BALB/c and C57Bl/6 mice infected with virulentBurkholderia pseudomalleiprovide contrasting animal models for the acute and chronic forms of human melioidosis

Burkholderia pseudomalleiis the aetiological agent of melioidosis, a life-threatening bacterial disease occurring in many species of animals, including man. Infection in humans commonly manifests as one of three clinical presentations: acute, subacute or chronic disease. Investigations were undertaken to assess the suitability of BALB/c and C57Bl/6 mice as animal models for the different forms of human melioidosis. The course of infection in BALB/c mice was similar to that which occurs in acute human infection. By contrast, infection of C57Bl/6 mice appeared to mimic chronic human melioidosis. While BALB/c mice suffered a rapidly-progressive bacteraemia which resulted in host death by 96 h, C57Bl/6 mice were able to prevent this, and typically remained asymptomatic for up to 6 weeks. LD₅₀values of 4 cells and 2.5×10⁴cells for BALB/c and C57Bl/6 mice, respectively, reflect these observations. The heightened level of resistance toB. pseudomalleiobserved in C57Bl/6 mice was suggested to have a genetic basis, when the susceptibilities of first filial and reciprocal backcross generations were examined. Growth kinetics ofB. pseudomalleiwithin BALB/c and C57Bl/6 peritoneal exudate cell (PEC) cultures were examined to investigate PEC microbicidal efficiency as a determinant of host susceptibility. C57Bl/6 PEC cultures exhibited greater microbicidal efficiency towardsB. pseudomalleiwhen compared to BALB/c cells, indicating that susceptibility may be determined by non-specific, cellular mechanisms. Collectively, these results suggest that the BALB/c and C57Bl/6 strains of mice may provide excellent models for acute and chronic human melioidosis, respectively.     

Morphofunctional characteristic of the immune system in BALB/c and C57BL/6 mice

Inbred animals serve as an adequate model to study the role of genetic factors in adaptive, disadaptive, and pathological processes. Morphofunctional study of the immune system was performed on intact BALB/c and C57Bl/6 mice. The structural and functional parameters of the immune system in BALB/c and C57Bl/6 mice differ under physiological conditions. In BALB/c mice, volume density of T zone in the spleen and production of IL-2, IL-3, IL-4, IL-10, and TNF-α were much higher than in C57Bl/6 mice. However, IL-12 production in BALB/c mice was lower than in C57Bl/6 mice. C57Bl/6 mice were characterized by higher cytostatic activity of splenic NK cells. The observed interstrain differences are genetically determined and contribute to the type of adaptive processes and different sensitivity of these mice to pathogenic agents.     

Spontaneous expression of endogenous type C RNA virus by BALB/c splenic B lymphocytes in continuous culture.

B-lymphocyte cultures were established from spleens of BALB/c, C57B1/6, NIH Swiss, and SWR mice of various age groups. Spontaneous, consistent, and thus predictable release of a B-tropic mouse endogenous virus occurred from the very first passage in cultured lymphocytes derived from BALB/c mice 6 months old or older but not from similar lymphocytes derived from BALB/c mice of 1.5 or 3 months of age. C57Bl/6, NIH Swiss, and SWR mice belonging to various age groups ranging between 1.5 and 18 months failed to exhibit such a spontaneous release of viral particles. We conclude that in BALB/c splenic B lymphocytes a breakdown of cellular control mechanisms occurs in older animals leading to viral production while such a phenomenon is absent in C57Bl/6, NIH Swiss, and SWR mice.     

Effect of dioxydine and cyclophosphane on lipid peroxidation and superoxide dismutase and catalase activities in C57Bl/6 and BALB/c mice

Twenty-four hours after intraperitoneal injection of cyclophosphane (40 mg/kg) and dioxydine (300 mg/kg) to C57Bl/6 mice, liver catalase activity dropped by 29 and 23%, respectively. In BALB/c mice, dioxydine (but not cyclophosphane) reduced catalase activity by 24%. Superoxide dismutase activity was lowered by cyclophosphane (but not dioxydine) in BALB/c mice, and by both dioxydine and cyclophosphane in C57Bl/6 mice (by 24 and 86%, respectively). The level of 2-thiobarbituric acid (TBA)-reactive lipid peroxidation (LPO) products in the liver of BALB/c mice treated with cyclophosphane and dioxydine increased 1.4- and 2.1-fold, respectively, while in C57Bl/6 mice it did not differ from the control. The initial rate ofin vitro-induced LPO in BALB/c mice receiving cyclophosphane and dioxydine increased 1.5- and 4-fold, respectively. In C57Bl/6 mice both cyclophosphane and dioxydine inhibited the accumulation of TBA-reactive LPO products. On the whole, animals of the C57Bl/6 strain are more resistant to the LPO-inducing action of mutagens than BALB/c mice, despite the fact that the latter are characterized by a higher activity of antioxidant enzymes. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 121, No. 5, pp. 528–532, May, 1996     

