Antibacterial immunity of lower airways: local or localized?

Clearance of bacteria in the bronchoalveolar lavage, the level and functional activity of IgA and changes in the cellular composition of BAL were examined in mice after supralaryngeal immunization and subsequent challenge with Klebsiella pneumoniae. More than 60% of the bacterial inoculum was removed by nonspecific mechanisms within 90 min after inoculation; within the time interval 1.5-3.5 h, clearance was significantly accelerated in locally immunized mice. The enhancement of clearance effectiveness is specific and increases proportionally with the length of immunization (1 less than 2 less than 4 weeks); it is of short duration and towards the end of the 3rd week after immunization, in 73% of immunized animals, the clearance values did not differ from values found in controls. The local immunization did not influence the total level of IgA in BAL, the formation of specific IgA antibody was minimal, in vivo binding of IgA to klebsiella could not be demonstrated. In immunized mice, a significant increase in the numbers of PMN and lymphocytes, as well as an increased activity of phagocytic cell (PMN, MP) was found in BAL. The time interval of 1.5-3.5 h after challenge bounds the space for mechanisms, activated by local immunization in lower airways. The actual participation of individual factors in the accelerated elimination of bacteria from the lumen of airways, remains unclear so far.     

The Effects of Bacterial Endotoxin on the Infection of Mice with Trypanosoma cruzi*

Mice (Rockland strain) infected with Trypanosoma cruzi strain Tulahuén were treated with Escherichia coli endotoxin before, simultaneously with, and after inoculation of the parasites. The peak parasitemias of endotoxin-treated mice were higher than those of nontreated infected animals, regardless of the time of endotoxin administration. Peak parasitemias occurred at the same time in infected nontreated mice as in animals given endotoxin before or simultaneously with the trypanosomes. If endotoxin was administered 24 hr after the infection, a delay in the peak parasitemia was noted. Changes in the survival time were not observed unless endotoxin was given 24 hr postinfection. Infected mice had an increasing susceptibility to the lethal effect of endotoxin. The LD₅₀ of endotoxin decreased from 675 μg for normal mice to 230, 92, and 18 μg for infected animals 1, 3, and 8 days after the infection, respectively. In the infected mice, the endotoxin-detoxifying ability of the spleen was found to be impaired.     

Activation of trehalase by heat shock in yeast ascospores: Correlation with total cellular cyclic-AMP content

An animal model resembling the human disease caused byCampylobacter jejuni has been developed. Characteristic illness followed intragastric challenge of neonatal mice with strains ofC. jejuni enhanced for virulence by serial intraperitoneal passage in weanling mice of organisms suspended in either mucin or iron dextran. Such passage lowered the LD₅₀ in weanlings from 2×10¹¹ colony-forming units (CFU) to 2×10⁵ CFU per mouse. Neonatal mice chellenged by intragastric intubation with 2×10⁹ CFU of the virulence-enhanced organisms suspended in mucin or iron dextran showed signs of infection by day 5, including severe diarrhea, increased musus discharge occasionally with blood, and reduced weight gain. Diarrhea contionued for eight days, after which most animals recovered. This mouse infection model provides a means for assessing the determinants of virulence among strains ofC. jejuni.     

Occurrence of atypical lymphocytes following intravenous injection of Candida albicans in mice

The occurrence of atypical lymphocytes has been observed in the course of experimental acute infection withCandida albicans in mice. In animals injected intravenously with 2.5 × 10⁶ ofCandida albicans cells, an increased number of monocytes was seen in 24 hours. Monocytes showed toxic vacuolisation in most instances in protoplasm and sometimes in the nuclei. Only a few atypical lymphocytes could be seen at that time. In the following days the number of monocytes diminished and the number of atypical lymphocytes increased. After four days atypical lymphocytes constituted frequently over 20 % of white cells. The autopsy of sacrificed or dead animals with the presence of such elevated percentages of atypical lymphocytes showed enlargement of cervical lymphnodes in all animals. In mice infected with 1.4 × 10³ ofCandida albicans cells, no level higher than 12% of atypical lymphocytes was seen. Pictures were returning to normal with only a few atypical lymphocytes present among the animals which survived for two months after infection withCandida albicans.This work was supported partially byDora Kaplan, Joan Sloan, Cathy Cooper. Memorial Funds and the Roon Foundation.     

