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At least 19 recordsLinked to original sources

PubMed1975

Spontaneous Herpesvirus saimiri lymphoma in owl monkeys.

Three examples of spontaneous malignant lymphoma were observed in owl monkeys 23, 81, and 183 days after arrival in our laboratories. The pathological features of the disease were analogous to experimentally induced Herpesvirus saimiri lymphoma. H. saimiri was recovered from 2 animals (it was not attempted from one case) and one isolate was shown to reproduce characteristic H. saimiri malignant lymphoma. Each monkey originated in Peru in contrast to our usual source of owl monkeys which originate in Barranquilla, Colombia. Samples collected from owl monkeys in Peru did not reveal antibodies to H. saimiri nor were virus isolated from cocultured leukocytes. Squirrel monkeys in the same geographical location all carried H. saimiri. The observations indicate that H. saimiri lymphoma can occur as a spontaneous disease and that the virus can cross the same taxonomic lines in nature as in the laboratory.

Animals↗

PubMed1976

Studies of cultured lymphocytes of the owl monkey (Aotus trivirgatus) infected with Herpesvirus saimiri.

The lymphocytes of five owl monkeys (Aotus trivirgatus) infected with Herpesvirus saimiri and three control monkeys were studied. Lymphocytes were separated on Ficoll-Hypaque gradients, incubated in suspension cultures, and prepared for electron microscopic and immunofluorescent study at 24, 48, and 72 hours after the beginning of culture. Buffy coats of whole blood obtained immediately after bleeding were also prepared for study. At the time of the study, four of the five infected monkeys had died with malignant lymphoma and lymphocytic leukemia. Herpesvirus saimiri virions were demonstrated by electron microscopy and H saimiri antigens by immunofluorescence in 1-20% of the lymphocytes from infected monkey in two of five cultures at 24 hours after culture, four of five at 48 hours after culture, and all of five at 72 hours after culture. There was good agreement between the electron microscopic and the immunofluorescent data. None of the control monkey cultures and none of the buffy coat preparations contained H saimiri virions or antigens. By electron microscopy, the great majority of the virus particles were nucleocapsids within the nuclei of lymphocytes. Enveloped virions were seldom observed. There was some evidence to suggest that the higher the percentage of lymphocyte containing H saimiri, the poorer the prognosis for the monkey. Herpesvirus saimiri was isolated from all five infected monkeys by co-cultivation of lymphocytes with Vero cells. Control lymphocyte co-cultivations were negative.

Animals↗

PubMed1975

Experimental horizontal transmission of Herpesvirus saimiri from squirrel monkeys to an owl monkey.

Herpesvirus saimiri was naturally transmitted from squirrel monkeys excreting the virus to one of two owl monkeys housed in the same cage. The owl monkey became infected approximately three months after contact was initiated. H. saimiri was consistently isolated from the peripheral lymphocytes until this animal died eight months later. During this period the owl monkey developed specific antibody to H. saimiri to a maximal neutralization index of 5.5 logs. The other monkey remained uninfected for an ovservation period of one year. The documentation of this horizontal transmission of H. saimiri infection from squirrel monkeys to an owl monkey suggests that owl monkeys developing spontaneous malignant lymphomas associated with H. saimiri infection may also have acquired the infection in this manner.

Animals↗

PubMed1992

Mechanisms of protective immunity against asexual blood stages of Plasmodium falciparum in the experimental host Saimiri.

In the Saimiri monkey, an experimental host for human malaria, acquired protection against Plasmodium falciparum blood stages depends on the IgG antibody populations developed. In vivo protective anti-falciparum activity of IgG antibodies is correlated with the in vitro opsonizing activity promoting phagocytosis of parasitized red blood cells. In contrast, non protective antibodies inhibit this mechanism by competing at the target level. A similar phenomenon can be observed in human infection. Anti-cytoadherent and anti-rosette antibodies developed by Saimiri and humans prevent the development of physiopathological events like cerebral malaria which can also occur in this experimental host. Furthermore, transfer to protective human anti-falciparum IgG antibodies into infected Saimiri monkeys exerts an anti parasite activity as efficient as that observed when it is transferred into acute falciparum malaria patients, making the Saimiri an even more attractive host. Studies on the role of immunocompetent cells in the protective immune response are still in their infancy, however the existence of a restricted polymorphism of MHC II class molecules in the Saimiri confers additional theoretical and practical importance to this model.

Animals↗

PubMed1992

Platelet kinetics and other hematological profiles in experimental Plasmodium falciparum infection: a comparative study between Saimiri and Aotus monkeys.

