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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Correction: Free fatty acid release from vegetable and bovine milk fat-based infant formulas and human milk during two-phase: In vitro digestion
Hageman, Jeske H.J. ; Keijer, Jaap ; Dalsgaard, Trine Kastrup ; Zeper, Lara W. ; Carrière, Frédéric ; Feitsma, Anouk L. ; Nieuwenhuizen, Arie G. - \ 2019
Food & Function 10 (2019)5. - ISSN 2042-6496 - p. 3018 - 3020.

The authors regret that the lipid composition of IF1 was reported incorrectly. The percentage of C18:1n-9 should be 42.3%. Since the incorrect value was also used for some calculations, this also affects some of the results: it increases the total amount of fatty acids in the sample, and consequently the percentage of released FFA is lower. The FFA release (as a percentage of initial composition), both of total FFA and C18:1, is similar for both IFs. One small difference between IF1 and IF2 that was seen when using the incorrect value, i.e. a faster early duodenal digestion for IF1, was found to be no longer statistically significant. This has no consequences for the conclusions of the manuscript. Page 2106 should read " The human milk samples showed less release of FFA during the gastric phase compared to IF1 and IF2 (2.0 ± 0.2% vs. 4.3 ± 0.2% and 4.7 ± 0.1% respectively, p < 0.01). Compared to the amount of FFA released after the digestion, during the gastric phase 4% of FFA were released from human milk, about 10% from IF1, and about 11% from IF2. Except for 45 minutes (p = 0.04), i.e. 15 minutes after the start of the duodenal phase, no differences were found in FFA release between the IFs compared to the human milk samples during this phase. The total release of FAs at the end of the digestion, as percentage of initial composition, was found to be similar for the different samples (43.9 ± 2.0%, 42.2 ± 1.4%, and 52.3 ± 4.5% for IF1, IF2 and human milk respectively, p = 0.14)". The correspondingly updated Fig. 2B, Fig. 5K, Table 2 and Table 3 are as presented below.(Table Persented).

Biogeography of the fish pathogen Aeromonas salmonicida inferred by vapA genotyping
Gulla, Snorre ; Bayliss, Sion ; Björnsdóttir, Bryndís ; Dalsgaard, Inger ; Haenen, Olga ; Jansson, Eva ; McCarthy, Una ; Scholz, Felix ; Vercauteren, Maaike ; Verner-Jeffreys, David ; Welch, Tim ; Wiklund, Tom ; Colquhoun, Duncan J. - \ 2019
FEMS Microbiology Letters 366 (2019)7. - ISSN 0378-1097
Aeromonas salmonicida - aquaculture - bacterial fish pathogen - genotyping - host specificity - vapA/A-layer

A recently described typing system based on sequence variation in the virulence array protein (vapA) gene, encoding the A-layer surface protein array, allows unambiguous subtyping of Aeromonas salmonicida. In the present study, we compile A-layer typing results from a total of 675 A. salmonicida isolates, recovered over a 59-year period from 50 different fish species in 26 countries. Nine novel A-layer types (15-23) are identified, several of which display a strong predilection towards certain fish hosts, including e.g. Cyprinidae and Pleuronectidae species. Moreover, we find indications that anthropogenic transport of live fish may have aided the near global dissemination of two cyprinid-associated A-layer types. Comparison of whole genome phylogeny and A-layer typing for a subset of strains further resulted in compatible tree topologies, indicating the utility of vapA as a phylogenetic as well as an epizootiological marker in A. salmonicida. A Microreact project (microreact.org/project/r1pcOAx9m) has been created, allowing public access to the vapA analyses and relevant metadata. In sum, the results generated provide valuable insights into the global population structure of A. salmonicida, particularly in relation to its piscine host spectrum and the geographic distribution of these hosts.

Free fatty acid release from vegetable and bovine milk fat-based infant formulas and human milk during two-phase in vitro digestion
Hageman, Jeske H.J. ; Keijer, Jaap ; Dalsgaard, Trine Kastrup ; Zeper, Lara W. ; Carrière, Frédéric ; Feitsma, Anouk L. ; Nieuwenhuizen, Arie G. - \ 2019
Food & Function 10 (2019)4. - ISSN 2042-6496 - p. 2102 - 2113.

