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PubMed1987

Cell adherence to microfilariae of Onchocerca volvulus: a comparative study.

The conditions were examined for in vitro antibody-mediated adherence of granulocytes to microfilariae of Onchocera volvulus and Dirofilaria immitis. Reactivity in human sera from patients in endemic foci in Sudan was specific for O. volvulus and no reactions were observed with heterologous Onchocerca species or with Mansonella perstans. Microfilariae from skin, nodules or adult female worms were satisfactory targets for cell adherence, and the cells involved were almost exclusively eosinophils. The reaction was inhibited by indomethacin but not by nordihydroguaiaretic acid, an inhibitor of leukotriene production. Agents that slowed or stopped microfilarial motility (e.g. nifedipine, lidocaine, chloroquine) inhibited the reaction, probably by reducing target/cell contact. Ivermectin did not enhance the reaction, and in the absence of cells exerted only slight effects on the movement of microfilariae at higher concentrations (greater than 10 micrograms/ml). Antibody activity was labile, and did not persist well through freeze-thaw cycles. Some differences between homologous and heterologous mixtures (microfilariae/cells/serum) were seen but they could not be resolved satisfactorily. There were no apparent geographical differences between microfilariae from different foci in Sudan. In the D. immitis system neutrophils were the dominant cell type adhering to microfilariae, and the activity was stable to storage and freeze-thaw. No enhancement was detectable with diethylcarbamazine. Antibody activity was absorbable with microfilarial antigens and was reduced by agents that inhibited microfilarial motility. In dogs, adherence-mediating antibody was seen only in amicrofilaraemic animals with occult infection, and in only a minority of these sera. In humans the relationship to clinical findings was less clear, but patients with punctate keratitis were the most likely to have positive serum and were the most reactive in the assay. This system may therefore offer some insights into disease mechanisms in vivo, and its molecular mechanisms deserve further characterization.

Animals↗
PubMed1997

Ivermectin-induced killing of microfilariae in vitro by neutrophils mediated by NO.

Rat neutrophil granulocytes isolated after intraperitoneal casein injection of the donors exhibit high cytotoxic efficacy in vitro against microfilariae of Litomosoides carinii in the presence of ivermectin. Optimum effects of 80-90% killing of microfilariae were obtained with 100 ng ivermectin per milliliter and a microfilariae: cell ratio of 1:100. Spleen cells killed approximately 30% of the microfilariae under these conditions. Cytotoxic effects were independent of any adherence of the cell to the larvae. In contrast to the effects of spleen cells, cytotoxicity of neutrophils completely abrogated when cells and targets were separated by a membrane impermeable for the cells, suggesting a very short-living mediator in the latter case. Correspondingly, cytotoxic effects of neutrophils were completely inhibited by the addition of the arginine analogues NG-monomethyl-L-arginine and L-canavanine, indicating the involvement of reactive nitrogen intermediates. The nitric oxide scavenger hemoglobin also protected the microfilariae. Several compounds which are known to interfere with reactive oxygen intermediates were ineffective. An excess of ferrous ions in the medium in the presence of a reducing agent significantly reduced the cytotoxic efficacy of neutrophils.

Animals↗
PubMed1982

Fate of microfilariae of Dirofilaria immitis following use of levamisole as a microfilaricide.

A pretreatment liver biopsy was secured from each of three dogs with Dirofilaria immitis microfilariae counts of 29,500, 24,700, and 76,700/ml blood, respectively. Post-treatment biopsies were obtained 30 h later following treatment with a single dose of levamisole and a reduction in microfilariae counts of up to 80%. Both pre- and posttreatment biopsies were examined by light and electron microscopy. Microfilariae in dilated sinusoids of pretreatment liver biopsies were not degenerated and were unattended by an inflammatory reaction when examined by either method. However, degenerated microfilariae were present within granulomas in post-treatment liver biopsies examined by light and electron microscopy. Several stages of degeneration of microfilariae, including phagocytosis, were identified by the latter method.

Animals↗
PubMed2003

Doxycycline as a novel strategy against bancroftian filariasis-depletion of Wolbachia endosymbionts from Wuchereria bancrofti and stop of microfilaria production.

