Cell-type deconvolution with immune pathways identifies gene networks of host defense and immunopathology in leprosy

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Abstract

Transcriptome profiles derived from the site of human disease have led to the identification of genes that contribute to pathogenesis, yet the complex mixture of cell types in these lesions has been an obstacle for defining specific mechanisms. Leprosy provides an outstanding model to study host defense and pathogenesis in a human infectious disease, given its clinical spectrum, which interrelates with the host immunologic and pathologic responses. Here, we investigated gene expression profiles derived from skin lesions for each clinical subtype of leprosy, analyzing gene coexpression modules by cell-type deconvolution. In lesions from tuberculoid leprosy patients, those with the self-limited form of the disease, dendritic cells were linked with MMP12 as part of a tissue remodeling network that contributes to granuloma formation. In lesions from lepromatous leprosy patients, those with disseminated disease, macrophages were linked with a gene network that programs phagocytosis. In erythema nodosum leprosum, neutrophil and endothelial cell gene networks were identified as part of the vasculitis that results in tissue injury. The present integrated computational approach provides a systems approach toward identifying cell-defined functional networks that contribute to host defense and immunopathology at the site of human infectious disease.

Authors

Megan S. Inkeles, Rosane M.B. Teles, Delila Pouldar, Priscila R. Andrade, Cressida A. Madigan, David Lopez, Mike Ambrose, Mahdad Noursadeghi, Euzenir N. Sarno, Thomas H. Rea, Maria T. Ochoa, M. Luisa Iruela-Arispe, William R. Swindell, Tom H.M. Ottenhoff, Annemieke Geluk, Barry R. Bloom, Matteo Pellegrini, Robert L. Modlin

Bladder catheterization increases susceptibility to infection that can be prevented by prophylactic antibiotic treatment

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Abstract

Catheter-associated urinary tract infections (CAUTI) are the most common hospital-associated infections. Here, we report that bladder catheterization initiated a persistent sterile inflammatory reaction within minutes of catheter implantation. Catheterization resulted in increased expression of genes associated with defense responses and cellular migration, with ensuing rapid and sustained innate immune cell infiltration into the bladder. Catheterization also resulted in hypersensitivity to Enterococcus faecalis and uropathogenic Escherichia coli (UPEC) infection, in which colonization was achieved using an inoculum 100-fold lower than the ID₉₀ for infection of an undamaged urothelium with the same uropathogens. As the time of catheterization increased, however, colonization by the Gram-positive uropathogen E. faecalis was reduced, whereas catheterization created a sustained window of vulnerability to infection for Gram-negative UPEC over time. As CAUTI contributes to poorer patient outcomes and increased health care expenditures, we tested whether a single prophylactic antibiotic treatment, concurrent with catheterization, would prevent infection. We observed that antibiotic treatment protected against UPEC and E. faecalis bladder and catheter colonization as late as 6 hours after implantation. Thus, our study has revealed a simple, safe, and immediately employable intervention, with the potential to decrease one of the most costly hospital-incurred infections, thereby improving patient and health care economic outcome.

Authors

Matthieu Rousseau, H.M. Sharon Goh, Sarah Holec, Matthew L. Albert, Rohan B.H. Williams, Molly A. Ingersoll, Kimberly A. Kline

The antifibrotic drug pirfenidone promotes pulmonary cavitation and drug resistance in a mouse model of chronic tuberculosis

