Flow microfluorometric analysis of peripheral blood mononuclear cells from nonhuman primates: Correlation of phenotype with immune function

Immunohematological features of free-living Alouatta belzebul (Linnaeus, 1766) red-handed howler monkeys in the Eastern Amazon

The red-handed howler monkey (Alouatta belzebul) is one of the 35 threatened Brazilian primate species found in two highly endangered Brazilian biomes. Their Amazonian native populations have been declining due to exponential deforestation associated with human activities, especially the construction of dams. The studied population (n = 27) was located in the Belo Monte dam Area of Influence. For the first time, we presented hematological parameters and the basic profile of T (CD3) and B (BSAP PAX5) cells by immunocytochemistry. The results supported the hypothesis that the immuno-hematological profile is influenced by sex, age, and season. Eosinophils were significantly higher in females (p = 0.03), monocytes statistically greater in juveniles (p = 0.04), and total plasma protein increased significantly (p > 0.001) during the dry season. Furthermore, adults showed a statistically higher average absolute number of B lymphocytes than young individuals (p = 0.03), in contrast to T lymphocytes. Even without knowing the full history of antigenic exposure, these results not only contribute to elucidating the boundaries between health and disease but may help lay the groundwork for future research into the effects of anthropogenic stress on immune activation.

Immunological Responses to Injury and Grafting in the Central Nervous System of Nonhuman Primates

Allogeneic transplantation for the therapy of human Parkinson's disease is being considered as a viable approach at several clinical centers worldwide. As an attempt to understand the basic biology of central nervous system (CNS) transplantation, our laboratory has developed an experimental nonhuman primate model for human Parkinson's disease and carried out preliminary studies directed at evaluating the potential pathology at the graft site. In addition, studies have been conducted to examine whether such transplantation procedures lead to specific and/or nonspecific immunologic sensitization of the host or results in generalized immunosuppression. Groups of rhesus macaques (Macaca mulatta) were either controls operated (n = 6), autografted with adrenal medullary and peripheral nerve tissue (n = 3), or allografted with fetal mesencephalic tissue (n = 6). Immunohistological studies demonstrated the presence of mononuclear cell infiltrates as early as 1 wk and up to 1 yr postoperatively, although the frequency of the infiltrating cells declined with time. The infiltrates consisted of variable numbers of cells which express CD2+, CD3+, CD4+, CD8+, CD19+, CD22+, CD25+, and CD68+. There appeared to be no difference in the frequency, kinetics, or phenotype of the infiltrating cells in operative controls compared with recipients of auto- or allografts. Tissue sections obtained postoperatively showed low levels of major histocompatibility complex (MHC) Class I antigens and no detectable level of MHC-Class II antigens in neural tissue. A small aliquot of tissue from the operative site was placed in vitro with media containing interleukin-2 (IL-2), which led to the exudation and growth of mononuclear cells that were predominantly CD4+ cells. Phenotypic studies of peripheral blood mononuclear cells (PBMC) from operative controls, auto- and allograft recipient monkeys performed at varying time periods postoperatively failed to show differences in the frequencies of subsets of T-cells, B-cells, NK-cells, or monocytes. Studies on aliquots of the same PBMC failed to show major functional differences in NK-cells, LAK cells, or response to polyclonal mitogens. Finally, recipients of allogeneic mesencephalic grafts failed to show evidence of donor-specific humoral or cellular sensitization. These data indicate that transplantation of autograft adrenal or allograft fetal mesencephalic tissues in the CNS of nonhuman primate did not induce detectable donor-specific sensitization nor nonspecific immunosuppression.

Delineation of multiple subpopulations of natural killer cells in rhesus macaques

Natural killer (NK) cells in rhesus macaques have been variably defined as CD3- CD16+ or CD3- CD8+, although only limited efforts have been made to validate these definitions rigorously. To better understand the role of NK cells in macaque disease models, we undertook a multiparameter analysis of macaque NK cells employing four-colour flow cytometry and a panel of lineage-specific and non-lineage-specific lymphocyte markers. Using this approach, we identified two distinct populations of candidate NK cells: a major CD8bright CD16+ population and a minor CD8bright CD16- population. Further analysis of the major and minor NK cell populations revealed the expression of multiple markers characteristic of NK cells, including CD2, CD7, CD16, CD161, NKG2A and granzyme B. In addition, a CD56+ subset of cells within the minor rhesus NK population was identified which expressed chemokine and lymph node homing receptors similar to those expressed by the CD56bright NK cell population identified in humans. Cytolytic assays confirmed that the phenotypically defined rhesus NK cells lysed NK-susceptible target cells. Our observations support the existence of several distinct subpopulations of rhesus macaque NK cells, which have significant phenotypic and functional similarities to their human counterparts. These improved immunophenotypic definitions of macaque NK cells should facilitate future analysis of innate immune responses in rhesus macaques and the role of NK cells in AIDS pathogenesis in Simian immunodeficiency virus (SIV)-infected macaques.

Evidence for antibody-mediated enhancement of simian immunodeficiency virus (SIV) Gag antigen processing and cross presentation in SIV-infected rhesus macaques

By using the dominant simian immunodeficiency virus (SIV) Gag Mamu-A01 restricted major histocompatibility complex (MHC) class I epitope p11CM, we demonstrate antibody-mediated enhanced MHC class I cross presentation of SIV Gag. In vitro restimulation of peripheral blood mononuclear cells from SIV-infected rhesus macaques with recombinant full-length SIV Gag p55 plus p55 affinity-purified immunoglobulin G (p55 Gag/p55-IgG) led to the generation of markedly higher frequencies of p11CM specific precursor cytotoxic T lymphocytes (p-CTLs) compared with restimulation with (i) SIV Gag p55 alone or (ii) optimal concentrations of the p11CM peptide alone. These results, along with the finding that CD4 depletion abrogated the enhancement, suggest a prominent role for CD4(+) T cells. Testing for p-CTLs against other Mamu-A01-restricted SIV Gag epitopes suggested that this mechanism favored recognition of the dominant p11CM peptide, potentially further skewing of the CTL response. The p-CTL enhancing effect was also decreased or abrogated by pepsin digestion of the p55-specific IgG or by the addition of monoclonal antibodies to Fc receptor (FcR) II/III, suggesting that the effect was dependent on FcR-mediated uptake of the immune-complexed antigen. Finally, incubation of antigen-presenting cells with SIV Gag p55 immune complexes in the presence of lactacystin or of bafilomycin indicated that the mechanism of antibody-mediated enhancement of cross presentation required both the proteasomal and the endosomal pathways. These data demonstrate for the first time the cross presentation of antigens via immune complexes in lentiviral infection and indicate a heretofore-unrecognized role for antibodies in modulating the magnitude and potentially also the breadth of MHC class I-restricted antigen processing and presentation and CTL responses.

