Antibody isotype responses to Trichuris infection in humanized SCID mice

We have developed a humanized SCID mouse model of trichuriasis involving the injection of peripheral blood lymphocytes (PBLs) from normal healthy donors into C. B.-17 severe combined immunodeficiency (SCID) mice followed by vaccination and infection of these mice with the murine species of Trichuris, Trichuris muris . Optimal results with respect to parasite specific antibody production and peripheral engraftment were achieved by injecting intraperitoneally 2 × 10⁷ PBLs which had been incubated overnight on anti-human CD3 coated plates. Mice were immunized three weeks post reconstitution with parasite antigen in Freund's Incomplete Adjuvant and infected two weeks later. At autopsy human T cells could be detected in the spleens of engrafted animals and anti- T. muris antibody detected. The dominant IgG isotype responses were shown to be IgG1 and IgG2, providing a similar IgG isotype profile to that seen in humans infected with T. trichiura in the field. In several cases engrafted animals showed the remarkable ability to expel their parasite load. The model will thus be useful for analysing human immune responses to trichuriasis under highly controlled laboratory conditions impossible to achieve in the field .     

Immunogenic proteins of Leishmania major during mouse infection

Mice of different strains (C3H/He, A/Jax, DBA/2, BALB/c and CBA/Ca) were infected intracutaneously with Leishmania major. Antibody production was analysed on the antigens of the promastigote form of the parasite which had previously been separated by SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose sheets. The kinetics of IgG antibody production were determined and the major immunogenic proteins of the parasite were identified for each strain of mouse. It was found that: 1 Antibody directed against parasite proteins appeared in the blood in all mouse strains tested soon after the first week of infection and rose steadily for 5 to 12 weeks. 2 Qualitative individual variation within a given strain was commonly observed in the response to the various antigens. Each mouse strain synthesized IgG directed against a somewhat different spectrum of parasite proteins. Homologies in antigen recognition by pooled sera of five mice ranged from 54% to 79% from one mouse strain to another. Hybrid mice from a BALB/c X CBA cross (F1 generation) recognized essentially all antigens recognized by the two parents. Proteins of L. major with apparent molecular weights of 19 kD, 60 kD, 65 kD, 70 kD and greater than 100 kD were immunogenic in all strains of mice tested.     

Targeting caspases in intracellular protozoan infections

Caspases are cysteine aspartases acting either as initiators (caspases 8, 9, and 10) or executioners (caspases 3, 6, and 7) to induce programmed cell death by apoptosis. Parasite infections by certain intracellular protozoans increase host cell life span by targeting caspase activation. Conversely, caspase activation, followed by apoptosis of lymphocytes and other cells, prevents effective immune responses to chronic parasite infection. Here we discuss how pharmacological inhibition of caspases might affect the immunity to protozoan infections, by either blocking or delaying apoptosis.     

REVIEWS

Over a wide range of conditions fine fuel re-accumulation after fire in eucalypt forests is well described by equations of the form X_t = X_ss (l-e^?kt)

where X_t is the weight (t ha^?1) of litter accumulated at time t(yr), X_ss is the weight of accumulated litter under steady-state conditions, and k is a decomposition rate constant (yr^?1). Decomposition constants ranged from 0.11 to 0.31 yr^?1, and steady- state litter accumulations varied between 11.1 and 29.4 t ha^?1.

In many types of eucalypt forest, litter re-accumulates to dangerous (from a fire control point of view) weights in 3–6 years, thus severely limiting the period during which prescribed burning provides protection from wildfire. The rapid rate of litter re-accumulation is mostly due to a marked decrease in the total amount of litter decomposing (relative to rates of litter input), rather than to any fire-induced reduction in the rate of decomposition. The implications of these findings for fire management in eucalypt forests are briefly discussed.

More quantitative information on the relationships between fuel mass (and other fuel characteristics) and fire behaviour under high to very high fire danger conditions is required to enable better evaluation of the effectiveness of low intensity prescribed burning for fire control. The ecological impacts of prescribed burning regimes, which also need to be considered when devising burning programs, are briefly discussed.     

Congenital Chagas disease: time to screen pregnant women?

Evaluation of: Bua J, Volta BJ, Velazquez EB et al. Vertical transmission of Trypanosoma cruzi infection: quantification of parasite burden in mothers and their children by parasite DNA amplification. Trans. R. Soc. Trop. Med. Hyg. 106(10), 623–628 (2012).

The congenital transmission of Trypanosoma cruzi has gained epidemiological importance because it is partially responsible for the spread of Chagas disease worldwide. The feasibility of a cure when infected children are treated early makes the detection of congenital infection a valuable goal toward the control of the disease. Here, the authors review and discuss the findings of Bua et al., who quantified the parasitemia of infected women and their newborns by quantitative PCR. The authors demonstrate that the maternal parasite burden is directly related to the risk of neonatal infection. This study points out the importance of a quantitative screen for T. cruzi in pregnant women who live in, or have traveled to, endemic areas for improving the diagnosis of infected newborns and providing prompt treatment.     

Inorganic arsenite inhibits IgE receptor‐mediated degranulation of mast cells

Millions of people worldwide are exposed to arsenic (As), a toxicant which increases the risk of various cancers, cardiovascular disease and several other health problems. Arsenic is a potent endocrine disruptor, including of the estrogen receptor. It was recently shown that environmental estrogen‐receptor disruptors can affect the signaling of mast cells, which are important players in parasite defense, asthma and allergy. Antigen (Ag) or allergen crosslinking of IgE‐bound receptors on mast cells leads to signaling, culminating in degranulation, the release of histamine and other mediators. Because As is an endocrine disruptor and because endocrine disruptors have been found to affect degranulation, here we have tested whether sodium arsenite affects degranulation. Using the rat basophilic leukemia (RBL) mast cell model, we have measured degranulation in a fluorescence assay. Arsenic alone had no effect on basal levels of degranulation. However, As strongly inhibited Ag‐stimulated degranulation at environmentally relevant concentrations, in a manner that is very dependent on concentrations of both As and Ag. The concentrations of As effective at inhibiting degranulation were not cytotoxic. This inhibition may be a mechanism underlying the traditional Chinese medicinal use of As to treat asthma. These data indicate that As may inhibit the ability of humans to fight off parasitic disease. Copyright © 2010 John Wiley & Sons, Ltd.     

青海省湟源县人体肠道寄生虫分布调查报告

湟源县为我省海东地区管辖的农业县之一，是青海省农、牧区之间的过渡地段。该县属高原大陆性气候，日照强，多风干燥，地势复杂，是青藏公路沿线的重镇。按全国人体寄生虫分布调查实施细则的要求，确定日月，大华两乡各１个调查点。共检查１０３９人，查见寄生虫感染者４２９例，人群的寄生虫总感染率为４１．３％。日月点和大华点人群寄生虫感染率（感染者）分别为４５．４％（２３５／５１８）和３７．０％（１９３／５２１）。共查见寄生虫９种，各种寄生虫感染率分别为：蛔虫２９％（３０１例），蛲虫（１２岁以下儿童）３８．７％（９１例），结肠内阿米巴８．１％（８４例），微小内蜒阿米巴４．３％（４５例），布氏嗜碘阿米巴２．２％（２３例），哈氏内阿米巴０．９％（９例），溶组织内阿米巴０．５％（５例），贾第虫１．７％（１８例），人芽囊原虫１．４％（１４例）。两个点的调查结果表明，在不同性别、年龄和职业寄生虫感染率间的差别，均具有显著意义（其χ２值依次为８．３８７６、２８．６０２８和３２．４８，其Ｐ值均＜０．０５）。