Determination of emergency nurse practitioner and plastic surgery trainee disposition decision agreement for plastic surgery emergency department presentations: A prospective study

OBJECTIVE

To examine if there was a high degree of agreement for disposition decisions of emergency nurse practitioners (ENP) compared to plastic surgery trainees (PST) for plastic surgery presentations.

METHODS

A prospective study of disposition decision agreement from February 2020 to January 2021 for patients who required plastic surgery consultation and managed exclusively by an ENP. Absolute percentages were used to determine the exact disposition decision accuracy of ENP and the PST, while Cohen's kappa compared disposition decision agreement. Sub-analyses of age, gender, ENP experience and presenting condition agreement were also completed. To mitigate confounding factors, operative management (OM) and non-OM groups were analysed.

RESULTS

The study recruited 342 patients who presented mostly with finger or hand-related conditions (82%, n = 279) and managed by an ENP with less than 10 years of experience (65%, n = 224). Disposition decisions by ENP compared to PST were the same in 80% (n = 274) of cases. Disposition agreement for all patients was 0.72 (95% confidence interval 0.66-0.78). For the OM and non-OM groups, disposition decisions were the same in 94% (n = 320), with a Cohen's kappa 0.85 (95% confidence interval 0.79-0.91). Seven patients (2%) were discharged to GP care by the ENP when determined to need further plastic surgery involvement by the PST.

CONCLUSIONS

Disposition decisions by ENP and PST were the same in most cases and had a high overall level of agreement. This may lead to greater autonomy of ENP care and reduced ED length of stay and occupancy.

Documentation of paediatric head injuries in a mixed metropolitan emergency department

OBJECTIVE

Head injuries are a common presentation of children to Australian EDs. Healthcare documentation is an important tool for enhancing patient care. In our study, we aimed to assess the adequacy of paediatric head injury documentation in a mixed ED.

METHODS

A retrospective analysis of presentations to a mixed ED between 2017 and 2018. Children aged <16 years old with a primary diagnosis of head injury were included. Documentation items based on local head injury guidelines were assessed in both medical and nursing documentation. We compared cases aged <1 and ≥1 year.

RESULTS

There were 427 presentations that met the case definition. Medical documentation was present in 422 cases and nursing documentation in 310 cases. In combined medical and nursing documentation, items poorly documented include blood pressure (BP; 21.3%) and secondary survey (16.9%). In solely medical documentation, least commonly documented items are high-risk bony injuries (22.5%), high-risk soft tissue injuries (22.3%), seizure (22.0%) and non-accidental injury (3.6%). Glasgow Coma Scale (GCS) was poorly documented in cases aged <1 year (10.9%, P < 0.001).

CONCLUSIONS

The largest gaps in the documentation of paediatric head injuries were BP and paediatric GCS in infants. Future audits and educational strategies should focus on targeting clinically relevant items that are predictive of serious outcomes.

Defying Occam's Razor: A Case of Pulmonary Embolism Masked By Cardiac Tamponade

BACKGROUND

Occam's razor instructs physicians to assume one single cause for multiple symptoms, whereas Hickam's dictum encourages them to suspect multiple concurrent pathologies. Although the general practice is to follow Occam's razor, occasionally Hickam's dictum reigns supreme. Here we present one such case, where the concurrent presence of two life-threatening pathologies posed clinical challenges in diagnosis and management.

CASE REPORT

Although cardiac tamponade and pulmonary embolism (PE) are known complications of malignancy, their concomitant existence is rare. Here we report a patient who presented with shortness of breath found to have both cardiac tamponade and submassive PE. Although the cardiac tamponade was initially diagnosed in the Emergency Department by bedside ultrasound and treated with pericardiocentesis, only a few hours later, when she deteriorated, the submassive PE was diagnosed, which was treated with heparin infusion and subsequently transitioned to a newer oral anticoagulant. The patient was later diagnosed as having primary breast cancer and metastatic lung adenocarcinoma. Why Should an Emergency Physician Be Aware of This? This raised unique diagnostic challenges, as both cardiac tamponade and PE present with obstructive shock. The increased right heart pressure from the PE could have paradoxically protected the patient from the tamponade effects of the pericardial effusion. Furthermore, the presence of cardiac tamponade may also mask the typical echocardiographic features of PE. The concurrent presence of two pathologies raised challenges and dilemmas in management. This case shows that physicians should maintain a high degree of suspicion of two pathologies when the patient deteriorates after the first pathology has been appropriately treated.

