Estimating the average distribution of Antarctic krill Euphausia superba at the northern Antarctic Peninsula during austral summer and winter.

This study was performed to aid the management of the fishery for Antarctic krill Euphausia superba. Krill are an important component of the Antarctic marine ecosystem, providing a key food source for many marine predators. Additionally, krill are the target of the largest commercial fishery in the Southern Ocean, for which annual catches have been increasing and concentrating in recent years. The krill fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which has endorsed a new management framework that requires information about the spatial distribution and biomass of krill. Here, we use krill density estimates from acoustic surveys and a GAMM framework to model habitat properties associated with high krill biomass during summer and winter in the northern Antarctic Peninsula region, an area important to the commercial fishery. Our models show elevated krill density associated with the shelf break, increased sea surface temperature, moderate chlorophyll-a concentration and increased salinity. During winter, our models show associations with shallow waters (< 1500 m) with low sea-ice concentration, medium sea-level anomaly and medium current speed. Our models predict temporal averages of the distribution and density of krill, which can be used to aid CCAMLR's revised ecosystem approach to fisheries management. Our models have the potential to help in the spatial and temporal design of future acoustic surveys that would preclude the need for modelled extrapolations. We highlight that the ecosystem approach to fisheries management of krill critically depends upon such field observations at relevant spatial and temporal scales. Supplementary Information: The online version contains supplementary material available at 10.1007/s00300-022-03039-y.

Specificity of the helper T cell for the cytolytic T lymphocyte response to influenza viruses.

We have described a model system in which helper T cells are required to mount a primary antiviral cytolytic T lymphocyte response. The radioresistant helper cell can be found in the spleens of mice that have been immunized subcutaneously with influenza viruses 6-8 d previously. These helper cells appear to be type specific but cross-reactive among the subtypes of influenza A viruses. The phenotypes of the interacting cell populations were determined.

Ia expression by vascular endothelium is inducible by activated T cells and by human gamma interferon.

We have used monoclonal antibody binding, measured by radioimmunoassay, fluorescence flow cytometry, and ultrastructural immunocytochemistry, to measure expression of Ia antigens on cultured human umbilical vein endothelial (HUVE) cells. Under standard culture conditions, HUVE cells do not express Ia antigens. However, treatment of primary HUVE cultures with phytohemagglutinin induces the expression of Ia antigens. Every endothelial cell in the culture becomes Ia-positive and endothelial cells appear to synthesize Ia. HLA-A,B is concomitantly increased. The expression of Ia appears to be mediated by T cells because (a) pretreatment of primary HUVE cultures with OKT3 plus complement blocks the action of the lectins but not of medium conditioned by lectin-activated peripheral blood mononuclear cells; (b) co-culture of endothelial cells with allogeneic T cells, in the absence of lectin, also induces endothelial Ia; and (c) human immune (gamma) interferon, produced by Chinese hamster ovary cells transfected with the human gamma interferon gene, directly induces endothelial Ia. During co-culture with lymphocytes, about one-third of the endothelial cells are Ia-positive after 24 h and all of the endothelial cells are Ia-positive by 72 h. Proliferation of allogeneic T cells starts by 96 h and peaks at 144 h. Thus, endothelial Ia appears sufficiently early to be a determinant for the proliferation of allogeneic T cells. Inducible expression of Ia by endothelium may be important both for allograft rejection and for recruitment of circulating T cells into the site of an immune response.

Dissection of serological and cytolytic T lymphocyte epitopes on murine major histocompatibility antigens by a recombinant H-2 gene separating the first two external domains.

A novel H-2 gene in which the first external (N) domain of the H-2Ld antigen was replaced with that of the H-2Dd antigen was constructed and introduced into L cells. A transformant expressing the products of the hybrid gene was studied for binding to monoclonal antibodies specific for H-2Ld and H-2Dd antigens. It was found that serological determinants are distributed both in the N (Dd) and Cl (Ld) domains. Determinants recognized by allospecific cytotoxic T lymphocytes (CTLs) and virus-specific CTLs also mapped to the N and Cl domains. Determinants recognized by vesicular stomatitis virus (VSV)-specific effect cells, however, were not present on the recombinant molecule. These results show that a recombinant gene of two H-2 antigens in which the first external domain has been reshuffled can express a functional H-2 antigen that can then be used to map serological and CTL determinants to specific domains.

Evidence for genetic restriction in the suppression of erythropoiesis by a unique subset of T lymphocytes in man.

