Trichomonad Gastritis in Rhesus Macaques (Macaca mulatta) Infected with Simian Immunodeficiency Virus

In a retrospective study, 51 cases of gastritis (14%) were identified from among 341 necropsies performed on simian immunodeficiency virus (SlV)-infected rhesus macaques ( Macaca mulatta) at the New England Primate Research Center from 1993 to 2001. Protozoa were seen in the stomach of 13 monkeys (25%) with gastritis. Two histopathologic manifestations of gastritis were observed: seven cases of lymphoplasmacytic gastritis with trichomonad trophozoites within lumens of gastric glands and four cases of necrosuppurative gastritis containing intralesional periodic acid-Schiff-positive protozoa; two cases of gastritis had morphologic features of both types of gastritis. In instances of necrosuppurative and combined lymphoplasmacytic and necrosuppurative gastritis, protozoa were 4-35 μm in diameter and round to tear-shaped. Because of the unusual morphology of the protozoa in these latter cases, transmission electron microscopy and polymerase chain reaction (PCR) were used to further identify these organisms. The protozoa were definitively identified as Tritrichomonas in all cases on the basis of ultrastructural characteristics (flagella and undulating membranes) and amplification of a 347-bp product of the 5.8S ribosomal RNA gene of Tritrichomonas foetus, Tritrichomonas suis and Tritrichomonas mobilensis by PCR using DNA extracted from stomach tissue. On the basis of these observations, we conclude that Tritrichomonas can be a significant cofactor in the development of necrosup-purative gastritis in SIV-infected rhesus macaques.

Ovarian pathology in rhesus macaques: a 12-year retrospective

BACKGROUND

Ovarian pathology is an important cause of decreased fertility and reproductive capability and may impact multiple systems, particularly in aging rhesus macaques.

METHODS

Retrospective histopathologic and immunohistochemical analysis of 458 female rhesus macaque necropsies over 12 years at the New England Primate Research Center in Southborough, MA.

RESULTS

Degenerative and inflammatory changes in the ovaries included mineralization, infiltration by lymphocytes, macrophages and multinucleated giant cells, endometriosis, and arteriopathy. Cystic changes included follicular cysts, cystic rete, and mesonephric duct cysts with cystic rete the most common. Neoplasms included granulosa cell tumors, cystadenoma, cystadenocarcinoma, and teratoma.

CONCLUSIONS

Ovarian lesions of the rhesus macaque are similar to those of cynomolgus macaques and humans. These lesions are frequently incidental findings but may impact metabolic and neurocognitive studies.

Rhesus lymphocryptovirus type 1-associated B-cell nasal lymphoma in SIV-infected rhesus macaques

Epstein-Barr virus (EBV) is a worldwide endemic gamma herpesvirus of the genus Lymphocryptovirus (LCV) that infects more than 90% of the world's population. EBV has been associated with a variety of malignancies, but it has a demonstrated role in lymphomas, especially in immunosuppressed individuals. Lymphomas of the nasal cavity, paranasal sinuses, and nasopharynx are uncommon and constitute less than 5% of all extranodal lymphomas. Sinonasal non-Hodgkin's lymphomas have been reported in patients infected with human immunodeficiency virus (HIV) at an increased frequency. Rhesus LCV (rhLCV), the rhesus viral homolog of EBV, has been cloned and is associated with B-cell lymphomas in immunosuppressed rhesus macaques. We report two cases of B-cell lymphoma within the nasal cavity from 2 simian immunodeficiency virus-infected rhesus macaques with acquired immunodeficiency syndrome. The B-cell phenotype and rhLCV association were demonstrated by immunohistochemistry and confocal microscopy. The majority of the nuclei of the neoplastic B lymphocytes were EBNA-2 positive. RhLCV type 1 sequences were verified from the neoplasms by polymerase chain reaction. Nasal lymphoma is an unusual presentation of rhLCV-associated B-cell lymphoma in immunosuppressed rhesus macaques. These tumors demonstrate comparable viral pathogenesis with EBV-induced nasal lymphomas in HIV-positive people.

