatic pathology [CP], or circulating microfilaremia [MF]) were studied by CRIE with the use of a constant amount of IgE antibody (50 ng IgE anti-BmA). Distinct patterns of allergen recognition were observed among the groups. Individuals with TE recognized both anodic and cathodic antigens as allergens, whereas the other two groups recognized predominantly anodic antigens. The greatest number of allergens was recognized by patients with TE; this number ranged from nine to 18, whereas patients with CP or circulating MF recognized from six to 11 allergens. Although potentiated IgE responses at a quantitative level in parasitic helminth infections is a well-established phenomenon, our studies showing the diversity of antigens recognized as allergens indicate for the first time potentiated IgE responses at a qualitative level as well.     

Biological activity and diagnostic use of detergent soluble antigens fromSetaria digitata

Filarial parasite, responsible for filariasis is known to remain in the host for long periods of time. A 29 kDa protein isolated fromSetaria digitata by gel electrophoresis and electroelution of detergent soluble surface antigens showed a 70% inhibition of the cell mediated immune response. On evaluation of its diagnostic application, the same protein was found to be very sensitive in detecting antibody at an antigenic protein concentration as low as 1 ng per μl. The cross reactivity of surface antigen with bancroftian filarial patient’s sera was tested by Dot-ELISA and ELISA. Both the antigen as well as antibody detection tests showed 100% positivity with all types of filariasis cases. It did not produce any positive reaction with non-endemic control sera. However, a proportion of endemic normal subjects showed positivity and this is attributed to the fact that people in endemic areas are exposed to infective mosquito bites. The biological property of inhibition and 100% positivity of filariasis cases in both antibody and antigen detection tests point towards the bifunctional nature of the surface proteins before and after release. The same may be happening under normal conditions also, perhaps at a much lower rate     

Diagnostic utility of monoclonal antibodies raised against microfilarial excretory-secretory antigens in bancroftian filariasis

Two monoclonal antibodiesWuchereria bancrofti E 33 andWuchereria bancrofli E 34 raised againstWuchereria bancrofti microfilarial excretory-secretory antigens were studied for their diagnostic utility.Wuchereria bancrofti E 34 monoclonal antibody was found to be relatively specific and sensitive in detection of circulating filarial antigen. WhenWuchereria bancrofti E 34 monoclonal antibody was used alongwith immunoglobulin G fraction of human filarial serum immunoglobulins in double antibody sandwich enzyme linked immunosorbent assay. 68% of microfilaraemic sera (26 out of 38). 12% of clinical filarial sera (3 out of 25), 13% endemic normal sera (2 out of 15) and none of the 20 non-endemic normal sera showed the presence of filarial antigen. The filarial antigen detected byWuchereria bancrofti E 34 monoclonal antibody in double antibody sandwich enzyme linked immunosorbent assay is possibly associated with the active stage (microfilaraemia) of infection.     

Evaluation of a standardized F1 capsular antigen capture ELISA test kit for the rapid diagnosis of plague

Rapid detection of soluble F1 capsular antigen in serum, bubo fluid or urine of patients proved to be a valuable tool in the presumptive diagnosis of plague. We evaluated a F1 capsular antigen capture ELISA resembling a commercially available test kit. The minimal detectable concentration was 4 ng/ml. The specificity was 100% when investigating 47 sera from healthy Malagasy subjects and 98.4% when 365 sera from German blood donors were studied. Sensitivity was determined on sera (n=11) and buboes (n=18) from bacteriologically confirmed Malagasy plague patients. Sensitivity was 90.1% for serum and 100% for buboes. A standardized F1 capsular antigen capture ELISA test kit might be well suited for the early detection of plague particularly in non-endemic areas where clinical microbiological laboratories have only limited access to alternative techniques for rapid identification of Yersinia pestis.     

Demonstration of the humoral immune response of horses to Babesia caballi by western blotting.

Babesia caballi-infected or normal equine erythrocytes were solubilized in sodium dodecyl sulfate (SDS) buffer and analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. Antigens were allowed to react with sera from horses experimentally or field-infected with B. caballi and with sera from non-infected horses. Major babesial antigens recognized by immune sera had apparent mol. wts of 141, 112, 70, 50, 48, 34, and 30 kDa. The polypeptides at 50 and 48 kDa were recognized earliest and throughout infection, but also weakly by 3/100 equine sera tested negative and 1/33 sera tested false positive by the complement fixation test (CFT) and immunofluorescence antibody test (IFAT). Thus, further characterization and purification of B. caballi antigens are required to identify target antigens for an improved enzyme immuno assay. Until such an assay is available, Western blotting can provide a specific tool for the diagnosis of B. caballi infections, particularly in cases of contradicting CFT and IFAT results.     

