Antifilarial Therapy Research Articles

In vitro extracellular replication of Wolbachia endobacteria.

Obligate intracellular endobacteria of the genus Wolbachia are widespread in arthropods and several filarial nematodes. Control programs for vector-borne diseases (dengue, Zika, malaria) and anti-filarial therapy with antibiotics are based on this important endosymbiont. Investigating Wolbachia, however, is impeded by the need for host cells. In this study, the requirements for Wolbachia wAlbB growth in a host cell-free in vitro culture system were characterized via qPCRs. A cell lysate fraction from Aedes albopictus C6/36 insect cells containing cell membranes and medium with fetal bovine serum were identified as requisite for cell-free replication of Wolbachia. Supplementation with the membrane fraction of insect cell lysate increased extracellular Wolbachia replication by 4.2-fold. Replication rates in the insect cell-free culture were lower compared to Wolbachia grown inside insect cells. However, the endobacteria were able to replicate for up to 12 days and to infect uninfected C6/36 cells. Cell-free Wolbachia treated with the lipid II biosynthesis inhibitor fosfomycin had an enlarged phenotype, seen previously for intracellular Wolbachia in C6/36 cells, indicating that the bacteria were unable to divide. In conclusion, we have developed a cell-free culture system in which Wolbachia replicate for up to 12 days, providing an in vitro tool to elucidate the biology of these endobacteria, e.g., cell division by using compounds that may not enter the C6/36 cells. A better understanding of Wolbachia biology, and in particular host-symbiont interactions, is key to the use of Wolbachia in vector control programs and to future drug development against filarial diseases.

Imported Mansonella perstans infection in Spain

BackgroundMansonella perstans infection can be considered one of the most neglected tropical infectious diseases. Very few studies have reported on the clinical picture caused by infection with this nematode. Therefore, our study was aimed to describe the clinical patterns and treatment of imported M. perstans infection by migrants from Africa.MethodsThe present study evaluated a large cohort of migrants who have been diagnosed, examined and treated for imported M. perstans infection at a Spanish reference center (Hospital Carlos III Tropical Medicine Unit, Madrid, Spain) over a 19-year period. Most patients voluntarily attend the emergency unit or are referred from primary care or general hospitals in Madrid. Chi-square test was used to compare the association between categorical variables. The continuous variables were compared by Student’s t-test or the Mann–Whitney test. The corresponding regression models were used for multivariate analysis.ResultsFive hundred three cases of migrants from tropical and subtropical areas with M. perstans infection were identified. Two hundred sixty-four patients were female (52.5%). The mean age (± SD) was 44.6 ± 18.2 years (range: 16–93 years). The mean time (± SD) between the arrival in Spain and the first consultation was 8.6 ± 18.0 months. The major origin of the patients was Equatorial Guinea (97.6%). Regarding the clinical picture, 257 patients were asymptomatic (54.7%) and 228 were symptomatic (45.3%); 190 patients had pruritus (37.8%), 50 (9.9%) had arthralgia, 18 patients had Calabar-like swelling (3.6%), and 15 (3%) had abdominal pain. Four hundred forty-two (87.9%) migrants had hyper-IgE, and 340 (67.6%) had eosinophilia. One hundred ninety-five patients had coinfections with other filarial nematodes (38.8%), and 308 migrants had only M. perstans infection (61.2%). Four hundred thirty-seven cases (86.9%) had been treated with anti-filarial drugs; 292 cases were treated with one anti-filarial drug, and 145 cases were treated with combined anti-filarial therapy. Additionally, 20 (4%) cases received steroids and 38 (7.6%) cases received antihistamines.ConclusionsA long series of M. perstans infections is presented in sub-Saharan immigrants whose data indicate that it should be included in the differential diagnosis in patients with pruritus or analytical alterations such as eosinophilia or hyper-IgE presentation, and they also have a high number of coinfections with other microorganisms whose treatment needs to be protocolized.

