Serological evidence of exposure to ebolaviruses in domestic pigs from Guinea

The genus Ebolavirus comprises several virus species with zoonotic potential and varying pathogenicity for humans. Ebolaviruses are considered to circulate in wildlife with occasional spillover events into the human population which then often leads to severe disease outbreaks. Several studies indicate a significant role of bats as reservoir hosts in the ebolavirus ecology. However, pigs from the Philippines have been found to be naturally infected with Reston virus (RESTV), an ebolavirus that is thought to only cause asymptomatic infections in humans. The recent report of ebolavirus‐specific antibodies in pigs from Sierra Leone further supports natural infection of pigs with ebolaviruses. However, susceptibility of pigs to highly pathogenic Ebola virus (EBOV) was only shown under experimental settings and evidence for natural infection of pigs with EBOV is currently lacking. Between October and December 2017, we collected 308 serum samples from pigs in Guinea, West Africa, and tested for the presence of ebolavirus‐specific antibodies with different serological assays. Besides reactivity to EBOV nucleoproteins in ELISA and Western blot for 19 (6.2%) and 13 (4.2%) samples, respectively, four sera recognized Sudan virus (SUDV) NP in Western blot. Furthermore, four samples specifically detected EBOV or SUDV glycoprotein (GP) in an indirect immunofluorescence assay under native conditions. Virus neutralization assay based on EBOV (Mayinga isolate) revealed five weakly neutralizing sera. The finding of (cross‐) reactive and weakly neutralizing antibodies suggests the exposure of pigs from Guinea to ebolaviruses or ebola‐like viruses with their pathogenicity as well as their zoonotic potential remaining unknown. Future studies should investigate whether pigs can act as an amplifying host for ebolaviruses and whether there is a risk for spillover events.     

Cumulative mortality of Aedes aegypti larvae treated with compounds

OBJECTIVE

To evaluate the larvicidal activity of Azadirachta indica, Melaleuca alternifolia, carapa guianensis essential oils and fermented extract of Carica papaya against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae).

METHODS

The larvicide test was performed in triplicate with 300 larvae for each experimental group using the third larval stage, which were exposed for 24h. The groups were: positive control with industrial larvicide (BTI) in concentrations of 0.37 ppm (PC1) and 0.06 ppm (PC2); treated with compounds of essential oils and fermented extract, 50.0% concentration (G1); treated with compounds of essential oils and fermented extract, 25.0% concentration (G2); treated with compounds of essential oils and fermented extract, 12.5% concentration (G3); and negative control group using water (NC1) and using dimethyl (NC2). The larvae were monitored every 60 min using direct visualization.

RESULTS

No mortality occurred in experimental groups NC1 and NC2 in the 24h exposure period, whereas there was 100% mortality in the PC1 and PC2 groups compared to NC1 and NC2. Mortality rates of 65.0%, 50.0% and 78.0% were observed in the groups G1, G2 and G3 respectively, compared with NC1 and NC2.

CONCLUSIONS

The association between three essential oils from Azadirachta indica, Melaleuca alternifolia, Carapa guianensis and fermented extract of Carica papaya was efficient at all concentrations. Therefore, it can be used in Aedes aegypti Liverpool third larvae stage control programs.     

CD169+ macrophages in lymph node and spleen critically depend on dual RANK and LTbetaR signaling

CD169⁺ macrophages reside in lymph node (LN) and spleen and play an important role in the immune defense against pathogens. As resident macrophages, they are responsive to environmental cues to shape their tissue-specific identity. We have previously shown that LN CD169⁺ macrophages require RANKL for formation of their niche and their differentiation. Here, we demonstrate that they are also dependent on direct lymphotoxin beta (LTβ) receptor (R) signaling. In the absence or the reduced expression of either RANK or LTβR, their differentiation is perturbed, generating myeloid cells expressing SIGN-R1 in LNs. Conditions of combined haploinsufficiencies of RANK and LTβR revealed that both receptors contribute equally to LN CD169⁺ macrophage differentiation. In the spleen, the Cd169-directed ablation of either receptor results in a selective loss of marginal metallophilic macrophages (MMMs). Using a RANKL reporter mouse, we identify splenic marginal zone stromal cells as a source of RANKL and demonstrate that it participates in MMM differentiation. The loss of MMMs had no effect on the splenic B cell compartments but compromised viral capture and the expansion of virus-specific CD8⁺ T cells. Taken together, the data provide evidence that CD169⁺ macrophage differentiation in LN and spleen requires dual signals from LTβR and RANK with implications for the immune response.