Preparedness of Australasian emergency departments for point-of-care ultrasound in the COVID-19 pandemic

Introduction

Point-of-care ultrasound (POCUS) has been brought to the limelight again, with a surge in lung ultrasound in suspected COVID-19 patients. This is due to POCUS superiority over chest X-ray, equivalent efficacy to computerised tomography chest for COVID-19 diagnosis and potential minimisation of cross-infection. However, inadequate disinfection practices could make ultrasound machines a vector for disease transmission. This study, conducted during the early phase of the COVID-19 pandemic, surveyed the preparedness of Australasian Clinicians for responsible POCUS practice within the Emergency Department (ED).

Methods

An anonymous online survey conducted from 20th April to 3rd June 2020 among emergency clinicians providing POCUS within Australasian EDs investigated preparedness to provide effective POCUS while minimising cross-infection.

Results

The survey received 171 responses and 116 being eligible for analysis. Most respondents (n = 96, 98%) had a separate 'hot zone' with a dedicated US device (n = 75, 77%), but lacked COVID-19-specific standard-operating procedures (n = 51, 52%) or a designated safety and compliance officer (n = 36, 37%). Most clinicians (n = 86, 88%) were willing to perform ultrasound in highly infectious patients, despite poor formal training (n = 66, 67%) or COVID-19-specific lung protocols (n = 59, 60%). Most (n = 92, 93%) had access to appropriate low-level disinfectant wipes but varied significantly in disinfection practice due to a lack of timely, formal or unified guidelines.

Conclusion

Australasian EDs significantly lacked investment in education, training and protocols to conduct safe POCUS in the COVID-19 pandemic. A framework with evidence-based, logistically feasible protocols supporting safe emergency POCUS is required to deal with similar future infectious outbreaks.

Australasian emergency ultrasound: A survey on the current status

OBJECTIVE

Emergency ultrasound (EUS) has become an integral part of emergency medicine, and the core pillars of governance, infrastructure, administration, education and quality assurance (QA) are vital for its quality and continued growth. We aimed to assess the status of these vital pillars among Australasian EDs.

METHODS

A survey among the clinical leads in ultrasound (CLUS) in Australasian EDs from November 2020 to April 2021.

RESULTS

We analysed a total of 98 responses from CLUS representing 98 EDs. Most CLUS (85%) held EUS qualifications (CCPU 57%, DDU 18%, other 9%) but 15% had none. Only 66% of CLUS had dedicated clinical support time, and a mere 5% had administrative personnel support. Up to three ultrasound machines in 62% of EDs, but only 26% of EDs had secured image archiving facilities. In-house credentialing and the Australasian College for Emergency Medicine (ACEM) trainee special skills placement were available in 50% and 32% of EDs, respectively. Only 11% of EDs had regular EUS training for FACEMs, and only 66% of EDs had regular EUS education for emergency medicine trainees. Only 20 EDs had sonographer educators. Regarding EUS QA, only 33% of EDs provided formal EUS report, 23% of EDs conducted regular image reviews and 37% of EDs audited EUS performance. Only 35% of EDs had high-level disinfection equipment, and 56% of EDs had formal transducer disinfection protocols.

CONCLUSION

Despite ACEM recommendations for the practice of EUS, Australasian EDs still lack vital governance, administrative support, infrastructure, education and QA processes. Prompt actions such as ACEM mandating these recommendations are required to improve resource allocation by health services.

