Induction of AIDS-like disease in macaque monkeys with T-cell tropic retrovirus STLV-III.

The T-cell tropic retrovirus of macaque monkeys STLV-III has morphologic, growth, and antigenic properties indicating that it is related to HTLV-III/LAV, the etiologic agent of the acquired immune deficiency syndrome (AIDS) in humans. Four of six rhesus monkeys died within 160 days of STLV-III inoculation with a wasting syndrome, opportunistic infections, a primary retroviral encephalitis, and immunologic abnormalities including a decrease in T4+ peripheral blood lymphocytes. These data show that an immunodeficiency syndrome can be produced experimentally in a nonhuman primate by an agent from the HTLV-III/LAV group of retroviruses. The STLV-III-macaque system will thus provide a useful model for the study of antiviral agents and vaccine development for human AIDS.

Gastrointestinal tract as a major site of CD4+ T cell depletion and viral replication in SIV infection.

Human and simian immunodeficiency virus (HIV and SIV) replicate optimally in activated memory CD4(+) T cells, a cell type that is abundant in the intestine. SIV infection of rhesus monkeys resulted in profound and selective depletion of CD4+ T cells in the intestine within days of infection, before any such changes in peripheral lymphoid tissues. The loss of CD4+ T cells in the intestine occurred coincident with productive infection of large numbers of mononuclear cells at this site. The intestine appears to be a major target for SIV replication and the major site of CD4+ T cell loss in early SIV infection.

In vivo administration of lymphocyte-specific monoclonal antibodies in nonhuman primates. Delivery of ribosome-inactivating proteins to spleen and lymph node T cells.

The selective delivery in vivo of a T lymphocyte-specific monoclonal antibody and immunotoxin conjugates to T cells in lymph node and spleen was assessed in rhesus monkeys. A transient coating of all T lymphocytes in the lymph nodes and spleens of healthy rhesus monkeys could be achieved after infusion of unconjugated anti-T11. Because derivatized antibody is cleared more rapidly than unconjugated antibody, it was necessary to infuse a higher dose of immunotoxin than antibody alone to achieve saturation of the lymphocyte binding sites with anti-T11. When sufficient antibody-toxin conjugate was infused, toxin was readily demonstrable on lymph node and spleen T cells by 16 h after infusion. This demonstration that toxins can be successfully delivered with specificity to target T cell populations in the monkey suggests that killing of restricted cell populations in vivo should be feasible.

In vivo administration of lymphocyte-specific monoclonal antibodies in nonhuman primates. IV. Cytotoxic effect of an anti-T11-gelonin immunotoxin.

The cytotoxic effect of a lymphocyte-specific immunotoxin formed by disulfide conjugation of an anti-T11 monoclonal antibody with the ribosome-inactivating protein gelonin was assessed in vitro on peripheral blood T cells and in vivo on splenic and lymph node T cells of macaque monkeys. This immunotoxin was cytotoxic to proliferating peripheral blood T cells in vitro as measured by both direct and indirect assays. Two sequential intravenous infusions into macaque monkeys achieved plasma concentrations of immunotoxin far in excess of those shown to be cytotoxic for cultured T cells and coated all T cells in lymph nodes and spleen with intact immunotoxin for four days. However, the cytotoxic effect of the immunotoxin on T cells in vivo was considerably less than that predicted by the in vitro studies. Further experiments suggested that the state of activation of the targeted T cell population in vivo, or the appearance of anti-immunotoxin antibodies, which occurred in all infused monkeys, might attenuate immunotoxin-mediated cell killing in vivo. These studies illustrate the significant differences between the action of immunotoxin conjugates in vitro, and those seen when these conjugates are utilized as therapeutic agents in vivo.

An activated CD8+ lymphocyte appears in lymph nodes of rhesus monkeys early after infection with simian immunodeficiency virus.

