Immune responses to filarial infection in laboratory mice

Models of filarial infection in laboratory inbred mice are valuable tools for assessing the relevance of anti-filarial immune responses in protection against these parasites. However, laboratory mice are not permissive for those filarial species which are known to infect humans. Therefore, immunity to the different stages of these filariae, i.e. infective third stage larvae (L3), adults and microfilariae, has been analyzed separately, as a surrogate approach. Although much information has been gathered by analysis of immunity and intervention in particular immune responses in these experimental systems, interference of different stage-specific responses as well as modulation of filarial maturation by the immune system cannot be assessed. A newly established infection model of filariasis, namely infection of laboratory mice with Lito-mosoides sigmodontis, accommodates the full developmental cycle of the parasite and may overcome this deficiency. Although the disadvantage of this latter model is that it deals with a filaria which is not pathogenic to man, it is the only model in which immunity can be analyzed during maturation of infective larvae into adult worms, the period considered most important for vaccination studies. Received: 23 December 1996     

Eosinophilia and intracranial worm recovery in interleukin-5 transgenic and interleukin-5 receptor α chain-knockout mice infected with Angiostrongylus cantonensis

We infected interleukin-5 (IL-5)-transgenic (IL-5-Tg) and IL-5 receptor α knockout (IL-5Rα^−/−) mice with Angiostrongylus cantonensis to determine the possible roles of IL-5 and eosinophils in A. cantonensis infection in mice. IL-5-Tg mice demonstrated significantly higher eosinophilia in bone marrow, blood and cerebrospinal fluid (CSF), lower intracranial worm recovery and smaller female worms than naive C3H/HeN mice. Both IL-5-Tg and C3H/HeN mice evoked antigen-specific serum and CSF IgA antibody responses as early as days 5 and 7 postinfection, respectively. Prominent eosinophil infiltration was noted around intracranial worms in the subarachnoid spaces of the mouse brains; eosinophils adhering to the worm surface were degranulated. In contrast, IL-5Rα^−/− mice yielded a higher worm recovery than wild-type or heterozygous mice at day 20 postinfection and failed to provoke CSF eosinophilia. These findings indicate that A. cantonensis infection in the mouse causes IL-5 production and subsequent CSF eosinophilia, the latter probably being involved in the killing of intracranial worms. Received: 20 December 1996 / Accepted: 15 January 1997     

Interleukin-5 transgenic mice show augmented resistance to Angiostrongylus costaricensis infection

To determine the possible role of eosinophils in Angiostrongylus costaricensis infection, both interleukin-5 (IL-5) transgenic (Tg) and non-transgenic (non-Tg) C3H/HeN mice were infected with A. costaricensis third-stage larvae. IL-5 Tg mice demonstrated greater resistance than non-Tg mice to A. costaricensis, as shown by lower adult worm recovery, smaller adults, fewer eggs in the intestinal wall and fewer larvae passed in the feces. Both mice showed similar antigen-specific IgA and IgGI antibody responses, although IgA was more prominent than IgG1. Egg deposition and inflammatory responses in the intestinal walls were milder in IL-5 Tg mice than in non-Tg mice. The eggs with developed larvae, deposited in the intestinal walls of IL-5 Tg mice, were surrounded by numerous degranulating eosinophils and sometimes with Splendore-Hoeppli deposits. The data suggest that eosinophils are involved in the resistance of the mouse during primary infection with A. costaricensis.     

alpha4 integrin-dependent eotaxin induction of bronchial hyperresponsiveness and eosinophil migration in interleukin-5 transgenic mice

We investigated the roles of eosinophil infiltration and activation induced by the eosinophil-selective chemokine eotaxin, and of the expression of eosinophil alpha4 and beta2 integrins in causing bronchial hyperresponsiveness (BHR) in interleukin (IL)-5 CBA/Ca transgenic mice. These mice did not show BHR, despite the presence of some eosinophils in the lungs. Intratracheal mouse recombinant eotaxin (3 micrograms) did not induce BHR in wild-type mice. In IL-5 transgenic mice, eotaxin (3 and 5 micrograms) increased responsiveness at 24 h and increased eosinophils in bronchoalveolar lavage (BAL) fluid by 9.4- and 14-fold by 24 h, respectively, together with augmentation of eosinophil peroxidase activity and eosinophil infiltration in the airway submucosa. Using flow cytometry, the expression of alpha4, CD11b, and CD18 was upregulated in BAL, but not in blood, eosinophils. A rat anti-alpha4 antibody inhibited eotaxin-induced BHR and eosinophil migration and activation, but an anti-CD11b antibody had no significant effects on BHR. A combination of both antibodies was more effective. IL-5 and eotaxin synergize in the induction of BHR and airway eosinophilia, effects that are dependent on the induction of eosinophil alpha4 integrin. Expression of BHR depends on the recruitment and activation of eosinophils.     