Echocardiography does not prolong peri-shock pause in cardiopulmonary resuscitation using the COACH-RED protocol with non-expert sonographers in simulated cardiac arrest

OBJECTIVE

Focused echocardiography during peri-shock pause (PSP) can prognosticate and detect reversible causes in cardiac arrest but minimising interruptions to chest compressions improves outcome. The COACH-RED protocol was adapted from the COACHED protocol to systematically incorporate echocardiography into rhythm check without prolonging PSP beyond the recommended 10 s. The primary objective of this study was to test the feasibility of emergency nurses learning to perform all roles in the COACH-RED protocol. PSP duration and change in participant confidence were secondary outcomes.

METHODS

After an initial two-hour workshop, five ALS-trained nurses were assessed for the correct use of COACH-RED protocol, without critical error, in three simulated cardiac arrest scenarios of four cycles each. Assessments were repeated on days 7 and 35. On day 35, three COACHED scenarios were also assessed for comparison. Participant roles per scenario and cardiac rhythm per cycle were randomised. Participants completed questionnaires on their confidence levels. Sessions were videotaped for accurate measurement of PSP duration and results tabulated for simple comparison. Statistical analysis was not performed due to small sample size.

RESULTS

There were no critical errors, two minor team-leading errors and two minor echosonography errors. Minor errors occurred in separate scenarios resulting in a 100% pass rate overall by predetermined criteria. Echocardiographic recordings were 100% adequate. Overall median PSP was 9.35 s for COACH-RED and 6.94 s for COACHED. Sub-group analysis of COACH-RED revealed median PSP 10.80 s in shockable rhythms and 8.74 s (∼2 s less) in non-shockable rhythms. Mean participant confidence in performing COACH-RED improved from 1.6 to 4.6, on a 5-point scale.

CONCLUSION

The COACH-RED protocol can be effectively performed by ALS-trained nurses, in all roles of this protocol, including echocardiography, in a simulated environment, after a single training session. Using this protocol, focused echocardiography does not prolong PSP beyond 10 s.

CLUE: COVID-19 lung ultrasound in emergency department

Lung ultrasound (LUS) plays a critical role in the SARS‐CoV‐2 pandemic. Evidence is mounting on its utility to diagnose, assess the severity and as a triage tool in the ED. Sonographic features correlate well to computed tomography (CT) chest findings and a bedside LUS performed by a trained clinician along with clinical examination, could be an alternative to chest X‐ray and CT chest in these highly infectious patients. In this article, we have described a step‐by‐step approach to LUS in COVID patients and the CLUE (COVID‐19 LUS in the ED) protocol, which involves an anatomical parameter, the severity of lung changes, objectively scored using the validated LUS scoring system and a physiological parameter, oxygen requirement. We believe this CLUE protocol can help risk‐stratify patients presenting to ED with suspected COVID‐19 and aid clinicians in making appropriate disposition decisions.

COACHRED: A protocol for the safe and timely incorporation of focused echocardiography into the rhythm check during cardiopulmonary resuscitation

Focused echocardiography may be a useful tool in cardiopulmonary resuscitation for prognostication, to identify certain reversible causes of cardiac arrest, and to guide further management and procedures. Nonetheless, many clinicians have reservations regarding its widespread adoption due to evidence that it leads to prolonged interruption of cardiac compressions. Furthermore, the lack of a clear protocol for the inclusion of focused echocardiography into the rhythm check can lead to confusion in teams not familiar with incorporating the modality, as well as safety concerns for the echosonographer during delivery of a shock. We propose the protocol COACHRED to guide the use of focused echocardiography during rhythm check in a safe and timely manner. This approach incorporates the best strategies identified to date that minimise interruptions to chest compressions. We demonstrate that, in a simulation environment, it is achievable to incorporate focused echocardiography into the rhythm check while keeping the interruption to chest compressions within the timeframe prescribed by international guidelines.

Maturation of an antibody response is governed by modulations in flexibility of the antigen-combining site

Although affinity maturation constitutes an integral part of T-dependent humoral responses, its structural basis is less well understood. We compared the physicochemical properties of antigen binding of several independent antibody panels derived from both germline and secondary responses. We found that antibody maturation essentially reflects modulations in entropy-control of the association, but not dissociation, step of the binding. This influence stems from variations in conformational heterogeneity of the antigen-combining site, which in turn regulates both the affinity and specificity for antigen. Thus, the simple device of manipulating conformational flexibility of paratope provides a mechanism wherein the transition from a degenerate recognition capability to a high-fidelity effector response is readily achieved, with the minimum of somatic mutations.