Although alterations in T lymphocyte subset distribution and function in the peripheral blood of HIV-infected humans are well defined, the extent to which these reflect changes in other lymphoid compartments is unclear. We have characterized the coincident changes in PBL and lymph nodes (LN)1 after simian immunodeficiency virus of macaques (SIVmac) infection of rhesus monkeys. Whereas no consistent change in CD8+ PBL was noted during the first 60 d after infection, CD8+ lymphocytes increased significantly in number in LN. These CD8+ LN lymphocytes exhibited an increased expression of MHC class II and a decreased expression of leukocyte adhesion molecule-1, suggesting that they were activated, but interestingly did not express CD25 (IL-2 receptor). Moreover, there was no evidence that these CD8+ LN cells were proliferating, suggesting that they had migrated to the LN. These changes in the LN CD8+ lymphocyte population preceded any detectable change in the light microscopic appearance of the LN. When SIVmac-specific effector T cell responses were assessed, the magnitude of virus-specific effector activity was nearly identical in the PBL and LN of each monkey studied. However, the presence of SIVmac-specific effector cells in the LN did not correlate with the presence of CD8+, MHC class II+ cells. These findings suggest that this numerically important CD8+ lymphocyte subpopulation may serve a regulatory function.

Pathologic features of SIV-induced disease and the association of macrophage infection with disease evolution.

Since the original isolation of simian immunodeficiency virus (SIV) from a macaque with an AIDS-like disease, numerous studies have demonstrated the close biologic and genetic relationship of the SIVs to the HIVs. Probably most important, the clinical spectrum of disease associated with SIVmac/SIVsmm infection in rhesus monkeys is strikingly similar to AIDS in HIV-1-infected human beings. Herein are summarized the pathologic features of SIVmac-induced disease in a cohort of rhesus monkeys, with special reference to the role of infected macrophages in the development of AIDS-related manifestations.

Enterocytozoon bieneusi as a cause of proliferative serositis in simian immunodeficiency virus-infected immunodeficient macaques (Macaca mulatta).

CONTEXT: Enterocytozoon bieneusi is the most frequent microsporidian parasite of human patients with acquired immunodeficiency syndrome and is a significant cause of diarrhea and wasting. Recently, this organism has also been recognized as a spontaneous infection of several species of captive macaques. As in humans, E bieneusi frequently causes enteropathy and cholangiohepatitis in immunodeficient simian immunodeficiency virus (SIV)-infected macaques. OBJECTIVE: To examine E bieneusi as an etiologic agent of nonsuppurative proliferative serositis in immunodeficient rhesus macaques (Macaca mulatta). DESIGN: Retrospective analysis of necropsy material obtained from immunodeficient SIV-infected rhesus macaques. RESULTS: Examination of SIV-infected rhesus macaques (n = 225) revealed E bieneusi proliferative serositis in 7 of 16 cases of peritonitis of unknown origin. The organism could be identified by in situ hybridization and polymerase chain reaction in sections of pleura and peritoneum obtained at necropsy. Serositis was always accompanied by moderate-to-severe infection of the alimentary tract, and morphologic evidence suggested dissemination through efferent lymphatics. Colabeling experiments revealed most infected cells to be cytokeratin positive and less frequently positive for the macrophage marker CD68. Sequencing of a 607-base pair segment of the small subunit ribosomal gene revealed 100% identity to sequences obtained from rhesus macaques (Genbank accession AF023245) and human patients (Genbank accession AF024657 and L16868). CONCLUSIONS: These findings indicate that E bieneusi disseminates in immunodeficient macaques and may be a cause of peritonitis in the immunocompromised host.

Campylobacter-induced enteritis and diarrhea in captive cotton-top tamarins (Saguinus oedipus) during the first year of life.

A prospective study of 43 cotton-top tamarins, from infancy to 6 to 17 months of age, was conducted to determine the epidemiology of Campylobacter spp. infection. Nine infants followed for one year in an isolation unit, where attendants wore protective clothing, did not become infected. In the main facility where 32 of 34 animals had repeated infections with C. coli, 6% of the infections developed initially in incubators, 66% in the nursery room, and 28% after transfer to the main colony. Fifteen of these tamarins also were infected with C. jejuni. Twenty percent of the infections developed initially in the nursery room and 80% in the colony. Polyacrylamide gel electrophoresis analysis of C. jejuni cultures revealed multiple reinfections with different strains. Both types of infections were most prevalent between 3 and 9 months of age. Campylobacterjejuni infection developed most frequently between April and June and C. coli infection developed between October and December. In the nursery, diarrhea developed most frequently at times when there was no infection with Campylobacter spp. Forty percent of animals with diarrhea in the nursery had C. coli and none had C. jejuni, whereas, in the colony, 49% had C. jejuni and 11% had C. coli infections. There was no association between these infections and diet or idiopathic colitis.