Effect of recombinant interleukin-5, interleukin-3, and eotaxin on apoptosis in eosinophilic granulocytes

We studied in vitro effects of recombinant interleukin-5, interleukin-3, and eotaxin on programmed death of eosinophils from healthy donors and patients with non-Hodgkin’s lymphomas associated with severe blood eosinophilia. Interleukin-5 and eotaxin produced the most potent antiapoptotic effect on eosinophils from healthy donors. In patients with non-Hodgkin’s lymphomas, spontaneous apoptosis in eosinophilic leukocytes was low and remained unchanged during incubation with recombinant proteins. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 4, pp. 370–373, April, 2007     

Increased cardiac weight in interleukin-6 transgenic mice with viral infection accompanies impaired expression of natriuretic peptide genes

Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) regulate cardiac hypertrophy. We investigated ventricular alterations of ANP and BNP in interleukin-6 (IL-6) transgenic mice (TG) and wild type (WT) mice with or without viral infection. The ANP and BNP mRNA/GAPDH mRNA ratios in the ventricles of IL-6 TG mice were twice that of WT mice, but were not increased significantly by viral inoculation. In WT mice, both ANP and BNP responses were significantly increased in the ventricles of mice 10 days after encephalomyocarditis (EMC) viral inoculation. Cardiac weight in IL-6 TG mice was significantly greater than in WT 10 days after viral inoculation. Left ventricular wall thickness and the diameter of ventricular myocytes also were greater in IL-6 TG than WT after viral infection. Primary cultures of neonatal rat cardiac myocyte showed that IL-6 increased ANP and BNP mRNA expression in a dose-responsive fashion. In summary, overexpression of ANP and BNP occurs in the ventricles of IL-6 TG mice, along with increased cardiac weight after infection with EMC virus, and impaired responses in the expression of ANP and BNP.     

The role of interleukin-5 in protective immunity to Strongyloides venezuelensis infection in mice.

We depleted or neutralized interleukin-5 (IL-5) and IL-5 receptor of C57BL/6 mice, using rat anti-murine IL-5 monoclonal antibody (NC17) and anti-murine IL-5 receptor monoclonal antibody (H7). Mice treated with these monoclonal antibodies were infected with Strongyloides venezuelensis larvae. The time-course of faecal egg output and peripheral eosinophilia were monitored. In a primary infection, anti-IL-5 treatment did not affect faecal egg output, although the eosinophil count in peripheral blood was markedly reduced. There was no difference in intestinal worm burden or faecal egg output between anti-IL-5 treated and non-treated mice. In a secondary infection, worms were expelled from the small intestine of anti-IL-5-treated mice as well as from non-treated mice. Worm recovery from the lungs of mice treated with either anti-IL-5 or anti-IL-5 receptor monoclonal antibody was the same as that of normal controls. However, a marked reduction in worm recovery was observed in re-infected mice that had not been treated with monoclonal antibodies. Treatment with anti-IL-5 or anti-IL-5 receptor monoclonal antibody suppressed blood and tissue eosinophilia. Thus the results suggested that the host's protective immunity against tissue-migrating larvae was IL-5-dependent but intestinal immunity was not.     

Pulmonary eosinophilia in mice devoid of interleukin-5

The biology of the eosinophilic leukocyte-development, recruitment, and prolonged existence in somatic tissues-has been linked almost invariably to the actions of the "eosinophil" cytokine, interleukin-5 (IL-5). Here we demonstrate that pulmonary eosinophilia can occur in the absence of IL-5, as morphologically normal eosinophils are recruited to the lungs of virus-infected IL-5 -/- mice with kinetics and sequelae that are indistinguishable from those of their IL-5 +/+ counterparts. We conclude that pulmonary eosinophilia observed in response to primary paramyxovirus infection occurs via mechanisms that are distinct from those involved in eosinophil responses to allergens and in asthma. Furthermore, the presence of functional eosinophils in IL-5 -/- mice suggests the possibility of developmentally distinct subsets of what has been presumed to be a homogeneous leukocyte population.     

