Leishmania donovani: cellular and humoral immune responses after primary and challenge infections in squirrel monkeys, Saimiri sciureus

Cellular and humoral immune responses were studied in squirrel monkeys after primary and challenge infection with a Khartoum strain (WR 378) of Leishmania donovani. Each of 7 squirrel monkeys, Saimiri sciureus, was inoculated intravenously with 5 X 10(7) amastigotes/kg body weight, and one other monkey (control) was inoculated with uninfected hamster spleen homogenate. Five infected monkeys recovered from visceral leishmaniasis and two infected monkeys died. Three of the five squirrel monkeys which recovered from the primary infection demonstrated acquired resistance when challenged with an intravenous inoculation of 1.0 X 10(8) amastigotes of L. donovani/kg of body weight. Each of these same three monkeys, the two remaining monkeys which recovered from the primary infection and an uninfected control monkey, were challenged subsequently with an intradermal injection of 2.2 X 10(7) promastigotes of L. braziliensis panamensis (WR539) and developed cutaneous lesions. The reactivity of peripheral blood leukocytes from infected squirrel monkeys to phytohemagglutinin was depressed 2 to 10 weeks after infection, and the reactivity to concanavalin A was not affected. Data on responses to pokeweed mitogen were inconclusive. Reactivity to leishmanial antigens was detected at 12 weeks after infection, which coincided with a marked decrease or disappearance of parasites in liver imprints. Two of five surviving squirrel monkeys developed weak delayed skin test responses to leishmanin antigens after 23 weeks; the three remaining monkeys were anergic during the primary infection but developed strong delayed skin test responses to leishmanin antigens at 7 weeks after a challenge with L. donovani. All squirrel monkeys inoculated with L. donovani developed a hyperproteinemia, hypergammaglobulinemia, hypoalbuminemia, and a reversal of the albumin/globulin ratio between 4 to 18 weeks after infection. Plasma IgM and IgG levels were increased between 2 to 18 weeks after infection; much of this increase was due to IgG. Class-specific antileishmanial antibodies, with generally low IgM and high IgG titers, reached a maximum after 14 and 16 weeks, respectively. A correlation was observed between concentration of gamma-globulins and plasma IgM and IgG levels, but not gamma-globulin concentrations and maximum titers of class-specific antileishmanial antibodies. Squirrel monkeys challenged with L. donovani again developed hyperproteinemia, hypergammaglobulinemia, and increased concentrations of plasma IgM and IgG which correlated with high titers of IgG class-specific antileishmanial antibody 4 weeks after reinoculation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Experimental American leishmaniasis and Chagas'' disease in the Brazilian squirrel monkey: cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi

, and 1988. Experimental American leishmaniasis and Chagas' disease in the Brazilian squirrel monkey: cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi. International Journal for Parasitology 18: 1053–1059. Adult, laboratory-bred squirrel monkeys (Saimiri sciureus) previously infected with either Leishmania braziliensis braziliensis or L. b. panamensis were challenge infected with blood-form trypomastigotes of Trypanosoma cruzi (Brazil strain). Monkeys previously infected with T. cruzi were challenged with stationary phase promastigote forms of L. b. braziliensis. Monkeys were examined during the course of challenge for evidence of infection, electrocardiographic alterations and parasite-specific antibody responses. T. cruzi epimastigotes were cultured from the blood of monkeys up to 3 months after challenge with this parasite. Unulcerated cutaneous lesions appeared and persisted in monkeys challenged with L. b. braziliensis. The formation of satellite lesions was observed in one monkey. Increased QRS intervals were not observed in T. cruzi challenged monkeys without prior cardiac irregularities and QRS left axis shifts were observed in only two of these monkeys. Elevated titers of parasite binding IgM and IgG specific for both T. cruzi and L. braziliensis were observed in all monkeys following challenge. These results indicate that prior infection with T. cruzi or L. braziliensis does not protect against heterologous challenge infection with these organisms. However, prior infection with Leishmania parasites may provide some protection against chagasic cardiopathies.     

