P. Whitaker

Mass Spectrometric Characterization of Circulating and Functional Antigens Derived from Piperacillin in Patients with Cystic Fibrosis

A mechanistic understanding of the relationship between the chemistry of drug Ag formation and immune function is lacking. Thus, mass spectrometric methods were employed to detect and fully characterize circulating Ags derived from piperacillin in patients undergoing therapy and the nature of the drug-derived epitopes on protein that can function as an Ag to stimulate T cells. Albumin modification with piperacillin in vitro resulted in the formation of two distinct haptens, one formed directly from piperacillin and a second in which the dioxopiperazine ring had undergone hydrolysis. Modification was time and concentration dependent, with selective modification of Lys541 observed at low concentrations, whereas at higher concentrations, up to 13 out of 59 lysine residues were modified, four of which (Lys190, Lys195, Lys432, and Lys541) were detected in patients’ plasma. Piperacillin-specific T lymphocyte responses (proliferation, cytokines, and granzyme B release) were detected ex vivo with cells from hypersensitive patients, and analysis of incubation medium showed that modification of the same lysine residues in albumin occurred in situ. The antigenicity of piperacillin-modified albumin was confirmed by stimulation of T cells with characterized synthetic conjugates. Analysis of minimally modified T cell-stimulatory albumin conjugates revealed peptide sequences incorporating Lys190, Lys432, and Lys541 as principal functional epitopes for T cells. This study has characterized the multiple haptenic structures on albumin in patients and showed that they constitute functional antigenic determinants for T cells.

Characterization of the antigen specificity of T-cell clones from piperacillin hypersensitive patients with cystic fibrosis

β-Lactam antibiotics provide the cornerstone of treatment and reduce the rate of decline in lung function in patients with cystic fibrosis, but their use is limited by a high frequency of delayed-type allergic reactions. The objective of this study was to use cloned T-cells expressing a single T-cell receptor from five piperacillin-hypersensitive patients to characterize both the cellular pathophysiology of the reaction and antigen specificity to define the mechanism of activation of T-cells by piperacillin. More than 400 piperacillin-responsive CD4+, CD4+CD8+, or CD8+ T-cell clones were generated from lymphocyte transformation test and ELIspot-positive patients. The T-cell response (proliferation, T helper 2 cytokine secretion, and cytotoxicity) to piperacillin was concentration-dependent and highly specific. Enzyme-linked immunosorbent assay, gel electrophoresis, and mass spectrometry revealed that piperacillin bound exclusively to albumin in T-cell culture. Irreversible piperacillin binding at Lys 190, 195, 199, 432, and 541 on albumin and the stimulation of T-cells depended on incubation time. A synthetic piperacillin albumin conjugate stimulated T-cell receptors via a major histocompatibility complex- and processing-dependent pathway. Flucloxacillin competes for the same Lys residues on albumin as piperacillin, but the resulting conjugate does not stimulate T-cells, indicating that binding of the β-lactam hapten in peptide conjugates confers structural specificity on the activation of the T-cell receptors expressed on drug-specific clones. Collectively, these data describe the cellular processes that underlie the structural specificity of piperacillin antigen binding in hypersensitive patients with cystic fibrosis.

The role of respiratory viruses in adult patients with cystic fibrosis receiving intravenous antibiotics for a pulmonary exacerbation

BACKGROUND Respiratory viruses have become increasingly recognised as important agents in pulmonary exacerbations in infants and children with CF. The aim of this study was to determine the prevalence of respiratory viruses during acute pulmonary exacerbations in adults and compare the severity of these exacerbations with non-viral associated exacerbations. METHODS This was a retrospective case control study. Viral throat swabs were taken from all patients presenting with an acute pulmonary exacerbation requiring intravenous antibiotic treatment over a 12 month period. RESULTS There were 432 pulmonary exacerbations in 180 adults. A positive viral PCR in 42 exacerbations indicated a prevalence of 9.7%. The commonest virus isolated was rhinovirus (n = 29, 69%) with influenza A/H1N1 in seven patients (16.7%). Exacerbations associated with a positive viral PCR had a greater fall in lung function at presentation with higher levels of inflammatory markers. They received more days of intravenous antibiotics, showed less response to treatment and had a shorter time to next pulmonary exacerbation compared to matched controls. CONCLUSION Viral associated pulmonary exacerbations in adults with CF are associated with more severe pulmonary involvement and respond less well to standard treatment.

