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Group B streptococci (GBS) have been recognised as an ever-growing cause of serious invasive infections in non-pregnant adults, in particular in association with severe underlying diseases such as diabetes mellitus. In the present study we used mice rendered diabetic to gain further insights into host-pathogen interaction during induced GBS sepsis and septic arthritis. Type I diabetes was induced in adult CD-1 mice by low-dose streptozotocin treatment. Mice were then infected with different doses of GBS, and mortality, appearance of arthritis, growth of microorganisms in the organs and cytokine and chemokine profile were assessed in diabetic and control animals. The LD50 was significantly lower in diabetics than in controls, while both incidence and severity of arthritis were higher. A significantly higher number of microorganisms were recovered from the organs of diabetic mice than in controls. The worsening of sepsis and arthritis was associated with a significant increase in systemic and local production of IL-6, IL-1 beta, TNF-alpha, IL-10, macrophage inflammatory protein 1 alpha (MIP-1alpha), and MIP-2 and with a decrease in IFN-gamma production. Taken together, our results indicate an impaired host resistance to GBS infection in diabetics, likely due to a dysregulation of the cytokine network and prolonged local inflammatory response.

Group BStreptococcus(GBS) is a major cause of pneumonia, bacteremia, and meningitis in neonates and has been found to persist inside host phagocytic cells. The pore-forming GBS β-hemolysin/cytolysin (βH/C) encoded bycylEis an important virulence factor as demonstrated in severalin vivomodels. Interestingly,cylEdeletion results not only in the loss of βH/C activity, but also in the loss of a carotenoid pigment of unknown function. In this study, we sought to define the mechanism(s) by whichcylEmay contribute to GBS phagocyte resistance and increased virulence potential. We found thatcylE-deficient GBS was more readily cleared from a mouse's bloodstream, human whole blood, and isolated macrophage and neutrophil cultures. Survival was linked to the ability of βH/C to induce cytolysis and apoptosis of the phagocytes. At a lower bacterial inoculum,cylEalso contributed to enhanced survival within phagocytes that was attributed to the ability of carotenoid to shield GBS from oxidative damage. In oxidant killing assays,cylEmutants were shown to be more susceptible to hydrogen peroxide, hypochlorite, superoxide, and singlet oxygen. Together, these data suggest a mechanism by which the linkedcylE-encoded phenotypes, βH/C (sword) and carotenoid (shield), act in partnership to thwart the immune phagocytic defenses.

Septic arthritis is a clinical manifestation of group B Streptococcus (GBS) infection in both neonates and adults. Because macrophages are known to participate in tissue injury, the role of this cell population in GBS-induced arthritis was investigated. Mice were rendered monocytopenic by administration of etoposide, a drug that selectively depletes the monocyte/macrophage population and then injected with GBS (1 x 10(7) colony-forming units per mouse). Appearance of arthritis, mortality, GBS growth in the organs, and local and systemic cytokine production were examined. Etoposide-treated mice had a significantly less severe arthritis than control animals. Histopathological analysis of the joints confirmed clinical observations. Decreased joint levels of the proinflammatory cytokines interleukin 1 (IL-1) beta and IL-6 accompanied the less severe development of arthritis in monocytopenic mice. In contrast, mortality was increased in the etoposide-treated mice compared with controls. Monocytopenic mice exhibited elevated bacterial load in the blood and kidneys at all time points examined. These results indicate that lack of macrophages leads to less severe joint lesions, but also results in impaired clearance of bacteria, and consequent enhancement of mortality rates.

The ability of different serotypes of group B streptococci (GBS) to induce septic arthritis in mice was compared. Types II, III, IV, V, VI and VII GBS were investigated. A highly capsulate strain of type III GBS, COH1, and its mutants, COH1-11 (lacking capsular sialic acid) and COH1-13 (non-capsulate), obtained by transposon insertional mutagenesis, were used to assess the role of type-specific polysaccharide on the induction of arthritis. At an intravenous dose of 10(7) cfu/mouse, reference strains of types II, III, IV, VI and VII and type III strain COH1 induced arthritis with an incidence ranging from 70 to 90%. For type V and strain COH1-11, 10(8) cfu/mouse was required to obtain a 50% incidence of arthritis; lesions were not evident with strain COH1-13. The presence of the capsule played a major role in the induction of GBS septic arthritis. The presence and amount of sialic acid in capsular polysaccharide influenced the incidence of articular lesions. The bacterial dose affected the manifestations of arthritis; the less virulent strains of GBS also induced articular lesions when an adequate number of micro-organisms reached the joints.

