New insight into molecular mechanisms underlying division of labor in honeybees

Honeybees are highly organized eusocial insects displaying a distinct division of labor. Juvenile hormone (JH) has long been hypothesized to be the major driver of behavioral transitions. However, more and more experiments in recent years have suggested that the role of this hormone is not as fundamental as hypothesized. Vitellogenin, a common egg yolk precursor protein, seems to be the major regulator of division of labor in honeybees, in connection with nutrition and the neurohormone and transmitter octopamine. Here, we review the role of vitellogenin in controlling honeybee division of labor and its modulation by JH, nutrition, and the catecholamine octopamine.

Corrigendum: Honeybees are buffered against undernourishment during larval stages

[This corrects the article DOI: 10.3389/finsc.2022.951317.].

Honeybees are buffered against undernourishment during larval stages

The negative impact of juvenile undernourishment on adult behavior has been well reported for vertebrates, but relatively little is known about invertebrates. In honeybees, nutrition has long been known to affect task performance and timing of behavioral transitions. Whether and how a dietary restriction during larval development affects the task performance of adult honeybees is largely unknown. We raised honeybees in-vitro, varying the amount of a standardized diet (150 µl, 160 µl, 180 µl in total). Emerging adults were marked and inserted into established colonies. Behavioral performance of nurse bees and foragers was investigated and physiological factors known to be involved in the regulation of social organization were quantified. Surprisingly, adult honeybees raised under different feeding regimes did not differ in any of the behaviors observed. No differences were observed in physiological parameters apart from weight. Honeybees were lighter when undernourished (150 µl), while they were heavier under the overfed treatment (180 µl) compared to the control group raised under a normal diet (160 µl). These data suggest that dietary restrictions during larval development do not affect task performance or physiology in this social insect despite producing clear effects on adult weight. We speculate that possible effects of larval undernourishment might be compensated during the early period of adult life.

In Vitro Rearing Changes Social Task Performance and Physiology in Honeybees

Simple Summary

The rearing of honeybee larvae in the laboratory is an important tool for studying the effects of plant protection products or pathogens on developing and adult bees, yet how rearing under artificial conditions affects the later social behavior and physiology of the honeybees is mostly unknown. We, here, show that honeybees reared in the laboratory generally had a lower probability for performing nursing or foraging tasks compared to bees reared under natural conditions in bee colonies. Nursing behavior itself appeared normal in in vitro honeybees. In contrast, bees reared in the laboratory foraged for a shorter period in life and performed fewer trips compared to bees reared in colonies. In addition, in vitro honeybees did not display the typical increase in juvenile hormone titer, which goes hand-in-hand with the initiation of foraging in colony-reared bees.

Abstract

In vitro rearing of honeybee larvae is an established method that enables exact control and monitoring of developmental factors and allows controlled application of pesticides or pathogens. However, only a few studies have investigated how the rearing method itself affects the behavior of the resulting adult honeybees. We raised honeybees in vitro according to a standardized protocol: marking the emerging honeybees individually and inserting them into established colonies. Subsequently, we investigated the behavioral performance of nurse bees and foragers and quantified the physiological factors underlying the social organization. Adult honeybees raised in vitro differed from naturally reared honeybees in their probability of performing social tasks. Further, in vitro-reared bees foraged for a shorter duration in their life and performed fewer foraging trips. Nursing behavior appeared to be unaffected by rearing condition. Weight was also unaffected by rearing condition. Interestingly, juvenile hormone titers, which normally increase strongly around the time when a honeybee becomes a forager, were significantly lower in three- and four-week-old in vitro bees. The effects of the rearing environment on individual sucrose responsiveness and lipid levels were rather minor. These data suggest that larval rearing conditions can affect the task performance and physiology of adult bees despite equal weight, pointing to an important role of the colony environment for these factors. Our observations of behavior and metabolic pathways offer important novel insight into how the rearing environment affects adult honeybees.

