Genetic Factors Altering Immune Responses in Atrial Fibrillation: JACC Review Topic of the Week

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide and is associated with a range of adverse clinical outcomes. Accumulating evidence points to inflammatory processes resulting from innate immune responses as a cornerstone in AF pathogenesis. Genetic and epigenetic factors affecting leukocytes have been identified as key modulators of the inflammatory response. Inherited variants in genes encoding proteins involved in the innate immune response have been associated with increased risk for AF recurrence and stroke in AF patients. Furthermore, acquired somatic mutations associated with clonal hematopoiesis of indeterminate potential, leukocyte telomere shortening, and epigenetic age acceleration contribute to increased AF risk. In individuals carrying clonal hematopoiesis of indeterminate potential, myocardial monocyte-derived macrophage shift toward a proinflammatory phenotype may precipitate AF. Further studies are needed to better understand the role of genetic regulation of the native immune response in atrial arrhythmogenesis and its therapeutic potential as a target for personalized medicine.

Multi-ancestry genome-wide study identifies effector genes and druggable pathways for coronary artery calcification

Coronary artery calcification (CAC), a measure of subclinical atherosclerosis, predicts future symptomatic coronary artery disease (CAD). Identifying genetic risk factors for CAC may point to new therapeutic avenues for prevention. Currently, there are only four known risk loci for CAC identified from genome-wide association studies (GWAS) in the general population. Here we conducted the largest multi-ancestry GWAS meta-analysis of CAC to date, which comprised 26,909 individuals of European ancestry and 8,867 individuals of African ancestry. We identified 11 independent risk loci, of which eight were new for CAC and five had not been reported for CAD. These new CAC loci are related to bone mineralization, phosphate catabolism and hormone metabolic pathways. Several new loci harbor candidate causal genes supported by multiple lines of functional evidence and are regulators of smooth muscle cell-mediated calcification ex vivo and in vitro. Together, these findings help refine the genetic architecture of CAC and extend our understanding of the biological and potential druggable pathways underlying CAC.

Hematopoietic Somatic Mosaicism Is Associated With an Increased Risk of Postoperative Atrial Fibrillation

BACKGROUND

On-pump cardiac surgery triggers sterile inflammation and postoperative complications such as postoperative atrial fibrillation (POAF). Hematopoietic somatic mosaicism (HSM) is a recently identified risk factor for cardiovascular diseases and results in a shift toward a chronic proinflammatory monocyte transcriptome and phenotype.

OBJECTIVES

The aim of this study was to assess the prevalence, characteristics, and impact of HSM on preoperative blood and myocardial myeloid cells as well as on outcomes after cardiac surgery.

METHODS

Blood DNA from 104 patients referred for surgical aortic valve replacement (AVR) was genotyped using the HemePACT panel (576 genes). Four screening methods were applied to assess HSM, and postoperative outcomes were explored. In-depth blood and myocardial leukocyte phenotyping was performed in selected patients using mass cytometry and preoperative and postoperative RNA sequencing analysis of classical monocytes.

RESULTS

The prevalence of HSM in the patient cohort ranged from 29%, when considering the conventional HSM panel (97 genes) with variant allelic frequencies ≥2%, to 60% when considering the full HemePACT panel and variant allelic frequencies ≥1%. Three of 4 explored HSM definitions were significantly associated with higher risk for POAF. On the basis of the most inclusive definition, HSM carriers exhibited a 3.5-fold higher risk for POAF (age-adjusted OR: 3.5; 95% CI: 1.52-8.03; P = 0.003) and an exaggerated inflammatory response following AVR. HSM carriers presented higher levels of activated CD64+CD14+CD16- circulating monocytes and inflammatory monocyte-derived macrophages in presurgery myocardium.