Virtual screening of natural anti-filarial compounds against glutathione-S-transferase of Brugia malayi and Wuchereria bancrofti

Glutathione-S-transferase also referred as GST is one of the major detoxification enzymes in parasitic helminths. The crucial role played by GST in various chronic infections has been well reported. The dependence of nematodes on detoxification enzymes to maintain their survival within the host established the crucial role of GST in filariasis and other related diseases. Hence, this well-established role of GST in filariasis along with its greater nonhomology with its human counterpart makes it an important therapeutic drug target. Here in this study, we have tried to explore the inhibitory potential of some of the well-reported natural ant-filarial compounds against the GST from Wuchereria bancrofti (W.bancrofti) and Brugia malayi (B.malayi). In silico virtual screening, approach was used to screen the selected natural compounds against GST from W.bancrofti and B.malayi. On the basis of our results, here we are reporting some of the natural compounds which were found to be very effective against GSTs. Along with we have also revealed the characteristic of the active site of BmGST and WbGST and the role of important active site residues involve in the binding of natural compounds within the active site of GSTs. This information will oped doors for using natural compounds as anti-filarial therapy and will also be helpful for future drug discovery.

Glucose and Glycogen Metabolism in Brugia malayi Is Associated with Wolbachia Symbiont Fitness.

Wolbachia are endosymbiotic bacteria found in the majority of arthropods and filarial nematodes of medical and veterinary importance. They have evolved a wide range of symbiotic associations. In filarial nematodes that cause human lymphatic filariasis (Wuchereria bancrofti, Brugia malayi) or onchocerciasis (Onchocerca volvulus), Wolbachia are important for parasite development, reproduction and survival. The symbiotic bacteria rely in part on nutrients and energy sources provided by the host. Genomic analyses suggest that the strain of Wolbachia found in B. malayi (wBm) lacks the genes for two glycolytic enzymes—6-phosphofructokinase and pyruvate kinase—and is thus potentially unable to convert glucose into pyruvate, an important substrate for energy generation. The Wolbachia surface protein, wBm00432, is complexed to six B. malayi glycolytic enzymes, including aldolase. In this study we characterized two B. malayi aldolase isozymes and found that their expression is dependent on Wolbachia fitness and number. We confirmed by immuno-transmission electron microscopy that aldolase is associated with the Wolbachia surface. RNAi experiments suggested that aldolase-2 plays a significant role in both Wolbachia survival and embryogenesis in B. malayi. Treatment with doxycycline reduced Wolbachia fitness and increased the amount of both glucose and glycogen detected in the filarial parasite, indicating that glucose metabolism and glycogen storage in B. malayi are associated with Wolbachia fitness. This metabolic co-dependency between Wolbachia and its filarial nematode indicates that glycolysis could be a shared metabolic pathway between the bacteria and B. malayi, and thus a potential new target for anti-filarial therapy.

Parasite-antigen driven expansion of IL-5(-) and IL-5(+) Th2 human subpopulations in lymphatic filariasis and their differential dependence on IL-10 and TGFβ.

BackgroundTwo different Th2 subsets have been defined recently on the basis of IL-5 expression – an IL-5+Th2 subset and an IL-5−Th2 subset in the setting of allergy. However, the role of these newly described CD4+ T cells subpopulations has not been explored in other contexts.MethodsTo study the role of the Th2 subpopulation in a chronic, tissue invasive parasitic infection (lymphatic filariasis), we examined the frequency of IL-5+IL-4+IL-13+ CD4+ T cells and IL-5−IL-4 IL-13+ CD4+ T cells in asymptomatic, infected individuals (INF) and compared them to frequencies (Fo) in filarial-uninfected (UN) individuals and to those with filarial lymphedema (CP).ResultsINF individuals exhibited a significant increase in the spontaneously expressed and antigen-induced Fo of both Th2 subpopulations compared to the UN and CP. Interestingly, there was a positive correlation between the Fo of IL-5+Th2 cells and the absolute eosinophil and neutrophil counts; in addition there was a positive correlation between the frequency of the CD4+IL-5−Th2 subpopulation and the levels of parasite antigen – specific IgE and IgG4 in INF individuals. Moreover, blockade of IL-10 and/or TGFβ demonstrated that each of these 2 regulatory cytokines exert opposite effects on the different Th2 subsets. Finally, in those INF individuals cured of infection by anti-filarial therapy, there was a significantly decreased Fo of both Th2 subsets.ConclusionsOur findings suggest that both IL-5+ and IL-5−Th2 cells play an important role in the regulation of immune responses in filarial infection and that these two Th2 subpopulations may be regulated by different cytokine-receptor mediated processes.

