Mannan-binding lectin recognizes structures on ischaemic reperfused mouse kidneys and is implicated in tissue injury.

Organ damage as a consequence of ischaemia and reperfusion (I/R) is a major clinical problem in an acute renal failure and transplantation. Ligands on surfaces of endothelial cells that are exposed due to the ischaemia may be recognized by pattern recognition molecules such as mannan-binding lectin (MBL), inducing complement activation. We examined the contribution of the MBL complement pathway in a bilateral renal I/R model (45 min of ischaemia followed by 24 h of reperfusion), using transgenic mice deficient in MBL-A and MBL-C [MBL double knockout (MBL DKO)] and in wildtype (WT) mice. Kidney damages, which were evaluated by levels of blood urea nitrogen (BUN) and creatinine, showed that MBL DKO mice were significantly protected compared with WT mice. MBL DKO mice, reconstituted with recombinant human MBL, showed a dose-dependent severity of kidney injury increasing to a comparable level to WT mice. Acute tubular necrosis was evident in WT mice but not in MBL DKO mice after I/R, confirming renal damages in WT mice. MBL ligands in kidneys were observed to be present after I/R but not in sham-operated mice. C3a (desArg) levels in MBL DKO mice were decreased after I/R compared with that in WT mice, indicating less complement activation that was correlated with less C3 deposition in the kidneys of MBL DKO mice. Our data implicate a role of MBL in I/R-induced kidney injury.

Mannan-binding lectin modulates the response to HSV-2 infection.

Viruses have developed numerous strategies to escape recognition by the immune system. However, some viruses such as herpes simplex virus-2 (HSV-2) are recognized by initiators of the complement system, e.g. mannan-binding lectin (MBL). To study the effects of MBL deficiency during viral infection we have chosen a model of generalized HSV-2 infection. We infected MBL-A and MBL-C double knock-out mice (DKO) with HSV-2 via the intraperitoneal (i.p.) route. DKO mice cleared HSV-2 from the liver less efficiently than the comparable wild-type animals. The impairment to effectively neutralize HSV-2 correlated with compromised liver function as measured by increased plasma levels of alanine-amino transferase. No differences in the viral burden were found in other organs such as spleen or brain. Thus, MBL-mediated protection was limited to the effects of preservation of liver homeostasis. Reconstitution with recombinant human MBL before and during the HSV-2 infection dramatically lowered the viral titres in the liver. Taken together, the data show that MBL modulates the response to HSV-2 in mice by affecting neutralization of the virus. To analyse if MBL plays a role in establishment and progression of human HSV-2 infection we analysed MBL levels in the serum samples from asymptomatic (virus-exposed people who have never displayed symptoms of HSV-2 infection) and symptomatic HSV-2 patients (people with recurrent HSV-2 infections). We found that the frequency of the MBL deficiency (<100 ng/ml) was higher in the symptomatic group and significantly different from that in the asymptomatic group (P = 0.0369). This suggests that lack of MBL-mediated complement activation increases susceptibility to viral infection.

Characterization and quantification of mouse mannan-binding lectins (MBL-A and MBL-C) and study of acute phase responses.

Rat monoclonal antibodies (MoAbs) against mouse mannan-binding lectin (MBL)-A and MBL-C were generated and assays for MBL-A and MBL-C were constructed. This allowed for the quantitative analysis of both proteins for the first time. Previously only MBL-A has been quantified using less standardized methods. In a mouse serum pool the concentrations were now determined at 7.5 microg MBL-A and 45 microg MBL-C per ml. On gel permeation chromatography of mouse serum, MBL-A eluted corresponding to a M(r) of 850 kDa whereas the majority of MBL-C eluted corresponding to a Mr of 950 kDa. On sucrose density gradient centrifugation the sedimentation velocities of MBL-A and MBL-C were estimated at 7.3 S and 10.8 S, respectively. The MBL-A and MBL-C levels in 10 laboratory mice strains were compared and found to vary between 4 microg/ml to 12 microg/ml, and 16 microg/ml to 118 microg/ml, respectively. After the induction of acute phase responses by intraperitoneal injection of either casein or lipopolysaccharide (LPS), MBL-A was found to increase approximately two-fold, with a maximum after 32 h, while MBL-C did not increase significantly. In comparison, serum amyloid A component (SAA) peaked at 15 h with an approximate 100-fold increase.

Mannose-binding protein B allele confers protection against tuberculous meningitis.