Group B streptococci have long been known as a leading cause of life-threatening infection in neonates, young infants and pregnant women, and recently have been recognized as an ever-growing cause of serious invasive infections in nonpregnant adults. B7-1 and B7-2 are two molecules with immunoregulatory functions implicated in the differentiation of T cells. The present study examined the role of B7-1 and B7-2 during group B streptococci-induced sepsis and arthritis. B7-1- or B7-2-deficient mice were infected with 1 × 10 7 streptococci, and mortality, appearance of arthritis, growth of microorganisms in the organs and cytokine profile were assessed. Lack of B7-1 was associated with amelioration of arthritis, while worsening of articular lesions was found in B7-2 deficient mice, in comparison to controls. Amelioration of arthritis in B7-1 deficient mice was accompanied by a lower local production of IL-1 β and IL-18, and increase in IL-4 and IL-10 secretion. On the contrary, B7-2 deficient mice showed an higher proinflammatory cytokine production and lower IL-10 secretion than controls. Taken together, our results provide evidence that signaling delivered by B7-1 and B7-2 plays a role in determining the outcome of group B streptococcal induced arthritis, likely due to the different local secretory pattern.

Group B streptococcus (GBS) has been recognized as an ever-growing cause of serious invasive infections in nonpregnant adults, in particular, in association with severe underlying diseases. The most common manifestations include primary bacteremia, urinary tract infections, pneumonia, meningitis, peritonitis, and osteoarticular infections. Toll-like receptor-2 (TLR2) mediates host responses to gram-positive bacteria. TLR2 function was investigated in murine GBS-induced sepsis and arthritis in wild-type (wt) and TLR2-deficient (TLR2−/−) mice. Mice were infected with different doses of GBS (107, 5 × 106, or 106CFU per mouse). Mortality, appearance of arthritis, GBS growth in the organs, and local and systemic cytokine and chemokine production were examined. TLR2−/−mice showed earlier and higher mortality rates and increased incidence and severity of arthritis than wt mice at all the infecting doses employed. Histopathological analysis of the joints confirmed clinical observations. TLR2−/−mice exhibited a higher microbial load in blood, kidneys, and joints than wt animals. In vitro experiments performed with peritoneal polymorphonuclear cells and macrophages showed a significantly lower bactericidal ability of cells from TLR2−/−mice. Increased systemic and local levels of interleukin-1β (IL-1β), IL-6, tumor necrosis factor alpha, macrophage inflammatory protein-1α (MIP-1α), and MIP-2 accompanied the more severe development of sepsis and arthritis in TLR2−/−mice. In conclusion, the lack of TLR2 was associated with an impaired host resistance to GBS infection, likely due to a diminished bacterial clearing and a consequent enhanced inflammatory response.

Corynebacterium diphtheriae is a well-known cause of localized respiratory tract infections. However, this micro-organism can also be associated with invasive infections, such as endocarditis, septic arthritis and osteomyelitis. Invasive infections are often caused by non-toxigenic strains. To set up an in vivo experimental model of C. diphtheriae infection, mice were infected intravenously with different doses (ranging from 1×107 to 5×108 bacteria per mouse) of three non-toxigenic strains, namely ISS-4749, ISS-4746 and ISS-3319. Similar mortality rates were observed with the three strains, with an LD50 ranging from 9×107 to 1·2×108. All strains were arthritogenic, although to different extents. ISS-4749 and ISS-4746 infection resulted in a maximum of 60 and 50 %, respectively, of animals with articular lesions, while in the ISS-3319-infected group only 25 % were positive. There were differences in systemic and joint cytokine production in the three experimental groups. ISS-4749- and ISS-4746-infected mice exhibited higher local levels of interleukin (IL)-6 and IL-1β than ISS-3319-infected animals. At systemic levels, ISS-3319 was able to induce early and sustained production of interferon-γ (IFN-γ), but not IL-6. Conversely, infection with the other strains resulted in high IL-6, but not IFN-γ, production. In conclusion, an experimental model of C. diphtheriae infection was set up, with development of septic arthritis. This model could be useful in studies on the pathogenicity and characterization of virulence factors other than toxin production.