Rapid desensitization for non-immediate reactions in patients with cystic fibrosis

Non-immediate hypersensitivity reactions to antibiotics in patients with CF represent a real-life challenge for clinicians. Desensitization is often performed in patients who have exhausted all therapeutic options. Whilst desensitization is an established procedure for immediate reactions we assessed the outcomes and safety of desensitization for non-immediate reactions. We retrospectively reviewed 275 desensitization procedures in 42 patients with a range of non-immediate reactions to six commonly used antibiotics. Desensitization was performed using a 7-step rapid intravenous protocol on a normal medical ward. 250 (91%) of overall desensitization procedures were successful; however, this figure incorporates certain individuals having multiple successful procedures. Individual patient success ranged from 55% with tazocin through to 88% with tobramycin. In the 25 patients who failed desensitization the reactions were mild and the majority occurred within 48 h of starting treatment. Prophylactic anti-histamines and steroids did not reduce the risk of reaction. Whilst the mechanisms remain uncertain we can confirm that rapid desensitization is a safe and effective way of re-introducing an antibiotic to a patient with a non-immediate reaction.

β-Lactam antibiotics form distinct haptenic structures on albumin and activate drug-specific T-lymphocyte responses in multiallergic patients with cystic fibrosis.

β-Lactam antibiotics provide the cornerstone of treatment for respiratory exacerbations in patients with cystic fibrosis. Unfortunately, approximately 20% of patients develop multiple nonimmediate allergic reactions that restrict therapeutic options. The purpose of this study was to explore the chemical and immunological basis of multiple β-lactam allergy through the analysis of human serum albumin (HSA) covalent binding profiles and T-cell responses against 3 commonly prescribed drugs; piperacillin, meropenem, and aztreonam. The chemical structures of the drug haptens were defined by mass spectrometry. Peripheral blood mononuclear cells (PBMC) were isolated from 4 patients with multiple allergic reactions and cultured with piperacillin, meropenem, and aztreonam. PBMC responses were characterized using the lymphocyte transformation test and IFN-γ /IL-13 ELIspot. T-cell clones were generated from drug-stimulated T-cell lines and characterized in terms of phenotype, function, and cross-reactivity. Piperacillin, meropenem, and aztreonam formed complex and structurally distinct haptenic structures with lysine residues on HSA. Each drug modified Lys190 and at least 6 additional lysine residues in a time- and concentration-dependent manner. PBMC proliferative responses and cytokine release were detected with cells from the allergic patients, but not tolerant controls, following exposure to the drugs. 122 CD4+, CD8+, or CD4+CD8+ T-cell clones isolated from the allergic patients were found to proliferate and release cytokines following stimulation with piperacillin, meropenem, or aztreonam. Cross-reactivity with the different drugs was not observed. In conclusion, our data show that piperacillin-, meropenem-, and aztreonam-specific T-cell responses are readily detectable in allergic patients with cystic fibrosis, which indicates that multiple β-lactam allergies are instigated through priming of naïve T-cells against the different drug antigens. Characterization of complex haptenic structures on distinct HSA lysine residues provides a chemical basis for the drug-specific T-cell response.

Negative Regulation by PD-L1 during Drug-Specific Priming of IL-22–Secreting T Cells and the Influence of PD-1 on Effector T Cell Function

Activation of PD-1 on T cells is thought to inhibit Ag-specific T cell priming and regulate T cell differentiation. Thus, we sought to measure the drug-specific activation of naive T cells after perturbation of PD-L1/2/PD-1 binding and investigate whether PD-1 signaling influences the differentiation of T cells. Priming of naive CD4+ and CD8+ T cells against drug Ags was found to be more effective when PD-L1 signaling was blocked. Upon restimulation, T cells proliferated more vigorously and secreted increased levels of IFN-γ, IL-13, and IL-22 but not IL-17. Naive T cells expressed low levels of PD-1; however, a transient increase in PD-1 expression was observed during drug-specific T cell priming. Next, drug-specific responses from in vitro primed T cell clones and clones from hypersensitive patients were measured and correlated with PD-1 expression. All clones were found to secrete IFN-γ, IL-5, and IL-13. More detailed analysis revealed two different cytokine signatures. Clones secreted either FasL/IL-22 or granzyme B. The FasL/IL-22–secreting clones expressed the skin-homing receptors CCR4, CCR10, and CLA and migrated in response to CCL17/CCL27. PD-1 was stably expressed at different levels on clones; however, PD-1 expression did not correlate with the strength of the Ag-specific proliferative response or the secretion of cytokines/cytolytic molecules. This study shows that PD-L1/PD-1 binding negatively regulates the priming of drug-specific T cells. ELISPOT analysis uncovered an Ag-specific FasL/IL-22–secreting T cell subset with skin-homing properties.