The suppression of erythropoiesis by lymphocytes from patients with a T cell lymphoproliferative syndrome and pure erythrocyte aplasia has been previously demonstrated. To study the nature of the suppressor cell and possible genetic restriction of this suppression, we investigated a patient with severe anemia, splenomegaly, lymphocytosis, and erythroid aplasia. A 3-mo course of low-dose daily oral cyclophosphamide achieved a complete remission for over 12 mo. The surface phenotype of his lymphocytes was analyzed by means of antibodies to lineage, differentiation, and activation-specific surface antigens. The cells expressed mature T cell antigens T3, T8, and T11, while lacking T1. Immature T cell, B cell, and the monocyte-specific antigen Mo2 were absent, while Mo1, a monocyte-associated antigen not normally expressed on T cells, was present. T10 and Ia expressed as activation antigens were also present. The cells, cryopreserved at diagnosis, were thawed and co-cultured in plasma clot with patient remission marrow samples at T cell/bone marrow ratios of 1:1 and 2:1. There was nearly 90% suppression of erythroid colony-forming unit expression and 60% suppression of erythroid burst-forming unit expression at 2:1 T cell to bone marrow ratios and somewhat less suppression at 1:1. Granulocyte/macrophage progenitor expression was unaffected. Erythroid progenitor differentiation in the marrows of two HLA identical siblings was similarly suppressed. The cells were co-cultured with the marrows of nine nonrelated donors to investigate the potential genetic restriction of this suppression. Colony suppression equal to that observed in the marrow of the patient and his siblings was found in studies of two partially HLA identical individuals. No suppression was detected in marrow co-cultures of two entirely HLA dissimilar individuals. These results show that suppression of erythropoiesis by a unique subset of T8, Mo1, Ia-positive lymphocytes isolated from a patient with lymphocytosis and erythrocyte aplasia is genetically restricted.

Human dermal fibroblasts present tetanus toxoid antigen to antigen-specific T cell clones.

Cultured human dermal fibroblasts treated with immune interferon express HLA-DR antigens. We report here that DR-positive fibroblasts present tetanus toxoid (TT) to autologous TT-specific monoclonal helper T cells vigorously depleted of monocytes by passage over Sephadex G10 columns followed by treatment with the monoclonal antibodies (mAb) OKM1 and Leu M1 plus complement. The extent of T cell proliferation in response to TT presented by DR-positive fibroblasts was similar to that elicited using monocytes as antigen-presenting cells. The proliferative response was TT dependent, antigen specific, depended upon DR expression by fibroblasts, appeared MHC restricted, and was completely blocked by mouse mAb to HLA-DR but not by mAb to HLA-A,B, or DQ. DR-positive fibroblasts pulsed with TT were similarly effective in antigen presentation. In summary, immune interferon-stimulated human dermal fibroblasts can substitute for classical antigen-presenting cells in antigen-specific proliferative responses. Since fibroblasts are a ubiquitous cell type in the body, they may play a significant role in the immunobiology of the host.

H-2Ld antigen encoded by a recombinant retrovirus genome is expressed on the surface of infected cells.

A recombinant murine retrovirus was constructed which contains, within its genome, a truncated version of the gene encoding the murine H-2Ld major histocompatibility antigen. The H-2Ld gene, which was inserted 3' of the env splice acceptor site in the recombinant retrovirus MSV-neo, lacked the 5' promoter and TATA sequences and the 3' transcription termination and polyadenylate addition sites of the normal H-2Ld gene. Transfection of the MSV-neo/H-2Ld plasmid (pLTV-11) into Y-2 cells resulted in the production of the transmissible recombinant retrovirus LTV-11. Cells infected with LTV-11 virus were resistant to the eucaryotic antibiotic G418 and expressed H-2Ld on the cell surface. These infected cells contained a viral RNA species which possessed both the H-2Ld and the neomycin resistance gene sequences but did not contain significant levels of the smaller H-2Ld-specific mRNA. The H-2Ld antigen expressed on the surface of infected cells functioned as a target for cytolytic T cells specific for the H-2Ld antigen.

Biochemical and functional analyses of a secreted H-2Ld molecule.

A truncated H-2Ld gene was constructed by deleting the transmembrane and cytoplasmic exons. The truncated H-2Ld gene was introduced into mouse L cells using the thymidine kinase gene as a selectable marker. Transformants were isolated and screened for the presence of truncated H-2Ld antigen. The truncated H-2Ld gene product was present in both the cytoplasm and culture medium, but not on the cell surface. The truncated H-2Ld antigen was stable in culture medium for at least 9 h and was secreted into the medium at a rate similar to the kinetics with which complete H-2 antigens reach the cell surface. Transformants expressing the truncated H-2Ld molecule were not recognized by cytotoxic T lymphocytes specific for the H-2Ld antigen.