Inguinal hernia TAPP repair using Senhance® robotic platform: first multicenter report from the TRUST registry

PURPOSE

The purpose of this article was to provide feasibility and safety results of robotic transabdominal preperitoneal inguinal hernia repair (Robotic TAPP).

METHODS

We included 271 cases of robotic inguinal hernia TAPP repair using the Senhance^® robotic platform from four different centers between March 2017 and March 2020. Key data points were intraoperative and postoperative complication rate, operating time, length of hospital stay, postoperative pain score and time required to get back to a daily routine that were inserted in the TransEnterix European Patient Registry for Robotic assisted Laparoscopic Procedures in Urology, Abdominal Surgery, Thoracic and Gynecologic Surgery (TRUST).

RESULTS

We report 203 cases of unilateral and 68 cases of bilateral inguinal hernia repairs. Mean operative time was 74 ± 35 min (range 32-265 min), postoperative complications occurred in five (1.85%) cases, the intraoperative complication rate was five (1.85%). The average subjective patient-related pain score after the procedure was 3 ± 1.9 (range 1-9), length of hospital stay was 39 ± 28 h (range 4-288 h), and recovery time was 9.65 ± 8 days (range 1-36 days).

CONCLUSION

Robotic inguinal hernia TAPP repair shows inspiring results. It is a safe and doable procedure. However, cost analysis should be performed in future to show the superiority over other techniques.

Use of ultrasonography to detect calcifications in cattle and sheep fed Trisetum flavescens silage

Twelve cows (mean age 6.4 years) and eight sheep (mean age 0.8 years) were fed silage containing 70 to 90 per cent vitamin D3-effective Trisetum flavescens for a period of 14 weeks. At the beginning and the end of this period, the animals were examined and their kidneys, abdominal aortas and heart valves were examined by ultrasonography; the animals were then slaughtered and these organs were examined histologically, and the specificity and sensitivity of the ultrasonography were calculated. After the feeding period, all the cows had a decreased body temperature and all but one had raised hair, movement disorders and difficulty in rising and lying down. Ultrasonography of the abdominal aorta had a specificity of 90 per cent and a sensitivity of 75 per cent, and ultrasonography of the heart valves had a specificity of 100 per cent and a sensitivity of 50 per cent. In the sheep, cardiac arrythmia was the only pathological finding at the end of the feeding period, and the ultrasonographic examination of the kidneys had a specificity and sensitivity of 100 per cent.

Fibroepithelial hamartoma in a domestic pig

This case report is the first description of a fibroepithelial hamartoma in a pig. The dysplasia, which covered half of the face of the newborn piglet, did not increase in relative size until the animal was euthanatized at 6 months of age. Histologic examination revealed a moderate orthokeratotic hyperkeratosis with variable degrees of epithelial proliferation. The main body of the dysplasia consisted of collagenous fibers. In addition, some proliferating small blood vessels as well as focally gathered dilated apocrine glands were evident. Given morphologic and clinical features, the diagnosis of a hamartoma seemed to be justified.

Immunophenotypic characterization of peripheral blast cells in a leukemic miniature pig

The health status of a 4-year-old female, dd-haplotype miniature pig deteriorated rapidly, so the animal finally had to be euthanized because of poor clinical condition. Necropsy revealed a massive leukocytic infiltration in the parenchymatous organs of the abdominal cavity. On hematologic cell counting, severe leukocytosis (69.3 x 10(9) cells/liter) and high-grade basophilia (6.9 x 10(9) cells/liter) were evident. Cytologic examination, as well as analysis of expression of leukocyte differentiation antigens by means of flow cytometry, classified blasts, which accounted for about 22% of leukocytes, as biphenotypic cells co-expressing the myeloid marker SWC3 (CD172a) and the lymphoid markers CD5 and CD25. Hematologic features resembled those seen in humans with chronic myeloid leukemia at blast phase.