Immunoglobulin-A nephropathy with crescentic glomerulonephritis in a pigtailed macaque (Macaca nemestrina)

A 4-year-old female pigtailed macaque (Macaca nemestrina), experimentally coinfected with simian immunodeficiency virus (SIVmac251) and Mycobacterium bovis(bacillus Calmette-Guerin), was euthanatized 1 year after infection because of weight loss and labored breathing. On gross examination, both kidneys were found to be markedly enlarged (right: 54.7 g and left: 51.7 g; normal < 20 g). Renal lesions were evaluated by histopathologic, immunohistochemical, and ultrastructural methods. Light microscopy revealed that the glomeruli were diffusely hypercellular with expansion of the mesangial matrix, and crescent formation affected approximately 60% of the glomeruli. By immunohistochemical evaluation, it was found that the crescents were composed principally of macrophages, as seen by CD68 (KP1), MRP8, MAC387, and HAM56 expression. Electron microscopic examination of the glomeruli revealed extensive intramembranous, subendothelial, and mesangial electron-dense deposits and multifocal fusion of the visceral epithelial foot processes. Immunofluorescence, used to determine the composition of the electron-dense deposits, revealed diffuse granular mesangial and capillary staining for immunoglobulin A (IgA). The renal changes described in this case report are most consistent with the findings of crescentic gloerulonephritis with IgA immune complex deposition in the glomerular basement membrane and mesangium as described in humans with IgA nephropathy.

Postinoculation PMPA treatment, but not preinoculation immunomodulatory therapy, protects against development of acute disease induced by the unique simian immunodeficiency virus SIVsmmPBj

The fatal disease induced by SIVsmmPBj4 clinically resembles endotoxic shock, with the development of severe gastrointestinal disease. While the exact mechanism of disease induction has not been fully elucidated, aspects of virus biology suggest that immune activation contributes to pathogenesis. These biological characteristics include induction of peripheral blood mononuclear cell (PBMC) proliferation, upregulation of activation markers and Fas ligand expression, and increased levels of apoptosis. To investigate the role of immune activation and viral replication on disease induction, animals infected with SIVsmmPBj14 were treated with one of two drugs: FK-506, a potent immunosuppressive agent, or PMPA, a potent antiretroviral agent. While PBMC proliferation was blocked in vitro with FK-506, pig-tailed macaques treated preinoculation with FK-506 were not protected from acutely lethal disease. However, these animals did show some evidence of modulation of immune activation, including reduced levels of CD25 antigen and FasL expression, as well as lower tissue viral loads. In contrast, macaques treated postinoculation with PMPA were completely protected from the development of acutely lethal disease. Treatment with PMPA beginning as late as 5 days postinfection was able to prevent the PBj syndrome. Plasma and cellular viral loads in PMPA-treated animals were significantly lower than those in untreated controls. Although PMPA-treated animals showed acute lymphopenia due to SIVsmmPBj14 infection, cell subset levels subsequently recovered and returned to normal. Based upon subsequent CD4(+) cell counts, the results suggest that very early treatment following retroviral infection can have a significant effect on modifying the subsequent course of disease. These results also suggest that viral replication is an important factor involved in PBJ-induced disease. These studies reinforce the idea that the SIVsmmPBj model system is useful for therapy and vaccine testing.

Brain weight throughout the life span of the chimpanzee

Studies on human postmortem material report lower brain weights in older than in younger cohorts, whereas there is no apparent change with age in the rhesus monkey. In view of these contrasting results, we examined the pattern of brain weight across the life span in the chimpanzee, one of the closest biological relatives of humans. To place the study in context of the empirical life expectancy of the chimpanzee, we first performed a survival analysis on data from 275 chimpanzees that were maintained in the colony of the Yerkes Primate Center. The survival analysis revealed the maximum life spans of female and male chimpanzees to be about 59 and 45 years, respectively. We examined fresh brain weights from 76 chimpanzees ranging in age from birth to 59.4 years of age. The brains were taken from 9 infants (birth to 1 year of age), 25 juveniles (1-7 years), 13 adolescents (7-15 years), 21 young adults (15-30 years), and 8 old adults (over 30 years). Adult brain weight was achieved by the age of 7 years. The adolescent and young adult chimpanzees had the largest brain weights; in these two age groups combined, the mean brain weight (+/- standard deviation) was 368.1 g (+/-37.3) for females (n = 17) and 405.6 g (+/-39.4) for males (n = 17). This sex difference was statistically significant (P < 0.01). Simple linear regression performed on the combined material from females and males aged 7 years and older revealed a decline in brain weight with advancing age of 1.1 g/year (P < 0.05). When the effect of sex on brain weight was statistically controlled for, the loss of brain weight with age was 0.9 g/year (P = 0.07). These results suggest that brain weight declines moderately with age in the chimpanzee as it does in humans.

