Sailfish generate foraging opportunities for seabirds in multi-species predator aggregations.

While various marine predators form associations, the most commonly studied are those between subsurface predators and seabirds, with gulls, shearwaters or terns frequently co-occurring with dolphins, billfish or tuna. However, the mechanisms underlying these associations remain poorly understood. Three hypotheses have been proposed to explain the prevalence of these associations: (1) subsurface predators herd prey to the surface and make prey accessible to birds, (2) subsurface predators damage prey close to the surface and thereby provide food scraps to birds, and (3) attacks of underwater predators lower the cohesion of prey groups and thereby their collective defences making the prey easier to be captured by birds. Using drone footage, we investigated the interaction between Indo-Pacific sailfish (Istiophorus platypterus) and terns (Onychoprion sp.) preying on schooling fish off the eastern coast of the Malaysian peninsula. Through spatio-temporal analysis of the hunting behaviour of the two predatory species and direct measures of prey cohesion we showed that terns attacked when school cohesion was low, and that this decrease in cohesion was frequently caused by sailfish attacks. Therefore, we propose that sailfish created a by-product benefit for the bird species, lending support to the hypothesis that lowering cohesion can facilitate associations between subsurface predators and seabirds.

Animal board invited review: The need to consider emissions, economics and pig welfare in the transition from farrowing crates to pens with loose lactating sows.

In the development and implementation of housing systems for pigs, there has been a significant focus on pig welfare including loose housing of lactating sows either indoors or outdoors. However, it is equally important to consider the environmental and economic aspects of housing systems to ensure sustainability in livestock production. The aim of this work was to review the sustainability (societal and animal welfare, environmental and economic impact) of different approaches for housing farrowing and lactating sows in indoor environments. The review illustrates that like outdoor systems, indoor housing systems are challenged in meeting the three pillars of sustainability when changing the housing of lactating sows from conventional crates with permanent confinement to systems with temporary or zero-confinement. Increased space allowance increases sow welfare, but in addition, pen designs with increased space increase ammonia emission, investment and running costs. Furthermore, indoor loose lactation systems come with an increased risk for piglet mortality, which unless effectively managed, reduces animal welfare and the economic sustainability of the system. If farms retrofit existing buildings, the larger space per loose farrowing pen leads to a reduction in pen numbers and therefore herd size, reducing the farm profitability. If farmers choose to reduce herd size to meet requirements, welfare will be reduced while emissions will be increased as more sows are brought into production again in other countries, often in conventional systems with fully slatted flooring, to meet the demand for animal protein to feed the growing global population. The review indicates there are ways to house lactating sows loose indoors with increased opportunity to perform highly motivated species-specific behaviours compared to the conventional crates with continuous confinement. These systems can offer a lower risk for environmental impact and economic risk through reducing piglet mortality. Nevertheless, a trade-off for continual freedom of sow movement may be required as zero-confinement increases the risk of piglet mortality and increased emissions. It is important to raise awareness among citizens and policy makers that loose farrowing and lactating systems if applied today, come with a higher production cost and the risk of increased environmental impact. More research and development is needed in relation to the environmental and economic impact of these systems in order to give farmers the best information to invest in new and more sustainable production systems.

California sea lions interfere with striped marlin hunting behaviour in multi-species predator aggregations.

The open ocean offers a suite of ecological conditions promoting the occurrence of multi-species predator aggregations. These mixed predator aggregations typically hunt large groups of relatively small and highly cohesive prey. However, the mechanisms and functions of these mixed predator aggregations are largely unknown. Even basic knowledge of whether the predator species' interactions are mutualistic, commensal or parasitic is typically missing. Moreover, recordings of attack and capture rates of marine multi-species predator aggregations, which are critical in understanding how and why these interactions have evolved, are almost completely non-existent owing to logistical challenges. Using underwater video, we quantified the attack and capture rates of two high-trophic level marine predators, California sea lions (Zalophus californianus) and striped marlin (Kajikia audax) attacking schools of fishes in the Southern California Current System, offshore the Baja California Peninsula. Recording over 5000 individual attacks across 13 fish schools, which varied in species, size and predator composition, we found that sea lions kleptoparasitized striped marlin hunts and reduced the frequency of marlin attacks and captures via interference competition. We discuss our results in the context of the phenotypic differences between the predator species and implications for a better understanding of multi-species predator aggregations. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Mechanisms of prey division in striped marlin, a marine group hunting predator.