Blastogenic responsiveness of spleen cells fromLegionella pneumophila-infected mice immunosuppressed with cyclophosphamide

Although guinea pigs are highly susceptible to experimental infection withLegionella pneumophila, mice are considered resistant. In the present study it was found that, although untreated mice resisted lethal infection with up to 10⁷ L. pneumophila, mice treated with three divided doses of cyclophosphamide became 10–100 times more susceptible. Injection of mice with 150 mg cyclophosphamide/kg body weight 96 and 48h prior to and on the same day as intraperitoneal challenge with graded dose ofL. pneumophila resulted in markedly increased lethality. Approximately half of the mice pretreated with cyclophosphamide succumbed to 10⁶ legionellae within 4–10 days after infection, and all treated animals given 10⁷ bacteria died. Legionellae were readily recovered from spleen, lymph nodes, and liver of surviving mice 4–10 days after infection, but not thereafter. Sensitization of mice with Legionella antigen was evident by the lymphocyte blastogenic test in vitro, by use of spleen cells at various times after infection. Mice given graded doses ofL. pneumophila evinced enhanced responsiveness to either formalin-killed whole cell vaccine, cell-free sonicate, or purified outer membrane antigen when tested in vitro on days 3 and 5. Peak responses generally occurred 20–35 days after infection. Mice given none or one dose of cyclophosphamide and injected with legionellae showed enhanced responses on day 5 of culture in vitro, a time when spleen cells from control nonsensitized animals showed much lower responses. Surviving mice given three doses of cyclophosphamide had lower blastogenic responses, generally as low as that occurring with spleen cells from nonsensitized animals. Thus suppression of immune responses of mice by cyclophosphamide substantially increased susceptibility toL. pneumophila and depressed blastogenic responsiveness.     

Lipopolysaccharide-induced resistance in mice against ascending urinary tract infection withklebsiella pneumoniœ

Protective effect of the lipopolysaccharide (LPS) antigen ofKlebsiella pneumoniœ was tested against ascending-mode urinary tract infection in BALB/c and LACA strains of mice. LPS was given by two different routes; LPS was found to be protective (whatever the application route) since colonization with the challenge organism was significantly lower in both cases as compared with unimmunized mice. A maximum decrease in bacterial count in the kidney of LPS-treated animals was observed on challenge after a 4-d treatment.     

Humoral immunity induced in the lower respiratory tract by local immunization with a temperature-sensitive mutant ofPseudomonas aeruginosa

The nature of the humoral immune mechanisms involved in the protection induced after local immunization with a temperature-sensitive (ts) mutant ofPseudomonas aeruginosa was investigated. We had previously shown that intranasal (i.n.) immunization of granulocytopenic mice protected the animals from lethal pulmonary challenge withP. aeruginosa, whereas mice immunized intraperitoneally were unprotected. Intranasal immunization induced high levels of anti-P. aeruginosa IgG and IgA in the lower respiratory tract, whereas only modest levels of IgG (and no IgA) could be detected in lung lavage fluids from mice immunized by the intraperitoneal (i.p.) route with ts mutant E/9/9. Plasma anti-P. aeruginosa IgG levels after i.n. immunization were lower than those observed after i.p. immunization with similar doses of the ts mutant. The main contribution to the protection induced when mice are immunized intranasally appears to be from IgA in the pulmonary secretions, although other immune mechanisms cannot be discounted.     

Toxoplasma gondii: The effects of infection at different stages of pregnancy on the offspring of mice

