Streptococcus suis (S. suis) is an important porcine pathogen causing meningitis, arthritis, and septicemia. Serotypes 2 and 14 are the most common zoonotic ones worldwide, whereas serotypes 2, 9, ...and 7 are very important in pigs in Europe. To cause invasive infections S. suis needs to enter the bloodstream. Consequently, the immune response in blood represents an important line of defense and bacteremia plays a key role in the pathogenesis of invasive S. suis infections. We investigated the working hypothesis that S. suis strains of the same serotype but different clonal complex (CC) might exhibit substantial differences in the interaction with components of the immune system in porcine blood. The experimental design of this study includes comparative analysis of 8 virulent strains belonging to 4 serotypes with strains of the same serotype being genetically not closely related. Significant differences between two strains of the same serotype but different clonal complex were recorded in the flow cytometric analysis of association with different leukocytes for serotype 9 and 14. Our results demonstrate that the serotype 9 strain of CC94 shows significantly increased association with monocytes and survival in porcine blood of conventional piglets as well as a tendency towards decreased composition of C3 in plasma of these piglets in comparison to the serotype 9 strain of CC16. Correlation analysis of C3 deposition on the bacterial surface and survival in respective blood samples of 8-week-old piglets demonstrated a negative correlation indicating that C3 deposition is a crucial step to limit bacterial survival and proliferation of different S. suis pathotypes in the blood of these piglets. In summary, our results indicate that the capsule composition of a S. suis strain is not alone sufficient to determine association with leukocytes, activation of complement, induction of proinflammatory cytokines, oxidative burst, and bacterial survival in porcine blood. In this study, substantial differences in these host-pathogen interactions were observed between strains of the same serotype. Therefore, a more comprehensive characterization of the field isolates, including at least MLST analysis to determine the sequence type/clonal complex, is recommended.
(
) is a common swine pathogen but also poses a threat to human health in causing meningitis and severe cases of streptococcal toxic shock-like syndrome (STSLS). Therefore, it is crucial to ...understand how
interacts with the host immune system during bacteremia. As
has the ability to introduce d-alanine into its lipoteichoic acids (LTAs), we investigated the working hypothesis that cell wall modification by LTA d-alanylation influences the interaction of
with porcine blood immune cells. We created an isogenic mutant of
strain 10 by in-frame deletion of the d-alanine d-alanyl carrier ligase (DltA). d-alanylation of LTAs was associated with reduced phagocytosis of
by porcine granulocytes, reduced deposition of complement factor C3 on the bacterial surface, increased hydrophobicity of streptococci, and increased resistance to cationic antimicrobial peptides (CAMPs). At the same time, survival of
was not significantly increased by LTA d-alanylation in whole blood of conventional piglets with specific IgG. However, we found a distinct cytokine pattern as IL-1β but not tumor necrosis factor (TNF)-α levels were significantly reduced in blood infected with the Δ
mutant. In contrast to TNF-α, activation and secretion of IL-1β are inflammasome-dependent, suggesting a possible influence of LTA d-alanylation on inflammasome regulation. Especially in the absence of specific antibodies, the association of
with porcine monocytes was reduced by d-alanylation of its LTAs. This
-dependent phenotype was also observed with a non-encapsulated
double mutant indicating that it is independent of capsular polysaccharides. High antibody levels caused high levels of
-monocyte-association followed by inflammatory cell death and strong production of both IL-1β and TNF-α, while the influence of LTA d-alanylation of the streptococci became less visible. In summary, the results of this study expand previous findings on d-alanylation of LTAs in
and suggest that this pathogen specifically modulates association with blood leukocytes through this modification of its surface.
is a zoonotic agent causing meningitis in pigs and humans. Neutrophils, as the first line of defense against
infections, release neutrophil extracellular traps (NETs) to entrap pathogens. In this ...study, we investigated the role of the secreted nuclease A of
(SsnA) as a NET-evasion factor in vivo and in vitro. Piglets were intranasally infected with
strain 10 or an isogenic
mutant. DNase and NET-formation were analyzed in cerebrospinal fluid (CSF) and brain tissue. Animals infected with
strain 10 or S. suis 10ΔssnA showed the presence of NETs in CSF and developed similar clinical signs. Therefore, SsnA does not seem to be a crucial virulence factor that contributes to the development of meningitis in pigs. Importantly, DNase activity was detectable in the CSF of both infection groups, indicating that host nucleases, in contrast to bacterial nuclease SsnA, may play a major role during the onset of meningitis. The effect of DNase 1 on neutrophil functions was further analyzed in a 3D-cell culture model of the porcine blood-CSF barrier. We found that DNase 1 partially contributes to enhanced killing of
by neutrophils, especially when plasma is present. In summary, host nucleases may partially contribute to efficient innate immune response in the CSF.