Effects of the deregulated expression of human interleukin-2 in transgenic mice

We constructed transgenic mice that carry the cDNA of human interleukin-2 (IL-2) under the control of the H-2Kd promoter. The IL-2 transgenic mice expressed human IL-2 mRNA in the thymus, spleen, bone marrow, lung, muscle and skin. Human IL-2 protein was also detected in their sera. The IL-2 transgenic mice suffered from alopecia and pneumonia, but no typical autoimmune reactions seemed to be involved in these lesions. In the epidermis of the IL-2 transgenic mice there was an increase in Thy-1+ dendritic epidermal cells (DEC), which might be involved in the skin lesion. Immune responses of their spleen cells against antigens were significantly impaired whereas their spleen cells responded well to polyclonal lymphocyte activators.     

Lymphoid hyperplasia in transgenic mice over-expressing a secreted form of the human interleukin-1beta gene product

To evaluate the biological effects of over-expression of interleukin-1beta (IL-1beta) on the immune system we have generated transgenic mice, expressing the IL-1beta gene fused to a heterologous signal sequence under the control of the mouse immunoglobulin enhancer (Emu). A prominent hyperplasia and a disturbed microarchitecture of lymphoid tissues were observed in the transgenic mice. The CD4+ T cells in the hyperplastic lymphoid organs seemed to invade the majority of the lymphoid organs including B-cell restricted areas. Analysis of lymph node cells revealed an increased frequency of CD4+ CD44high CD62L- T cells and local secretion of IL-2 and IL-4, compatible with an elevated number of activated T cells. Furthermore, significant levels of human IL-1beta in sera and high concentrations of serum immunoglobulin G (IgG) were observed in the transgenic mice. The data suggest a role for IL-1beta in controlling lymphoid microarchitecture and, when over-expressed, breaking the threshold in T-helper-B-cell interaction.     

Overexpression of suppressor of cytokine signalling-5 augments eosinophilic airway inflammation in mice

BACKGROUND: Enhanced expression of the suppressor of cytokine signalling (SOCS)-5 might be of therapeutic benefit for T-helper type 2 (Th2) dominant diseases, as its expression is reported to result in a reduction of Th2 differentiation in vitro due to the inhibition of IL-4 signalling. OBJECTIVE: To investigate the regulatory role of SOCS-5 in vivo, we explored the phenotype of an experimental asthma model developed in SOCS-5 transgenic (Tg) mice. METHODS: The SOCS-5 Tg mice or wild-type (WT) mice were sensitized and repeatedly challenged with ovalbumin (OVA). We examined bronchoalveolar lavage fluid (BALF), lung specimens, and airway hyperresponsiveness (AHR) to methacholine. RESULTS: The production of IFN-gamma by CD4(+) T cells from unprimed SOCS-5 Tg mice was significantly increased in comparison with unprimed wild-type mice, indicating that SOCS-5 Tg mice have a Th1-polarizing condition under natural conditions. However, in an asthma model, significantly more eosinophils in the airways and higher levels of IL-5 and IL-13 in BALF were observed in the SOCS-5 Tg than the wild-type mice. AHR in the asthma model of SOCS-5 Tg was also more enhanced than that of wild-type mice. OVA-stimulated CD4(+) T cells from the primed SOCS-5 Tg mice produced significantly more IL-5 and IL-13 than CD4(+) T cells from wild-type mice. CONCLUSION: Our results demonstrate that the overexpression of SOCS-5 does not inhibit Th2 response, but rather augments the phenotype of the asthma model in vivo. This finding throws into question the therapeutic utility of using enhancement of SOCS-5 expression for Th2-dominant disease.     

NK T cells are a source of early interleukin-4 following infection with third-stage larvae of the filarial nematode Brugia pahangi

Infection of C57BL/6 mice with the third-stage larvae of Brugia pahangi results in a rapid expansion of NK1.1(+) T cells in the spleen and draining lymph nodes. NK T cells produced interleukin-4 in the spleen within 24 h of infection, and these cells were CD4(-).     

