Understanding them to understand ourselves: The importance of NHP research for translational neuroscience

Studying higher brain function presents fundamental scientific challenges but has great potential for impactful translation to the clinic, supporting the needs of many patients suffering from conditions that relate to neuronal dysfunction. For many key questions relevant to human neurological conditions and clinical interventions, non-human primates (NHPs) remain the only suitable model organism and the only effective way to study the relationship between brain structure and function with the knowledge and tools currently available. Here we present three exemplary studies of current research yielding important findings that are directly translational to human clinical patients but which would be impossible without NHP studies. Our first example shows how studies of the NHP prefrontal cortex are leading to clinically relevant advances and potential new treatments for human neuropsychiatric disorders such as depression and anxiety. Our second example looks at the relevance of NHP research to our understanding of visual pathways and the visual cortex, leading to visual prostheses that offer treatments for otherwise blind patients. Finally, we consider recent advances in treatments leading to improved recovery of movement and motor control in stroke patients, resulting from our improved understanding of brain stem parallel pathways involved in movement in NHPs. The case for using NHPs in neuroscience research, and the direct benefits to human patients, is strong but has rarely been set out directly. This paper reviews three very different areas of neuroscience research, expressly highlighting the unique insights offered to each by NHP studies and their direct applicability to human clinical conditions.

The continued need for animals to advance brain research

Policymakers aim to move toward animal-free alternatives for scientific research and have introduced very strict regulations for animal research. We argue that, for neuroscience research, until viable and translational alternatives become available and the value of these alternatives has been proven, the use of animals should not be compromised.

International primate neuroscience research regulation, public engagement and transparency opportunities

Scientific excellence is a necessity for progress in biomedical research. As research becomes ever more international, establishing international collaborations will be key to advancing our scientific knowledge. Understanding the similarities in standards applied by different nations to animal research, and where the differences might lie, is crucial. Cultural differences and societal values will also contribute to these similarities and differences between countries and continents. Our overview is not comprehensive for all species, but rather focuses on non-human primate (NHP) research, involving New World marmosets and Old World macaques, conducted in countries where NHPs are involved in neuroimaging research. Here, an overview of the ethics and regulations is provided to help assess welfare standards amongst primate research institutions. A comparative examination of these standards was conducted to provide a basis for establishing a common set of standards for animal welfare. These criteria may serve to develop international guidelines, which can be managed by an International Animal Welfare and Use Committee (IAWUC). Internationally, scientists have a moral responsibility to ensure excellent care and welfare of their animals, which in turn, influences the quality of their research. When working with animal models, maintaining a high quality of care ("culture of care") and welfare is essential. The transparent promotion of this level of care and welfare, along with the results of the research and its impact, may reduce public concerns associated with animal experiments in neuroscience research.

Communicating About Animal Research with the Public

Animals play a key role in biomedical research and other areas of scientific inquiry. But public opinion plays a key role in influencing how this area of science is regulated and funded. Nevertheless, scientists have historically been reticent to speak openly about their animal research or to open their animal facilities to the public in any way. Consequently, most of the available information has come from those opposed to animal research. This imbalance has led to suspicion and lagging public support for this work. To reverse this effect, efforts are now being made in many parts of the world to increase openness and transparency in this sector. The authors firmly believe that encouraging more institutions to join this movement, focused on better and greater communication, is essential to preserve the research community's "permission" to perform justifiable studies involving animals. For the purposes of this article, we consider "the public" to include that cross-section of society who may be asked their views in opinion poll studies and who may vote in elections. It also includes other influential groups such as the media, scientists working in other disciplines, animal welfare groups, and politicians who may shape regulatory frameworks. Public opinion on this issue matters. The majority of funding for biomedical research comes, either directly or indirectly, from the public purse. In the case of pharmaceutical research, funding derives from selling medicines to consumers. We therefore all have a vested interest in this funding. Furthermore, legislation that covers the use of animals in research is permissive-it allows scientists to do things that might otherwise contravene animal welfare laws. But this permission is normally contingent on complying with strict protective measures designed to ensure the work stays within the ethical framework that public opinion has deemed appropriate. Open and transparent communication is the best way to promote public understanding. There is thus a responsibility on all those involved in animal research, whether scientists, animal care staff, physicians, veterinarians, members of ethics committees, or managers and leaders, to support and promote public awareness and trust in this work. Circumstantial evidence shows that, with such open dialogue, there is decreased targeting and harassment of individuals and job pride and satisfaction for all involved is improved.

Accelerating the Evolution of Nonhuman Primate Neuroimaging

Nonhuman primate neuroimaging is on the cusp of a transformation, much in the same way its human counterpart was in 2010, when the Human Connectome Project was launched to accelerate progress. Inspired by an open data-sharing initiative, the global community recently met and, in this article, breaks through obstacles to define its ambitions.