Effects of morphine on T-cell recirculation in rhesus monkeys

A 2-yr study on effects of morphine on lymphocyte circulation in rhesus monkeys (Macaca mulatta) showed that, over time, a well-maintained morphine-dependency caused biphasic depressive effects on circulating lymphocyte levels. Depression of T cell circulation by opiates actually was a relative effect. Morphine exposure basically stabilized T cell circulation in the context of concurrent increases in controls. Biphasic effects of morphine were attributable to distinctions in circulation kinetics of CD4+/CD62L (+ & -) T cells. That is, levels of CD4+/CD62L+ T cells were selectively depressed by opiates through the first 32wk after initiation of drug, and levels of CD4+/CD62L- T cells were selectively depressed thereafter. Regression analyses also showed that morphine stabilized lymphocyte recirculation. Circulating levels of resting and activated-memory types of T cells were positively correlated in opiate-exposed monkeys during the first 32wk after opiate exposure--an effect not seen with control monkeys. Considerations of changes in the types of experimental stressors extant during the study suggested that temporally differential effects of opiates on T cell recirculation were connected with changes in the stress environment and the ability of morphine to modulate these changes. Thus, morphine, and by inference the endogenous opioid system, are involved in homeostasis of lymphocyte recirculation, probably through effects on central mediation of the stress axis.

Neutralizing antibodies as a potential secondary protective mechanism during chronic SHIV infection in CD8+ T-cell-depleted macaques

OBJECTIVE

To directly examine the role of CD8+ T cells in controlling viremia and disease during chronic, low-level primate immunodeficiency virus infection in DNA prime/protein boost-vaccinated macaques.

BACKGROUND

A cohort of macaques, vaccinated with either a DNA prime/HIV-1 gp160 boost regimen or with gp160 alone was previously protected partially from sequential challenges with non-pathogenic and pathogenic strains of chimeric simian/human immunodeficiency virus (SHIV). In this study, the effect of temporary ablation of CD8+ T cells in these animals was examined.

METHODS

Animals were treated with an anti-CD8 antibody and CD8+ T-cell levels in peripheral blood, plasma viral loads, peripheral blood mononuclear cell-associated virus levels, neutralizing antibody (nAb) titers and simian immunodeficiency virus Gag-specific CD8+ T-cell numbers were followed.

RESULTS

Plasma viremia rose sharply in direct synchrony with a rapid but transient drop in CD8+ T cells. However, although levels of cell-associated virus also rose concomitantly, peak levels were much lower than those in virus-challenged, naive animals. In addition, despite a rise of pathogenic SHIV89.6P RNA levels in three animals, CD4+ T-cell counts remained unchanged. In each of these animals, neutralizing antibody titers against the pathogenic SHIV89.6P strain were high.

CONCLUSIONS

The results indicate that CD8+ T cells play a key role in suppressing viremia in a chronically infected host. In addition, the results suggest that in the absence of CD8+ T cells, nAb may act as an effective second line of defense by limiting both the spread of infectious virus to new target cells and CD4+ T-cell loss.

Induction of long-term protective effects against heterologous challenge in SIVhu-infected macaques

A group of three rhesus macaques were inoculated with SIV isolated from a human (SIVhu) accidentally exposed and infected with SIVsm. Extensive sequence analyses of SIVhu obtained from the human and macaques following infection indicated the presence of truncated nef. Not only did nef fail to repair itself in vivo postinfection (p.i.), but instead, further mutations added additional stop codons with increasing time p.i. Infection of these animals was associated with minimal acute viral replication, followed by undetectable plasma viral loads and only intermittent PCR detection up to 5 years p.i. The three SIVhu infected and three control monkeys were then challenged with the heterologous highly pathogenic SHIV89.6p. All three controls became infected and showed rapid declines in peripheral CD4(+) lymphocytes, disease, and death at 10 and 32 weeks p.i., respectively. In contrast, all three animals previously infected with SIVhu are healthy and exhibit stable CD4(+) lymphocyte levels and undetectable plasma viral loads at >20 months post-SHIV89. 6p challenge. Only transient, low levels of SHIV replication were noted in these animals. Whereas responses to SIVgag/pol were noted, no evidence for SIV/SHIV envelope cross-reactivity was detected by antibody or CTL analyses, suggesting that the protective immune mechanisms to the heterologous challenge isolate were most likely not directed to envelope but rather to other viral determinants.

Trait-like immunological and hematological measures in female rhesus across varied environmental conditions

In this 2-year longitudinal study, 45 2-year-old female rhesus were observed as they were captured and removed from a free-ranging setting (Phase I), single caged for 1 year (Phase II), and housed in small, stable social groups for an additional year (Phase III). During the study, eight blood samples were taken, and hematological, immunological, and hormonal variables were assayed to determine whether 1) any of the measures would exhibit trait-like, inter-individual longitudinal stability, despite fluctuations in population means induced by Phases I, II, and III; 2) plasma concentrations of cortisol, prolactin, and norepinephrine would be lowest in Phase III, and elevated during the periods of acute and chronic stress associated with Phases I and II; and 3) there would be any evidence of immunosuppression associated with Phases I and II. The results suggest that the majority of hematological/immunological variables were trait-like throughout the study in contrast to plasma cortisol, prolactin, and norepinephrine concentrations. Thus, red blood cells, hemoglobin, hematocrit, platelets, mean corpuscular volume and hemoglobin, as well as white blood cells, the absolute number of CD4+ (T-helper/inducer) cells, the absolute number of CD8+ (T-suppressor/cytotoxic) cells, total T cells (CD2+%), total B cells (CD20+%), and the ratio of CD4+/CD8+ cells were trait-like. The hematological measures were changed dramatically by capture and the subsequent single caging, with most not recovering to presumed baselines until after 12-28 weeks. The immune measures were depressed at capture (excepting B cells), and during 7 months of single caging failed to return to normal levels associated with social housing. We thus conclude that single housing can produce significant, long-term features of immunosuppression. Capture produced significant increases in plasma cortisol, prolactin, and norepinephrine concentrations. Long periods of single caging produced significant increases in plasma prolactin concentrations, indicative of stress-induced anxiety, and may also have been associated with down-regulation of plasma norepinephrine and cortisol concentrations.

Importance of the CD3 marker for evaluating changes in rhesus macaque CD4/CD8 T-cell ratios

BACKGROUND

Until recently, there were no CD3 antibodies that crossreacted with rhesus macaque T cells. Consequently, studies relying on CD8 counts or CD4/CD8 ratios enumerated this subpopulation on the basis of CD8+ or CD8bright+ staining. We used a rhesus-specific, anti-CD3 antibody to better define the CD8+ T-cell population, and to show the effects of better measurements on CD4/CD8 ratios and changes in T cells as macaques age.

METHODS

We used three-color flow cytometry to measure CD4 and CD8 populations with and without CD3 costaining. Venous blood samples were obtained from 52 colony-bred macaques between 2 months and 9 years of age.

