14 results found
Siggins MK, Thwaites RS, Openshaw PJM, 2021, Durability of immunity to SARS-CoV-2 and other respiratory viruses: (Trends in microbiology, 29, 648-662, 2021)., Trends in Microbiology, ISSN: 0966-842X
Siggins MK, Thwaites RS, Openshaw PJM, 2021, Durability of Immunity to SARS-CoV-2 and Other Respiratory Viruses, TRENDS IN MICROBIOLOGY, Vol: 29, Pages: 648-662, ISSN: 0966-842X
Thwaites RS, Sanchez Sevilla Uruchurtu A, Siggins MK, et al., 2021, Inflammatory profiles across the spectrum of disease reveal a distinct role for GM-CSF in severe COVID-19, Science Immunology, Vol: 6, Pages: 1-17, ISSN: 2470-9468
While it is now widely accepted that host inflammatory responses contribute to lung injury, the pathways that drive severity and distinguish coronavirus disease 2019 (COVID-19) from other viral lung diseases remain poorly characterized. We analyzed plasma samples from 471 hospitalized patients recruited through the prospective multicenter ISARIC4C study and 39 outpatients with mild disease, enabling extensive characterization of responses across a full spectrum of COVID-19 severity. Progressive elevation of levels of numerous inflammatory cytokines and chemokines (including IL-6, CXCL10, and GM-CSF) were associated with severity and accompanied by elevated markers of endothelial injury and thrombosis. Principal component and network analyses demonstrated central roles for IL-6 and GM-CSF in COVID-19 pathogenesis. Comparing these profiles to archived samples from patients with fatal influenza, IL-6 was equally elevated in both conditions whereas GM-CSF was prominent only in COVID-19. These findings further identify the key inflammatory, thrombotic, and vascular factors that characterize and distinguish severe and fatal COVID-19.
Triantafyllou E, Gudd C, Mawhin M-A, et al., 2020, PD-1 blockade improves Kupffer cell bacterial clearance in acute liver injury, Journal of Clinical Investigation, Vol: 131, Pages: 1-16, ISSN: 0021-9738
Acute liver failure (ALF) patients display systemic innate immune suppression and increased susceptibility to infections. PD-1 expression by macrophages has been associated with immune suppression during sepsis and cancer. We therefore examined the role of PD-1/PD-L1 pathway in regulating Kupffer cell inflammatory and antimicrobial responses in acetaminophen (APAP) induced acute liver injury. Using intravital imaging and flow cytometry we found impaired Kupffer cell bacterial clearance and systemic bacterial dissemination in mice with liver injury. Increased PD-1 and PD-L1 expression was detected in Kupffer cells and lymphocyte subsets, respectively, during resolution of injury. Gene expression profiling of PD-1+ Kupffer cells revealed an immune-suppressive profile and reduced pathogen responses. Compared to wild-type, PD-1 deficient or anti-PD-1 treated mice with liver injury showed improved Kupffer cell bacterial clearance, reduced tissue bacterial load and protection from sepsis. Blood sample analyses of ALF patients revealed enhanced PD-1 and PD-L1 expression of monocytes and lymphocytes, respectively, and that plasma soluble PD-L1 levels predict patient outcome and sepsis. PD-1 in vitro blockade restored monocyte functionality. Our study describes a role for PD-1/PD-L1 axis in suppressing Kupffer cell and monocyte antimicrobial responses after liver injury and suggests anti-PD-1 immunotherapy as a strategy to reduce infection susceptibility in ALF.