IL-12 and viral infections.

Interleukin-12 activates natural killer cells and promotes the differentiation of Th1 CD4+ cells; it is a critical factor in viral immunity. IL-12 is secreted by antigen presenting cells including dendritic cells, macrophages and astrocytes, both in tissues and in secondary lymphoid organs. Experimental studies have shown that administration of the cytokine rapidly activates both innate and specific immune responses; this results in enhanced host cellular responses and generally, promotes clearance of virus and host recovery from infection. The observations of many laboratories, studying viral immunity to both RNA and DNA based pathogens, are summarized.

Innate immune responses in viral encephalitis.

The innate immune system is multifaceted, comprised of preformed factors, cells, and many proteins and lipid mediators produced by those cells. In the CNS these are critical in initiation and amplification of the inflammatory response and in the subsequent elicitation of the specific T cell response to viral encephalitis. Cells that are resident in brain parenchyma and peripheral cells that are recruited both play key roles in the hosts's responses. Unlike the peripheral compartments, in the CNS, non-cytolytic means of eliminating viral infections have been critical, since, in contrast to columnar epithelial cells, neurons are non-renewing. When the innate immune responses are inefficient or absent in viral encephalitis, pathology is more likely. Much more work remains to elucidate all of the critical cells and their mediators, as well as to develop new therapies for infections of the CNS.

Interferon-gamma induced type I nitric oxide synthase activity inhibits viral replication in neurons.

Type I NOS expression increases in OB neurons during VSV infection. Immunocytochemical staining of NB41A3 cells indicates constitutive expression of interferon (IFN)-gamma receptor and type I NOS. IFN-gamma treatment of NB41A3 cells increased NO production and type I NOS protein. In vitro replication of VSV, polio virus type I, and Herpes Simplex virus type I (HSV-1) is significantly inhibited by IFN-gamma induced type I NOS and antagonized by NOS inhibitors. In contrast, while IFN-gamma treatment inhibited influenza and Sindbis virus replication, a different pathway(s) was involved. The isoform-selective NOS inhibitor. 7-nitroindazole (7NI) was used to treat mice, resulting in a 10-fold higher titer of virus in brain homogenates, and abrogated the recovery-promoting effect of interleukin-12 treatment. Thus, IFN-gamma induced type I NOS activity may play an important role in host immunity against neurotropic viral infections.

Leukotrienes play protective roles early during experimental VSV encephalitis.

Leukotrienes (LT) are potent lipid mediators of inflammation. 5-Lipoxygenase (5-LO) is the key enzyme in the conversion of arachidonic acid to LT. There are four LT: LTB(4), LTC(4), LTD(4) and LTE(4). LT have been extensively studied in airway inflammation but little is known about their roles in viral infection in the CNS. LTB(4) is a chemoattractant for neutrophils. In this work, we studied the roles of LT in acute vesicular stomatitis virus (VSV) encephalitis. Two methods were used to disrupt 5-LO activity: mice were treated with Zileuton, an enzyme antagonist, or 5-LO genetic knockout mice were used. We found that inhibition or deletion of 5-LO resulted in: (a) impaired process of neutrophil infiltration into the CNS early during viral infection; (b) fewer neurons expressed nitric oxide synthase-1 (NOS-1); (c) higher viral titers 1 day after viral infection; and (d) increased disruption of blood brain barrier (BBB). Our studies suggest that LT are important innate immune players during VSV pathogenesis and are beneficial to the host in early control of viral replication in the CNS.

Sex differences in susceptibility to viral infection of the central nervous system.

We have characterized striking differences in recovery of male and female BALB/c and BALB/c-H-2dm2 (dm2) mice from an experimental neurotropic viral infection of the central nervous system (CNS). Following intranasal inoculation of vesicular stomatitis virus (VSV), assays of tissue homogenates from female mice produced lower viral titers. There was also a significant reduction in the spread of virus from the rostral to caudal end of the brain in female mice. Enhanced recovery by female mice of both strains in response to this viral insult correlates with increased levels of Nitric Oxide Synthase (NOS) types I, II, and III expression, an increased prevalence of reactive astrocytes, earlier and enhanced levels of expression of Major Histocompatibility Complex (MHC) class II molecules on astrocytes, endothelial and microglial cells, and increased T cell infiltration in the female BALB/c mouse. Taken together, these findings document sexual dimorphism in CNS immunity, and may provide an understanding of some of the mechanisms underlying many sex-biased diseases.