B cell responses to a peptide epitope. IX. The kinetics of antigen binding differentially regulates costimulatory capacity of activated B cells

We explore the possible mechanism by which association rates of Ag with activated B cells influences the ability of the latter to selectively recruit Th subsets. Our system used cocultures of Ag-activated B and T cells, where the Ag was a synthetic peptide, G41CT3. Restimulation was with either peptide G41CT3 or its analogue, G28CT3. Peptide G28CT3 has been previously shown to display a higher on rate, relative to the homologous peptide G41CT3, of binding to G41CT3-activated B cells. This difference in on rates was eventually exerted at the level of IFN-gamma, but not of IL-10, induction from T cells, with peptide G28CT3 proving more effective. However, various treatment regimens rendered peptide G41CT3 as potent as peptide G28CT3 at eliciting IFN-gamma responses from the above cultures. This included simultaneous treatment of B cells with peptide G41CT3 and the protein tyrosine kinase inhibitor tyrphostin. Alternatively, pretreatment of B cells with a peptide representing only the B cell epitope constituent of peptide G28CT3 (G28) was also equally effective. Subsequent experiments revealed that IFN-gamma production from activated T cells resulted from an engagement of CD28 by B7-1 on the B cell surface. Finally, the extent of cell surface B7-1 up-regulation on activated B cells was dependent on the on rate of Ag binding to the membrane-bound Ig receptor. Thus, cumulative results suggest that the kinetics of Ag binding to activated B cells can differentially regulate intracellular signaling. This influences selective costimulatory molecule expression, with its consequent effects on relative Th subset activation.

B cell responses to a peptide epitope. X. Epitope selection in a primary response is thermodynamically regulated

We examine the etiological basis of hierarchical immunodominance of B cell epitopes on a multideterminant Ag. A model T-dependent immunogen, containing a single immunodominant B cell epitope, was used. The primary IgM response to this peptide included Abs directed against diverse determinants presented by the peptide. Interestingly, affinity of individual monomeric IgM Abs segregated around epitope recognized and was independent of their clonal origins. Furthermore, affinity of Abs directed against the immunodominant epitope were markedly higher than that of the alternate specificities. These studies suggested that the affinity of an epitope-specific primary response, and variations therein, may be determined by the chemical composition of epitope. This inference was supported by thermodynamic analyses of monomer IgM binding to Ag, which revealed that this interaction occurs at the expense of unfavorable entropy changes. Permissible binding required compensation by net enthalpic changes. Finally, the correlation between chemical composition of an epitope, the resultant affinity of the early primary humoral response, and its eventual influence on relative immunogenicity could be experimentally verified. This was achieved by examining the effect of various amino-terminal substitutions on immunogenicity of a, hitherto cryptic, amino-terminal determinant. Such experiments permitted delineation of a hierarchy of individual amino acid residues based on their influence; which correlated well with calculated Gibbs-free energy changes that individual residue side chains were expected to contribute in a binding interaction. Thus, maturation of a T-dependent humoral response is initiated by a step that is under thermodynamic control.

B cell responses to a peptide epitope. VI. The kinetics of antigen recognition modulates B cell-mediated recruitment of T helper subsets