•New model for antimicrobial treatment of Klebsiella pneumoniae septicaemia.•The apidaecin Api137 mediates killing of K. pneumoniae in porcine blood ex vivo.•Cytotoxicity and TNFα induction of Api137 ...treatment are comparable with cefquinome.
Klebsiella pneumoniae is an emerging invasive pathogen in humans and pigs. Resistance against multiple antibiotics in this species is a major health concern and the development of new antibiotics is urgently needed. The objective of this study was to investigate the effects of proline-rich antimicrobial peptides (PrAMPs) on the survival of K. pneumoniae strains in porcine blood.
We established a bactericidal assay with K. pneumoniae in fresh blood drawn from 4-week-old piglets. PrAMPs, namely the apidaecins Api137 and Api802 as well as the oncocin Onc112, were added to ex vivo-infected whole blood samples in order to study their bactericidal effects and, in the case of Api137, also immune responses.
A porcine invasive and a human iucA+rmpA+ K. pneumoniae strain showed prominent proliferation in porcine blood. Application of Api137 resulted in a dose-dependent prominent bactericidal effect killing the invasive porcine K. pneumoniae strain. Addition of 8 μg/mL Api137 also resulted in complete killing of the human iucA+rmpA+ strain. Cytotoxicity, haemolysis and induction of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNFα) in K. pneumoniae-infected porcine blood treated with Api137 was comparable with values obtained after application of 10 μg/mL cefquinome.
We describe a new non-rodent model for invasive K. pneumoniae bacteraemia and present promising data for the PrAMP Api137 for the control of infection with hypervirulent K. pneumoniae strains.
•Veterinary K. pneumoniae isolates show great diversity in siderophore profiles.•iucA+ rmpA- K. pneumoniae proliferate in blood of young piglets.•Supernatants of iucA+ strains boost bacterial growth ...in serum.•Opsonophagocytosis is crucial for bactericidal immunity of growing piglets.
Klebsiella (K.) pneumoniae causes different diseases in humans and animals including the life-threatening liver abscess syndrome and septicemia, respectively. However, host-pathogen interactions of K. pneumoniae in porcine blood have not been studied. We investigated the working hypothesis that only distinct K. pneumoniae strains have the capacity to survive in porcine blood and that this feature is associated with specific molecular markers such as sequence type, profile of siderophore genes and the regulator of the mucoid phenotype (rmp). Furthermore, we characterize the immune response in growing piglets leading to killing of an invasive K. pneumoniae strain.
The veterinary isolates showed great diversity in sequence types and profile of siderophore genes. Porcine isolates were mainly positive for the aerobactin gene iucA but did not carry rmpA and this genotype was associated with proliferation in blood of 4-week-old piglets. Supernatants of an iucA+ but not an iucA- strain boosted growth in porcine serum. Between four and eight weeks of age, piglets showed a prominent increase of IgM binding to K. pneumoniae. Immunglobulin M and complement were crucial for killing of a serum-resistant iucA+ porcine K. pneumoniae strain at eight weeks of age. Flow cytometry analysis confirmed induction of phagocytosis and oxidative burst mediated by serum samples of 8-week-old piglets. Based on our in vitro findings we propose that many porcine iucA+ rmpA- K. pneumoniae strains have the ability to cause bacteremia in young piglets in association with aerobactin-mediated iron acquisition and that this phenotype is lost as specific IgM increases after weaning.
Bacteremia is a hallmark of invasive
infections of pigs, often leading to septicemia, meningitis, or arthritis. An important defense mechanism of neutrophils is the generation of reactive oxygen ...species (ROS). In this study, we report high levels of ROS production by blood granulocytes after intravenous infection of a pig with high levels of
-specific antibodies and comparatively low levels of bacteremia. This prompted us to investigate the working hypothesis that the immunoglobulin-mediated oxidative burst contributes to the killing of
in porcine blood. Several
strains representing serotypes 2, 7, and 9 proved to be highly susceptible to the oxidative burst intermediate hydrogen peroxide, already at concentrations of 0.001%. The induction of ROS in granulocytes in
-infected reconstituted blood showed an association with pathogen-specific antibody levels. Importantly, inhibition of ROS production by the NADPH oxidase inhibitor apocynin led to significantly increased bacterial survival in the presence of high specific antibody levels. The oxidative burst rate of granulocytes partially depended on complement activation, as shown by specific inhibition. Furthermore, treatment of IgG-depleted serum with a specific IgM protease or heat to inactivate complement resulted in >3-fold decreased oxidative burst activity and increased bacterial survival in reconstituted porcine blood in accordance with an IgM-complement-oxidative burst axis. In conclusion, this study highlights an important control mechanism of
bacteremia in the natural host: the induction of ROS in blood granulocytes via specific immunoglobulins such as IgM.
