T cell receptor V beta repertoire in an acute infection of rhesus monkeys with simian immunodeficiency viruses and a chimeric simian-human immunodeficiency virus.

Changes in T cell receptor (TCR) V beta repertoire and their correlation with virologic events were investigated in rhesus monkeys after acute infection with the simian immunodeficiency virus (SIV). 11 genetically defined rhesus monkeys were experimentally infected with SIVmac or a chimeric simian-human immunodeficiency virus (SHIV), and their peripheral blood lymphocytes (PBL) and lymph nodes were prospectively assessed for TCR V beta gene expression. PBL and lymph nodes of the acutely infected monkeys demonstrated an expansion of selected V beta-expressing T lymphocyte subpopulations as early as 3 d after infection. These expanded V beta-expressing lymphocyte subpopulations were comprised predominantly of CD8+ cells. Six of seven infected monkeys sharing a single electrophoretically defined major histocompatibility complex class I allele exhibited a similar expansion of V beta 14-expressing PBL. Sequence analyses of V-D-J segments of TCR-beta cDNA indicated that the V beta-expressing T cell subpopulation expansion can be oligoclonal. SIVmac-specific CD8+ cytotoxic T lymphocytes were demonstrated in both PBL and lymph nodes of the infected monkeys at the time expansion of the selected V beta-expressing cell subpopulations was seen. Finally, the expansion of the selected V beta-expressing lymphocytes in PBL coincided with the emergence and clearance of SIV p27 from the plasma of the infected monkeys. These results demonstrate that acute infection of rhesus monkeys with SIVmac or SHIV results in an expansion of CD8+ lymphocyte subpopulations expressing selected V beta gene families. The selectively expanded T lymphocytes may contribute to early viral clearance after acute SIVmac or SHIV infection.

An animal model for acute and persistent Epstein-Barr virus infection.

Epstein-Barr virus (EBV) is a human lymphocryptovirus that causes infectious mononucleosis, persists asymptomatically for life in nearly all adults, and is associated with the development of B cell lymphomas and nasopharyngeal carcinomas. A highly similar rhesus lymphocryptovirus naturally endemic in rhesus monkeys was used to orally infect naïve animals from a pathogen-free colony. This animal model reproduced key aspects of human EBV infection, including oral transmission, atypical lymphocytosis, lymphadenopathy, activation of CD23(+) peripheral blood B cells, sustained serologic responses to lytic and latent EBV antigens, latent infection in the peripheral blood, and virus persistence in oropharyngeal secretions. This system may be useful for studying the pathogenesis, prevention, and treatment of EBV infection and associated oncogenesis.

Experimental allergic encephalomyelitis in cynomolgus monkeys. Quantitation of T cell responses in peripheral blood.

Chronic relapsing-remitting experimental allergic encephalomyelitis (EAE) was induced in cynomolgus monkeys by a single immunization with a homogenate of human brain white matter (BH) in adjuvant. Proliferative T lymphocyte responses to BH, to myelin basic protein (MBP), but not to proteolipid protein, were detected in peripheral blood mononuclear cells (PBMC) of all animals and persisted until their death or, in surviving animals, for greater than 10 mo postimmunization. Responses of higher magnitude tended to be associated with fatal, compared with nonfatal, episodes of clinical EAE. The frequency of MBP-reactive T cells in PBMC of animals with acute EAE was quantitated with a soft agar colony system; the ratio of T cells that proliferated specifically to MBP was estimated at between 5 and 20 per 10(6) PBMC. A similar frequency of peptide-specific T cells was estimated from PBMC of monkeys immunized with a synthetic 14-mer peptide corresponding to a region near the carboxy terminus of MBP. Thus, autoantigen-reactive T cells can be detected in the circulation throughout the course of chronic EAE, are predictive of disease severity, and occur at a frequency similar to that estimated to be present in humans with multiple sclerosis.

In healthy primates, circulating autoreactive T cells mediate autoimmune disease.