Isolation and characterization of a neuropathogenic simian immunodeficiency virus derived from a sooty mangabey

Transfusion of blood from a simian immunodeficiency virus (SIV)- and simian T-cell lymphotropic virus-infected sooty mangabey (designated FGb) to rhesus and pig-tailed macaques resulted in the development of neurologic disease in addition to AIDS. To investigate the role of SIV in neurologic disease, virus was isolated from a lymph node of a pig-tailed macaque (designated PGm) and the cerebrospinal fluid of a rhesus macaque (designated ROn2) and passaged to additional macaques. SIV-related neuropathogenic effects were observed in 100% of the pig-tailed macaques inoculated with either virus. Lesions in these animals included extensive formation of SIV RNA-positive giant cells in the brain parenchyma and meninges. Based upon morphology, the majority of infected cells in both lymphoid and brain tissue appeared to be of macrophage lineage. The virus isolates replicated very well in pig-tailed and rhesus macaque peripheral blood mononuclear cells (PBMC) with rapid kinetics. Differential replicative abilities were observed in both PBMC and macrophage populations, with viruses growing to higher titers in pig-tailed macaque cells than in rhesus macaque cells. An infectious molecular clone of virus derived from the isolate from macaque PGm (PGm5.3) was generated and was shown to have in vitro replication characteristics similar to those of the uncloned virus stock. While molecular analyses of this virus revealed its similarity to SIV isolates from sooty mangabeys, significant amino acid differences in Env and Nef were observed. This virus should provide an excellent system for investigating the mechanism of lentivirus-induced neurologic disease.

Ultrastructure of atypical (teratoid) sporogonial stages of Enterocytozoon bieneusi (Microsporidia) in naturally infected rhesus monkeys (Macacca mulatta)

OBJECTIVE

To demonstrate the ultrastructural features of normal and atypical (teratoid) developmental stages of Enterocytozoon bieneusi in naturally infected rhesus monkeys (Macacca mulatta).

DESIGN AND METHODS

Two rhesus monkeys with chronic simian immunodeficiency virus infection developed naturally acquired microsporidian infections. The gallbladder had a high parasite burden and was evaluated by transmission electron microscopy. The microsporidian agent was confirmed as E bieneusi by polymerase chain reaction.

RESULTS

In addition to normal sporogonial plasmodia and spores of E bieneusi, abnormal teratoid structures were noted. These structures were greatly enlarged (up to 10 microm) and were surrounded by an electron-dense exospore and electron-lucent endospore typical of mature spores. Unlike mature spores, the abnormal structures contained multiple nuclei and polar tubes in varying proportions, which were reminiscent of sporogonial plasmodia.

CONCLUSIONS

These teratoid structures represent aberrant sporogonial stages, a result of defective maturation in which abnormal cytokinetic replication of organelles occurs, and normal development into uninucleate sporoblasts and spores is inhibited. This leads to the development of teratoid stages having mature spore walls, but containing multiple sets of nuclei and polar tubes, unusual polyribosomal arrays and vacuoles, or persistent cleavage. The biological significance of these atypical spores is unknown, but it is evident that they develop in the absence of antimicrosporidian drugs in extraintestinal tissues from nonhuman primates. Teratoid spores of E bieneusi should not be misinterpreted as another microsporidian species or confused with other pathogenic protozoa, nor should their presence be misconstrued as evidence of antimicrosporidian drug efficacy or toxicity.