Inflammation induced by infection potentiates tau pathological features in transgenic mice

Comorbidities that promote the progression of Alzheimer's disease (AD) remain to be uncovered and evaluated in animal models. Because elderly individuals are vulnerable to viral and bacterial infections, these microbial agents may be considered important comorbidities that could potentiate an already existing and tenuous inflammatory condition in the brain, accelerating cognitive decline, particularly if the cellular and molecular mechanisms can be defined. Researchers have recently demonstrated that triggering inflammation in the brain exacerbates tau pathological characteristics in animal models. Herein, we explore whether inflammation induced via viral infection, compared with inflammation induced via bacterial lipopolysaccharide, modulates AD-like pathological features in the 3xTg-AD mouse model and provide evidence to support the hypothesis that infectious agents may act as a comorbidity for AD. Our study shows that infection-induced acute or chronic inflammation significantly exacerbates tau pathological characteristics, with chronic inflammation leading to impairments in spatial memory. Tau phosphorylation was increased via a glycogen synthase kinase-3β-dependent mechanism, and there was a prominent shift of tau from the detergent-soluble to the detergent-insoluble fraction. During chronic inflammation, we found that inhibiting glycogen synthase kinase-3β activity with lithium reduced tau phosphorylation and the accumulation of insoluble tau and reversed memory impairments. Taken together, infectious agents that trigger central nervous system inflammation may serve as a comorbidity for AD, leading to cognitive impairments by a mechanism that involves exacerbation of tau pathological characteristics.     

Susceptibility of HLA-B27 transgenic mice to Yersinia enterocolitica infection

The majority of patients with reactive arthritis have the major histocompatibility complex class I gene HLA-B27. The development of arthritis in these patients often occurs following infection with one of several enteric bacteria, including Yersinia enterocolitica. In this study, transgenic mice expressing HLA-B27 and their negative full sibs were infected intravenously with Yersinia enterocolitica 0:8 WA in an attempt to develop an experimental model of reactive arthritis. To date, no reactive arthritis has been observed; however, a significantly higher incidence of paralysis was observed in the HLA-B27⁺ transgenic mice. Injection of 10⁵ organisms induced hind limb paralysis in 8 out of 30 of the HLA-B27 transgenic mice (27%) and in only 1 of the 24 negative siblings (4%). Paralysis occurred in 14 out of 30 HLA-B27⁺ mice (47%) at a dose of 10⁴ organisms. Only 2 of the 25 negative siblings (8%) were affected at this dose. Paraspinal abscesses were found in all of the paralyzed animals. At the 10⁴ dose most of the HLA-B27⁺ mice (70%) succumbled to the disease within 4 weeks, while the mortality in their B27⁻ full sibs was less than 10%. Thus, HLA-B27 transgenic mice have higher mortality and morbidity from infection with Y. enterocolitica 0:8 WA than corresponding HLA-B27⁻ littermates.     

Transmission of filarial infection through blood transfusion

Microfilariae can be transmitted by blood transfusion and they may be circulated in the recipient's blood but they do not develop into adult worms. Mortality associated with transfusion associated filarial infection is not documented but it may give rise to morbidity in transfusion recipients in terms of allergic reaction. The present study was carried out to investigate the association of post transfusion reactions and filarial infections in an endemic area. About 11,752 transfusion recipients were followed up and in 15 months period, 47 (0.4%) post transfusion reactions (PTR) were reported. Routine investigations for post transfusion reaction were carried out in all 47 patients and their respective blood donor. Moreover, blood culture, microfilaria detection by concentration technique, filarial antibody and antigen detection (both by ELISA) were done in all subjects. Out of 47 patients showing post transfusion reaction, 29 (61.7%) patients developed allergic reaction. Eighteen (38.3%) patients having allergic reaction did not have previous history of blood transfusion and 14 (29.8%) of them received transfusion from blood donors who was either positive for microfilaria, filarial antigen or antibody. Microfilaremia was demonstrated in 4 (8.5%) patients and 5 (10.6%) blood donors. Microfilaria was concurrently present in 2 patients and their respective donors. Filarial antibody was detected in 27 (56.5%) patients and 26 (55.3%) blood donors but microfilaria was detected in 3 (6.4%) and 4 (8.5%) subjects, respectively. Antigen detection test correlated with microfileraemic state of subjects. The result shows that transfusion associated filarial infection may be a probable cause for transfusion-associated morbidity in endemic areas. In 14 (29.8%) patients having allergic reactions, the probable cause was transfusion-associated filarial infection. Filarial antigen detection test was found to be more useful in detecting infections. Blood donors with active history of filarial infection should be deferred from donating blood. Filarial antigen detection test may be employed as screening test for blood donors, if possible.     