Porcine dermatitis and nephropathy syndrome (PDNS) is associated with a systemic cytokine expression profile indicative of proinflammation and a Th1 bias

Porcine dermatitis and nephropathy syndrome (PDNS) is broadly discussed as a porcine circovirus type 2 (PCV2)-associated disease, although PCV2, in contrast to postweaning multisystemic wasting syndrome (PMWS), has to date not been proven to be the aetiologic agent. In order to better understand the complex immunopathology of PDNS, the systemic cytokine expression profiles of (i) five pigs suffering from PDNS, (ii) five animals suffering from naturally acquired PMWS and (iii) five controls were investigated at mRNA and protein levels by means of multiplex real-time RT-PCR and flow cytometric intracellular cytokine detection, respectively. IL-1alpha, IL-6 and IFN-gamma mRNA expressions were found to be elevated in PDNS pigs. At the protein level, an increased capacity of peripheral blood mononuclear cells to produce IL-2, IL-4, IL-6, IL-12, TNF-alpha and IFN-gamma was evident. Hematological investigations revealed a hypochromic anemia while basophils and monocytes were relatively and neutrophils absolutely increased in PDNS pigs. PCV2 antibody levels did not differ significantly between PDNS and PMWS affected animals. Taken results together, the cytokine profile of the PDNS affected animals together with hematological data pointed towards a proinflammatory condition supporting a Th1 bias. Cytokine data of PMWS affected animals exhibited only minor non-significant differences when compared to controls, only IL-10 was significantly decreased at the mRNA level.

Outbreak of Clinical Listeriosis in Sheep: Evaluation from possible Contamination Routes from Feed to Raw Produce and Humans

We report the results of clinical and microbiological investigations on Listeria monocytogenes infections in a flock of 55 sheep and describe the implications for the safety of the raw milk and raw-milk cheeses produced in the on-farm dairy. The outbreak was caused by feeding grass silage, which was contaminated with 5 log10 CFU L. monocytogenes/g. Clinically, although having been fed from the same batch of silage, abortive (nine ewes), encephalitic (one ewe) and septicaemic (four ewes) forms of listeriosis were observed during the outbreak phase. As the starting point of feeding the contaminated silage was known we could calculate an incubation period of 18+/-2 and 26 days for the abortive and the encephalitic form of listeriosis, respectively. Pathologically, the septicaemic cases suffered from Listeria accumulation at comparable numbers in visceral organs but not in the brain. Only a single ewe developed central nervous symptoms and a rhomb-encephalitis was immunohistologically confirmed. In this case the infection proceeded from the nasal mucosa into the brain, with no infections of the liver, spleen and other visceral organs. Sampling of the cheese production chain, the farm environment and the persons living at the farm revealed the exposure of a farm-worker to an isolate genetically indistinguishable from the outbreak clone, obviously through the consumption of faecally contaminated bovine raw milk. The cheese under processing was free of Listeria because, as a result of intensive consultations, the farmer ensured a proper acidification of the cheese. The epidemiological findings suggest that food safety matters should be assessed in any case where infection of food-producing animals with potential human pathogens is observed.

Clinical and histopathological aspects of naturally occurring mastitis caused by Listeria monocytogenes in cattle and ewes

Listeria monocytogenes was isolated from the milk of two cows and two sheep with mastitis in one quarter and one udder half. The animals were observed over a period of 2-12 months. Clinical examination of the udder, bacteriological examinations and determination of somatic cell counts of milk samples were performed monthly. All four cases suffered from a subclinical mastitis characterized by an elevated somatic cell count (0.8-10.1 x 10(6) cells/ml), a persistent shedding of Listeria and by a normal appearance of the milk. The animals did not show any systemic reaction, but all animals developed an atrophy of the infected mammary gland. Histological examinations revealed a chronic interstitial mastitis with diffuse infiltration of lymphocytes, plasma cells and macrophages. All internal organs showed no abnormalities, no Listeria could be isolated. Listeria could however be isolated from the affected mammary parenchyma and from the mammary lymph node. The results of the bacteriological examination could be confirmed by means of PCR. Using PFGE, all the isolates from the same animal were identical. Immunohistochemical examination of the ovine mammary glands achieved a very strong immunoreactivity for CD5 cells. The mode of infection and the reaction of the immune system's defense of the ovine udders are discussed.

