Assessment of the Implementation of Pakistan's National Action Plan on Antimicrobial Resistance in the Agriculture and Food Sectors

The agriculture and food (agrifood) sectors play key roles in the emergence, spread, and containment of antimicrobial resistance (AMR). Pakistan's first National Action Plan (NAP) on AMR was developed to guide One Health interventions to combat AMR through 2017-2022. To improve subsequent iterations, we assessed the implementation of Pakistan's NAP in the agrifood sectors (NAPag) in October 2022, using the Progressive Management Pathway on AMR tool developed by the Food and Agriculture Organization of the United Nations (FAO). The assessment tool addressed four crucial focus areas of the NAPag: governance, awareness, evidence, and practices. Each focus area contains multiple topics, which involve four sequential stages of activities to progressively achieve systematic management of AMR risk in the agrifood sectors. High-level representatives of the NAPag stakeholders provided information for the assessment through pre-event documentary review and workshop discussions. The assessment results showed that Pakistan's NAPag had an overall moderate coverage (59%) of the anticipated activities. Gaps were particularly notable in strengthening governance, good practices, and interventions in non-livestock sectors. Furthermore, only 12% of the evaluated activities were fully executed and documented, consistently remaining at the planning and piloting stages in the livestock sector across all the examined topics. Insufficient attention to non-livestock sectors, inadequate regulation and enforcement capacity, and resource constraints have hindered scalable and sustainable interventions under the current plan. This assessment provides valuable insights to strengthen the inclusiveness and contribution of the agrifood sectors in the next NAP iteration. In the short-to-medium term, strategic prioritization is necessary to optimize the use of limited resources and target the most critical gaps, such as improving awareness among key stakeholders and fortifying regulations for prudent antimicrobial use. In the long term, integration of AMR into the country's broader health, development, and agricultural transformation agendas will be needed to generate sustainable benefits.

Unsupervised clustering to differentiate rheumatoid arthritis patients based on proteomic signatures

OBJECTIVE

Patients with rheumatoid arthritis (RA) have different presentations and prognoses. Cluster analysis based on proteomic signatures creates independent phenogroups of patients with different pathophysiological backgrounds. We aimed to identify distinct pathophysiological clusters of RA patients based on circulating proteomic biomarkers.

METHOD

This was a cohort study including 399 RA patients. Clustering was performed on 94 circulating proteins (92 CVDII Olink®, high-sensitivity troponin T, and C-reactive protein). Unsupervised clustering was performed using a partitioning cluster algorithm.

RESULTS

The clustering algorithm identified two distinct clusters: cluster 1 (n = 223) and cluster 2 (n = 176). Compared with cluster 1, cluster 2 included older patients with a higher burden of comorbidities (cardiovascular and RA related), more erosive and longer RA duration, more dyspnoea and fatigue, walking a shorter distance in the Six-Minute Walk Test, with more severe diastolic dysfunction, and a 4.5-fold higher risk of death or hospitalization for cardiovascular reasons. Tumour necrosis factor (TNF) receptor superfamily-related pathways were mainly responsible for the model's discriminative ability.

CONCLUSION

Using unsupervised cluster analysis based on proteomic phenotypes, we identified two clusters of RA patients with distinct biomarkers profiles, clinical characteristics, and different outcomes that could reflect different pathophysiological backgrounds. TNF receptor superfamily-related proteins may be used to distinguish subgroups.

Association of heart rate with heart failure outcomes and the effects of empagliflozin in patients with preserved ejection fraction – EMPEROR-Preserved trial

Background and objective

High resting heart rate (HR) associates with cardiovascular death (CVD) and heart failure hospitalisation (HFH) in patients with reduced ejection fraction (HFrEF), but data are sparse in patients with preserved (HFpEF) or mildly reduced (HFmrEF) ejection fraction. Empagliflozin reduced the risk of CVD and HFH in HFpEF in the EMPEROR-Preserved trial. This study analyses the influence of HR on outcomes in patients with left ventricular ejection fraction (LVEF) >40% in EMPEROR-Preserved and evaluates the effects of empagliflozin across HR categories.