RESULTS

The CD8+ T cells defined by CD3 and CD8 double staining were approximately 60% of all cells that were stained by CD8 alone. Improved detection of this lymphocyte subset showed that CD4/CD8 ratios were close to the range of 1.5-2.0. Declining CD4/CD8 ratios during aging are predominantly due to decreasing CD4+ T-cell counts.

CONCLUSIONS

Better quantitation of the CD8+ T-cell population showed that the CD4/CD8 ratio was not inverted as had been reported, but is actually very similar to the values observed in human beings. Although the two species differ in the pattern of CD8 expression, the general immune system characteristics are very similar.

Immunogenicity and safety of Mycobacterium tuberculosis culture filtrate proteins in non-human primates

The development of improved vaccines is considered a high priority in the effort to control tuberculosis (TB) world wide. Results from several studies performed in relevant animal models have demonstrated that Mycobacterium tuberculosis secreted antigens may represent major components of improved TB vaccines. To characterize further the M. tuberculosis secreted antigens as they relate to specific features important for vaccine development, rhesus macaques were immunized with either one of two different preparations containing M. tuberculosis culture filtrate (CF) proteins. These preparations differed in relative protein content and in the presence or absence of lipoarabinomannan. Animals received a total of three monthly intramuscular injections consisting of CF proteins resuspended in RIBI adjuvant and were tested for development of specific antibody and cellular proliferative responses. In addition, all animals were constantly monitored for local and systemic reactions as well as for the development of DTH reactions to intradermal tuberculin injection. Results from this study show that the two CF preparations are relatively safe and immunogenic in non-human primates. These two CF preparations differed in their ability to induce specific antibody responses, but were comparable in their ability to induce specific cellular proliferative responses. Induction of both humoral and cellular responses occurred even in presence of pre-existing antibodies directed against M. tuberculosis antigens. However, these responses appeared to be short-lived. Only one of the four animals produced interferon-gamma (IFN-gamma) in response to immunization with CF proteins. No DTH reaction to intradermal tuberculin injection was observed in any immunized animal. Although it is clear that additional studies are required to design strategies for the improvement of the immunogenicity of CF proteins, our observations support the currently accepted view that secreted protein-based preparations may represent promising vaccine candidates for TB.

Simian immunodeficiency virus (SIV) from sun-tailed monkeys (Cercopithecus solatus): evidence for host-dependent evolution of SIV within the C. lhoesti superspecies

Recently we reported the characterization of simian immunodeficiency virus (SIVlhoest) from a central African l'hoest monkey (Cercopithecus lhoesti lhoesti) that revealed a distant relationship to SIV isolated from a mandrill (SIVmnd). The present report describes a novel SIV (SIVsun) isolated from a healthy, wild-caught sun-tailed monkey (Cercopithecus lhoesti solatus), another member of the l'hoest superspecies. SIVsun replicated in a variety of human T-cell lines and in peripheral blood mononuclear cells of macaques (Macaca spp.) and patas monkeys (Erythrocebus patas). A full-length infectious clone of SIVsun was derived, and genetic analysis revealed that SIVsun was most closely related to SIVlhoest, with an amino acid identity of 71% in Gag, 73% in Pol, and 67% in Env. This degree of similarity is reminiscent of that observed between SIVagm isolates from vervet, grivet, and tantalus species of African green monkeys. The close relationship between SIVsun and SIVlhoest, despite their geographically distinct habitats, is consistent with evolution from a common ancestor, providing further evidence for the ancient nature of the primate lentivirus family. In addition, this observation leads us to suggest that the SIVmnd lineage should be designated the SIVlhoest lineage.

CD40 ligation induced phenotypic and functional expression of CD80 by human cardiac microvascular endothelial cells

BACKGROUND

CD40/CD40L (gp39) interactions are known to play a central role in the function of the immune system (1). CD40 is constitutively expressed on professional antigen presenting cells, such as macrophages and dendritic cells, as well as at low levels on other cell lineages, including human umbilical vein endothelial cells (HUVECs). On antigen-presenting cells, ligation of CD40 causes expression of the costimulatory molecule CD80 (B7-1). Similar ligation of CD40 on HUVECs, however, leads to up-regulation of the adhesion molecules VCAM-1, ICAM-1, and E-selectin, but not CD80.

METHODS

In efforts to provide evidence that microvascular endothelial cells (MECs) are distinct from HUVECs and that the distinguishing features play a role in allograft rejection, MEC cultures were prepared from the explanted hearts of human heart transplant recipients and primary cell lines were established. These MECs were induced to express higher levels of CD40 with interferon-gamma pretreatment, co-cultured with CD40L-transfected HeLa cells, and fluorescence-activated cell sorter-assisted phenotypic studies, in addition to functional allogeneic mixed lymphocyte reaction and accessory-cell dependent mitogen induced proliferation assays were performed.

RESULTS

CD40-CD40L interactions induced the expression of the adhesion molecules VCAM-1 and E-selectin and the costimulatory molecule CD80 but not CD86 (B7-2) on the MECs. The expressed CD80 proved functional in both allo-MLR assays and accessory-cell dependent mitogen proliferation assays.

CONCLUSIONS

MECs are distinct from HUVECs by their potential to express VCAM-1 after interferon-gamma pretreatment and CD80 after CD40 ligation, properties which enable this cell lineage to play a central role in initiating and maintaining allograft rejection in human cardiac transplants.

A preliminary description of responses of free-ranging rhesus monkeys to brief capture experiences: behavior, endocrine, immune, and health relationships

A cohort of free-ranging rhesus monkeys has been followed since birth in 1994 on the island of Cayo Santiago, Puerto Rico. At 3 years of age, subjects were trapped and blood samples were collected after capture and prior to release the following day. Blood samples were processed for natural cytotoxicity toward xenogeneic tumors, phenotyping, and plasma hormones. Intestinal parasites were determined from fresh stool samples collected during trapping. Data were also available from the previous year for antibody titers to latent viruses prevalent in this population. Behavioral traits of each monkey were characterized using a previously developed trait scale for rhesus monkeys. Natural cytotoxicity toward both K562 and Raji targets declined from capture until release the following day. Plasma cortisol rose and plasma prolactin and growth hormone fell during the period of captivity; a rise in insulin was significant. It was expected that individual differences in behavioral traits might predict immune and hormone levels at the time of capture or changes in these parameters during the capture period. Although behavioral adjectives tended to cluster along three orthogonal dimensions (Insecurity, Irritability, and Sociability), they bore no relationship to the physiological parameters collected acutely (in vitro immune and endocrine parameters). The individual difference markers of gender and maternal rank were not related to the magnitude of the observed changes in these in vitro parameters, either. However, an in vivo measure (CMV titer) was related to individual differences in Irritability. It was concluded that the magnitude of the stress associated with capture overwhelmed the individual difference effects.