The ability of Ag-primed B cells to recruit distinct Th subsets was examined using two analogous synthetic peptides, G41CT3 and G28CT3, as model Ags. With sequence differences at only two positions, these peptides were identical both with respect to fine specificity of Abs induced and ability to prime T cells. Lymph node cell populations primed with peptide G41CT3, when challenged with the homologous Ag, yielded predominantly Th2 cytokines. In contrast, a challenge with the heterologous Ag, G28CT3, resulted in a markedly increased production of Th1 cytokines. These distinctions derived from altered APC function of Ag-primed B cells due to differential kinetics of recognition of the two Ags by surface Ig receptors, as confirmed by binding studies with a panel of anti-G41CT3 mAbs. A concentration-dependent circular dichroism study revealed differences in the nature of intermolecular associations for these two peptides. Furthermore, the on-rate of peptide G28CT3 binding to Ab also increased with increasing peptide concentration, implying a dependence on intermolecular interactions. This, in turn, correlated well with the ability of peptide G28CT3 to preferentially activate either Th1 or Th2 cells. Thus, the relative proportion of Th1 vs Th2 cells recruited by Ag-primed B cells is governed by the on-rate of Ag binding to surface Ig receptors, with higher on-rates promoting Th1 recruitment. Further, even subtle changes in solution behavior of an Ag can markedly influence the kinetics of recognition by B cells.

B cell responses to a peptide epitope. V. Kinetic regulation of repertoire discrimination and antibody optimization for epitope

The influence of imposing various conformational constraints on immune responses to a model epitope within a synthetic peptide immunogen was examined in mice. Although overall immunogenicity was affected, the model epitope (sequence DPAF) remained the predominant recognition site regardless of the conformation in which it was presented. A comparison of anti-DPAF mAbs obtained in response to two analogue peptides, PS1CT3 and CysCT3, in which the DPAF segment was either unconstrained or held within a cyclic loop, respectively, revealed a significant homology in the paratope composition. At one level a subset of anti-PS1CT3 and anti-CysCT3 mAbs was found to share a common heavy chain variable region. In addition, nucleotide sequence homology comparisons of both heavy and light chain variable regions identified the presence of anti-PS1CT3 and anti-CysCT3 mAbs that collectively appeared to derive from a common progenitor, but with nonidentical somatic mutations. Interestingly, however, no bias toward homologous Ag could be discerned on measurement of relative affinities of the mAbs for the two peptides. In contrast, mAb binding on-rates clearly discriminated between peptides representing the homologous vs the heterologous confomer of the DPAF epitope. Thus, it would appear that the kinetics of Ag recognition dominate over equilibrium binding criteria both in epitope-driven repertoire selection and Ab maturation in a humoral response.

Human T-helper cell responses to a synthetic peptide derived from the hepatitis B surface antigen

Hepatitis B virus surface antigen peptide OS (aa124-147) self oligomerizes to form conformational B-cell immunogen with several properties of a candidate peptide vaccine. It gives a T-cell blastogenic response in vaccinated as well as naturally infected individuals. To study the nature and localization of the T-helper cell epitopes, the T-lymphocyte proliferative responses in humans exposed to hepatitis B surface antigen (HBsAg) were examined with a synthetic peptide representing residues 124-147 of this antigen [peptide OS (aa24-147)]. Positive responses were obtained in most cases regardless of whether HBsAg exposure was due to vaccination or a hepatitis B viral infection. Epitope localization studies with truncated peptides indicated the presence of more than two HBsAg-relevant T-helper cell epitopes. This was also corroborated by our fine mapping studies which revealed that the amino acid residues crucial for eventual T-helper cell activation were diverse amongst the various individuals. Together these studies suggest that immunization with peptide OS (aa124-147) may result in an HBsAg cross-reactive T-helper cell response in a broad spectrum of the human population.

A self-associating hepatitis B surface antigen-derived peptide that is immunogenic in alum

We previously described an oligomeric synthetic peptide derived from the hepatitis B surface antigen that displayed a limited tendency to form self-associating macromolecular structures in solution. Here it is demonstrated that amino-terminal myristylation of this peptide results in near quantitative aggregation of the oligomeric peptide. The myristylated peptide is highly immunogenic when used in conjunction with alum as adjuvant in both the rabbit and rhesus monkey models. The antibody response generated by peptide also cross-reacted with native antigen and was long-lasting. Collectively the results described in this and previous reports offer an attractive new approach for generating immunogenic peptide mimetics of conformational epitopes that may find application as vaccines.