Congenital toxoplasmosis can cause fetal damage in humans and domestic animals. This study was focused on the effects of Toxoplasma gondii (Prugniaud strain) infection at different stages of pregnancy on the offspring of mice. Results showed that newborn mice from all infected groups were significantly lower in weight than those from the control group but significant difference was not found among these groups at day 60 after birth. The survival rate of the offspring from the group of mice infected at the earlier stage of pregnancy was significantly lower than those of infected and control groups. The positive offspring (with cysts found in their brain tissues) born from the mice infected at the earlier and intermediate stages of pregnancy showed a shorter latency and greater number of errors in the step-through passive avoidance test than those born from the mice infected at the late stage of pregnancy, the control group and the negative offspring from the infected groups. The number of cysts in the brain tissue was significantly higher in the offspring born from the groups of mice infected at the earlier and intermediate stages of pregnancy than those from the group of mice infected at the late stage of pregnancy. In addition, our results indicated that a high congenital transmission rate (90%) occurred in this NIH mouse model. In conclusion, the earlier and intermediate maternal infection of T. gondii can result in severe congenital toxoplasmosis, exhibiting conditions such as stillbirth or non-viability, and learning or memory capability damage in this mouse model. These results not only provide useful data for better understanding the effects of T. gondii infection on the offspring of mice infected at different stages of pregnancy but also for better consideration of the effect of this infection on other mammalian hosts including humans.     

The production of oxygen metabolites and their possible regulatory role in the course of tularemia infection

The changes of oxidative metabolism were studied in the course of a primary infection of mice with attenuated strain ofFrancisella tularensis. Metabolic stimulation of peritoneal cells is associated with a significant increase in spontaneous tetrazolium derivative reduction, the production of superoxide anion and hydrogen peroxide on day 5 after the immunization. The enhancement of superoxide dismutase precedes the increase in superoxide anion secretion. The splenic cells of immunized mice obtained on day 3 andin vitro pulsed by tularemic antigen secreted lymphokins(s) that could induce a metabolic stimulation. The treatment of resting splenic cells with hydrogen peroxide induces the secretion of interferon activity. The changes of oxidative metabolism that appear early after the infection seem to be related to a sequential activation of cells and probably have a regulatory role in the induction of immune defence againstF. tularensis.     

PrimaryListeria monocytogenes infection in gestating mice

The facultative intracellular Gram-positive bacteriumListeria monocytogenes is a food-borne pathogen of frequently underestimated importance. Pregnant women represent the high-risk group forL. monocytogenes infection. Abortion, stillbirth or neonatal infection can be the serious outcome of such an infection. Recovery from listeriosis, resistance mechanisms of the host and the effect ofL. monocytogenes on fetal development still remain to be fully understood. The results of our experiments showed an increased susceptibility of gestating BALB/c mice to primaryL. monocytogenes infection. The duration of listeriosis in gestating animals was almost twice longer than in the control group. Furthermore, it was clearly shown that the detrimental effect ofL. monocytogenes on fetal development was more pronounced if the infection was acquired earlier during gestation.     

Echinococcus granulosus:An Intraperitoneal Diffusion Chamber Model of Secondary Infection in Mice

Breijo, M., Spinelli, P., Sim, R.B., and Ferreira, A. M. 1998.Echinococcus granulosus:An intraperitoneal diffusion chamber model of secondary infection in mice.Experimental Parasitology90, 270–276. The present work describes a new experimental model of secondary infection which allows, through the recovery of the parasite together with its localin vivoenvironment, examination of the local nonadaptive immune response of the infected host and the differentiation of the parasite from protoscoleces to cysts. In this model we administered protoscoleces within silicone diffusion chambers, previously implanted into the peritoneal cavities of mice. The process of designing the model involved, first, determination of the optimal time postimplantation to infect the mice and, second, evaluation of the parasite's ability to establish infection within the chambers. The optimal time for infection was considered to be after the inflammation caused by implantation of the chambers had subsided. Our results showed that by day 20 postsurgery, three parameters used as indications of inflammation (complement C3, serum amyloid P protein, and polymorphonuclear cells in the peritoneum and in the chamber contents) had reverted to their normal levels. In our study of parasite differentiation, we found that 2–3% of the total number of parasites inoculated into the chambers were recovered as viable cysts after 100 days. Throughout the infection period, the population of parasites recovered was heterogeneous; certain parasite morphologies that have not been described previously were observed. In conclusion, the use of intraperitoneal diffusion chambers offers a potential tool for investigating thein vivodifferentiation process of secondary cysts ofEchinococcus granulosusin mice and the early local interactions between host and parasite during this process.     