Cross-species reactivity of a panel of antibodies with monkey and porcine tissue

The continuing shortage of organs available for transplantation limits the number of patients able to benefit from this highly successful form of therapy. Interest in alternative sources of organs has now turned towards the pig because of its physiological similarity to human. There is a requirement therefore for reagents not only for research purposes but possibly for studying xenotransplants in the clinical situation in the future. In this study, we have concentrated on determining the cross-species reactivity of a large panel of antibodies directed against human leukocyte markers, testing peripheral blood leukocytes and also including renal tissue to determine non-leukocyte cross-reactivity. A total of 63 out of 127 antibodies cross-reacted with cynomolgus monkey cells. Twenty of these antibodies stained similar populations of leukocytes to human, whereas the remaining 43 reacted with clearly different populations. The majority of antibodies (108/127) were unreactive with porcine leukocytes, reflecting the evolutionary differences between pig and man. Of the 19 antibodies cross-reactive with porcine cells, seven reacted with similar proportions of leukocytes to human, whereas the remaining 12 antibodies stained entirely different populations. The most interesting, and potentially most useful, antibodies were four that reacted with human, cynomolgus monkey and porcine tissue in a similar manner, suggesting that the epitopes recognized are present on similar molecules. These antibodies were directed against CD29 (MEM1O1A, K20) and CD18 (BU87, 7E4), the common beta1- and beta2-integrin subunits respectively. This study demonstrates that there are antigens common to cynomolgus monkey, pig and man that react with currently available antibodies. Nevertheless, when determining cross-species reactivity of human antibodies, it is important to consider the possibility that there may be additional non-leukocyte reactivity in other tissues.

Diverse host responses and outcomes following simian immunodeficiency virus SIVmac239 infection in sooty mangabeys and rhesus macaques

Sooty mangabeys naturally infected with simian immunodeficiency virus (SIV) do not develop immunodeficiency despite the presence of viral loads of 10(5) to 10(7) RNA copies/ml. To investigate the basis of apathogenic SIV infection in sooty mangabeys, three sooty mangabeys and three rhesus macaques were inoculated intravenously with SIVmac239 and evaluated longitudinally for 1 year. SIVmac239 infection of sooty mangabeys resulted in 2- to 4-log-lower viral loads than in macaques and did not reproduce the high viral loads observed in natural SIVsmm infection. During acute SIV infection, polyclonal cytotoxic T-lymphocyte (CTL) activity coincident with decline in peak plasma viremia was observed in both macaques and mangabeys; 8 to 20 weeks later, CTL activity declined in the macaques but was sustained and broadly directed in the mangabeys. Neutralizing antibodies to SIVmac239 were detected in the macaques but not the mangabeys. Differences in expression of CD38 on CD8(+) T lymphocytes or in the percentage of naive phenotype T cells expressing CD45RA and CD62L-selection did not correlate with development of AIDS in rhesus macaques. In macaques, the proportion of CD4(+) T lymphocytes expressing CD25 declined during SIV infection, while in mangabeys, CD25-expressing CD4(+) T lymphocytes increased. Longitudinal evaluation of cytokine secretion by flow cytometric analysis of unstimulated lymphocytes revealed elevation of interleukin-2 and gamma interferon in a macaque and only interleukin-10 in a concurrently infected mangabey during acute SIV infection. Differences in host responses following experimental SIVmac239 infection may be associated with the divergent outcome in sooty mangabeys and rhesus macaques.

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.

Development of an animal model for autotransfusion therapy: in vitro characterization and analysis of anti-CD3/CD28 expanded cells

Previous studies have shown that in vitro culture of human CD4+ T cells with antibodies to CD3 and CD28 immobilized on beads induced an antiviral effect to HIV-1 infection. Herein, we have used CD4+ T cells from nonhuman primates to address issues critical for use of such cells for therapy and immune reconstitution of humans and nonhuman primates infected with HIV and simian immunovirus (SIV). These studies include definition of the kinetics of the antiviral effect, the relative stability of the acquired phenotype, and whether such activated and expanded CD4+ T cells retain their immune function. Results of our studies show that antiviral effect is induced rapidly following activation with anti-CD3/CD28-coated beads. Additionally, the antiviral effect is not stable in these cells and requires continuous culture with anti-CD3/CD28 beads. Removal of CD4+ T cells from anti-CD3/CD28 stimulation renders these cells susceptible to infection, demonstrating that the resistant phenotype is not stable in these cultures. However, anti-CD3/CD28 expanded CD4+ T cells do retain immune function. Thus, although these findings imply a note of caution for therapeutic strategies aimed at providing patients with virus-resistant CD4+ T cells, the present study suggests that transfusion of such cells with retained immune function may have immune restoration capability.

Experimental studies on immunosuppression: how do they predict for man?

The ultimate goal of any animal model in immunotoxicity testing is that it be a sensitive predictor of xenobiotic-induced immune dysfunction in humans. Such models should be capable of identifying the target(s) within the immune system affected by the xenobiotic. In particular the tier testing models have been successfully used to identify and characterize a variety of different immunotoxicants in animals as it pertains to immunosuppression and reduced resistance to infectious diseases. These tier models in mice and rats have been validated in interlaboratory studies. Although these protocols were designed for studies of rats and mice, some have been applied successfully for studying immunotoxicity in other animal species, including non-human primates. A great amount of data has been generated by the application of these models, which demonstrate that xenobiotics alter the immune system of animals. In man, the database on chemical-induced immunosuppression is limited, as the use of markers of immunotoxicity has received little attention in clinical and epidemiological studies. Such studies have not been performed frequently, and their interpretation often does not permit unequivocal conclusions to be drawn, due for instance to the presence of confounding factors and the uncontrolled nature of exposure. Also, testing possibilities in humans are limited and immune function changes by chemical exposure are often subtle. In humans, a number of agents have been shown to have immunosuppressive properties (including PCBs, PCDDs, PCDFs, oxidant gases, and ultraviolet radiation), but the strongest evidence stems from the clinical use of immunosuppressant drugs in transplant patients. These human data do in general terms confirm the data gained with experimental animals. Immunotoxicity assessment in rodents therefore adequately forms the basis for human risk assessment. Knowledge on the predictability of these animal models and immune assays can be further improved by comparison of the human and animal data obtained in the development of drugs.