Levels of platelets and other hematological values were monitored in 21 Saimiri and 12 Aotus monkeys over a period of three weeks post-infection with monkey-adapted Indochina CDC-1 strain of Plasmodium falciparum. In both Saimiri sciureus boliviensis and Aotus nancymai karyotype-1 monkeys the severest thrombocytopenia was observed at 14 days post-infection coinciding with peak parasitemia, neutropenia, lymphocytosis, and anemia associated with severe hemoglobinemia and elevated fibrinogen degeneration products(FDP's). MCH and MCV profiles in Aotus monkeys decreased with ascending parasitemia. In contrast, these parameters in Saimiri were characterized by a significant compensatory increase correlating with parasitemia. In general, thrombocytopenia was one of the earliest clinical manifestations of the infection with the platelets returning to normal levels shortly after peak parasitemia at 14 days. Platelet kinetics had a strong correlation with hematologic and parasitologic values in the Aotus model. No consistent associations were observed between platelet kinetics and other parameters in the Saimiri model. These data indicate that the Aotus model for malaria is more predictable than the Saimiri. Further, platelet turnover rates and recovery provide a useful prognostic parameter during malaria infection. The results are discussed in relation to the value of the two species of monkeys as models for the pathogenesis of human malaria.

Animals↗

PubMed1977

Episomal viral DNA in a Herpesvirus saimiri-transformed lymphoid cell line.

The lymphoid cell line #1670 has been derived from the infiltrated spleen of a tumor-bearing marmoset monkey infected with Herpesvirus saimiri. The cells contain both types of H. saimiri DNA, unique light (L-) DNA (36% cytosine plus guanine) and repetitive heavy (H-) DNA (71% cytosine plus guanine), without producing infectious virus. Viral DNA was found to persist in these cells as nonintegrated circular DNA molecules. Closed circular superhelical viral DNA molecules were isolated by three subsequent centrifugation steps: (i) isopycnic centrifugation in CsCl, (ii) sedimentation through glycerol gradients, and (iii) equilibrium centrifugation in CsCl-ethidium bromide. The isolated circles had a molecular weight of 131.5 +/- 3.6 x 10(6). This is significantly higher than the molecular weight of linear DNA molecules isolated from purified H. saimiri virions (about 100 x 10(6)). Partial denaturation mapping of circular molecules from #1670 lymphoid cells showed uniform arrangement of H- and L-DNA sequences in all circles. All denatured molecules contained two L-DNA regions (molecular weights of 54.0 +/- 1.8 x 10(6) and 31.5 +/- 1.3 x 10(6)) and two H-DNA regions (molecular weight of 25.6 +/- 1.9 x 10(6) and 20.0 +/- 0.8 x 10(6)) of constant length. Maps of both L-regions suggested that the sequences of the shorter L-DNA region were a subset of those of the longer region. The sequences of both L-regions had the same orientation. Circular molecules from H. saimiri-transformed lymphoid cell line #1670 appeared to represent defective genomes, containing only 75% of the genetic information present in L-DNA of H. saimiri virions.

Animals↗

PubMed1992

Primary structure of the herpesvirus saimiri genome.

This report describes the complete nucleotide sequence of the genome of herpesvirus saimiri, the prototype of gammaherpesvirus subgroup 2 (rhadinoviruses). The unique low-G + C-content DNA region has 112,930 bp with an average base composition of 34.5% G + C and is flanked by about 35 noncoding high-G + C-content DNA repeats of 1,444 bp (70.8% G + C) in tandem orientation. We identified 76 major open reading frames and a set of seven U-RNA genes for a total of 83 potential genes. The genes are closely arranged, with only a few regions of sizable noncoding sequences. For 60 of the predicted proteins, homologous sequences are found in other herpesviruses. Genes conserved between herpesvirus saimiri and Epstein-Barr virus (gammaherpesvirus subgroup 1) show that their genomes are generally collinear, although conserved gene blocks are separated by unique genes that appear to determine the particular phenotype of these viruses. Several deduced protein sequences of herpesvirus saimiri without counterparts in most of the other sequenced herpesviruses exhibited significant homology with cellular proteins of known function. These include thymidylate synthase, dihydrofolate reductase, complement control proteins, the cell surface antigen CD59, cyclins, and G protein-coupled receptors. Searching for functional protein motifs revealed that the virus may encode a cytosine-specific methylase and a tyrosine-specific protein kinase. Several herpesvirus saimiri genes are potential candidates to cooperate with the gene for saimiri transformation-associated protein of subgroup A (STP-A) in T-lymphocyte growth stimulation.

Amino Acid Sequence↗

PubMed1991

Identification of transforming genes of subgroup A and C strains of Herpesvirus saimiri.