Methods

Patients (n=5988) with HFpEF (LVEF >40%) were categorised to HR <70 beats per minute (bpm), 70–75 bpm and >75 bpm. The composite of CVD or HFH (primary outcome), first HFH, CVD, recurrent HFH and all-cause mortality were studied in the HR groups and in patients separated by sinus rhythm (SR) or atrial fibrillation (AF) and true HFpEF (EF ≥50%) or HFmrEF (EF 40–49%).

Results

Empagliflozin did not influence HR over time. At HR >75 bpm, the primary outcome (hazard ratio: 1.31, 1.13–1.52, p=0.0003), time to first HFH (hazard ratio: 1.25, 1.04–1.49, p=0.02), recurrent HFH (hazard ratio: 1.29, 1.05–1.60, p=0.02), CVD (hazard ratio: 1.49, 1.21–1.84, p=0.0001) and all-cause mortality (hazard ratio: 1.49, 1.28–1.73, p<0.0001) were increased compared to HR of <70 bpm with HR 70–75 bpm showing intermediate results. The influence of HR on the primary outcome was only observed in SR (p trend=0.005), but not in AF (p trend=0.55). Patients with true HFpEF (≥50%) or HFmrEF (40–49%) showed similar effects. The treatment effects of empagliflozin to reduce the primary outcome, time to first HFH and recurrent HFH were not modified by HR.

Conclusions

HR in SR, but not in AF, predicts heart failure outcomes in HFpEF and HFmrEF, but the effects of empagliflozin were not modified by HR.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Boehringer Ingelheim & Eli Lilly and Company Diabetes Alliance

Achieving Antimicrobial Stewardship on the Global Scale: Challenges and Opportunities

Antimicrobial resistance (AMR) has been clearly identified as a major global health challenge. It is a leading cause of human deaths and also has a toll on animals, plants, and the environment. Despite the considerable socio-economic impacts, the level of awareness of the problem remains woefully inadequate, and antimicrobials are not generally recognized as a global common good, one that everyone has a role and responsibility to conserve. It is imperative for antimicrobial stewardship to be more widely implemented to achieve better control of the AMR phenomenon. The Food and Agriculture Organization (FAO) of the United Nations plays an important role in promoting and facilitating antimicrobial stewardship. The specific needs to be addressed and barriers to be overcome, in particular, in low- and middle-income countries in order to implement antimicrobial stewardship practices in agrifood systems are being identified. As a global community, it is essential that we now move beyond discussing the AMR problem and focus on implementing solutions. Thus, FAO provides multi-pronged support for nations to improve antimicrobial stewardship through programs to strengthen governance, increase awareness, develop and enhance AMR surveillance, and implement best practices related to antimicrobial resistance in agrifood systems. For example, FAO is developing a platform to collect data on AMR in animals and antimicrobial use (AMU) in plants (InFARM), working on a campaign to reduce the need to use antimicrobials, studying the use of alternatives to the use of antimicrobials (especially those used for growth promotion) and actively promoting the implementation of the Codex Alimentarius AMR standards. Together, these will contribute to the control of AMR and also bring us closer to the achievement of multiple sustainable development goals.

Impact of changes in weight and haematocrit on the reduction in systolic office and ambulatory blood pressure with empagliflozin in patients with type 2 diabetes

Background

There is uncertainty on how empagliflozin (EMPA) reduces blood pressure (BP), and in particular the potential role for changes in weight and haematocrit in mediating these effects.

Purpose

To assess the contributions of changes in weight and haematocrit on EMPA induced changes in BP in patients with type 2 diabetes mellitus (T2DM) in the EMPA-BP and EMPA-REG OUTCOME trials.

Methods

Patients received placebo (PBO), EMPA 10 mg or EMPA 25 mg. In EMPA-BP (12-week study), 823 patients with T2DM and hypertension (mean [SD] age 60.2 [9.0] years, HbA1c 7.90 [0.74] %, BMI 32.6 [5.1] kg/m2) were studied. In EMPA-REG OUTCOME, of the 7,020 treated patients with T2DM and cardiovascular disease (mean [SD] age 63.1 [8.6] years, HbA1c 8.07 [0.85] %, BMI 30.6 [5.3] kg/m2), 95.0% were on anti-hypertensive treatment at baseline. ANCOVA/MMRM models were applied to assess changes in systolic BP (SBP) at week 12 associated with, and independent of, changes in weight and haematocrit (Hct). SBP measurements are based on mean 24-h measurements from an ambulatory blood pressure monitoring (ABPM) device in EMPA-BP and seated office measurements in EMPA-REG OUTCOME.