Effect of neonatal treatment with a gonadotropin releasing hormone antagonist on developmental changes in circulating lymphocyte subsets: a longitudinal study in male rhesus monkeys

We have examined changes in circulating lymphocyte subsets from the neonatal period until adulthood (4 months until 5.5 years of age) in male rhesus monkeys, and the impact of neonatal treatment with a GnRH antagonist (Ant) or Ant and androgen (Ant/And) on these parameters. Absolute numbers of lymphocytes, B cells, total T lymphocytes, and CD4+ T cells decreased, neutrophils increased, and CD8+ T cells did not change with age. WBC counts increased between 4 mo and 2 years of age and then fell to neonatal levels over the next two years. The decline of CD4 + T cells in association with stable CD8+ T cell levels resulted in an age-related decrease in the CD4+/CD8+ T cell ratio. At 4 months of age, WBC's, lymphocytes, total T cells, CD8+ T cells and B cells were lower in Ant- and Ant/And-treated animals compared to controls. With the exception of WBC counts, these values had normalized by 2 years of age. Reduced WBC levels in treated animals persisted through adulthood. CD4+ T cell levels tended to be lower in Ant-treated and higher in Ant/And-treated animals than in controls at 4 months of age. CD4+ T cells remained lower in Ant- than in Ant/And-treated animals at most ages. The higher CD4 + T cell counts in Ant/And-treated animals resulted in an elevated CD4 + /CD8 + T cell ratio that persisted until the onset of year 5. During years 5 and 6, seasonal fluctuations in WBC's and neutrophils were observed with counts being higher in the breeding (fall) than in the nonbreeding (summer) season. The data document that developmental changes in circulating immune cells in the rhesus monkey are qualitatively similar to those reported in humans, and provide further evidence that neonatal treatment of male rhesus monkeys with Ant or Ant/And may alter early programming of the immune system.

Simian immunodeficiency virus of African green monkeys is apathogenic in the newborn natural host

Several studies have demonstrated that newborn animals are more susceptible to disease development following infection with retroviruses than adults. Adult African green monkeys (AGMs) infected with SIVagm do not develop AIDS-like disease and the objective of the study was to determine whether experimental infection of newborn AGMs with SIVagm would result in pathogenesis. Neonatal AGMs were found to have a higher percentage of circulating CD4+ lymphocytes than adults (62% versus 14%) and therefore a higher potential pool of target cells for SIVagm infection. However, no differences in the in vitro replication kinetics of SIVagm in peripheral blood mononuclear cells of adult or neonatal AGMs could be observed. In vivo, the neonatal AGMs became viremic at the earliest two months after inoculation whereas the adult AGMs had evidence of virus replication already 2 to 6 weeks after infection. None of the animals developed AIDS-like symptoms upon infection. In the heterologous cynomolgus macaque host, a newborn infected with SIVagm developed early high virus loads and died two months after birth with AIDS-like histopathologic features. It would therefore appear that in contrast to the situation with many other retroviruses, newborn AGMs are no more permissive to SIVagm infection than are adults.

The tyrosine-17 residue of Nef in SIVsmmPBj14 is required for acute pathogenesis and contributes to replication in macrophages

The variant simian immunodeficiency virus termed SIVsmmPBj14 induces a rapidly fatal disease in pig-tailed macaques. The acute pathogenic effects of this virus appear to be associated with at least two in vitro characteristics: the ability to induce lymphocyte proliferation; and the ability to replicate in unstimulated PBMC. Two of the amino acids in Nef of PBj14 (the No. 17 residue, tyrosine, and the No. 18 residue, glutamic acid) appear to be linked to the virus' ability to induce lymphocyte activation. To further study the effects of these amino acids on PBj14-induced pathogenesis, we generated two mutant viruses from our molecular clone, PBj6.6, containing either changes in both the No. 17 and No. 18 residues (termed PBj6.6YE-RQ), or a single change in the No. 17 residue (termed PBj6.6Y-R). In vitro analyses of these viruses showed that while their replicative abilities in stimulated peripheral blood mononuclear cells (PBMC) were altered, they still maintained the ability to replicate in unstimulated PBMC. Replication of these viruses in macrophage populations was impaired relative to the wild-type virus. Both mutant viruses were unable to induce proliferation of macaque PBMC in vitro. Virus derived from PBj6.6Y-R was unable to induce acute disease in macaques, but did maintain the ability to induce lymphopenia and intestinal lymphoid hyperplasia. These results show that the tyrosine-17 residue of Nef is linked to lymphocyte proliferation and disease development, but also suggest that the pathogenic characteristics of SIVsmmPBj14 are dependent upon multiple genetic determinants.

Age-dependent remodeling of peripheral blood CD4+ CD8+ T lymphocytes in cynomolgus monkeys

Recently, we have found in adult cynomolgus monkeys that substantial peripheral blood CD4+ CD8+ double-positive (DP) T lymphocytes exhibit a resting memory phenotype and increase in proportion with age. In this study, we investigated whether phenotypic changes occur in the course of the increase in proportion of the DP T cells. The results obtained from 195 clinically healthy monkeys aged from 1 month to 31 years showed that the CD29hi and CD28 subpopulation in the DP T subset increased in proportion with age and that the increase reached a plateau at six years old for the CD29hi subpopulation and at eleven years old for the CD28 one, respectively. The phenotypic alteration preceded the abrupt increase in proportion of the DP T cells and was able to be classified into four phases on the basis of the qualitative and quantitative alteration.

Comparative analysis of human and macaque monkey CD4: differences in formaldehyde lability and conformation

Here we characterized macaque monkey CD4 by flow cytometry. The results showed that relatively lower fluorescence intensity was observed depending on the monoclonal antibodies (mAbs) used for staining; Leu-3a exhibited four-fold lower intensity than Nu-Th/i, and that formaldehyde fixation dramatically reduced fluorescence intensity of macaque CD4+ cells stained with Leu-3a but not of human cells. Nu-Th/i is therefore preferable for the analysis of macaque CD4. Pretreatment of either mAb inhibited the other mAb binding to human CD4. On the contrary, Nu-Th/i inhibited Leu-3a binding but Leu-3a poorly blocked Nu-Th/i binding to the macaque CD4. These results indicate that Leu-3a and Nu-Th/i epitopes are conserved in macaque CD4 but Leu-3a epitope is conformationally cryptic and/or fragile, resulting in the lower affinity. Amino acid sequence alignment of CD4 domain 1 shows that the substitutions outside the linear Leu-3a epitope may determine these characteristics of macaque CD4.

CD8+ cell-mediated immune responses: relation to disease resistance and susceptibility in lentivirus-infected primates

Immune responses mediated by CD8+ lymphocytes have been correlated with protection from HIV infection and disease progression in humans and nonhuman primates. The CD8+ cell population is heterogeneous in terms of biological function and phenotype. We have undertaken a review of the current state of knowledge of subtypes of CD8+ cells and their role in immune responses directed to HIV and related primate lentiviruses. Differences in the pathogenesis of lentivirus infections in various primate hosts were examined and the possible roles of the various subpopulations of CD8+ lymphocytes in the resistance and/or susceptibility to lentivirus-related disease were compared.

Chronic social stress, social status, and susceptibility to upper respiratory infections in nonhuman primates

OBJECTIVE

The objective of the study was to assess the roles of social stress and social status in susceptibility to upper respiratory infection.

METHOD

Sixty male cynomolgus monkeys were randomly assigned to stable or unstable social conditions for 15 months. Two markers of social status, social rank and percent of behaviors that were submissive, were assessed at independent observation periods. Endocrine, immune, and behavioral responses were each assessed (at 3-month intervals) during the 9th through 14th months of the study. At the beginning of the 15th month, all animals were exposed to a virus (adenovirus) that causes a common-cold-like illness. The primary outcome was whether or not an animal developed an infection (shed virus) after viral exposure.