A sensitive assay for detection and measurement of neutralising antibody to human immunodeficiency virus

An assay based on the inhibition of syncytium formation in C8166 cells was developed to measure low levels of neutralising antibody (NT-AB) to human immunodeficiency virus (HIV) and to detect cross-reactivity between virus strains. The relationship between virus challenge and antibody titre was represented by a tripartite curve which was essentially linear over moderate levels of virus input. Based on these findings, antibody titres were standardised against 100 TCID50 of challenge virus. However, lower virus inocula were found to detect minimum levels of antibody. Reproducibility of antibody titres between tests was high, with variation generally lying within one dilution step. The improved sensitivity of the technique allowed detection of NT-ABs in animals immunised with immune-stimulating complexes (ISCOMS) incorporating HIV antigens. Consistent levels of cross-reactivity between HIV strains was demonstrated, indicating the presence of distinct viral groups, from which dominant isolates may be chosen for use in vaccination studies.

Induction of virus-producing tumours in athymic nude mice by bovine papillomavirus type 4

Bovine papillomavirus type 4 (BPV-4), the causative agent of alimentary papillomatosis, has been used to infect, in vitro, fragments of palatine mucosa from late term bovine fetuses. These small explants were placed beneath the renal capsule of athymic nude mice where they grew to produce, at first, squamous epithelial cysts containing BPV-4 genomic DNA and, later, papillomas which were morphologically identical to those of cattle and which contained large amounts of replicating virus. The possible utility of this technique in assessing neutralising antibodies in vaccine development is discussed.

Feline oncornavirus-associated cell membrane antigen. IV. Antibody titers in cats with naturally occurring leukemia, lymphoma, and other diseases

Cats with naturally occurring leukemia and lymphoma had low or negative humoral antibody titers to the feline oncornavirus-associated cell membrane antigen (FOCMA). Geographic differences were seen in the relative frequencies of various forms of lymphoproliferative neoplasms. Lymphatic leukemia and thymic lymphoma were most common in Boston, whereas alimentary lymphoma was most frequent in Glasgow. No significant differences were found in geometric mean FOCMA antibody titers for the various forms of leukemia-lymphoma or for feline leukemia virus (FeLV)-positive as compared to FeLV-negative cats. Approximately 70% of 76 Boston cats with nonregenerative anemias were FeLV gs antigen (gsa) positive; this was similar to the percentage with leukemia-lymphoma from the same population that was positive. Fifty-five to 62% of the Boston cats with other infectious diseases, such as peritonitis and septicemia, were gsa positive. We postulate that this is due to a predisposition to infectious diseases by the immunosuppressive action of FeLV. Young cats from the Boston population that developed lymphoma, infectious peritonitis, and certain other diseases were more likely to be FeLV gsa positive than older cats with the same diseases.

Vaccination against feline leukaemia virus using a cell membrane antigen system

Cats inoculated with live feline lymphoblastoid cells of the FL74 line developed high titres of antibody to feline oncornavirus-associated cell membrane antigen (FOCMA). Eight cats were subsequently challenged with a large dose of feline leukaemia virus (FeLV) of a highly pathogenic strain. All resisted infection while 10 cats given the challenge virus alone became infected. The FeLV produced by FL74 cells was shown to be of extremely low infectivity in cats and in cultured feline cells. Cats inoculated with either FL74 cells or virus purified from them did not become infected. The purified virus did not induce FOCMA antibody in cats not previously exposed to FeLV. The fact that FL74 cells are highly immunogenic, but produce virus of low infectivity, is of value in devising vaccines against FeLV. Cats were also inoculated with FL74 cells which had been inactivated with paraformaldehyde. They developed FOCMA antibody, reaching a peak titre of 256, and no virus could be cultured either from the vaccine preparations or from the tissues of the cats.

B and T cells in a cat with thymic lymphosarcoma

The mixed antiglobulin reaction and the formation of nonimmune rosettes with guinea-pig red blood cells (RBC) distinguished feline B and T cells, respectively. In a cat with thymic lymphosarcoma, the cells reacting in these tests formed separate, nonoverlapping populations. The malignant cells were large lymphoblasts replacing the normal thymus and infiltrating local lymph nodes, where they localized only in the paracortical, i.e., thymus-dependent areas. Cells from the nodes could therefore be identified as malignant or normal by their size. The mixed antiglobulin reaction showed that the malignant cells did not carry the surface Ig characteristic of B cells, whereas these malignant cells formed nonimmune rosettes with guinea-pig RBC. Among lymph node cells, most surviving normal and small lymphocytes, from outside the thymus-dependent areas, reacted as B cells. The morphologic evidence therefore corroborated the test results, which indicated that the formation of rosettes with guinea-pig RBC seems a reliable means for the demonstration of T cells in the cat.

