Immune response deviation and enhanced expression of chemokine receptor CCR4 in TBI patients due to unknown serum factors

BACKGROUND: Severe brain trauma leads to an activation of the immune system. To this date, neither the exact perturbation of the specific immune reaction induced by the traumatic brain injury (TBI), nor the interactions leading to the infiltration of peripheral immune cells into the brain are fully understood. PATIENTS AND METHODS: Serum was collected from 17 patients with TBI and a long bone fracture, 24 patients with an isolated long bone fracture and from healthy individuals. The effect of the serum on normal human monocytes and T-lymphocytes was tested in vitro by assessing proliferation and expression of surface markers, chemokine receptors and cytokines. RESULTS: Serum collected from patients with a TBI and a long bone fracture increased the expression of the chemokine receptor CCR4 in monocytes when compared to patients with an isolated long bone fracture. Extending this comparison to T-lymphocytes, the serum from TBI patients induced lower proliferation rates and decreased expression of the pro-inflammatory cytokine TNF-alpha, while simultaneously increasing the secretion of immune-modulatory cytokines (IL-4, IL-10 and TGF-beta) (p<0.05). CONCLUSION: Patients with a TBI release currently unknown soluble factors into the circulating blood that up regulate expression of chemokine receptor CCR4 in peripheral blood monocytes whilst concurrently inducing expression of immunosuppressive cytokines by activated T-lymphocytes.

Effects of HIV type-1 immune selection on susceptability to integrase inhibitor resistance

BACKGROUND: All site-specific interactions between HIV type-1 (HIV-1) subtype, human leukocyte antigen (HLA)-associated immune selection and integrase inhibitor resistance are not completely understood. We examined naturally occurring polymorphisms in HIV-1 integrase sequences from 342 antiretroviral-naive individuals from the Western Australian HIV Cohort Study and the Swiss HIV Cohort Study. METHODS: Standard bulk sequencing and sequence-based typing were used to generate integrase sequences and high-resolution HLA genotypes, respectively. Viral residues were examined with respect to drug resistance mutations and CD8(+) T-cell escape mutations. RESULTS: In both predominantly subtype B cohorts, 12 of 38 sites that mediate integrase inhibitor resistance mutations were absolutely conserved, and these included the primary resistance mutations. There were 18 codons with non-primary drug resistance-associated substitutions at rates of up to 58.8% and eight sites with alternative polymorphisms. Five viral residues were potentially subject to dual-drug and HLA-associated immune selection in which both selective pressures either drove the same amino acid substitution (codons 72, 157 and 163) or HLA alleles were associated with an alternative polymorphism that would alter the genetic barrier to resistance (codons 125 and 193). The common polymorphism T125A, which was characteristic of non-subtype B and was also associated with carriage of HLA-B*57/*5801, increased the mutational barrier to the resistance mutation T125K. CONCLUSIONS: Primary integrase inhibitor resistance mutations were not detected in the absence of drug exposure in keeping with sites of high constraint. Viral polymorphisms caused by immune selection and/or associated with non-subtype B might alter the genetic barrier to some non-primary resistance-associated mutations.

Tenascin-C downregulates wnt inhibitor dickkopf-1, promoting tumorigenesis in a neuroendocrine tumor model

The extracellular matrix molecule tenascin-C (TNC) is a major component of the cancer-specific matrix, and high TNC expression is linked to poor prognosis in several cancers. To provide a comprehensive understanding of TNC's functions in cancer, we established an immune-competent transgenic mouse model of pancreatic β-cell carcinogenesis with varying levels of TNC expression and compared stochastic neuroendocrine tumor formation in abundance or absence of TNC. We show that TNC promotes tumor cell survival, the angiogenic switch, more and leaky vessels, carcinoma progression, and lung micrometastasis. TNC downregulates Dickkopf-1 (DKK1) promoter activity through the blocking of actin stress fiber formation, activates Wnt signaling, and induces Wnt target genes in tumor and endothelial cells. Our results implicate DKK1 downregulation as an important mechanism underlying TNC-enhanced tumor progression through the provision of a proangiogenic tumor microenvironment.

