Research at the Iovino Laboratory

We investigate host-pathogen interactions during pathogenesis of bacterial invasive infectious disease of the brain.

Focus

Among unsolved causes of neurological dysfunctions in both children and adults there are Central Nervous System (CNS) bacterial infections and bacterial meningitis, a severe inflammation of the meninges occurring as a consequence of a bacterial infection of the brain. The main etiological cause of these bacterial infections is Streptococcus pneumoniae, also known as the pneumococcus.

Pneumococcal infections of the brain can be cured with antibiotics, however, the major burden of these infectious diseases is that, once bacteria invade the brain after trafficking across the blood-brain barrier, they interact with neurons causing neuronal death. Most of neurons cannot be either repaired or replaced.

World Health Organization (WHO) defines bacterial meningitis as a devastating disorder of the CNS primarily because, even if the bacterial infection is adequately cured, permanent neurological deficiencies, such as motor and intellectual delay, hearing loss, seizures, psychiatric disorders, occur in fifty percent of the cases, and they are all due to a neuronal injury caused by the infection. Finding the correct antibiotic therapy for a patient with bacterial meningitis could take a few days. In the meantime, bacteria in the brain kill and damage neurons in the brain. Successful treatments do not only have to eliminate the bacterial infection but must also protect neurons.

Our goal is to understand the molecular mechanisms of neuronal damage caused by pneumococcal infection to develop a new therapeutic strategy to block pneumococcal-neuron interaction and protect neurons. The pneumococcal conjugated vaccine (PCV) is the only prophylactic tool we currently have to prevent pneumococcal infections, however PCV is based on capsular polysaccharides which surround the bacterial cells and are poorly immunogenic; moreover, the protection is conferred only towards the pneumococcal serotypes included in the vaccine (thirteen serotypes in the PCV13), and there is no protection towards all the other serotypes, which are more than 100 in total. Since the introduction of PCV, cases of pneumococcal infections, including meningitis, caused by all serotypes not included in PCV, have increased.

Our goal is to identify the bacterial molecules that are “sensed” by microglia, the immune sentinels of the brain, and trigger the immune response which culminates with the killing of the bacteria by phagocytosis; we then want to use these molecules as immune-stimulatory agents to boost microglial immune response towards pneumococcal pathogens.  
Bacterial meningitis is routinely treated with β-lactamic-antibiotics, like penicillin.

There are two main problems related to the antibiotic treatment in the management of bacterial meningitis:

  1. β-lactam antibiotics have a poor penetration of the BBB due to their huge molecular size
  2. Because of the overuse and misuse of antibiotics in the last decades, the problem of antibiotic-resistance is a constant threat to face in clinics.

Bacteria are highly-versatile microorganisms and can change in response to antibiotics, new antibiotics can be discovered but bacteria can rapidly adapt and develop resistance.

Our goal is to establish a new antimicrobial treatment against antibiotic-resistant S. pneumoniae strains, especially the ones causing meningitis. 

Illustration of Pneumococcal infections of the brain.
Pneumococcal infections of the brain. Photo: Federico Iovino

After trafficking across the blood-brain barrier endothelium, S. pneumoniae in the brain encounters neurons and microglia. Neuronal damage can be caused by a direct interaction with the bacteria as a consequence of bacterial adhesion and invasion of neuronal cells, but also by an indirect interaction through the release of the toxin pneumolysin; microglia, the resident immune cells of the brain, have the fundamental function of eliminating bacteria by phagocytosis, on the other hand bacteria can also use microglia as niche to survive in the brain.

Projects

Neurological sequelae caused by meningitis: Interaction between pneumococci and neurons

Neurons are the main cell component of the brain, and mediate many functions controlled by the brain. Neurological sequelae caused by bacterial infection of the brain occur in 50% of meningitis survivors and are often related to neuronal damage. Our goal is to study how pneumococci can interact with neurons, invade and kill neuronal cells.

Blockade of pneumococcal interaction with neurons, a novel therapeutic strategy to prevent neuronal damage post-bacterial meningitis

Following up our recent discovery that ß-actin mediates pneumococcal binding to neuronal plasma membrane, we are now investigating novel approaches to block the interaction of S. pneumoniae with neuronal ß-actin to protect neurons during bacterial meningitis pathogenesis.

Study the role of neurons as "helper cells" in brain´s immunity towards bacterial infections

Neurons, as well as other eukaryotic cells, use the ubiquitin-proteasome system (UPS) and autophagy to degrade mis-folded proteins. Brain endothelial cells were previously shown to use the UPS system to kill intracellular pneumococci*. We want to investigate how neurons can use the UPS and autophagy to eliminate intracellular pneumococci and protect themselves from bacterial infections during meningitis pathogenesis.

The interplay between pneumococci and microglia, the primary immune cells of the brain

Study the biology of how microglia sense bacterial pathogens and initiate phagocytosis and/or neuroinflammatory process during meningitis pathogenesis; Study how pneumococci in the brain can survive and grow within microglia.

Study the pattern of entry of the brain by blood-borne S. pneumoniae

Using our bacteremia-derived meningitis mouse model and whole brain microscopy imaging, we want to identify what are the brain regions/lobes that are mostly affected by pneumococcal invasion upon penetration of the blood-brain barrier.

The relationship between bacterial meningitis and dementia

Many molecular processes, like the injury of neuronal cells and the neuro-inflammation process, are common in both bacterial meningitis and neurodegenerative diseases. We want to investigate to what extent the neuronal damage caused by a bacterial infection of the brain can increase the risk for onset of dementia, such as Parkinson's disease.

This project is a collaboration with the research groups of Professor Gilberto Fisone (Department of Neuroscience), Professor Per Svenningsson (Department of Clinical Neuroscience), Dr. Joana Pereira (Department of Neurobiology, Care Science and Society), and Professor Fang Fang (Institute of Environmental Medicine) at Karolinska Institutet.

Support

  • Swedish Research Council 
  • Karolinska Institutet Committee of Research 
  • Karolinska Institutet Research Foundation Grants
  • Bjarne Ahlström Foundation
  • European Society of Clinical Microbiology and Infectious Diseases (ESCMID)
  • StratNeuro
  • Petrus and Augusta Hedlund Foundation
  • Jeansson Foundation
  • Åke Wiberg Foundation
  • Clas Groschinsky Foundation
  • HKH Kronprinsessan Lovisa Association for Child Care
  • Magnus Bergvall Foundation
  • Tore Nilson Foundation
  • Loo and Hans Osterman Foundation
  • Fredrik and Ingrid Thuring Foundation
  • Stiftelsen Längmanska Kulturfonden

Collaborations

At Karolinska Institutet

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