Genetically determined antigens of squirrel monkey (Saimiri sciureus) IgG

Alloantigens of squirrel monkey (Saimiri sciureus) IgG were studied using alloantisera prepared by cross-immunizations among four subspecies. The results demonstrated the occurrence of IgG antigenic polymorphism. Three distinct Fd fragment allotypes were detected. Greater alloantigenic complexity occurred among Colombian and Peruvian squirrel monkeys, which occupy the more central regions of the geographic range; Bolivian and Guyanan monkeys, which occupy the extremes of the range, expressed less alloantigenic complexity.     

Fasting hyperbilirubinemia in normal squirrel monkeys.

The plasma of Bolivian squirrel monkeys, unlike that of Brazilian squirrel monkeys, is markedly yellow due to unconjugated hyperbilirubinemia after an overnight fast. The fasting hyperbilirubinemia in Bolivian squirrel monkeys is likely due to two mechanisms. First, a twofold increase in the bilirubin turnover/production rate occurs during a 24-hour fast. A second mechanism is the decreased hepatic conjugation potential for bilirubin due to the presence of a higher bilirubin UDP-glucuronosyltransferase UDPGAKm and a lower Vm; this results in higher steady-state plasma and hepatic bilirubin levels during a fast when hepatic UDP-glucuronic acid levels are low. The Bolivian squirrel monkey provides an excellent animal model for human Gilbert's syndrome type I in which to study rate-limiting mechanisms in the movement of bilirubin from plasma to bile.     

Cortisol metabolism in the Bolivian squirrel monkey (Saimiri boliviensis boliviensis)

New World squirrel monkeys (Saimiri spp.) have high circulating cortisol levels but normal electrolytes and blood pressures. The goal of the present study was to gain insight into adaptive mechanisms used by Bolivian squirrel monkeys to minimize the effects of high cortisol on mineralocorticoid receptor (MR) activity and electrolyte and water balance. Aldosterone levels in serum from 10 squirrel monkeys were 17.7 +/- 3.4 ng/dl (normal range in humans, 4 to 31 ng/dl), suggesting that squirrel monkeys do not exhibit a compensatory increase in aldosterone. The squirrel monkey MR was cloned and expressed in COS-7 cells and found to have similar responsiveness to cortisol and aldosterone as human MR, suggesting that squirrel monkey MR is not inherently less responsive to cortisol. To determine whether altered metabolism of cortisol might contribute to MR protection in squirrel monkeys, serum and urinary cortisol and cortisone were measured, and a comprehensive urinary corticosteroid metabolite profile was performed in samples from anesthetized and awake squirrel monkeys. The levels of cortisone exceeded those of cortisol in serum and urine, suggesting increased peripheral 11beta-hydroxysteroid dehydrogenase 2 activity in squirrel monkeys. In addition, a significant fraction (approximately 20%) of total corticosteroids excreted in the urine of squirrel monkeys appeared as 6beta-hydroxycortisol, compared with that in man (1%). Therefore, changes in cortisol metabolism likely contribute to adaptive mechanisms used by Bolivian squirrel monkeys to minimize effects of high cortisol.     

Increased production of 11beta-hydroxysteroid dehydrogenase type 2 in the kidney microsomes of squirrel monkeys (Saimiri spp.)

In squirrel monkeys (Saimiri spp.), cortisol circulates at levels much higher than those seen in man and other Old World primates, but squirrel monkeys exhibit no physiologic signs of the mineralocorticoid effects of cortisol. These observations suggest that squirrel monkeys have mechanisms for protection of the mineralocorticoid receptor (MR) from these high levels of cortisol. We previously showed that the serum cortisol to cortisone ratio in these animals is low relative to that in human serum, suggesting that production of the MR protective enzyme, 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), is increased in squirrel monkeys. Here, we directly evaluate whether increased production of 11beta-HSD2, which inactivates cortisol to cortisone, is a mechanism for protection of MR. In vitro assays showed that 11beta-HSD2 activity in squirrel monkey kidney microsomes was 3 to 7 times higher than that seen in kidney microsomes from pig or rabbit. 11beta-HSD2 protein detected by Western blot analysis was 4 to 9 times greater in squirrel monkey microsomes than in pig or rabbit microsomes. Comparison of the effect of expression of either human or squirrel monkey 11beta-HSD2 on MR transactivation activity showed similar inhibition of MR response to cortisol by both enzymes, indicating that the intrinsic activities of the human and squirrel monkey enzymes are similar. These findings suggest that one mechanism by which squirrel monkeys protect the MR from activation by high cortisol levels in the kidney is by upregulation of 11beta-HSD2 activity through increased production of the enzyme.     