Chemotherapy of onchocerciasis by doxycycline, which targets symbiotic Wolbachia endobacteria, has been shown to result in a long-term sterility of adult female worms and corresponding absence of microfilariae. It represents an additional chemotherapeutic approach. The aim of this study was to determine whether a similar regimen would also show efficacy against Wuchereria bancrofti. Ghanaian individuals ( n=93) with lymphatic filariasis and a minimum microfilaremia of 40 microfilariae/ml were included in a treatment study consisting of four arms: (1) doxycycline 200 mg/day for 6 weeks; (2) doxycycline as in (1), followed by a single dose of ivermectin after 4 months; (3) ivermectin only; or (4) no treatment during observation period of 1 year (ivermectin at the end of the study). Doxycycline treatment resulted in a 96% loss of Wolbachia, as determined by real time PCR from microfilariae. After 12 months, doxycycline had led to a 99% reduction of microfilaremia when given alone, and to a complete amicrofilaremia together with ivermectin. In contrast, after ivermectin treatment alone a significant presence of microfilariae remained (9% compared to pretreatment), as known from other studies. This study shows that doxycycline is also effective in depleting Wolbachia from W. bancrofti. It is likely that the mechanism of doxycycline is similar to that in other filarial species, i.e., a predominant blockade of embryogenesis, leading to a decline of microfilariae according to their half-life. This could render doxycycline treatment an additional tool for the treatment of microfilaria-associated diseases in bancroftian filariasis, such as tropical pulmonary eosinophilia and microfiluria.

Adolescent↗
PubMed1984

Brugia malayi: stage-specific expression of carbohydrates containing N-acetyl-D-glucosamine on the sheathed surfaces of microfilariae.

Microfilariae, infective larvae, and adult worms of Brugia malayi were incubated with a panel of seven lectins in order to study the expression of surface carbohydrates. Infective larvae and adult worms did not bind any of the lectins utilized. Microfilariae, on the other hand, bound wheat germ agglutinin. The binding of this lectin was saturable and specific, and attributed to the presence of N-acetyl-D-glucosamine. In addition, microfilariae derived in vitro bound concanavalin A, indicating the presence of glucose and/or mannose on this stage of the parasite. The fact that similar concanavalin A binding was not seen on microfilariae recovered directly from the infected host implies that there is masking or loss of parasite surface antigens as microfilariae mature in vivo.

Acetylglucosamine↗
PubMed1977

Immunofluorescent reactions with microfilariae: 1. Diagnostic evaluation.

Microfilariae have been evaluated as antigen for the indirect immunofluorescent test in the diagnosis of filariasis. Sonicated, unlike whole, microfilariae present no problems in handling on a slide. The cytoplasmic antigen that is exposed by sonication, unlike the sheath or cuticular antigen, reacts with filariasis sera irrespective of whether or not there is a detectable microfilaraemia. The cytoplasmic antigen of microfilariae of various species was marginally superior to Dirofilaria adult worm as antigen for diagnostic immunofluorescence in respect of both sensitivity and specificity. The microfilariae extruded from the uterus of an adult D. immitis were a useful source. But the best results were obtained with the sonicated microfilariae of Brugia pahangi, with which it was possible to utilize both cytoplasmic and sheath antigens simultaneously, giving a positivity rate of 95% for filariasis infecions as a group. This test is thought to be the best available at present for the sero-diagnosis of filariasis, in spite of some lack of specificity. For individual filarial infections a homologous microfilarial antigen is probably the deal.

Antigens↗
PubMed1987

Immunochemical characterization and biosynthesis of major antigens of iodo-bead surface-labeled Brugia malayi microfilariae.

The objectives of the present study were to identify and characterize biochemically the major antigens of Brugia malayi microfilariae, a filarial parasite that infects humans. IgG antibodies in sera of mice which had cleared parasites from the bloodstream reacted with 30, 55, 94 and 150 kDa molecules of living microfilariae radioiodinated by the Iodo-bead method. Sera of humans infected with the related filariae Wuchereria bancrofti, Loa loa or Onchocerca volvulus immunoprecipitated molecules of similar size as well as two additional proteins of 22 and 43 kDa. Sera of uninfected North Americans or mice infected with Trichinella spiralis or Schistosoma mansoni did not recognize these radioiodinated antigens. Experiments to examine the possible surface localization and metabolism of these antigens showed that they were removed from intact parasites exposed to chymotrypsin or trypsin and that immunogenic molecules of 30, 55, and 150 kDa were released into excretory-secretory products by viable microfilariae. [35S]Methionine biosynthetically labeled polypeptide antigens of 22, 30, 35 and 150 kDa were detected by antibody reacted with intact microfilariae and/or their excretion products. Antigens of 30, 55, and 150 kDa appear to be glycoproteins as they bound wheat germ agglutinin and were biosynthetically labeled with [14C]N-acetyl-D-glucosamine. These data suggest that the surface of B. malayi microfilariae is a dynamic structure which synthesizes and sheds antigens.