Glucuronoxylomannan (GXM), the principal constituent of the Cryptococcus neoformans capsule, modulates the inflammatory response of human monocytes in vitro. Here we examine the efficacy of GXM as a novel anti-inflammatory compound for use against experimental septic arthritis. Arthritis was induced in mice by the intravenous injection of 8 × 10 6 CFU of type IV group B streptococcus (GBS). GXM was administered intravenously in different doses (50, 100, or 200 μg/mouse) 1 day before and 1 day after bacterial inoculation. GXM treatment markedly decreased the incidence and severity of articular lesions. Histological findings showed limited periarticular inflammation in the joints of GXM-treated mice, confirming the clinical observations. The amelioration of arthritis was associated with a significant reduction in the local production of interleukin-6 (IL-6), IL-1β, macrophage inflammatory protein 1α (MIP-1α), and MIP-2 and an increase in systemic IL-10 levels. Moreover, peritoneal macrophages derived from GXM-treated mice and stimulated in vitro with heat-inactivated GBS showed a similar pattern of cytokine production. The present study provides evidence for the modulation of the inflammatory response by GXM in vivo and suggests a potential therapeutic use for this compound in pathologies involving inflammatory processes.

The role of nitric oxide in group BStreptococcus(GBS) infection was evaluated by inhibiting its production with aminoguanidine (AG). AG-treated mice displayed higher mortality rates and more frequent and severe arthritis than controls. Worsening of arthritis correlated with a higher number of GBS cells in the joints and local interleukin-1β production.

Intravenous inoculation of CD-1 mice with 107CFU of type IV group BStreptococcus(GBS) results in a high incidence of diffuse septic arthritis,associated with high levels of systemic and local production of interleukin-1β (IL-1β) and IL-6. In this study, the role of the anti-inflammatory cytokine IL-10 in the evolution of GBS systemic infection and arthritis was evaluated. IL-10 production was evident in sera and joints of GBS-infected mice. Neutralization of endogenous IL-10 by administration of anti-IL-10 antibodies (1 mg/mouse) at the time of infection resulted in worsening of articular lesions and 60% mortality associated with early sustained production of IL-6, IL-1β, and tumor necrosis factor alpha (TNF-α). The effect of IL-10 supplementation was assessed by administering IL-10 (100, 200, or 400 ng/mouse) once a day for 5 days, starting 1 h after infection. Treatment with IL-10 had a beneficial effect on GBS arthritis, and there was a clear-cut dose dependence. The decrease in pathology was associated with a significant reduction in IL-6, IL-1β, and TNF-α production. Histological findings showed limited periarticular inflammation and a few-cell influx in the articular cavity of IL-10-treated mice, confirming clinical observations. In conclusion, this study provides further information concerning the role of IL-10 in regulating the immune response and inflammation and calls attention to the potential therapeutic use of IL-10 in GBS arthritis.

The susceptibilities of C3H/HeN, BALB/c, and C57BL/6N mouse strains to group B streptococci (GBS) infection were evaluated. C3H/HeN mice developed severe polyarthitis; mild lesions and no lesions were observed in BALB/c and C57BL/6N mice, respectively. A correlation between the severity of arthritis, the number of GBS in the joints, and local interleukin-6 and interleukin-1β production was evident.

Intravenous inoculation of CD1 mice with 10 7 CFU of type IV group B Streptococcus (GBS IV) results in a high incidence of diffuse septic arthritis. In this study the roles of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and IL-6 in articular pathology were evaluated. Cytokine levels were quantified in the serum and joints by enzyme-linked immunosorbent assay in mice injected with GBS IV and tested or not tested with pentoxifylline (PTF), a methylxanthine that affects cytokine production. PTF was administered intraperitoneally at a dose of 1 mg/mouse (50 mg/kg of body weight) 1 h after GBS infection and then at 24-h intervals for 4 days. High levels of IL-1β and IL-6, but not TNF-α, were detected in the joints of mice injected with GBS IV from 5 to 15 days after infection, when articular lesions were most frequent and severe. IL-1β and IL-6 concentrations in the joints significantly ( P < 0.001) exceeded those detected in the serum, confirming a strong local production. PTF treatment resulted in a strong reduction of cytokine production and in a marked decrease in both the incidence and severity of arthritis. Inoculation of exogenous murine recombinant IL-1β or IL-6 in mice treated with GBS IV plus PTF resulted in an incidence and severity of articular lesions similar to those obtained with inoculation of GBS IV alone. No significant effect was obtained with TNF-α administration. These data show a strong involvement of IL-1β and IL-6, but not TNF-α, in the pathogenesis of GBS arthritis.

We have previously shown that the most prominent feature of type IV group B Streptococcus (GBS) systemic infection in mice is a high incidence of diffuse septic arthritis1–3. In this study we investigated the ability of different GBS serotypes to induce arthritis in mice to evaluate the role of type-specific polysaccharide on the appearance of articular lesions. Furthermore, all GBS serotypes were assayed for virulence and growth of GBS in the blood, kidneys, and joints during infection.