Brain weight does not decrease with age in adult rhesus monkeys

Cross-sectional studies on adult human autopsy material have shown that younger cohorts have heavier brains than older groups. We sought to determine whether a similar pattern is present in the rhesus monkey, a species that serves as a useful model of human brain and cognitive aging. Data were obtained from necropsies of 399 rhesus monkeys (180 females; 219 males), of ages covering the entire adult lifespan of this species. In addition to fresh brain weight, variables considered were age, sex, body weight, heart weight, identity of the prosector, and circumstance of death. Initial bivariate analyses revealed a significant sex difference in brain weight (mean for males: 96.1 g; for females: 86.1 g; p < 0.001), as well as significant correlations of brain weight with body weight (r = 0.20, p < 0.01 for females; r = 0.27, p < 0.001 for males), and heart weight (r = 0.27, p < 0.001 for females; r = 0.38, p < 0.001 for males). Identity of prosector, circumstance of death, and age were not significantly related to brain weight in bivariate analyses. Multiple linear regression, controlling for possible confounding effects of body weight and sex, also suggested that brain weight is stable throughout adulthood in the rhesus monkey.

Development of AIDS in a chimpanzee infected with human immunodeficiency virus type 1

The condition of a chimpanzee (C499) infected with three different isolates of human immunodeficiency virus type 1 (HIV-1) for over 10 years progressed to AIDS. Disease development in this animal was characterized by (i) a decline in CD4+ cells over the last 3 years; (ii) an increase in viral loads in plasma; (iii) the presence of a virus, termed HIV-1JC, which is cytopathic for chimpanzee peripheral blood mononuclear cells; and (iv) the presence of an opportunistic infection and blood dyscrasias. Genetic analysis of the V1-V2 region of the envelope gene of HIV-1JC showed that the virus present in C499 was significantly divergent from all inoculating viruses (> or = 16% divergent at the amino acid level) and was suggestive of a large quasispecies. Blood from C499 transfused into an uninfected chimpanzee (C455) induced a rapid and sustained CD4+-cell decline in the latter animal, concomitant with high plasma viral loads. These results show that HIV-1 can induce AIDS in chimpanzees and suggest that long-term passage of HIV-1 in chimpanzees can result in the development of a more pathogenic virus.

Chemotherapy-induced hemolytic uremic syndrome: description of a potential animal model

Hemolytic uremic syndrome (HUS) is an uncommon complication of chemotherapy that contributes to the morbidity of oncology and bone marrow transplant patients. The pathogenesis is not well understood and no established clinical animal model exists. We studied four rhesus monkeys (RM) that developed fatal HUS following high-dose chemotherapy. Microangiopathic hemolytic anemia (pre-Hct 40% and day 5-8 Hct 31% (P < .05), increased BUN (168 mg/dl), creatinine (8.2 mg/dl), and lactate dehydrogenase (1458 IU/L) (mean day 5-8 measurements) were observed. Platelets counts decreased to 39 +/- 15 x 10(9)/l from a mean of 397 +/- 31 x 10(9)/L (P < .0001). vWF, ATIII, thrombin:anti-thrombin complex (T:AT) and prothrombin fragment F1.2 levels were not different from a control group (N = 2). The data presented describe chemotherapy-induced HUS with typical clinical and laboratory features which may provide an animal model for the study of this important syndrome.

Encephalomyelitis due to a Sarcocystis neurona-like protozoan in a rhesus monkey (Macaca mulatta) infected with simian immunodeficiency virus

A captive-born rhesus monkey (Macaca mulatta) experimentally infected with simian immunodeficiency virus developed neurologic abnormalities approximately seven months postinoculation. A chronic necrotizing encephalomyelitis with intralesional protozoal schizonts was diagnosed histologically. The protozoa was identified as Sarcocystis neurona based on its morphologic characteristics by light and electron microscopic examination, the developmental stages of the schizonts, and positive staining with antisera against Sarcocystis cruzi by immunocytochemical techniques. Although S. neurona may be confused with Toxoplasma gondii by light microscopy, the former lacks rhoptries, is in direct contact with the host cell cytoplasm, and divides by endopolygeny. Sarcocystis neurona has recently been identified as an etiologic agent of encephalomyelitis in horses, raccoons, and mink.