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Abstract

Pirfenidone is a recently approved antifibrotic drug for the treatment of idiopathic pulmonary fibrosis (IPF). Because tuberculosis (TB) is characterized by granulomatous inflammation in conjunction with parenchymal destruction and replacement fibrosis, we sought to determine whether the addition of pirfenidone as an adjunctive, host-directed therapy provides a beneficial effect during antimicrobial treatment of TB. We hypothesized that pirfenidone’s antiinflammatory and antifibrotic properties would reduce inflammatory lung damage and increase antimicrobial drug penetration in granulomas to accelerate treatment response. The effectiveness of adjunctive pirfenidone during TB drug therapy was evaluated using a murine model of chronic TB. Mice treated with standard therapy 2HRZ/4HR (H, isoniazid; R, rifampin; and Z, pyrazinamide) were compared with 2 alternative regimens containing pirfenidone (Pf) (2HRZPf/4HRPf and 2HRZPf/4HR). Contrary to our hypothesis, adjunctive pirfenidone use leads to reduced bacterial clearance and increased relapse rates. This treatment failure is closely associated with the emergence of isoniazid monoresistant bacilli, increased cavitation, and significant lung pathology. While antifibrotic agents may eventually be used as part of adjunctive host-directed therapy of TB, this study clearly demonstrates that caution must be exercised. Moreover, as pirfenidone becomes more widely used in clinical practice, increased patient monitoring would be required in endemic TB settings.

Authors

Bintou A. Ahidjo, Mariama C. Maiga, Elizabeth A. Ihms, Mamoudou Maiga, Alvaro A. Ordonez, Laurene S. Cheung, Sarah Beck, Bruno B. Andrade, Sanjay Jain, William R. Bishai

In vivo disruption of latent HSV by designer endonuclease therapy

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Abstract

A large portion of the global population carries latent herpes simplex virus (HSV), which can periodically reactivate, resulting in asymptomatic shedding or formation of ulcerative lesions. Current anti-HSV drugs do not eliminate latent virus from sensory neurons where HSV resides, and therefore do not eliminate the risk of transmission or recurrent disease. Here, we report the ability of HSV-specific endonucleases to induce mutations of essential HSV genes both in cultured neurons and in latently infected mice. In neurons, viral genomes are susceptible to endonuclease-mediated mutagenesis, regardless of the time of treatment after HSV infection, suggesting that both HSV lytic and latent forms can be targeted. Mutagenesis frequency after endonuclease exposure can be increased nearly 2-fold by treatment with a histone deacetylase (HDAC) inhibitor. Using a mouse model of latent HSV infection, we demonstrate that a targeted endonuclease can be delivered to viral latency sites via an adeno-associated virus (AAV) vector, where it is able to induce mutation of latent HSV genomes. These data provide the first proof-of-principle to our knowledge for the use of a targeted endonuclease as an antiviral agent to treat an established latent viral infection in vivo.

Authors

Martine Aubert, Emily A. Madden, Michelle Loprieno, Harshana S. DeSilva Feelixge, Laurence Stensland, Meei-Li Huang, Alexander L. Greninger, Pavitra Roychoudhury, Nixon Niyonzima, Thuy Nguyen, Amalia Magaret, Roman Galleto, Daniel Stone, Keith R. Jerome

Biofilm in group A streptococcal necrotizing soft tissue infections

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Abstract

Necrotizing fasciitis caused by group A streptococcus (GAS) is a life-threatening, rapidly progressing infection. At present, biofilm is not recognized as a potential problem in GAS necrotizing soft tissue infections (NSTI), as it is typically linked to chronic infections or associated with foreign devices. Here, we present a case of a previously healthy male presenting with NSTI caused by GAS. The infection persisted over 24 days, and the surgeon documented the presence of a “thick layer biofilm” in the fascia. Subsequent analysis of NSTI patient tissue biopsies prospectively included in a multicenter study revealed multiple areas of biofilm in 32% of the patients studied. Biopsies associated with biofilm formation were characterized by massive bacterial load, a pronounced inflammatory response, and clinical signs of more severe tissue involvement. In vitro infections of a human skin tissue model with GAS NSTI isolates also revealed multilayered fibrous biofilm structures, which were found to be under the control of the global Nra gene regulator. The finding of GAS biofilm formation in NSTIs emphasizes the urgent need for biofilm to be considered as a potential complicating microbiological feature of GAS NSTI and, consequently, emphasizes reconsideration of antibiotic treatment protocols.