Insect-catching behavior in socially inexperienced infant squirrel monkeys

Insects are an essential component of squirrel monkey natural food. Eight of ten socially inexperienced infant squirrel monkeys, during their 2nd and 3rd month of age, directed their attention to living insects or film presentations of moving insects. They attempted to catch them with gradually improving success, and on at least two occasions consumed them. For comparison, group-living squirrel monkeys begin to eat solid food around their 2nd month of age, continuing with some nursing until about 11 or 13 months, and were only at this age seen to successfully catch and eat insects. Thus, as infant squirrel monkeys proved to be able to catch and eat insects before their first experience with conspecifics, an innate basis for this behavior can be assumed.     

The origin of four squirrel monkey cell lines established by karyotype analysis

The squirrel monkey is a neotropical primate genus which is widely used in biomedical research but includes individual species and subspecies that respond differently to experimental perturbations. GTG-banding patterns of chromosomes 15 and 16, which are distinct among different squirrel monkey species and subspecies, were used to determine the origin of three lung fibroblast cell lines from squirrel monkeys of unknown genetic background (DPSO 114/74, SqMkLu/68, and 7603830) and to confirm the origin of a lymphoblast cell line (GSML) recently established from Guyanese squirrel monkey. DPSO 114/74 cells are from Peruvian squirrel monkey, SqMkLu/68 cells are Bolivian squirrel monkey, and 7603830 cells are from a Peruvian/Bolivian hybrid. Chromosome analysis of GSML cells confirmed that they are from Guyanese squirrel monkey.     

Squirrel monkeys support replication of BK virus more efficiently than simian virus 40: an animal model for human BK virus infection

We performed experiments to test the suitability of squirrel monkeys (Saimiri sciureus) as an experimental model for BK virus (BKV) and simian virus 40 (SV40) infection. Four squirrel monkeys received intravenous inoculation with BKV Gardner strain, and six squirrel monkeys received intravenous inoculation with SV40 777 strain. Eight of 10 monkeys received immunosuppression therapy, namely, cyclophosphamide subcutaneously either before or both before and after viral inoculation. The presence of viral infection was assessed by quantitative real-time PCR amplification of viral DNA from blood, urine, and 10 tissues. We found that squirrel monkeys were susceptible to infection with BKV, with high viral copy number detected in blood and viral genome detected in all tissues examined. BKV genome was detected in urine from only one monkey, while three monkeys manifested focal interstitial nephritis. BKV T antigen was expressed in renal peritubular capillary endothelial cells. By contrast, SV40 was detected at very low copy numbers in only a few tissues and was not detected in blood. We conclude that the squirrel monkey is a suitable animal for studies of experimental BKV infection and may facilitate studies of viral entry, pathogenesis, and therapy.     

Herpesvirus saimiri strain variability

Herpesvirus saimiri was isolated from 22 squirrel monkeys by cocultivation of peripheral lymphocytes with permissive owl monkey kidney monolayer cells. Comparison of virion DNA fragments produced from restriction endonuclease digestion was used as a sensitive measure of strain variability. Although all isolates contained similarities and common features, 19 of the 22 were readily distinguished. Three of the isolates, however, were indistinguishable and possibly were related epidemiologically. Distinct subtypes of H. saimiri were not evident by these criteria; Peruvian, Colombian, Guyanan, and Bolivian squirrel monkeys yielded isolates without characteristic features peculiar to the geographic region. Three of three colony-born squirrel monkeys that were tested yielded a strain of virus distinct from that obtained from the mother. In separate experiments, two of three animals chosen at random yielded a strain of virus different from that originally obtained 16 and 22 months previously; only one of the three animals examined yielded the same strain of virus 22 months after the original isolation. The degree of restriction endonuclease fragment variability among H. saimiri strains appeared to be greater than previously observed for other herpesviruses.     