Background: Bovine milk fat is increasingly used in infant formula (IF). The triacylglycerol (TAG) structure of bovine milk fat might be beneficial for digestion and absorption. We investigated the release of fatty acids (FAs) of IF containing different fat blends and compared this to human milk. Methods: Fresh human milk was sampled and two IFs were produced; one containing 100% vegetable fat (IF1) and one with 67% bovine milk fat and 33% vegetable fat (IF2). Using a static in vitro infant digestion model, consisting of a gastric and duodenal phase, the time dependent release of individual free fatty acids (FFA) was studied and analysed using GC-MS, and residual TAG levels were determined by GC-FID. Results: Human milk and the IFs showed comparable total FA release. In the gastric phase, 4-11% of lipolysis occurred, and mainly short (SCFA)- and medium chain fatty acids (MCFA) were released. In the duodenal phase, lipolysis proceeded with release of C4:0 but was marked by a fast release of long-chain fatty acids (LCFA). The digestion of the IFs resulted in different FFA profiles during and at the end of digestion. IF2 gave more release of C4:0-C11:0, which reflects the FA composition of bovine milk. Conclusion: The addition of bovine milk fat to IF resulted in a total FA release comparable to an IF with only vegetable fat and human milk. However, it did lead to a different time-dependent release of individual FAs, which might result in differences in absorption and other health effects in vivo.

Comparison of bovine milk fat and vegetable fat for infant formula : Implications for infant health
Hageman, Jeske H.J. ; Danielsen, Marianne ; Nieuwenhuizen, Arie G. ; Feitsma, Anouk L. ; Dalsgaard, Trine K. - \ 2019
International Dairy Journal 92 (2019). - ISSN 0958-6946 - p. 37 - 49.

Fat is an important component of human milk and infant formula (IF), delivering half of the energy a baby needs. Nowadays, mostly vegetable fats are used in IFs; however, the use of bovine milk fat in formulas is currently increasing. Bovine milk fat contains a composition of fatty acids and lipid components different from those of vegetable fats. We have compared the lipid profile of human and bovine milk with infant formulas with different fat sources. Furthermore, current knowledge of how infant digestion, absorption, metabolic responses, gut immunity, microbiota and/or cognition is affected by dietary fat is reviewed. The possible opportunities and drawbacks of the application of bovine milk fat in infant nutrition are described. Future perspectives for the development of IF containing bovine milk fat and future research directions are highlighted.