Low Density Microfilaraemia as a Causative Agent in a Case of Unexplained Ascitis of Suspicious Nature

It is estimated that 120 million people worldwide are affected by filariasis. In the South East and South Asian region, Wuchereria bancrofti is the most prevalent parasite causing filariais in 99.4 % of cases. In the present case the parasite was a cause of unexplained ascitis in a young female whose previous cytological report was suspicious in nature. Extensive physical and radiological assesment was not able to determine the cause of ascitis. Repeat cytological examinantion revealed a few microfilariae of Wuchereria bancrofti. The patient was diagnosed as a case of low density microfilaremia and was put on anti-filarial therapy subsequent to which ascitis of the patient regressed. In this case, the clinical picture did not give a clue regarding the aetiology of the ascites. There was no evidence suggestive of filariasis, such as lymphoedema or hydrocele except mild eosinophilia. Circumstantialtial evidence regarding the aetiology of the effusion in our patient included her recovery following antifilarial therapy. The cytological diagnosis of Mf in this patient avoided further expensive investigations and the patient responded to antifilarial therapy.

Wolbachia and Its Implications for the Immunopathology of Filariasis

Filarial infections are characterized by immunopathological phenomena, that are responsible for the onset of often dramatic pathological outcomes, such as blindness (Onchocerca volvulus) and elephantiasis (W. bancrofti). In addition, the long-term survival (as long as 10 years) of these parasites in otherwise immunocompetent hosts indicates that these nematodes are capable of manipulating the host immune response. The ground-breaking discovery of the bacterial endosymbiont Wolbachia, which resides in most filarial nematodes causing disease, has led to increasing interest in the role it may play in immuno-modulation, pro-inflammatory pathology and other aspects of filarial infection. Indeed, Wolbachia has been shown to be responsible for exacerbating inflammation (as in river blindness), while at the same time blocking efficient elimination of parasites through the host immune response (Onchocerca ochengi). While studies aimed at identifying Wolbachia as a potential target for anti-filarial therapy are at the forefront of current research, understanding its role in the immunology of filarial infection is a fascinating field that has yet to uncover many secrets.

Targeting the Wolbachia Cell Division Protein FtsZ as a New Approach for Antifilarial Therapy

The use of antibiotics targeting the obligate bacterial endosymbiont Wolbachia of filarial parasites has been validated as an approach for controlling filarial infection in animals and humans. Availability of genomic sequences for the Wolbachia (wBm) present in the human filarial parasite Brugia malayi has enabled genome-wide searching for new potential drug targets. In the present study, we investigated the cell division machinery of wBm and determined that it possesses the essential cell division gene ftsZ which was expressed in all developmental stages of B. malayi examined. FtsZ is a GTPase thereby making the protein an attractive Wolbachia drug target. We described the molecular characterization and catalytic properties of Wolbachia FtsZ. We also demonstrated that the GTPase activity was inhibited by the natural product, berberine, and small molecule inhibitors identified from a high-throughput screen. Furthermore, berberine was also effective in reducing motility and reproduction in B. malayi parasites in vitro. Our results should facilitate the discovery of selective inhibitors of FtsZ as a novel anti-symbiotic approach for controlling filarial infection.NoteThe nucleotide sequences reported in this paper are available in GenBank™ Data Bank under the accession number wAlB-FtsZ (JN616286).

A rare case of reversible acquired AA-type renal amyloidosis in a chronic filariasis patient receiving antifilarial therapy