RESULTS

Although the social instability manipulation was associated with increased agonistic behavior as indicated by minor injuries and elevated norepinephrine responses to social reorganizations, the manipulation did not influence the probability of being infected by the virus. However, low social status (as assessed by either marker) was associated with a substantially greater probability of being infected. It was also associated with less body weight, greater elevated cortisol responses to social reorganizations, and less aggressive behavior. However, none of these characteristics could account for the relation between social status and infection.

CONCLUSIONS

Social stress was not associated with susceptibility to infection. However, animals with lower social status were at higher risk than high social status animals.

Immune and hematopoietic parameters in HIV-1-infected chimpanzees during clinical progression toward AIDS

Until recently, chimpanzees were considered susceptible to human immunodeficiency virus type 1 (HIV-1) infection, but refractory to disease induction based on the asymptomatic status of all experimentally infected chimpanzees after over 10 years postinfection (PI). However, a decline in peripheral CD4+ T cells was noted in one chimpanzee (C499) of the Yerkes cohort of HIV-1 infected apes, after 11 years PI concurrent with increasing plasma viral load. These clinical signs were followed by the occurrence of opportunistic infections, thrombocytopenia, and progressive anemia leading to euthanasia. A second chimpanzee (C455) was transfused with blood from C499 collected during the symptomatic stage. Shortly thereafter, this second animal showed a rapid decline in peripheral CD4+ T-cell levels and sustained high viral load. Hematological analyses showed a 50% decrease in CFU-GM for both apes during the symptomatic phase and a reduction of 40% and 73% of the total CFU despite normal levels of CD34+ cells in the bone marrow. Cryopreserved sequential PBMC samples from these two chimpanzees were analyzed for constitutive and PHA-P induced levels of cytokines and chemokines. Data show that whereas there were no detectable constitutive levels of mRNA coding for IL-2, 4, and 10, there appears to be a transient increase in IFN-gamma message level coincident with increased viremia and this IFN-gamma synthesis decreased with disease progression. PHA-induced cytokine mRNA analysis showed low or undetectable levels of IL-4 and IL-10 mRNA in all samples and a marked decrease in the levels of IL-2 shortly after HIV infection. In addition, there was also a gradual decrease in IFN-gamma mRNA with progression of disease. Of interest were the findings of high to normal levels of PHA-induced synthesis of the chemokines MIP-1alpha, MIP-1beta, and RANTES in samples during the asymptomatic and early symptomatic period, which also dramatically decreased at late stages of the disease. These data suggest important roles for IL-2, IFN-gamma, and the chemokines in the regulation of immune responses in HIV-1-infected chimpanzees.

Pertussis toxin induces lymphocytosis in rhesus macaques

Lymph nodes and other solid tissues of the immune system are the principal sites for antigen presentation and lymphocyte activation. Lymphocytes in peripheral blood recognize the high endothelial venules within lymphoid tissues and cross from blood to tissue by the process of extravasation. Pertussis toxin is known to block extravasation and cause lymphocytosis in murine models but has not been studied extensively in nonhuman primates. We used intravenous injection of soluble pertussis toxin to induce a transient lymphocytosis in rhesus monkeys. The increase in total white blood cells was proportionally greater for lymphocytes than for polymorphonuclear cells and the CD4+ lymphocyte subpopulation increased more than the CD8+ cell population. The presence of immature polymorphonuclear cells suggested some activation of bone marrow. Clinical chemistry studies revealed an effect of pertussis toxin on liver function. Pertussis toxin is a powerful immunomodulatory agent that can disrupt and reorganize solid lymphoid tissues.

In vitro interleukin-1 and 2 production and interleukin 2 receptor expression in the rhesus monkey

Anti-human monoclonal antibodies were used to detect and quantify interleukins-1 and 2 and interleukin-2 receptor expression in peripheral blood mononuclear cells from a rhesus monkey. Interleukin-1 production could be induced by phorbol esters (PMA) and was potentiated by phytohemagglutinin (PHA). Interleukin-2 secretion could also be induced by the combination of PHA and PMA, but only weakly with PHA alone. Interleukin-2 receptor expression was present in a subpopulation of unstimulated lymphocytes and could be enhanced by PHA or PMA. These data show once again that the rhesus monkey immune system is cross-reactive with the human one and that rhesus macaque could be a good model to study interleukin therapy.

Transient expression of CD20 antigen (pan B cell marker) in activated lymph node T cells

In contrast to the case of peripheral T cells, the surface expression of CD20 antigen and the expression of CD20 mRNA in monkey lymph node (LN) T cells underwent a noticeable increase when they were cultured with mitogen and interleukin-2 (IL-2). To confirm in vivo regulation of CD20 expression during the activation of LN T cells, we examined LNs derived from monkeys experimentally inoculated with simian immunodeficiency virus (SIV). Significant expression of CD20 antigen was detected in the T cells of the LNs at the stage of lymphadenopathy. These findings suggest that lymphocyte activation in the LNs induced expression of the CD20 molecule in some T cells.

Immunological and virological studies of natural SIV infection of disease-resistant nonhuman primates

Nonhuman primates naturally infected with simian immunodeficiency virus (SIV), while maintaining chronic viremia, do not develop any disease associated with lentiviral infection. Thus they provide a unique model to define the mechanism(s) by which they remain infected but disease-resistant. The purpose of this article is to summarize our current knowledge of the virological and immunological studies that have been performed in sooty mangabeys naturally infected with SIVsmm and in disease-susceptible rhesus macaques experimentally infected with SIVsmm. Data on virological studies demonstrate that the naturally infected sooty mangabeys are infected predominantly with SIV that have nef sequences distinct from those shown to cause disease in the inappropriate host, a factor which may contribute to disease resistance. Hyperimmunization with a variety of antigens or chronic infection contributes to accelerated disease and death in rhesus macaques if hyperimmunizations are initiated at the time of SIV infection, whereas similar hyperimmunization and chronic infection do not lead to disease in naturally infected seropositive sooty mangabeys. However, in both species infected with SIV, hyperimmunization leads to increased virus load, suggesting that virus load per se cannot account for disease, at least in naturally infected nonhuman primates. Immunological studies concerning changes in subsets of T cells, based on cytokine profile (TH0/TH1/TH2), showed that whereas rhesus macaques early post SIV infection show a dominant TH1 profile, this profile rapidly changes to TH0. On the other hand, mangabeys continuously demonstrate a TH2-like profile. Studies also showed a high frequency of in vivo-activated cells in the peripheral blood of SIV-infected rhesus macaques and mangabeys. Of interest, however, is the finding of a similar level of in vivo-activated cells from ELISA seronegative mangabeys. Although cells from SIV-infected mangabeys fail to show increased levels of apoptotic cells following incubation with immobilized anti-CD3, PBMC from rhesus macaques at varying time intervals do show increased levels of apoptotic cells, an increase which is predominantly seen in CD8+ T cells and is unrelated to levels of viremia. Sooty mangabeys maintain a high frequency of CD8+ T cells that regulate virus replication throughout their lifetime, a frequency that develops prior to ELISA-based seroconversion, whereas rhesus macaques only show a frequency of CD8+ T cells high enough to regulate virus replication shortly post infection, and this regulatory function is gradually lost prior to CD8+ cell loss and death. HIV and SIV infection do have profound effects on the expression of a number of costimulatory and adhesion molecules. There appear to be differences in the nature of the intracellular phosphorylated proteins in cells from activated rhesus macaques and mangabeys. We believe that careful studies of the detailed mechanisms of the issues described above may provide an understanding of the constellation of virological and immunological mechanisms responsible for the disease-resistant state of naturally infected sooty mangabeys. These findings can be employed for evaluating a nonvirus sterilizing form of SIV/HIV vaccines.