A T cell response against myelin basic protein (MBP) is thought to contribute to the central nervous system (CNS) inflammation that occurs in the human demyelinating disease multiple sclerosis. To test whether MBP-reactive T cells that are normally retrieved from the circulation are capable of inducing CNS disease, MBP-reactive T cell clones were isolated from the peripheral blood of healthy, unimmunized Callithrix jacchus (C. jacchus) marmosets. This primate species is characterized by a natural chimerism of bone marrow elements between siblings that should make possible adoptive transfer of MBP-reactive T cells. We report that MBP-reactive T cell clones efficiently and reproducibly transfer CNS inflammatory disease between members of C. jacchus chimeric sets. The demyelination that is characteristic of experimental allergic encephalomyelitis induced in C. jacchus by immunization against human white matter did not occur after adoptive transfer of the MBP-reactive clones. It was noteworthy that encephalitogenic T cell clones were diverse in terms of their recognition of different epitopes of MBP, distinguishing the response in C. jacchus from that in some inbred rodents in which restricted recognition of MBP occurs. These findings are the first direct evidence that natural populations of circulating T cells directed against a CNS antigen can mediate an inflammatory autoimmune disease.

Prostatic adenocarcinoma with osseous metastases in a dog.

Bone scintigraphy was used to diagnose osseous metastasis of prostatic adenocarcinoma in a 10-year-old dog with neck pain and ataxia and a large, sensitive prostate gland. Although radiography revealed a normal spine, prostatic fluid cytologic and ultrasonographic findings were compatible with prostatitis or neoplasia. Scintigraphic hot spots were seen in the axial skeleton, ribs, pelvis, humerus, and femur and corresponded to sites of metastatic prostatic adenocarcinoma.

Anaesthetic management of baboons undergoing heterotopic porcine cardiac xenotransplantation.

A detailed anaesthetic technique for baboons (Papio anubis) undergoing heterotopic abdominal cardiac xenotransplantation is described. Twenty-two baboons served as transplant recipients. Donors were either crossbred farm pigs (Sus scrofa) (n = 4) or transgenic pigs (Sus scroefa) (n = 18) expressing human complement regulatory proteins on the endothelium. Intra-operative management was complicated by the physiological consequences of infrarenal. abdominal aortic cross-clamping, in addition to the immunological sequelae related to cross-species transplantation. In choosing anaesthetics for this procedure, we considered the need for maximal cardiac stability throughout a long surgical procedure that required abdominal aortic cross-clamping to facilitate the implantation of an oversized porcine cardiac graft. Baboons received a balanced anaesthetic consisting of inhaled isoflurane in oxygen, intravenous fentanyl and intravenous pancuronium. The pharmacological techniques employed were found to be safe and reliable and were well tolerated by our recipients without any significant side-effects.

Parental failure in captive cotton-top tamarins (Saguinus Oedipus).

Several New World monkey species experience high rates of infant mortality in captivity, and parental failure in the form of infant neglect and abuse is often regarded as one of the leading causes of this problem. We explored a large archival database to assess environmental, familial, and biological variables identified as significant for parental success in previous studies of captive tamarins, through several generations and across several dozen pedigrees. Using a stepwise multiple regression analysis we developed a model including the fewest variables able to identify statistically significant predictors of infant outcome. We found that seven independent variables could predict infant outcome in the colony. The most important appeared to be the presence of helpers with whom parents could share infant carrying. Mother's experience and litter size were two other variables that contributed to a significant extent to explaining parental failure. Moreover, the model showed that there is a measurable contribution to infant outcome due to the health status of both parents. Finally, we found a distinct role for mothers and fathers, and that parental failure follows different patterns for abuse and rejection.

A spontaneous squamous cell carcinoma of the oral cavity in a squirrel monkey (Saimiri sciureus)

A spontaneous squamous cell carcinoma was diagnosed in the oral cavity of an adult female squirrel monkey (Saimiri sciureus). Immunohistochemical analysis of the neoplasm demonstrated cytokeratin and vimentin, but not S100 or desmin in the neoplastic epithelial cells.

Cytotoxic T-lymphocyte responses to cytomegalovirus in normal and simian immunodeficiency virus-infected rhesus macaques.

Disseminated cytomegalovirus (CMV) infection is a frequent occurrence in human immunodeficiency virus-infected humans and in simian immunodeficiency virus (SIV)-infected rhesus macaques. Rhesus macaques are a suitable animal model with which to study in vivo interactions between CMV and AIDS-associated retroviruses. Since cytotoxic T lymphocytes (CTL) play a major role in control of viral infections, we have characterized CMV-specific CTL responses in SIV-infected and uninfected rhesus macaques. Autologous fibroblasts infected with rhesus CMV were used to stimulate freshly isolated peripheral blood mononuclear cells from CMV-seropositive animals. Following in vitro stimulation, specific CTL activity against CMV-infected autologous fibroblasts was detected in CMV-seropositive but not in CMV-seronegative normal macaques. CMV-specific CTL activity comparable to that in normal animals was also detected in two CMV-seropositive macaques infected with a live attenuated SIV strain (SIVdelta3) and in two of three macaques infected with pathogenic SIV strains. The CMV-specific CTL response was class I major histocompatibility complex restricted and mediated by CD8+ cells. An early CMV protein(s) was the dominant target recognized by bulk CTL, although the pattern of CTL recognition of CMV proteins varied among animals. Analysis of CMV-specific CTL responses in macaques should serve as a valuable model for CMV immunopathogenesis and will facilitate prospective in vivo studies of immune interactions between CMV and SIV in AIDS.