Immune response to hepatitis B virus surface antigen peptides during HBV infection

Antibody responses of patients with acute (n = 73), fulminant (n = 30) and chronic (n = 51) hepatitis B virus (HBV) infection as well as recovered individuals (n = 7) were studied against three synthetic peptides, Pre-S1 amino acids (aa. 12-32), Pre-S2 amino acids (aa. 120-145), and S amino acids (aa. 124-147) of the envelope region (HBsAg). T cell blastogenic response was investigated in a proportion of the patients (27 acute, nine fulminant, 13 chronic hepatitis and seven recovered individuals) along with seven HBV vaccinated and three normal individuals. The presence of T cell response against S peptide was observed in all the cases (9/9, 100%) during early acute hepatitis. This was suppressed during late stages (8/18, 44%) followed by partial reversal during recovery (5/7, 71%). T cell response and antibodies to Pre-S1 and Pre-S2 peptides were present only in one-third of the patients throughout these periods. The T cell blastogenic response as well as antibody reactivity against these peptides were absent and minimal in chronic hepatitis. Immune response against envelope protein appears to play a major role in acute hepatic injury due to HBV infection and help in virus clearance.

Identification of a new group-specific determinant on hepatitis B surface antigen with a synthetic peptide

In a recent study we demonstrated that a synthetic peptide representing residues 124-147 of the major protein of hepatitis B surface Ag (HBsAg) undergoes spontaneous oligomerization to reconstruct one or more conformational group-specific determinants on HBsAg. The present study was undertaken to identify and characterize the HBsAg-related antigenic determinants on this oligomeric peptide (peptide OS[124-147]). A panel of nine analogs of this peptide was generated by either deleting, substituting, or chemical side chain modification of specific amino acid residues. With HBsAg subtype-specific antisera a single "a" epitope was identified as one that includes Met133 and Lys141. In addition a "d" epitope toward the amino-terminal end of the sequence was also observed. Perturbation of certain amino acid residues was found to enhance a antigenicity and subsequent experiments indicated that maximal expression of this a antigenicity is dependent in part on accessibility of the Lys141 side chain and in part on the primary sequence. With a total of 50 human anti-HBsAg serum samples obtained from individuals vaccinated against hepatitis B, it was demonstrated that these sera recognize the Met133-Lys141-dependent a epitope as the dominant, and in many cases the only, determinant on peptide OS[124-147]. Finally, on immunization, peptide OS[124-147] elicits an anti-HBsAg response that is predominantly anti-a though a lesser contribution from an anti-d response was also obtained.

Identification of a new group-specific determinant on hepatitis B surface antigen with a synthetic peptide

In a recent study we demonstrated that a synthetic peptide representing residues 124-147 of the major protein of hepatitis B surface Ag (HBsAg) undergoes spontaneous oligomerization to reconstruct one or more conformational group-specific determinants on HBsAg. The present study was undertaken to identify and characterize the HBsAg-related antigenic determinants on this oligomeric peptide (peptide OS[124-147]). A panel of nine analogs of this peptide was generated by either deleting, substituting, or chemical side chain modification of specific amino acid residues. With HBsAg subtype-specific antisera a single "a" epitope was identified as one that includes Met133 and Lys141. In addition a "d" epitope toward the amino-terminal end of the sequence was also observed. Perturbation of certain amino acid residues was found to enhance a antigenicity and subsequent experiments indicated that maximal expression of this a antigenicity is dependent in part on accessibility of the Lys141 side chain and in part on the primary sequence. With a total of 50 human anti-HBsAg serum samples obtained from individuals vaccinated against hepatitis B, it was demonstrated that these sera recognize the Met133-Lys141-dependent a epitope as the dominant, and in many cases the only, determinant on peptide OS[124-147]. Finally, on immunization, peptide OS[124-147] elicits an anti-HBsAg response that is predominantly anti-a though a lesser contribution from an anti-d response was also obtained.