Many terrestrial group-hunters cooperate to kill prey but then compete for their share with dominance being a strong predictor of prey division. In contrast, little is known about prey division in group-hunting marine predators that predominately attack small, evasive prey (e.g. fish schools). We identified individual striped marlin (Kajikia audax) hunting in groups. Groups surrounded prey but individuals took turns attacking. We found that competition for prey access led to an unequal division of prey among the predators, with 50% of the most frequently attacking marlin capturing 70-80% of the fish. Neither aggression, body size nor variation in hunting efficiency explained this skewed prey division. We did find that newly arrived groups of marlin gained on average more access to the prey. This raises the possibility that newly arrived marlin were hungrier and more motivated to feed. However, this result does not necessarily explain the unequal prey division among the predators because the skew in prey captures was found at the level of these groups. Dynamic prey division is probably widespread but under-reported in marine group-hunters and the inability of individuals to monopolize prey until satiation likely reduces the importance of social hierarchies for prey division.

Oil gland and oil pores in billfishes: in search of a function.

Billfishes are well known for their distinctive elongated rostra, i.e. bills. The functional significance of billfish rostra has been frequently discussed and the recent discovery of an oil gland (glandula oleofera) at the base of the rostrum in swordfish, Xiphias gladius, has added an interesting facet to this discussion regarding the potential co-evolution of gland and rostra. Here, we investigated the oil gland and oil pores (through which the oil is brought to the skin surface) of four billfish species - swordfish, Atlantic blue marlin (Makaira nigricans), Indo-Pacific sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) - and provide detailed evidence for the presence of an oil gland in the last three. All four species had a high density of oil pores on the forehead which is consistent with the hypothesis of hydrodynamic benefits of the oil. The extension of the pores onto the front half of the rostrum in sailfish and striped marlin, but not in swordfish or blue marlin, suggests that the oil may have additional functions. One such function could be linked to the antibacterial and anti-inflammatory properties of the oil. However, the available evidence on predatory rostrum use (and hence the likelihood of tissue damage) is only partly consistent with the extension of pores on rostra across species. We conclude that the oil gland probably serves multiple, non-mutually exclusive functions. More detailed information on rostrum use in blue marlin and swordfish is needed to better link behavioural and morphological data with the aim of accomplishing a full comparative analysis.

Linking hunting weaponry to attack strategies in sailfish and striped marlin.

Linking morphological differences in foraging adaptations to prey choice and feeding strategies has provided major evolutionary insights across taxa. Here, we combine behavioural and morphological approaches to explore and compare the role of the rostrum (bill) and micro-teeth in the feeding behaviour of sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) when attacking schooling sardine prey. Behavioural results from high-speed videos showed that sailfish and striped marlin both regularly made rostrum contact with prey but displayed distinct strategies. Marlin used high-speed dashes, breaking schools apart, often contacting prey incidentally or tapping at isolated prey with their rostra; while sailfish used their rostra more frequently and tended to use a slower, less disruptive approach with more horizontal rostral slashes on cohesive prey schools. Capture success per attack was similar between species, but striped marlin had higher capture rates per minute. The rostra of both species are covered with micro-teeth, and micro-CT imaging showed that species did not differ in average micro-tooth length, but sailfish had a higher density of micro-teeth on the dorsal and ventral sides of their rostra and a higher amount of micro-teeth regrowth, suggesting a greater amount of rostrum use is associated with more investment in micro-teeth. Our analysis shows that the rostra of billfish are used in distinct ways and we discuss our results in the broader context of relationships between morphological and behavioural feeding adaptations across species.