Siggins MK, Lynskey NN, Lamb L, et al., 2020, Extracellular bacterial lymphatic metastasis drives Streptococcus pyogenes systemic infection, Nature Communications, Vol: 11, ISSN: 2041-1723
Unassisted metastasis through the lymphatic system is a mechanism of dissemination thus far ascribed only to cancer cells. Here, we report that Streptococcus pyogenes also hijack lymphatic vessels to escape a local infection site, transiting through sequential lymph nodes and efferent lymphatic vessels to enter the bloodstream. Contrasting with previously reported mechanisms of intracellular pathogen carriage by phagocytes, we show S. pyogenes remain extracellular during transit, first in afferent and then efferent lymphatics that carry the bacteria through successive draining lymph nodes. We identify streptococcal virulence mechanisms important for bacterial lymphatic dissemination and show that metastatic streptococci within infected lymph nodes resist and subvert clearance by phagocytes, enabling replication that can seed intense bloodstream infection. The findings establish the lymphatic system as both a survival niche and conduit to the bloodstream for S. pyogenes, explaining the phenomenon of occult bacteraemia. This work provides new perspectives in streptococcal pathogenesis with implications for immunity.
Sharma H, Turner CE, Siggins MK, et al., 2019, Toxic shock syndrome toxin-1 evaluation and antibiotic impact in a transgenic model of staphylococcal soft tissue infection, mSphere, Vol: 4, ISSN: 2379-5042
Nonmenstrual toxic shock syndrome (nmTSS), linked to TSST-1-producing CC30 Staphylococcus aureus, is the leading manifestation of toxic shock syndrome (TSS). Due to case rarity and a lack of tractable animal models, TSS pathogenesis is poorly understood. We developed an S. aureus abscess model in HLA class II transgenic mice to investigate pathogenesis and treatment. TSST-1 sensitivity was established using murine spleen cell proliferation assays and cytokine assays following TSST-1 injection in vivo. HLA-DQ8 mice were infected subcutaneously with a tst-positive CC30 methicillin-sensitive S. aureus clinical TSS-associated isolate. Mice received intraperitoneal flucloxacillin, clindamycin, flucloxacillin and clindamycin, or a control reagent. Abscess size, bacterial counts, TSST-1 expression, and TSST-1 bioactivity were measured in tissues. Antibiotic effects were compared with the effects of control reagent. Purified TSST-1 expanded HLA-DQ8 T-cell Vβ subsets 3 and 13 in vitro and instigated cytokine release in vivo, confirming TSST-1 sensitivity. TSST-1 was detected in abscesses (0 to 8.0 μg/ml) and draining lymph nodes (0 to 0.2 μg/ml) of infected mice. Interleukin 6 (IL-6), gamma interferon (IFN-γ), KC (CXCL1), and MCP-1 were consistent markers of inflammation during infection. Clindamycin-containing antibiotic regimens reduced abscess size and TSST-1 production. Infection led to detectable TSST-1 in soft tissues, and TSST-1 was detected in draining lymph nodes, events which may be pivotal to TSS pathogenesis. The reduction in TSST-1 production and lesion size after a single dose of clindamycin underscores a potential role for adjunctive clindamycin at the start of treatment of patients suspected of having TSS to alter disease progression.
Lamb LE, Siggins MK, Scudamore C, et al., 2018, Impact of contusion injury on intramuscular emm1 group A-Streptococcus infection and Lymphatic spread, Virulence, Vol: 9, Pages: 1074-1084, ISSN: 2150-5594
Invasive group A Streptococcus (iGAS) is frequently associated with emm1 isolates, with an attendant mortality of around 20%. Cases occasionally arise in previously healthy individuals with a history of upper respiratory tract infection, soft tissue contusion, and no obvious portal of entry. Using a new murine model of contusion, we determined the impact of contusion on iGAS bacterial burden and phenotype. Calibrated mild blunt contusion did not provide a focus for initiation or seeding of GAS that was detectable following systemic GAS bacteremia, but instead enhanced GAS migration to the local draining lymph node following GAS inoculation at the same time and site of contusion. Increased migration to lymph node was associated with emergence of mucoid bacteria, although was not specific to mucoid bacteria. In one study, mucoid colonies demonstrated a significant increase in capsular hyaluronan that was not linked to a covRS or rocA mutation, but to a deletion in the promoter of the capsule synthesis locus, hasABC, resulting in a strain with increased fitness for lymph node migration. In summary, in the mild contusion model used, we could not detect seeding of muscle by GAS. Contusion promoted bacterial transit to the local lymph node. The consequences of contusion-associated bacterial lymphatic migration may vary depending on the pathogen and virulence traits selected.
