Publications

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2007
Hamza, E., M. Doherr, G. Bertoni, T. W. Jungi, and E. Marti, "Modulation of allergy incidence in Icelandic horses is associated with a change in IL-4-producing T cells", Intern Arch of Allergy and Immunology , vol. 144, pp. 325-337, 2007.
2008
Hamza, E., B. Wagner, T. W. Jungi, J. Mirkovitch, and E. Marti, "Reduced incidence of insect-bite hypersensitivity in Icelandic horses is associated with a down-regulation of interleukin-4 by interleukin-10 and transforming growth factor", Vet Immunol Immunopathol, vol. 122, pp. 65-75, 2008.
Marti, E Antczak D, V. Gerber, A. D. Wilson, J. P. Lavoie, D. Horohov, R. Crameri, D. P. Lunn, D. Antczak, S. Björnsdóttir, B. TS, et al., "Report of the 3rd Havemeyer workshop on allergic diseases of the Horse, Hólar, Iceland, June 2007", Vet Immunol Immunopathol, vol. 126, issue 3-4, pp. 351-361, 2008.
2010
Hamza, E., S. Torsteinsdottir, M. Eydal, C. Frey, J. Mirkovitch, B. Wagner, A. D. Wislon, T. W. Jungi, and E. Marti, "Increased IL-4 and decreased regulatory cytokine production following relocation of Icelandic horses from a high to low endoparasite environment", Vet Immunol Immunopathol, vol. 133, pp. 40-50, 2010.
2011
Hamza, E., V. Gerber, F. Steinbach, and E. Marti, "Equine CD4+CD25high T cells exhibit regulatory activity by close contact and cytokine-dependent mechanisms in vitro ", Immunology, vol. 134, pp. 292-304, 2011.
Schaffartzik, A., E. Marti, E. Hamza, J. Janda, R. Crameri, and C. Rhyner, "Equine insect bite hypersensitivity: what do we know?", Vet Immunol Immunopathol, vol. 147, issue 3-4, pp. 113-126, 2011.
2012
Hamza, E., F. Steinbach, and E. Marti, "CD4+CD25+ T cells expressing FoxP3 in Icelandic horses affected with insect bite hypersensitivity.", Vet Immunol Immunopathol, vol. 148, issue 1-2, pp. 139-144, 2012.
2013
Lanz, S., V. Gerber, J. Klukowska-Rötzler, H. Rettmer, E. Marti, J. Matthews, S. Pirie, and E. Hamza, "Effect of hay-dust extract and cyathostomins stimulation on cytokine expression by PBMC from horses affected with recurrent airway obstruction.", Vet Immunol Immunopathol, vol. 155, issue 4, pp. 229-237, 2013.
Hamza, E., C. A. Akdis, B. Wagner, F. Steinbach, and E. Marti, "Restoring the ability of CD4+CD25+ T cells to suppress allergen-induced proliferation of CD4+CD25- Cells in horses affected with insect bite hypersensitivity", Clinical and experimental Allergy, vol. 43, pp. 889-901, 2013.
2014
Marti, E., and E. Hamza, "Equine immunoglobulin E. in Veterinary Allergy, Eds Noli, C, Foster, A, Rosenkrantz W. ", Veterinary allergy, Hoboken, New Jersey, Wiley Blackwell, 2014.
Mählmann, K., E. Hamza, E. Marti, J. Klukowska-Rötzler, V. Gerber, and C. Koch, "Increased FoxP3 expression in tumor associated tissues of horses affected with equine sarcoid disease", Veterinary Journal Elsevier, vol. 202, issue 3, pp. 516-21, 2014.
2015
Jonsdottir, S., E. Hamza, J. Janda, C. Rhyner, A. Meinked, E. L. Marti, V. Svansson, and S. Torsteinsdottir, "Developing a preventive immunization approach against insect bite hypersensitivity using recombinant allergens: A pilot study", Veterinary Immunology and Immunopathology , vol. 166, pp. 8-21, 2015.
Jonsdottir, S., E. Hamza, J. Janda, C. Rhyner, A. Meinke, E. Marti, W. Svanson, and S. Torsteinsdottir, "Developing a preventive immunization approach against insect bite hypersensitivity using recombinant allergens: a pilot study. ", Vet Immunol Immunopathol, vol. 166, issue 1-2, pp. 8-21, 2015.
Pacholewska, A., V. Jagannathan, M. Drögemüller, J. Klukowska-Rötzler, S. Lanz, E. Hamza, E. T. Dermitzakis, E. L. Marti, T. Leeb, and V. Gerber, "Impaired Cell Cycle Regulation in a Natural Equine Model of Asthma", Plos One , vol. 10, issue 8, pp. 1-23, 2015.
Hamza, E., J. Mirkovitch, F. Steinbach, and E. Marti, "Regulatory T cells in early life: Comparative study of CD4+CD25 high T cells from foals and adult horses", PLOS ONE, vol. 10(3), issue e012066, 2015.
Pacholewska, A., M. Drögemüller, J. Klukowska-Rötzle, S. Lanz, E. Hamza, E. T. Dermitzak, E. L. Marti, V. Gerber, T. Leeb, and V. Jagannathan, "The Transcriptome of Equine Peripheral Blood Mononuclear Cells", Plos One, vol. 10, issue 3, pp. 1-16, 2015.
Poacholewska, A., M. Drögemüller, J. Klukowska-Rötzler, S. Lanz, E. Hamza, E. Dermitzakis, E. Marti, V. Gerber, T. Leeb, and V. Jagannatha, "Transcriptome of equine peripheral blood mononuclear cells.", PLOS ONE, vol. 10(3), issue e0122011, 2015.
2016
Hamza, E., S. M. Dorgham, and D. A. Hamza, "Carbapenemase-producing Klebsiella pneumoniae in broiler poultry farming in Egypt.", Journal of global antimicrobial resistance, vol. 7, pp. 8-10, 2016 Dec. Abstract