Immunochemical interactions of peptides with site-directed polyclonal immunoglobulin G

The objective of this study was to investigate the immunochemical nature of the polyclonal immune response to the 14mer peptide TINKEDDESPGLYG and to identify interactions among antibodies to more than one epitope. Two groups of rabbits were immunized with the 14mer peptide and a Keyhole Limpet hemocyanin (KLH) carrier, but with KLH attached either to the 14mer's N- or C-terminus. Two approximate epitopes were mapped by an antibody-capture enzyme-linked immunosorbent assay method using antiserum obtained when KLH was oriented on the C-terminus of the 14mer. A precise mapping of the epitopes performed with inhibition enzyme immunoassays (iEIAs) resulted in an N-terminal 6mer epitope TINKED and a C-terminal 10mer epitope EDDESPGLYG. The epitopes overlapped by two amino acids. IEIAs and iEIAs incorporating antibody-blocking peptides indicated that the two anti-epitope antibody fractions did not interfere with one anothers' epitope binding. It was postulated that the anti-TINKED and anti-EDDESPGLYG antibody fractions individually bind their respective hydrophobic epitope "core" region at the N- or C-terminal of peptide TINKEDDESPGLYG, while sharing the two hydrophilic overlap amino acids. This antibody "lap joint" binding interaction can be accomplished by each of the anti-epitope antibodies binding an opposite side of the epitope overlap region in the shallow periphery of its binding site. ^

Interaction of small molecules with specific immune receptors: the p-i concept and its consequences

Drugs may stimulate the immune system by forming stable new antigenic complexes consisting of the drug or drug metabolite which is covalently bound to a protein or peptide (hapten-carrier complex). Both, B- and T-cell immunity may arise, the latter directed to hapten modified peptides presented by HLA molecules. Beside this immunological stimulation, drugs can also stimulate the immune system through binding by non-covalent bonds to proteins like immune receptors. This so-called “pharmacological interaction with immune receptors” concept (“p-i concept”) may occur with HLA or TCR molecules themselves (p-i HLA or p-i TCR), and not the immunogenic peptide. It is a type of “off-target” activity of the drug on immune receptors, but more complex as various cell types, cell interactions and functionally different T cells are involved. In this review the conditions which lead to activation of T cells by p-i are discussed: important factors for a functional consequence of drug binding is the location of binding (p-i HLA or p-i TCR); the exact site within these immune receptors; the affinity of binding and the finding that p-i HLA can stimulate the immune system like an allo-allele. The p-i concept is able to solve some puzzles of drug hypersensitivity reactions and are a basis to better treat and potentially avoid drug hypersensitivity reactions. Moreover, the p-i concept shows that in contrast to previous beliefs small molecules do interact with immune receptors with functional consequence. But these interactions are not based on “immune recognition”, are at odds with some immunological concepts, but may nevertheless open new possibilities to understand and even treat immune reactions

Thromboxane A2 acts as tonic immunoregulator by preferential disruption of low-avidity CD4+ T cell-dendritic cell interactions

Interactions between dendritic cells (DCs) and T cells control the decision between activation and tolerance induction. Thromboxane A2 (TXA2) and its receptor TP have been suggested to regulate adaptive immune responses through control of T cell-DC interactions. Here, we show that this control is achieved by selectively reducing expansion of low-avidity CD4(+) T cells. During inflammation, weak tetramer-binding TP-deficient CD4(+) T cells were preferentially expanded compared with TP-proficient CD4(+) T cells. Using intravital imaging of cellular interactions in reactive peripheral lymph nodes (PLNs), we found that TXA2 led to disruption of low- but not high-avidity interactions between DCs and CD4(+) T cells. Lack of TP correlated with higher expression of activation markers on stimulated CD4(+) T cells and with augmented accumulation of follicular helper T cells (TFH), which correlated with increased low-avidity IgG responses. In sum, our data suggest that tonic suppression of weak CD4(+) T cell-DC interactions by TXA2-TP signaling improves the overall quality of adaptive immune responses.

Current concepts: host-pathogen interactions in cystic fibrosis airways disease.

Chronic infection and inflammation are defining characteristics of cystic fibrosis (CF) airway disease. Conditions within the airways of patients living with CF are conducive to colonisation by a variety of opportunistic bacterial, viral and fungal pathogens. Improved molecular identification of microorganisms has begun to emphasise the polymicrobial nature of infections in the CF airway microenvironment. Changes to CF airway physiology through loss of cystic fibrosis transmembrane conductance regulator functionality result in a wide range of immune dysfunctions, which permit pathogen colonisation and persistence. This review will summarise the current understanding of how CF pathogens infect, interact with and evade the CF host.

