Filarial Antibody Research Articles

Detection of filarial antigen and antibody in serum and hydrocele fluid of 100 patients of hydrocele

The present study was carried out to detect an association between isolated non-communicable hydrocoele and filariasis and to provide awareness to positive patients regarding sequel and advising methods for the reduction of morbidity. Blood samples and hydrocoele fluids were used to detect filarial antigen and antibody by ICT Kit, Trop-bio kit and Sevafilachek Kit. These were followed by statistical evaluation by chi2 test. 14% of cases were positive for filarial antigen and antibody in hydrocoele patient serum, while 15% of cases were positive for filarial antigen and antibody in the serum of non-hydrocoele patients. Probability is less than 0.05, which is statistically significant.

A Woman from British Guyana with Recurrent Back Pain and Fever

Diagnosis: Chyluria associated with infection due to Wuchereria bancrofti. This patient, who had lived most of her life in an area in which Wuchereria bancrofti infection was endemic, received a diagnosis of chyluria due to lymphatic filariasis. The diagnosis was confirmed by serological testing for filarial antibody and the presence of circulating filarial antigen. Lymphatic filariasis caused by infection with W. bancrofti and Brugia species affects >120 million people worldwide. The spectrum of disease associated with filariasis includes asymptomatic microfilaremia, acute lymphangitis, and chronic manifestations, such as lymphedema, elephantiasis, chyluria, or hydrocele. Chyluria is produced by the rupture of lymphatics into the renal collecting system with resultant reflux of intestinal chyle into the urine (figure 1). This occurs when filaria residing in the lymphatics incite a chronic inflammatory reaction with scarring that ultimately increases pressure in the renal lymphatics. Filarial nematodes contain endobacteria of the genus Wolbachia, which are phylogenetic relatives of Rickettsia, Ehrlichia, and Anaplasma species [ 1-5]. Wolbachia species have coevolved in an ndosymbiotic fashion to some filarias, such as Wuchereria bancrofti, Brugia species, and Onchocerca volvulus (but not Loa loa). W lbachia endosymbionts of these filarial nematodes are vital for larval development and for fertility and viability in the adult female worm. In addition, there is evidence that Wolbachia species contribute to the inflammatory process within the lymphatics by releasing cell wall components that interact with Toll-like receptors and induce a lipopolysaccharide-like immune response [2-7]. The de endency of the filaria on Wolbachia species has led to the novel therapeutic approach of treating filariasis with antiWolbachia agents [2-4]. Doxycycline, which is active against Wolbachia species, sterilizes the adult female and interrupts transmission of Onchocerca species for up to several months. Doxycycline also enhances ivermectin-induced blockage of microfilaremia [2, 9]. On the other hand, treatment of lymphatic

Cloning and expression of a 12 kDa serospecific epitope of Wuchereria bancrofti

The immunoscreening of a microfilarial cDNA library of Wuchereria bancrofti with microfilaraemic sera revealed many positive clones expressing filarial antigens. One immunoreactive clone, designated PMR1, was shown to encode a protein of 114 amino acid residues. The cDNA fragment was subcloned into an expression vector, Pinpoint XaT. The resulting recombinant (r)PMR1-biotin fusion protein was expressed in Escherichia coli (BL21 [DE3] pLys) and was affinity purified on avidin resin. Analysis of sera of different groups for filarial antibodies against rPMR1 showed it to be highly reactive with microfilaraemic and clinical filarial sera compared to its reactivity with endemic and nonendemic controls. This indicates that the gene sequence of cDNA is expressing an immunodominant epitope, which could be useful in serodiagnosis of lymphatic filariasis.