Interactions between Plagiotremus spp., Labroides dimidiatus and their clients: evidence for behavioural niche partitioning.

This study employed community analysis and behavioural field observations to explore the inter-specific interactions between fangblenny species (Plagiotremus spp.), the cleaner wrasse Labroides dimidiatus and their target species and found that the presence of Plagiotremus spp. did not affect the total amount that L. dimidiatus cleaned but it did reduce the amount L. dimidiatus cleaned key prey species of the Plagiotremus spp. The behavioural interactions between adult L. dimidiatus and their clients changed in response to the presence of Plagiotremus spp., but the results suggested the potential cost of Plagiotremus spp. on L. dimidiatus may be offset by behavioural niche partitioning.

Donor life stage influences juvenile American eel Anguilla rostrata attraction to conspecific chemical cues.

The present study investigated the potential role of conspecific chemical cues in inland juvenile American eel Anguilla rostrata migrations by assessing glass eel and 1 year old elver affinities to elver washings, and elver affinity to adult yellow eel washings. In two-choice maze assays, glass eels were attracted to elver washings, but elvers were neither attracted to nor repulsed by multiple concentrations of elver washings or to yellow eel washings. These results suggest that A. rostrata responses to chemical cues may be life-stage dependent and that glass eels moving inland may use the odour of the previous year class as information to guide migration. The role of chemical cues and olfaction in eel migrations warrants further investigation as a potential restoration tool.

Crimson Spotted Rainbowfish (Melanotaenia duboulayi) Change Their Spatial Position according to Nutritional Requirement.

Decision making in moving animal groups has been shown to be disproportionately influenced by individuals at the front of groups. Therefore, an explanation of state-dependent positioning of individuals within animal groups may provide a mechanism for group movement decisions. Nutritional state is dynamic and can differ between members of the same group. It is also known to drive animal movement decisions. Therefore, we assayed 6 groups of 8 rainbowfish foraging in a flow tank. Half of the fish had been starved for 24h and half had been fed 1h prior to experimental start. Groups were assayed again one week later but individuals were allocated to the opposite nutritional treatment. During the assay the positions of individually identified fish were recorded as were the number of food items they each ate and the position within the group they acquired them from. Food-deprived fish were more often found towards the front of the shoal; the mean weighted positional score of food-deprived fish was significantly larger than that of well-fed fish. Individuals were not consistent in their position within a shoal between treatments. There was a significant positive correlation between mean weighted positional score and number of food items acquired which displays an obvious benefit to front positions. These results suggest that positional preferences are based on nutritional state and provide a mechanism for state-dependent influence on group decision-making as well as increasing our understanding of what factors are important for group functioning.

Pasteurellaceae bacteria from the oral cavity of Tasmanian devils (Sarcophilus Harrisii) show high minimum inhibitory concentration values towards aminoglycosides and clindamycin.

UNLABELLED: Threatened by Devil Facial Tumor Disease, the Tasmanian devil populations are vulnerable and decreasing. Additionally, the devils' biting behaviour elevates their risk of acquiring bite wound infections caused by members of the bacterial Pasteurellaceae family that are natural inhabitants of the oral microbiota. In medical management of such bite wounds, antimicrobial susceptibility profiles are crucial. Prior to this investigation, no available data on minimal inhibitory concentration (MIC) values existed. A total of 26 isolates obtained from the oral cavity of 26 healthy Tasmanian devils were tested for their antimicrobial susceptibility by broth micro dilution. Most prominently, high MIC values for clindamycin (≥4 µg ml(-1) ), gentamicin (≥8 µg ml(-1) ) and amikacin (≥32 µg ml(-1) ), were observed for 92, 77 and 73% of the strains tested respectively. This study may be used as a guideline for antimicrobial therapy against bite wound infections caused by Pasteurellaceae originating from the oral cavity of Tasmanian devils. SIGNIFICANCE AND IMPACT OF THE STUDY: Tasmanian devils' aggressive behaviour makes bite wounds in fellow devils and human caretakers a common entity. Pasteurellaceae bacteria are common inhabitants of the oral microbiota of Tasmanian devils and a likely cause of bite wound infections. Here, for the first time, we report antimicrobial sensitivity profiles from a broad collection of Pasteurellaceae isolates obtained from the oral cavity of Tasmanian devils. Low MIC values were observed for the majority of the 22 antimicrobial agents included, yet nearly all strains were tolerant to clindamycin and the aminoglycosides. The work can serve as a guide for clinicians involved in treatment of bite wounds inflicted by devils in animals and humans.