Mapping topsoil organic carbon concentrations and stocks for Tanzania
Kempen, Bas ; Dalsgaard, Soren ; Kaaya, Abel K. ; Chamuya, Nurdin ; Ruiperez Gonzalez, Maria ; Pekkarinen, Anssi ; Walsh, Markus G. - \ 2019
Geoderma 337 (2019). - ISSN 0016-7061 - p. 164 - 180.
Tanzania is one of the countries that has embarked on a national programme under the United Nations collaborative initiative on Reducing Emissions from Deforestation and forest Degradation (REDD). Tanzania is currently developing the capacity to enter into a carbon monitoring REDD+ regime. In this context spatially representative soil carbon datasets and accurate predictive maps are important for determining the soil organic carbon pool. The main objective of this study was to model and map the SOC stock for the 0–30-cm soil layer to provide baseline information for REDD+ purposes. Topsoil data of over 1400 locations spread throughout Tanzania from the National Forest Monitoring and Assessment (NAFORMA), were used, supplemented by two legacy datasets, to calibrate simple kriging with varying local means models. Maps of SOC concentrations (g kg−1) were generated for the 0–10-cm, 10–20-cm, 20–30-cm, 0–30-cm layers, and maps of bulk density and SOC stock (kg m−2) for the 0–30-cm layer. Two approaches for modelling SOC stocks were considered here: the calculate-then-model (CTM) approach and the model-then-calculate approach (MTC). The spatial predictions were validated by means of 10-fold cross-validation. Uncertainty associated to the estimated SOC stocks was quantified through conditional Gaussian simulation. Estimates of SOC stocks for the main land cover classes are provided. Environmental covariates related to soil and terrain proved to be the strongest predictors for all properties modelled. The mean predicted SOC stock for the 0–30-cm layer was 4.1 kg m−2 (CTM approach) translating to a total national stock of 3.6 Pg. The MTC approach gave similar results. The largest stocks are found in forest and grassland ecosystems, while woodlands and bushlands contain two thirds of the total SOC stock. The root mean squared error for the 0–30-cm layer was 1.8 kg m−2, and the R2-value was 0.51. The R2-value of SOC concentration for the 0–30-cm layer was 0.60 and that of bulk density 0.56. The R2-values of the predicted SOC concentrations for the 10-cm layers vary between 0.46 and 0.54. The 95% confidence interval of the predicted average SOC stock is 4.01–4.15 kg m−2, and that of the national total SOC stock 3.54–3.65 Pg. Uncertainty associated with SOC concentration had the largest contribution to SOC stock uncertainty. These findings have relevance for the ongoing REDD+ readiness process in Tanzania by supplementing the previous knowledge of significant carbon pools. The soil organic carbon pool makes up a relatively large proportion of carbon in Tanzania and is therefore an important carbon pool to consider alongside the ones related to the woody biomass. Going forward, the soil organic carbon data can potentially be used in the determination of reference emission levels and the future monitoring, reporting and verification of organic carbon pools.
In vitro digestion of infant formula containing cow's milk fat and vegetable fat
Hageman, Jeske ; Carrière, Frédéric ; Dalsgaard, Trine K. ; Feitsma, Anouk ; Nieuwenhuizen, A.G. ; Keijer, J. - \ 2017
An evaluation of fish health-management practices and occupational health hazards associated with Pangasius catfish (Pangasianodon hypophthalmus) aquaculture in the Mekong Delta, Vietnam
Phu, Tran Minh ; Phuong, Nguyen Thanh ; Dung, Tu Thanh ; Hai, Dao Minh ; Son, Vo Nam ; Rico Artero, Andreu ; Clausen, Jesper Hedegaard ; Madsen, Henry ; Murray, Francis ; Dalsgaard, Anders - \ 2016
Aquaculture Research 47 (2016)9. - ISSN 1355-557X - p. 2778 - 2794.
Pangasianodon hypophthalmus - Antimicrobials - Catfish - Fish disease - Mekong Delta - Occupational health

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow-out farms producing Pangasius catfish (Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi-structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow-out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small-scale farmers, all large-scale grow-out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small-scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private-public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small-scale grow-out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One-Health approach.