This study investigated the occurrence of carbapenem-resistant Klebsiella pneumoniae strains in broiler chickens, drinking water and humans working in contact with chickens and identified the carbapenem resistance determinants among isolates from different sources. Internal organs and droppings were collected from 100 broilers with signs of respiratory disease at five broiler farms in Egypt. Additionally, 20 drinking water samples and 49 faecal samples from workers and veterinarians working at these farms were included. Following culture on MacConkey agar, suspected K. pneumoniae colonies were identified by phenotypic testing. Susceptibility to carbapenems was tested in confirmed K. pneumoniae isolates by disk diffusion. Carbapenem-resistant isolates were subjected to PCR for detection of carbapenemase-encoding genes (blaKPC, blaOXA-48 and blaNDM). K. pneumoniae was isolated from 35% of broilers and 25% of water samples. Of the 35 poultry isolates, 15 were carbapenem-resistant; all of them were blaNDM-positive, including 11 isolates harbouring blaKPC, blaOXA-48 and blaNDM and 4 containing either blaKPC and blaNDM (n=3) or blaOXA-48 and blaNDM (n=1). Similarly, three of five K. pneumoniae isolates from drinking water were positive for blaKPC and blaNDM (n=1) or for all three genes (n=2). Interestingly, 56% of K. pneumoniae from humans displayed carbapenem resistance; all of them were positive for the three carbapenemase genes. Carbapenemase-producing K. pneumoniae occurred at relatively high frequency among broilers, drinking water and workers at poultry farms in Egypt. Additional work is needed to confirm transmission between poultry and humans and to elucidate the direction and mechanism of transmission.

SABRY, M. A. H. A., K. Abdel-Moein, E. Hamza, and F. A. T. M. A. A. B. D. E. L. KADER, "Occurrence of Clostridium perfringens Types A, E, and C in Fresh Fish and Its Public Health Significance.", Journal of food protection, vol. 79, issue 6, pp. 994-1000, 2016 Jun. Abstract

Fish remains among the most traded of food commodities, and Egypt is one of the emerging countries being recognized as an important world fish exporter. Clostridium perfringens is an important foodborne pathogen to consider in fish trade, as it has been implicated as the causative organism of two fish outbreaks. The aim of the present study was to investigate the occurrence and toxin diversity of C. perfringens associated with fresh and canned fish and to examine the public health significance of C. perfringens infection in fish. Isolation and identification of C. perfringens showed a significantly higher prevalence of the bacterium in fresh fish collected from aquaculture (54.5%) and from markets (71%) as well as in humans in contact with fish (63%) compared with water used for keeping fresh fish (27.3%) and water used in canned fish (17.8%). The isolation level was significantly higher in samples from the external surface of fresh fish (31.8% in aquaculture, 45.6% in markets) than from the intestinal contents of the same fish (9.1% in aquaculture, 6.7% in markets). Thus, markets represent a risk factor for contamination of the external surface of fish from the surrounding environment. Genotyping of the C. perfringens-positive isolates by using multiplex PCR revealed that type A enterotoxin-negative (CPE(-)) is the predominant strain among fish (fresh and canned), humans, and water in contact with fresh fish. Interestingly, C. perfringens types A enterotoxin-positive (CPE(+)) and C were found only in fresh fish, and these two strains have great health importance in humans. Strikingly, C. perfringens type E strain was detected for the first time in fish, humans, and water in contact with fresh fish. Our results demonstrate for the first time that fish act as a reservoir for C. perfringens, particularly for types A CPE(+), C, and E. The external surface of fish represents a vehicle for contamination of fish from the surrounding environment as well as a source of infection of humans, thereby representing a public health hazard.