Herpesvirus saimiri is an oncogenic herpesvirus that induces rapidly progressing lymphomas in New World primates. Using retrovirus vectors for gene transfer, specific open reading frames of H. saimiri were tested for their ability to transform rodent cells in culture. One open reading frame, designated STP-C488 (for saimiri-transformation-associated protein of the subgroup C strain 488), phenotypically transformed Rat-1 cells, resulting in formation of foci, growth at reduced serum concentration, and growth to higher cell densities. Cells transformed by STP-C488 formed invasive tumors in nude mice. The STP-A11 reading frame of strain 11 (subgroup A) was much less potent in its transforming ability than STP-C488. These results demonstrate the oncogene nature of these two open reading frames and provide a means for studying their transforming functions independent of the rest of the H. saimiri genome.

Animals↗

PubMed1991

Persistence of selectable herpesvirus saimiri in various human haematopoietic and epithelial cell lines.

Herpesvirus (h.) saimiri, an infectious agent of squirrel monkeys, is capable of persisting in T lymphocytes of various primate species. It has been used as a vector for the functional analysis of regulatory genes in primary human T lymphocytes. As it is not yet known whether other cell types are capable of supporting viral persistence, various human cell lines were investigated using selectable h. saimiri recombinants. The lines chosen represent cells from the epithelium and connective tissue as well as from all haematopoietic lineages, i.e. cells of B and T lymphoid origin as well as myeloid-, fibroblast- and carcinoma-derived cultures converted to Geneticin or hygromycin B resistance, and harbouring episomal DNA of the selectable recombinants. The Burkitt's lymphoma-derived cell line Raji also contained simultaneously persisting episomes of the Epstein-Barr virus. Most of the cell cultures except a pancreatic carcinoma line and foreskin fibroblasts did not produce infectious virus. These observations show that a herpesvirus genome can persist episomally in a broad range of cultured cell types. The variety of infectable cell types and species suggests the presence of a widely distributed and well conserved virus receptor for h. saimiri. Thus the h. saimiri genome could be applied more generally as a vector.

Blotting, Northern↗

PubMed1978

Herpesvirus ateles DNA and its homology with Herpesvirus saimiri nucleic acid.

Analysis of the structural organization of Herpesvirus ateles DNA shows that two types of viral DNA molecules are encapsidated in virions: (i) M-genomes, which contain 74% light sequences (L-DNA, 38% guanine plus cytosine) and 26% highly repetitive heavy sequences (H-DNA, 75% guanine plus cytosine), and (ii) defective H-genomes, which consist exclusively of repetitive H-DNA. The structure of M-genomes from H. ateles consists of an L-DNA region of about 70 x 10(6) daltons inserted between H-DNA termini of variable length. M-genomes with a shorter H-DNA region at one end of the molecule have a long stretch of H-DNA at the other end, resulting in a total molecular weight of 89.8 +/- 8.5 x 10(6). Thus it resembles the structure of M-genomes of H. saimiri. H-DNA of the two independent H. ateles isolates, strains 810 and 73, reveals different patterns after cleavage with restriction endonuclease Sma I. H-DNA of H. ateles 810 appears to consist of identical tandem repeat units with a molecular weight of 1,035,000; the H-DNA repeat unit of strain 73 is shorter (930,000 molecular weight). Corresponding DNA sequences of the two H. ateles strains (810 and 73) are completely homologous in cross-hybridizations. However, a discrete nucleotide sequence divergence between these virus strains is detected by measuring melting temperatures (T(m)) of DNA hybrid molecules. Some homology exists between H. ateles and H. saimiri DNA. Hybridization of L-DNA from H. ateles with L-DNA from H. saimiri shows about a 35% homology between the respective L-DNA sequences; the resulting heteroduplex molecules show a decrease of T(m) by 13.5 degrees C, corresponding to about a 9% mismatching in cross-hybridizing parts of L-regions. Very little homology is found between H-DNA of H. ateles and H. saimiri.

Base Sequence↗

PubMed1975

Chemotherapy of Plasmodium vivax in Saimiri and Aotus models.