Differences in migration inhibitory factor production by C57Bl/6 and BALB/c mice in allergic and irritant contact dermatitis

Two strains of mice, BALB/c and C57Bl/6, which are known to differ in their inflammatory responsiveness to allergens, were analyzed regarding their expression of macrophage migration inhibitory factor (MIF). Allergic contact dermatitis to 2,4-dinitro-1-fluorobenzene and irritant contact dermatitis to croton oil were studied immunohistologically at designated time intervals after elicitation. BALB/c mice presented a significantly more intense ear swelling response than C57Bl/6 mice and showed a strong endothelial MIF expression in the early phase of inflammation in both allergic and irritant contact dermatitis. Endothelial MIF expression was much weaker in C57Bl/6 mice. Furthermore, the infiltration rate of inflammatory cells (MIF+ and BM8+ macrophages, Lyt2+ and L3T4+ T cells) was significantly higher in BALB/c than in C57Bl/6 mice. We conclude that genetically determined differences of susceptibility to allergens and irritants in BALB/c and C57Bl/6 mice are reflected by the intensity of MIF expression in the microvascular endothelium and immigrating inflammatory cells. MIF seems to appear as first molecular equivalent of developing inflammation and probably determines the degree of cellular infiltration.     

Morphofunctional changes of BALB/c and C57BL/6 mice's immune system under chronic bacterial gram-negative endotoxicosis

Chronic endotoxicosis was modeled by subcutaneous injection of the sepharose in complex with LPS. In these conditions we have studied morphofunctional changes of the immune system of BALB/c and C57Bl/6 mice, which are characterized by the different types of the immune response (Th2 type is predominant in BALB/c, Th1--in C57Bl/6). In the 1st-7th day t in the serum of BALB/c mice the endotoxin level increased in 21.3 times, in C57Bl/6--in 20.6 times. The endotoxin antibodies significantly decreased in 1th-7th days, on the 14th day it increased in the serum of both mice's strains. Morphofunctional changes of the immune system after chronic endotoxicosis were different in BALB/c and C57BI/6 mice. On the 1th day after injection of LPS and sepharose, in the thymus of C57Bl/6 mice the cortex layer was exhausted because of cell death, in the thymus of BALB/c mice II-III stages of accidental involution were developed. On the 7-14th day after injection of LPS and sepharose in the spleen of C57Bl/6 mice T- and B-zones were hyperplastic, however in spleen of BALB/c mice only T-zone were enlarged. After LPS and sepharose injection changes of cytokine production synthesized by KonA activated splenic cells were found out. In both strains the level of proinflammatory cytokines--TNFalpha and IL-1beta decreased, as well the Th1-cytokine IL-2. The production o fTh2-cytokine - IL-4, significantly decreased only in C57BI/6 mice. We suggest that damaging effect of LPS injection is determined by predominant Th2 or Th2 types of the immune response.     

The mTPH2 C1473G single nucleotide polymorphism is not responsible for behavioural differences between mouse strains

Tryptophan hydroxylase 2 (TPH2) is the rate limiting enzyme of serotonin synthesis in the brain. A recently described functional (C1473G) single nucleotide polymorphism in mouse TPH2 resulting in vitro in a strongly decreased enzymatic activity was suspected to be responsible for the observed differences in 5-HT levels and behaviour between mice strains. We bred two substrains of C57BL/6 mice carrying the two isoforms and could show that both exhibit equal TPH activity, brain 5-HT content and behaviour. These data indicate that the distinct behavioural characteristics of mouse strains are not due to differences in TPH2 activity, but to other variations in the genetic background.     

Morphofunctional Characteristic of Mast Cells in BALB/c and C57Bl/6 Mice during Cold Exposure

Mast cells of the mesentery and subcutaneous tissue in BALB/c and C57Bl/6 mice were studied after single and repeated cold exposure (-20 degrees C, 3 min). Immediate adaptive reactions of mast cells in BALB/c and C57Bl/6 mice did not differ after single cold exposure and were manifested in increased degranulation. Repeated cold exposure of BALB/c mice was followed by an adaptive reaction, which included an increase in the count of mast cells in subcutaneous tissue and normalization of the degranulation index. In C57Bl/6 mice the count of mast cells in subcutaneous tissue decreased, while the degranulation index remained high. These changes reflect the disadaptive response of mast cells to repeated cold exposure.     