Disseminated B virus infection in a cynomolgus monkey.

A cynomolgus monkey (Macaca fascicularis) was euthanatized 1 week following dystocia because of severe peritonitis. Histologic examination revealed lesions characteristic of herpesvirus infection in lungs, liver, spleen, bone marrow, uterus, and adrenal gland, and on the serosal surface of intestines, pancreas, and reproductive tract. Immunohistochemical studies on liver and lungs revealed Herpes B-like antigens in the lesions. B virus was isolated from serum. As systemic B-virus infection was not diagnosed before death of the monkey, these findings underscore the need for universal precautions when handling blood, fluids, or tissues from macaques.

Active and passively induced experimental autoimmune encephalomyelitis in common marmosets: a new model for multiple sclerosis.

A chronic relapsing-remitting form of experimental autoimmune encephalomyelitis was induced in the common marmoset Callithrix jacchus following a single immunization with human white matter. Individual animals in this species are born as natural bone marrow chimeras, allowing transfer of functional T-cell populations between genetically distinct siblings. The acute disease was characterized clinically by mild neurological signs. Pathologically, the disease was characterized by perivascular mononuclear cell infiltrates, large foci of primary demyelination, and reactive astrogliosis. No animal displayed hemorrhagic-necrotic lesions or polymorphonuclear cell infiltrates characteristic of other acute forms of primate experimental autoimmune encephalomyelitis. A late spontaneous relapse occurred in each of 2 animals followed for 3 to 12 months subsequent to recovery from the acute attack. In these animals, chronic lesions consisted of mononuclear cell infiltrates within large sharply defined areas of demyelination and astrogliosis, and resembled active plaques of chronic multiple sclerosis. Proliferative responses to myelin basic protein but not to myelin proteolipid protein were present in peripheral blood lymphocytes of immunized animals. Furthermore, myelin basic protein-reactive T-cell lines derived from immunized donors induced clinical signs of experimental autoimmune encephalomyelitis when adoptively transferred into a sibling, indicating that myelin basic protein-reactive T cells can induce disease in this species. Because of its clinical and pathological similarity to human multiple sclerosis and the ability to adoptively transfer experimental autoimmune encephalomyelitis, this model system should prove useful in the analysis of the immunological mechanisms responsible for autoimmune demyelination in outbred primates.

Behavioral management of specific pathogen-free rhesus macaques: group formation, reproduction, and parental competence.

Breeding colonies of specific pathogen-free (SPF) rhesus macaques were established to eradicate the transmission of Herpesvirus simiae and several retroviruses in this species. Strategies to attain this goal included the combination of large numbers of monkeys into groups, the establishment of small unimale groups, and a program using animals that were temporarily socially restricted. All methods required the establishment of new social groups from unfamiliar animals. In using these methods, we encountered important behavioral questions related to the group formation process, as well as reproductive and parental competence. Age and prior social experience were important determinants of social and parental success. New multimale-multifemale SPF group formations were successful initially and involved the least aggression during the first breeding season when young females and older males were used. Formation of unimale groups was successful, even when males and females were of similar ages. Breeding competence did not seem to be affected by any of the SPF colony management procedures, but animals with restricted early social experience exhibited impaired parental competence when compared with animals with more social experience. Males were more sensitive to the effects of early social restriction than females. A variety of behavioral obstacles will be encountered when attempting to establish an SPF breeding colony by forming groups by use of these methods. Skilled behavioral management is necessary to surmount these obstacles and to achieve satisfactory social integration, reproduction, and parenting.

In vivo effects of a bacterial superantigen on macaque TCR repertoires.

