Nayar JK et al. (1989) J Med Entomol "Intracellular melanization in the mosquito Anopheles quadrimaculatus (Diptera: Culicidae) against the filarial nematodes, Brugia spp. (Nematoda: Filarioidea)."

Nayar JK, Vickery AC, Knight JW

[J Med Entomol, 1989]

Intracellular melanization responses to developing larvae of Brugia species (B. malayi (Buckley), B. pahangi (Buckley and Edeson), and B. patei (Buckley, Nelson, and Heisch] in the thoracic muscle fibers of eight strains of Anopheles quadrimaculatus Say were first observed 48 to 72 h after an infective blood meal. Three to 4 d later, large numbers of melanized first-stage larvae were found within the thoracic muscle fibers. These intracellular responses were in addition to the extracellular responses to microfilariae and microfilarial sheaths of B. pahangi in the abdominal hemocoel of An. quadrimaculatus described in literature. Simultaneously, normal development of larvae of the three Brugia species also was observed in all eight strains of An. quadrimaculatus. Comparisons of melanized first-stage larvae and normally developing larvae of the three Brugia species in the thoracic muscle fibers of the eight strains of An. quadrimaculatus showed that there were distinct variations in numbers of melanized and developing larvae and percentage of females with melanized and developing larvae in different strains. Numbers of melanized first-stage larvae reflected the extent of refractoriness of An. quadrimaculatus strains. Fully melanized larvae showed no abnormalities in parasite organelles, indicating that refractoriness is due to an enhanced ability of the host to recognize the living parasite. Further comparison among the strains suggested that the mutants, Yellow Larvae and Vero Beach Colony were significantly more susceptible, and Red Stripe was the most refractory to all three Brugia species. Thus, the gene(s) controlling susceptibility and refractoriness to all three Brugia species probably occurs on the same autosomal chromosome as the mutations in these strains. The significance of intracellular melanization of filarial larvae is discussed with reference to the melanization responses to different parasites in other mosquitoes.

Vickery AC et al. (1985) Acta Trop "Differential pathogenicity of Brugia malayi, B. patei and B. pahangi in immunodeficient nude mice."

Albertine KH, Nayar JK, Vickery AC

[Acta Trop, 1985]

Immunodeficient nude mice chronically parasitized by subperiodic Brugia malayi developed an elephantoid appearance with persistent lymphoedema of limbs and massive lymphangiectasis of subcutaneous vessels containing viable adult worms. Removal of worms reversed the process. The syndrome was not caused by B. patei or B. pahangi and was not correlated with the presence or absence of microfilaremia. Histologic examination of elephantoid mice revealed dilated and tortuous lymphatics containing small nonobstructive lymph thrombi composed of small mononuclear cells and multinucleate giant cells. Draining lymph nodes were not enlarged or congested and mast cells in oedematous tissue were not degranulated. Analysis of lymph aspirated from dilated lymphatics showed increased total protein content: bacterial sepsis was not detected. This work suggests that viable adult B. malayi exert direct pathologic effects upon lymphatics and that this parasite is more pathogenic than related Brugia spp.

Vickery AC et al. (1991) Acta Trop "Histopathology of Brugia malayi-infected nude mice after immune-reconstitution."

Vickery AC, Kwa BH, Nayar JK, Albertine KH

[Acta Trop, 1991]

Long term (greater than 200 day) Brugia malayi-infected nude mice with grossly dilated lymphatics were reconstituted with 10(8) primed spleen cells from heterozygous donors. Histological and ultrastructural examination at 7, 14, 21 and 28 days post-reconstitution revealed progressive fibrosis, obliterative lymph thrombus formation, interstitial infiltrates and extensive perilymphangitis. Formation of lymph thrombi/granulomas was associated with killing of adult worms and microfilariae, and the predominant cell types involved were large granular macrophages. Langhan's giant cells and eosinophils. Thus, the ability to initiate the formation of obstructive lesions in the dilated lymphatics of chronically parasitized nude mice by immunological reconstitution, suggests that several complex mechanisms might operate in stages to cause filarial elephantiasis.

Rao UR et al. (1990) Exp Parasitol "Brugia malayi and Brugia pahangi: transmission blocking activity of ivermectin and brugian filarial infections in Aedes aegypti."