Tracking of dye-labeled lymphocytes in rhesus macaques

Lymphocytes were isolated from rhesus monkeys and marked with a fluorescent lipophilic dye to monitor their distribution in vivo. Dye-labeled cells were either monitored by blood draws over a three-month period, or identified within peripheral organs upon autopsy. Lymphocyte labeling conditions were optimized. Dye-labeled lymphocytes could be detected in the circulation for at least 100 days by flow cytometry and fluorescence microscopy. Activated lymphocytes were removed from the circulation more rapidly than lymphocytes that had not been activated.

Evaluation of anti-human antibodies for immunohistochemistry on archival nonhuman primate tissues

A panel of commercially available antibodies which recognize specific antigens on human tissues was developed for use in immunohistochemistry on tissues from eight species of nonhuman primates. Antibodies were selected for potential usefulness in diagnostic pathology, and for effectiveness in formalin-fixed, paraffin-embedded tissues. Tissues from four species of macaques and four New World monkeys were evaluated. Using these antibodies we were able to identify 17/21 antigens examined in all eight species, and 21/21 antigens in the four species of macaques. Detailed immunohistochemistry protocols are presented, along with a systematic approach to developing a protocol for a new antibody.

Cell surface marker evaluation of infant Macaca monkey leukocytes in peripheral whole blood using simultaneous dual-color immunophenotypic analysis

Cross-reactivity between several commercially available mouse antihuman monoclonal antibodies (mAbs), conjugated to phycoerythrin (PE) and fluorescein isothiocyanate (FITC) fluorochromes, and peripheral blood leukocyte surface antigens, has been established in infant cynomolgus (Macaca fascicularis) monkeys using whole blood lysis, and two-color, PE and FITC flow cytometric analysis. With the exception of the CD8 marker, the bivariate dot-plot patterns for all other markers were similar in infant monkeys and in humans. For the CD8 marker, however, a CD8+CD2- population of cells was observed in the majority of monkeys tested (10 out of 12). The number of CD8+CD2- cells was higher (13%) in infant monkeys compared to the 3% reported for adult human blood. The mean percentage and absolute numbers for the cell surface markers identified with the human mAbs CD2 (FITC, Ortho, Paritan, NJ), CD4 (PE, B-D, Mountain View, CA), and CD8 (PE, B-D) when these were combined with a series of PE- or FITC-labelled human mAbs were similar across all combinations tested. Statistically significant differences were observed between male and female monkeys for the mean percentage levels of CD4 (females > males) and for the CD4/CD8 ratio (females > males). Such gender differences need to be taken into consideration when infant cynomolgus monkeys are used as models for chemical-induced immunotoxicity studies. Measurement of the interleukin-2 (IL-2) and transferrin proved to be useful in monitoring in vitro cellular activation in infant cynomolgus and possibly in rhesus (M. mulatta) monkeys.

Cross-reactivity of antihuman monoclonal antibodies with cell surface receptors in the common marmoset

In this report we demonstrate that a large number of monoclonal antibodies (mAbs) against human epitopes cross-react with surface receptors on white blood cells of Callithrix jacchus, indicating species similarities. However, a variety of other mAbs do not exhibit any cross-reactivity, thus also providing evidence for distinct differences in the structure of these receptors among nonhuman primates. Such differences have to be known and taken into consideration when attempting extrapolations between species. The results presented provide the prerequisite for performing extensive studies on immunological structures and functions in marmosets under normal and pathological conditions. We conclude that the immune system of Callithrix jacchus is a convenient model for studies on immunotoxicity with relevance for man, and for this purpose it is clearly superior to that of any rodent species.

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.

Effect of a preferred companion in modulating stress in adult female rhesus monkeys

Using a counterbalanced design, seven adult female rhesus monkeys were removed from their social group and housed in a novel environment both alone and with a companion chosen on the basis of quantitative affiliative behaviors. Blood samples (n = 2) were collected from all study animals before the exposure to the novel environment, then at 2, 24, and 96 h thereafter for cortisol and immunological analyses. During both conditions, subjects showed evidence of stress as indicated by elevated cortisol concentrations and decreases in absolute numbers of lymphocyte subsets. There was no significant interaction between condition (alone vs. companion) and time in cortisol percent change and further planned post hoc analyses showed no significant between-condition differences for any of the postseparation time points. Similarly, no significant interaction was found between conditions and time for the absolute number of CD4+CD8-T cells, CD8+CD4- T cells, or CD20+CD2- B cells. However, planned post hoc comparisons showed that subjects in the companion condition exhibited a significantly smaller percent change from baseline than in the alone condition at the 24 h and 96 h sample periods in absolute numbers of CD4+CD8- and CD8+CD4- T cells. Results showed that adult female rhesus monkeys exhibited a profound stress response when removed from their social group to a novel environment and that recovery time of T cell subsets was significantly enhanced by the presence of a preferred companion.

Effect of a preferred companion in modulating stress in adult female rhesus monkeys

Using a counterbalanced design, seven adult female rhesus monkeys were removed from their social group and housed in a novel environment both alone and with a companion chosen on the basis of quantitative affiliative behaviors. Blood samples (n = 2) were collected from all study animals before the exposure to the novel environment, then at 2, 24, and 96 h thereafter for cortisol and immunological analyses. During both conditions, subjects showed evidence of stress as indicated by elevated cortisol concentrations and decreases in absolute numbers of lymphocyte subsets. There was no significant interaction between condition (alone vs. companion) and time in cortisol percent change and further planned post hoc analyses showed no significant between-condition differences for any of the postseparation time points. Similarly, no significant interaction was found between conditions and time for the absolute number of CD4+CD8-T cells, CD8+CD4- T cells, or CD20+CD2- B cells. However, planned post hoc comparisons showed that subjects in the companion condition exhibited a significantly smaller percent change from baseline than in the alone condition at the 24 h and 96 h sample periods in absolute numbers of CD4+CD8- and CD8+CD4- T cells. Results showed that adult female rhesus monkeys exhibited a profound stress response when removed from their social group to a novel environment and that recovery time of T cell subsets was significantly enhanced by the presence of a preferred companion.