Indian hepatitis E virus shows a major deletion in the small open reading frame

Enterically transmitted non-A, non-B hepatitis virus (HEV), the causative agent for sporadic and large epidemic outbreaks in developing countries, contains a positive-sense single-stranded RNA genome. The genome of the virus encodes three open reading frames (ORF1, ORF2, and ORF3). The gene segment corresponding to the small open reading frame (ORF3), overlapping between ORF1 and ORF2, was synthesized by reverse transcription-polymerase chain reaction (RT-PCR) from a number of previously identified HEV-positive clinical specimens. A DNA fragment of 166 bp was consistently obtained from all the clinical specimens. This small fragment was cloned, sequenced, and found to contain an open reading frame encoding only 41 amino acid residues. Comparison of our results with that of geographically related Burma HEV suggests a major inframe deletion of 246 bp in the ORF3 of Indian strain. The protein encoded by ORF3 does not appear to be useful for early serodiagnosis as a synthetic peptide deduced from the truncated ORF3 failed to show any demonstrable immunoreactivity against HEV-infected acute phase sera in an enzyme-linked immunosorbent assay.

A synthetic peptide spontaneously self-assembles to reconstruct a group-specific, conformational determinant of hepatitis B surface antigen

A cysteine-rich peptide of sequence 124 to 147 of the major protein of hepatitis B surface Ag (HBsAg) was synthesized. On cleavage and subsequent work-up it was found that all of the cysteine sulfhydryl groups had spontaneously formed disulfide bonds to yield a heterogenous mixture of multiple forms with molecular masses ranging from 8 to 35 kDa (peptide OS[124-147]). In a direct ELISA peptide OS[124-147] showed a high degree of cross-reactivity with polyclonal anti-HBsAg antiserum whereas the HBsAg-related antigenicity of its disulfide-reduced analogs was insignificant. Peptide OS[124-147] was also recognized by all 15 of the anti-HBsAg-positive human sera tested. Further studies revealed that peptide OS[124-147] represents the conformational, disulfide-dependent "a" determinant of HBsAg and elicits antibodies that cross-react with a variety of HBsAg subtypes. Anti-peptide antibodies bound to the corresponding native epitope with an apparent affinity higher than that of homologous antisera. Finally, polyclonal anti-OS[124-147] antibodies could also immunoprecipitate purified Dane particles in solution. Together these studies indicate that peptide OS[124-147] represents an excellent candidate component of a peptide-based vaccine for hepatitis B.

A synthetic peptide spontaneously self-assembles to reconstruct a group-specific, conformational determinant of hepatitis B surface antigen

A cysteine-rich peptide of sequence 124 to 147 of the major protein of hepatitis B surface Ag (HBsAg) was synthesized. On cleavage and subsequent work-up it was found that all of the cysteine sulfhydryl groups had spontaneously formed disulfide bonds to yield a heterogenous mixture of multiple forms with molecular masses ranging from 8 to 35 kDa (peptide OS[124-147]). In a direct ELISA peptide OS[124-147] showed a high degree of cross-reactivity with polyclonal anti-HBsAg antiserum whereas the HBsAg-related antigenicity of its disulfide-reduced analogs was insignificant. Peptide OS[124-147] was also recognized by all 15 of the anti-HBsAg-positive human sera tested. Further studies revealed that peptide OS[124-147] represents the conformational, disulfide-dependent "a" determinant of HBsAg and elicits antibodies that cross-react with a variety of HBsAg subtypes. Anti-peptide antibodies bound to the corresponding native epitope with an apparent affinity higher than that of homologous antisera. Finally, polyclonal anti-OS[124-147] antibodies could also immunoprecipitate purified Dane particles in solution. Together these studies indicate that peptide OS[124-147] represents an excellent candidate component of a peptide-based vaccine for hepatitis B.

