From the working group “ Experimental Pathology ” to the department “ Pathology Unit ” – historical development in retrospect

Abstract. The Pathology Unit of the German Primate Center started as the working group of Experimental Pathology in 1992. This small group with one veterinary pathologist and a technician was founded based on an idea of Prof. Dr. Kuhn, who wanted to strengthen the pathology research activities and to establish a centralized electron microscopy laboratory. Later on, experimental pathology, veterinary services and primate husbandry were integrated as the Department of Veterinary Medicine and Primate Husbandry but subsequently again separated. Prof. Dr. Franz-Josef Kaup, the head of the previously integrated department, remained in his capacity as the leader of the different units. Over the years, the research activities have changed from SIV-associated pathology to other infectious diseases. Today, the main research focus is on the pathogenesis of orthopoxvirus infection, primate pathology, neglected tropical diseases and nonhuman primates as models for chronic respiratory diseases. This paper gives an overview of the historical development and aspects of research activities.


Introduction
Following its establishment in the early 1980s, the initial divisional structure of the German Primate Center reorganized its scientific focus towards the end of this decade.In this context, establishment of a new Morphology and Systematics Department was considered, for which acquisition of a transmission electron microscope was planned.In the financial year of 1990, a budget of DM 750 000 was set aside for a transmission electron microscope.Establishment of an electron microscopic device was also supported by the German Council of Science during evaluation of the German Primate Center in January 1990.At the same time, the head of the German Primate Center, Professor Kuhn, considered setting up an independent scientific working group for experimental pathology in addition to the existing Pathology Department headed by Dr. Manfred Brack.
2 Establishment of the working group "Experimental Pathology": 1992-1996 In the subsequent meetings of the Scientific Advisory Council and the Supervisory Board, establishment of three working groups was decided on in June 1991: Electron Microscopy, Behavior Research, and Experimental Pathology (Supervisory Board Meeting on 4 June 1991).Since an eligible candidate for the head of the Electron Microscopy group could not be found, supervision of the electron microscope as part of the central service facility was assigned to the new Experimental Pathology group.At the same time, Dr. Franz-Josef Kaup, who at the time was a research assistant in the electron microscopy division of the Institute of Pathology, University of Veterinary Medicine Hanover, was invited to give a talk at the German Primate Center.On 30 January 1992 Dr. Kaup gave a presentation titled "Morphologic Methods of Viral Detection with Special Reference to Immunoelectron Microscopy" at the German Primate Center.After discussion in the Scientific Advisory Council, Dr. Kaup was endorsed as head for the new Experimental Pathology working group.Thus, two During the first few years, the newly formed working group focused on the pathogenesis of gastrointestinal and respiratory infections, while related ultrastructural studies contributed to the establishment of a central electron microscopy division (Kaup et al., 1994(Kaup et al., , 1998(Kaup et al., , 2005;;Kuhn and Kaup, 1996).In this process, the Department of Virology and Immunology proved to be a valuable partner, as both experimental SIV infections in rhesus macaques (Fig. 1) and associated opportunistic infections opened new research fields for the working group (Figs. 2 and 3).At the beginning of 1994, Dr. Kerstin Mätz-Rensing joined the working group as the first research assistant, and spontaneous nonhuman primate disease increasingly became the subject of research.Special emphasis was laid on the establishment of immunohistochemical markers for nonhuman primate tissue, which were used in different studies on the pathogenesis of the intestinal SIV infection, but also for tumor differentiation and classification in nonhuman primates (Kuhn et al., 1999;Didier et al., 1999;Mätz-Rensing et al., 1999b;Kaup et al., 2001;Kahnt et al., 2002).Beside pathomorphological methods, new in vivo experimental techniques were also implemented.Endoscopic techniques were introduced at the German Primate Center during a study on SIV passage via the intestinal barrier (Kewenig et al., 1999;Schäfer et al., 2002).Since then, endoscopy has been an essential tool that is widely used to this day to obtain gastrointestinal biopsies in experimental infections, for example, with Helicobacter pylori.Dr. Kaup, who was meanwhile appointed as an exceptional professor by the University of Veterinary Medicine    pensary, veterinary diagnostics (pathology, histology, bacteriology, and parasitology), primate husbandry with animal and sample supply, transmission electron microscopy, and animal welfare.This broad service spectrum was intensively used by many internal and external scientists.On 1 December 2000, Professor Dr. Kaup was appointed university professor for laboratory animal pathology at the University of Veterinary Medicine Hanover, which was connected to his position as the head of the Department of Veterinary Medicine and Primate Husbandry at the German Primate Center.