Immune-Deficient Drosophila melanogaster: A Model for the Innate Immune Response to Human Fungal Pathogens

We explored the host-pathogen interactions of the human opportunistic fungus Candida albicans using Drosophila melanogaster. We established that a Drosophila strain devoid of functional Toll receptor is highly susceptible to the human pathogen C. albicans. Using this sensitive strain, we have been able to show that a set of specific C. albicans mutants of different virulence in mammalian infection models are also impaired in virulence in Drosophila and remarkably display the same rank order of virulence. This immunodeficient insect model also revealed virulence properties undetected in an immunocompetent murine model of infection. The genetic systems available in both host and pathogen will enable the identification of host-specific components and C. albicans genes involved in the host-fungal interplay.

T Cell Motility as Modulator of Interactions with Dendritic Cells

It is well established that the balance of costimulatory and inhibitory signals during interactions with dendritic cells (DCs) determines T cell transition from a naïve to an activated or tolerant/anergic status. Although many of these molecular interactions are well reproduced in reductionist in vitro assays, the highly dynamic motility of naïve T cells in lymphoid tissue acts as an additional lever to fine-tune their activation threshold. T cell detachment from DCs providing suboptimal stimulation allows them to search for DCs with higher levels of stimulatory signals, while storing a transient memory of short encounters. In turn, adhesion of weakly reactive T cells to DCs presenting peptides presented on major histocompatibility complex with low affinity is prevented by lipid mediators. Finally, controlled recruitment of CD8(+) T cells to cognate DC-CD4(+) T cell clusters shapes memory T cell formation and the quality of the immune response. Dynamic physiological lymphocyte motility therefore constitutes a mechanism to mitigate low avidity T cell activation and to improve the search for "optimal" DCs, while contributing to peripheral tolerance induction in the absence of inflammation.

Neutrophils: Between host defence, immune modulation, and tissue injury.

Neutrophils, the most abundant human immune cells, are rapidly recruited to sites of infection, where they fulfill their life-saving antimicrobial functions. While traditionally regarded as short-lived phagocytes, recent findings on long-term survival, neutrophil extracellular trap (NET) formation, heterogeneity and plasticity, suppressive functions, and tissue injury have expanded our understanding of their diverse role in infection and inflammation. This review summarises our current understanding of neutrophils in host-pathogen interactions and disease involvement, illustrating the versatility and plasticity of the neutrophil, moving between host defence, immune modulation, and tissue damage.

Drug Hypersensitivity: How Drugs Stimulate T Cells via Pharmacological Interaction with Immune Receptors.

Small chemicals like drugs tend to bind to proteins via noncovalent bonds, e.g. hydrogen bonds, salt bridges or electrostatic interactions. Some chemicals interact with other molecules than the actual target ligand, representing so-called 'off-target' activities of drugs. Such interactions are a main cause of adverse side effects to drugs and are normally classified as predictable type A reactions. Detailed analysis of drug-induced immune reactions revealed that off-target activities also affect immune receptors, such as highly polymorphic human leukocyte antigens (HLA) or T cell receptors (TCR). Such drug interactions with immune receptors may lead to T cell stimulation, resulting in clinical symptoms of delayed-type hypersensitivity. They are assigned the 'pharmacological interaction with immune receptors' (p-i) concept. Analysis of p-i has revealed that drugs bind preferentially or exclusively to distinct HLA molecules (p-i HLA) or to distinct TCR (p-i TCR). P-i reactions differ from 'conventional' off-target drug reactions as the outcome is not due to the effect on the drug-modified cells themselves, but is the consequence of reactive T cells. Hence, the complex and diverse clinical manifestations of delayed-type hypersensitivity are caused by the functional heterogeneity of T cells. In the abacavir model of p-i HLA, the drug binding to HLA may result in alteration of the presenting peptides. More importantly, the drug binding to HLA generates a drug-modified HLA, which stimulates T cells directly, like an allo-HLA. In the sulfamethoxazole model of p-i TCR, responsive T cells likely require costimulation for full T cell activation. These findings may explain the similarity of delayed-type hypersensitivity reactions to graft-versus-host disease, and how systemic viral infections increase the risk of delayed-type hypersensitivity reactions.