Suppression of Brugia malayi (sub-periodic) larval development in Aedes aegypti (Liverpool strain) fed on blood of animals immunized with microfilariae

Preliminary studies were carried out to investigate the role of filarial specific antibodies, raised in an animal model against the filarial parasite, Brugia malayi (sub-periodic), in blocking their early development in an experimental mosquito host, Aedes aegypti (Liverpool strain). In order to generate filarial specific antibodies, Mongolian gerbils, Meriones unguiculatus, were immunized either with live microfilariae (mf) of B. malayi or their homogenate. Mf were harvested from the peritoneal cavity of Mongolian gerbils with patent infection of B. malayi and fed to A. aegypti along with the blood from immunized animals. Development of the parasite in infected mosquitoes was monitored until they reached infective stage larvae (L3). Fewer number of parasites developed to first stage (L1) and subsequently to L2 and L3 in mosquitoes fed with blood of immunized animals, when compared to those fed with blood of control animals. The results thus indicated that filarial parasite specific antibodies present in the blood of the immunized animals resulted in the reduction of number of larvae of B. malayi developing in the mosquito host.

PORT SITE METASTASES ARE FREQUENT AFTER OPEN LAPAROSCOPY IN PATIENTS WITH ADVANCED OVARIAN CARCINOMA, BUT DO NOT INFLUENCE THE SURVIVAL: AN ANALYSIS OF 173 CASES

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.

Microscopic haematuria as an occult filarial infection in bhubaneshwar an endemic area for bancroftian filariasis.

Sera samples of 7 microscopic haematuria cases collected before and after treatment with Diethylcarbamazine citrate, (DEC), 9 microfilaraemic cases and 19 endemic normal individuals were analysed for filarial antigen and IgG antibody levels. Filarial antigen was detected in 5 of the 7 microscopic haematuria cases, of which 3 turned negative for antigen after treatment with DEC. While none of the 7 haematuria cases were positive for filarial IgG antibodies, before the DEC treatment, all of them turned positive after DEC treatment. The sensitivity and specificity values(to detect mf +ve cases) were 89% and 90% respectively for the detection of filarial antigen and 78% and 95% respectively for the detection of filarial IgG antibodies.

Evaluation of sevafilachek immunoassays and rapid ICT-filariasis test for detection of bancroftian filariasis.

A comparative analysis was made on the utility of SEVAFILACHEK-stick based immunoassays and commercially available ICT-filariasis test to detect active infection in different groups of bancroftian filariasis. The SEVAFILACHEK immunoassays were found to be useful to detect filarial infection in microfilaraemia and in a significant number of clinical filarial cases with acute, chronic and occult clinical manifestations. In the clinical cases, microfilariae are not usually detected in peripheral circulation. Employing SEVAFILACHEK assays 6 and 5 of the 7 samples of patients with chronic filarial disease, and 6 and 5 of 6 microfilaraemic cases gave positivity for filarial IgG antibodies and antigen respectively. Four of the 6 occult filarial samples were positive for antibodies and antigen. Filarial antigen was detected by ICT-filariasis test in blood samples of all the 6 microfilariaemic cases, 1 chronic filarial and 2 occult filarial samples. The main advantage of ICT assay is its rapid format and convenience for field use.

Re-examination of the diagnostic criteria of tropical pulmonary eosinophilia

There is no agreement on the minimum absolute eosinophil count essential for the diagnosis of tropical pulmonary eosinophilia (TPE) at present. The aim of this study was to determine this figure as well as to evaluate the other diagnostic criteria of TPE. The response to diethylcarbamazine (DEC) was tested in 98 patients [of whom 79 (80·6%) completed the study] by means of clinical scores, lung function tests and the absolute eosinophil counts. The minimum absolute eosinophil count necessary for the diagnosis of TPE was found to be 3300 for two reasons. Firstly there was a marked fluctuation in the mean percentage change of the absolute eosinophil count after treatment with DEC, when it was below 3225 cells mm −3, while the mean percentage reduction showed a remarkable stability when the eosinophil count exceeded 3600. Secondly there was a marked difference in the response to DEC in patients whose eosinophil counts were above and below these values. All patients who had eosinophil counts greater than 3600 responded to DEC and were diagnosed as cases of TPE. All of them were from filarial endemic areas. The total eosinophil count decreased by a mean of 92·5%, 3 months after administration of DEC. The sensitivities of the following tests in TPE were as follows: filarial antibody test (FAT) 30%, radiological changes 45·5%, erythrocyte sedimentation rate (ESR) 80%. The radiological changes and the ESR, but not the FAT, were helpful in differentiating TPE from those patients with TPE-like symptoms but with lower eosinophil counts, e.g. those with asthma. Patients with cough who had eosinophil counts of between 53 and 2000 cells mm −3, showed elevated filarial antibody levels in a significant number of cases when compared to asymptomatic subjects. ( P<0·001). Five of them responded to DEC. Three of these had filarial antibody in their serum and one had bilateral mottling on chest X-ray. These results suggest that atypical cases of TPE may exist. Our study has shown that the diagnosis of TPE rests on the following criteria: cough worse at night; residence in a filarial endemic area; the eosinophil count greater than 3300 cells mm −3, clinical and haematological response to DEC. The diagnosis is supported by radiological changes and elevated ESR. The FAT is of little value. The clinical benefit and the improvement in lung function which follows the administration of DEC was sustained up to a minimum period of 15 months.