Pleistocene diversification of living squirrel monkeys (Saimiri spp.) inferred from complete mitochondrial genome sequences

In order to enhance our understanding of the evolutionary history of squirrel monkeys (Saimiri spp.), we newly sequenced and analyzed data from seven complete mitochondrial genomes representing six squirrel monkey taxa. While previous studies have lent insights into the taxonomy and phylogeny of the genus, phylogenetic relationships and divergence date estimates among major squirrel monkey clades remain unclear. Using maximum likelihood and Bayesian procedures, we inferred a highly resolved phylogenetic tree with strong support for a sister relationship between Saimiri boliviensis and all other Saimiri, for monophyly of Saimiri oerstedii and Saimiri sciureus sciureus, and for Saimiri sciureus macrodon as the sister lineage to the S. oerstedii/S. s. sciureus clade. We inferred that crown lineages for extant squirrel monkeys diverged around 1.5 million years ago (MYA) in the Pleistocene Epoch, with other major clades diverging between 0.9 and 1.1 MYA. Our results suggest a relatively recent timeline of squirrel monkey evolution and challenge previous conceptions about the diversification of the genus and its expansion into Central America.     

Androgen resistance in squirrel monkeys (Saimiri spp.)

The goal of this study was to understand the basis for high androgen levels in squirrel monkeys (Saimiri spp.). Mass spectrometry was used to analyze serum testosterone, androstenedione, and dihydrotestosterone of male squirrel monkeys during the nonbreeding (n = 7) and breeding (n = 10) seasons. All hormone levels were elevated compared with those of humans, even during the nonbreeding season; the highest levels occurred during the breeding season. The ratio of testosterone to dihydrotestosterone in squirrel monkeys is high during the breeding season compared to man. Squirrel monkeys may have high testosterone to compensate for inefficient metabolism to dihydrotestosterone. We also investigated whether squirrel monkeys have high androgens to compensate for low-activity androgen receptors (AR). The response to dihydrotestosterone in squirrel monkey cells transfected with AR and AR-responsive reporter plasmids was 4-fold, compared with 28-fold in human cells. This result was not due to overexpression of cellular FKBP51, which causes glucocorticoid and progestin resistance in squirrel monkeys, because overexpression of FKBP51 had no effect on dihydrotestosterone-stimulated reporter activity in a human fibroblast cell line. To test whether the inherently low levels of FKBP52 in squirrel monkeys contribute to androgen insensitivity, squirrel monkey cells were transfected with an AR expression plasmid, an AR-responsive reporter plasmid, and a plasmid expressing FKBP52. Expression of FKBP52 decreased the EC50 or increased the maximal response to dihydrotestosterone. Therefore, the high androgen levels in squirrel monkeys likely compensate for their relatively low 5 alpha-reductase activity during the breeding season and AR insensitivity resulting from low cellular levels of FKBP52.     

A kidney epithelial cell line from a Bolivian squirrel monkey

Squirrel monkeys are the most commonly used New World primates in biomedical research, but in vitro studies are restricted by the limited number of cell lines available from this species. We report here the development and characterization of a continuous, kidney epithelial cell line (SQMK-FP cells) derived from a newborn squirrel monkey. Karyotype was consistent with Bolivian squirrel monkey (submetacentric chromosome pair 15 and acrocentric chromosome pair 16). All cells examined were hyperdiploid with chromosome numbers ranging from 52 to 57. Ultrastructural analysis of SQMK-FP cells revealed the presence of cell junctions with radiating filaments, indicating desmosomes and numerous surface projections containing longitudinally oriented filaments typical of tubular epithelium. Biochemically, SQMK-FP cells exhibit glucocorticoid resistance typical of the squirrel monkey. Glucocorticoid receptor (GR) binding is low in SQMK-FP cells because of high expression of the FK506-binding immunophilin FKBP51 that inhibits GR binding. SQMK-FP cells constitute a tubular epithelial cell line that has biochemical properties characteristic of squirrel monkeys and represents an alternate cell model to B-lymphoblast SML cells to study the biology of the squirrel monkey in vitro.     