牛种布鲁氏菌2308不同途径小鼠感染模型的建立与评估

[背景] 布鲁氏菌可经口、皮肤、黏膜和呼吸道感染人和动物。小鼠是布鲁氏菌研究中最常用的模型动物。[目的] 建立牛种布鲁氏菌2308不同途径和剂量感染BALB/c小鼠的模型,为布鲁氏菌小鼠感染试验提供参考。[方法] 用10¹-10⁵ CFU这5个不同感染剂量,分别经注射、口服和点眼方式感染BALB/c小鼠。在感染后不同时间点采集小鼠血清,检测IgG、IgM、IgA抗体含量、脾脏重量及脾脏含菌量,评价布鲁氏菌经不同途径感染BALB/c小鼠的效果。[结果] 10 CFU是注射感染BALB/c小鼠的最小感染剂量;10⁵ CFU是口服感染BALB/c小鼠的最小感染剂量。10¹-10⁵ CFU这5个不同感染剂量经点眼途径均未能成功感染BALB/c小鼠。在10⁵ CFU感染剂量下,口服与注射感染组小鼠每克脾脏平均含菌量分别为10^5.673 CFU/g和10^5.009 CFU/g,无显著差异（P>0.05）,但口服感染组小鼠脾脏平均重量为0.310 g,显著高于注射感染组0.165 g （P<0.01）。在试验期内,注射感染组和口服感染组小鼠体内IgG抗体的滴度均随感染时间延长而持续升高;整体上,口服感染组IgG抗体峰值显著高于注射感染组;2组IgM抗体变化趋势一致;口服感染组有2只小鼠在感染28 d后产生IgA抗体,注射感染组均未检测到IgA抗体。[结论] 建立了牛种布鲁氏菌2308通过不同途径感染BALB/c小鼠的模型。     

Functional analysis of T lymphocyte subsets in antiviral host defense

The role of different T cell subsets in antiviral host defense was investigated by treating thymectomized C57BL/6 and CBA/J mice with monoclonal rat anti-Lyt-2 or anti-L3/T4 IgG 2b antibodies 14 and 10 days before infection. This treatment depleted the respective T cell subsets to undetectable levels in peripheral blood when assayed by immunofluorescence. In mice treated with anti-Lyt-2, induction of cytotoxic T cells was reduced to less than 1 to 2% after intravenous infection with Armstrong strain of lymphocytic choriomeningitis virus (LCMV). In addition, no primary swelling of the footpad could be detected following local inoculation of the virus. In animals treated with anti-L3/T4, antiviral cytotoxic T lymphocyte responses were reduced by a factor of 10. These L3/T4+ cell-depleted mice showed delayed footpad swelling after local injection of LCMV Armstrong. After intracerebral infection with LCMV, anti-Lyt-2-treated mice were resistant and those injected with anti-L3/T4 were totally susceptible to LCMV Armstrong-triggered immunopathologic disease. Virus could be detected in the blood of antibody-treated mice 7 days after inoculation; however, no virus could be measured in the blood of surviving anti-Lyt-2-treated animals 15 days after intracerebral infection. Serum titers of interferon-alpha,beta induced by viral infection remained unaffected by depletion of T cell subsets. Anti-L3/T4 antibody-treated C57BL/6 mice failed to generate IgG antibodies against the New Jersey strain of vesicular stomatitis virus, whereas Lyt-2+ cell-depleted mice had normal antivesicular stomatitis virus (New Jersey strain) IgG antibody titers.     

Bacterial infection modulated by glucan: A search for the host defense potentiation mechanisms

Interactions between bacteria and the host were studied from day 0 up to day 10 post-challenge in mice pretreated with soluble glucan (20 mg/kg i.p.) and challenged supralaryngeally with a virulent strain ofKlebsiella pneumoniae. In the initial phase of infection, clearance of bacteria in the airways of glucan-treated mice was improved to an extent comparable with the vaccinated group but, in contrast to the immunized animals, subsequent regrowth of the bacterial inoculum was not prevented. The efficacy of defense, based during the entire course of infection mainly upon phagocytosis by neutrophils, markedly increased at intervals corresponding to the onset of humoral immune response. No evidence was obtained to indicate an enhanced involvement of alveolar macrophages in the phagocytosis of bacteria in glucan-stimulated mice. The results further support the notion that improvement of specific immune responsiveness rather than activation of nonspecific effector functions might be the most important expression of the host-defense-potentiating capacity of glucan and related stimulants of microbial origin.     