CONCLUSIONS

HSM is frequent in candidates for AVR, is associated with an enrichment of proinflammatory cardiac monocyte-derived macrophages, and predisposes to a higher incidence of POAF. HSM assessment may be useful in the personalized management of patients in the perioperative period. (Post-Operative Myocardial Incident & Atrial Fibrillation [POMI-AF]; NCT03376165).

The BNT162b2 mRNA SARS-CoV-2 vaccine induces transient afucosylated IgG1 in naive but not in antigen-experienced vaccinees

BACKGROUND

Afucosylated IgG1 responses have only been found against membrane-embedded epitopes, including anti-S in SARS-CoV-2 infections. These responses, intrinsically protective through enhanced FcγRIIIa binding, can also trigger exacerbated pro-inflammatory responses in severe COVID-19. We investigated if the BNT162b2 SARS-CoV-2 mRNA also induced afucosylated IgG responses.

METHODS

Blood from vaccinees during the first vaccination wave was collected. Liquid chromatography-Mass spectrometry (LC-MS) was used to study anti-S IgG1 Fc glycoprofiles. Responsiveness of alveolar-like macrophages to produce proinflammatory cytokines in presence of sera and antigen was tested. Antigen-specific B cells were characterized and glycosyltransferase levels were investigated by Fluorescence-Activated Cell Sorting (FACS).

FINDINGS

Initial transient afucosylated anti-S IgG1 responses were found in naive vaccinees, but not in antigen-experienced ones. All vaccinees had increased galactosylated and sialylated anti-S IgG1. Both naive and antigen-experienced vaccinees showed relatively low macrophage activation potential, as expected, due to the low antibody levels for naive individuals with afucosylated IgG1, and low afucosylation levels for antigen-experienced individuals with high levels of anti-S. Afucosylation levels correlated with FUT8 expression in antigen-specific plasma cells in naive individuals. Interestingly, low fucosylation of anti-S IgG1 upon seroconversion correlated with high anti-S IgG levels after the second dose.

INTERPRETATION

Here, we show that BNT162b2 mRNA vaccination induces transient afucosylated anti-S IgG1 responses in naive individuals. This observation warrants further studies to elucidate the clinical context in which potent afucosylated responses would be preferred.

FUNDING

LSBR1721, 1908; ZonMW10430012010021, 09150161910033, 10430012010008; DFG398859914, 400912066, 390884018; PMI; DOI4-Nr. 3; H2020-MSCA-ITN 721815.

DNA methyltransferase 3 alpha and TET methylcytosine dioxygenase 2 restrain mitochondrial DNA-mediated interferon signaling in macrophages

Deleterious somatic mutations in DNA methyltransferase 3 alpha (DNMT3A) and TET mehtylcytosine dioxygenase 2 (TET2) are associated with clonal expansion of hematopoietic cells and higher risk of cardiovascular disease (CVD). Here, we investigated roles of DNMT3A and TET2 in normal human monocyte-derived macrophages (MDM), in MDM isolated from individuals with DNMT3A or TET2 mutations, and in macrophages isolated from human atherosclerotic plaques. We found that loss of function of DNMT3A or TET2 resulted in a type I interferon response due to impaired mitochondrial DNA integrity and activation of cGAS signaling. DNMT3A and TET2 normally maintained mitochondrial DNA integrity by regulating the expression of transcription factor A mitochondria (TFAM) dependent on their interactions with RBPJ and ZNF143 at regulatory regions of the TFAM gene. These findings suggest that targeting the cGAS-type I IFN pathway may have therapeutic value in reducing risk of CVD in patients with DNMT3A or TET2 mutations.