Evaluation of ICT filariasis card test using whole capillary blood: comparison with Knott's concentration and counting chamber methods.

An immunochromatographic card test (ICT) that uses fingerprick whole blood instead of serum for diagnosis of bancroftian filariasis has recently been developed. The card test was validated in the field in Kenya by comparing its sensitivity to the combined sensitivity of Knott's concentration and counting chamber methods. A total of 102 (14.6%) and 117 (16.7%) persons was found to be microfilaremic by Knott's concentration and counting chamber methods, respectively. The geometric mean intensities (GMI) were 74.6 microfilariae (mf)/ml and 256.5 mf/ml by Knott's concentration and counting chamber methods, respectively. All infected individuals detected by both Knott's concentration and counting chamber methods were also antigen positive by the ICT filariasis card test (100% sensitivity). Further, of 97 parasitologically amicrofilaremic persons, 24 (24.7%) were antigen positive by the ICT. The overall prevalence of antigenemia was 37.3%. Of 100 nonendemic area control persons, none was found to be filarial antigen positive (100% specificity). The results show that the new version of the ICT filariasis card test is a simple, sensitive, specific, and rapid test that is convenient in field settings.     

IgG antibody subclasses in human filariasis. Differential subclass recognition of parasite antigens correlates with different clinical manifestations of infection

The four subclasses of IgG are distinct in structure, function, and degree of participation in the antibody response to complex antigens. Looking for differential responsiveness of potential pathogenetic significance, we have analyzed both quantitatively and qualitatively the filaria-specific IgG subclass responses of 20 patients with lymphatic filariasis presenting either with chronic lymphatic obstructive pathology and elephantiasis (CP) or with asymptomatic microfilaremia (MF). Subclass-specific monoclonal antibodies were used in an enzyme-linked immunosorbent assay to study IgG filarial antibodies quantitatively and in immunoblot analyses to determine qualitatively the subclass antibody specificities. Quantitatively, the most significant differences among patient groups were in levels of IgG4, which were more than 17 times higher in MF patients (geometric mean, 64.7 micrograms/ml) than in those with CP (mean, 3.7 micrograms/ml). When qualitative analyses were done on the same sera, major differences were noted, particularly in the recognition profiles of the IgG1, IgG3, and IgG4 responses. IgG1 and IgG3 responses to antigens were seen especially to antigens with m.w. greater than 68,000 in all patients with elephantiasis, whereas MF patients showed most of their reactivity to antigens less than 68,000. For IgG4, the MF patients showed prominent recognition of antigens throughout the entire range of m.w., whereas those with CP had very little IgG4 recognition of antigens of any m.w. Interestingly, this relationship was essentially reversed in the IgG3 antibody responses (especially to antigens greater than 68,000) and, to a lesser extent, the IgG1 responses. These findings demonstrate correlations of potential cause/effect significance between IgG4 antibody responsiveness and the immunomodulated asymptomatic MF form of clinical filariasis and between IgG3/IgG1 antibody responsiveness and the clinical presentation of CP.     

Differential reactivity of filarial antigens with human sera from bancroftian filariasis endemic zone

The reacting pattern of circulating filarial antigen fraction-2 fromWuchereria bancrofti and soluble antigen from adultBrugia malayi with bancroftian filarial sera were analysed by immunoblotting technique and enzyme linked immunosorbent assay. Microfilaraemic sera reacted specifically with proteins of molecular weight 200, 120, 97, 56, 54, 43, 26 and 17 kDa of circulating Filarial antigen fraction-2 and 44, 40, 38, 31, 22 and 18 kDa ofBrugia malayi adult soluble antigen. Clinical filarial sera identified protein molecules of 56, 54 and 42 kDa of circulating filarial antigen fraction-2 and 19, 16 and 14 kDa ofBrugia malayi adult soluble antigen. Some components of both the antigen preparation were also identified by endemic normal serai.e.proteins 120, 97, 62, 43 and 33 kDa of circulating filarial antigen fraction-2 and 170, 120, 43, 31 and 12 kDa ofBrugia malayi adult soluble antigen. One of the sodium dodecyl sulphate-polyacrylamide gel electropherosis fractions of circulating filarial antigen fraction-2 (CFA₂-8) andBrugia malayi adult soluble antigen fraction-6 when used in enzyme linked immunosorbent assay could differentiate microfilaraemic sera from endemic normal and clinical filarial sera. The other antigen fractions (CFA₂-2, 6 and 7 andBmA-2) showed a high geometric mean titre of filarial immunoglobulin G antibodies in endemic normal sera when compared to microfilaraemia and clinical filarial sera. These proteins need to be further studied to assess their involvement in protecting from filarial infection in an endemic area.     