CD169⁺ macrophages are strategically localized at the lymphatic sinuses of lymph nodes (LNs) and the marginal zone of the spleen, where they capture lymph- and blood-borne antigens, respectively (1). These macrophages reside close to B cells and mesenchymal stromal cells. B cells are a constitutive source of lymphotoxin (LT) α and LTβ that bind to the LTβ receptor (R) as LTα₁β₂ heterotrimer (2). Lack of B cells and unconditional or B cell–specific ablation of LTα or LTβ lead to loss of CD169⁺ macrophages in LNs and the spleen (3–6). Conversely, B cell–specific overexpression of LTαβ results in an increase of their numbers (7). Furthermore, administration of the decoy fusion protein LTβR-Fc or LTβR inactivation negatively affects their presence in both organs (3, 8, 9). However, although the myeloid cell lineage has been shown to express LTβR (10–12), it remains unclear whether the dependency on LTβR signaling is direct or implies an intermediate cell partner such as the adjacent stromal cells (9, 13, 14).We have recently shown that receptor activator of NF-κB ligand (RANKL) from marginal zone reticular cells (MRCs) regulates the differentiation of CD169⁺ macrophages in the LN (15). Like LTα and LTβ, RANKL is a member of the TNF superfamily and binds to the signaling receptor RANK (16). Stromal RANKL activates the lymphatic endothelial cells to form a cellular niche for macrophages and directly stimulates their differentiation into the CD169⁺ macrophages of the subcapsular sinus (subcapsular sinus macrophages, SSMs). However, a role of stromal RANKL for the splenic CD169⁺ macrophages has not been addressed. LTαβ and RANKL share many similarities in their biological functions. They are both indispensable for the organogenesis of secondary lymphoid organs (17, 18), are involved in the organogenesis of the thymus (19), and contribute to the formation of the intestinal microfold cells (20). However, RANKL stands out for its role in osteoclastogenesis (16), while LTαβ regulates the production of homeostatic chemokines and the differentiation of follicular dendritic cells (2).In the context of partially overlapping functions, we scrutinized the implication of the RANK–RANKL and LTβR–LTαβ axes in the differentiation of LN and splenic CD169⁺ macrophages. Using Cd169-directed conditional deficiency of RANK or LTβR, we report that direct RANK and LTβR signals are required for their differentiation in the LN and the spleen. In the absence of the receptors, LN CD169⁺ macrophages were replaced by myeloid cells phenotypically similar to the SIGN-R1⁺ medullary sinus macrophages. Deficiency of one copy of either Rank or Ltbr alleles sufficed for a prominent decrease in macrophage numbers, but the heterozygous deletion of both genes had a compound effect. Altered macrophage differentiation had a negative impact on lymph-borne antigen transport to B cells. In the spleen, Cd169-directed RANK or LTβR deficiency elicited a selective loss of the CD169⁺ MMMs. By the use of a RANKL reporter mouse together with RT-qPCR of sorted splenic stromal subsets, we identified CCL19⁺ splenic MRCs as a source of RANKL and demonstrated in Ccl19-cre RANKL-deficient mice that stromal RANKL participates in MMM differentiation. Their specific loss had no effect on the marginal zone B cell compartment but compromised viral capture and the formation of the virus-specific CD8⁺ T cell response. Taken together, the data provide evidence that CD169⁺ macrophage differentiation is dependent on the dual signals emanating from LTβR and RANK, with implications for the immune response to lymph- and blood-borne pathogens.     

Étiologies et évolution des hépatites granulomateuses : étude rétrospective de 21 cas consécutifs

Purpose

To assess the etiologies and outcome of liver granulomatosis.

Methods

We analyzed all consecutive liver granulomatosis diagnosed in our internal medicine department from 2000 to 2008.

Results

Among 471 liver biopsies, 21 disclosed evidence of liver granulomatosis (4.5%), in sixteen women (76%) and five men, with a median age of 41 years. Thirteen were caucasians (62%). At the time of diagnosis, six (28.5%) had isolated abnormal liver function tests, and fifteen (71.4%) presented with clinical manifestations. The underlying cause was identified in 18 cases (85.7%). Eleven (52.3%) were systemic diseases: five (23.8%) primary biliary cirrhosis, two (9.5%) primary sclerosing cholangitis, two (9.5%) common variable immunodeficiency, one (4.7%) Sjögren's syndrome, and one (4.7%) Behçet's disease. Two (9.5%) patients had sarcoidosis. Three (14.3%) liver granulomatosis were of infectious origin (tuberculosis, schistosomiasis, and hepatitis C virus), two (9.5%) were neoplastic (Hodgkin's lymphoma and liver cell adenoma), and three (14.3%) were idiopathic. With a median of 38 months of follow-up, four patients (19%, two common variable immunodeficiency and two sarcoidosis) developed portal hypertension, independently of cirrhosis. One patient died of cryptococcosis.

Conclusion

In accordance with other European studies, systemic diseases are the main causes of hepatic granulomas. Liver granulomatosis related to common variable immunodeficiency and sarcoidosis are at risk of portal hypertension.