MHC class II DRB diversity predicts antigen recognition and is associated with disease severity in California sea lions naturally infected with Leptospira interrogans

We examined the associations between California sea lion MHC class II DRB (Zaca-DRB) configuration and diversity, and leptospirosis. As Zaca-DRB gene sequences are involved with antigen presentation of bacteria and other extracellular pathogens, we predicted that they would play a role in determining responses to these pathogenic spirochaetes. Specifically, we investigated whether Zaca-DRB diversity (number of genes) and configuration (presence of specific genes) explained differences in disease severity, and whether higher levels of Zaca-DRB diversity predicted the number of specific Leptospira interrogans serovars that a sea lion's serum would react against. We found that serum from diseased sea lions with more Zaca-DRB loci reacted against a wider array of serovars. Specific Zaca-DRB loci were linked to reactions with particular serovars. Interestingly, sea lions with clinical manifestation of leptospirosis that had higher numbers of Zaca-DRB loci were less likely to recover from disease than those with lower diversity, and those that harboured Zaca-DRB.C or -G were 4.5 to 5.3 times more likely to die from leptospirosis, regardless of the infective serovars. We propose that for leptospirosis, a disadvantage of having a wider range of antigen presentation might be increased disease severity due to immunopathology. Ours is the first study to examine the importance of Zaca-DRB diversity for antigen detection and disease severity following natural exposure to infective leptospires.

[Interstitial nephritis in pigs]

OBJECTIVE

Interstitial nephritis as a form of renal diseases can be found frequently among pigs. Nevertheless, prevalence and aetiology need to be investigated in more detail as reports about detailed analysis are lacking.

MATERIAL AND METHODS

In the present study, a total of 169 kidneys of conventionally and organically raised pigs were randomly chosen at slaughter and classified according to the degree of inflammation and the participating inflammatory cells. Moreover, PCV2 as an infectious agent was analysed by immunohistochemistry and in-situ hybridisation.

RESULTS

All of the investigated kidneys displayed mild interstitial lesions. Inflammatory cells included lymphocytes, macrophages, plasma cells, eosinophilic and neutrophilic granulocytes. Significant (p ≤ 0.0001) differences concerning the grade of inflammation and inflammatory cell occurrence could be observed between kidneys of conventionally and organically raised pigs. In comparison to conventionally raised pigs organically raised pigs showed significant (p ≤ 0.0001) more frequently a mild form of nephritis as well as a significant (p ≤ 0.0001) more frequent occurrence of lymphocytes and macrophages. In contrast to that, conventionally raised pigs had a significant (p ≤ 0.0001) higher occurrence rate of a mild to moderate form of nephritis as well as a significant (p ≤ 0.0001) higher level in occurrence of lymphocytes, macrophages, plasma cells, and neutrophilic granulocytes when compared to organically raised pigs. PCV2 DNA was detected in the kidney of only one animal.

CONCLUSION

Interstitial nephritis was found in conventionally and organically raised pigs and PCV2 was ruled out as a major pathogen for interstitial nephritis in slaughter pigs.

CLINICAL RELEVANCE

Because of the high prevalence and unknown cause further investigations are necessary to delineate the clinic relevance of this alteration and its pathogenesis.

In Vivo Chronic Stimulation Unveils Autoreactive Potential of Wiskott-Aldrich Syndrome Protein-Deficient B Cells

Wiskott–Aldrich syndrome (WAS) is a primary immunodeficiency caused by mutations in the gene encoding the hematopoietic-specific WAS protein (WASp). WAS is frequently associated with autoimmunity, indicating a critical role of WASp in maintenance of tolerance. The role of B cells in the induction of autoreactive immune responses in WAS has been investigated in several settings, but the mechanisms leading to the development of autoimmune manifestations have been difficult to evaluate in the mouse models of the disease that do not spontaneously develop autoimmunity. We performed an extensive characterization of Was^−/− mice that provided evidence of the potential alteration in B cell selection, because of the presence of autoantibodies against double-stranded DNA, platelets, and tissue antigens. To uncover the mechanisms leading to the activation of the potentially autoreactive B cells in Was^−/− mice, we performed in vivo chronic stimulations with toll-like receptors agonists (LPS and CpG) and apoptotic cells or infection with lymphocytic choriomeningitis virus. All treatments led to increased production of autoantibodies, increased proteinuria, and kidney tissue damage in Was^−/− mice. These findings demonstrate that a lower clearance of pathogens and/or self-antigens and the resulting chronic inflammatory state could cause B cell tolerance breakdown leading to autoimmunity in WAS.