New trends of research
During this time, the scientific spectrum of the department also expanded.In 2001, Dr. Uwe Hahmann and Professor Walter Bodemer established a new working group named Spongiform Encephalopathies, which focused on the pathogenesis of prion diseases and was notably funded by the EU during the BSE crisis (Krasemann et al., 2010;Kiesel et al., 2012a, b).The SIV/SHIV macaque model was continuously serviced pathomorphologically for the Department of Virology and Immunology (headed by Professor Dr. Hunsmann) and later on the Department of Infection Models (Dr.Stahl-Hennig).Dr. Mätz-Rensing succeeded to establish a macaque model for experimental Helicobacter pylori infections (Mätz-Rensing et al., 1999a;Mätz-Rensing et al., 2001) as well as detection systems for alveolar echinococcosis (Tappe et al., 2007), a tapeworm infection that has been increasingly diagnosed in the breeding colonies of the German Primate Center (Fig. 4).As both facilities were headed by Professor Kaup, the duties and responsibilities of this group remained unchanged (Table 1).
In 2004, the Pathology Unit set up two new working groups.The Dermatopathology group, headed by Dr. Bärbel Löblich-Beardi, worked on alopecia in rhesus macaques (Beardi et al., 2007;Steinmetz et al., 2005Steinmetz et al., , 2006) ) and the herpesvirus group, headed by Dr. Dieter Jentsch.Follow- The Primate Pathology group concentrated on spontaneous diseases in nonhuman primates for many years (Mätz-Rensing et al., 2012a) (Fig. 5).The group, led by Dr. Mätz-Rensing, established a new orthopoxvirus model in marmosets based on a diagnostic case of an orthopoxvirus infection in New World monkeys (Fig. 6).This model was used to investigate the clinical and pathological changes of this novel infection and enabled translational evaluation of vaccine efficacy.
This orthopoxvirus model was developed in response to a disease outbreak in a private primate husbandry in 2002.Several New World monkeys, among them common marmosets (Callithrix jacchus), died within a very short period of time.Necropsy of some animals with subsequent histological and electron microscopic examinations at the German Primate Center revealed an orthopoxvirus infection.In collaboration with the Robert Koch Institute (RKI), a cow pox virus was isolated.Sequence analyses and phylogenetic investigations showed that it was a novel cow pox virus, which was named calpox virus after its host species ("Callithrix") (Mätz-Rensing et al., 2006, 2012b;Kramski et al., 2010;Schmitt et al., 2014).
The virus was cultured from different organs, and a virus stock was generated by means of a permanent cell line.Meanwhile, different studies were conducted to determine the infectious dose and the optimal inoculation route for experimental infection and to characterize the pathogenesis and the spread of the virus to different organs.Vaccination studies with intranasal virus challenge (8.3 × 10 3 PFU of calpox virus) showed that the old vaccine, which had many adverse effects (vaccinia virus Elstree VACV LE-BN), provided adequate protection in comparison to subsequently developed vaccines (MVA: modified vaccinia virus Ankara; MVTT: modified vaccinia virus Tiantan), which did not induce reliable immunization.
In April 2010, a cooperation was established with a working group of the Fraunhofer Institute for Toxicology and experimental Medicine (ITEM) Hanover (today headed by Dr. Franziska Dahlmann), which works on primate models for COPD and asthma (Seehase et al., 2011(Seehase et al., , 2012)).This group is supported by a working group of the Pathology Unit named Anatomy/Pathology of the respiratory tract headed by Dr. Martina Bleyer (Hoffmann et al., 2013(Hoffmann et al., , 2014) ) (Fig. 7).Furthermore, a new research group studies neglected tropical www.primate-biol.net/2/57/2015/Primate Biol., 2, 57-63, 2015 F.-J. Kaup: From "Experimental Pathology" to "Pathology Unit" diseases in particular Treponema infection in baboons.This group (head Dr. Sascha Knauf) combines laboratory investigations in infectious diseases with field studies in free-living nonhuman primates (Knauf et al., 2012(Knauf et al., , 2015)).