High titers and low fucosylation of early human anti-SARS-CoV-2 IgG promote inflammation by alveolar macrophages

Patients diagnosed with coronavirus disease 2019 (COVID-19) become critically ill primarily around the time of activation of the adaptive immune response. Here, we provide evidence that antibodies play a role in the worsening of disease at the time of seroconversion. We show that early-phase severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) spike protein-specific immunoglobulin G (IgG) in serum of critically ill COVID-19 patients induces excessive inflammatory responses by human alveolar macrophages. We identified that this excessive inflammatory response is dependent on two antibody features that are specific for patients with severe COVID-19. First, inflammation is driven by high titers of anti-spike IgG, a hallmark of severe disease. Second, we found that anti-spike IgG from patients with severe COVID-19 is intrinsically more proinflammatory because of different glycosylation, particularly low fucosylation, of the antibody Fc tail. Low fucosylation of anti-spike IgG was normalized in a few weeks after initial infection with SARS-CoV-2, indicating that the increased antibody-dependent inflammation mainly occurs at the time of seroconversion. We identified Fcγ receptor (FcγR) IIa and FcγRIII as the two primary IgG receptors that are responsible for the induction of key COVID-19-associated cytokines such as interleukin-6 and tumor necrosis factor. In addition, we show that anti-spike IgG-activated human macrophages can subsequently break pulmonary endothelial barrier integrity and induce microvascular thrombosis in vitro. Last, we demonstrate that the inflammatory response induced by anti-spike IgG can be specifically counteracted by fostamatinib, an FDA- and EMA-approved therapeutic small-molecule inhibitor of Syk kinase.

Afucosylated IgG characterizes enveloped viral responses and correlates with COVID-19 severity

Antibodies are divided into several classes based on their nonvariable tail (Fc) domains. These regions interact with disparate immune cell receptors and complement proteins to help instruct distinct immune responses. The Fc domain of immunoglobulin G (IgG) antibodies contains a conserved N-linked glycan at position 297. However, the particular glycan used at this position is highly variable. IgG lacking core fucosylation at this position initiates enhanced antibody-dependent cellular cytotoxicity by increased affinity to the Fc receptor FcRIIIa. Larsen et al. report that COVID-19 patients with severe symptoms have increased levels of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG afucosylation compared with patients with mild disease. These findings suggest that treatment of COVID-19 patients with fucosylated anti–SARS-CoV-2 antibodies may circumvent pathologies associated with severe COVID-19.

Science, this issue p. eabc8378

INTRODUCTION

Antibody function is often considered static and mostly determined by isotype and subclass. The conserved N-linked glycan at position 297 in the Fc domain of immunoglobulin G (IgG) is essential for an antibody’s effector functions. Moreover, this glycan is highly variable and functionally relevant, especially for the core fucose moiety. IgG lacking core fucosylation (afucosylated IgG) causes increased antibody-dependent cellular cytotoxicity (ADCC) through highly increased IgG-Fc receptor IIIa (FcγRIIIa) affinity. Despite constant levels of total plasma IgG-Fc fucosylation above 90%, specific IgG responses with low core fucosylation have been sporadically reported. These are directed against alloantigens on blood cells and glycoproteins of HIV and dengue virus. In this study, we investigated the induction of afucosylated IgG to various antigens and delineated its dynamics and proinflammatory potential in COVID-19.

RATIONALE

Afucosylated IgG responses have only been found in various alloimmune responses against cellular blood groups and two enveloped viruses. Therefore, we tested the hypothesis that foreign surface–exposed, membrane-embedded proteins induce a specific B cell response that results in afucosylated IgG. We compared immune responses to natural infections by enveloped viruses and nonenveloped viruses, protein subunit vaccination, and live attenuated virus vaccinations. We also assessed the relation to the clinical outcome of such a response in COVID-19.