Multifactorial etiology of anemia in SIV-infected rhesus macaques: decreased BFU-E formation, serologic evidence of autoimmune hemolysis, and an exuberant erythropoietin response

We attempted to define the etiology of anemia in SIV-infected rhesus macaques. Bone marrow culture showed significantly decreased (75% reduction) burst forming unit-erythroid (BFU-E) growth in end-stage SIV+ "sick" animals. Direct antiglobulin tests (DAT) were positive in nine of 35 SIV+ "well" and 14 of 14 SIV+ "sick" monkeys (0 of 25 control animals had positive DATs). In animals with a positive DAT, moderate to severe anemia was observed, as was increased LDH and spherocytosis. Erythropoietin was measured in four control, eight SIV+ "well" and five SIV+ "sick" animals with mean levels of 4.0, 15.4, and 1176 mU/mL (r = .94) in the three groups. These data suggest that the cause of anemia in the SIV-infected rhesus macaque is multifactorial, that there may be a defect in erythropoiesis, and that, serologically, an IgG mediated autoimmune hemolytic anemia is also present.

Clinical and pathologic findings in infant rhesus macaques infected with SIVsmm by maternal transmission

Three of 12 infant rhesus macaques became infected at 9 to 12 months of age with SIVsmm through maternal-infant transmission. Clinical problems seen in one or more infants included decreased CD4 cells, hypergammaglobulinemia, diarrhea, weight loss, anemia, bacterial infections, and terminal respiratory and CNS problems. Gross and histologic lesions due to both primary SIV infection and opportunistic infections were observed. The SIV-infected infants had clinical, immunologic, and pathologic similarities to those seen in pediatric HIV infection.

The simian immunodeficiency virus infected macaque: a model for pediatric AIDS

Maternal-to-infant transmission of simian immunodeficiency virus (SIV) has been demonstrated in the rhesus macaque following experimental infection of pregnant rhesus monkeys, either parenterally or by inoculation of virus into the amniotic fluid. Virus infection occurred in 3 of 12 (25%) rhesus infants born to mothers with SIV infection induced by parenteral inoculation of virus during gestation. However, these infants did not become seropositive or virus positive until they were 9-15 months old, suggesting that virus infection most likely occurred as the result of breast feeding. Infection has also been demonstrated in one rhesus infant following virus inoculation into the amniotic fluid during late gestation. These observations support the increasing evidence that intrapartum or postpartum infection may be important mechanisms for the maternal-infant transmission of HIV. The SIV-infected macaque should prove to be a useful model to evaluate the timing and mechanisms of lentivirus infection in infants, to determine maternal factors associated with transmission to the fetus or infant, and to evaluate therapeutic regimens for the prevention or treatment of pediatric AIDS.

Maternal transmission of SIVsmm in rhesus macaques

Fifteen SIV-infected rhesus monkeys delivered 13 livebirths and two stillbirths; one livebirth died at three days of age. While all infants were culture-negative for SIV at birth, nine had maternal antibodies that disappeared by six months of age. Three infants subsequently seroconverted and became virus positive at 9-15 months. Milk samples from all mothers were virus-negative at parturition but samples from four animals were virus-positive at nine and 12 months. This study documents maternal transmission of SIV and suggests transmission by breast-feeding.

Inherited selective intestinal cobalamin malabsorption and cobalamin deficiency in dogs