Lymphatic filariasis is a major health problem in India with a large number of patients tending to be asymptomatic. In the Southeast and South Asian regions, Wuchereria bancrofti is the most prevalent parasite, causing filariasis in 99.4% of cases. While kidney involvement is a rare event in chronic filariasis, this case is unique because AA-type renal amyloidosis occurs in chronic W. bancrofti infection. We present here a unique case of lymphatic filariasis. The patient, a 25-year-old male who was previously diagnosed with right lower limb filarial lymphedema and had undergone lymphovenous anastomosis, was admitted for evaluation of persistent nephrotic-range proteinuria. Autoimmune markers in the form of anti-nuclear antibodies, anti-double-stranded DNA and anti-neutrophil cytoplasmic antibody were negative; C3 was normal. Urine analysis revealed inactive sediment with moderate proteinuria. Both serum and urine electrophoresis were negative for paraproteins and bone marrow aspirate and biopsy were normal. Evidence of active filarial infection was established on the basis of microfilariae in the peripheral smear and a positive W. bancrofti antigen test. Kidney biopsy revealed renal amyloidosis when stained with Congo red and anti-AA immunostain. The patient's proteinuria improved on conservative management with angiotensin-converting enzyme inhibitors and a course of antifilarial drugs. His proteinuria returned to <1g/24h with normalization of renal function and no significant proteinuria on periodic follow-up at 6-month and 1-year intervals. Repeat kidney biopsy after 1.5years showed regression of amyloidosis. Repeat demonstration of filarial antigen and microfilariae in the peripheral smear were negative on multiple occasions during the follow-up period. Although various chronic infections can lead to secondary renal amyloidosis, this is the first case reported in world literature where secondary amyloidosis developed as a complication of chronic filarial infection due to W. bancrofti. This is probably also the first case reported in world literature where renal amyloidosis has an etiological association with W. bancrofti infection and where patient symptoms improved with antifilarial and antiproteinuric management.

The mitochondrial heat shock protein 60 (HSP60) is up-regulated inOnchocerca volvulusafter the depletion ofWolbachia

Wolbachia, a genus of endosymbiotic bacteria of filarial worms, represent novel targets for anti-filarial therapy. The efficacy of compounds against Wolbachia has been evaluated using antiserum raised against the 60 kDa heat shock protein (HSP60) which binds specifically to this protein in both Wolbachia and mitochondria. It has been shown that Wolbachia stains (using such specific probes) stronger than the mitochondria in untreated Onchocerca volvulus, whereas after the depletion of Wolbachia (with drugs) staining of the mitochondria is increased. Herein, immunogold electron microscopy showed that specific anti-HSP60 serum specifically labelled Wolbachia and filarial mitochondria, and that both have distinct localization patterns, thus allowing them to be differentiated. Immunohistochemistry of O. volvulus showed that HSP60 staining is increased in the mitochondria after Wolbachia depletion in the hypodermis, epithelia, muscles, oocytes, embryos, and developing spermatozoa. This could have been the result of the antiserum preferentially binding to the Wolbachia when they are present or due to increased expression of the protein in the absence of the bacteria. To address this, mRNA levels of filarial hsp60 in O. volvulus were measured. After the depletion of Wolbachia, the transcription of hsp60 was significantly greater (7.7 fold) compared with untreated worms. We hypothesize that the increased expression of HSP60 in the absence of Wolbachia is due to a disruption of the homeostasis of the endosymbiosis.

Prior killing of intracellular bacteria Wolbachia reduces inflammatory reactions and improves antifilarial efficacy of diethylcarbamazine in rodent model of Brugia malayi

The discovery of the endosymbiont Wolbachia, which has a mutualistic relationship with filarial nematodes, and its importance in filarial parasite biology has provided a lead for developing novel chemotherapeutic agents against human filariasis. Wolbachia also appears to be involved in immunopathological responses as well as adverse reactions after antifilarial therapy. The aim of the present study was to explore the potential of administering anti-Wolbachial therapy before antifilarial treatment to improve the filaricidal efficacy of the present-day filaricide diethylcarbamazine. An additional objective was to minimize host inflammatory reactions using a rodent model Mastomys coucha and Meriones unguiculatus infected with human lymphatic filariid Brugia malayi. We observed: (1) a 40-day treatment schedule of tetracycline alone resulted in delayed reduction in microfilaraemia and a low degree of macrofilaricidal efficacy; (2) tetracycline therapy followed by 100 mg/kg diethylcarbamazine (DEC) x5 days led to marked reduction in microfilaraemia from day 48 onward after initiation of treatment. The combination treatment also brought about approximately 70% death of adult B. malayi and sterilization of 82.3% of the surviving female worms, thus exhibiting remarkable enhancement in the antifilarial activity of DEC; (3) tissue inflammatory reactions and pathogenesis were significantly reduced as observed by histopathology, and peritoneal macrophage mediated oxidative burst shown by fluorescence-activated cell sorting (FACS) analysis using dichlorofluorescein diacetate (DCF-DA); and (4) the characteristic filarial antigen-specific and mitogen-specific cellular unresponsiveness was significantly reversed, possibly due to marked clearance of microfilaraemia. It is therefore advisable to give an anti-Wolbachial antibiotic trial before starting antifilarial therapy to achieve maximum benefits.