RESULTS

Analogous to blood cell alloantigens, the response to all enveloped viruses showed clear signatures of afucosylation of the antigen-specific IgG. By contrast, IgG against the nonenveloped virus, parvovirus B19, were highly fucosylated. The extent of afucosylated IgG responses varied, both between individuals and between antigens. The viral context was essential to induce afucosylated IgG because induction did not occur after subunit vaccination against hepatitis B virus. However, afucosylated IgG responses were found in response to attenuated viruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–specific afucosylated IgG were also found in critically ill COVID-19 patients but not in individuals with mild symptoms. Over the 2 weeks after seroconversion, the amount of fucosylated anti–SARS-CoV-2 IgG increased markedly, in most reaching relative levels similar to those found in total IgG. Afucosylated IgG promoted interleukin-6 (IL-6) release in macrophages cultured in vitro, which is in line with an observed association of SARS-CoV-2–specific IgG afucosylation with IL-6 and C-reactive protein (CRP) in these patients.

CONCLUSION

This work suggests that providing foreign B cell antigens in the context of host cells may be required to trigger an afucosylated IgG immune response. The strength of this response is highly variable for different antigens and between individuals. An afucosylated IgG response is a potent immune response, honed for the destruction of target cells by FcγRIII-expressing natural killer (NK) and myeloid cells. This may sometimes be desirable—for example, against HIV—and can be achieved in vaccines by providing the target as a surface protein, as is the case with attenuated viral vaccines or mRNA vaccines. However, for SARS-CoV-2, this afucosylated IgG response may promote the exacerbation of COVID-19 under conditions with high viral loads at the time of seroconversion.

Immunoglobulin G (IgG) antibodies are crucial for protection against invading pathogens. A highly conserved N-linked glycan within the IgG-Fc tail, which is essential for IgG function, shows variable composition in humans. Afucosylated IgG variants are already used in anticancer therapeutic antibodies for their increased activity through Fc receptors (FcγRIIIa). Here, we report that afucosylated IgG (approximately 6% of total IgG in humans) are specifically formed against enveloped viruses but generally not against other antigens. This mediates stronger FcγRIIIa responses but also amplifies brewing cytokine storms and immune-mediated pathologies. Critically ill COVID-19 patients, but not those with mild symptoms, had high concentrations of afucosylated IgG antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), amplifying proinflammatory cytokine release and acute phase responses. Thus, antibody glycosylation plays a critical role in immune responses to enveloped viruses, including COVID-19.

Treatment with Statins Does Not Revert Trained Immunity in Patients with Familial Hypercholesterolemia

Individuals with elevated LDL-cholesterol levels have an increased risk for cardiovascular disease. Despite lipid lowering strategies, however, a significant cardiovascular risk remains. Bekkering et al. show that monocytes from patients with familial hypercholesterolemia have a trained immunity phenotype and that lipid lowering with statins does not revert this pro-inflammatory phenotype.

Interactions between dyslipidemia and the immune system and their relevance as putative therapeutic targets in atherosclerosis

Cardiovascular disease (CVD) continues to be a leading cause of death worldwide with atherosclerosis being the major underlying pathology. The interplay between lipids and immune cells is believed to be a driving force in the chronic inflammation of the arterial wall during atherogenesis. Atherosclerosis is initiated as lipid particles accumulate and become trapped in vessel walls. The subsequent immune response, involving both adaptive and immune cells, progresses plaque development, which may be exacerbated under dyslipidemic conditions. Broad evidence, especially from animal models, clearly demonstrates the effect of lipids on immune cells from their development in the bone marrow to their phenotypic switching in circulation. Interestingly, recent research has also shown a long-lasting epigenetic signature from lipids on immune cells. Traditionally, cardiovascular therapies have approached atherosclerosis through lipid-lowering medications because, until recently, anti-inflammatory therapies have been largely unsuccessful in clinical trials. However, the recent Canakinumab Antiinflammatory Thrombosis Outcomes Study (CANTOS) provided pivotal support of the inflammatory hypothesis of atherosclerosis in man spurring on anti-inflammatory strategies to treat atherosclerosis. In this review, we describe the interactions between lipids and immune cells along with their specific outcomes as well as discuss their future perspective as potential cardiovascular targets.