Adoptive transfer of dendritic cells modulates immunogenesis and tolerogenesis in a neonatal model of murine cutaneous leishmaniasis

We evaluated the adoptive transfer of DCs on Leishmania (L.) mexicana-infected neonatal BALB/c mice. DCs were isolated and purified from the spleens of the following donor groups: a) Adult BALB/c mice infected during adulthood with L. (L) mexicana; b) Adult BALB/c mice infected during neonatal life; c) Healthy neonatal BALB/c mice; d) Healthy adult BALB/c mice. A neonatal model of infection, generated after inoculation with 5 × 10⁵ promastigotes of L. (L) mexicana, was used as the infection control group. Sixteen hours after intraperitoneal transfer of DCs (1 × 10³, 1 × 10⁵, or 1 × 10⁶ cells/ml), neonatal recipient BALB/c mice were infected. The adoptive transfer of DCs diminished disease progression in neonatal mice. This reduction depends on the quantity and provenance of transferred DCs, since the effect was more evident with high numbers of DCs from adult mice infected during adulthood and healthy neonatal mice. Protection was significantly reduced in animals receiving DCs from healthy adult mice but it was absent in mice receiving DCs from adult mice infected during neonatal life. These results suggest that genetic susceptibility to Leishmania infection can be modified during neonatal life, and that the period of life when antigens are encountered is crucial in influencing the capacity of DCs to induce resistance or tolerance.     

Treatment of systemic candidiasis in a neutropenic murine model using immunoglobulin G bearing liposomal amphotericin B

Efficacy of immunoglobulin G (IgG) bearing liposomal amphotericin B (LAMB-IgG), liposomal amphotericin B without IgG (LAMB) or free amphotericin B (fAMB/Fungizone) was investigated in the treatment of systemic candidiasis in a neutropenic mouse model. Treatment with a single dose (0.6 or 0.9 mg amphotericin B per kg body weight) of LAMB-IgG resulted in a significant increase in the survival rate of neutropenic mice infected with 3×10⁵ cfu ofCandida albicans compared to untreated controls, mice injected with IgG, or liposome alone. Survival was also better in neutropenic mice treated with LAMB-IgG than in neutropenic mice treated with the same dose of LAMB or fAMB. Moreover, 65% of all mice survived the infection after treatment with a single dose of 0.6 mg AMB of the LAMB-IgG formulation. Quantitative culture counts of organs showed that both fAMB and LABM-IgG formulations even at a dose of 0.3 mg AMB/kg, clearedC. albicans from the spleens, livers, and lungs but not from the kidneys. However, a decreasd number ofC. albicans cells was recovered from the kidneys of mice that survived the infection. Results of the study suggest that LAMB-IgG is more effective than LAMB or fAMB in the therapy of disseminated candidiasis in neutropenic mice.     

Role of interferon in homologous and heterologous rotavirus infection in the intestines and extraintestinal organs of suckling mice

Recent studies demonstrated that viremia and extraintestinal rotavirus infection are common in acutely infected humans and animals, while systemic diseases appear to be rare. Intraperitoneal infection of newborn mice with rhesus rotavirus (RRV) results in biliary atresia (BA), and this condition is influenced by the host interferon response. We studied orally inoculated 5-day-old suckling mice that were deficient in interferon (IFN) signaling to evaluate the role of interferon on the outcome of local and systemic infection after enteric inoculation. We found that systemic replication of RRV, but not murine rotavirus strain EC, was greatly enhanced in IFN-α/β and IFN-γ receptor double-knockout (KO) or STAT1 KO mice but not in mice deficient in B- or T-cell immunity. The enhanced replication of RRV was associated with a lethal hepatitis, pancreatitis, and BA, while no systemic disease was observed in strain EC-infected interferon-deficient mice. In IFN-α/β receptor KO mice the extraintestinal infection and systemic disease were only moderately increased, while RRV infection was not augmented and systemic disease was not present in IFN-γ receptor KO mice. The increase of systemic infection in IFN-deficient mice was also observed during simian strain SA11 infection but not following bovine NCDV, porcine OSU, or murine strain EW infection. Our data indicate that the requirements for the interferon system to inhibit intestinal and extraintestinal viral replication in suckling mice vary among different heterologous and homologous rotavirus strains, and this variation is associated with lethal systemic disease.     