Ziegler, A., H. Everett, E. Hamza, M. Garbani, V. Gerber, E. L. Marti, and F. Steinbach, "Equine dendritic cells generated with horse serum have enhanced functionality in comparison to dendritic cells generated with fetal bovine serum.", BMC veterinary research, vol. 12, issue 1, pp. 254, 2016 Nov 15. Abstract

BACKGROUND: Dendritic cells are professional antigen-presenting cells that play an essential role in the initiation and modulation of T cell responses. They have been studied widely for their potential clinical applications, but for clinical use to be successful, alternatives to xenogeneic substances like fetal bovine serum (FBS) in cell culture need to be found. Protocols for the generation of dendritic cells ex vivo from monocytes are well established for several species, including horses. Currently, the gold standard protocol for generating dendritic cells from monocytes across various species relies upon a combination of GM-CSF and IL-4 added to cell culture medium which is supplemented with FBS. The aim of this study was to substitute FBS with heterologous horse serum. For this purpose, equine monocyte-derived dendritic cells (eqMoDC) were generated in the presence of horse serum or FBS and analysed for the effect on morphology, phenotype and immunological properties. Changes in the expression of phenotypic markers (CD14, CD86, CD206) were assessed during dendritic cell maturation by flow cytometry. To obtain a more complete picture of the eqMoDC differentiation and assess possible differences between FBS- and horse serum-driven cultures, a transcriptomic microarray analysis was performed. Lastly, immature eqMoDC were primed with a primary antigen (ovalbumin) or a recall antigen (tetanus toxoid) and, after maturation, were co-cultured with freshly isolated autologous CD5(+) T lymphocytes to assess their T cell stimulatory capacity.

RESULTS: The microarray analysis demonstrated that eqMoDC generated with horse serum were indistinguishable from those generated with FBS. However, eqMoDC incubated with horse serum-supplemented medium exhibited a more characteristic dendritic cell morphology during differentiation from monocytes. A significant increase in cell viability was also observed in eqMoDC cultured with horse serum. Furthermore, eqMoDC generated in the presence of horse serum were found to be superior in their functional T lymphocyte priming capacity and to elicit significantly less non-specific proliferation.

CONCLUSIONS: EqMoDC generated with horse serum-supplemented medium showed improved morphological characteristics, higher cell viability and exhibited a more robust performance in the functional T cell assays. Therefore, horse serum was found to be superior to FBS for generating equine monocyte-derived dendritic cells.

2017
Hamed, O. M., M. A. Sabry, N. A. Hassanain, E. Hamza, A. G. Hegazi, and M. B. Salman, "Occurrence of virulent and antibiotic-resistant Shiga toxin-producing Escherichia coli in some food products and human stool in Egypt.", Veterinary World, EISSN: 2231-0916, vol. 10, issue 10, pp. 1233-1240, 2017. vetworld-10-1233.pdf
Hamza, E., S. Kittl, and P. Kuhnert, "Temporal induction of pro-inflammatory and regulatory cytokines in human peripheral blood mononuclear cells by Campylobacter jejuni and Campylobacter coli.", PloS one, vol. 12, issue 2, pp. e0171350, 2017. Abstract

Campylobacter jejuni along with C. coli are major cause of human gastroenteritis worldwide. So far, the human immune response against Campylobacter is not entirely clear. We hypothesize that it is coordinated by an interaction between pro-inflammatory and regulatory cytokines which is influenced by bacterial and host-individual differences. Accordingly, we used peripheral blood mononuclear cells (PBMC) from healthy donors to study the primary systemic immune response to C. jejuni and C. coli. PBMC were stimulated by different strains of C. jejuni and C. coli for three time points (5, 10, 24 hours). The production of the pro-inflammatory (IL-6, IL-8, IFN-γ) and the regulatory (IL-10) cytokines were measured by ELISA. All strains induced higher levels of IL-8 and IL-6 than IFN-γ and IL-10. In contrast to IL-8 and IL-6, IL-10 showed a steeper increase over time. While IFN-γ did not show any further increase between 10 and 24 hours. Interestingly, there was a significant correlation between IL-8 and IL-10 which peaked at 24 hours. Despite the variability of the used bacterial strains, their effect on cytokine production was less pronounced than the inter-person differences. The strongest significant effect of the strain was on the level of IL-10. IL-10 and IL-6 were significantly influenced by strain-person interaction. In conclusion, the systemic immune response to C. coli and C. jejuni is characterized by an early pro-inflammatory reaction with later initiation of regulatory immune response which is influenced mainly by the host, explaining the individual variations in disease severity. Additional work is needed to determine the cellular sources of the produced cytokines as well as the campylobacter molecules that might contribute to this stimulation.

