Mercury enhances susceptibility to murine leishmaniasis

The genetic background of mice infected with Leishmania major determines the response to infection, resulting in a resistant or susceptible phenotype. Susceptible mice develop a T-helper type 2 (Th2)-type immune response following infection distinguished by the development of interleukin (IL)-4 secreting T cells in the lymph node and spleen. In SJL mice, which normally heal L. major lesions, subtoxic doses of mercury induce an autoimmune syndrome characterized by an expansion of Th2 cells. In this study, we examined the effect of mercury administration on the outcome of L. major infection in SJL mice. We show that subtoxic doses of mercuric chloride (HgCl2) exacerbate disease outcome in SJL mice resulting in increased footpad swelling and increased parasite burdens. Furthermore, the effects of HgCl2 treatment on resistance to L. major are time-dependent. The nonhealing phenotype was observed only if mice had been treated with HgCl2 prior to L. major infection for at least 1 week, a timepoint at which mice treated with HgCl2 alone had increased splenocyte IL-4 production. HgCl2 treatment also increased production of serum immunoglobulin (Ig)E and IgG1, two IL-4 dependent isotypes. These results show that HgCl2 treatment enhances the susceptibility to L. major in SJL mice, consistent with the induction of host Th2 parameters. These findings have implications for the role of mercury contamination in areas of endemic leishmaniasis.     

Higher IL-10 levels are associated with less effective clearance of Plasmodium falciparum parasites

The implications of high levels of the immune regulatory cytokine IL-10 in Plasmodium falciparum malaria are unclear. IL-10 may down-regulate pro-inflammatory responses and also exacerbate disease by inhibiting anti-parasitic immune functions. To study possible inhibiting effects on parasite clearance, IL-10 plasma levels were determined in 104 Tanzanian children, 1 to 4 years old, with acute uncomplicated P. falciparum malaria, and analysed for association with parasite densities during 3 days of anti-malarial treatment. Higher baseline IL-10 plasma levels were associated with statistically significantly higher parasite densities after 24, 48 and 72 h of treatment. These associations could not be explained by differences in initial parasitaemia, temperature, age, sex or type of treatment. Induction of high IL-10 production might be a direct or indirect mechanism whereby the parasite evades the immune response.     

Evaluation of the antimalarial properties and standardization of tablets of Azadirachta indica (Meliaceae) in mice

The antimalarial activities of the tablet suspension of the bark and leaf of Azadirachta indica were evaluated on Plasmodium yoelli nigeriensis infected mice. The tablet suspensions exhibited high prophylactic, mode-rate suppressive and a very minimal curative schizonticidal effect. No animal was cured of the infection in the curative test and there was not much increase in the survival time of the animals compared with the control. The tablet suspensions from the leaf and bark at a concentration of 800 mg/kg and chloroquine at a concentration of 62.5 mg/kg body weight produced average percentage (%) parasitaemia of 79.6%, 68.2% and 99.5% for leaf, bark and chloroquine, respectively, in chemosuppression. Also in the prophylactic treatment, the tablet suspensions at 800 mg/kg and pyrimethamine at a concentration of 0.35 mg/kg gave an average parasitaemia reduction of 75.3%, 65.6% and 98.3% for the leaf, bark and pyrimethamine, respectively. There was a clear indication that both tablet suspensions from the leaf and bark possess antimalarial activity and a suspension from the former is relatively more effective than the bark. Extrapolation of the results from the antimalarial activity of the tablet suspension of the crude plant parts showed that an adult human would need to ingest a minimum of 48 g of the powdered plant material per day, an amount that is impracticable. A survival index value of 0.33 was obtained with the 800 mg/kg dose level, indicating that the tablet suspension has some moderate beneficial effect.     

Immunity to coccidia in chickens: adoptive transfer with peripheral blood lymphocytes and spleen cells

Suspensions of cells prepared from the caecal tonsils and spleen, and the peripheral blood lymphocytes of chickens immune to Eimeria maxima , were tested for their ability to transfer resistance to syngeneic recipients. The intravenous injection of approximately 6 × 10⁸ spleen cells or peripheral blood lymphocytes caused a significant reduction of oocyst production by the challenged recipients, in comparison with controls which were uninjected or given cells from birds susceptible to E. maxima. Peripheral blood lymphocytes appeared to be most effective when obtained 10–15 days after a primary, or 3–10 days after a secondary inoculation of oocysts. The peripheral blood lymphocytes which participate in the early response to challenge of immune birds were not found to be protective. When given intraperitoneally, greater numbers of spleen cells were required to reduce oocyst production, and small numbers of caecal tonsil cells were ineffective. The ability of the various cell suspensions to transfer antibody and cell-mediated responses was monitored with 'marker' antigens. There was some indication that both types of response were involved in protection.     