Systemic cytokine profile in feeder pigs suffering from natural postweaning multisystemic wasting syndrome (PMWS) as determined by semiquantitative RT–PCR and flow cytometric intracellular cytokine detection

Postweaning multisystemic wasting syndrome (PMWS) is an economically important disease in pigs caused by porcine circovirus type 2 (PCV2). Development of this disease is presumably associated with an impairment of the immune system. We, therefore, investigated the systemic expression of relevant cytokines (IL-1, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p40, TNF-alpha, IFN-gamma) and IL-2Ralpha at mRNA (semiquantitative RT-PCR) and at protein level (flow cytometric intracellular cytokine detection after short-time stimulation of peripheral blood mononuclear cells) in 10 feeder pigs aged 14 weeks suffering from natural PMWS and in 10 clinically healthy pen-mates. Hematological examination revealed a significant (p < 0.001) relative lymphopenia in the diseased animals when compared to reference pigs. IL-1alpha and IL-10 mRNA levels were notably increased in the affected pigs, whereas IL-2 and IL-2Ralpha (CD25) mRNA levels tended to be down-regulated. IL-8, TNF-alpha and IFN-gamma mRNA expressions appeared to be slightly increased. Intracellular cytokine levels as measured by flow cytometry revealed an increase of IL-1beta, IL-2, and IL-6, whereas IL-12 and TNF-alpha expressions were not affected. IFN-gamma was slightly decreased in the diseased animals. In conclusion, despite the assumption, that the cellular immune response to PMWS as a virus-induced disease should be characterized by either a Th1 driven cytokine profile or a cytokine profile indicative of T cell immunosuppression, our results did not support that hypothesis. Nevertheless, data from intracellular cytokine detection suggest an even increased percentage of the remaining lymphocytes capable to produce IL-2 upon in vitro stimulation, which is in contrast to the slightly diminished IL-2 mRNA levels reflecting the in vivo situation at least at the mRNA level.

Clinical and pathological features of the Porcine Ulcerative Dermatitis Syndrome (PUDS)

The nomenclature of ulcerative dermatitis as used in literature is somehow confusing because on the one hand this skin disorder is associated with bacterial growth and on the other hand it is a synonym for a chronic sporadic disease of adult sows with unknown aetiology. Thus, we propose the terminus 'Porcine Ulcerative Dermatitis Syndrome (PUDS)' for the latter to distinguish between these two disease complexes. This syndrome could be identified by clinical and pathological examinations in six sows, that were submitted to the clinic. Epidermal ulcers could be found nearly all over the body, but teats were always spared. Haematological examination showed a slight anaemia but physiological leucocyte counts. However, lymphopenia (x = 44.8%), granulocytosis (x = 42.0%) and an increased number of monocytes (x = 13.1%) could be found. Histologically, a lymphoplasmacytic and granulohistiocytic infiltration in the corium was most prominent. In some cases, a moderate leucocytoclastic vasculitis and perivasculitis could be seen at the dermo-epidermal border. Additionally, a multifocal interstitial nephritis with lymphoplasmacytic infiltration was a prominent feature in all animals. Participation of an immune complex associated disorder can be assumed when regarding histological findings as skin lesions in combination with glomerulonephritis are a common feature of such diseases. Also, IgG levels were elevated two- to fourfold in all affected sows when compared with healthy control pigs. This supports the hypothesis that not only T cells, as shown previously, but also the humoral branch of the immune system is involved in the aetiology of PUDS.