Wolbachia endobacteria depletion by doxycycline as antifilarial therapy has macrofilaricidal activity in onchocerciasis: a randomized placebo-controlled study.

In a randomized, placebo-controlled trial in Ghana, 67 onchocerciasis patients received 200-mg/day doxycycline for 4–6 weeks, followed by ivermectin (IVM) after 6 months. After 6–27 months, efficacy was evaluated by onchocercoma histology, PCR and microfilariae determination. Administration of doxycycline resulted in endobacteria depletion and female worm sterilization. The 6-week treatment was macrofilaricidal, with >60% of the female worms found dead, despite the presence of new, Wolbachia-containing worms acquired after the administration of doxycycline. Doxycycline may be developed as second-line drug for onchocerciasis, to be administered in areas without transmission, in foci with IVM resistance and in areas with Loa co-infections.

Retroperitoneal lymphatics on CT and MR

We report the CT and MRI appearances of dilated retroperitoneal lymphatic channels in six patients. In two patients, these dilated channels resembled a mass of confluent low-density lymph nodes on CT. On MR urography the lymphatic channels in all six patients were seen as a meshwork of multiple tubular, tortuous, fluid-filled structures in the retroperitoneum of the abdomen and pelvis. On axial T1W images, these channels were seen as numerous, interconnected small, nodular and streaky intensities and as a cloak of diffuse homogenous hyperintensity on T2W axial images. The lymphatic nature of these abnormalities was confirmed at surgery in one patient. In another patient, the calibre and number of the dilated retroperitoneal channels reduced following anti-filarial therapy. The remaining four patients presented with chyluria.

Povidone iodine and dextrose solution combination sclerotherapy in chyluria

Objectives To evaluate the effectiveness of combination (povidone iodine and 50% dextrose) renal pelvic instillation sclerotherapy (RPIS) as a minimally invasive therapy for chyluria resistant to conservative treatment. Methods A total of 50 patients with chyluria and hematochyluria (28 men and 22 women) were included in the study. Initially, all were offered conservative antifilarial drug therapy and dietary fat restriction. Intravenous urography was done in all cases to document normal renal functional status. In the patients in whom chyluria persisted after 3 weeks of conservative therapy, cystoscopic lateralization was done and a 5F open-ended ureteral catheter was positioned under local anesthesia. The same was left attached to a 16F Foley catheter for 3 days of RPIS. A solution of 5 mL of 5% povidone iodine and 5 mL of 50% dextrose was instilled twice a day with the patient in the Trendelenburg position for 3 days. In cases of bilateral efflux, the dominant side was treated first. The opposite side was subjected to a similar instillation sclerotherapy schedule after 6 weeks if chyluria persisted. Results Of the 50 patients, only 4 responded to conservative therapy. The remaining 46 patients underwent combination RPIS. The mean follow-up was 24 months. Complete remission of chyluria or hematochyluria occurred in 40 (87%) and persisted in 6 patients (13%). Of the 6 patients in whom symptoms persisted, 2 developed chyluria on the side opposite the one treated with RPIS. Another 2 patients developed recurrence on the same side after remaining asymptomatic for 6 months after RPIS. All four of these patients subsequently underwent chylolymphatic disconnection and nephropexy (two open and two laparoscopic) with a successful outcome. The final 2 patients with persistent symptoms were lost to follow-up. Conclusions Combination sclerotherapy using a 5% povidone iodine and 50% dextrose solution is a safe and cost-effective minimally invasive therapy for chyluria refractory to conservative treatment.

Tetracycline treatment and sex-ratio distortion: a role for Wolbachia in the moulting of filarial nematodes?