Drug Metabolite-Specific Lymphocyte Responses in Sulfamethoxazole Allergic Patients with Cystic Fibrosis

Sulfamethoxazole (SMX) is an important antibiotic in the management of patients with cystic fibrosis, but allergic reactions may develop thus restricting therapy. The aim of this study was to utilize drug (metabolite) antigens to diagnose SMX-mediated allergic reactions in patients with cystic fibrosis. Lymphocytes from 2/12 allergic patients were stimulated to proliferate strongly with the SMX metabolite nitroso SMX (SMX-NO). In contrast, responses to SMX were weak. The introduction of an antigen-driven T-cell enrichment step prior to the analysis of proliferation increased the sensitivity of the assay. SMX-NO responses were detected with lymphocytes from all patients with cutaneous signs.

Auto-oxidation of Isoniazid Leads to Isonicotinic-Lysine Adducts on Human Serum Albumin.

Isoniazid (INH), a widely used antituberculosis drug, has been associated with serious drug-induced liver injury (DILI). INH-modified proteins have been proposed to play important roles in INH DILI; however, it remains to be determined whether INH or reactive metabolites bind irreversibly to proteins. In this study, mass spectrometry was used to define protein modifications by INH in vitro and in patients taking INH therapy. When INH was incubated with N-acetyl lysine (NAL), the same isonicotinic-NAL (IN-NAL) adducts were detected irrespective of the presence or absence of any oxidative enzymes, indicating auto-oxidation may have been involved. In addition, we found that INH could also bind to human serum albumin (HSA) via an auto-oxidation pathway, forming isonicotinic amide adducts with lysine residues in HSA. Similar adducts were detected in plasma samples isolated from patients taking INH therapy. Our results show that INH forms protein adducts in the absence of metabolism.

Nonimmediate β-lactam reactions in patients with cystic fibrosis.

Purpose of reviewThe aim of this review is to present and discuss new developments regarding &bgr;-lactam hypersensitivity in patients with cystic fibrosis. It is a common complication that can have significant implications for a patient. Up to 30% of patients have had multiple &bgr;-lactam reactions. Recent findingsFor the first time drug-specific lymphocytes have been identified in patients with cystic fibrosis. This supports the clinical viewpoint that the nonimmediate reactions seen are T-cell mediated. Furthermore, in piperacillin hypersensitivity mass spectrometric methods have been used to characterise hapten formation both in vivo and in vitro. The synthetic piperacillin–albumin conjugate is able to stimulate patients’ lymphocytes and T cell clones. Lymphocyte proliferation was not seen with ceftazidime; this may be due to undetectable protein reactivity in vitro. Skin testing was not sensitive in this cohort and many patients have uncertain allergy status. Desensitisation is performed with some success; however, at present it is not known whether any immune modulation takes place. SummaryThe piperacillin model provides us with a useful tool to characterise the mechanisms of drug hypersensitivity. Prospective studies are needed to assess how drug sensitivity develops and whether clinical practice could be modified to reduce the risk.

The development and deployment of integrated electronic care records in a regional adult and paediatric cystic fibrosis unit

BACKGROUND Electronic care records (ECRs) for cystic fibrosis (CF) provide a basis for accurate, reliable capture of clinical measures and interventions, and epidemiological trends, providing the basis for improved efficiency and patient safety. METHODS A primary care system was modified for hospital use and clinical codes devised for all aspects of CF care. Performance and usability were assessed. RESULTS Of a total of 620 patients 619 consented to their data being recorded in the system. Five hundred and twenty three new codes were created and embedded behind 60 new templates. Following introduction of ECR, completion of annual assessments increased from 43% to 92%, retrieval of drug costs rose significantly and time to correspondence with primary care fell from 34days to <2days. Staff satisfaction was high. CONCLUSION The system is fully operational allowing the unit to function as a paperless service. Efficiencies of staffing activity, process management and cost retrievals are evident. Sharing of coding structures is important in future care.