CD70 limits atherosclerosis and promotes macrophage function

The costimulatory molecule CD70 is expressed on activated immune cells and is known to modulate responses of T, B, and NK cells via its receptor CD27. Until now, there is only limited data describing the role of CD70 in atherosclerosis. We observed that ruptured human carotid atherosclerotic plaques displayed higher CD70 expression than stable carotid atherosclerotic plaques, and that CD70 expression in murine atheroma localized to macrophages. Lack of CD70 impaired the inflammatory capacity (e. g. reactive oxygen species and nitric oxide production) of bone marrow-derived macrophages, increased both M1-like and M2-like macrophage markers, and rendered macrophages meta-bolically inactive and prone to apoptosis. Moreover, CD70-deficient macrophages expressed diminished levels of scavenger receptors and ABC-transporters, impairing uptake of oxidised low-density lipoprotein (oxLDL) and cholesterol efflux, respectively. Hyperlipidaemic Apoe −/− mice reconstituted with CD70-deficient bone marrow displayed a profound increase in necrotic core size, plaque area, and number of lesional macrophages as compared to mice receiving control bone marrow. Accordingly, 18 week-old, chow diet-fed CD70-deficient Apoe−/−mice displayed larger atheroma characterised by lower cellularity and more advanced plaque phenotype than Apoe−/− mice. In conclusion, CD70 promotes macrophage function and viability and is crucial for effective phagocytosis and efflux of oxLDL. Deficiency in CD70 results in more advanced atheroma. Our data suggest that CD70 mitigates atherosclerosis at least in part by modulating macrophage function.

Note: The review process for this manuscript was fully handled by G. Y. H. Lip, Editor in Chief.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Endothelial CSN5 impairs NF-κB activation and monocyte adhesion to endothelial cells and is highly expressed in human atherosclerotic lesions

The COP9 signalosome (CSN), a multifunctional protein complex involved in the regulation of cullin-RING-E3 ubiquitin ligases (CRLs), has emerged as a regulator of NF-κB signalling. As NF-κB drives the expression of pro-inflammatory and pro-atherosclerotic genes, we probed the yet unknown role of the CSN, in particular CSN5, on NF-KB-mediated atherogenic responses in endothelial cells. Co-immunoprecipitation in human umbilical vein endothelial cells (HUVECs) revealed the presence of a super-complex between IKK and CSN, which dissociates upon TNF-α stimulation. Furthermore, CSN5 silencing enhanced TNF-α-induced IKB-α degradation and NF-κB activity in luci-ferase reporter assays. This was paralleled by an increased NF-KB-driven upregulation of atherogenic chemokines and adhesion molecules, as measured by qPCR and flow cytometry, and translated into an enhanced arrest of THP-1 monocytes on TNF-α-stimulated, CSN5-depleted HUVECs. Reverse effects on NF-κB activity and THP-1 arrest were seen upon CSN5 overexpression. Finally, double-immunostaining confirmed the expression of CSN subunits in the endothelium of human atherosclerotic lesions, and revealed an increased expression of CSN5 which correlated with atheroprogression. In conclusion, endothelial CSN5 attenuates NF-KB-dependent pro-inflammatory gene expression and monocyte arrest on stimulated endothelial cells in vitro, suggesting that CSN5 might serve as a negative regulator of atherogenesis.

Note: The review process for this manuscript was fully handled by G. Y. H. Lip, Editor in Chief.

Abstract 441: Macrophage CD40 in Atherosclerosis, Obesity and Multiple Sclerosis

Introduction: The co-stimulatory dyad CD40-CD40L plays a central role in fine-tuning immune reactions in atherosclerosis, obesity-induced inflammation and multiple sclerosis (MS). Inhibition of CD40 in atherosclerosis and experimental autoimmune encephalomyelitis (EAE) ameliorates disease outcome, whereas CD40-deficiency in a diet induced obesity (DIO) model worsens insulin resistance and induces excessive adipose tissue inflammation. Although inhibition of CD40 has powerful effects, we do not know which CD40 expressing cell-type is responsible for the amelioration/aggravation of disease. As myeloid CD40 is known to play a role in leukocyte trafficking, which is important in atherosclerosis, obesity and neuro-inflammation, we hypothesize that myeloid CD40 is important in these disease modalities.

