25 research outputs found
Positively Selected Codons in Immune-Exposed Loops of the Vaccine Candidate OMP-P1 of Haemophilus influenzae
The high levels of variation in surface epitopes can be considered as an evolutionary hallmark of immune selection. New computational tools enable analysis of this variation by identifying codons that exhibit high rates of amino acid changes relative to the synonymous substitution rate. In the outer membrane protein P1 of Haemophilus influenzae, a vaccine candidate for nontypeable strains, we identified four codons with this attribute in domains that did not correspond to known or assumed B- and T-cell epitopes of OMP-P1. These codons flank hypervariable domains and do not appear to be false positives as judged from parsimony and maximum likelihood analyses. Some closely spaced positively selected codons have been previously considered part of a transmembrane domain, which would render this region unsuited for inclusion in a vaccine. Secondary structure analysis, three-dimensional structural database searches, and homology modeling using FadL of E. coli as a structural homologue, however, revealed that all positively selected codons are located in or near extracellular looping domains. The spacing and level of diversity of these positively selected and exposed codons in OMP-P1 suggest that vaccine targets based on these and conserved flanking residues may provide broad coverage in H. influenzae
Lipid Motif of a Bacterial Antigen Mediates Immune Responses via TLR2 Signaling
The cross-talk between the innate and the adaptive immune system is facilitated
by the initial interaction of antigen with dendritic cells. As DCs express a
large array of TLRs, evidence has accumulated that engagement of these molecules
contributes to the activation of adaptive immunity. We have evaluated the
immunostimulatory role of the highly-conserved outer membrane lipoprotein P6
from non-typeable Haemophilus influenzae (NTHI) to determine
whether the presence of the lipid motif plays a critical role on its
immunogenicity. We undertook a systematic analysis of the role that the lipid
motif plays in the activation of DCs and the subsequent stimulation of
antigen-specific T and B cells. To facilitate our studies, recombinant P6
protein that lacked the lipid motif was generated. Mice immunized with
non-lipidated rP6 were unable to elicit high titers of anti-P6 Ig. Expression of
the lipid motif on P6 was also required for proliferation and cytokine secretion
by antigen-specific T cells. Upregulation of T cell costimulatory molecules was
abrogated in DCs exposed to non-lipidated rP6 and in
TLR2−/− DCs exposed to native P6, thereby resulting
in diminished adaptive immune responses. Absence of either the lipid motif on
the antigen or TLR2 expression resulted in diminished cytokine production from
stimulated DCs. Collectively; our data suggest that the lipid motif of the
lipoprotein antigen is essential for triggering TLR2 signaling and effective
stimulation of APCs. Our studies establish the pivotal role of a bacterial lipid
motif on activating both innate and adaptive immune responses to an otherwise
poorly immunogenic protein antigen
Modelling the impact of toxic and disturbance stress on white-tailed eagle (Haliaeetus albicilla) populations
Several studies have related breeding success and survival of sea eagles to toxic or non-toxic stress separately. In the present investigation, we analysed single and combined impacts of both toxic and disturbance stress on populations of white-tailed eagle (Haliaeetus albicilla), using an analytical single-species model. Chemical and eco(toxico)logical data reported from laboratory and field studies were used to parameterise and validate the model. The model was applied to assess the impact of ∑PCB, DDE and disturbance stress on the white-tailed eagle population in The Netherlands. Disturbance stress was incorporated through a 1.6% reduction in survival and a 10–50% reduction in reproduction. ∑PCB contamination from 1950 up to 1987 was found to be too high to allow the return of white-tailed eagle as a breeding species in that period. ∑PCB and population trends simulated for 2006–2050 suggest that future population growth is still reduced. Disturbance stress resulted in a reduced population development. The combination of both toxic and disturbance stress varied from a slower population development to a catastrophical reduction in population size, where the main cause was attributed to the reduction in reproduction of 50%. Application of the model was restricted by the current lack of quantitative dose–response relationships between non-toxic stress and survival and reproduction. Nevertheless, the model provides a first step towards integrating and quantifying the impacts of multiple stressors on white-tailed eagle populations
Glycosaminoglycan Binding Facilitates Entry of a Bacterial Pathogen into Central Nervous Systems
Certain microbes invade brain microvascular endothelial cells (BMECs) to breach the blood-brain barrier (BBB) and establish central nervous system (CNS) infection. Here we use the leading meningitis pathogen group B Streptococcus (GBS) together with insect and mammalian infection models to probe a potential role of glycosaminoglycan (GAG) interactions in the pathogenesis of CNS entry. Site-directed mutagenesis of a GAG-binding domain of the surface GBS alpha C protein impeded GBS penetration of the Drosophila BBB in vivo and diminished GBS adherence to and invasion of human BMECs in vitro. Conversely, genetic impairment of GAG expression in flies or mice reduced GBS dissemination into the brain. These complementary approaches identify a role for bacterial-GAG interactions in the pathogenesis of CNS infection. Our results also highlight how the simpler yet genetically conserved Drosophila GAG pathways can provide a model organism to screen candidate molecules that can interrupt pathogen-GAG interactions for future therapeutic applications
Efficient identification of novel mutations in patients with limb girdle muscular dystrophy
X-inactivation modifies disease severity in female carriers of murine X-linked Alport syndrome
Background. Female carriers of X-linked Alport syndrome (XLAS) demonstrate variability in clinical phenotype that, unlike males, cannot be correlated with genotype. X-inactivation, the method by which females (XX) silence transcription from one X chromosome in order to achieve gene dosage parity with males (XY), likely modifies the carrier phenotype, but this hypothesis has not been tested directly