Interleukin-12 promotes recovery from viral encephalitis.

Infusion of interleukin-12 (IL-12) enhances recovery from lethal experimental vesicular stomatitis virus (VSV) infection of the central nervous system (CNS). Interleukin-12 treatment resulted in: 1) increased survival frequency; 2) faster recovery from weight loss; 3) substantially decreased VSV titers in brain homogenates and diminished immunohistochemical detection of VSV antigens in tissue sections; 4) earlier and increased CNS expression of types 1, 2, and 3 nitric oxide synthase (NOS) and both major histocompatibility complex (MHC) class I and class II antigens; 5) earlier and increased blood and CNS levels of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). These results suggest that IL-12 enhances recovery from VSV infection of the CNS.

Host immune response to vesicular stomatitis virus infection of the central nervous system in C57BL/6 mice.

In this report, the kinetics of cellular inflammatory changes in the brain of vesicular stomatitis virus (VSV)-infected C57BL/6 (B6) mice was determined. The behavior and survival rate of infected B6 were carefully monitored each day. Infectious viral titers and VSV antigen distribution were determined at several time points during the course of infection. Strong activation of both astrocytes and microglia was observed after VSV infection. Induction of type II nitric oxide synthase (iNOS) was detected in activated microglia in the olfactory bulb (OB) starting at day 4 postinfection. Induced expression of major histocompatibility complex (MHC) molecules and rapid infiltration of both T cells and natural killer (NK) cells were detected in the VSV-infected CNS. Collectively, these data indicate that the response to CNS infection in B6 mice, which is often primarily Th1 in characteristics, is comparable to BALB/c mice, a strain that often shows a Th2-dominated immune response.

Delayed administration of interleukin-12 is efficacious in promoting recovery from lethal viral encephalitis.

Vesicular stomatitis virus (VSV) applied intranasally to mice initially infects the olfactory receptor neurons, and then spreads quickly to the rest of the central nervous system (CNS). Previously, we have shown that the cytokine interleukin-12 (IL-12) has a significant survival and recovery promoting effect in mice infected with VSV when administered at the time of infection. The question of whether IL-12 is efficacious under the more clinically relevant condition of post-infection administration was explored. The data show that when IL-12 is administered post-infection, it is as effective as at the time of infection.

The role of interleukin-18 in vesicular stomatitis virus infection of the CNS.

Intranasal application of vesicular stomatitis virus (VSV) results in the initial infection of the olfactory receptor neurons and a rapid progression of the virus through the mouse central nervous system (CNS). Interleukin-18 (IL-18) is an 18.3-kd cytokine that induces interferon gamma (IFN-gamma) production in mice. IL-18 is synthesized as an inactive precursor that is cleaved and activated by caspase-1/interleukin-1beta converting enzyme (ICE). IL-18 shares several biological properties with IL-12, including the ability to induce IFN-gamma production in T lymphocytes and natural killer (NK) cells. In the CNS, microglia and astrocytes produce IL-18 and IL-12. We have previously shown that IL-12 promotes recovery from VSV encephalitis. This led us to examine the potential role of IL-18 in the pathogenesis of VSV encephalitis. We show that both IL-18 and caspase-1 mRNA are consistently present in the CNS of mice. The addition of exogenous IL-18 to cell cultures does not affect the production of VSV, and addition of exogenous IL-18 at the time of infection does not alter the morbidity or mortality of BALB/c mice. In vitro studies with neutralizing monoclonal antibody to IL-18 had no effect. From these results we conclude that in this system and under the experimental conditions used, unlike IL-12 and IFN-gamma, IL-18 does not play a significant role in the host response to VSV infection.

Interactions of T lymphocytes with human vascular endothelial cells: role of endothelial cells surface antigens.