Three standard antimalarial compounds were tested against trophozoite or sporozoite induced infections of the Panamanian Achiote strain of Plasmodium vivax in two species of monkeys. In Saimiri sciureus (24 subjects) and Aotus trivirgatus (11 subjects), parasite clearance from the peripheral blood averaged 3 days after initiating chloroquine therapy (total dose of 25 mg base/kg body weight over 3 days or single dose of 10 mg base/kg. Trophozoite induced infections were cured in all of 10 Saimiri and all of 6 Aotus, as indicated by the absence of relapses. Relapses did occur in 3 of 11 tests with Saimiri and 3 of 5 tests with Aotus against sporozoite induced infections. Subpatent periods ranged from 38 to 111 days among intact and splenectomized hosts. This is the first chemotherapeutic evidence for the persistence of exoerythrocytic stages of P. vivax in New World monkeys. Pyrimethaminr (single dose of 1 mg/kg) cured trophozoite induced infections in all of five Saimiri hosts. Radical cure of sporozoite induced infections was accomplished in each of six trials with chloroquine (25 mg base/kg) plus primaquine (1 mg base/kg for 14 days). The primary attack or relapse was treated. These models warrant further investigation in chemotherapy.

Administration, Oral↗

PubMed1975

Comparative studies of social behavior in Callicebus and Saimiri: strength and specificity of attraction between male-female cagemates.

The strength and specificity of attraction between male and female cagemates was compared in Saimiri and Callicebus, using paired-comparison and single-stimulus methods of testing. Results from both methods showed that the attraction to the cagemate was stronger and more specific in Callicebus than in Saimiri. Sex differences were more pronounced in Saimiri than in Callicebus. Squirrel monkey females were more strongly attracted to strangers than were males and they clearly preferred female strangers over male strangers or their male cagemates.

Animals↗

PubMed1979

Methylation of Herpesvirus saimiri DNA in lymphoid tumor cell lines.

Several continuous lymphoid cell lines have been established from tumors induced by Herpesvirus saimiri. At least a portion of the viral DNA in the marmoset lymphoid cell line 1670, which does not produce detectable virus, is present as covalently closed circular episomal DNA. The use of restriction endonuclease digestion, transfer to nitrocellulose filters, and hybridization of the virus-specific DNA has produced strong evidence that viral DNA sequences present in total 1670 cell DNA and in isolated episomes are extensively methylated. The restriction endonuclease Hpa II has the same recognition sequence as Msp I but, unlike Msp I, fails to cleave when the C of the C-G dinucleotide is methylated. Viral DNA sequences of 1670 cells are refractory to cleavage by Hpa II but not Msp I; greater than 80% of the Hpa II cleavage sites appear to be methylated. Similarly, viral DNA sequences of 1670 cells are refractory to cleavage by Sma I (C-C-C-G-G-G) and Sac II (C-C-G-C-G-G) but not Sac I, Pvu II, or Pst I, which lack the dinucleotide C-G in their recognition sequences. Methylation of mammalian DNA has been previously found exclusively at C residues in the dinucleotide C-G. H. saimiri DNA sequences of another nonproducer cell line, 70N2, also appeared to be extensively methylated, but analysis of total cell DNA extracted from three virus-producing lymphoid lines revealed no evidence of methylation of viral DNA sequences. It remains to be seen if methylation of viral DNA plays a role in the lack of complete expression of H. saimiri genome information in nonproducing lymphoid cell lines.

Animals↗

PubMed1975

Clinicopathologic characterization of Herpesvirus saimiri malignant lymphoma in New Zealand white rabbits.

Twenty-two of 39 rabbits inoculated with Herpesvirus saimiri developed malignant lymphoma and either died or were killed between 17 and 165 days after inoculation. No clinical signs were present in animals developing the disease before 46 days, but all other rabbits had a severe conjunctivitis, nasal discharge, and dyspnea resulting from a lymphocytic invasion of the ocular and nasal tissues. Four rabbits developed terminal leukemia. Pathologically, the disease resembled H. saimiri malignant lymphoma in nonhuman primates; there was extensive diffuse infiltration of most organs and tissues with either a lymphocytic or lymphoblastic infiltrate. Tumor nodules or masses seen in some forms of malignant lymphoma were not present. In contrast to nonhuman primates, all affected rabbits showed invasion of the skin of the nose and eyelids, conjunctiva, iris, ciliary body, and choroid. In 3 rabbits there was slight infiltration into the brain, not noted in nonhuman primates. The susceptibility of rabbits extended the host range of H. saimiri beyond the order Primates.

Animals↗

PubMed1976

Preventive vaccination against Herpesvirus saimiri-induced neoplasia.

In this paper we discuss the use of Herpesvirus saimiri as a model for the development of vaccines against herpesvirus-induced neoplasia in primates. Attempts at protection against the oncogenicity of H. saimiri have centered on the inactivation of virus by heat and formalin, the production of temperature-sensitive H. saimiri mutants, and the attenuation of the virus. Each of these approaches has provided information of use in the development of vaccines that may possibly be used in man.