Results

Mean (SD) baseline SBP was 131.7 (11.8), 131.3 (13.0) and 131.2 (12.1) mmHg in the PBO, EMPA 10 mg and EMPA 25 mg groups, respectively in EMPA-BP (mean 24-h SBP) and 135.8 (17.2), 134.9 (16.8) and 135.6 (17.0) mmHg (office SBP), respectively in EMPA-REG OUTCOME. In these relatively young patients with T2DM and mildly elevated mean SBP, EMPA reduced mean SBP by 3.4–4.2 mmHg compared with PBO (table) at week 12. Mean (SE) weight was reduced with EMPA (10 and 25mg) vs PBO treatment by −1.5 (0.2) kg and −2.0 (0.2) kg in EMPA-BP and by −1.2 (0.1) kg and −1.5 (0.1) kg in EMPA-REG OUTCOME at week 12. Mean (SE) haematocrit was increased by 2.1 (0.2) % and 1.8 (0.2) % versus placebo in EMPA-BP and by 2.2 (0.1) % and 2.5 (0.1) % in EMPA-REG OUTCOME with EMPA 10 mg and EMPA 25 mg, respectively. Weight loss accounted for 21–24% of the SBP reduction with EMPA treatment in EMPA-BP and 9–11% in EMPA-REG OUTCOME. Changes in Hct accounted for negligible (between −10% to 1%) SBP reduction with EMPA.

Conclusion

The reduction in SBP is modestly mediated through a reduction in weight. There was no meaningful effect of EMPA induced changes in Hct on SBP. Results were consistent using ABPM or office SBP. These findings suggest that EMPA's effects on SBP are likely mediated through other mechanisms such as natriuresis or reduction in arterial stiffness.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Boehringer Ingelheim and Eli Lilly and Company. Table 1

Setting the standard: multidisciplinary hallmarks for structural, equitable and tracked antibiotic policy

There is increasing concern globally about the enormity of the threats posed by antimicrobial resistance (AMR) to human, animal, plant and environmental health. A proliferation of international, national and institutional reports on the problems posed by AMR and the need for antibiotic stewardship have galvanised attention on the global stage. However, the AMR community increasingly laments a lack of action, often identified as an 'implementation gap'. At a policy level, the design of internationally salient solutions that are able to address AMR's interconnected biological and social (historical, political, economic and cultural) dimensions is not straightforward. This multidisciplinary paper responds by asking two basic questions: (A) Is a universal approach to AMR policy and antibiotic stewardship possible? (B) If yes, what hallmarks characterise 'good' antibiotic policy? Our multistage analysis revealed four central challenges facing current international antibiotic policy: metrics, prioritisation, implementation and inequality. In response to this diagnosis, we propose three hallmarks that can support robust international antibiotic policy. Emerging hallmarks for good antibiotic policies are: Structural, Equitable and Tracked. We describe these hallmarks and propose their consideration should aid the design and evaluation of international antibiotic policies with maximal benefit at both local and international scales.

Monitoring of Farm-Level Antimicrobial Use to Guide Stewardship: Overview of Existing Systems and Analysis of Key Components and Processes

The acknowledgment of antimicrobial resistance (AMR) as a major health challenge in humans, animals and plants, has led to increased efforts to reduce antimicrobial use (AMU). To better understand factors influencing AMR and implement and evaluate stewardship measures for reducing AMU, it is important to have sufficiently detailed information on the quantity of AMU, preferably at the level of the user (farmer, veterinarian) and/or prescriber or provider (veterinarian, feed mill). Recently, several countries have established or are developing systems for monitoring AMU in animals. The aim of this publication is to provide an overview of known systems for monitoring AMU at farm-level, with a descriptive analysis of their key components and processes. As of March 2020, 38 active farm-level AMU monitoring systems from 16 countries were identified. These systems differ in many ways, including which data are collected, the type of analyses conducted and their respective output. At the same time, they share key components (data collection, analysis, benchmarking, and reporting), resulting in similar challenges to be faced with similar decisions to be made. Suggestions are provided with respect to the different components and important aspects of various data types and methods are discussed. This overview should provide support for establishing or working with such a system and could lead to a better implementation of stewardship actions and a more uniform communication about and understanding of AMU data at farm-level. Harmonization of methods and processes could lead to an improved comparability of outcomes and less confusion when interpreting results across systems. However, it is important to note that the development of systems also depends on specific local needs, resources and aims.