Epidemiological studies on feline leukaemia virus infection. I. A serological survey in urban cats

A survey of the incidence of feline leukaemia virus (FeLV) infection in cats in a large urban area was made by studying the prevalence of antibodies to feline leukaemia virus-associated cell membrane antigens. Two serological tests were used, immunofluorescence and a mixed immunoglobulin rosette technique. The overall incidence of cats with antibodies was 40%, contrasting with 6% in the surrounding rural area. Only 6% of urban kittens were positive while 50% of adults had antibodies. The incidence in adults rose from 29% at 5-6 months to 74% in cats over 3 years. Stray cats had an incidence twice as high as that of domestic pets. These results support and extend earlier findings that FeLV infection is common and is horizontally transmitted.

Odontogenic myxofibroma: report of two cases

We have reported the occurrence of two odontogenic mesenchymal tumors of the jaws. Though both cases had an associated impacted tooth, neither had foci of epithelial growth. Results of clinical, radiographic, and histopathological analysis in both cases were consistent with the diagnosis of a fibroma with myxomatous degeneration and thus, the diagnosis was myxofibroma.

A mixed-immunoglobulin rosette technique for detection of antibody to feline oncornavirus-associated cell membrane antigen

A mixed-immunoglobulin rosette technique has been developed for the detection of antibodies to feline oncornavirus-associated cell membrane antigens. Lymphoblastoid cells infected with feline leukemia virus were incubated with test sera and then fixed in paraformaldehyde. They were then exposed to a rabbit anti-cat immunoglobulin G serum. Antigen-antibody reactions were detected by mixing the cells with sheep erythrocytes sensitized with cat anti-sheep red blood cell serum; the presence of cat antibody on the lymphoid cells was registered by the formation of sheep red blood cell rosettes around them. The method was shown to be at least 10 times more sensitive than indirect immunofluorescence. A high degree of correlation was shown between the mixed-immunoglobulin rosette and indirect immunofluorescence tests, using both feline leukemia virus-infected cat and dog cells as targets. The results indicate that the tests are likely to be measuring similar reactions. Using the indirect immunofluorescence test we found that 75% of cats with lymphoid neoplasia had no demonstrable antibodies. Twenty-four of such indirect immunofluorescence-negative sera were tested by the mixed-immunoglobulin rosette technique; antibody was shown in at least seven of these sera.

Feline oncornavirus-associated cell membrane antigen. II. Antibody titers in healthy cats from household and laboratory colony environments

Antibody titers to the feline oncornavirusassociated cell membrane antigen (FOCMA) were determined for 447 healthy cats from laboratory colony and household environments. Only 2.7 percent of 221 cats from colony environments were antibody positive as compared to 50.4 percent of 256 cats from household environments. Incidence of FOCMA antibody and geometric mean antibody titer for pet cats from New York City representing single cat apartment habitats were substantially lower than values for unscreened cats from the Boston, Glasgow, and Detroit suburban environments. Geometric mean antibody titer for young adults in the Boston population was significantly higher than titers for kittens or aged cats. This may be due to greater mobility resulting in increased exposure to other cats. In contrast to the high frequency of FOCMA antibody positivity in pet-cat populations, less than 2 percent of the same groups were positive for virus group-specific antigen in peripheral blood leukocytes and platelets. This was interpreted as an indication that many more cats became infected with feline leukemia virus under natural conditions that the number developing persistent virus infection and/or clinical leukemia.

Anemia associated with feline leukemia virus infection in cats

The types of anemia associated with natural and experimental feline leukemia virus (FeLV) infection in cats were investigated. In one experiment, 10 kittens were inoculated neonatally with Jarrett FeLV-1, an isolate of subgroup A; 6 developed anemia a few weeks later. This anemia was characterized by macrocytosis, normoblastosis, increased erythropoiesis in the bone marrow, and extramedullary hematopoiesis in the spleen. Anemia was transient and nonfatal and occurred before the onset of lympoid malignancy. The same type of anemia was also seen in 9 of 24 kittens inoculated with Jarrett FeLV-9 of subgroups A and B. A different form of anemai occurred in another experiment in which 10 kittens were inoculated with FeLV-C of subgroup C only. All 10 kittens developed a profound aplastic or erythroblastopenic anemia in which the bone marrow became depleted of erythroid tissue; all kittens died within 16 weeks, most as a direct result of anemia. In an experiment in which kittens were inoculated with FeLV-B of subgroup B only, no kitten showed anemia. Cats with naturally acquired, nonleukemic lymphosarcoma were also studied. Of 33 lymphosarcomas in which myelophthisis was excluded as a cause, 54% of the affected cats had anemia, the features of which were consistent with hemolytic origin. When virus could be grown from these lymphosarcomas, it was of subgroup A alone or a combination of A and B. With one exception, anemic cats had low or negative titers to feline oncornavirus-associated cell membrane antigens. Until more isolates have been tested, it is not known if the various hematologic changes reflected differences in the pathogenic effects of the subgroups of the virus or of types of strains within them.

Feline leukemia

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