Crossed renal ectopia in a squirrel monkey (Saimiri sciureus) and an owl monkey (Aotus trivirgatus).

A 5-year-old female squirrel monkey, Saimiri sciureus, died with a ceco-colonic infarct. An incidental finding was renal ectopia: The left kidney was located between the common iliac arteries posterior to the bifurcation of the aorta and to the right of the body midline. An adult owl monkey, Aotus trivirgatus, was killed in renal failure due to end-stage glomerulonephritis. Fused kidneys were located on the right side and posterior to the normal position. These are examples of crossed renal ectopia with and without fusion.

Colonic adenocarcinoma associated with chronic colitis in cotton top marmosets, Saguinus oedipus.

Colitis is a common disease of cotton top marmosets, Saguinus oedipus, characterized by crypt abscesses and inflammation of lamina propria. In more advanced colitis there is marked irregularity of mucosal surface, distortion of crypt architecture and epithelium, increased numbers of mitoses, and decreased numbers of goblet cells. Foci of pleomorphic cells arranged in poorly formed glands or sheets, interpreted as carcinoma in situ, also occur. Many such cases have invasive colonic adenocarcinoma with metastasis to colonic lymph nodes but not elsewhere. Analysis of necropsy data from a group of 210 marmosets in captivity for 3.5 yr revealed that the incidence of advanced colitis, adenocarcinoma in situ and invasive carcinoma increased markedly over that period. A strong association between colitis and adenocarcinoma was suggested by both morphologic and epidemiologic data.

Congenital anomalies in two neonatal tamarins (Saguinus oedipus and Saguinus fuscicollis).

Congenital anomalies were seen at necropsy of two neonatal tamarins. The defects included achondroplastic-like dwarfism, polydactyly and syndactyly in a Saguinus oedipus, and scoliosis and uterus didelphys in a S. fuscicollis. Both infants were the offspring of incestuous matings between twin siblings.

Eosinophilic myelocytoma in an owl monkey (Aotus trivirgatus).

A mass found in the anterior mediastinum at necropsy of an adult female owl monkey (Aotus trivirgatus) was morphologically consistent with an eosinophilic myelocytoma. Lymph nodes, kidneys, bone marrow, and other tissues were diffusely infiltrated by neoplastic cells. Intracellular and extracellular Charcot-Leyden crystals were present in the neoplasm.

Delineation of lymphocyte subsets in lymph nodes of nonhuman primates.

Monoclonal antibodies which recognize specific surface antigens on human lymphocytes were used with an avidin-biotin immunoperoxidase technique to stain lymph nodes from nonhuman primates. Cells in lymph nodes from three macaque species and two new-world primate species could be stained to define T11, T4, T8, and B1 lymphocyte subsets. This approach will facilitate the study of many important spontaneous and experimentally induced diseases of nonhuman primates.

Morphologic changes in lymph nodes of macaques with an immunodeficiency syndrome.

Lymph nodes from macaque monkeys with an immunodeficiency syndrome were examined by electron microscopy and both routine histologic and immunoperoxidase staining techniques, using monoclonal antibodies that recognize specific primate lymphocyte subsets. In the early stages of disease, marked follicular hyperplasia and a reduced paracortex comprised predominantly of T8-positive (suppressor/cytotoxic) cells were observed. In monkeys with more advanced disease, lymph nodes showed follicular involution and loss of B cells. Vasculature was seen prominently in the paracortex of these nodes; cellular elements included a mixture of small lymphocytes and larger cells, which by ultrastructural criteria appeared to be lymphoblasts. Lymph nodes in terminal stages of this disease showed a total effacement of architecture with a marked depletion of lymphocytes. These findings are remarkably similar to the lymph node changes seen in humans with acquired immune deficiency syndrome and underline the importance of this disease in macaques as a model for studying acquired immunodeficiency states.

Spontaneous infectious diseases of marmosets.