Lynskey NN, Reglinski M, Calay D, et al., 2017, Multi-functional mechanisms of immune evasion by the streptococcal complement inhibitor C5a peptidase, PLOS Pathogens, Vol: 13, Pages: 1-29, ISSN: 1553-7366
The complement cascade is crucial for clearance and control of invading pathogens, and as such is a key target for pathogen mediated host modulation. C3 is the central molecule of the complement cascade, and plays a vital role in opsonization of bacteria and recruitment of neutrophils to the site of infection. Streptococcal species have evolved multiple mechanisms to disrupt complement-mediated innate immunity, among which ScpA (C5a peptidase), a C5a inactivating enzyme, is widely conserved. Here we demonstrate for the first time that pyogenic streptococcal species are capable of cleaving C3, and identify C3 and C3a as novel substrates for the streptococcal ScpA, which are functionally inactivated as a result of cleavage 7 amino acids upstream of the natural C3 convertase. Cleavage of C3a by ScpA resulted in disruption of human neutrophil activation, phagocytosis and chemotaxis, while cleavage of C3 generated abnormally-sized C3a and C3b moieties with impaired function, in particular reducing C3 deposition on the bacterial surface. Despite clear effects on human complement, expression of ScpA reduced clearance of group A streptococci in vivo in wildtype and C5 deficient mice, and promoted systemic bacterial dissemination in mice that lacked both C3 and C5, suggesting an additional complement-independent role for ScpA in streptococcal pathogenesis. ScpA was shown to mediate streptococcal adhesion to both human epithelial and endothelial cells, consistent with a role in promoting bacterial invasion within the host. Taken together, these data show that ScpA is a multi-functional virulence factor with both complement-dependent and independent roles in streptococcal pathogenesis.
Smith DS, Siggins MK, Gierula M, et al., 2016, Identification of commonly expressed exoproteins and proteolytic cleavage events by proteomic mining of clinically-relevant UK isolates of Staphylococcus aureus, Microbial Genomics, Vol: 2, ISSN: 2057-5858
The range of exoproteins and core exoproteome of 14 S. aureus isolates representing major lineages associated with asymptomatic carriage and clinical disease in the United Kingdom was identified by mass spectrometry proteomics using a combined database incorporating sequences derived from 39 S. aureus genomes. In all, 632 different proteins were identified and, of these, only 52 (8%) were found in all 14 isolates whereas 144 (23%) were found in just a single isolate. Comparison of the observed mass of each protein (based on migration by SDS-polyacrylamide electrophoresis) with its predicted mass (based on amino acid sequence) suggested that 95% of the proteins identified were not subject to any major post translational modification. Migration of 5% of proteins was not as expected: 1% of proteins migrated at a mass greater than predicted, while 4% of proteins appeared to have undergone proteolytic cleavage; these included SsaA2, Aur, SspP, Ebh as well as BlaR1, MecR1, FsH, OatA and LtaS. Intriguingly, a truncated SasG was produced by a single CC8 USA300-like strain. The analysis provided evidence of the marked heterogeneity in protein expression by S. aureus in broth, while yielding a core but narrow common exoproteome.
