MeninGene Recall study, substudy of the MeninGene study

Bacterial meningitis is a life-threatening disease.1 The estimated incidence is
2-5 per 100.000 people per year in developed countries and is up to ten-times
higher in resource poor countries.1-4 The most common causative bacteria is the
Streptococcus pneumonia in 70% of the cases. 1,2 Despite treatment with
antibiotics and dexamethasone the mortality and morbidity is still high.
Especially in pneumococcal meningitis the fatality rate is substantial (26%).1,2

Understanding host genetic factors by PBMC and whole blood stimulation
Bacterial meningitis is a complex disorder in which injury is caused, in part,
by the causative organism and, in part, by the host*s own inflammatory
response.5 Both host and bacterial genetic factors influence this process.6-8
Further characterisation of the interplay between host and bacterial factors is
needed to increase our understanding in the pathophysiology of bacterial
meningitis.
Genetic variations influencing susceptibility and severity of bacterial
meningitis are identified in genes coding for the immune system.8,10-12 To
enhance understanding of the functionality of these genetic variations
stimulated peripheral blood mononuclear cells (PBMCs) and whole blood can be
used to study the immune response.9 After stimulation of PBMCs and whole blood
with bacteria or pathogen-associated molecular patterns activation of the
immune response can be analysed by measuring cytokine production and mRNA
expression.9
Our hypothesis is that differences in the immune response activation will be
found when stimulating PBMCs and whole blood of survivors of bacterial
meningitis with different genetic profiles. The activation of the immune system
will be compared between individuals with risk genotypes and those with
protective genotypes. Also differences in the immune response activation
between survivors of bacterial meningitis and healthy controls will be
compared. Determination of differences in immune activation will give us more
insight in the pathophysiology of bacterial meningitis and will help us to find
new targets for prevention or treatment.

Long term effects of bacterial meningitis
In survivors of bacterial meningitis neurological and neuropsychological
sequelae occur frequently. Even in patients with a good recovery, cognitive
impairments are common and affect one third of patients with pneumococcal and
meningococcal meningitis.13 The affected cognitive domains differ between
studies, but a study with pooled data showed most of cognitive impairments were
associated with a decline in cognitive speed.13-16 Despite concerns about
possible harmful effects of adjunctive dexamethasone therapy on cognition,
earlier studies did not pointed out an association between dexamethasone and
cognitive impairments in bacterial meningitis patients.16 Nowadays
dexamethasone is a routine therapy in adults with bacterial meningitis,
therefore evaluation of the long term affect on cognitive functioning is still
important.
Another long term finding in bacterial meningitis patients is a decreased
quality of sleep. Sleep disturbance is common in survivors of meningitis (58%),
but the pathophysiological understanding is still unknown.17 Possibly,
structural brain lesions due to the inflammatory disease underlie sleep
disturbances in meningitis patients. Still, large patient groups in order to
assess the extent and frequency of sleep disorders in bacterial (and in
particular pneumococcal) meningitis are lacking. In this study we will assess
quality of sleep and screen for possible related depressive mood disorders in
patients and controls.
Furthermore we will determine pituitary hormone function in survivors of
bacterial meningitis and healthy controls. Various case reports and
retrospective studies suggest bacterial meningitis is a frequent cause of
pituitary dysfunction, but larger patient cohorts are lacking.18 Since hormone
dysfunction could be clinically important, we want to assess the long term
pituitary function in survivors of bacterial meningitis. In order to assess
clinical relevance of possible findings we will investigate correlations
between hormonal function and quality of sleep.

Adaptive immune system after bacterial meningitis
The innate immune system plays an important role in bacterial meningitis, but
the role of the adaptive immune system is still unclear. In this study, we want
to sequence gene expression of B cells in search for long term memory signals
that are unique to survivors of bacterial meningitis. Furthermore we will
measure pneumococcal and anti-neuronal antibodies to determine if an adequate
immune response did take place and patients did acquired long term protection
for new pneumococcal infections.

1. Characterize the interplay between host factors and bacterial factors and
the specific activation of inflammatory pathways.
2. Evaluate the expression of identified risk genes after activation of
inflammatory pathways in host immune mediating cells.
3. Determine differences in expression of immune genes in survivors of
bacterial meningitis and healthy controls.
4. Determine the long term effects of bacterial meningitis on quality of life,
quality of sleep and cognitive functioning
5. Evaluate pneumococcal and anti-neuronal antibody titers and expression
patterns in B cells of survivors of bacterial meningitis

In the MeninGene study, patient DNA was analyzed for genetic variations that
influence susceptibility and severity of disease. In this sub-study effects of
those genetic variations on the immune response are studied by stimulation
experiments. Furthermore, blood samples will be used to analyze baseline
activity of the immune system (cytokine, chemokine, complement and antibody
levels), hormone function and to isolate B cells to assess the B-cell
repertoire. After the blood withdrawal patients will have a neurological
examination, fill in questionnaires and perform a neuropsychological
assessment.

A single blood withdrawal of maximum 100 cc will be performed in each
participant. Risks of a blood withdrawal are negligible. Filling in the
questionnaires will take less than 30 minutes. The cognitive functioning will
be assessed with an online assessment taking one hour.