Negligible Impact of Ingested Microplastics on Tissue Concentrations of Persistent Organic Pollutants in Northern Fulmars off Coastal Norway
Herzke, D. ; Anker-Nilssen, T. ; Haughdahl, T. ; Nøst, T. ; Götsch, A. ; Christensen-Dalsgaard, S. ; Langset, M. ; Fangel, K. ; Koelmans, A.A. - \ 2016
Environmental Science and Technology 50 (2016)4. - ISSN 0013-936X - p. 1924 - 1933.
The northern fulmar (Fulmarus glacialis) is defined as an indicator species of plastic pollution by the Oslo-Paris Convention for the North-East Atlantic, but few data exist for fulmars from Norway. Moreover, the relationship between uptake of plastic and pollutants in seabirds is poorly understood. We analyzed samples of fulmars from Norwegian waters and compared the POP concentrations in their liver and muscle tissue with the corresponding concentrations in the loads of ingested plastic in their stomachs, grouped as “no”, “medium” (0.01–0.21 g; 1–14 pieces of plastic), or “high” (0.11–0.59 g; 15–106 pieces of plastic). POP concentrations in the plastic did not differ significantly between the high and medium plastic ingestion group for sumPCBs, sumDDTs, and sumPBDEs. By combining correlations among POP concentrations, differences in tissue concentrations of POPs between plastic ingestion subgroups, fugacity calculations, and bioaccumulation modeling, we showed that plastic is more likely to act as a passive sampler than as a vector of POPs, thus reflecting the POP profiles of simultaneously ingested prey.
Industrial potential of lipoxygenases
Heshof, R. ; Graaff, L.H. de; Villaverde, J.J. ; Silvestre, A.J.D. ; Haarmann, T. ; Dalsgaard, T.K. ; Buchert, J. - \ 2016
Critical Reviews in Biotechnology 36 (2016)4. - ISSN 0738-8551 - p. 665 - 674.
Lipoxygenases (LOXs) are iron- or manganese-containing oxidative enzymes found in plants, animals, bacteria and fungi. LOXs catalyze the oxidation of polyunsaturated fatty acids to the corresponding highly reactive hydroperoxides. Production of hydroperoxides by LOX can be exploited in different applications such as in bleaching of colored components, modification of lipids originating from different raw materials, production of lipid derived chemicals and production of aroma compounds. Most application research has been carried out using soybean LOX, but currently the use of microbial LOXs has also been reported. Development of LOX composition with high activity by heterologous expression in suitable production hosts would enable full exploitation of the potential of LOX derived reactions in different applications. Here, we review the biological role of LOXs, their heterologous production, as well as potential use in different applications. LOXs may fulfill an important role in the design of processes that are far more environmental friendly than currently used chemical reactions. Difficulties in screening for the optimal enzymes and producing LOX enzymes in sufficient amounts prevent large-scale application so far. With this review, we summarize current knowledge of LOX enzymes and the way in which they can be produced and applied
Modeling the relationship between POPs in ingested plastic debris and in tissue of Norwegian Northern Fulmars
Herzke, D. ; Koelmans, A.A. ; Langset, M. ; Christensen-Dalsgaard, S. ; Fangel, K. - \ 2015
Dairy proteins, dairy lipids, and postprandial lipemia in persons with abdominal obesity (DairyHealth) : A 12-wk, randomized, parallel-controlled, double-blinded, diet intervention study
Bohl, Mette ; Bjørnshave, Ann ; Rasmussen, Kia V. ; Schioldan, Anne Grethe ; Amer, Bashar ; Larsen, Mette K. ; Dalsgaard, Trine K. ; Holst, Jens J. ; Herrmann, Annkatrin ; O'Neill, Sadhbh ; O'Driscoll, Lorraine ; Afman, Lydia ; Jensen, Erik ; Christensen, Merete M. ; Gregersen, Søren ; Hermansen, Kjeld - \ 2015
American Journal of Clinical Nutrition 101 (2015)4. - ISSN 0002-9165 - p. 870 - 878.
Abdominal obesity - Adipose tissue gene expression - ApoB-48 - Casein - Dairy - Incretin - Mediumchain saturated fatty acid - Milk fat - Milk protein - Postprandial lipemia - Whey

Background: Abdominal obesity and exaggerated postprandial lipemia are independent risk factors for cardiovascular disease (CVD) and mortality, and both are affected by dietary behavior. Objective: We investigated whether dietary supplementation with whey protein and medium-chain saturated fatty acids (MC-SFAs) improved postprandial lipid metabolism in humans with abdominal obesity. Design: We conducted a 12-wk, randomized, double-blinded, diet intervention study. Sixty-three adults were randomly allocated to one of 4 diets in a 2 3 2 factorial design. Participants consumed 60 g milk protein (whey or casein) and 63 g milk fat (with high or low MCSFA content) daily. Before and after the intervention, a high-fat meal test was performed. We measured changes from baseline in fasting and postprandial triacylglycerol, apolipoprotein B-48 (apoB-48; reflecting chylomicrons of intestinal origin), free fatty acids (FFAs), insulin, glucose, glucagon, glucagon-like peptide 1 (GLP-1), and gastric inhibitory polypeptide (GIP). Furthermore, changes in the expression of adipose tissue genes involved in lipid metabolism were investigated. Two-factor ANOVA was used to examine the difference between protein types and fatty acid compositions, as well as any interaction between the two. Results: Fifty-two participants completed the study. We found that the postprandial apoB-48 response decreased significantly after whey compared with casein (P = 0.025) independently of fatty acid composition. Furthermore, supplementation with casein resulted in a significant increase in the postprandial GLP-1 response compared with whey (P = 0.003). We found no difference in postprandial triacylglycerol, FFA, insulin, glucose, glucagon, or GIP related to protein type or MC-SFA content. We observed no interaction between milk protein and milk fat on postprandial lipemia. Conclusion: We found that a whey protein supplement decreased the postprandial chylomicron response compared with casein in persons with abdominal obesity, thereby indicating a beneficial impact on CVD risk.