Outlook
Over the past few decades, the German Primate Center has continuously focused on nonhuman primate pathology.
Results of the research activities are documented in more than 200 publications and 41 veterinary medical dissertations.In addition to its great contribution to research, the pathological diagnostics with associated etiological examinations and extensive sample supply represent important services offered by the German Primate Center that have been used extensively by external scientists and vets.At the German Primate Center, seven veterinarians have completed their five-year training to become veterinary specialists in pathology.The research activities and the diagnostic services of the Pathology Unit are of special value to the Infection Research Section because of the profound expertise in primate diseases and pathology, which is essential for a primate center.
Edited by: E. Fuchs Reviewed by: two anonymous referees

Figure 1 .
Figure 1.Transmission electron micrograph on the cover page of the program 5th German AIDS congress in Hanover, 1994.The micrograph presents an intracytoplasmic vacuole containing SIV particles.The structure was found in an SIV-induced giant cell from an infected rhesus monkey (Macaca mulatta).Photo taken by Kaup, Experimental Pathology, German Primate Center.

Figure 2 .
Figure 2. Cryptosporidiosis in an SIV-infected rhesus macaque.Enterocytes (Nu -nucleus) with adjacent parasites.The parasitophorous vacuoles (PV) are probably formed by the microvilli (MV) of the affected enterocytes.The ultrastructure of the vacuoles argue for the morphology of schizonts containing merozoites.Cryptosporidiosis is a typical opportunistic infection in SIVinfected macaques.Transmission electron microscopy.

Figure 3 .
Figure 3. Scanning electron micrograph showing a hemispherical intestinal dome area bulging into the gut lumen and surrounded by intestinal villi.The domes are covered by enterocytes and M cells (M -cytoplasm, Nu -nucleus).Transmission electron microscopy demonstrates the close contact of an M cell with intraepithelial lymphocytes (IEL).Ileum, rhesus monkey (Macaca mulatta).

Figure 4 .
Figure 4. Gross pathology of a hepatic echinococcosis.The parasites invade the liver tissue with multiple cystic transformation.Echinococcus multilocularis infection of a rhesus monkey of the German Primate Center.

Figure 5 .
Figure 5. Macroscopic findings in a cynomolgus macaque (Macaca fascicularis) from a diagnostic necropsy.Abundant amounts of encysted parasitic larvae in the abdominal viscera.In this case of a pentastomiasis PCR was done.The sequence matched 98 % that of Armillifer agkistrodontis.

Figure 6 .
Figure 6.Skin lesions due to a calpox infection in a marmoset (Callithrix jacchus).Apart from inflammatory signs calpox lesions are characterized by so-called Guarnieri bodies (arrow) within the cytoplasm of epithelial cells.Transmission electron microscopy of the Guarnieri bodies presents orthopoxvirus particles (inset).

Figure 7 .
Figure 7. Transmission electron micrograph of a ciliated cell (Ci) originating from the tracheal respiratory epithelium of a newborn marmoset (Callithrix jacchus).In the airway lumen numerous cross-sectioned cilia present normal axonemes consisting of a central pair of filaments surrounded by nine other pairs.In addition to normal cilia an atypical cilium (CC) is demonstrated.This malformation belongs to compound cilia of bulging type which contains loosely and randomly embedded axonemes.

Table 1 .
History of the Pathology Unit at the German Primate Center