Hemobartonellosis in squirrel monkeys (Saimiri sciureus) in a domestic breeding colony: case report and preliminary study

Infection with Hemobartonella sp was diagnosed in a colony-born squirrel monkey with normocytic, normochromic anemia and pronounced punctate erythrocytic basophilic stippling on Wright's-Giemsa stained blood films. The diagnosis was confirmed using transmission electron microscopy. Two randomly selected colony-born squirrel monkeys were splenectomized in an effort to activate and detect possible latent hemobartonellosis . One monkey became parasitemic 12 days following splenectomy. The second monkey was inoculated on day 14 with 1 ml of whole blood from an infected, but nonparasitemic monkey and developed overt parasitemia 3 days later (day 17 following splenectomy). Infections in the latter two monkeys were confirmed using scanning electron microscopy.     

Squirrel monkey--an ideal primate (correction of prmate) model of space physiology]

Investigation of the vestibulo-ocular system of the squirrel monkey was reviewed in consideration of space motion sickness (SMS), or which is recently more often termed as space adaptation syndrome (SAS). Since the first launching of the space satellite, Sputnik [correction of Sputonik] in October 1957, many experiments were carried out in biological and medical fields. A various kind of creatures were used as experimental models from protozoa to human beings. Rats and monkeys are most favorite animals, particularly the non-human primate seems to be the one, because of its phylogenetic relatives akin to the human beings. Chimpanzees, rhesus monkeys, pig tailed-monkeys, red-faced monkeys and squirrel monkeys have been used mostly in American space experiments. Russian used rhesus monkeys. Among these, however, the squirrel monkey has an advantage of the small size of the body, ranging from 600- l000g in adult. This small size as a primate is very advantageous in experiments conducted in a narrow room of the space satellite or shuttle because of its space-saving. The squirrel monkey has another advantage to rear easily as is demonstrated to keep it as a pet. Accordingly, this petit animal provides us a good animal model in biological and medical experiments in space craft. The size of the brain of the squirrel monkey is extraordinary large relative to the body size, which is even superior to that of the human beings. This is partly owed to enlargement of the occipito-temporal cortices, which are forced to well develop for processing a huge amount of audio-visual information indispensable to the arboreal habitant to survive in tropical forest. The vestibular system of the squirrel monkey seems to be the most superior as well, when judged from it relative size of the vestibular nuclear complex. Balancing on swinging twigs or jumping from tree to tree developed the capability of this equilibrium system. Fernandez, Goldberg and his collaborators used the squirrel monkey to elucidate functions of the peripheral vestibular system. A transfer function was proposed to explain the behaviors of regular and irregular unit activity of vestibular nerve fibers. The physiologic characteristics of the second order vestibular neuron was investigated in combination of electrophysiological and micro-morphological way, with using WGA-HRP methods, in relation to somato-motor and eye movements. Interconnections between vestibular neurons and cerebellum, interstitial nucleus of Cajal, oculomotor nuclear complex, superior colliculus and cervical spinal cord were elucidated. In physiological field of the vestibular system, the vestibulo-ocular reflex is well studied and results obtained from the squirrel monkey experiments were reviewed. The squirrel monkey, particularly the Bolivian, is a unique animal in that it is vulnerable to motion sickness induced by visual-motion stimulation with phase mismatch of the two stimuli. Experimental results of labyrinthectomy or bilateral ablation of the maculae staticae led to the conclusion that both semicircular and otolith organs are involved in the genesis of space motion sickness. On the other hand, destruction of the area postrema, acknowledged as the vomiting center to chemical stimulants, produced controversial results. However, it must be pointed out that the a human subject underwent to resection of the area postrema, became insensitive to administration of apomorphine, a well known chemical stimulant of vomiting. Finally the experiments in space revealed the presence of at least two origins of caloric nystagmus, that is, attributable to convection and non-convection current of the endolymphatic fluid.     