Filarial nematodes harbour intracellular bacteria of the genus Wolbachia. These bacteria are thought to be beneficial to the host nematode. Indeed, tetracycline treatments reduce the population of Wolbachia in filarial worms and have detrimental effects on the nematode. Even though various antibiotic-curing experiments have been performed on filariae, the actual role of Wolbachia in the biology of these nematodes is not yet clear. To address this issue, we designed a first experiment on a model filaria ( Brugia pahangi), maintained in the gerbil ( Meriones unguiculatus). In this experiment, timing of tetracycline treatment was set on the basis of the larval stage of the nematode. This first experiment showed that 2 weeks of treatment started after the L 4–L 5 moult of males, but before the moult of females, led to significant sex-ratio distortion of the nematodes. We thus hypothesised that tetracycline interferes with the moult in B. pahangi. To test this hypothesis, we designed a second experiment in which antibiotic treatments were started (1) before the moult of both sexes, (2) after the moult of males but before the moult of females, or (3) after the moult of both sexes. Treatment 1 determined a reduction of worm recovery with no sex bias. Treatment 2 led to a male-biased sex-ratio. Treatment 3 had no effect on either worm recovery or sex-ratio. These results thus support the hypothesis that tetracycline treatment interferes with the L 4–L 5 moult of B. pahangi. The nematodes recovered from the treated and control animals were examined for the presence of Wolbachia using both immunohistochemistry and real-time PCR. In general, nematodes from treated animals showed a dramatic reduction in Wolbachia content. In one group, Wolbachia depletion, as observed at the end of the treatment, was followed by a rebound to ‘normal’ values 160 days later. Prospects for antifilarial therapy using Wolbachia-targeted tetracycline treatments should thus take into account the possibility of Wolbachia rebound.

Diethylcarbamazine (DEC) Does Not Induce Nitric Oxide (NO) Synthesis

Rajan, T. V., Shultz, L. D., Babu, S., Doukas, J., Greiner, D., and Porte, P. 1998. Diethylcarbamazine (DEC) does not induce nitric oxide (NO) synthesis.Experimental Parasitology88, 217–222. Diethylcarbomazine (DEC) was discovered in 1947 as a potent therapeutic agent in lymphatic filariasis and has been a mainstay of antifilarial therapy over the past five decades (R. I. Hewitt,et al., 1947,Journal of Laboratory and Clinical Medicine32, 1304–1313). Several hundred million doses of this drug have been administered to people. Despite its widespread and successful use over this prolonged time scale, its mechanism of action remains obscure (R. M. Maizels and D. A. Denham, 1992,Parasitology105Suppl. 549–560). Numerous studies suggest that DEC has no direct effect on the parasite (F. Hawking and W. Laurie, 1949,Lancet2, 146–147) and that it exerts its action by stimulating host immune defense mechanisms (F. Hawkinget al., 1948,Lancet2, 730–731), or by activating host platelets to become microfilaricidal (J. Y. Cesbronet al., 1987,Nature325(6104) 533–536). Recent data from two different laboratories suggest that NO may be involved in host defense against filarial parasites (T. V. Rajanet al., 1996,Infection and Immunity64(8), 3351–3353; M. J. Tayloret al., 1996,Parasitology112, 315–322). We investigated whether DEC stimulates the production of NO from murine macrophages or rat endothelial cells. DEC did not stimulate the synthesis or secretion of NO from either, nor did it synergize with interferon-gamma or tumor necrosis factor-alpha in the induction of inducible NO synthase (iNOS). In addition, there was no consistent increase in the output of inorganic nitrate, the end product of NO metabolism, in the urines of rats treated with DEC. These data suggest that DEC does not achieve its therapeutic efficacy through the induction of host iNOS.

Microfilaria of Wuchereria bancrofti identified in pericardial fluid.

A case of pericardial effusion in which cytologic examination revealed numerous sheathed microfilariae of Wuchereria bancrofti is described. The patient had no symptoms suggestive of filarial infection in the past. Following antifilarial therapy, the effusion resolved and the patient became asymptomatic. The possible etiologic role of the microfilariae in the genesis of the effusion is discussed.