Untersuchungen zur Wirkung von Galakturoniden als Futtermittelzusatz im Vergleich zum Leistungsförderer Flavophospholipol und einer Kontrollgruppe bei Absetzferkeln

Gegenstand und Fragestellung: Untersuchungen zur Wirkung von Galakturoniden als Futtermittelzusatz im Vergleich zum Leistungsförderer Flavophospholipol und einer Kontrollgruppe bei Absetzferkeln. Material und Methoden: In einer Fütterungsstudie wurden Galakturonide als Futterzusatz im Vergleich zu Flavophospholipol in der Ferkelaufzucht getestet (Galakturonide: 10 g bzw. 5 g/kg Futter, Flavophospholipol: 10 mg/kg Futter). Die Ferkel erhielten drei Tage vor bis 27 Tage nach dem Absetzen die verschiedenen Futterzusätze oder keinerlei Futterzusatz. Den Futterrationen der Gruppe 1 (n = 42) wurden Galakturonide, der Gruppe 3 (n = 42) Flavophospholipol und der Gruppe 2 (n = 40) kein derartiger Futterzusatz beigefügt. Von allen Ferkeln wurden rektale Kottupferproben in drei- bis siebentägigen Intervallen genommen und einer mikrobiologischen Untersuchung unterzogen. Ergebnisse: Bezüglich bakteriologischer Untersuchungsergebnisse (Inzidenz von hämolysierenden pathogenen E. coli, Serotypen, Antibiogramme), der Lebendmassezunahme und des Futteraufwandes ergaben sich keine signifikanten Unterschiede zwischen den verschiedenen Gruppen. Ein- bis mehrfach resistente hämolysierende E. coli wurden von Absetzferkeln aller Gruppen ausgeschieden. Schlussfolgerung: Die weitere Untersuchung von aus Pflanzen gewonnenen Futterzusätzen ist sinnvoll.

Leberegelbedingte Photodermatitis beim Rind

Zwei Fleckviehkühe wurden wegen Hauterkrankungen nach Weidegang an die II. Medizinische Universitätsklinik für Klauentiere der Veterinärmedizinischen Universität Wien überwiesen. Bei der klinischen Untersuchung waren die Veränderungen auf die unpigmentierten Bereiche der Haut begrenzt. Die Haut des Rückens, des Flotzmaules, der Augen und der Zitzen war am stärksten betroffen. Die Tiere zeigten Alopezie, Erythem, Schuppen- und Krustenbildung, seröse Exsudation, Hautverdickungen, Hautablösungen und Narbenbildung. Signifikante Abweichungen der klinischchemischen Parameter bestanden in einer erhöhten Serumenzymaktivität der GGT und GLDH. Das klinische Erscheinungsbild erwies sich als durch eine Leberschädigung bedingte Photodermatitis solaris. Die parasitologische Untersuchung einer Kotprobe und des Gallenblasenpunktats ergab einen hochgradigen Leberegelbefall. Mittels Ultraschalluntersuchung konnten massive Leberveränderungen wie Gallengangsverkalkungen und Abszesse diagnostiziert werden. Bei der pathomorphologischen Untersuchung wurde bei beiden Tieren eine Fasziolose in Verbindung mit hepatogener Photodermatitis festgestellt. Die Symptomatik sowie klinische und pathologische Befunde werden beschrieben und Differenzialdiagnosen diskutiert.

Experimental investigations on the B and T cell immune response in primary alveolar echinococcosis