Animals↗
PubMed1992

The expression of small heat shock proteins in the microfilaria of Brugia pahangi and their possible role in development.

Development of the microfilariae of Brugia pahangi in the mammalian host is blocked until uptake by a mosquito vector when the developmental cycle is re-initiated. Comparison of the profile of polypeptides labelled in microfilariae cultured at mammalian temperature (37 degrees C) or mosquito temperature (28 degrees C) revealed a complex of low-molecular-weight proteins (18 kDa and 22-24 kDa) synthesized only in microfilariae at 37 degrees C. The synthesis of these proteins was also induced by transfer of microfilariae to 41 degrees C (i.e., heat shock conditions), suggesting that these are heat shock proteins. The expression of the small heat shock proteins in the Brugia life cycle is developmentally regulated, as they are not observed in the mature adult female. Their synthesis is strictly temperature dependent and is repressed upon transfer of the microfilariae to 28 degrees C.

Aedes↗
PubMed1980

The distribution of microfilariae in the skin of Guatemalan onchocerciasis patients: an evaluation of diagnostic potentials.

Quantitative examinations for the distribution and density of microfilariae were carried out on male Guatemalan onchocerciasis patients by taking 6 or 13 skin biopsies each from 74 subjects. We found that microfilariae were distributed most frequently on the iliac crest and secondarily in the scapular region; higher detection rates and greater microfilarial densities were seen in these areas. From these results we recommend the taking of biopsies from both of these anatomical regions so as to avoid false negative cases. The infected patients were classified into 3 groups (light, moderate and heavy infections) on the basis of the numbers of negative skin snips out of the 13 biopsies taken. In heavy infections, a higher densities of microfilariae were detected in the head and neck regions, as compared with the densities in the lower extremities (calf). The high concentration of microfilariae in these regions is of importance in relation to the development of eye lesions and/or transmission. Of patients who had microfilariae in the anterior segment of the eye some had negative skin biopsies frm the outer canthus, retroauricular region and neck.

Biopsy↗
PubMed1982

Immunization of calves against the microfilariae of Onchocerca lienalis.

Three Jersey bull calves were immunized by subcutaneous injections of sonicated Onchocerca lienalis microfilariae suspended in phosphate buffered saline, and three control animals were injected with medium only. All calves received booster injections 27 days later, and were challenged with live microfilariae 44 days after the booster. Following challenge, only the immunized animals developed an elevated level of circulating eosinophils. When necropsied ten days after challenge there was a 97% reduction in recoveries of microfilariae from immunized animals compared to challenge controls. In human onchocerciasis it is the microfilariae which are the principal cause of pathology, and we believe that studies on O. lienalis in both the natural bovine host and in inbred rodents provide a promising model to investigate immunity to Onchocerca microfilariae.

Animals↗
PubMed1984

Biochemical surface components of Brugia pahangi microfilariae.

The sheath and cuticle of microfilariae of Brugia pahangi were examined by electron microscopy and the presence of various proteins, carbohydrate and enzymes sought. The epicuticle of microfilariae consists of a pentalaminate structure (24.0 +/- 1.4 nm), a cortex (13.7 +/- 3.6 nm) and a basal zone (27.8 +/- 4.8 nm) which is often banded in appearance. The pentalaminate layers are not continuous at the base of the interannular grooves. The sheath and the epicuticle of B. pahangi stained positively with concanavalin A and saccharated iron oxide. The sheath of approximately 50% of microfilariae showed activity for acid phosphatase, 5' nucleotidase and peroxidase, but not for ATPases, alkaline phosphatase or esterase. No enzymes were detected in the epicuticle although the cortex and basal layers of the cuticle did show enzymic activity. Structures beneath the cuticle in the main body of the worms contained considerable enzymic activity. Microfilariae directly isolated from the blood of infected cats were found by immunochemical means to carry serum proteins on their sheaths but not on their cuticles. These studies extend the definition of the outer structures of microfilariae and confirm that they significantly differ in morphology and enzyme content from typical mammalian cell membranes.

Acid Phosphatase↗
PubMed1998

Tropomyosin implicated in host protective responses to microfilariae in onchocerciasis.