We have studied the interactions of peripheral blood T lymphocytes with cultured human vascular endothelial cells, focusing upon endothelial cell surface antigens important for T cell recognition. Under standard culture conditions endothelial cells express class I but not class II major histocompatibility complex (MHC) antigens. However, class II antigens may be induced by activated T cells or T cell products, including the lymphokine immune interferon. Immune interferon concomitantly increases class I antigen expression and causes a change in cell shape. In addition to vascular endothelial cells, we have found that vascular smooth muscle cells and human dermal fibroblasts may also be induced by immune interferon to express class II antigens. All known human class II antigens are induced (i.e. HLA-DR, DC and SB) as is the associated invariant chain. Induced antigen expression in these cells is stable over several days, although mRNA levels decline rapidly upon withdrawal of interferon. Vascular and stromal cell class II antigens are functional, in that they can be recognized by cytolytic and helper T cell clones. Several non-MHC antigens are also involved in the recognition of endothelial and stromal cells by T cells. We propose a model for the role of inducible class II molecules on endothelium and stromal cells in vivo: The induction of class II MHC antigens on endothelial cells, locally mediated by activated T cells, enables endothelium to present an immunogenic cell surface structure, comprised of antigen plus self class II polymorphic determinants, which in turn, serves to recruit additional antigen-specific T cells from the circulation into the site of a developing cell mediated immune response. Class II molecules on stromal cells, also induced locally at the site of a developing response, confers immune accessory function on these cells and may serve to augment and sustain a T cell response.

Viral replication in olfactory receptor neurons and entry into the olfactory bulb and brain.

This communication describes our ongoing studies of the interaction of the mouse host and vesicular stomatitis virus (VSV). When VSV is applied to the nasal neuroepithelium, it initially replicates in olfactory receptor neurons, and is transmitted along the olfactory nerve to the central nervous system (CNS) within 12 hours. In the olfactory bulb, the virus replicates invasively through the layers of the olfactory bulb, reaching the olfactory ventricle by day 4-5 post infection, and the hindbrain by day 8 post infection. In mice, infection may result in a 50% mortality rate. The crucial host innate and specific immune responses responsible for restricting viral propagation and caudal spread of the virus will be discussed. The efficacy of interleukin-12 (IL-12) treatment for enhanced viral clearance and promotion of host recovery are described along with the implications for treatment of human encephalitis. The hosts' response to infection is also regulated by the sex of the host, and the age at infection. The role of specific mucosal humoral immunity and systemic cellular immunity in prevention of infection are described.

Distribution of vesicular stomatitis virus proteins in the brains of BALB/c mice following intranasal inoculation: an immunohistochemical analysis.

Earlier studies have shown that intranasal instillation of vesicular stomatitis virus (VSV), a negative-sense RNA virus, in mice and rats can result in infection of the brain, hind-limb paralysis and death. Using an antiserum directed against VSV proteins, we sought to determine the potential neuronal and non-neuronal pathways VSV utilize, for central nervous system dissemination in BALB/c mice. Within 12 h following intranasal inoculation of VSV, VSV antigen could be detected in the olfactory nerve layer of the ipsilateral olfactory bulb. Within 3-4 days post-inoculation (p.i.), VSV had disseminated into the glomeruli of the olfactory bulb as well as the anterior olfactory nuclei that were ipsilateral to the VSV instillation. Within the glomeruli, VSV antigen was more prevalent in the granule cells than in the mitral cells. Correspondingly, the lateral olfactory tract, where axons of mitral cells course, remained VSV negative throughout 7 days p.i. By 7 days p.i., viral proteins were detected in several additional regions extending to the brainstem. These included regions involved in theta-rhythm generation during exploration and REM sleep, i.e. the septal nuclei, the supramammillary body, and the hippocampal formation, as well as the amygdaloid complex and brainstem neuromodulatory centers, such as the dorsal raphé and locus coeruleus. Structures abutting the ventricular surfaces, such as the dorsal cochlear nucleus, were also labeled. Tracts immunoreactive to VSV included the dorsal tegmental tract, fascia retroflexus, Probst tract, and mesencephalic tract of the trigeminal motor nerve. Besides the lateral olfactory tract, tracts that remained VSV negative included the anterior commissure, the corpus callosum and the mammillary peduncle. The pattern of VSV immunoreactivity supports the idea that following infection of the olfactory bulb glomeruli, VSV spreads via both ventricular surfaces and retrograde transport within axons of neuromodulatory transmitter systems innervating the olfactory bulb. Conversely, regions exhibiting low levels of VSV antigen are not likely to be involved in VSV dissemination. In particular, the paucity of VSV antigen in some of the terminal fields of neuromodulatory systems indicate that anterograde transport is more selective than retrograde transport. Surprisingly, the principal neurons of the olfactory glomeruli, thalamus, cerebral cortex and the hippocampus, all of which use L-glutamate as the excitatory neurotransmitter, are much less involved in viral dissemination.