Neuroimmune Interactions: a Bidirectional Flow that Leads to Health and Disease

The Vedic philosophy deals with harmony and balance between the mind and the body as well as interactions with nature. This ancient approach to health and well-being is being more and more appreciated in part as we understand the intimate relationship between the immune system, our major defense mechanism and the nervous system. Like other organ systems, the immune system is dependent on the central nervous system (CNS) and the endocrine system in its role for effective defense against foreign and domestic invaders.

Characterization of humoral immune responses against Treponema pallidum antigens

The spirochete Treponema pallidum subsp. pallidum is the causative agent of syphilis, a sexually transmitted disease with an estimated 12 million new cases per year worldwide. There is no vaccine currently available for the prevention of syphilis. In the present study, the T. pallidum hypothetical protein TP0693 was examined to determine its cellular location, and its potential for use as a vaccine candidate and immunodiagnostic for syphilis. TP0693 was demonstrated to be strongly reactive with sera from rabbits infected experimentally with T. pallidum for >25 days. Results from proteinase K digestion, immunofluorescence and immunoelectron microscopy were consistent with outer surface localization of TP0693. Serum reactivity against TP0693 was detected in only 68% of syphilis patients, which does not support its use as an immunodiagnostic for syphilis. Immunization of rabbits with TP0693 or three other outer membrane candidates did not alter the course of lesion development atter T. pallidum inoculation. We also examined the T. pallidum proteome by two-dimensional gel electrophoresis coupled with mass spectrometry analysis and immunoblotting. This approach resulted in the identification of 95 unique polypeptides, several of which were reactive with sera from infected rabbits and syphilis patients. The analyses described here enabled us to identify antigens potentially useful as vaccine candidates or diagnostic markers, and may provide insight into host-pathogen interactions during T. pallidum infection. ^

Characterization of the interactions between fibronectin and the Borrelia burgdorferi lipoprotein, BBK32

The findings presented in this dissertation detail the complex interaction between BBK32 and fibronectin and describe novel consequences of the interaction. BBK32 is a fibronectin-binding protein on Borrelia burgdorferi, the causative agent of Lyme disease. We found that BBK32 contains multiple fibronectin-binding motifs, recognizing the fibronectin N-terminal domain (NTD) and the gelatin binding domain (GBD) in an anti-parallel order, where corresponding sites in BBK32 and fibronectin are aligned so that there is a one-to-one interaction between the proteins. While characterizing this interaction, we discovered that binding of BBK32 to the GBD inhibits the migration stimulating factor's (MSF) motogenic activity. In the presence of BBK32, endothelial cells do not migrate in response to increasing concentrations of MSF or the GBD. MSF is found under wound healing conditions, and inhibition of its activity may allow the tick-transmitted spirochetes to delay wound healing and to establish an infection. ^ Biophysical structural studies, designed to identify a mechanism of interaction, revealed that BBK32 binding to the NTD leads to the unfolding of plasma fibronectin, which exposes α5β1 integrin recognition motifs. Binding assays demonstrate that the BBK32-NTD interaction enhances the plasma fibronectin-α5β1 integrin interaction, which may allow B. burgdorferi to invade host cells, and thereby evade the host immune system. ^ We also determined that BBK32 binds fibronectin F3 modules, which leads to plasma fibronectin aggregation and induction of superfibronectin. The resulting superfibronectin is conformationally distinct from plasma and cellular fibronectin, and can inhibit endothelial cell proliferation. BBK32's active superfibronectin-forming motif has been located to a region between residues 160 and 175, which contains two sequence motifs that are also found in anastellin, the only other known superfibronectin-inducing protein. ^ A potential consequence of BBK32-induced superfibronectin formation was identified. BBK32-induced superfibronectin formation results in the exposure of α4β1 integrin recognition sequences in fibronectin. The α4β1 integrin is required for leukocyte transendothelial cell migration. BBK32-induced superfibronectin inhibits this activity. The inhibition of leukocyte recruitment to the infection site may slow the activity of the host immune system, and permit the spirochetes to establish an infection. ^