Wuchereria bancrofti: Diminished platelet activation in filarial patients

Blood platelets are the innate immune elements that have not been investigated in human filarial infections. Platelet activation status in the endemic normals (EN), microfilaria positive individuals (MF) and patients with chronic pathology (CP) was evaluated in whole blood, under unstimulated as well as antigen exposed (BmA, E. coli) conditions for PAC-1 expression by Flow cytometry. A diminished PAC-1 expression was observed in MF compared to CP and EN spontaneously as well as upon antigen exposure. Besides this, PAC-1 expression within the groups did not exhibit any significant difference under all the experimental conditions. However in CP patients, E. coli antigen exposure resulted in a significantly reduced PAC-1 expression compared to the spontaneous expression levels. NO release in platelet culture supernatants from EN was inversely proportional to platelet aggregation. Collagen stimulated platelets from EN, exposed to sera and immune complexes from CP and MF patients resulted in elevated Nitric Oxide (NO) release, compared to those exposed to autologous sera and fetal calf serum. In addition, under similar conditions, collagen stimulated platelets from EN, exposed to filarial antigen (BmA) exhibited increased NO compared to the E. coli antigen exposed ones and light microscopic observations of cultured platelets supported the above findings. Thus it appears from the results of the present study that filarial antigen may play a role in the loss of platelet aggregation, leading to platelet inactivation.     

Two-dimensional immunoblot analysis of antigenic proteins of Spirometra plerocercoid recognized by human patient sera

Sparganosis is caused by invasion of Spirometra plerocercoid into various tissues/organs. Subcutaneous sparganosis can be diagnosed and treated by worm removal, while visceral/cerebral sparganosis is not easy to diagnose. The diagnosis depends largely on the detection of specific antibodies circulating in the patients' sera. Previous studies demonstrated that 31 and 36kDa proteins of the sparganum invoked specific and sensitive antibody responses, but also showed cross reactions with cysticercosis sera. We enriched protein fractions containing 31-36kDa through gel filtration and examined immune recognition pattern against the patient sera by 2-dimensional electrophoresis (2-DE) followed by immunoblotting. Serum samples from sparganosis patients recognized 8-10 protein spots of 31 and 36kDa with different isoelectric point (pI) values with variable combinations, in which four spots of 31kDa with pIs 3.4, 3.9, 4.0 and 4.1, and one 36kDa spot (pI 3.5) appeared to be specifically reactive. One 31kDa protein spot with pI 3.3 and two spots of 36kDa with pIs 3.3 and 3.5 reacted crossly with neurocysticercosis sera. Neither sera from patients with other parasitic infections nor those from healthy controls showed positive reaction. Two-DE/immunoblot analysis might be highly available in differential serodiagnosis of human sparganosis.     

An analysis of in vitro B cell immune responsiveness in human lymphatic filariasis

The immunoregulatory mechanisms involved in B cell function in patients with varying clinical manifestations of bancroftian filariasis were examined by studying the ability of peripheral blood mononuclear cells (PBMC) or PBMC subpopulations from patients with elephantiasis, asymptomatic microfilaremia (MF), and acute tropical pulmonary eosinophilia (TPE) to produce polyclonal and parasite-specific antibody in vitro, both spontaneously and in response to a mitogen (PWM) and to parasite antigen. When the spontaneous or mitogen-driven polyclonal responses were examined, all groups produced significant amounts of IgM and IgG; those with TPE produced extremely high levels. However, when in vitro parasite antigen-specific responses were examined, those with MF were unable to produce filaria-specific antibody either spontaneously or in response to PWM or parasite antigen; in contrast, patients with chronic lymphatic obstruction or TPE produced large quantities. Removal of neither adherent cells nor T8+ T cells affected the parasite-specific B cell anergy seen in those with MF. This absent or severely diminished capacity to produce antibody on parasite antigenic stimulation in patients with MF is likely responsible for the low levels of parasite-specific antibody seen in this most common clinical manifestation of bancroftian filariasis. Its inability to be reversed by the removal of "suppressor elements" suggests a state of B cell unresponsiveness to the parasite.