OIE Annual Report on Antimicrobial Agents Intended for Use in Animals: Methods Used

For over two decades, the World Organisation for Animal Health (OIE) has engaged in combatting antimicrobial resistance (AMR) through a One Health approach. Monitoring of antimicrobial use (AMU) is an important source of information that together with surveillance of AMR can be used for the assessment and management of risks related to AMR. In the framework of the Global Action Plan on AMR, the OIE has built a global database on antimicrobial agents intended for use in animals, supported by the Tripartite (World Health Organization (WHO), Food and Agriculture Organization of the United Nations (FAO) and OIE) collaboration. The OIE launched its first annual data collection in 2015 and published the Report in 2016. The second Report, published in 2017, introduced a new methodology to report quantitative data in the context of relevant animal populations, and included for the first time an annual analysis of antimicrobial quantities adjusted for animal biomass on a global and regional level. A continuing annual increase of countries participating in the data collection demonstrates the countries engagement for the global development of monitoring and surveillance systems in line with OIE international standards. Where countries are not yet able to contribute their quantitative data, their reports also highlight the barriers that impede them in data collection, analysis and/or reporting. The OIE Reports show annual global and regional estimates of antimicrobial agents intended for use in animals adjusted for animal biomass, as represented by the quantitative data reported by countries to the OIE. The OIE advises caution in interpretation of estimates made in the first few years of reporting recognizing some important limitations faced by countries as they develop their monitoring systems. The OIE remains strongly committed to supporting its Members in developing robust and transparent measurement and reporting mechanisms for AMU.

The Role of Physical Frailty Independent Components on Increased Disabilities in Institutionalized Older Women

The purpose of this study was to identify the independent components of physical frailty that most influence disability indicators in institutionalized older women. A cross-sectional study with 319 participants (81.96±7.89 years old) was performed. Disability was assessed through dynamic and static balance tests, activities of daily life and falls risk screen. Fried physical frailty protocol was used to access physical frailty. The frail subgroup displayed the weakest results for all disability indicators (p < 0.05). Regression analysis showed that in the two models tested, low physical activity levels and slowness were the physical frailty independent components that better associated with the disability indicators. More studies with larger samples will help to better understand the independent relationship of each physical frailty component with disability outcomes and assist to design a co-adjuvant treatment to reverse physical frailty.

Antimicrobial resistance and antimicrobial use animal monitoring policies in Europe: Where are we ?

The World Health Organization has recognized antimicrobial resistance as one of the top three threats to human health. Any use of antibiotics in animals will ultimately affect humans and vice versa. Appropriate monitoring of antimicrobial use and resistance has been repeatedly emphasized along with the need for global policies. Under the auspices of the European Union research project, EFFORT, we mapped antimicrobial use and resistance monitoring programs in ten European countries. We then compared international and European guidelines and policies. In resistance monitoring, we did not find important differences between countries. Current resistance monitoring systems are focused on food animal species (using fecal samples). They ignore companion animals. The scenario is different for monitoring antibiotics use. Recently, countries have tried to harmonize methodologies, but reporting of antimicrobial use remains voluntary. We therefore identified a need for stronger policies.

Decreased muscle strength is associated with proinflammatory cytokines but not testosterone levels in men with diabetes

The aim of this study was to compare muscle strength in male subjects with type 2 diabetes mellitus (DM2) with and without low plasma testosterone levels and assess the relationship between muscle strength, testosterone levels, and proinflammatory cytokines. Males (75) aged between 18 and 65 years were divided into 3 groups: control group that did not have diabetes and had a normal testosterone plasma level (>250 ng/dL), DnormalTT group that had DM2 with normal testosterone levels, and the DlowTT group that had DM2 and low plasma testosterone levels (<250 ng/dL). The age (means±SD) of the groups was 48.4±10, 52.6±7, and 54.6±7 years, respectively. Isokinetic concentric and isometric torque of knee flexors and extensors were analyzed by an isokinetic dynamometer. Plasma testosterone and proinflammatory cytokine levels were determined by chemiluminescence and ELISA, respectively. Glycemic control was analyzed by glycated hemoglobin (HbA1C). In general, concentric and isometric torques were lower and tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β plasma levels were higher in the groups with diabetes than in controls. There was no correlation between testosterone level and knee torques or proinflammatory cytokines. Concentric and isometric knee flexion and extension torque were negatively correlated with TNF-α, IL-6, and HbA1C. IL-6 and TNF-α were positively correlated with HbA1C. The results of this study demonstrated that muscle strength was not associated with testosterone levels in men with DM2. Low muscle strength was associated with inflammatory markers and poor glycemic control.