Effect of nutritional supplements and protease inhibitor on the yield of es antigens ofBrugia malayi microfilariaein vitro

Brugia malayi microfilarial excretory-secretory (mf ES) antigens obtained byin vitro maintenance of mf are important tools in the immunodiagnosis of bancroftian filariasis. To increase the yield of mf ES products, the effect of nutritional supplements on the culture medium (RPMI 1640) and the maintenance temperature were studied. Supplementation of RPMI 1640 medium with organic acids and sugars of Grace's insect culture medium forin vitro maintenance of 10 lakhs of mf in 40 ml medium increased the yield of mf ES antigen from 152 μg to 364 μg of mean protein, content and the mean antigen titre from 200 to 400. Supplementation with phenyl methyl sulphonyl fluoride (PMSF) and shift in the culture temperature resulted in a further increase in the yield of mf ES antigen to 502 μg of mean total protein with an antigen titre of 800. The modification resulted in a net increase of 3 fold in the protein content and 4 fold in the antigen titre of ES products. The above modifications in thein vitro maintenance of mf did not affect the diagnostic quality of mf ES antigen, which gave a sensitivity and specificity of 80% and 90% respectively in detection of filarial IgG antibodies inWuchereria bancrofti infected cases.

Immunomonitoring followed by optimal dec therapy for successful management of clinical filariasis in an endemic area

Lymphatic filariasis continues to be the major cause of clinical morbidity in India and other developing tropical countries. One of the major lacunae in the effective management of clinical filarial cases is the non-availability of a suitable diagnostic test for confirming filaria aetiology in acute, chronic and occult clinical cases where microfilariae (mf) are not usually seen in peripheral circulation. Studies in our laboratory have shown the usefulness of filarial antibody and antigen assays using microfilarial excretory-secretory (mf ES) antigen in detecting microfilaraemic, acute and chronic filarial cases and in confirming filarial aetiology in occult infections. Diethylcarbamazine citrate (DEC) is the drug of choice for lymphatic filariasis. Different regimens of DEC have been explored in the treatment of microfilaraemic cases. Immunomonitoring has shown that the seroconversion of antigen and antibody positivity was found to be very helpful in determining appropriate period of DEC treatment for clinical relief and cure in clinical filarial patients and further they did not have recurrence in most of the cases. Optimal DEC (6mg/kg body wt/day for 21 days each month for 3-12 months) therapy was found to be very effective in acute and atypical clinical manifestations such as asthmatic bronchitis, pulmonary eosinophilia, monoarthritis, recurrent upper respiratory tract infections (URI), pneumonia (super imposed infections) in children and minimal hydrocele, epididymoorchitis, lymphangitis, lymphadenitis, acute abdomen, central serous retinopathy, tenosynovitis, pain and swelling in limbs and joints in adults living in filaria endemic areas.