Quantitative and qualitative differences in bronchoalveolar inflammatory cells in Pseudomonas aeruginosa-resistant and -susceptible mice

The difference in severity of Pseudomonas aeruginosa-induced chronic lung infection may be determined by differences in host inflammatory responses. In the present study we investigate this possibility using BALB/c and C57Bl/6 mice, resistant and susceptible, respectively, to chronic lung infection with P. aeruginosa. Following intratracheal inoculation of P. aeruginosa-impregnated agar beads, C57Bl/6 mice mounted a stronger inflammatory response with significantly higher total cell numbers in the bronchoalveolar lavage fluid compared with BALB/c mice. While polymorphonuclear leucocytes were the predominant cell in C57Bl/6 mice, macrophages constituted the majority in BALB/c mice at day 7 post-infection. Alveolar macrophages from C57Bl/6 mice showed significantly higher spontaneous production of nitric oxide (NO) at day 7 post-infection compared with BALB/c mice. Following in vitro stimulation with heat-killed Pseudomonas antigen, these cells produced significantly higher NO compared with cells from BALB/c mice at day 21 post-infection. Production of tumour necrosis factor-alpha (TNF-α) by alveolar macrophages was significantly higher at day 7 in BALB/c mice compared with C57Bl/6 mice, which showed significantly higher levels at day 28 post-infection. Taken together, these results suggest that defects in the host inflammatory process contribute to the variable outcome of chronic lung infection with P. aeruginosa. An exaggerated inflammatory response dominated by polymorphonuclear cells correlates with susceptibility to infection, whilst a modest inflammatory response dominated by macrophages correlates with resistance. Moreover, the quantity and timing of production of NO and TNF-α by alveolar macrophages may modulate the course and outcome of infection.     

Morphofunctional characteristic of mast cells in BALB/c and C57Bl/6 mice during cold exposure

Mast cells of the mesentery and subcutaneous tissue in BALB/c and C57Bl/6 mice were studied after single and repeated cold exposure (−20°C, 3 min). Immediate adaptive reactions of mast cells in BALB/c and C57Bl/6 mice did not differ after single cold exposure and were manifested in increased degranulation. Repeated cold exposure of BALB/c mice was followed by an adaptive reaction, which included an increase in the count of mast cells in subcutaneous tissue and normalization of the degranulation index. In C57Bl/6 mice the count of mast cells in subcutaneous tissue decreased, while the degranulation index remained high. These changes reflect the disadaptive response of mast cells to repeated cold exposure. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 8, pp. 207–209, August, 2004     

Serotonin receptor 1A −1019C/G variant: Impact on antidepressant pharmacoresponse in melancholic depression?

Previous studies on the effects of serotonin receptor 1A (5-HT1A) gene variation on treatment response in depression revealed inconsistent results with studies pointing towards a detrimental influence of the 5-HT1A −1019G allele on antidepressant treatment response, while others did not discern any involvement of 5-HT1A variants. In order to further delineate the impact of 5-HT1A gene variation on pharmacoresponse in depression over 6 weeks of antidepressant treatment, the influence of the 5-HT1A −1019C/G (rs6295) polymorphism was investigated in 340 Caucasian patients with a Major Depressive Episode (DSM-IV) with particular attention to the subtype of depression (major depression and melancholic depression). Antidepressant treatment response across 5-HT1A −1019C/G genotype groups showed no differences in either Major Depressive Episode or major depression between genotype groups, whereas stratification for the melancholic subtype of depression revealed a significantly worse treatment response as conferred by the −1019CC genotype (p = 0.02). The poorer treatment response in melancholic depression could first be detected in week 2 (p = 0.03), continuing until week 6 and showing a maximum effect in week 3 (p = 0.01). The present study adds to the clarification of the role of 5-HT1A variation in treatment response in major depression by providing preliminary support for poor treatment response mediated by the 5-HT1A −1019C allele repressing 5-HT1A activity specifically in the melancholic subtype of depression.     

Effect of cyclophosphamide treatment on the course of Mycobacterium lepraemurium infection and development of delayed-type hypersensitivity reactions in C57B1 and BALB/c mice.