Inhalation is the principal mode of entry for Mycobacterium tuberculosis in humans. Primary infection is usually restricted to the lungs and contiguous lymph nodes. In a subset of infected individuals, predominantly children, the infection is spread hematogenously to the meninges. The host factors that influence the development of tuberculous meningitis have not been well elucidated. The mannose-binding protein (MBP), a serum protein, is considered as an "ante-antibody." MBP has been shown to bind mycobacteria and acts as an opsonin in vitro. Although MBP plays a role in first-line host defense, it may under certain circumstances be deleterious to the host. In tuberculosis (TB), MBP may assist the spread of this intracellular pathogen. Therefore, we hypothesized that MBP genotypes that result in a phenotype of low MBP levels might be protective. We studied a well-defined South African population in which TB has reached epidemic levels. We found that the MBP B allele (G54D), which disrupts the collagen region of the protein and results in low MBP levels, was found in 22 of 79 (28%) of the TB-negative controls from the same community, compared with 12 of 91 (13%) of the patients with pulmonary TB (p < 0.017), and 5 of 64 (8%) of patients with tuberculous meningitis (p < 0.002). In addition, we found significantly lower serum MBP concentrations in TB-negative controls compared with postacute phase, fully recovered TB patients (p < 0.004). These findings suggest that the MBP B allele affords protection against tuberculous meningitis.

Relationships among capsular structure, phagocytosis, and mouse virulence in Klebsiella pneumoniae.

Klebsiella pneumoniae strains of the K2 capsular serotype are usually highly virulent in mice, which is in contrast to the low virulence of most other serotypes. Here we used a genetic approach to examine the relative contribution of capsule type to the virulence of K. pneumoniae in mice. We used wild-type strains expressing capsular polysaccharide (CPS) serotypes K2 (strain KPA1) and K21a (strains KPB1 and KPC1), which were then used to construct capsule-switched derivatives. The close proximity of the cps gene cluster to selectable his markers made it possible to mobilize the cps genes by conjugation from one serotype (donor) to another (recipient) and to obtain recombinants in which interserotype switching had occurred by reciprocal recombination. Each capsule-switched derivative examined of the KPA and KPC strain backgrounds produced a CPS that was immunologically and structurally identical to that of the donor. Strain background was confirmed by demonstrating restriction fragment length polymorphism patterns identical to those of the respective recipients. The parent strains were then compared with capsule-switched recombinants for phenotypic properties associated with virulence. Clearance from the bloodstreams of mice was rapid in serotype K21a strains of either wild-type or recombinant origin, whereas K2 strains remained viable in the blood during the period examined. These differences appeared to be dependent upon the CPS type but independent of strain background. Binding to macrophages was higher in K21a strains than in those with the K2 capsule and was also independent of the strain background. Both blood clearance and macrophage-binding activities were completely inhibited by yeast mannan, suggesting that they were mediated via the macrophage mannose receptor. The K2 parent strain was highly virulent to mice (50% lethal dose [LD50], 3 x 10(3)), while the K21a parent strains demonstrated low virulence (LD50, > 2 x 10(8)). Interestingly, the virulence of recombinant KPC10(cpsK2), originally of the KPC1(cpsK21a) background, was intermediate (LD50, 4 x 10(5)). In contrast, both cpsK21a recombinants of the originally virulent KPA1 (cpsK2) background became nearly avirulent (LD50, > 2 x 10(8)). Six additional serotypes (K12, K24, K32, K55, K62, and K67) were examined, and all showed a positive correlation between the ability of the Klebsiella serotype to interact with a human mannose receptor, as expressed by Cos I cell recombinants, and the LD50 of the serotype. These results suggest that expression of a capsule which is recognized by the mannose receptor markedly affects the interaction with macrophages and blood clearance.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytokines in the treatment of primary immunodeficiency.

Cytokines have great potential in the treatment of primary immunodeficiencies, which is just beginning to be realized. We discuss some general considerations in the use of cytokines in this setting, and review the clinical use of a number of cytokines. The best proven example to date is the use of interferon-gamma in chronic granulomatous disease, which significantly reduces infectious complications of this disease. We also discuss the potential use of interferon-gamma in the hyperimmunoglobulin E syndrome and in newborns. Granulocyte-colony stimulating factor usage in congenital neutropenias is reviewed. The use of IL-2, thymic hormones, and interferon-alpha are briefly discussed. Strategies for the design of clinical trials of cytokines in these uncommon illnesses are proposed.