Quantitative Outcomes of a One Health approach to Study Global Health Challenges

Having gained momentum in the last decade, the One Health initiative promotes a holistic approach to address complex global health issues. Before recommending its adoption to stakeholders, however, it is paramount to first compile quantitative evidence of the benefit of such an approach. The aim of this scoping review was to identify and summarize primary research that describes monetary and non-monetary outcomes following adoption of a One Health approach. An extensive literature search yielded a total of 42,167 references, of which 85 were included in the final analysis. The top two biotic health issues addressed in these studies were rabies and malaria; the top abiotic health issue was air pollution. Most studies described collaborations between human and animal (n = 42), or human and environmental disciplines (n = 41); commonly reported interventions included vector control and animal vaccination. Monetary outcomes were commonly expressed as cost-benefit or cost-utility ratios; non-monetary outcomes were described using disease frequency or disease burden measurements. The majority of the studies reported positive or partially positive outcomes. This paper illustrates the variety of health challenges that can be addressed using a One Health approach, and provides tangible quantitative measures that can be used to evaluate future implementations of the One Health approach.

Why Antibiotic Use Data in Animals Needs to Be Collected and How This Can Be Facilitated

Antimicrobial resistance (AMR) is currently recognized as one of the most significant threats to public health worldwide. It is a phenomenon that highlights the interconnectivity between human and animal health since any use of antibiotics in humans can eventually lead to resistance in the microbial populations colonizing animals and vice versa. In recent years, our understanding of the relationship between the use of antibiotics and the consequent development of resistance in microbial populations to these (or similar) antibiotics has increased. Having accurate data, ideally in a digital format, on the use of antibiotics are therefore of paramount importance. Current obstacles to having such data include, among others, the lack of consensual and harmonized technical methods and units that represent antimicrobial use (AMU), the insufficient incentives to motivate primary producers to report their use of antibiotics, and the inexistence of user-friendly technologies for the collection of such data, despite the generalized use of Internet and electronic devices. Further development and adoption of the units proposed by the European Surveillance of Veterinary Antimicrobial Consumption will contribute to the long-desired harmonization. Rewarding the animal producers (via tax incentives, for example) that use less antibiotics and the development of an app, to which producers could orally report the used antibiotics are among the solutions that could help to overcome the current challenges. I here also argue that having mandatory electronic veterinary prescriptions and awareness campaings, funded via public-private partnerships, should also be considered as methods that could help for the control of societal problems like AMR.

Contribution to the characterization of Opuntia spp. juices by LC-DAD-ESI-MS/MS

Opuntia spp. fruits are considered as health promoting foods due to the diversity of bioactive molecules found in these fruits. The composition in organic acids, flavonols and betalains in the Opuntia ficus-indica juice from a region of Portugal was accomplished for the first time by liquid chromatography and tandem mass spectrometry using an electrospray ionization source operating in negative and positive mode. The methodology used allowed the detection of 44 compounds, from which 32 were identified. Isorhamnetin derivatives were the dominant flavonol glycosides. A total of 9 betalains including 6 betaxanthins and 3 betacyanin were also detected in the fruit juice samples and indicaxanthin, betanin and isobetanin were the major pigments. Phenolic acid and phenylpyruvic acid derivatives were also identified. To our knowledge, it is the first time derivative compounds from piscidic acid, phenolic compounds and betalains are characterized in cactus pear juice using a single LC-DAD-ESI-MS/MS method.