黄淮平原河网地区间日疟防治方法的研究

鹿邑县观堂乡是黄淮平原河网地区,历史上曾不断出现间日疟暴发流行。1970年,该乡发病率为43.33%。经过积极防治,1980年发病率降为1.35%。1981～1985年,采取以消灭传染源,保护易感人群和减少人蚊接触的综合性防治方法,1985年,疟疾发病率为0.73‰,较1981年的44.07‰下降98.35%,疫区明显缩小。该项研究,为同类型疟区深入开展防治工作提供了经验。     

中韩蠕虫病防治调查

采用多种检查方法以进一步调查少数民族居民寄生虫感染的种类，感染率，感染度。结果：查出寄生虫１２种，感染一种虫的占８６．８％，二种虫的占１３．２％，居民平均感染率为３０．９％，其中蛔虫为１０．８％，晓虫为３９．３％，其余低于１０％，华枝睾吸虫的感染率属中度、线虫、原虫、绦虫均属轻度。男性感染率为２８．１％，女性为２４．６％，中间宿主－纹沼螺全部阴性，鱼感染率为０．４％，提示：不同年龄组人群体内虫种构     

Ocular toxoplasmosis in the immunocompromised host

Disseminated toxoplasmosis is a well-known complication of immunodeficiency states, including those induced by malignancies, steroid and cytotoxic drug therapy, and AIDS. In immunodeficient patients, toxoplasmic infections of the eye are less common than toxoplasmic infections of other organs for unknown reasons. When ocular toxoplasmosis does occur in the immunodeficient host, or if immunosuppressive therapy is administered to patients with active disease, widespread tissue destruction by proliferating organisms may result. Immunodeficiency alone may not be sufficient, however, to cause reactivation of encysted organisms in retinochoroidal scars.Ocular toxoplasmosis in the immunocompromised host presents difficult problems in diagnosis and management. There may be a variety of clinical lesions, including single foci of retinochoroiditis in one or both eyes, multifocal lesions, or diffuse areas of retinal necrosis. The majority of lesions do not arise from the borders of preexisting scars, which suggests that they result from acquired infection or dissemination of organisms from nonocular sites of disease.Toxoplasma gondii may infect iris, choroid, and vitreous-tissues that are not usually infected in the immunocompetent host. Ocular lesions appear to respond to standard antiparasitic drug therapies, but continued treatment is probably necessary to prevent reactivation of disease in the most immunocompromised patients. The best treatment regimens have yet to be determined. Histopathologic studies show little retinal inflammation; therefore anti-inflammatory drugs, such as oral steroids, probably have no role in the management of infection.     

卢湾区人体重要寄生虫感染调查

目的了解卢湾区居民寄生虫感染情况,为今后中心城区开展寄生虫病防治提供科学依据。方法采用改良加滕厚涂片法查肠道蠕虫卵,抗原皮内实验查肺吸虫,用ELISA方法查弓形虫和丝虫短程抗体,间接免疫荧光法(IFA)查隐孢子虫感染。结果肠道寄生虫感染率0.44%,肺吸虫皮试阳性率0.84%,孕妇弓形虫抗体阳性率2.85%,隐孢子虫感染率4.80%,丝虫抗体阳性率0.32%。结论中心城区存在各种寄生虫感染,针对各种寄生虫感染途径积极开展寄生虫病健康教育,对防治寄生虫病具有重要意义。     

Immunopathology of intestinal helminth infection

The relationship between intestinal pathology and immune expulsion of gastrointestinal nematodes remains controversial. Parasite expulsion is associated with intestinal pathology in several model systems and both of these phenomena are T cell dependent. However, while immune expulsion of gastrointestinal helminth parasites is usually associated with Th2 responses, the effector mechanisms directly responsible for parasite loss have not been elucidated. In contrast, the intestinal pathology observed in many other disease models closely resembles that seen in helminth infections, but has been attributed to Th1 cytokines. We have used infection with the nematode Trichinella spiralis in mice defective for cytokines to demonstrate that although parasite expulsion is indeed IL-4 dependent, contrary to expectations, the enteropathy is also regulated by IL-4. Furthermore, abrogation of severe pathology in iNOS deficient and TNF receptor defective animals does not prevent parasite expulsion. TNF and iNOS are therefore involved in intestinal pathology in nematode infections, apparently under regulation by IL-4 and Th2 mediated responses. Therefore, it appears that the IL-4-dependent protective response against the parasite operates by a mechanism other than merely the gross degradation of the parasite's environment brought about by the immune enteropathy. However, it remains important to elucidate the protective mechanisms involved in parasite expulsion, which are still unclear.