A cDNA from adult female Onchocerca volvulus encoding the C-terminal portion of a tropomyosin isoform (termed MOv-14) has been shown previously to confer protective immunity in rodent models of onchocerciasis. The full-length sequence (designated Ov-tmy-1) obtained by PCR amplification, codes for a protein of 33 kDa and shares 91% identity with tropomyosins from other nematodes, falling to 57% identity with human alpha-tropomyosin. Ov-TMY-1 migrates with an apparent molecular mass of 42 kDa on SDS/PAGE and is present in all life-cycle stages, as determined by immunoblotting. Immunogold electron microscopy identified antigenic sites within muscle blocks and the cuticle of microfilariae and infective larvae. Anti-MOv14 antibodies were abundant in mice exhibiting serum-transferable protection against microfilariae conferred by vaccination with a PBS-soluble parasite extract. In contrast, little or no MOv14-specific antibody was present in mice inoculated with live microfilariae, in which resistance is mediated by antibody-independent mechanisms. In human infections, there was an inverse correlation between anti-tropomyosin IgG levels and densities of microfilariae in the skin. Seropositivity varied with the relative endemicity of infection. An immunodominant B cell epitope within Ov-TMY-1 (AQLLAEEADRKYD) was mapped to the N terminus of the MOv14 protein by using sera from protectively vaccinated mice. Intriguingly, the sequence coincides with an IgE-binding epitope within shrimp tropomyosin, believed to be responsible for hypersensitivity in individuals exhibiting allergy to shellfish. IgG and IgE antibodies reacting with the O. volvulus epitope were detected in human infections. It is concluded that antibody responses to tropomyosin may be important in limiting microfilarial densities in a proportion of individuals with onchocerciasis and have the potential to mediate hypersensitivity reactions to dead microfilariae, raising the possibility of a link with the immunopathology of infection.

Adult↗
PubMed1983

Chemotaxis of human granulocytes toward microfilariae of Onchocerca volvulus.

Migration of human peripheral blood granulocytes in response to microfilariae of O. volvulus was demonstrated using modified Boyden chambers. Granulocyte migration was significantly enhanced when microfilariae were preincubated with heat-inactivated immune serum (delta IS), then added to a fresh serum source (P less than 0.025). This effect was not seen when microfilariae were incubated in medium alone, in delta IS alone, in delta IS plus C4-deficient guinea-pig serum, or in fresh serum alone. There was no significant difference between the response of cells from O. volvulus-infected donors and that of cells from normal volunteers. Likewise, there was no significant difference between the migratory response seen toward nodule- versus skin-derived microfilariae. These results suggest that the host inflammatory response to O. volvulus microfilariae is mediated in part by chemotactic factors generated by antibody and complement interaction with the organism and, furthermore, that these factors are product(s) of classical complement pathway activation.

Animals↗
PubMed1990

Efficacy of avermectin B1 given orally against equine intestinal strongyles and Onchocera microfilaria.

Three groups of horses and ponies (N = 13, 13 and 12) were treated with ivermectin paste (0.2 mg/kg p.o.), avermectin B1 solution (0.2 mg/kg p.o.), or fenbendazole suspension (10 mg/kg via nasogastric tube). The avermectin B1 was a 1% solution in a propylene glycolglycerol formal base. Faecal strongyle egg counts were performed before, and 14, 28, 42, 56 and 70 d, after treatment. Full-thickness skin biopsies from the neck, pectoral and umbilical regions were examined for Onchocera microfilaria before treatment, and again 14 and 70 d later. Ivermectin therapy produced a significant (P less than 0.01) decrease in mean strongyle egg counts 14, 28, 42 and 56 d after treatment. Avermectin B1 therapy resulted in significant (P less than 0.01) decreases in mean strongyle egg counts 14, 28 and 42 d after treatment. All horses given ivermectin or avermectin B1 had zero strongyle egg counts 14 and 28 d after treatment. Fenbendazole failed to significantly decrease strongyle egg counts. Both ivermectin and avermectin B1 resulted in zero microfilaria counts in all horses 14 d after treatment. On day 70 the percentage decrease in microfilaria counts were 100% and 99.6% respectively. Fenbendazole failed to significantly decrease microfilaria counts. The oral administration of this formulation of avermectin B1 appeared to be highly efficacious against intestinal strongyles and Onchocera microfilaria. The duration of anti-strongyle activity was, however, significantly (P less than 0.01) shorter than that of ivermectin paste.

Administration, Oral↗
PubMed1997

Protective responses against skin-dwelling microfilariae of Onchocerca lienalis in severe combined immunodeficient mice.