Hart PJ, O'Shaughnessy CM, Siggins MK, et al., 2016, Differential Killing of Salmonella enterica Serovar Typhi by Antibodies Targeting Vi and Lipopolysaccharide O:9 Antigen, PLOS One, Vol: 11, ISSN: 1932-6203
Salmonella enterica serovar Typhi expresses a capsule of Vi polysaccharide, while most Salmonella serovars, including S. Enteritidis and S. Typhimurium, do not. Both S. Typhi and S. Enteritidis express the lipopolysaccharide O:9 antigen, yet there is little evidence of cross-protection from anti-O:9 antibodies. Vaccines based on Vi polysaccharide have efficacy against typhoid fever, indicating that antibodies against Vi confer protection. Here we investigate the role of Vi capsule and antibodies against Vi and O:9 in antibody-dependent complement- and phagocyte-mediated killing of Salmonella. Using isogenic Vi-expressing and non-Vi-expressing derivatives of S. Typhi and S. Typhimurium, we show that S. Typhi is inherently more sensitive to serum and blood than S. Typhimurium. Vi expression confers increased resistance to both complement- and phagocyte-mediated modalities of antibody-dependent killing in human blood. The Vi capsule is associated with reduced C3 and C5b-9 deposition, and decreased overall antibody binding to S. Typhi. However, purified human anti-Vi antibodies in the presence of complement are able to kill Vi-expressing Salmonella, while killing by anti-O:9 antibodies is inversely related to Vi expression. Human serum depleted of antibodies to antigens other than Vi retains the ability to kill Vi-expressing bacteria. Our findings support a protective role for Vi capsule in preventing complement and phagocyte killing of Salmonella that can be overcome by specific anti-Vi antibodies, but only to a limited extent by anti-O:9 antibodies.
Siggins MK, Gill SK, Langford PR, et al., 2015, PHiD-CV induces anti-Protein D antibodies but does not augment pulmonary clearance of nontypeable Haemophilus influenzae in mice, Vaccine, Vol: 33, Pages: 4954-4961, ISSN: 1873-2518
BackgroundA recently-licensed 10-valent pneumococcal conjugate vaccine (PHiD-CV; Synflorix, GSK) uses Protein D from Haemophilus influenzae as a carrier protein. PHiD-CV therefore has the potential to provide additional protection against nontypeable H. influenzae (NTHi). NTHi frequently causes respiratory tract infections and is associated with significant morbidity and mortality worldwide and there is currently no vaccine.MethodsWe developed mouse models of NTHi infection and influenza/NTHi superinfection. Mice were immunized with PHiD-CV, heat-killed NTHi, or a 13-valent pneumococcal conjugate vaccine that did not contain Protein D (PCV13; Prevenar, Pfizer) and then infected intranasally with NTHi.ResultsInfection with NTHi resulted in weight loss, inflammation and airway neutrophilia. In a superinfection model, prior infection with pandemic H1N1 influenza virus (strain A/England/195/2009) augmented NTHi infection severity, even with a lower bacterial challenge dose. Immunization with PHiD-CV produced high levels of antibodies that were specific against Protein D, but not heat-killed NTHi. Immunization with PHiD-CV led to a slight reduction in bacterial load, but no change in disease outcome.ConclusionsPHiD-CV induced high levels of Protein D-specific antibodies, but did not augment pulmonary clearance of NTHi. We found no evidence to suggest that PHiD-CV will offer added benefit by preventing NTHi lung infection.
Siggins MK, O'Shaughnessy CM, Pravin J, et al., 2014, Differential timing of antibody-mediated phagocytosis and cell-free killing of invasive African Salmonella allows immune evasion, EUROPEAN JOURNAL OF IMMUNOLOGY, Vol: 44, Pages: 1093-1098, ISSN: 0014-2980
Siggins MK, Cunningham AF, Marshall JL, et al., 2011, Absent bactericidal activity of mouse serum against invasive African nontyphoidal Salmonella results from impaired complement function but not a lack of antibody (vol 186, pg 2365, 2011), JOURNAL OF IMMUNOLOGY, Vol: 186, Pages: 4527-4527, ISSN: 0022-1767
Siggins MK, Cunningham AF, Marshall JL, et al., 2011, Absent Bactericidal Activity of Mouse Serum against Invasive African Nontyphoidal Salmonella Results from Impaired Complement Function but Not a Lack of Antibody, JOURNAL OF IMMUNOLOGY, Vol: 186, Pages: 2365-2371, ISSN: 0022-1767
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