Inherited selective intestinal malabsorption of cobalamin (Cbl) was observed in a family of giant schnauzer dogs. Family studies and breeding experiments demonstrated simple autosomal recessive inheritance of this disease. Affected puppies exhibited chronic inappetence and failure to thrive beginning between 6 and 12 wk of age. Neutropenia with hypersegmentation, anemia with anisocytosis and poikilocytosis, and megaloblastic changes of the bone marrow were present. Serum Cbl concentrations were low, and methylmalonic aciduria and homocysteinemia were present. Parenteral, but not oral, cyanocobalamin administration rapidly eliminated all signs of Cbl deficiency except for low serum Cbl concentrations. Cbl malabsorption in affected dogs was documented by oral administration of [57Co]cyanocobalamin with or without simultaneous oral administration of intrinsic factor or normal dog gastric juice. Quantitation and function studies of intrinsic factor and transcobalamin-II from affected dogs revealed no abnormality. Other gastrointestinal functions and ileal morphology were normal, indicating a selective defect of Cbl absorption at the level of the ileal enterocyte. Immunoelectron microscopy of ileal biopsies showed that the receptor for intrinsic factor-Cbl complex was absent from the apical brush border microvillus pits of affected dogs. This canine disorder resembles inherited selective intestinal Cbl malabsorption (Imerslund-Gräsbeck syndrome) in humans, and is a spontaneously occurring animal model of early onset Cbl deficiency.

Nonhuman primate models for evaluation of AIDS therapy

Infection of macaque monkeys with simian immunodeficiency virus (SIV) has been established as an excellent animal model system for studying the pathogenesis of an HIV-like virus and for evaluating newly developed antiretroviral drugs and vaccines. Based on their genetic, antigenic, and biologic properties, the simian immunodeficiency viruses are the closest known relatives of the human AIDS viruses, and experimental infection of macaque monkeys results in a disease that is remarkably similar to human AIDS. Infected macaques show diarrhea, weight loss, hematologic abnormalities including lymphopenia and thrombocytopenia, lymphadenopathy/lymphoid hyperplasia that progresses to lymphoid depletion, immunosuppression with marked reduction in CD4+ cells and in the CD4+/CD8+ cell ratio, and opportunistic infections. A majority of such macaques die from an AIDS-like disease within one to three years of infection. An acutely lethal variant of SIV has been identified that results in death in susceptible macaques within 7-12 days of infection. Preliminary prophylactic treatment trials with AZT in macaque monkeys exposed to the acutely lethal SIV variant indicate that some protection is provided when AZT treatment is initiated within 24 hours of virus exposure. Other studies with the more chronic SIV infection model, however, failed to show any prophylactic efficacy of CS-87, AZT, D4T, or FDT.

Survey of the pathologic findings in a large production colony of pigeons, with special reference to pseudomembranous stomatitis and nephritis

Pathologic evaluations of pigeons dying between September 1984 and August 1985 are reported for a production colony of 1200-1800 White Carneau and Show Racer pigeons ranging in age from hatchlings to 12 years. Infectious diseases were the common causes of death in pigeons younger than 1 year; salmonellosis and nephritis were the common causes in pigeons 1-3 years old; and neoplasia and reproductive organ disorders were the common causes in pigeons older than 3 years. Monthly mortality was 2-4% in pigeons fed a cholesterol-containing diet and 0.9% in those fed noncholesterol-containing pellet diets. The increased deaths in the cholesterol-fed birds were attributed primarily to end-stage renal disease and atherosclerosis with secondary complications. The most frequently observed clinical entity in pigeons younger than 6 months was pseudomembrane formation on the oral and pharyngeal mucosa, termed pseudomembranous stomatitis. The definitive etiologic factor was not determined. Although all affected pigeons had similar gross lesions, the cases fell into one of three subsets, suggestive of bacterial, fungal, or viral etiologies. Chronic nephritis occurring as end-stage renal disease was more severe in pigeons fed a cholesterol-containing diet.

Salmonella osteomyelitis in a rhesus monkey

An adult male rhesus monkey (Macaca mulatta) developed clinical signs of severe osteomyelitis of the left femur 42 days after onset of enteritis. Salmonella sp. were cultured from feces, blood, and femoral lesions. Response to antibiotic therapy was poor, and the animal was euthanized. The left femur, with pathologic fracture and involucrum, and the right femur, tibia and fibula were most severely affected. Additionally hepatic microgranulomas, mild tubulointerstitial nephritis, medullary histiocytosis and erythrophagocytosis in the lymph nodes, and a mild colitis were diagnosed microscopically. The severity of the disease and serum electrophoresis findings were suggestive of lowered resistance to the organism, possibly due to anemia or polychlorinated biphenyl toxicosis.