Authors

Nikolai Siemens, Bhavya Chakrakodi, Srikanth Mairpady Shambat, Marina Morgan, Helena Bergsten, Ole Hyldegaard, Steinar Skrede, Per Arnell, Martin B. Madsen, Linda Johansson, INFECT Study Group, Julius Juarez, Lidija Bosnjak, Matthias Mörgelin, Mattias Svensson, Anna Norrby-Teglund

Soluble membrane attack complex is diagnostic for intraventricular shunt infection in children

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Abstract

BACKGROUND. Children treated with cerebrospinal fluid (CSF) shunts to manage hydrocephalus frequently develop shunt failure and/or infections, conditions that present with overlapping symptoms. The potential life-threatening nature of shunt infections requires rapid diagnosis; however, traditional microbiology is time consuming, expensive, and potentially unreliable. We set out to identify a biomarker that would identify shunt infection.

METHODS. CSF was assayed for the soluble membrane attack complex (sMAC) by ELISA in patients with suspected shunt failure or infection. CSF was obtained at the time of initial surgical intervention. Statistical analysis was performed to assess the diagnostic potential of sMAC in pyogenic-infected versus noninfected patients.

RESULTS. Children with pyogenic shunt infection had significantly increased sMAC levels compared with noninfected patients (3,211 ± 1,111 ng/ml vs. 26 ± 3.8 ng/ml, P = 0.0001). In infected patients undergoing serial CSF draws, sMAC levels were prognostic for both positive and negative clinical outcomes. Children with delayed, broth-only growth of commensal organisms (P. acnes, S. epidermidis, etc.) had the lowest sMAC levels (7.96 ± 1.7 ng/ml), suggesting contamination rather than shunt infection.

CONCLUSION. Elevated CSF sMAC levels are both sensitive and specific for diagnosing pyogenic shunt infection and may serve as a useful prognostic biomarker during recovery from infection.

FUNDING. This work was supported in part by the Impact Fund of Children’s of Alabama.

Authors

Theresa N. Ramos, Anastasia A. Arynchyna, Tessa E. Blackburn, Scott R. Barnum, James M. Johnston

Recognition of influenza H3N2 variant virus by human neutralizing antibodies

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Abstract

Since 2011, over 300 human cases of infection, especially in exposed children, with the influenza A H3N2 variant (H3N2v) virus that circulates in swine in the US have been reported. The structural and genetic basis for the lack of protection against H3N2v induced by vaccines containing seasonal H3N2 antigens is poorly understood. We isolated 17 human monoclonal antibodies (mAbs) that neutralized H3N2v virus from subjects experimentally immunized with an H3N2v candidate vaccine. Six mAbs exhibited very potent neutralizing activity (IC₅₀ < 200 ng/ml) against the H3N2v virus but not against current human H3N2 circulating strains. Fine epitope mapping and structural characterization of antigen-antibody complexes revealed that H3N2v specificity was attributable to amino acid polymorphisms in the 150-loop and the 190-helix antigenic sites on the hemagglutinin protein. H3N2v-specific antibodies also neutralized human H3N2 influenza strains naturally circulating between 1995 and 2005. These results reveal a high level of antigenic relatedness between the swine H3N2v virus and previously circulating human strains, consistent with the fact that early human H3 seasonal strains entered the porcine population in the 1990s and reentered the human population, where they had not been circulating, as H3N2v about a decade later. The data also explain the increased susceptibility to H3N2v viruses in young children, who lack prior exposure to human seasonal strains from the 1990s.

Authors

Sandhya Bangaru, Travis Nieusma, Nurgun Kose, Natalie J. Thornburg, Jessica A. Finn, Bryan S. Kaplan, Hannah G. King, Vidisha Singh, Rebecca M. Lampley, Gopal Sapparapu, Alberto Cisneros III, Kathryn M. Edwards, James C. Slaughter, Srilatha Edupuganti, Lilin Lai, Juergen A. Richt, Richard J. Webby, Andrew B. Ward, James E. Crowe Jr.