There is ample evidence that protection against group B streptococcal (GBS) disease, both in experimental animals and in humans, is related to the presence of specific antibodies and complement. However, until now the possibility of increasing resistance to GBS infection by potentiating natural cell-mediated immunity in the host, has not been explored. In this study we examine the effect of administering in vivo MVE-2 (a polymer fraction of 1,2-co-polymer of divinyl ether and maleic anhydride) and inactivated Candida albicans (CA) cells on mouse resistance to the reference strain type Ia 090 GBS (GBS-090) lethal infection. MVE-2 and CA, respectively a synthetic and a microbial biological response modifier (BRM), are strong inducers and activators of natural resistance effectors, such as natural killer (NK) cells, macrophages and polymorphonuclear cells (PMN). The results showed that MVE-2 protected 100% CD-1 mice from a systemic lethal challenge with GBS-090 (5 x 10(3) microorganisms/mouse) when administered 3 days before infection at dose of 50 mg kg-1. CA treatment, in five doses (CA-5d) over 14 days protected 100% mice when administered at 2 x 10(7) cells/mouse and when the last CA injection was given 1 day before the GBS-090 challenge. Instead, when the GBS-090 challenge was performed by intraperitoneal route, protection was obtained with CA-5d treatment but not with MVE-2. The possibility that MVE-2 or CA stimulated a rapid production of specific antibodies against GBS-090 infection was excluded by the ELISA assay. Evidence exists that NK cells do not play a primary role as effectors in the MVE-2 and CA conferred protection since the strong reduction in NK activity, due to in vivo administration of anti-asialo GM1 antibodies before GBS-090 infection, did not influence the BRM-induced protection. Besides, high NK activity levels, induced by in vivo rhIL-2 administration, did not protect the mice against GBS-090 infection. Both studies on in vivo clearance and in vitro microbicidal activity, showed that, after 1 h, immunopotentiated effectors were unable to kill GBS-090, but were highly effective against GBS type VI. These results seem to indicate that intracellular GBS-090 killing is a slow process requiring more than 1 h. This study demonstrates that it is possible to increase resistance to GBS-090 lethal infection by BRMs, by potentiating the antibody-independent microbicidal activity of the phagocytes.

We have established an experimental murine model to gain insight into the pathogenicity and clinical features of type IV group B streptococcus (GBS) infections. Adult CD-1 mice were challenged intravenously with 10(7) type IV GBS cells, inducing systemic invasion. Most of the animals were able to clear the infection from the blood, brain, and lungs within 2 weeks and from the spleen and liver within 1 month. However, the animals were unable to clear the microorganism from the joints and kidneys during the 60-day observation period. About 80% of the mice challenged intravenously with type IV GBS manifested early septic arthritis, which evolved from an acute exudative synovitis to permanent lesions characterized by irreversible joint damage and ankylosis. Induction of persistent septic arthritis was dependent on the number and viability of microorganisms inoculated and was unrelated to the strain of type IV GBS and the growth phase of the inoculum. Type-specific antibodies of both immunoglobulin M and G classes could be detected by agglutination and enzyme-linked immunosorbent assay from days 7 and 14, respectively; immunoglobulin G antibodies persisted for more than 40 days. Complexes of antibodies and group- and type-specific antigens were detected in mouse sera 24 h after infection and persisted up to day 22. These results were obtained an experimental model of type IV GBS chronic infection with early development of septic arthritis, which could be useful in future studies of pathogenicity and immune mechanisms involved in the host resistance to this microorganism.

SUMMARY: Cell wall components from Candida albicans were compared to intact cells for their ability to induce natural cytotoxic immunoeffectors in the peritoneal cavity of mice. A soluble mannoprotein extract (MP) and an insoluble glucan fraction (GG) strongly stimulated the generation of peritoneal effectors capable of lysing YAC-1 and P-815 tumour cell lines in vitro. The anti-YAC-1 effectors were characterized as natural killer (NK) lymphocytes while the anti-P-815 effectors appeared to be activated macrophages. The activity of each fraction was typically dose-dependent and both fractions differed from whole cells in the kinetics of induction of cytotoxicity. However, the NK and macrophage effectors generated by these materials had similar functional and phenotypic properties, irrespective of the material used as inducer. No mannoprotein was detected in the insoluble glucan fraction GG. Hence, the immunoenhancing activity of GG could not be attributed to the presence of some MP or MP-like component. Mannan-rich fractions with low (