Modelling and mapping the topsoil organic carbon content for Tanzania
Kempen, B. ; Kaaya, A.K. ; Ngonyani Mhaiki, C.J. ; Kiluvia, S.K. ; Ruiperez Gonzalez, M. ; Batjes, N.H. ; Dalsgaard, S. - \ 2014
Geophysical Research Abstracts 16 (2014). - ISSN 1029-7006
Soil organic carbon (SOC), held in soil organic matter, is a key indicator of soil health and plays an important
role in the global carbon cycle. The soil can act as a net source or sink of carbon depending on land use and
management. Deforestation and forest degradation lead to the release of vast amounts of carbon from the soil
in the form of greenhouse gasses, especially in tropical countries. Tanzania has a high deforestation rate: it is
estimated that the country loses 1.1% of its total forested area annually. During 2010-2013 Tanzania has been
a pilot country under the UN-REDD programme. This programme has supported Tanzania in its initial efforts
towards reducing greenhouse gas emission from forest degradation and deforestation and towards preserving soil
carbon stocks. Formulation and implementation of the national REDD strategy requires detailed information on
the five carbon pools among these the SOC pool. The spatial distribution of SOC contents and stocks was not
available for Tanzania. The initial aim of this research, was therefore to develop high-resolution maps of the SOC
content for the country.
A novel class of fungal lipoxygenases
Heshof, R. ; Jylhä, S. ; Haarmann, T. ; Jørgensen, A.L.W. ; Dalsgaard, T.K. ; Graaff, L.H. de - \ 2014
Applied Microbiology and Biotechnology 98 (2014)3. - ISSN 0175-7598 - p. 1261 - 1270.
manganese lipoxygenase - cloning - hydroperoxide - stereocontrol - oxygenation - oxylipins - pathway
Lipoxygenases (LOXs) are well-studied enzymes in plants and mammals. However, fungal LOXs are less studied. In this study, we have compared fungal LOX protein sequences to all known characterized LOXs. For this, a script was written using Shell commands to extract sequences from the NCBI database and to align the sequences obtained using Multiple Sequence Comparison by Log-Expectation. We constructed a phylogenetic tree with the use of Quicktree to visualize the relation of fungal LOXs towards other LOXs. These sequences were analyzed with respect to the signal sequence, C-terminal amino acid, the stereochemistry of the formed oxylipin, and the metal ion cofactor usage. This study shows fungal LOXs are divided into two groups, the Ile- and the Val-groups. The Ile-group has a conserved WRYAK sequence that appears to be characteristic for fungal LOXs and has as a C-terminal amino acid Ile. The Val-group has a highly conserved WL-L/F-AK sequence that is also found in LOXs of plant and animal origin. We found that fungal LOXs with this conserved sequence have a Val at the C-terminus in contrast to other LOXs of fungal origin. Also, these LOXs have signal sequences implying these LOXs will be expressed extracellularly. Our results show that in this group, in addition to the Gaeumannomyces graminis and the Magnaporthe salvinii LOXs, the Aspergillus fumigatus LOX uses manganese as a cofactor
Panda WP4: Report on the current best methods for rapid and accurate detection of the main disease hazards in aquaculture, requirements for improvement, their eventual standardisation and validation, and how to achieve harmonised implementation throughout Europe of the best diagnostic methods.
Haenen, O.L.M. ; Dalsgaard, I. ; Bonami, J.R. ; Joly, J.P. ; Olesen, N. ; Bang Jensen, B. ; Ariel, E. ; Miossec, L. ; Arzul, I. - \ 2008
Lelystad : EU - 108 p.
Transmission of fishborne zoonotic parasites in livestock-fish production systems in Vietnam
Boerlage, A.S. ; Jong, M.C.M. de; Dalsgaard, A. ; Verreth, J.A.J. ; Graat, E.A.M. - \ 2008