Animals↗

PubMed1977

Inhibition of Herpesvirus saimiri replication by phosphonoacetic acid, benzo(a)pyrene, and methylcholanthrene.

The present investigations were undertaken to determine the possible effects of two carcinogenic polycyclic aromatic hydrocarbons, benzo(a)pyrene and 3-methylcholanthrene on Herpesvirus saimiri replication. The results from these experiments were compared with the effects of phosphonoacetic acid on the virus replication cycle. Phosphonoacetic acid inhibited the synthesis of virus-induced intracellular late antigens, membrane antigens and infectious virus but not the synthesis of the early antigens induced by H. saimiri. In contrast, benzo(a)pyrene and 3-methylcholanthrene inhibited primarily membrane antigen expression and infectious virus production. Benzo(a)pyrene was the most effective of the two compounds, with significant inhibition occurring with 2 mug/ml, whereas a minimum concentration of 10 mug/ml was required with 3-methylcholanthrene. Both compounds were most effective when present continuously during the 4-day infection process. However, exposure of infected cultures to a 3-hr pulse with each chemical also inhibited membrane antigen expression. Furthermore, pretreatment of cells for 48 hr before virus infection resulted in the inhibition of membrane antigen expression but not that of early or late antigens. These result demonstrate that some carcinogenic chemicals are capable of altering the H. saimiri replication cycle, primarily by inhibiting some but not all late events.

Acetates↗

PubMed1991

Ultrastructure of erythrocytes from Aotus trivirgatus and Saimiri sciureus monkeys infected by Plasmodium vivax.

Erythrocytes from Aotus and Saimiri monkeys parasitized by Plasmodium vivax show dramatic changes starting during the early stages of parasite development. Invaginations of the erythrocyte membrane, caveolae, are found during all parasite development stages. Up to six vesicles can be fused with one caveola, forming a caveola-vesicle complex. As the parasite grows, large accumulations of these vesicles can be seen within the erythrocyte cytoplasm. In addition to these caveolae-vesicle complexes, knob-like structures appear on the erythrocyte surface that are similar to those seen on the host-cell surface of P. falciparum-infected red cells. Extensive membrane-bound clefts spread throughout the erythrocytic cytoplasm, sometimes forming stacks or large whorls. The density of the red cell cytoplasm begins to decrease at an early stage of parasite development. All of these changes may be responsible for an increased fragility of the P. vivax-infected red cell from Aotus or Saimiri monkeys. Moreover, the large amount of parasite material that is released during rupture of the red cell may account for the high fever paroxysms that are characteristic of P. vivax malaria infection.

Animals↗

PubMed1991

Evidence of an x zone in lobule V of the squirrel monkey (Saimiri sciureus) cerebellum: the distribution of corticonuclear fibers.

The distribution of corticonuclear fibers to medial-most parts of the posterior interposed nucleus (NIP) from lateral areas of the vermis was studied in the squirrel monkey (Saimiri sciureus), using a silver impregnation method. The origin and course of degenerated fibers were studied in serial sections. The distribution pattern of corticonuclear fibers from a series of small well localized lesions placed in the vermis and paravermal cortex of lobule V is compatible with the interpretation that an x zone is present in Saimiri. A comparison of the positions of lesions and the trajectory of fibers arising therein suggests that corticonuclear input to medial-most parts of the NIP originated from a narrow cortical area (about 0.5-0.7 mm wide) located between a cortical area projecting into the medial cerebellar nucleus (the A zone) and a laterally adjacent area (the B zone) which related to the lateral vestibular nucleus. This NIP-projecting cortical area, located about 1.7 mm to 2.5 mm off the midline in lobule V, is interpreted as the x zone in this primate; it extends from lobule IV into lobule VI in squirrel monkey. Corticonuclear fibers of zone x in this primate form a comparatively small terminal field in the medial-most portions of NIP. This contrasts with the distribution of corticonuclear fibers of the C2 zone which consistently distribute to terminal fields that are shifted into more central areas of NIP. There appears to be no overlap of the corticonuclear terminal fields in the NIP for zone x versus the C2 zone. These results were correlated with data from the literature on the distribution of olivocerebellar fibers to the x zone and the C2 zone and the arrangement of cerebellar nucleoolivary projections into the inferior olive from the NIP. The x zone and the C2 zone both receive input from the contralateral medial accessory olive (MAO), both zones project into the NIP, and the NIP projects into those regions of the MAO which, in turn, project to these respective cortical zones and into the NIP. This suggest that the x zone is a component of the NIP-MAO circuit. Furthermore the proposed function of the x zone would support the view that this sagittal strip may have a more extensive rostrocaudal distribution in primates as compared to the cat.

Animals↗