Red, far-red, and near infrared photoswitches based on azonium ions.

Azonium ions formed by p-amino substituted azo compounds with both ortho- and meta-methoxy substituents exhibit strong absorbance in far-red and near infrared spectral region. The compounds undergo robust photoswitching in aqueous solution and exhibit a range of thermal relaxation rates from 10 µs-100 ms.

Osmoregulation by juvenile brown-banded bamboo sharks, Chiloscyllium punctatum, in hypo- and hyper-saline waters.

While there is a considerable body of work describing osmoregulation by elasmobranchs in brackish and saltwater, far fewer studies have investigated osmoregulation in hypersaline waters. We examined osmo- and ionoregulatory function and plasticity in juvenile brown-banded bamboo sharks, Chiloscyllium punctatum, exposed to three experimental salinities (25, 34 and 40‰) for two weeks. C. punctatum inhabits sheltered coastal areas and bays which can naturally become hypersaline as a consequence of evaporation of water but can also become hyposaline during flood events. We hypothesised that C. punctatum would demonstrate a phenotypically plastic osmoregulatory physiology. Plasma osmolality, urea, Na(+) and Cl(-) levels increased significantly with increasing environmental salinity. Rectal gland and branchial sodium-potassium ATPase (NKA) activities were unaffected by salinity. Using immunohistochemistry and Western Blotting we found evidence for the presence of the key ion-regulatory proteins vacuolar H(+)-ATPase (VHA), pendrin (Cl(-)/HCO3(-) co-transporter) and the Na(+)-H(+) exchanger isoform 3 (NHE3) in discrete cells within the branchial epithelia. These results indicate that C. punctatum is a partially euryhaline elasmobranch able to maintain osmo- and ionoregulatory function between environmental salinities of 25‰ and 40‰. As suggested for other elasmobranchs, the gills of C. punctatum likely play a limited role in maintaining Na(+) homeostasis over the salinity range studied, but may play an important role in acid-base balance.

Modulation of central leptin sensitivity and energy balance in a rat model of diet-induced obesity.