Transmission of MRSA between companion animals and infected human patients presenting to outpatient medical care facilities

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in both human and veterinary medicine. The importance of companion animals as reservoirs of human infections is currently unknown. The companion animals of 49 MRSA-infected outpatients (cases) were screened for MRSA carriage, and their bacterial isolates were compared with those of the infected patients using Pulsed-Field Gel Electrophoresis (PFGE). Rates of MRSA among the companion animals of MRSA-infected patients were compared to rates of MRSA among companion animals of pet guardians attending a “veterinary wellness clinic” (controls). MRSA was isolated from at least one companion animal in 4/49 (8.2%) households of MRSA-infected outpatients vs. none of the pets of the 50 uninfected human controls. Using PFGE, patient-pets MRSA isolates were identical for three pairs and discordant for one pair (suggested MRSA inter-specie transmission p-value = 0.1175). These results suggest that companion animals of MRSA-infected patients can be culture-positive for MRSA, representing a potential source of infection or re-infection for humans. Further studies are required to better understand the epidemiology of MRSA human-animal inter-specie transmission.

Microparticles for delivering therapeutic peptides and proteins to the lumen of the small intestine

Several different peptides and proteins, such as the pancreatic trypsin inhibitor, growth factors and trefoil peptides, are known to play important roles in maintaining the structure and function of the gastrointestinal wall. With the advent of recombinant biotechnology, it has become feasible to test some of these proteins as therapeutics in different inflammatory conditions of the intestines. However, the harsh pH and enzymatic conditions of the stomach can lead to their inactivation. This research was aimed at the development of particulate, gastric-resistant pharmaceutical forms, incorporating those bioactive molecules. Mixtures of proteins in powder form were coated with cellulose acetate phthalate, Eudragit S100 or Eudragit RS PO, using simple preparation techniques based on single emulsion/solvent evaporation. Using aprotinin as a model drug, it was found that these procedures were effective in microencapsulating protein in the solid form without affecting its biological activity. Furthermore, and in particular with the first two polymers above, particles showed adequate in vitro release patterns for the applications envisioned.

Effect of drug properties on the release from CAP microspheres prepared by a solvent evaporation method

Drugs with different water-solubility and molecular weights were microencapsulated in cellulose acetate phthalate, using an emulsion-solvent evaporation technique with a continuous oil-phase. The mean size of the particles was approximately 600 microns, and they were non-porous. The capacity of the microspheres to retain the drugs was evaluated by in vitro release studies in acidic medium. For low molecular weight compounds the release rates increased with solubility: for thiamin hydrochloride and phenacetin, a highly and a poorly soluble compound respectively, the percentages released at 60 min were 90 and 10%. Drugs with molecular weights above approximately 700 Da were retained in the microspheres. The above dependence on solubility was corroborated by release studies in ethanol, and by modelling the release of phenacetin in acidic media. Microspheres with a different polymer matrix, Eudragit RS PO, were also prepared by a similar technique, and these particles prolonged the release of thiamin for over 6 h, under simulated GI conditions.

Study of an anti-human transthyretin immunoadsorbent. Influence of coupling chemistry on binding capacity and ligand leakage

A variant of transthyretin (TTR Val30Met) has been identified as the main protein precursor of the amyloid fibrils deposited in familial amyloidotic polyneuropathy (FAP). Specific removal of TTR in an extracorporeal immunoadsorption procedure is currently under investigation as a possible treatment of FAP. Immunoadsorbents were constructed by immobilizing murine anti-TTR monoclonal antibody 88.6.BA9 onto agarose gel supports via several different coupling chemistries. The influence of coupling conditions such as pH and antibody density, and of perfusion variables, such as antigen concentration and applied flow-rate, on the TTR capture efficiency, was determined. Cyanogen bromide-, carbonyldiimidazole- and aldehyde-activated (ALD) supports conjugated with antibody at optimal pH, provided immunoadsorbents with comparable TTR binding capacities. Regarding stability, leakage was lowest for the ALD based immunoadsorbents, particularly at high pH.