Viral genetic determinants in SIVsmmPBj pathogenesis

A variant simian immunodeficiency virus (SIV) from sooty mangabeys, SIVsmmPBj, induces an acutely lethal disease in pigtailed macaques (Macaca nemestrina). This study further characterizes the viral genetic determinants involved in this acutely lethal disease. We have generated chimeric molecular clones constructed between SIVsmmPBj and either SIVsmH4 or SIVsmm9 to analyze the role of the 5' half of the genome and the envelope gene in the induction of acute disease. These studies suggest that the gag and gp40 of SIVsmmPBj are required for the development of lethal disease, and an additional determinant in the central regulatory gene region of the SIVsmmPBj genome is also required.

TH1/TH2 subset analysis. I. Establishment of criteria for subset identification in PBMC samples from nonhuman primates

Cloned T-cell lines from two nonhuman primate species were phenotyped and their mRNA analyzed for cytokine profiles by RT-PCR procedures. PBMC from rhesus macaques showed a relatively high frequency of cloned T-cell lines with a TH1-like profile; PBMC from sooty mangabeys showed a relatively high frequency of TH2-like cloned T-cell lines. In vitro activated macaque PBMC also resulted in a high frequency of CD4+, CD8+ dual marked cells. These findings suggest that cytokine analysis of cloned T-cell lines from nonhuman primates provides a means to distinguish subsets of both CD4+ and CD8+ T cells.

The mitogen-induced generation of interferon-gamma producing cells in cultures of rhesus monkey peripheral blood mononuclear cells is age-dependent

An enzyme-linked immunoabsorbent spot (ELISPOT) assay has been developed for measuring the frequency of interferon-gamma (IFN-gamma) producing cells in rhesus monkeys. Aged monkeys revealed, upon mitogenic stimulation, a significantly higher percentage of IFN-gamma secreting peripheral blood mononuclear cells (PBMC) compared to young animals. No correlation was found between the frequency of IFN-gamma producing PBMC and the mitogen-driven proliferation, indicating that in rhesus monkeys no direct correlation exists between these two activation parameters.

Qualitative and quantitative studies of cytokines synthesized and secreted by non-human primate peripheral blood mononuclear cells

Non-human primates are being utilized in a variety of pre-clinical studies, including those involved with mechanisms of organ transplant rejection and those being used as models to test the efficacy of vaccines against a variety of infectious diseases, most notably AIDS. These studies clearly involve immunological effector mechanisms, which include the interaction between T cells, B cells, monocytes, and cytokines that regulate these interactions. However, there is very little known about assays and quantitation of cytokines from non-human primates. In attempts to address this issue, bioassays, commercially available EIA kits, and primer pairs and probes specific for human cytokines were evaluated for their ability to detect and quantitate the non-human primate homologues. Data suggest that although the EIA kits that were evaluated for human IL-1 alpha, IFN-gamma, and TNF-beta failed, the EIA kits for IL-1 beta, IL-2, IL-4, IL-6, and TNF-alpha, the bioassays and RT-PCR assays for each of the cytokines were successful in detection and most likely quantitation of the non-human primate cytokine homologues. These assays will greatly facilitate future studies on the role of cytokines in these non-human primate studies.

Inhibition of cellular activation of retroviral replication by CD8+ T cells derived from non-human primates

To test the hypothesis that CD8+ T cells inhibit viral replication at the level of cellular activation, an Epstein-Barr virus (EBV)-transformed cell line (FEc1) from a simian immunodeficiency virus (SIV)-seropositive sooty mangabey monkey was transfected with a human CD4 gene and shown to be replication-competent for HIV-1, HIV-2 and SIV. Utilizing a dual-chamber culture system, it was found that inhibition of viral replication can be mediated by a soluble factor. The FEc1 cell line was transiently transfected with an LTR-driven CAT reporter gene. It was found that autologous CD8+ T cells markedly inhibited CAT activity. Furthermore, co-transfection of the FEc1 cell line with an LTR-driven tat plasmid and LTR-CAT was able to quantitatively mitigate the suppressive effect. Thus, this inhibition appears to be directed at cellular mechanisms of viral transcription. Control transfections with an LTR-driven CAT plasmid with a mutation at the NFkB binding site yielded no CAT activity, suggesting that most viral replication as measured by CAT activity is dependent, to a large extent, upon cellularly derived NFkB binding proteins.

Response to removal from and return to a social group in adult male rhesus monkeys

The removal of four adult rhesus monkeys from a large social group (n = 85) to peer housing resulted in no significant changes in basal cortisol levels or absolute numbers of T lymphocyte subsets 24 h later. However, the return of these males 1 year later to the same social group resulted in significant increases in cortisol levels (66 +/- 21%) and significant decreases in T-helper (-31.6 +/- 15.8%) and T-suppressor cells (-35.2 +/- 8.7%) 24 h later. Blood samples for immune and cortisol measurements were obtained before and 24 h following both the removal and the return 1 year later. Aggressive and sexual behavioral data were recorded on audiotape for 3.5 h following the reintroduction using an all occurrences of some behaviors sampling technique. Analyses revealed a negative correlation between percent change from baseline in T-helper cells 24 h following the return and the frequency of bites (nonwounding) and chases received during the 3.5 h following the return. The absence of a stress response to separation in adult males is in contrast to the presence of a stress response observed in infants, juveniles, and adult females and possibly is due to sex differences in group attachment in sexually mature males. On the other hand, the return to the social group did induce a psychosocial stress response in the males, and the degrees of the stress, as determined by cortisol and immune cell measures, was related to the agonistic interactions experienced by the individuals.

Behavioral and physiological response of juvenile sooty mangabeys to reunion with their mothers following a year's absence

The return of 6 juvenile mangabey monkeys to their social group following an absence of a year resulted in increased basal cortisol secretion for both the offspring and the mothers and in significant decrements in the absolute number of lymphocyte subsets for the offspring. Six 9-month-old sooty mangabeys were removed from their socially housed mothers, subsequently peer housed, and returned to the maternal social group 1 year later. Offspring showed a significant increase in cortisol levels 24 hr following reunion (48 +/- 6%) and this difference persisted through 1 month, while the mothers showed a significant increase only at the 24-hr sample point (18 +/- 3%). Moreover, the offspring, but not the mothers, showed a significant decrease in lymphocyte subsets which were evident through the 1-month sample point. Behavioral data revealed a significant positive correlation between the percent of total scan samples offspring were with their mothers (proximity, contact, huddle) the day of return and the offspring's percent change from baseline in total T cells 24 hr later, r = 0.84. All mother-offspring pairs with the exception of one exhibited frequent affiliative behaviors toward one another by 6 days following the return. These data demonstrate that the reunion of juvenile mangabeys with their mothers after a year's absence is an acute stressor for the mothers and a relatively longer term stressor for the offspring, and that behavioral interactions which characterize the return of individual subjects to the natal group can predict acute physiological responses.