Filarial antibody responses in Wuchereria bancrofti transmission area are related to parasitological but not clinical status

In Wuchereria bancrofti transmission areas, three groups of individuals have been identified, according to the presence or absence of microfilariae or adult worm derived molecules in the blood compartment. These groups likely reflect individuals with different permissivity/resistance to the complete development of W. bancrofti cycle. The profile of filarial‐specific immunoglobulins was analysed in W. bancrofti‐exposed individuals in French Polynesia, according to the presence or absence of microfilariae (Mf) and adult worms, measured by Og4C3 circulating antigen. Individuals harbouring adult worms, have higher filarial‐specific IgG4 but lower IgG3 and IgE levels, than adult worm‐free individuals, independently of the presence of Mf. Low filarial‐specific IgG1 and IgG2 levels were associated with the presence of Mf but independent of the presence/absence of adult worms. The filarial antibody responses were associated with the parasitological status of individuals but not with clinical symptoms such as hydroceles or limb lymphangitis or elephantiasis. The reduction of filarial‐specific immunoglobulin levels was higher after treatment with diethylcarbamazine than ivermectin, which likely reflects the better effect of the former on W. bancrofti adult worms. However, reduction of antibody levels was also observed in Mf‐and adult worm‐negative individuals. This could be due to the overall reduction of W. bancrofti transmission in the island where this study took place.

Filarial antibody responses in Wuchereria bancrofti transmission area are related to parasitological but not clinical status.

In Wuchereria bancrofti transmission areas, three groups of individuals have been identified, according to the presence or absence of microfilariae or adult worm derived molecules in the blood compartment. These groups likely reflect individuals with different permissivity/resistance to the complete development of W. bancrofti cycle. The profile of filarial-specific immunoglobulins was analysed in W. bancrofti-exposed individuals in French Polynesia, according to the presence or absence of microfilariae (Mf) and adult worms, measured by Og4C3 circulating antigen. Individuals harbouring adult worms, have higher filarial-specific IgG4 but lower IgG3 and IgE levels, than adult worm-free individuals, independently of the presence of Mf. Low filarial-specific IgG1 and IgG2 levels were associated with the presence of Mf but independent of the presence/absence of adult worms. The filarial antibody responses were associated with the parasitological status of individuals but not with clinical symptoms such as hydroceles or limb lymphangitis or elephantiasis. The reduction of filarial-specific immunoglobulin levels was higher after treatment with diethylcarbamazine, than ivermectin, which likely reflects the better effect of the former on W. bancrofti adult worms. However, reduction of antibody levels was also observed in Mf-and adult worm-negative individuals. This could be due to the overall reduction of W. bancrofti transmission in the island where this study took place.

Antibodies to diethylcarbamazine potentiate the antifilarial activity of the drug.

The antifilarial drug diethylcarbamazine citrate (DEC) is known to mediate in vivo microfilaricidal activity in conjunction with the host immune system. In this study passive transfer of antibodies to DEC elicited by immunization with methyl piperazine carboxylic acid (MPCA) coupled to bovine serum albumin (BSA), was found to potentiate microfilaricidal activity of subcurative doses of DEC in Setaria digitata infected Mastomys coucha. Active immunization of microfilaraemic animals with MPCA-BSA followed by administration of subcurative doses of DEC also resulted in rapid clearance of microfilaraemia in both S. digitata and Brugia malayi infected M. coucha indicating the synergistic activity of DEC and the antibodies to the drug. Since some of the filarial antibodies are known to react with DEC, it is proposed that such antibodies may potentiate the microfilaricidal activity of the drug in vivo.

Immunoreactive molecules of Brugia malayi and their diagnostic potential

Antigen derived from three major life-stages of human lymphatic filariid, Brugia malayi was fractionated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and reactivity of filarial antibodies, present in sera of human bancroftian patients belonging to different categories of the disease, to immunoreactive molecules was evaluated by Western blotting and immune recognition. Antigen molecules of >180, ~180, ~116, ~66, 58, 33 and <20 kDa were strongly identified in blots especially by symptomatic and endemic normal sera. Although mf positive serum reacted with the majority of these molecules, the intensity of bands was poor. These functional molecules along with ~43 kDa were later isolated from a preparative SDS-polyacrylamide gel by elution. The diagnostic utility of these purified molecules was then assessed by enzyme linked immunosorbent assay (ELISA) for detecting the IgG antibodies in patients' sera of various categories. Tropical pulmonary eosinophilic subjects revealed highest reactivity with <20 and ~116 kDa molecules while mf positive ones reacted feebly with the majority of the molecules except ~43 and ~66 kDa. Sera of endemic normals revealed high IgG levels but antibodies to ~ 66 kDa were highest. Symptomatic patients showed moderate reactivity. Non-endemic sera neither reacted in blots nor in ELISA. The study demonstrates the usefulness of ~43 kDa in detecting IgG antibodies of mf positive asymptomatic patients. High IgG levels to ~66 kDa followed by ~116 kDa and <20 kDa in sera of endemic normals warrants their immunoprophylactic evaluation.