Pre-treatment of Mycobacterium lepraemurium susceptible, BALB/c, and resistant, C57Bl, mice with cyclophosphamide markedly altered the development of delayed hypersensitivity during footpad infections with this organism. A tuberculin-type response demonstrated by untreated C57Bl mice was significantly intensified after week 3 in cyclophosphamide-pre-treated mice although this response had returned to normal levels by week 8. A Jones-Mote-type response demonstrated throughout experiments by untreated BALB/c mice was considerably increased in magnitude by week 3 in cyclophosphamide-pre-treated mice. By week 6 this response had become considerably protracted and was of the tuberculin-type. By week 8 however this response had started to diminish and by week 12 cyclophosphamide-treated and untreated BALB/c mice produced similar Jones-Mote-type responses when skin-tested. Cyclophosphamide pre-treatment had no effect on the growth of M. lepraemurium in C57Bl mice over 12 weeks. In BALB/c mice however cyclophosphamide-pre-treated mice demonstrated considerable resistance to infection at weeks 8 and 10 after infection but not thereafter. Whereas the magnitude of the delayed hypersensitivity response in C57Bl mice could not be correlated with resistance such a relationship could be demonstrated in BALB/c mice.     

Endothelial cells and renal epithelial cells do not express the Wegener''s autoantigen, proteinase 3.

In vitro and in vivo T cell responses were determined during the course of bronchopulmonary infection with mucoid Pseudomonas aeruginosa. T cell responses were compared in two inbred mouse strains, namely BALB/c mice, which are resistant to the establishment of chronic bronchopulmonary Ps. aeruginosa infection, and C57Bl/6 mice, which have high numbers of bacteria in the lungs through 14 days post-infection. Unseparated lung cells and lung T cells from BALB/c mice exhibited significantly higher in vitro proliferative responses to both heat-killed Ps. aeruginosa and concanavalin A (Con A) than cells from C57Bl/6 mice through 20 days post-intratracheal infection with 10(4) colony-forming units (CFU) Ps. aeruginosa. Proliferation of unseparated lung cells but not lung T cells from BALB/c mice infected 6 days previously with 10(5) CFU Ps. aeruginosa was suppressed in response to Con A; these cells were unresponsive to specific antigen. Suppression of lymphocyte proliferation in the lungs of C57Bl/6 mice infected with 10(4) CFU Ps. aeruginosa and in BALB/c mice infected with 10(5) CFU was found to be mediated by adherent lung cells via the production of nitric oxide and prostaglandins. Determination of in vivo T cell-mediated responses in infected mice demonstrated that resistant BALB/c mice had high DTH and low Pseudomonas-specific antibody responses, while C57Bl/6 mice had low DTH and high antibody levels, in particular, IgG2b and IgM.     

V and C Gene Contribution in Creating Anti-α-1,3 Dextran Antibodies in Mice

The light (L) and heavy (H) chain and the antigenic, idiotypic (Id) composition of the antibody (Ab) plaque-forming cells (PFC) and serum Ab specific for alpha-1,3 dextran have been characterized in Ig-lal BALB/c prototype mice, in Ig-la- [30] mice, and in BALB/c congenic and recombinant strains. Four distinct Ab Id specificities were identified by using criteria of Id relatedness to three Id-distinct, alpha-1,3 dextran-binding BALB/c myeloma proteins (MP), all associated, in the Ig-lal mice with the lambda (lambda) chains: a major, common IdX in 40--90% of the molecules; three minor, individual IdI in 1--49% of the molecules; and a fifth, Id-undefined one. These specificities were expressed at the PFC and serum level in the mu and gamma isotypes. A minor, kappa (kappa), Id-negative Ab was discerned only at the PFC level. The Ig-la- CBA and C3H mice responded with anti-alpha-1,3 dextran, kappa Id-negative Ab. The BALB/c, congenic strain CB20 (BALB/c Ig-lb, carrying the C57Bl/Ka, Ig-lb variable H (VH) gene complement and CH phenotype, made anti-alpha-1,3 dextran kappaId-negative Ab of the Ig-lb prototype. The recombinant BAB/14, carrying in the C57Bl/Ka CH-Ig-lb phenotype the BALB/c Ig-lal VH gene(s) controlling anti-alpha-1,3 dextran lambda Ab responsiveness and Id specificity (VH-DEX+), express the BALB/c lambdaId repertoire.     