A macaque model was employed to explore staphylococcal enterotoxin B (SEB) superantigen-driven T lymphocyte responses. The SEB-reactive Vbeta+ cell subpopulations demonstrated a striking tri-phase response in rhesus monkeys following an SEB challenge in vivo. The hyperacute down-regulation, seen as early as 2 h through 2 days after SEB injection, was characterized by a disappearance of the reactive Vbeta-restricted PBL subpopulations from the circulation and decreased expression of these cell subpopulations in lymphoid tissues. Following this, a dominant expansion of reactive Vbeta-expressing CD4+ cell subpopulations occurred in lymph nodes and spleens, whereas in the peripheral blood a preferential expansion of reactive Vbeta-expressing CD8+ cell subpopulations was seen. An exhaustion of this response was then seen, with a prolonged decrease in the number of the reactive Vbeta+ CD4+ lymphocyte subpopulations. Interestingly, monoclonal or oligoclonal dominance was seen in the reactive Vbeta+ cell subpopulations in the period of the transition from the polyclonal cellular expansion to the exhaustion of the response, suggesting that some Vbeta+ cell clones may be more resistant than others to superantigen-mediated depletion. These results indicate that in vivo SEB superantigen-mediated effect on lymphocyte subpopulations in macaques is complex, suggesting that profound dynamics in the TCR repertoires may in part account for the susceptibility of higher primates to SEB-induced diseases.

Mycobacterium bovis bacille Calmette-Guérin enhances pathogenicity of simian immunodeficiency virus infection and accelerates progression to AIDS in macaques: a role of persistent T cell activation in AIDS pathogenesis.

It has recently been proposed that Mycobacterium tuberculosis may enhance the pathogenicity of HIV infections and accelerate the course of HIV disease. This hypothesis has been tested in the present study using a simian immunodeficiency virus of macaques (SIVmac)/Mycobacterium bovis bacille Calmette-Guérin (BCG)-coinfected macaque model. Naive and chronically SIVmac-infected monkeys were evaluated. Following BCG inoculation, the SIVmac-infected monkeys exhibited the dominant responses of TCR-beta complementarity-determining region 3-restricted T cell subpopulations. This BCG-driven T cell activation correlated with a marked increase in viral loads in SIVmac-infected monkeys. Moreover, the prolonged T cell activation coincided with the enhanced decline of CD4+ PBL counts and the accelerated progression to clinical AIDS in the coinfected monkeys, suggesting that Mycobacterium-driven T cell activation may be the mechanism underlying the enhanced pathogenicity of AIDS virus infection in the coinfected individuals. Within 2 to 7 mo after BCG coinfection, all chronically SIVmac-infected monkeys died from SIV-induced AIDS including tuberculosis-like disease. Surprisingly, the naive monkeys manifested a T cell activation-related toxic shock syndrome and a profound depletion of CD4+ lymphocytes 2 wk after simultaneous SIVmac/BCG inoculation. These naive animals died 2 mo after SIVmac/BCG inoculation, with the evidence of the persistent SIV p27 antigenemia and SIVmac-induced disease. In contrast, the normal monkeys not infected with SIVmac survived BCG infection; the control SIVmac-infected animals showed a natural course of chronic SIV infection. Thus, results from this SIV/BCG coinfection model strongly support the hypothesis that active coinfection with HIV and Mycobacterium can impact remarkably on the AIDS virus-induced disease.

Use of human leukocyte-specific monoclonal antibodies for clinically immunophenotyping lymphocytes of rhesus monkeys.

The rhesus monkey (Macaca mulatta) is an important experimental animal frequently utilized for studies of infectious diseases, immunity, hematopoiesis, and transplantation. Since the structure of cell surface molecules is phylogenetically conserved, monoclonal antibodies raised against human leukocyte antigens can sometimes recognize the homologous determinant on monkey leukocytes. To facilitate better utilization of this animal model, we tested 89 commercially available monoclonal antibodies which define 27 human cell surface antigens for reactivity with rhesus monkey PBL. Certain antigens which delineate clinical useful lymphocyte subsets such as CD2, CD4, CD8, CD14, CD16, CD20, and MHC class II are apparently well conserved since most human cell-specific antibodies identified the homologous cell subset in monkeys. However, other antigens such as CD3, CD19, CD45, and CD56 were identified infrequently by human cell-specific antibodies. FITC-modification of antibodies which had no effect on their binding to human cells occasionally inhibited antibody binding to monkey cells. Nevertheless, an adequate number of cross-reactive monoclonal antibodies was identified to allow gating of lymphocytes for accurate flow cytometric analysis and quantitation of the major lymphocyte subsets of the rhesus monkey. The T lymphocyte subset distribution in blood and lymphoid tissue of rhesus monkeys was similar to man. However, the B subset was significantly larger in monkeys. The daily variation in absolute PBL subset size was marked and found to be due mainly to daily fluctuations in total lymphocyte number.