Influence of sodium selenite on203Hg absorption,distribution, and elimination in male mice exposed to methyl203Hg

To study the effects of long-term selenium supplementation on absorption, distribution, and elimination of methylmercury (MeHg) in mice, three groups of male mice (Balb/c CA) were exposed for 7 wk to 0, 0.6, and 3 ppm sodium selenite in tap water. They were then given a single oral dose of Me²⁰³Hg (2 μmol/kg) by gastric intubation, and elimination of²⁰³Hg was followed by whole-body counting for 49 d at the same Se exposure as previously. Twenty-four hours and 49 d after dosage, 6–7 animals/group were sampled for analysis of²⁰³Hg distribution in the body. Glutathione peroxidase (GSH-PX) activity in blood and selenium levels in the liver were used as measures of selenium status. Gastrointestinal absorption of Me²⁰³Hg was not influenced by the Se status of the animals. Selenium supplementation of MeHg-exposed mice caused an enhanced whole-body elimination of Hg, but selenium-supplemented animals did not have lower Hg levels in the brain and kidney than nonsupplemented animals. The effect of selenium on the accumulation, of Hg in the brain was dose-dependent, a high dose (3 ppm Se) causing a higher initial accumulation of Hg. The intracellular distribution of²⁰³Hg in the liver and kidney was not affected by Se. The results indicate that selenium treatment of MeHg-exposed mice may have a positive effection the health of the animals by decreasing the total body burden of MeHg.     

Production of stress-inducible form of heat-shock protein 70 in mouse peritoneal adherent cells afterin Vivo infection byFrancisella tularensis

Heat-shock proteins (hsp) are ubiquitously produced molecules which participate in the protection of cells from environmental perturbation. Moreover, the members of the heat-shock protein 60 (hsp60) and 70 (hsp70) families play an important role in pathogen-host interactions. We studiedin vivo production of the 70-kDa heat-shock proteins in the extract of peritoneal exudate cells (PEC) from mice injected intraperitoneally with an attenuated vaccine strain (LVS) ofFrancisella tularensis. We found a differential production of a highly stress-inducible member of the hsp70 family, designated hsp72, in three inbred strains of mice exhibiting either resistance or susceptibility toF. tularensis LVS infection. Whereas in tularemia-resistant mice hsp72 was even expressed in PEC without injection of bacteria and its production further increased on day 3 and slowly declined on days 5 and 7 after injection, in susceptible mice hsp72 production was highly inducble and restricted only to day 3 afterin vivo infection. Further analysis of hsp72 expression revealed intracellular hsp72 accumulation and its preferential production by peritoneal adherent cells.     

Microscopic analysis of the effect ofRhizobium leguminosarum biovartrifolii host specific nodulation genes in the infection of white clovers

Summary A microscopic assessment is presented of the comparative infection capacity of wild-type and hybrid strains ofRhizobium leguminosarum bv.viciae withR. l. bv.trifolii strain ANU 843 on white clover seedlings. TheR. l. bv.viciae hybrid strains contained defined DNA segments coding for different combinations ofR. l. bv.trifolii host-specific nodulation genes. White clover plants were examined over a 72 h period to assessRhizobium infectivity, the morphological changes in root hair growth; colonisation ability of rhizobia; infection thread initiation and the ability to induce cortical cell division.R. l. bv.viciae strain 300 induced root hair curling more slowly than strain ANU 843 or any of the hybrid strain 300 bacteria, and when curling had taken place, there was poorer colonization by strain 300 within the folded hair cell, no evidence of infection thread formation and only limited cortical cell division 72 h after inoculation. The addition of the host-specific nodulation genes ofR. l. bv.trifolii to strain 300 was necessary to induce infection threads and establish a normal pattern of nodulation of the roots of white clovers.