2018
Anja, Z., H. Eman, J. Sigridur, R. Claudio, W. Bettina, S. Getraud, S. Vilhjalmur, T. Sigurbjorg, and M. Eliane, "Longitudinal analysis of allergen-specific IgE and IgG subclasses as potential predictors of insect bite hypersensitivity following first exposure to Culicoides in Icelandic horses.", Vet Dermatology, vol. 29, issue 1, pp. 51-e22, 2018.
Ahmed-Hassan, H., M. S. Abdul-Cader, U. De Silva Senapathi, M. A. Sabry, E. Hamza, E. Nagy, S. Sharif, and M. F. Abdul-Careem, "Potential mediators of in ovo delivered double stranded (ds) RNA-induced innate response against low pathogenic avian influenza virus infection.", Virology journal, vol. 15, issue 1, pp. 43, 2018 03 12. Abstract

BACKGROUND: Toll like receptor (TLR) 3 is a critically important innate pattern recognizing receptor that senses many viral infections. Although, it has been shown that double stranded (ds) RNA can be used for the stimulation of TLR3 signaling pathway in a number of host-viral infection models, it's effectiveness as an antiviral agent against low pathogenic avian influenza virus (LPAIV) needs further investigation.

METHODS: In this study, first, we delivered TLR3 ligand, dsRNA, in ovo at embryo day (ED)18 since in ovo route is routinely used for vaccination against poultry viral and parasitic infections and infected with H4N6 LPAIV 24-h post-treatment. A subset of in ovo dsRNA treated and control groups were observed for the expressions of TLR3 and type I interferon (IFN)s, mRNA expression of interleukin (IL)-1β and macrophage recruitment coinciding with the time of H4N6 LPAIV infection (24 h post-treatment). Additionally, Day 1 chickens were given dsRNA intra-tracheally along with a control group and a subset of chickens were infected with H4N6 LPAIV 24-h post-treatment whereas the rest of the animals were observed for macrophage and type 1 IFN responses coinciding with the time of viral infection.

RESULTS: Our results demonstrate that the pre-hatch treatment of eggs with dsRNA reduces H4N6 replication in lungs. Further studies revealed that in ovo delivery of dsRNA increases TLR3 expression, type I IFN production and number of macrophages in addition to mRNA expression of IL-1β in lung 24-h post-treatment. The same level of induction of innate response was not evident in the spleen. Moreover, we discovered that dsRNA elicits antiviral response against LPAIV correlating with type I IFN activity in macrophages in vitro. Post-hatch, we found no difference in H4N6 LPAIV genome loads between dsRNA treated and control chickens although we observed higher macrophage recruitment and IFN-β response coinciding with the time of viral infection.

CONCLUSIONS: Our findings imply that the TLR3 ligand, dsRNA has antiviral activity in ovo and in vitro but not in chickens post-hatch and dsRNA-mediated innate host response is characterized by macrophage recruitment and expressions of TLR3 and type 1 IFNs.

Ahmed-Hassan, H., M. S. Abdul-Cader, M. A. Sabry, E. Hamza, and M. F. Abdul-Careem, "Toll-like receptor (TLR)4 signalling induces myeloid differentiation primary response gene (MYD) 88 independent pathway in avian species leading to type I interferon production and antiviral response.", Virus research, vol. 256, pp. 107-116, 2018 09 02. Abstract

Engagement of toll-like receptor (TLR)4 ligand, lipopolysaccharide (LPS) with TLR4 in mammals activates two downstream intracellular signaling routes; the myeloid differentiation primary response gene (MyD)88 dependent and independent pathways. However, existence of the later pathway leading to production of type I interferons (IFNs) in avian species has been debated due to conflicting observations. The objective of our study was to investigate whether LPS induces type I IFN production in chicken macrophages leading to antiviral response attributable to type I IFN. We found that LPS elicits type I IFN response dominated by IFN-β production. We also found that reduction in infectious laryngotracheitis virus (ILTV) replication by LPS-mediated antiviral response is attributable to type I IFNs in addition to nitric oxide (NO). Our findings imply that LPS elicits both MyD88 dependent and independent pathways in chicken macrophages consequently eliciting anti-ILTV response attributable to production of both type I IFNs and NO.