Design and synthesis of a self-assembling peptide derived from the envelope proteins of HIV type 1. An approach to heterovalent immunogens

A chimeric peptide that included sequences from gp120 and gp41 of HIV type 1 was synthesized. Cleavage from solid support yielded a composite of self-oligomerized products with molecular masses ranging from 5 to about 9 kDa. The oligomer but not its reduced, monomeric form was recognized by human anti-HIV sera and at least one of the two lysines in the sequence was involved in antibody binding. The oligomeric peptide was immunogenic, yielding a conformation-specific antibody response. Co-oligomerization of a hepatitis B surface Ag-derived peptide and the HIV type 1-derived peptide yielded a bivalent product in which conformational integrity of the individual components was maintained. Immunization with this hybrid peptide resulted in conformation-specific antibodies to both epitopes in all four murine strains tested. Lymphocyte proliferation assays revealed that the T epitopes resident in both peptide sequences remained active in the hybrid peptide. These results demonstrate the potential of this approach in generating multi- and heterovalent immunogens which may eventually find application as vaccines.

Design and synthesis of a self-assembling peptide derived from the envelope proteins of HIV type 1. An approach to heterovalent immunogens

A chimeric peptide that included sequences from gp120 and gp41 of HIV type 1 was synthesized. Cleavage from solid support yielded a composite of self-oligomerized products with molecular masses ranging from 5 to about 9 kDa. The oligomer but not its reduced, monomeric form was recognized by human anti-HIV sera and at least one of the two lysines in the sequence was involved in antibody binding. The oligomeric peptide was immunogenic, yielding a conformation-specific antibody response. Co-oligomerization of a hepatitis B surface Ag-derived peptide and the HIV type 1-derived peptide yielded a bivalent product in which conformational integrity of the individual components was maintained. Immunization with this hybrid peptide resulted in conformation-specific antibodies to both epitopes in all four murine strains tested. Lymphocyte proliferation assays revealed that the T epitopes resident in both peptide sequences remained active in the hybrid peptide. These results demonstrate the potential of this approach in generating multi- and heterovalent immunogens which may eventually find application as vaccines.

Comparison of immune responses to a native viral antigen and a synthetic peptide derived from it: implications for vaccine development

Murine immune responses to the hepatitis B surface antigen (HBsAg) and a synthetic peptide derived from it were compared at the humoral level. Six of nine strains used responded to either peptide or HBsAg, though restriction profiles were not superimposable. Two of three strains non-responsive to HBsAg produced an antibody response on immunization with peptide which was cross-reactive with both peptide and HBsAg. In in vitro lymphocyte stimulation assays, lymphocyte from all six peptide-immunized mouse strains could be induced to proliferate on challenge with HBsAg. However, of the HBsAg-immunized groups, lymphocytes from only three of six responder strains proliferated on in vitro HBsAg challenge. Cumulatively, these results suggest that a vaccine formulation that includes both protein antigens and synthetic peptides derived from these proteins may be more effective at eliciting an immune response in a broader cross-section of target population.

Macromolecular self-association of a synthetic peptide derived from the hepatitis B surface antigen: construction of a quaternary epitope

A major impediment to the development of peptide vaccines has been the inability accurately to mimic conformationally constrained epitopes on the envelope proteins of pathogens. This limitation is further compounded by the fact that several viral envelope proteins exist either as covalently or non-covalently associated homo-oligomers in the native state. Evidence is now accumulating to indicate that, at least in some instances, these homo-oligomers display antigenic determinants that are not present in the dissociated monomer units. Clearly this problem will have to be addressed if peptide-based vaccines are ever to become feasible alternatives. In this report we demonstrate that an oligomerized synthetic peptide that was derived from the hepatitis B surface antigen aggregates in solution to form macromolecular structures. These aggregates appear to represent a 'native' form of the group-specific determinant presented by the hepatitis B surface antigen.

Interleukin-1 derived synthetic peptide as an added co-adjuvant in vaccine formulations

A synthetic peptide containing the immunostimulatory and receptor binding sequences of human IL-1 beta was synthesized and tested for its immunoadjuvant properties. Using a commercially available hepatitis B vaccine as model antigen we found that added peptide enhanced both total and protective antibody responses in high and low responder strains of mice but was unable to overcome non-responsiveness in a third strain. Increased antibody response to antigen in the responder strains was not accompanied by any significant alteration in IgG isotype composition. These results suggest that this peptide may prove useful as a co-adjuvant in vaccines.