Age-related changes of immunoglobulin levels in African green monkeys (Cercopithecus aethiops)

Serum IgG, IgA, and IgM levels were measured in domestically bred African green monkeys (Cercopithecus aethiops) ranging in age from 0 day to 49 months as well as in adult (5 years or older) animals of wild origin. Transplacental transfer of IgG was observed. IgG, IgA, and IgM levels increased with increasing age except for a temporal decrease of IgG level in the first month of life.     

An immunoradiometric assay for squirrel monkey prolactin.

Determination of immunoreactive prolactin in squirrel monkeys has been hampered by the lack of specific antibodies. We investigated the adaptability of a commercially available immunoradiometric assay for human prolactin, which employs two separate monoclonal antibodies (MAb I and II) to human prolactin, to determine the presence of squirrel monkey prolactin. We found that immunoreactivity curves for prolactin in squirrel monkey pituitary homogenates and serum were parallel to human prolactin standards, suggesting that the epitopes recognized by these antibodies were common to both human and squirrel monkey prolactin. Both nonglycosylated (23 kD) and glycosylated (26 kD) forms of squirrel monkey prolactin were detected in squirrel monkey pituitary homogenates by Western blot analysis using [125I]-MAb II. Neither sheep nor rat prolactin was recognized by Western blot analysis, indicating that the assay may be specific for primate prolactins. We examined the effect of ketamine HCl, an anesthetic that has been shown to elevate serum prolactin levels in other primates, on prolactin secretion in squirrel monkeys. Serum prolactin levels increased greater than fourfold after the administration of ketamine HCl (30 mg/kg b.w., i.m.) compared with control levels. Serum prolactin levels were unaffected by anesthesia with pentobarbital sodium (15 mg/kg b.w., i.v.). This assay provides a reliable and sensitive method for determining immunoreactive squirrel monkey prolactin.     

Comparison of antigenicity of serum immunoglobulin G among human, cynomolgus monkey, African green monkey and squirrel monkey

Antigenicity of IgG was compared among human, the cynomolgus monkey, the African green monkey and the squirrel monkey by the quantitative precipitation test using purified IgG of and rabbit anti-IgG serum to each species. Clear cross-antigenicity was observed between the cynomolgus monkey and the African green monkey and less clear cross-antigenicity between human and the cynomolgus monkey or the African green monkey. The cross-antigenicity observed between the squirrel monkey and the other three species examined was evidently weak.     

Hypoglycemia of squirrel monkey neonates: implications for infant survival

Neonatal deaths are a serious problem in breeding colonies of squirrel monkeys. Seriously ill neonates in our colony are always hypoglycemic on presentation. To determine normal glucose values for squirrel monkey infants of various ages, serum glucose determinations were done at 1, 3, 7, 10, 14 days and 1 month of age using a standard laboratory test for serum glucose. Glucose concentration increased from a low of 49 +/- 3 mg/dl (Mean +/- SEM) at 1 day (n = 21) to 109 +/- 4 mg/dl at 1 month of age (n = 17). Glucose values for 1, 3 and 7 day-old infants were significantly lower than 1 month-old infants (P less than .05). To provide a time-averaged indication of blood glucose, glycosylated hemoglobin (GHb) measurements were made at 1 day, 1 week, 2 weeks, 1 month, 2 months, 1 year of age and in adults (greater than 3 years of age). GHb values ranged from 2.6% +/- 0.1 for 1 day old infants (n = 13) to 4.0 +/- 0.2 for adults (n = 10) with a steady increase during the first 2 months of life. Animals 1 year of age and younger had significantly lower glycosylated hemoglobin than adults. These studies indicate that blood glucose concentration is significantly lower in squirrel monkey neonates than in older infants, juveniles and adults. Maternal rejection, trauma, and associated problems occur commonly in socially reared squirrel monkeys. The marginal hypoglycemic state of these infants places them at high risk for clinical hypoglycemia as a sequel to such perturbations.