Use of Parasite Antigen Detection to Monitor Macrofilaricidal Therapy in Brugia malayi-Infected Jirds

Improved methods are needed to evaluate new treatments for filarial infections. We have recently developed a monoclonal antibody-based enzyme immunoassay to detect circulating parasite antigen in sera from Brugia malayi-infected jirds. In the present study, parasite antigen levels were compared to parasitological parameters after treatment of B. malayi-infected jirds with CGP 20376 that has been reported to be active against both microfilariae and adult worms of this parasite. Microfilariae were cleared promptly and permanently after CGP 20376 treatment, and no adult worm was recovered in jirds at necropsy 20 wk after treatment. In contrast, untreated animals had sustained microfilaremia throughout the course of the study, and adult worms were recovered in all control animals (mean worm recovery; 24.3 +/- 7.8 SE). Parasite antigen was present in sera from all infected animals before treatment. Parasite antigen titers in sera were unchanged 5 wk after treatment but fell to undetectable levels in 4 of 6 animals by 20 wk after treatment. Low-level antigenemia was detected in 2 of 6 animals at 20 wk, perhaps suggesting incomplete killing of parasites or incomplete clearance of antigen. Parasite antigen levels were stable throughout the study in control animals. These preliminary results suggest that parasite antigen detection is useful as a means of noninvasively monitoring the efficacy of anti-filarial drug therapy.

Persistence of parasite antigenemia following diethylcarbamazine therapy of bancroftian filariasis.

This study was designed to reexamine the efficacy of diethylcarbamazine for bancroftian filariasis with special reference to changes in serum parasite antigen levels and antifilarial antibody titers after treatment. Patients with asymptomatic microfilaremia were treated with 6 mg/kg diethylcarbamazine daily for 12 days. Microfilaria counts fell dramatically after treatment, as expected. IgG antibody titers to adult and microfilarial antigens of B. malayi were increased 1 month after treatment in most patients. Titers fell slowly to or below pretreatment levels, but remained positive during subsequent months. Parasite antigen levels, measured by monoclonal antibody-based enzyme immunoassay, decreased to 72%, 58%, 53%, and 48% of pretreatment values 1, 3, 6, and 12 months after diethylcarbamazine treatment, respectively. Parasite antigen levels decreased similarly in subjects with and without residual microfilaremia after treatment. These results suggest that diethylcarbamazine has only partial macrofilaricidal activity against W. bancrofti with this dosage schedule. The sustained, impressive reductions in microfilaria counts after treatment despite significant persistence of parasite antigenemia may be explained by sublethal effects of the drug on adult worms. We believe that parasite antigen detection represents a valuable new approach for monitoring the efficacy of antifilarial drug therapy which we hope will lead to improved use of existing drugs and aid in the evaluation of new drugs for filariasis.

Sequential alterations in the human eosinophil content of arylsulfatase B during therapy of Bancroftian filariasis

Since transient increases in blood eosinophilia of varying levels accompany diethylcarbamazine therapy of filariasis, possible qualitative alterations in such eosinophils were assessed in 21 patients from an area hyperendemic for Bancroftian filariasis. The activities of arylsulfatase B, peroxidase, and β-glucuronidase were assayed in sonicates of eosinophil-enriched peripheral blood granulocytes obtained prior to, on the eighth day of, and 10–14 days after antifilarial chemotherapy. The activities of arylsulfatase B, which were attributable largely to eosinophils, decreased significantly from 36.0 to 26.0 μg p-nitrocatechol generated/hr/10 6 eosinophils at the height of eosinophilia during therapy and rose significantly to 47.0 μg p-nitrocatechol generated/hr/10 6 eosinophils after therapy, while the levels of other enzymes were unchanged. The extent of fall in the arylsulfatase B level per eosinophil with therapy was unrelated to either the increase in eosinophil count or the magnitude of the maximal eosinophil count, which suggested that the fall was not simply a function of a lower content of arylsulfatase B in young eosinophils. The significant fluctuations in eosinophil arylsulfatase B activity and the increased variability in eosinophil cellular content of arylsulfatase B during therapy suggested that eosinophil degranulation may accompany the host response to the filarial infection initiated by antifilarial therapy.