A study on the functional subunits of phospholipases A2 by enzyme immobilization

Pancreatic and venom phospholipases A2 have complex and distinct oligomerization behaviour. Pancreatic enzymes are monomeric in solution, but their quaternary structure at interfaces is unknown. On the other hand, certain crotalid venom phospholipases A2 are dimeric in solution, and different reports have proposed either the monomer or the dimer as the catalytically functional subunit. In this study, enzyme immobilization was used as a tool for determining the functional subunits of these enzymes. The dimeric Crotalus atrox phospholipase A2 was covalently attached to agarose beads, via either the amine or the carboxylic groups of the protein. In the first case immobilization led to an 80% loss of activity as compared with the soluble form, and measured by using micellar diheptanoylphosphocholine. Inclusion of micellar protectants in the coupling media did not improve the activity. Enzyme immobilized via carboxylic groups was 2-3-fold more active than the amine-coupled form. In a second approach, Crotalus atrox enzyme was immobilized with single-subunit attachment. The removal, with denaturating washes, of the non-covalently bound units involved in monomer-monomer interactions, caused a large decrease in specific activity of the support-bound enzyme. This suggests the dimeric form as the fully active one. Similar procedures were also carried out with pig pancreatic and Naja naja phospholipases A2. The results indicated that these enzymes are active as monomers.

Carbodiimide modification enhances activity of pig pancreatic phospholipase A2

Pig phospholipase A2, pig iso-phospholipase A2 and bovine pancreatic phospholipase A2 were reacted in solution with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, in the presence of N-hydroxysulfosuccinimide, at pH 7. The influence of micellar protectants was analyzed. In the presence of n-hexadecylphosphocholine, the losses of activity in micellar diheptanoyl-lecithin were 80, 35, and 10% in bovine phospholipase A2, pig iso-phospholipase A2, and pig phospholipase A2, respectively. With 1-oleoylglycerophosphocholine, the bovine enzyme lost 40% activity, but the pig enzyme was activated sevenfold. The modified pig enzyme showed pre-micellar activation on monomeric diheptanoyl-lecithin, and either reduced or increased activities on mixed micelles of bile salt with egg phosphatidylcholine, depending on the composition of the micelles. This activation is consistent with previous protein-engineering studies of pig pancreatic phospholipase A2. In this study, we present new information concerning the specificity and interfacial recognition behaviour of this enzyme in relation to this activation.

[Acute meningoencephalitis caused by non-poliomyelitic enterovirus]

Enterovirus are ubiquitous pathogenic agents, whose only hosts are human. Their protean clinical presentation does not allow an etiological diagnosis grounded only on clinical basis. Despite their known neurotropism, a symptomatic infection of the central nervous system is not the rule. Nevertheless, with the ecological changes induced by the viral vaccines introduced during the last decades and the frequency of infection by these agents, especially among children, non-poliomyelitic enterovirus assume a major role as a cause of viral meningitis and encephalitis in the paediatric age. The epidemiological and clinical context should rule the request of serologic tests to achieve a final diagnosis.

Influence of chemistry in immobilization of cobra venom phospholipase A2: implications as to mechanism

Phospholipase A2 from Naja naja kaouthia venom was covalently coupled onto agarose beads using two different chemistries. The effect of micellar competitive inhibitors in the coupling media was evaluated. Enzyme bound to N-hydroxysuccinimide-activated agarose, which is reactive primarily toward epsilon-amino groups, had 20% activity retention against micellar diheptanoylphosphatidylcholine (DiC7-PC). Enzyme bound through carboxylic groups, using a modification of the carbodiimide method, had 50% retention. Similar relative activities were observed, for both conjugates, in monomeric dihexanoyl-PC and in mixed micelles of Triton X-100 with dipalmitoyl-PC or dioleoylphosphatidylethanolamine. The soluble form of the enzyme showed premicellar activation against monomeric DiC7-PC, while the immobilized form showed interfacial recognition at concentrations around the critical micellar concentration. These results suggest that the enzyme activity lost upon immobilization is a result of the inherent chemical modification of the enzyme and that enzyme oligomerization and interfacial recognition are not cause-effect phenomena.

Enzymatic modification of plasma low density lipoproteins in rabbits: a potential treatment for hypercholesterolemia

Phospholipase A2 (EC 3.1.1.4) hydrolyzes certain phospholipids of low density lipoprotein (LDL). Plasma clearance of phospholipase A2-modified human LDL is up to 17 times faster than that of native human LDL in hypercholesterolemic rabbits. Modification of blood lipoproteins of hypercholesterolemic rabbits was performed by using an extracorporeal circuit containing immobilized phospholipase A2. After 90-min treatments, nearly 30% decreases in plasma cholesterol concentrations were observed. Erythrocyte, leukocyte, and platelet counts showed no net change after treatment. This technique does not require any fluid replacement or sorbent regeneration and offers a potential approach for lowering serum cholesterol and LDL levels.