Inoculation of severe combined immunodeficient (SCID) mice with microfilariae of Onchocerca lienalis results in a sustained infection of the skin, extending for months beyond the point at which the parasites are eliminated from immunocompetent BALB/c controls. Reconstitution of SCID mice with spleen cells, thymocytes, or CD4+-cell-enriched splenocytes from naive BALB/c donors confers the ability to mount a protective immune response, leading to the rapid elimination of microfilariae. High levels of interleukin-5 and low levels of gamma interferon in the sera of reconstituted SCID mice during the destruction of microfilariae suggest that this protective immune response is directed by Th2 lymphocytes, mirroring that observed in immunocompetent controls. Unexpectedly, abbreviation of primary infections of unreconstituted SCID mice with the drug ivermectin induces resistance to reinfection with microfilariae at a level equivalent to that induced in secondarily infected, immunocompetent controls. In contrast to protection mediated by adoptive reconstitution, resistance induced by ivermectin-abbreviated infection occurs in the absence of T cells and in association with negligible levels of serum interleukin-5 and gamma interferon. This points to the activation of some alternative host defense mechanism that operates after the clearance of therapeutic levels of drug. Such a response could have important implications for the treatment of human onchocerciasis and may go some way in explaining the long-term suppression of microfilariae observed in patients after treatment with ivermectin.

Animals↗
PubMedDate not supplied

Microfilariae in association with other diseases. A report of six cases.

BACKGROUND: Lymphatic filariasis is a major public health problem in tropical countries. Earlier reports have reported microfilariae as an incidental finding in body fluids and fine needle aspiration smears from various sites. CASES: The findings of body fluid cytology and fine needle aspiration smears from six patients with microfilariae in association with other conditions--tubercular pleural effusion/lymphadenitis, pregnancy and non-Hodgkin's lymphoma--are presented. Three patients demonstrated an associated eosinophilic cellular exudate. Adherence of inflammatory cells to microfilariae was seen in two patients. CONCLUSION: Although microfilariae in cytologic smears are considered incidental findings, the association of microfilariae with debilitating conditions suggests that it is an opportunistic infection and needs further study.

Adolescent↗
PubMed1982

Light and electron microscopic pulmonary lesions associated with retained microfilariae in canine occult dirofilariasis.

Lungs from dogs infected with adult, gravid Dirofilaria immitis but without microfilaria circulating in systemic vessels were studied by light and transmission electron microscopy. Microfilariae were seen within the pulmonary microvasculature and in interstitial areas of interalveolar septa. An acute inflammatory reaction characterized by aggregates of eosinophils, neutrophils, macrophages and lymphocytes was associated with intact microfilariae. Necrotic and fragmented microfilariae were surrounded by macrophages and epithelioid cells. Other lesions in interalveolar septa of dogs with chronic occult dirofilariasis included endothelial degeneration and hypertrophy, perivascular aggregates of plasma cells, hypertrophy and hyperplasia of smooth muscle cells, and interstitial fibrosis. The findings suggest that a cell-mediated hypersensitivity reaction is at least partially responsible for retention of microfilariae in pulmonary parenchyma of dogs with occult dirofilariasis.

Animals↗
PubMed1974

The prevalence of trypanosomes and microfilariae in Panamanian monkeys.

A total of 3,523 wild caught monkeys from Panama was examined for blood parasites from August 1968 through June 1972. Trypanosomes or microfilariae were observed in the blood of 31.1% of the monkeys. Mixed infections, with microfilariae and trypanosomes, were detected in 6.6% of the animals. Trypanosoma cruzi was found in marmosets. Saguinus geoffroyi (12.2%), in white-faced capuchins, Cebus capucinus (5.0%), in squirrel monkeys, Saimiri sciureus (1.7%) and in black spider monkeys, Ateles fusciceps (1.2%). Trypanosoma rangeli was found in S. geoffroyi (55.8%) and C. capucinus (12.5%). Other trypanosomes found in Panamanian monkeys included T. minasense, and T. mycetae. Saguinus geoffroyi showed the highest infection rate (88.9%) with trypanosomes and/or microfilariae; trypanosomes were seen in 68.1%, and microfilariae in 73.0%, of the animals examined. The marmosets, white-faced capuchins, and squirrel monkeys should be considered as significant hosts of T. cruzi in sylvatic habitats and may serve as reservoir hosts of Chagas' disease in Panama. The microfilariae seen in monkeys from Panama were tentatively identified as larval forms of Dipetalonema gracile in Aotus trivirgatus; D. obtusa in C. capucinus and S. geoffroyi; and D. marmosetae in Alowatta villosa, C. capucinus, A. trivirgatus, S. sciureus, A. fusciceps, and S. geoffroyi.

Animals↗