Macrophages and protective immunity in Mycobacterium lepraemurium infections in a ''resistant'' (C57Bl) and a ''susceptible'' (BALB/c) mouse strain

The progressive low resistance form of M. lepraemurium infection in BALB/c mice and the more benign form of infection in C57Bl mice provided appropriate models for analysing the role of macrophages in the spectrum of leprosy in man. Although C57Bl mice were more resistant to both primary and challenge infections than BALB/c mice, peritoneal macrophages from infected mice of both strains were bacteriostatic in vitro. However, a diffusion chamber technique demonstrated that macrophages of BALB/c mice were usually less effective in controlling mycobacterial multiplication in vivo than those of C57Bl mice. This technique also revealed two diffusible factors in infected mice of both strains: one able to activate, the other able to suppress macrophage anti-mycobacterial activity. In C57Bl mice, the macrophage activating factor was apparently dominant; in BALB/c mice, the macrophage suppressor factor seemed to play the major role.     

Experimental African trypanosomiasis: differences in cytokine and nitric oxide production by macrophages from resistant and susceptible mice.

Immunosuppression in experimental infections with Trypanosoma congolense is mediated by the synergistic action of macrophages and a novel lymphocyte(s), which involves the activity of IFN-gamma as well as IL-10. BALB/c mice are highly susceptible while C57Bl/6 mice are relatively resistant to T. congolense infections. Plasma and/or supernatants of spleen cell cultures of infected susceptible BALB/c mice have more IL-10 but less IL-12 than those of infected relatively resistant C57Bl/6 mice. Cells of a BALB/c macrophage cell line, when pulsed with T. congolense, produce more IL-10 and IL-6, but have less TNF-alpha mRNA, than equally treated cells of a C57Bl/6 cell line. Peritoneal and/or bone marrow-derived macrophages obtained from BALB/c mice, pulsed with T. congolense in culture, produce less nitric oxide, TNF-alpha and IL-12, but more IL-6 and IL-10 than equally treated macrophages isolated from C57Bl/6 mice. We suggest that genetic resistance to African trypanosomiasis is expressed at the level of the macrophage.     

Anti-Inulin [β-(2→1)-Linked Polyfructose] and Anti-Grass Levan [β-(2→6)-Linked Polyfructose] Antibody Response in Mice

Anti-inulin [β-(2 → 1) polyfructosan Brucella abortus (InuBA)] and anti-grass levan [β-(2 → 6) polyfructosan] antibody responses in BALB/c and C57BL mice and in their F₁ and backcross progeny, as well as in immunoglobulin congenic and Bailey recombinant inbred strains derived from BALB/c and C57BL mice, were examined. The anti-inulin antibodies could accommodate both β-(2 → 1)- and β-(2 → 6)-linked polyfructosans, and 97% of the anti-inulin plaque-forming cells (PFC) from BALB/c mice expressed the cross-reactive idiotypes (InuIdX) shared by the BALB/c inulin- and levan-binding myeloma proteins. Of the C57BL mice, only 25% produced high anti-inulin response, and none exhibited the InuIdX of BALB/c anti-inulin antibodies. The percentages of InuIdX⁺ anti-inulin PFC were also examined in other strains with high anti-inulin response. In C58 and AL mice, 80% of anti-inulin PFC were InuIdX⁺, whereas in A/He and RIII mice, only 40% were InuIdX⁺. All strains examined developed high anti-grass levan response, and the antibodies were specific for β-(2 → 6) structures and did not exhibit InuIdX. Comparison of the magnitude of the anti-inulin antibody titers in response to InuBA in BALB/c, C57BL, and their F₁ and backcross progeny, as well as in immunoglobulin congenic (i.e., B.C-8, BAB-14, and C.B-20) and recombinant inbred strains derived from BALB/c and C57BL mice, showed that all mice having the IgCH^a(BALB/c) allotype gave high anti-inulin response. In addition to the InuIdX structural genes, the effects of allotype-linked or unlinked “regulatory” genes were also indicated by the lower anti-inulin response in B.C-8 and BAB-14 mice compared with BALB/c mice and the higher anti-inulin response in C.B-20 mice compared with C57BL mice. A multigene interaction in controlling the production of the anti-inulin antibodies was implicated.     

Benzodiazepine Reception in C57Bl/6 and BALB/c Mice Depending on the Type of Stress Factor

Specific binding of ³Н-fl unitrazepam with synaptosomal membranes after exposure to open field test and “contact with predator” test was measured in C57Bl/6 and BALB/c mice. Stress-induced decrease in benzodiazepine binding after open field test was observed only in BALB/c mice and after contact with predator in both animal strains.