In vivo T-lymphocyte activation and transient reduction of viral replication in macaques infected with simian immunodeficiency virus.

While it is well established that cellular activation can increase human immunodeficiency virus (HIV) replication in T lymphocytes, it is also clear that both activated CD8+ and CD4+ T lymphocytes mediate anti-HIV activity. To assess the relative importance of these contrary effects on HIV replication in vivo, we evaluated the consequences of Mycobacterium bovis BCG and staphylococcal enterotoxin B (SEB) inoculation in vivo in rhesus monkeys chronically infected with simian immunodeficiency virus of macaques (SIVmac). BCG inoculation induced as much as a 2.5-log reduction of plasma and intracellular SIV RNA in SIVmac-infected monkeys. This down-regulation of virus replication persisted as long as 4 weeks after BCG inoculation. Similarly, SEB injection resulted in up to a 3-log decrease in plasma and intracellular SIV RNA in SIVmac-infected macaques. Interestingly, the short-term reduction of viremia in these monkeys correlated with the peak in vivo production of SEB- and BCG-induced cytokine responses. However, no long-term clinical benefit was observed in the SIVmac-infected macaques. These studies provide in vivo evidence that potent T-cell stimulation driven by antigens other than the virus itself can, under some circumstances, mediate short-term reduction of viremia in AIDS virus-infected individuals.

An acutely lethal simian immunodeficiency virus stimulates expansion of V beta 7- and V beta 14-expressing T lymphocytes.

SIVsmmPBj14, a variant simian immunodeficiency virus isolated from a pig-tailed macaque, stimulates the proliferation of macaque T lymphocytes in vitro and induces an acutely lethal disease in macaques characterized, in part, by lymphadenopathy and splenomegaly. To determine whether SIVsmmPBj14 exhibits superantigen-like activity, in vitro and in vivo studies of T-cell receptor V beta repertoire were undertaken using PCR-based quantitative methods. Whereas in vitro phytohemagglutinin stimulation of macaque peripheral blood lymphocytes did not cause a perturbation of T-cell receptor V beta repertoire, SIVsmmPBj14 stimulated the expansion of both CD4+ and CD8+ T-lymphocyte subpopulations expressing the V beta 7 and V beta 14 gene families. Such V beta 7 and V beta 14 expansions could be confirmed by a multiple RNase protection assay. Furthermore, the expansion of the same lymphocyte subpopulations was also detected in peripheral blood lymphocytes and lymph node cells of virus-infected macaques. These observations suggest that SIVsmmPBj14-mediated V beta expansion may contribute to the induction of an acutely lethal disease in macaques.

An env gene derived from a primary human immunodeficiency virus type 1 isolate confers high in vivo replicative capacity to a chimeric simian/human immunodeficiency virus in rhesus monkeys.

To explore the roles played by specific human immunodeficiency virus type 1 (HIV-1) genes in determining the in vivo replicative capacity of AIDS viruses, we have examined the replication kinetics and virus-specific immune responses in rhesus monkeys following infection with two chimeric simian/human immunodeficiency viruses (SHIVs). These viruses were composed of simian immunodeficiency virus SIVmac239 expressing HIV-1 env and the associated auxiliary HIV-1 genes tat, vpu, and rep. Virus replication was assessed during primary infection of rhesus monkeys by measuring plasma SIVmac p27 levels and by quantifying virus replication in lymph nodes using in situ hybridization. SHIV-HXBc2, which expresses the HIV-1 env of a T-cell-tropic, laboratory-adapted strain of HIV-1 (HXBc2), replicated well in rhesus monkey peripheral blood leukocytes (PBL) in vitro but replicated only to low levels when inoculated in rhesus monkeys. In contrast, SHIV-89.6 was constructed with the HIV-1 env gene of a T-cell- and macrophage-tropic clone of a patient isolate of HIV-1 (89.6). This virus replicated to a lower level in monkey PBL in vitro but replicated to a higher degree in monkeys during primary infection. Moreover, monkeys infected with SHIV-89.6 developed an inversion in the PBL CD4/CD8 ratio coincident with the clearance of primary viremia. The differences in the in vivo consequences of infection by these two SHIVs could not be explained by differences in the immune responses elicited by these viruses, since infected animals had comparable type-specific neutralizing antibody titers, proliferative responses to recombinant HIV-1 gp120, and virus-specific cytolytic effector T-cell responses. With the demonstration that a chimeric SHIV can replicate to high levels during primary infection in rhesus monkeys, this model can now be used to define genetic determinants of HIV-1 pathogenicity.