Nayar JK, Kwa BH, Rao UR, Vickery AC

[Exp Parasitol, 1990]

Brugia malayi- or Brugia pahangi-infected, microfilaremic jirds (Meriones unguiculatus) were treated with ivermectin at a single dose of 200 micrograms/kg body weight, administered subcutaneously. After different time intervals, Aedes aegypti mosquitoes were fed on treated or untreated jirds. Sausage stage, L2, and L3 larvae failed to develop in mosquitoes that fed on jirds from 15 to 30 days post-treatment. After 1 month, the numbers of L3 larvae recovered from mosquitoes fed on treated B. pahangi jirds were comparable to controls. However, the number of L3's recovered from mosquitoes fed on B. malayi jirds remained significantly lower than controls, 2 and 3 months after treatment. This reduction suggests that ivermectin may be more effective in blocking transmission of B. malayi than B. pahangi. Ivermectin treatment had no effect on the mean number of circulating microfilariae in treated jirds. Therefore, mosquitoes ingested comparable numbers of microfilariae when compared to those mosquitoes fed on untreated controls. Only in the case of jirds infected with B. malayi did the circulating microfilarial counts fall 30 days after treatment. The failure of microfilariae to develop to the L3 stage in mosquitoes fed on jirds within 30 days of treatment was not due to failure of mosquitoes to ingest microfilariae. Brugia malayi microfilariae also failed to develop to L3 in mosquitoes that were allowed to feed on microfilaremic jird blood treated with ivermectin (50 ng/ml) in vitro, indicating its efficacy at low concentrations. In addition to N-acetyl glucosamine, microfilariae obtained for a period of 15 days from ivermectin-treated but not control jirds showed D-mannose, N-acetyl galactosamine, and L-fucose moieties on the surface of the sheath.(ABSTRACT TRUNCATED AT 250 WORDS)

Chikilian ML et al. (1994) J Parasitol "Ultrastructural comparison of extracellular and intracellular encapsulation of Brugia malayi in Anopheles quadrimaculatus."

Chikilian ML, Bradley TJ, Knight JW, Nayar JK

[J Parasitol, 1994]

Ultrastructural aspects of extracellular humoral encapsulation of microfilariae of Brugia malayi in the hemocoel of Anopheles quadrimaculatus were compared with those of intracellular encapsulation of first-stage larvae (L1) of the same parasite species, in the thoracic muscle cells of the same species of mosquito. The results showed that extracellular humoral encapsulation of microfilarial sheaths, and sheathed and exsheathed microfilariae, in the hemocoel of mosquitoes occurs around the parasite within the first 6 hr postingestion, apparently without initial participation of hemocytes. Hemocytes and their remnants were observed near the parasite during the first 6 hr postingestion. Within the next 24 hr, hemocytes attach to the initial humoral capsule. By contrast, intracellular encapsulation of L1S is initiated by the accumulation of a dense cytoplasmic layer derived from the infected thoracic muscle cell. Melanin deposits accumulate in this layer adjacent to the parasite cuticle, again without visible participation of hemocytes.

Rao UR et al. (1990) Int J Parasitol "A direct fluorescence technique for the rapid detection of sheathed microfilariae in blood smears."

Rao UR, Vickery AC, Nayar JK, Lowrie RC, Kwa BH

[Int J Parasitol, 1990]

Thick and thin blood smears containing microfilariae of Wuchereria bancrofti, Loa loa, Brugia malayi, Brugia pahangi, Brugia patei or Acanthocheilonema viteae were prepared from either cryopreserved blood samples or from freshly collected blood, fixed in methanol and treated with a fluoresceinated lectin wheat germ agglutinin. Sheathed microfilariae of W. bancrofti, L. loa, B. malayi, B. pahangi and B. patei in the blood smears could be easily detected and counted using a fluorescence assay. The unsheathed microfilaria of Acanthocheilonema viteae did not fluoresce. The possibility of adapting this technique, which does not require the use of parasite specific antibody for the sensitive, parasitological detection of filarial infections, is discussed.

Rao UR et al. (1992) Parasitol Res "Effect of carrageenan on the resistance of congenitally athymic nude and normal BALB/c mice to infective larvae of Brugia malayi."

Vickery AC, Rao UR, Kwa BH, Nayar JK, Subrahmanyam D

[Parasitol Res, 1992]

Resistance of BALB/c mice to infective third-stage larvae (L3) of the human filarial parasite Brugia malayi is thymus-dependent, although the actual effector mechanisms that mediate larval killing are unknown. The present study examined the effect of carrageenan (CGN) on the mechanisms of resistance to B. malayi infection in heterozygous (nu/+) and nude (nu/nu) mice. Mice were treated with CGN at a single dose of 20 or 200 mg/kg and were inoculated intraperitoneally 1 day later with 100 L3. The results showed a dose-dependent increase in the numbers of L4 and L5 that were recovered from nu/+ and nu/nu mice. CGN treatment also enhanced the recovery of mature adult worms from nu/nu mice and appeared to abolish partially the dichotomy of resistance between the usually more susceptible male and the more resistant female nu/nu mouse. Microfilariae were found in the peripheral blood and the peritoneal cavity of CGN-treated male and female nu/nu mice and in the peritoneal cavity of male but not female nu/+ mice. Fewer larval granulomas were recovered from the peritoneal cavity of treated mice. CGN-treated, parasitized nu/+ and nu/nu mice showed high titers of IgM and IgG antibodies. An experimental compound, CGP 20376, showed 100% larvicidal activity following the administration of a single dose of 20 mg/kg to CGN-treated mice. From this study, we conclude that macrophages alone or in conjunction with other cells are actively involved in the resistance of mice to B. malayi L3.