The various species of marmosets are susceptible to a wide variety of infectious agents of which only a few have been fully characterized. Little is known concerning spontaneous disease in their natural habitat, and often deaths in the laboratory go unexplained. In captivity, Herpesvirus-T infection appears to be the most important viral infection, but serious disease may also follow infection with measles virus (rubeola) and an unidentified paramyxovirus. Bacterial diseases are multiple, but rarely occur as epizootics. Various species of Salmonella, Yersinia, Klebsiella, and Diplococcus are among the more frequent pathogens. Mycoses and parasitic infections are also numerous, but most do not result in major losses.

A sparsely granulated, nonsecreting adenoma of the pars intermedia associated with galactorrhea in a male rhesus monkey (Macaca mulatta).

A pituitary mass was found at necropsy of a male Macaca mulatta. Hematoxylin and eosin-stained sections were consistent with a chromophobe adenoma. Ultrastructural examination revealed the tumor to be comprised predominantly of sparsely granulated cells. The tumor cells were negative for prolactin, somatotropin, adrenocorticotropin, luteinizing hormone, and thyrotropin by the peroxidase anti-peroxidase method. Other major lesions were gynecomastia and galactorrhea, testicular atrophy, ankylosing spondylitis, and amyloid deposition in the liver, spleen, adrenal, and intestinal tract.

Management and breeding of Aotus trivirgatus.

Attempts to establish successful breeding colonies of Aotus trivirgatus at this and other laboratories have largely been unsuccessful, resulting in only occasional pregnancies and a rare live birth. After the recognition of seven different karyotypes of owl monkeys, animals were paired on this basis and resulted in a marked increase in conceptions. From 1971 to 1975 only 10 pregnancies occurred but during 1975, there were 19 pregnancies. In addition to proper karyotyping, a period of acclimation and conditioning was required. Mean body measurements and weights of infants were established.

Suppression of simian immunodeficiency virus replication in vitro by CD8+ lymphocytes.

The AIDS-like disease in rhesus monkeys induced by the simian immunodeficiency virus (SIV) has been used as a model to explore the nature of the T lymphocyte response after infection with viruses of the human immunodeficiency virus family. Activated CD8+ lymphocytes are present in increased numbers in the paracortex of lymph nodes of SIV-infected rhesus monkeys with a lymphadenopathy syndrome. We demonstrate that SIV is more readily isolated from CD8+ lymphocyte-depleted PBL of SIV-infected animals than from their unfractionated PBL. Rather than reflecting the fact that the CD8+ lymphocyte-depleted cell populations are simply enriched for CD4+ lymphocytes, this indicates that CD8+ cells themselves are critical in this regulatory interaction. In fact, CD8+ lymphocytes from SIV-infected but not uninfected rhesus monkeys can block SIV replication in vitro in PBL populations. A T lymphocyte population that blocks replication of viruses of the HIV family may contribute to containing the progression of AIDS.

Nephritis and hemolytic anemia in owl monkeys (Aotus trivirgatus).

The two most common diseases of captive owl monkeys (Aotus trivirgatus) are hemolytic anemia and glomerulonephritis. The anemia is characterized by total red blood cell counts between 0.45 and 3.44 x 10(6) microliters, hemoglobin values as low as 1.0 g/dl, and many circulating nucleated red blood cells. Centrilobular necrosis in the liver, extramedullary hematopoiesis in liver and spleen, and hemoglobin casts in kidney tubules are prominent histologic features. Hemosiderin and lipofuscin often are found in liver, spleen, kidney and lymph nodes. Microthrombi and microinfarcts sometimes are scattered throughout the brain. Glomerular lesions in Aotus have been described previously and are characterized by increased numbers of mesangial cells and matrix, glomerulosclerosis and electron dense deposits in basement membranes. Lymphocytes, plasma cells and eosinophils frequently are present in the interstitium. In the early stages the cellular infiltrate is periglomerular. The foci then grow to encompass adjacent glomeruli and tubules. Finally, large portions of the kidney are affected and connective tissue proliferates. The incidence of extramedullary hematopoiesis in the liver correlated significantly with that of interstitial nephritis (0.001 less than p less than 0.01) but not with glomerular lesions. The two kidney lesions, glomerulonephritis and interstitial nephritis correlated strongly in incidence. They also found with equal frequency in 87 monkeys with clinical evidence of anemia. This analysis indicates that there may be no common pathogenesis of the hematologic and renal abnormalities as seen in certain autoimmune diseases. However, there could be complex interactions between two or more disease mechanisms that account for the various manifestations of disease.