AIM: The aim of this study was to further explore the time-dependent changes in leptin sensitivity using a rat model of dietary fat-induced obesity and to investigate the potential mechanisms governing these changes. METHODS: We used male, adult Sprague-Dawley rats that were fed either a standard laboratory chow diet (3% fat) or a high-saturated fat (HF) diet (60% fat) for 2 or 5 weeks. Energy balance (body weight, energy intake and energy expenditure); sensitivity to central leptin and central alpha-melanin stimulating hormone (alpha-MSH) administration and expression levels of hypothalamic ObRb, signal transducers and activators of transcription factor (STAT)-3 phosphorylation, suppressor of cytokine signalling-3 (SOCS-3), proopiomelanocortin (POMC) processing hormones (prohormone convertase-1 and prohormone convertase-2) and neuropeptide Y (NPY) were measured. RESULTS: After 2 weeks of feeding HF diet, there was an increase in total energy intake (TEI) but a reduction in food intake as measured by the mass of food ingested. Body weight at this time was not significantly different between the two diet groups; however, white adipose tissue (WAT) weight was significantly greater in the HF-fed rats than in the chow-fed rats. In addition, spontaneous physical activity levels were increased, but no changes were observed in resting energy expenditure. Furthermore, chow-fed lean rats responded to central leptin administration by reducing the energy intake by approximately 67 kJ compared with saline treatment (p < 0.05), while the HF-fed diet-induced obese (DIO) rats responded by reducing their energy intake by approximately 197 kJ compared with saline treatment (p < 0.05). After 5 weeks of feeding HF diet, TEI remained significantly higher, body weight was significantly increased by 5% in the HF-fed rats and WAT weight was significantly heavier in HF-fed rats than in the chow-fed lean rats. After leptin treatment, the chow-fed lean rats reduced their energy intake by approximately 97 kJ (p < 0.05); yet, leptin had no significant effect in the HF-fed DIO rats. ObRb protein expression, STAT-3 phosphorylation levels, content and messenger RNA (mRNA) expression of NPY, SOCS-3 mRNA and protein expression and energy intake response to central alpha-MSH administration were not altered after HF diet feeding. CONCLUSION: These results suggest that early in the course of HF diet-induced weight gain, there was a period of central leptin hypersensitivity, and as the obesity progresses, central leptin insensitivity develops. This insensitivity does not appear to be explained by a downregulation of ObRb protein levels, reduced leptin signalling, an increase in either SOCS-3 or NPY expression or reduced function of the melanocortin system. The effect of an HF diet on other actions of leptin such as its effect on the endocannabinoid system should be investigated.

Differential protease, innate immunity, and NF-kappaB induction profiles during lung inflammation induced by subchronic cigarette smoke exposure in mice.

Cigarette smoke exposure is a major determinant of adverse lung health, but the molecular processes underlying its effects on inflammation and immunity remain poorly understood. Therefore, we sought to understand whether inflammatory and host defense determinants are affected during subchronic cigarette smoke exposure. Dose-response and time course studies of lungs from Balb/c mice exposed to smoke generated from 3, 6, and 9 cigarettes/day for 4 days showed macrophage- and S100A8-positive neutrophil-rich inflammation in lung tissue and bronchoalveolar lavage (BAL) fluid, matrix metalloproteinase (MMP) and serine protease induction, sustained NF-kappaB translocation and binding, and mucus cell induction but very small numbers of CD3+CD4+ and CD3+CD8+ lymphocytes. Cigarette smoke had no effect on phospho-Akt but caused a small upregulation of phospho-Erk1/2. Activator protein-1 and phospho-p38 MAPK could not be detected. Quantitative real-time PCR showed upregulation of chemokines (macrophage inflammatory protein-2, monocyte chemoattractant protein-1), inflammatory mediators (TNF-alpha, IL-1beta), leukocyte growth and survival factors [granulocyte-macrophage colony-stimulating factor, colony-stimulating factor (CSF)-1, CSF-1 receptor], transforming growth factor-beta, matrix-degrading MMP-9 and MMP-12, and Toll-like receptor (TLR)2, broadly mirroring NF-kappaB activation. No upregulation was observed for MMP-2, urokinase-type plasminogen activator, tissue-type plasminogen activator, and TLRs 3, 4, and 9. In mouse strain comparisons the rank order of susceptibility was Balb/c > C3H/HeJ > 129SvJ > C57BL6. Partition of responses into BAL macrophages vs. lavaged lung strongly implicated macrophages in the inflammatory responses. Strikingly, except for IL-10 and MMP-12, macrophage and lung gene profiles in Balb/c and C57BL/6 mice were very similar. The response pattern we observed suggests that subchronic cigarette smoke exposure may be useful to understand pathogenic mechanisms triggered by cigarette smoke in the lungs including inflammation and alteration of host defense.

Evidence for an interaction between neuropeptide Y and the melanocortin-4 receptor on feeding in the rat.