Susceptibility/resistance of the intermediate host to alveolar echinococcosis (AE) seems to be based on hitherto unknown immunological mechanisms, possibly involving the activation of different CD4+ T cell immune responses (Th1/Th2). Mice of two strains previously characterized as 'susceptible' (C57BL/6 J) and 'resistant' (C57BL/10 J) to secondary AE were orally infected with eggs of Echinococcus multilocularis and the course of infection was analysed by macroscopical, pathohistological and immunohistochemical examinations of the lymphocytes and cytokines participating in the periparasitic granulomas and by serological examinations of cytokines and E. multilocularis-specific antibodies. Although differences in the extent of parasitic growth were seen between the two groups, the composition of the granulomas was quite similar with CD4+ cells being the dominant lymphocyte subpopulation, succeeded by B cells and CD8+ cells. Interferon (IFN)-gamma-, interleukin (IL)-2- and IL-4-expressing cells could not be detected in the lesions of the early phase of the infection, possibly indicating the host's immunosuppression, but were present at the end. IL-10 was the most prominent cytokine throughout the course of the disease. Serological analyses of the cytokine concentrations revealed small amounts at the beginning and high levels at the end of the infection. The pattern of cytokine response was similar for IL-4 in both strains, but different for IL-2 and IL-10 in the late phase, when the C57BL/10 J strain developed higher levels than the C57BL/6 J strain. Correspondingly only small amounts of immunoglobulin (Ig)M, IgG1, IgG2a and IgG3 could be detected at the beginning of disease, followed by higher levels at the end. The courses of antibody titres were similar in both groups except IgG3, which was more pronounced in the C57BL/10 J strain. Parasite-specific IgG2b could neither be detected in the C57BL/6 J nor in the C57BL/10 J strain by the test system used. The results of the study suggest both subsets of CD4+ T cells (Th1 and Th2) being involved in murine primary alveolar echinococcosis. A strict differentiation of mice in susceptible and resistant animals based on the activation of different CD4+ T cell immune responses (Th1 'resistant' and Th2 'susceptible') should be avoided.

Ultrasonographic appearance of normal superficial cervical and subiliac lymph nodes in cattle

The superficial cervical and the subiliac lymph nodes of 18 healthy, non-pregnant Simmental cows with a mean (sd) age of 5-6 (1.6) years were examined ultrasonographically in transverse and longitudinal planes with a real-time B-mode unit equipped with a 7.5 MHz linear-transducer. The position, demarcation and echogenicity of the lymph nodes were examined, and the craniocaudal and lateromedial diameters of each lymph node were measured three times within a period of six weeks. The pole to pole length of the lymph nodes was determined with a tape measure on the surface of the skin because the whole length could not be imaged in a single scan field. The gross anatomical and histological results showed that the lymph nodes were normal. Ultrasonographically, they were well demarcated from the adjoining muscular and subcutaneous tissue. Their internal structure was characterised by an anechoic to hypoechoic cortical zone corresponding to the lymphoid tissue, and an echogenic medullary zone, where the lymphatic sinuses converge towards the hilus and produce numerous acoustic interfaces. In all the lymph nodes, the hilar area had an echoic to hyperechoic appearance. The mean (sd) pole to pole length of the superficial cervical lymph nodes was 15.5 (3.2) cm and of the subiliac lymph nodes 13.5 (2.4) cm. The mean craniocaudal and lateromedial diameters of the superficial cervical lymph nodes were 2.8 (0.3) cm and 1.6 (0.3) cm, and those of the subiliac lymph nodes were 2.4 (0.4) cm and 1.1 (0.3) cm. The ultrasonographic morphology of these normal lymph nodes was consistent and provides basic reference data for the investigation of lymphadenopathies in cattle.

Cutaneous, multilocular T-cell lymphosarcoma in a horse--clinical, ultrasonographic and pathological findings

Clinical, ultrasonographic and pathological findings of a cutaneous, multilocular T-cell lymphosarcoma (malignant lymphoma) in a 13-year-old, brown Austrian warmblood mare are reported. The horse was under clinical observation, and the tumours were sonographically monitored over an 8 month period, revealing worsening of body condition, weight loss, lameness of the left hindlimb and a slight increase in the tumours size. Most of the tumours were covered by normal skin, one showed ulceration. Ultrasonography of the tumours allowed accurate anatomical localization in relation to the adjoining tissue, assessment of their internal structure, of involvement of adjacent muscles and of a regional lymph node, and it facilitated the percutaneous fine-needle aspiration. Necropsy confirmed muscular infiltration in three locations. Light microscopy and immunohistology led to the diagnosis of a T-cell lymphosarcoma.