Antigenic profile of African horse sicknes virus serotype 4 VP5 and identification of a neutralizing epitope shared by bluetongue virus and epizootic hemorrhagic disease virus
Martinez-Torrecuadrada, J.L. ; Langeveld, J.P.M. ; Venteo, A. ; Sanz, A. ; Dalsgaard, K. ; Hamilton, W.D.O. ; Meloen, R.H. ; Casal, J.I. - \ 1999
Virology 257 (1999). - ISSN 0042-6822 - p. 449 - 459.
Mapping the antigenic structure of porcine parvovirus at the level of peptides
Kamstrup, S. ; Langeveld, J. ; Botner, A. ; Nielsen, J. ; Schaaper, W.M.M. ; Boshuizen, R.S. ; Casal, J.I. ; Hojrup, P. ; Vela, C. ; Meloen, R. ; Dalsgaard, K. - \ 1998
Virus Research 53 (1998). - ISSN 0168-1702 - p. 163 - 173.
Edible vaccines
Meloen, R.H. ; Hamilton, W.D.O. ; Casal, J.I. ; Dalsgaard, K. ; Langeveld, J.P.M. - \ 1998
Veterinary Quarterly 20 (1998)SUPPL. 3. - ISSN 0165-2176 - p. S92 - S95.
The ultimate vaccine is an oral vaccine which given once protects against a multitude of diseases. Furthermore this ultimate vaccine needs to be very stable and inexpensive to produce. Probably this latter condition can be met only if the vaccines are produced in plants. Such vaccines are called 'edible vaccines'. Edible vaccines can be produced in plants in many ways. Using recombinant plant-virus, CPMV, it was shown that plants can produce massive amounts of chimaeric virus particles which protect after a single injection the target animal against disease. The final step, oral administration, is being addressed at present. Preliminary experiments by others suggest that this step may be solved sooner than expected.
Antigenic structure of the capsid protein of rabbit haemorrhagic disease virus
Martinez-Torrecuadrada, J.L. ; Cortés, E. ; Vela, C. ; Langeveld, J.P.M. ; Meloen, R.H. ; Dalsgaard, K. ; Hamilton, W.D.O. ; Casal, J.I. - \ 1998
Journal of General Virology 79 (1998). - ISSN 0022-1317 - p. 1901 - 1909.
Synthetic peptide vaccines: palmitoylation of peptide antigens by an thioester bond increases immunogenicity
Beekman, N.J.C.M. ; Schaaper, W.M.M. ; Tesser, G.I. ; Dalsgaard, K. ; Langeveld, J.P.M. ; Boshuizen, R.S. ; Meloen, R.H. - \ 1997
Journal of peptide research 50 (1997)5. - ISSN 1397-002X - p. 357 - 364.
Synthetic peptides have frequently been used to immunize animals. However, peptides less than about 20 to 30 amino acids long are poor immunogens. In general, to increase its immunogenicity, the presentation of the peptide should be improved, and molecular weight needs to be increased. Many attempts have been made to couple peptide immunogens to different carrier proteins [e.g. keyhole limpet haemocyanin (KLH) or ovalbumin]. This leads to very complex structures, however. We used a controlled conjugation of a peptide to a single long-chain fatty acid like palmitic acid by a thioester or an amide bond. It was found that these S-palmitoylated peptides were much more immunogenic than N-palmitoylated peptides and at least similar to KLH-conjugated peptides with respect to appearance and magnitude of induced antibodies (canine parvovirus) or immunocastration effect (gonadotropin-releasing hormone). For chemical synthesis of thioesters, we established conditions for solution and solid-phase synthesis. In both phases, Cys(SBu(t)) could only be deprotected efficiently using phosphines, and S-acylation was accomplished using standard coupling at pH 5. We speculate that, in vivo, the presence of an appropriate fatty acid chain, chemically linked through a labile thioester bond, greatly enhances immunogenicity, because it represents a favourable substrate for cleavage by cellular thioesterases in cells of the immune system.
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