The hypothalamus is a critical centre for the control of appetite. Neuropeptide Y (NPY) and alpha-melanocyte stimulating hormone (alpha-MSH) exert opposing effects on feeding and substantial neuroanatomical evidence exists to suggest these hypothalamic peptides may interact to alter feeding behaviour. We have examined central interactions between these two peptide systems on food intake in satiated male Sprague-Dawley rats. NPY-induced (1 nmol; i.c.v.) food intake was significantly attenuated by subsequent alpha-MSH administration (1 and 4 nmol; i.c.v.) at 1 h post-injection and persisted for the entire 4 h observation period (P<0.05). Central administration of the selective MC4-R antagonist HS014 (0.5 nmol) significantly increased food intake compared to saline-vehicle (P<0.05). However, co-administration of HS014 (0.5 nmol) and NPY (0.5 and 1 nmol) did not increase feeding compared to either dose of NPY alone. These results taken together provide some evidence for an interaction between these mediators in the control of food intake.

Enhanced binding of low-affinity antibodies interacting simultaneously with targeted cell surface molecules and Fc receptor.

The possibility that different forms of class I molecules might be expressed on the cell surface of lymphocytes has been investigated periodically over the past several decades. A series of major histocompatibility complex (MHC) class I-specific monoclonal antibodies, including the commonly used antibodies 64-3-7 and 25-D1.16, bind B cells differentially, suggesting the existence of differentially expressed class I-associated cell surface determinants on B lymphocytes. However, the ability of antibodies to bind cells is determined by the sum of interactions between the antibodies and the molecules expressed on the cell surface. The interactions of class I-specific antibodies with B cells were dissected, revealing dual specificity of the antibodies for the targeted class I molecules, as well as to Fc receptors preferentially expressed by B cells. We demonstrate that antibodies simultaneously bind targeted class I molecules and Fc receptors expressed on the surface of B cells. Simultaneous binding to two cell surface structures significantly enhances the class I-specific binding pattern of certain antibodies by increasing their avidity, leading to apparent cell-specific differences in MHC expression patterns. We conclude that no differences in MHC structures need be postulated to account for the observed binding patterns.

Enhanced inhibitory feeding response to alpha-melanocyte stimulating hormone in the diet-induced obese rat.

A dysregulation in the hypothalamic neuropeptide systems involved in the control of appetite has previously been shown in models of diet-induced obesity. In the present study, male Sprague-Dawley rats were rendered obese by a highly palatable cafeteria-style diet over 20 weeks, while control rats had access to standard laboratory chow. Feeding responses to alpha-melanocyte stimulating hormone (alpha-MSH), an anorectic peptide and neuropeptide Y (NPY), a potent orexigenic agent were investigated in diet-induced obese and control animals. In addition, endogenous hypothalamic peptide levels were determined in these animals. Intracerebroventricular injections of either 4 nmol alpha-MSH or saline vehicle were given 10 min prior to the onset of the dark phase. Diet-induced obese rats had significantly enhanced nocturnal inhibitory feeding responses to alpha-MSH (P<0.05). The orexigenic feeding response induced by 1 nmol NPY was similar for both groups. At sacrifice, both alpha-MSH and NPY peptide content were selectively reduced in the paraventricular nucleus (PVN) of these animals (P<0.05). Although diet-induced obesity had no effect on responses to NPY, the significantly greater inhibition of nocturnal feeding by alpha-MSH and reduction in PVN alpha-MSH peptide level, suggests melanocortinergic signalling may be reduced in obesity which may account for the hyperphagia of these animals when presented with a palatable diet.

Prevalent class I-restricted T-cell response to the Theiler's virus epitope Db:VP2121-130 in the absence of endogenous CD4 help, tumor necrosis factor alpha, gamma interferon, perforin, or costimulation through CD28.