M-CSF transgenic mice: role of M-CSF in infection and autoimmunity.

In this study, transgenic CD2F1 mouse lines (C-1.1-C-1.11) bearing a transgene encoding the murine growth factor M-CSF under the control of the liver specific alpha-1-antitrypsin gene promoter were generated. Transgenic C-1.4 mice showed elevated expression of transgene-encoded M-CSF in the liver and displayed a 2-3-fold increase of M-CSF plasma levels and of macrophage numbers in the liver as compared with non-transgenic littermates. M-CSF transgenic mice showed increased resistance against sublethal i.v. infections with Listeria monocytogenes as compared with infected non-transgenic mice. To investigate the influence of M-CSF in murine systemic lupus erythematosus (SLE), the M-CSF transgenic mouse line C-1.4 was bred into the genetic background of SLE-prone MRL+/+ mice. The resulting C-1.4/MRL transgenic mice bearing increased endogenous M-CSF levels showed consistently lower levels of anti-ss-DNA autoantibodies as compared with non-transgenic MRL+/+ mice. The life span of the C- 1.4/MRL transgenic mice and the severity of the disease in these mice remained unchanged as compared with their non-transgenic littermates. It is concluded that in addition to M-CSF further factors must be involved in the acceleration of the autoimmune disease in SLE prone MRL/lpr mice.     

Visceral Leishmania donovani infection in interleukin-13-/- mice

Leishmania donovani-infected interleukin-13-/- BALB/c mice showed impaired initial gamma interferon secretion and incomplete granuloma assembly at parasitized liver foci. Nonetheless, control of early parasite replication, resolution of liver infection, and responsiveness to antileishmanial chemotherapy were intact. By itself, interleukin-13 does not appear to materially influence acquired resistance in this intracellular infection.     

Accelerated control of visceral Leishmania donovani infection in interleukin-6-deficient mice

In patients with visceral leishmaniasis, increased levels of circulating interleukin-6 (IL-6) regularly accompany fully expressed, progressive infections (kala-azar). To experimentally test the role of IL-6, responses to an intracellular Leishmania donovani infection in the livers of IL-6(-/-) and wild-type mice were compared. IL-6(-/-) mice showed an enhanced control of the infection and earlier, rapid parasite killing along with additional evidence of a stimulated antileishmanial Th1-cell-type response: increased levels of circulating gamma interferon, accelerated granuloma assembly, and heightened responsiveness to chemotherapy. In this model of visceral leishmaniasis, IL-6 appears to act in a suppressive, macrophage-deactivating fashion, which identifies it as a potential target for therapeutic blockade.     

Regulation of primary Strongyloides ratti infections in mice: a role for interleukin-5.

C57BL/6 mice genetically deficient in interleukin-5 (IL-5-/-) and normal C57BL/6 (IL-5+/+) mice were infected with larvae of a homogonic strain of the nematode Strongyloides ratti. In primary infections both male and female IL-5-/- mice released two to four times more eggs and larvae than IL-5+/+ mice. IL-5-/- mice harboured about 60% more intestinal worms, which were more fecund, than IL-5+/+ mice. The duration of the infection was similar in normal and IL-5-deficient mice. Both IL-5-/- and IL-5+/+ mice resisted a secondary infection. IL5-/- mice lost more weight during the infection than normal mice and took longer to regain their initial weight after expelling the worms. The number of eosinophils increased in the bone marrow, peritoneal cavity and small intestine of IL-5+/+ mice, but not IL-5-/- mice, following infection. No significant differences between infected IL-5+/+ and IL-5-/- mice in mast cells or other leucocytes were observed in the peritoneal cavity. Thus, IL-5 functions to protect the host in a primary infection of S. ratti by limiting the number and fecundity of worms establishing in the small intestine. This protection is correlated with elevated blood and tissue eosinophilia which occurs in normal mice but not in IL-5-/- mice.