VEGF and LPS synergistically silence inflammatory response to Plasmodium berghei infection and protect against cerebral malaria

Malaria infection induces, alongside endothelial damage and obstruction hypoxia, a potent inflammatory response similar to that observed in other systemic diseases caused by bacteria and viruses. Accordingly, it is increasingly recognised that cerebral malaria (CM), the most severe and life threatening complication of Plasmodium falciparum infection, bears a number of similarities with sepsis, an often fatal condition associated with a misregulated inflammatory response triggered by systemic microbial infections. Using a Plasmodium berghei ANKA mouse model, histology, immunohistochemistry and gene expression analysis, we showed that lipopolysaccharide S (LPS), at doses that normally induce inflammation tolerance, protects P. berghei infected mice against experimental CM (ECM). Vascular endothelial growth factor (VEGF) preserved blood vessel integrity, and the combination with LPS resulted in a strong synergistic effect. Treated mice did not develop ECM, showed a prolonged survival and failed to develop a significant inflammatory response and splenomegaly in spite of normal parasite loads. The protective role of VEGF was further confirmed by the observation that the treatment of P. berghei infected C57BL/6 and Balb/c mice with the VEGF receptor inhibitor axitinib exacerbates cerebral pathology and aggravates the course of infection. Infected mice treated with VEGF and LPS showed an induction of the anti-inflammatory genes Nrf2 and HO-1 and a suppression to basal levels of the genes IFN-γ and TNF-α. These results provide the rationale for developing new therapeutic approaches against CM and shed new light on how the inflammatory process can be modulated in the presence of systemic infectious diseases.

Vascular endothelial growth factor (VEGF) and lovastatin suppress the inflammatory response to Plasmodium berghei infection and protect against experimental cerebral malaria

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection, which is associated with high mortality and long-term cognitive impairment even when effective anti-parasitic treatment is administered. (1 , 2) Supportive therapy is needed to improve both morbidity and mortality associated with this condition. In an accompanying paper, we have demonstrated that in the Plasmodium berghei ANKA (PbA) rodent model, CM can be effectively prevented by a treatment combining sub-lethal doses of lipopolysaccharide S (LPS) and vascular endothelial growth factor (VEGF). Since LPS is not suitable for human therapy, we investigated whether lovastatin would represent a suitable substitute. This compound, widely used to lower cholesterol levels in plasma, shares with LPS the ability to elicit an anti-inflammatory response by activating the Nrf-2 gene, and when given to P. berghei-infected mice prevents to some extent the onset of CM. We show here that lovastatin- and VEGF-treated mice did not develop CM and showed few signs, if any, of endothelial damage and systemic inflammation. The combination treatment was much more effective than lovastatin and VEGF alone. Immunohistochemistry and gene expression analysis indicated that VEGF and LPS together overturned the two pathogenic mechanisms responsible for the development of CM: endothelial damage and disregulated activation of the inflammatory response. These findings provide the rationale for investigating the therapeutic potential of these compounds in human CM as well as in other inflammatory pathologies that respond poorly to steroid and non-steroid anti-inflammatory therapy.

Development of tertiary lymphoid structures in the kidneys of pigs with chronic leptospiral nephritis

Tertiary lymphoid organs (TLOs) are structures that are morphologically and functionally similar to secondary lymphoid organs. TLOs usually arise in a background of chronic inflammation. Several histological patterns of interstitial nephritis have been documented in porcine leptospirosis. Among them the lympho-follicular pattern is characterized by infiltrates of mononuclear cells organized in lymphoid follicle-like structures. Immunohistological analysis of 5 cases of porcine lympho-follicular nephritis associated with Leptospira Pomona infection demonstrated the presence of inflammatory cell populations, including B cells, T cells, macrophages and follicular dendritic cells (FDCs), which were compartmentalized as in TLOs. Immunohistochemistry for Leptospira Pomona revealed an intimate association between leptospiral antigen and FDCs. Overexpression of MHCII in different populations of both professional and non-professional antigen presenting cells was also demonstrated. FDCs play role during TLOs induction for their ability to retain non-self antigens in the form of immune complexes, thus causing persistent T cell activation, generation of a complex cytokine network and stimulation of humoral immunity. Sustained bacterial antigen presentation in the context of chronic leptospiral nephritis, may also lead to autoimmune mechanisms involved in the generation of TLOs. Whether lymphoid neogenesis and TLOs play a protective role in porcine leptospiral nephritis is still unclear.