All kidney transplant recipients followed up in the outpatient Kidney Transplantation Department of Strasbourg University Hospital between January 20, 2021, and June 3, 2021, with a negative history ...for COVID-19 and SARS-CoV-2 antispike IgG levels less than 50 arbitrary units (AU) per milliliter on the day of the first vaccine injection and 1 month after the second dose were included. All patients received a third vaccine dose between April 9, 2021, and May 12,2021. The study protocol was approved by the local ethics committee and written informed consent was obtained. Anti-receptor-binding domain IgG response after the third vaccine dose was assessed using the ARCHITECT IgG II Quant test (Abbott). According to the manufacturer, titers greater than 50 AU/mL were considered positive (detection range, 6.8-80 000 AU/mL; positive agreement, 99.4%; negative agreement, 99.6%). The results of this assay have been shown to correlate with in vitro neutralization of SARS-CoV-2.3 Mean differences adjusted for the factors in the Table were calculated using general linear models. All calculations were performed using GraphPad Prism version 8.0 (GraphPad) and SPSS version 2020.0.0 (IBM). P<.05 (2-sided) was considered statistically Significant.
Abstract
Background and Aims
Excessive complement activation is particularly important in the pathogenesis of IgAN nephropathy (IgAN). The relationship of complement CFH gene genetics and IgAN ...phenotype has not been clearly established in IgAN.
Method
We performed a genetic analysis of 234 French IgAN patients by next generation sequencing and Sanger. CFH polymorphisms were combined into haplotypes using the Michigan imputation Server1. CFH rare variants (MAF<0.1%) and haplotypes frequencies were compared to the 1k genome population of European ancestry. Recombinant full-length FH rare variants were produced and studied functionally in vitro.
Results
Genetic analysis revealed an enrichment in CFH non synonymous rare variants in IgAN patients (n = 234) compared to the reference population (n = 503) (5.1 versus 1.8%, p = 0.010). Interestingly, the identified variants preferentially located in FH functional domains. In vitro functional studies based on new functional Luminex® assays showed a decrease in C3b-binding, C3bBb decay-accelerating activity and/or FI-cofactor activity for 4 variants, classifying a newly identified variant as a pathogenic variant. CFH haplotypes distribution differed between the IgAN patients and controls (p<0.001), with a higher prevalence of the H3 haplotype (rs80029 c.184G>A, rs1061170 c.1204T>C, rs7542235 chr1:196854483 A>G, GTA) in IgAN patients (28.2 versus 21.1%, p = 0.0029), but this haplotype was not associated with renal survival.
Conclusion
In our series of French IgAN patients, CFH rare variants and haplotypes are associated with disease's susceptibility. Our results support the hypothesis of a complement dysregulation underlying the IgAN pathogenesis.
Abstract
Background and Aims
Acute kidney injury (AKI) increases long-term cardiovascular risk in non-transplanted patients. Delayed graft function (DGF) mimics AKI in kidney transplant recipients, ...yet its impact on their cardiovascular risk remains unclear.
Method
We investigated the impact of DGF on cardiovascular morbidity and mortality in kidney transplant recipients using data from patients across 17 French centres from the Astre and Divat cohorts. Included patients were aged 18 years or older, transplanted between 2008 and 2022, with follow-up until 31/03/2023. DGF was defined as the need for hemodialysis within the first week following renal transplantation. The primary outcome was the impact of DGF on the occurrence of a cardiovascular event (composite endpoint including cardiovascular death, coronary artery disease, stroke, heart failure), adjusted for conventional cardiovascular risk factors and glomerular filtration rate at 3 months. Analyses were performed using univariate and multivariate Cox models.
Results
Among the 19, 837 patients transplanted during the inclusion period, 3, 794 experienced DGF (19.1%). In the multivariate Cox model, DGF was strongly associated with cardiovascular risk (adjusted Hazard Ratio HR = 1.37, P < .0001), independently of renal function. Other significantly associated variables included age, duration of dialysis, expanded criteria donors, diabetes, dyslipidemia, smoking, initial nephropathy, and various cardiovascular comorbidities. The effect of DGF was predominantly observed in men, patients over 40, and those at lower cardiovascular risk. DGF was associated with independent cardiac outcomes, such as cardiovascular death (HR 1.31), coronaropathy (HR 1.51), heart failure (HR 1.61 and arrhythmia (HR 1.38), but not with stroke (HR 0.99) nor peripheral artery disease (HR 0.97).
Conclusion
DGF is an independent risk factor for the occurrence of cardiovascular events in kidney transplant recipients. Strategies aimed at minimizing DGF could potentially reduce cardiovascular complications in these patients.
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