Eosinophil Hyporesponse of Jirds Induced by Microfilariae of Brugia Pahangi

Male jirds (Meriones unguiculatus) were inoculated sc with 100 infective larvae of Brugia pahangi. After 16 weeks, the animals were reinoculated with a comparable number of organisms. Blood eosinophil responses during the 5 weeks subsequent to this attempt to reinfect were much lower than those of comparable naive animals, while the response to a heterologous infection (Toxocara canis) was comparable to that of controls. Mebendazole was given to infected animals for 2 weeks beginning 5 weeks (prepatent) or 16 weeks (patent) after infection. At comparable intervals after drug administration, the animals were reinoculated with infective larvae and the blood eosinophil response was measured over a 5 week period. The response in the animals treated during the prepatent period was higher than the untreated infected controls. Treatment during the patent period had no demonstrable effect. Jirds made artificially microfilaremic by intravenous inoculation of viable filaria before and after the standard infecting dose had a low eosinophil response to infective larvae

Plasma Levels of Diethylcarbamazine and Their Effects on Implanted Microfilariae of Brugia pahangi in Rats

ラット腹腔内にジエチルカルバマジン (DEC, 200mg/kg) を投与後, 血漿中のDEC濃度をガスクロマトグラフィーにて測定し, 血中ミクロフィラリア (mf) 数の変化との相関を調べた. ラットはDEC投与の1日前にB. pahangiのmf, 2×10^5隻を移入し, 人工的にmf血症状態にしておいた. DEC投与後, 30分から4時間の間, 血中のmf数は急激かつ有意に減少し, その後徐々に増加した. DECはラットにおいてB. pahangiのmf血症を一時的にではあるが直接的に抑制することができると考えられる.Plasma level of diethylcarbamazine (DEC) was measured by using gas chromatography and was compared to the changes of microfilaremia after an intraperitoneal injection with 200mg/kg of DEC in rats. The microfilaremia was induced artificially by an intravenous implantation with 2×10^5 Brugia pahangi microfilariae (mf) 1 day before DEC treatment. The rats treated with DEC showed a rapid and significant decrease in mf number in the circulation within 30 min, continued for 4hr, and then increased rapidly. DEC seemed to cause transsient but significant suppression of microfilaremia of B. pahangi in rats directly

Mechanisms of Acquired Immunity against Brugia pahangi : Inflammatory Cell Responses and Antibody Formation Following the Challenge Infection in Mice Immunized with Naive Infective Larvae

The mechanisms of resistance of immunized BALB/c mice to intraperitoneally challenged B. pahangi were examined. Mice developed significant resistance to challenge infection by immunization with naive B. pahangi infective larvae. Remarkable resistance was already established at 5 weeks after immunization and persisted at least until 12 weeks. Resistance in immunized mice appeared at the early phase of challenge infection (5 days post-inoculation) and became more remarkable on day 10 and 15 post-inoculation. Immunized mice showed higher inflammatory cell (lymphocytes, macrophages and eosinophils) responses against B. pahangi challenge infection than control mice at 5 and 10 days post-infection. At that time, immunized mice showed high levels of anti-B. pahangi IgG and IgM antibodies. Moreover, many killed or weakened larvae encapsulated with inflammatory cells (macrophages and eosinophils were predominant) were observed in the peritoneal cavities of immunized mice. These results suggest that the significant resistance to challenge infection in mice immunized by naive B. pahangi infective larvae is due to developed inflammatory cell responses and coexistence of specific antibodies

Cattle with a low bovine leukemia virus proviral load are rarely an infectious source

Bovine leukemia virus (BLV) is an etiological agent of fatal B-cell leukemia and malignant lymphoma in cattle. Cattle with higher BLV proviral loads represent a higher risk of both horizontal and vertical transmission. Therefore, quantifying the proviral load of BLV is important in identifying major infectious sources and protecting BLV-free cattle from exposure to infected cattle. In this study, we confirmed that cattle with very low BLV proviral loads did not transmit the virus to virus-free cattle under conventional conditions. We observed a total of 7 tests in which a BLV-infected bull was allowed to cohabit with 57 to 92 BLV-free cattle for 12 or 22 months. We then evaluated the frequency of viral transmission. A BLV-infected bull with a “very low proviral load” (i.e., fewer than 100 proviral copies/50 ng of genomic DNA) did not transmit the virus to any virus-free cattle in 2 out of 2 tests. However, a BLV-infected bull with a “low proviral load” (i.e., 100 to 500 copies/50 ng) transmitted the virus to a total of 3 virus-free cattle in 2 out of 5 tests. These results suggest that BLV-infected cattle with “very low proviral loads” do not transmit the virus under conventional conditions, while cattle with “low proviral loads” can transmit the virus, although at low rates. We believe that the results of this study will promote the construction of effective measures to prevent BLV infection and control the spread of BLV