Clinical and laboratory features of patients with loiasis ( Loa loa filariasis) in the U.K.

To assess differences between Africans and expatriates, we reviewed records of 100 patients with loiasis presenting to The Hospital for Tropical Diseases, London. Fifty-one were black Africans, and 49 were white expatriates. A history of Calabar swellings was more common amongst expatriates (P = 0.0001, OR 8.1), whilst eyeworm was reported more frequently in Africans (P = 0.0038, OR 4.2). Higher eosinophil levels (P < 0.0001) and filarial antibody levels, whether measured by immunofluorescence (P = 0.047) or ELISA (P < 0.0001) were present in the expatriates. Africans were more likely to have microfilaraemia (P < 0.0025, OR 7.3), and among microfilaraemic patients, Africans had denser microfilaraemia (P = 0.012). The sensitivity of microfilaremia as a screening test for loiasis was 75% in Africans and 29% in expatriates. The sensitivities of filarial antibody tests in Africans and expatriates were 81% and 100% for IFAT, and 28% and 93% for ELISA. Following treatment, 63% of patients were considered cured, 25% were lost to follow-up and 12% had a documented relapse. The differences between the two groups of patients could be caused by differences in the chronicity of loiasis, but other explanations are also discussed.

Diagnostic potential of fractionated Brugia malayi microfilarial excretory/secretory antigen for bancroftian filariasis

Due to the non-availability of sufficient parasite material from Wuchereria bancrofti, a heterologous filarial antigen from Brugia malayi has been investigated for the diagnosis of bancroftian filariasis. B. malayi microfilarial excretory/secretory antigen (BmmfES) effectively inhibited the binding of circulating filarial antigen fractions (CFA2-1,9,11 and 12) from microfilaraemic cases, and of W. bancrofti microfilarial excretory/ secretory antigen, to the immunoglobulin G (IgG) fraction of anti-filarial serum immunoglobulins. BmmfES was separated by ion-exchange chromatography on DEAE cellulose into 2 fractions, BmE DE1 and BmE DE2. BmE DE1 was marginally superior to whole BmmfES and BmE DE2 in detecting filarial IgG antibodies in human sera. 230 human sera from different groups of patients were screened against BmE DE1, which detected specific IgG in 83% of sera from microfilaraemic donors, 83% of sera from patients with clinical filariasis, 17% of sera from normal residents of an endemic area, and in none of the sera from persons living in a non-endemic area. The assay system using BmE DE1, with a sensitivity of 83% and specificity of 83%, should be very useful in detecting microfilaraemia, particularly in active clinical infections where the parasite is usually not seen.

Filarial Antibody Detection in Suspected Occult Filariasis in Children in an Endemic Area