Methods: To investigate the role of myeloid CD40 in atherosclerosis, obesity and EAE we have generated macrophage specific LysM-CD40flfl - (ApoE-/-), and dendritic cell/adipose tissue macrophage specific CD11C-CD40flfl). Atherosclerosis was induced by aging the LysM-CD40flfl - ApoE-/- mice until 30 weeks. EAE was induced in LysM-CD40flfl mice by subjecting them to myelin oligodendrocyte glycoprotein peptide (MOG35-55), and LysM-CD40flfl and CD11c-CD40flfl mice were subjected to a 60% high fat diet for 18 wks.

Results: LysM-CD40flfl - ApoE-/- mice showed a significant reduction in atherosclerotic plaque area, with a reduced macrophage accumulation. Loss of macrophage CD40 in EAE results in a significant decrease in the neurological symptoms of EAE, and a majority of the LysM-CD40flfl mice were fully protected against EAE. LysM-CD40flfl mice subjected to DIO showed an increase in macrophage accumulation in the visceral adipose tissue, but did not affect adipose tissue mass, insulin tolerance, or plasma triglyceride concentrations. The CD11CcreCD40flfl mice exhibited a decrease in visceral adipose tissue weight, an increased lipid content in the liver and slightly decreases leukocyte numbers and pro-inflammatory gene expression in the adipose tissue.

Conclusions: Macrophage CD40 is an important driver of atherosclerosis and EAE. Macrophage CD40 is protective in obesity-induced inflammation, but is probably not the key player.

The IgM response to modified LDL in experimental atherosclerosis: hypochlorite-modified LDL IgM antibodies versus classical natural T15 IgM antibodies

INTRODUCTION

It is hypothesized that IgM antibodies to oxidized LDL are anti-atherogenic. Myeloperoxidase from plaque-infiltrating neutrophils catalyzes the production of hypochlorite (HOCl), which oxidizes LDL. Here we study the IgM response to HOCl-modified LDL in comparison to titers of T15 clonotypic natural antibodies.

METHODS

Plasma of LDLR(-/-) mice fed a normal chow or high-fat diet was obtained after 6 and 16 weeks. The IgM responses to HOCl-modified LDL and T15 clonotypic natural IgM antibodies were measured by ELISA.

RESULTS

The IgM levels in response to HOCl-modified LDL increased dramatically in the atherosclerotic group after introduction of the high-fat diet, but not in mice on normal chow. The natural IgM T15 clonotypic antibody titers revealed a more moderate increase during atherogenesis.

CONCLUSION

Our results show that during atherogenesis there is a strong induction of IgM antibodies to HOCl-modified LDL particles. Whether these induced IgM antibodies are pro- or anti-atherogenic remains to be established.

Rupture of the atherosclerotic plaque: does a good animal model exist?

By its very nature, rupture of the atherosclerotic plaque is difficult to study directly in humans. A good animal model would help us not only to understand how rupture occurs but also to design and test treatments to prevent it from happening. However, several difficulties surround existing models of plaque rupture, including the need for radical interventions to produce the rupture, lack of direct evidence of rupture per se, and absence of convincing evidence of platelet- and fibrin-rich thrombus at the rupture site. At the present time, attention should therefore focus on the processes of plaque breakdown and thrombus formation in humans, whereas the use of animal models should probably be reserved for studying the function of particular genes and for investigating isolated features of plaques, such as the relationship between cap thickness and plaque stability.