Generation of effective cancer vaccines genetically engineered to secrete cytokines using adenovirus-enhanced transferrinfection (AVET)

Cancer vaccines are based on the concept that tumors express novel antigens and thus differ from their normal tissue counterparts. Such putative tumor-specific antigens should be recognizable by the immune system. However, malignant cells are of self origin and only poorly immunogenic, which limits their capability to induce an anticancer immune response. To overcome this problem, tumor cells have been isolated, genetically engineered to secrete cytokine gene products and administered as cancer vaccines. We used adenovirus-enhanced transferrinfection (AVET), which allows high-level transient transgene expression, to introduce cytokine gene expression vectors into murine melanoma cells. The efficiency of AVET makes laborious selection and cloning procedures obsolete. We administered such modified tumor cells as cancer vaccines to syngeneic animals and investigated their impact on the induction of anticancer immunity. We found that IL-2 or GM-CSF gene-transfected murine melanoma cells are highly effective vaccines. Both of these cytokine-secreting vaccines cured 80% of animals which bore a subcutaneous micrometastasis prior to treatment, and induced potent antitumor immunity. The generation of antitumor immunity by these cytokine-secreting vaccines requires three different steps: (1) tumor antigen uptake and processing by antigen-presenting cells (APCs) at the site of vaccination; (2) migration of these APCs into the regional lymph nodes where T-cell priming occurs; (3) recirculation of specific, activated T-cells that recognize distinct tumor load and initiate its elimination. Extending our previously reported studies, we have now comprehensively analysed the requirements for effective antitumor vaccination in animals. This may also become the basis for treatment of human cancer patients.

Priming of tumor-specific T cells in the draining lymph nodes after immunization with interleukin 2-secreting tumor cells: three consecutive stages may be required for successful tumor vaccination

Although both CD4+ and CD8+ T cells are clearly required to generate long-lasting anti-tumor immunity induced by s.c. vaccination with interleukin 2 (IL-2)-transfected, irradiated M-3 clone murine melanoma cells, some controversy continues about the site and mode of T-cell activation in this system. Macrophages, granulocytes, and natural killer cells infiltrate the vaccination site early after injection into either syngeneic euthymic DBA/2 mice or athymic nude mice and eliminate the inoculum within 48 hr. We could not find T cells at the vaccination site, which argues against the concept that T-cell priming by the IL-2-secreting cancer cells occurs directly at that location. However, reverse transcription-PCR revealed transcripts indicative of T-cell activation and expansion in the draining lymph nodes of mice immunized with the IL-2-secreting vaccine but not in mice vaccinated with untransfected, irradiated M-3 cells. We therefore propose that the antigen-presenting cells, which invade the vaccination site, process tumor-derived antigens and, subsequently, initiate priming of tumor-specific T lymphocytes in lymphoid organs. These findings suggest a three-stage process for the generation of effector T cells after vaccination with IL-2-secreting tumor cells: (i) tumor-antigen uptake and processing at the site of injection by antigen-presenting cells, (ii) migration of antigen-presenting cells into the regional draining lymph nodes, where T-cell priming occurs, and (iii) circulation of activated T cells that either perform or initiate effector mechanisms leading to tumor cell destruction.

Cancer vaccines: the interleukin 2 dosage effect

Cancer vaccines genetically engineered to produce interleukin 2 have been investigated intensively in a series of animal models and are at the point of entering into clinical trials. In this study we demonstrate a strong correlation between the rate of interleukin 2 production and the protection efficiency of murine S91 melanoma cell (clone M-3) vaccines. Best immunization is achieved with vaccines producing medium interleukin 2 levels of 1000-3000 units per 10(5) cells per day. Reduced interleukin 2 production evokes a corresponding decline in the number of successfully treated animals. Unexpectedly, when interleukin 2 expression is raised to high levels of 5000-7500 units per 10(5) cells per day, protection is completely absent because of impaired generation of tumor-specific cytotoxic T lymphocytes. In comparison, granulocyte-macrophage colony-stimulating factor as immunomodulator induces substantial immunization even at a moderate level of secretion and protects all animals at the maximal obtainable level of secretion. Our findings demonstrate the importance of the interleukin 2 level produced by genetically modified tumor cells and may have substantial impact for the clinical application of cancer vaccines.