C57BL/6 mice mount a cytotoxic T-lymphocyte (CTL) response against the Daniel's strain of Theiler's murine encephalomyelitis virus (TMEV) 7 days after infection and do not develop persistent infection or the demyelinating syndrome similar to multiple sclerosis seen in susceptible mice. The TMEV capsid peptide VP2121-130 sensitizes H-2Db+ target cells for killing by central-nervous-system-infiltrating lymphocytes (CNS-ILs) isolated from C57BL/6 mice infected intracranially. Db:VP2121-130 peptide tetramers were used to stain CD8(+) CNS-ILs, revealing that 50 to 63% of these cells bear receptors specific for VP2121-130 presented in the context of Db. No T cells bearing this specificity were found in the cervical lymph nodes or spleens of TMEV-infected mice. H-2(b) mice lacking CD4, class II, gamma interferon, or CD28 expression are susceptible to persistent virus infection but surprisingly still generate high frequencies of CD8(+), Db:VP2121-130-specific T cells. However, CD4-negative mice generate a lower frequency of Db:VP2121-130-specific T cells than do class II negative or normal H-2(b) animals. Resistant tumor necrosis factor alpha receptor I knockout mice also generate a high frequency of CD8(+) CNS-ILs specific for Db:VP2121-130. Furthermore, normally susceptible FVB mice that express a Db transgene generate Db:VP2121-130-specific CD8(+) CNS-ILs at a frequency similar to that of C57BL/6 mice. These results demonstrate that VP2121-130 presented in the context of Db is an immunodominant epitope in TMEV infection and that the frequency of the VP2121-130-specific CTLs appears to be independent of several key inflammatory mediators and genetic background but is regulated in part by the expression of CD4.

Canine silica urolithiasis. Risk factors, detection, treatment, and prevention.

Uroliths containing 70% or greater silica comprise approximately 1% of the canine uroliths submitted to the Minnesota Urolith Center. Male dogs are far more commonly affected than females. In our series, 84 different breeds were affected. Currently available data suggest dietary factors play a role in their formation. Diagnosis is facilitated by the characteristic jackstone configuration of silica uroliths, but must be confirmed by quantitative analysis. Voiding urohydropropulsion or surgery are currently the most practical methods of removal of silica uroliths.

Retroviral-mediated expression of an MHC class I-restricted T cell receptor in the CD8 T cell compartment of bone marrow-reconstituted mice.

The introduction of cloned T cell receptor (TCR) genes into bone marrow cells could provide a way to increase the frequency of tumor- or pathogen-specific cytotoxic T lymphocyte (CTL) precursors. We demonstrate here the ability of a retroviral vector to direct expression of a Valpha15/Vbeta13 MHC class I-restricted TCR in lethally irradiated mice reconstituted with transduced bone marrow cells. We have detected retroviral-mediated TCR expression by flow cytometry 6-19 weeks after transplantation in C57L (Vbeta13(-/-)) and Rag1(-/-) bone marrow-reconstituted mice, and in C57BL/6 hosts reconstituted with transduced C57BL/6-Rag1(-/-) bone marrow. Southern analysis confirmed the presence of integrated provirus and revealed that the frequency of transduction is greater than the frequency of cell surface TCR expression. Although TCR expression on Vbeta13+ transduced cells is lower than endogenous TCR levels, it is largely confined to CD4+CD8+ (thymus) and CD8+ (thymus and spleen) T cells. In Rag1(-/-) mice, which display a developmental arrest of thymocytes at the immature CD4-CD8- stage, retrovirus-mediated TCR expression selectively rescues CD4+CD8+ and CD8+ populations. These results indicate that the ectopically expressed TCR is functional during T cell development. Furthermore, we have observed Vbeta13+ TCR expression by up to 13% of peripheral CD8+ T cells in C57L and C57BL/6 hosts. This represents a substantial increase relative to total Vbeta13 frequency in normal C57BL/6 mice (3-5%), and an even greater increase over the estimated frequency of CTL precursors of a defined specificity (10(-5)-10(-4)). Our findings indicate that TCR gene transfer can be used to develop new approaches to immunotherapy, and provide the basis for further studies examining the contribution of retrovirus-mediated TCR expression to an antigen-specific CTL response.