A study was conducted in filarial endemic area for diagnosis of occult filariasis in various clinical conditions in children. Thirty-five age- and sex-matched controls (endemic-15, non-endemic-10, disease control-10), 16 classical lymphatic filariasis, and 92 occult filariasis (clinical conditions which fall in the spectrum of occult filariasis and suspected to be filarial), were subjected to peripheral night blood smear examination for microfilaria (mf) and stick ELISA test using mf ES antigen for filarial antibodies. In the control group none showed mf and only 3 per cent (1/35) among endemic control were positive for filarial antibodies. In classical filariasis 1 per cent (2/16) showed mf and 94 per cent (15/16) had filarial antibodies. In suspected occult filariasis 1 per cent (one case of arthritis) showed mf and 62 per cent (57/92) showed filarial antibodies. These consisted of tropical pulmonary eosinophilia 63 per cent (15/24), arthritis where no cause could be ascertained on investigation 64 per cent (27/42), nephrotic syndrome 69 per cent (11/16), acute glomerulonephritis with ASO < 200 units 38 per cent (3/8), and cardiomyopathy 50 per cent (1/2). Correlation with age showed that 80 per cent (4/5) of cases of arthritis seen in 0-4 years of age group and 82 per cent (11/9) of nephrotic syndrome in the 10-14 years of age group were positive for filarial antibody. Arthritis due to other causes and minimal change nephrotic syndrome are uncommon in these respective age groups. It is concluded that the role of filariasis in endemic areas in these disease states cannot be denied and needs to be studied further.

Filarial antibody and antigen detection in different clinical conditions in an endemic area

The study was conducted in filarial endemic area for various clinical presentations and diagnosis of occult filariasis. A total of 157 cases of various clinical presentations namely tropical pulmonary eosinophilia, monoarthritis, polyarthritis, glomerulonephropathy, tenosynovitis, inguinal lymphadenopathy, generalised lymphadenopathy, retroperitonial lymphadenopathy, endomyocardial fibrosis and acute conjunctivitis were screened for filarial antigen and antibody by enzyme linked immunosorbent assay (ELISA). Out of 157 cases, 107 cases were positive for antigen or antibody, suggesting the role of filarial infection in these clinical presentations. All the 107 cases were treated with diethylcarbamazine citrate (DEC) and some of the patients who were followed showed relief in signs and symptoms. Hence assay of filarial antigen and/or antibody may be useful for diagnosing occult filarial syndromes for better management and further appropriate treatment.

A Case of Acquired Lymphangioma Due to a Suspected Old Filariasis and a Review of Literature

A 65-year-old man presented in 1992 with multiple papular lesions on the scrotum and foreskin. His medical history revealed that, at the age of 25, he was diagnosed as having filariasis and treated conservatively at a hospital in Hawaii. The histologic study of the scrotal skin showed large, dilated vascular spaces in the upper dermis lined with a single layer of endothelial cells that were negative for Factor 8-related antigen. The diagnosis was acquired lymphangioma due to a suspected old filariasis infestation, although serologic tests for filarial antibodies were negative. The paper also presents a review of the literature of acquired lymphangioma in Japan with a brief discussion of etiology and nomenclature.

Bancroftian filariasis in Kwale District of Kenya. II. Humoral immune responses to filarial antigens in selected individuals from an endemic community.

Humoral immune responses to filarial infection were investigated in 162 individuals, covering the full clinical and parasitological spectrum of bancroftian filariasis as seen in an endemic community of Kwale District, Kenya. Sera were tested for specific antifilarial antibodies (total immunoglobulins, IgM, IgGl, IgG4 and IgE) using ELISA. Most individuals showed an immunological response to the filarial antigen (prepared from adult Brugia pahangi). How these responses were related to the clinical manifestations, parasitological status and age was analysed by comparing the mean antibody levels among different categories of endemic individuals, and by comparing these to the levels in control groups from filariasis-free areas. IgM and IgE anti-filarial antibodies were detected with low specificity in unabsorbed sera. A higher specificity, clearly distinguishing the mean antibody levels in the endemic categories from those of control groups, was obtained for total specific immunoglobulins, and for IgE in sera absorbed with protein A. The most specific results were obtained for IgGl and IgG4; clear inter-category differences were observed for these classes. The mean level of specific IgG4 was significantly higher in microfilaraemic groups than in amicrofilaraemic groups, whereas the mean level of specific IgGl was significantly higher in amicrofilaraemic, symptomatic cases than in microfilaraemic, symptomatic cases. In most categories of endemic individuals, and for most antibody isotypes, the mean levels of specific antibodies tended to be higher (although not significantly) in the younger individuals than in the older individuals. Overall, the differences in the filarial antibody responses were more closely related to the presence or absence of microfilariae and to the age of the individuals than to the disease manifestations in this endemic population.