Activity of human Delta5 and Delta6 desaturases on multiple n-3 and n-6 polyunsaturated fatty acids

Yeast co-expressing human elongase and desaturase genes were used to investigate whether the same desaturase gene encodes an enzyme able to desaturate n-3 and n-6 fatty acids with the same or different carbon chain length. The results clearly demonstrated that a single human Delta5 desaturase is active on 20:3n-6 and 20:4n-3. Endogenous Delta6 desaturase substrates were generated by providing to the yeast radiolabelled 20:4n-6 or 20:5n-3 which, through two sequential elongations, produced 24:4n-6 and 24:5n-3, respectively. Overall, our data suggest that a single human Delta6 desaturase is active on 18:2n-6, 18:3n-3, 24:4n-6 and 24:5n-3.

Activity and mRNA abundance of Delta-5 and Delta-6 fatty acid desaturases in two human cell lines

We analyzed fatty acid biosynthesis in Chang and ZR-75-1 cells. Both cell lines could desaturate and further elongate substrates for Delta-5 desaturase. ZR-75-1 but not Chang cells showed Delta-6 desaturation of 18:2n-6, 18:3n-3, 24:4n-6 and 24:5n-3. In both cell lines, the mRNA abundance can be related to Delta-5 or Delta-6 fatty acid desaturase activities. These results suggest that desaturase genes could have, at least in part, independent control mechanisms and that Delta-6 desaturase impairment is not specific to any particular step of the fatty acid metabolic pathways, which may diminish the rationale for the existence of at least two distinct enzymes.

A pilot study to investigate the treatment of anogenital warts with Topical Lithium Succinate cream (8% lithium succinate, 0.05% zinc sulphate)

The incidence of anogenital warts (condyloma acuminatum) is rapidly increasing while there is still no totally satisfactory treatment available. In light of the emphasis of experimental approaches toward the prevention of viral replication and evidence of the antiviral action of lithium salts it was proposed to investigate the efficacy of Topical Lithium Succinate cream (LSC) in the treatment of anogenital warts. A total of 101 patients (42 women, 59 men) were randomized to receive either active or placebo treatment for a period of 4 weeks. Assessment of the number, location, size and area of coverage of the warts was made by the clinician at baseline, weeks 2, 4, 6 and 12. Compliance to the study protocol following cessation of treatment at week 4 was extremely poor. The high drop-out rate after this was felt to invalidate data collected after that point. It was therefore decided that the analysis should concentrate on the treatment period. Of 101 patients entering the trial 51 received active (30 male and 21 female) and 50 received placebo (29 male, 21 female). The primary efficacy variable was percentage change from baseline in the overall coverage of lesions. Over all patients LSC treatment resulted in a reduction of 42% (P<0.02) in the overall coverage of lesions. Separate analyses for male and female patients showed that for males there was a highly significant reduction in the coverage of lesions of 65% (P<0.02). However for females the reduction of 11% was not significant. A possible explanation for this difference between the sexes is that as many of the lesions in the female patients were internal therefore this could lead to difficulty in both application of the cream, and subsequent lesion assessment.

Bacterially expressed antigenic peptide from foot-and-mouth disease virus capsid elicits variable immunologic responses in animals

A fusion protein consisting of beta-galactosidase (GZ) to which was attached at its N-terminus the amino acid sequence corresponding to residues 142-160 of the immunogenic protein VP1 of foot-and-mouth disease virus (FMDV) has been expressed in E. coli. A chemically synthesized section of DNA corresponding to the amino acid sequence 142-160 was inserted into a vector (pXY410) designed to express fusion proteins with the carboxy terminal 1015 amino acids of GZ. The hybrid protein immunopurified by a GZ-specific monoclonal antibody was soluble, retained full GZ activity, and induced virus-neutralizing antibody in guinea pigs and mice. There were significant differences between the responses of individual mice to the FMDV peptide sequence, although the titers against GZ were uniformly high. This variable pattern did not change after hyperimmunization and was demonstrable in a range of mouse strains of different haplotype. The same results were obtained whether the response was measured by virus neutralization or by RIA against the FMDV peptide sequence. The possible reasons for the variable recognition of the FMDV epitopes by individual mice are discussed.

Bacterially expressed antigenic peptide from foot-and-mouth disease virus capsid elicits variable immunologic responses in animals

A fusion protein consisting of beta-galactosidase (GZ) to which was attached at its N-terminus the amino acid sequence corresponding to residues 142-160 of the immunogenic protein VP1 of foot-and-mouth disease virus (FMDV) has been expressed in E. coli. A chemically synthesized section of DNA corresponding to the amino acid sequence 142-160 was inserted into a vector (pXY410) designed to express fusion proteins with the carboxy terminal 1015 amino acids of GZ. The hybrid protein immunopurified by a GZ-specific monoclonal antibody was soluble, retained full GZ activity, and induced virus-neutralizing antibody in guinea pigs and mice. There were significant differences between the responses of individual mice to the FMDV peptide sequence, although the titers against GZ were uniformly high. This variable pattern did not change after hyperimmunization and was demonstrable in a range of mouse strains of different haplotype. The same results were obtained whether the response was measured by virus neutralization or by RIA against the FMDV peptide sequence. The possible reasons for the variable recognition of the FMDV epitopes by individual mice are discussed.

Production of epidermal growth factor in Escherichia coli from a synthetic gene

Mouse epidermal growth factor (EGF) is under investigation as a deflecting agent for sheep. Substantial quantities of the pure protein are required for these studies and to supply this need a gene for the protein was synthesized and inserted into plasmid vectors to direct the expression of EGF polypeptide, or fusion proteins containing the EGF peptide sequence, in transformed Escherichia coli. Mature EGF was released by lysine specific proteolysis of a fusion protein consisting of part of the E. coli TrpE protein, a lysine linker and EGF polypeptide. The EGF was purified and characterized and was found to be biologically active.

The impact of new technologies on vaccine development

The ability to move genetic determinants between species using in vitro gene-manipulation techniques has opened up new approaches to vaccine development. This has rapidly grown into an exciting area of research in both academic and industrial laboratories. There are numerous scientific challenges which require multidisciplinary teams to solve problems in creating new immunogens. This has challenged our existing knowledge about protein structure and conformation, microbial pathogenicity and the immune system. Recombinant-DNA techniques are invaluable as tools of analysis and antigen production. The surface of micro-organisms can also be minutely explored with the use of synthetic peptides and monoclonal antibodies. Nevertheless, these new technologies do not allow us to circumvent the need for detailed understanding of pathogens and the disease process. What is apparent from the work carried out so far is that there are few easy answers to vaccine development and it is not realistic to expect rapid solutions to these problems. As there are many potential targets for constructing novel vaccines for both human and animal diseases, it is helpful to establish some priorities. There is a tendency to look at the existing effective vaccines and simply direct research at producing them more economically or with enhanced safety and stability. The advantage of this approach is that considerable background work will have already been carried out establishing the basis for the application of recombinant DNA techniques. However, this can also lead to conflicts (often within the same institute or company) between the new and old technologies. This could be to the detriment of the new technologies which are still only partly developed and may not be good enough yet to compete with existing vaccines in cost or efficacy. The more ambitious, and eventually more rewarding, approach is to attempt to develop new vaccines where none had existed before. There is a vast untapped market, especially in the parasitic diseases, but the scientific problems may be considerable and much more background work is likely to be necessary. Indeed, most of the work in this area is more accurately referred to as basic research rather than vaccine development as totally new, effective vaccines are still some way off. Having directed research towards a specific organism or disease there are still many options available as to the scientific strategy to adopt. As discussed in this review it may be possible to consider subunits, synthetic antigens and live (attenuated or heterologous) organisms as possible vaccines.(ABSTRACT TRUNCATED AT 400 WORDS)