Variation in infant rhesus monkeys' (Macaca mulatta) neutrophil-to-lymphocyte ratio is associated with environmental conditions, emotionality, and cortisol concentrations, and predicts disease-related outcomes

The neutrophil-to-lymphocyte ratio (NLR) is a predictor of morbidity for a variety of medical conditions, but little is known about how variation in NLR arises. We examined variation in this measure in a sample of 4577 infant rhesus monkeys (54.8 % female), who participated in the BioBehavioral Assessment program at the California National Primate Research Center at 3-4 months of age. Lower values for NLR were seen for animals reared indoors, for animals that were raised to be free of specific pathogens, and for males. In addition lower NLR was associated with higher stress values of cortisol and with greater emotionality in response to an acute stressor. Finally, lower NLR in infancy was associated with greater risk for developing airways hyperresponsiveness (a hallmark of asthma); with display of diarrhea up to 3.97 years later; and with greater viral load when infected with the simian immunodeficiency virus at a mean of 6.1 years of age. Infant NLR was a better predictor of viral load than was a contemporaneously obtained measure of NLR. Infant and adult values of NLR were only modestly correlated; one reason may be that the infant measure was obtained during stressful conditions and the adult measure was obtained under baseline conditions. We propose that NLR is an integrated outcome measure reflecting organization and interaction of stress-response and immune systems. As such, assessment of NLR under conditions of stress may be a particularly useful marker of individual differences in morbidity, especially for conditions in which stress plays an important role, as in asthma, diarrhea/colitis, and AIDS.

Antemortem Screening for Left Ventricular Hypertrophy in Rhesus Macaques (Macaca mulatta)

Concentric left ventricular hypertrophy (LVH) is a hallmark finding in hypertrophic cardiomyopathy that leads to diastolic dysfunction and variable cardiac consequences as severe as congestive heart failure and sudden cardiac death. LVH was diagnosed postmortem in a large colony of rhesus macaques (Macaca mulatta), but methods to screen and diagnose LVH in living animals are desired. We hypothesized that targeted echocardiography of macaques with a familial association of LVH would yield antemortem LVH diagnoses. We also hypothesized that cardiac biomarker levels would be higher in sudden-death LVH or occult LVH than controls and that cardiac troponin I (cTnI) levels would be higher in macaques housed outdoors than indoors. Sera were assayed for cardiac biomarkers (cTnI, C-reactive protein, creatinine kinase-MB, creatine phosphokinase, and LDH), in conjunction with echocardiography, after diagnosis by postmortem exam or from animals with different levels of exercise due to indoor compared with outdoor housing. None of the investigated biomarkers were associated with LVH. cTnI levels were significantly higher in serum collected from outdoor than indoor macaques. In addition, LVH was diagnosed in 29.4% of subjects with a familial association of LVH. These findings suggest that exercise may increase cTnI levels in rhesus macaques and that targeted echocardiography of rhesus macaques with a familial association of LVH was the most useful variable examined for disease surveillance.

The interplay between immune maturation, age, chronic viral infection and environment

BACKGROUND

The worldwide increase in life expectancy has been associated with an increase in age-related morbidities. The underlying mechanisms resulting in immunosenescence are only incompletely understood. Chronic viral infections, in particular infection with human cytomegalovirus (HCMV), have been suggested as a main driver in immunosenescence. Here, we propose that rhesus macaques could serve as a relevant model to define the impact of chronic viral infections on host immunity in the aging host. We evaluated whether chronic rhesus CMV (RhCMV) infection, similar to HCMV infection in humans, would modulate normal immunological changes in the aging individual by taking advantage of the unique resource of rhesus macaques that were bred and raised to be Specific Pathogen Free (SPF-2) for distinct viruses.

RESULTS

Our results demonstrate that normal age-related immunological changes in frequencies, activation, maturation, and function of peripheral blood cell lymphocytes in humans occur in a similar manner over the lifespan of rhesus macaques. The comparative analysis of age-matched SPF-2 and non-SPF macaques that were housed under identical conditions revealed distinct differences in certain immune parameters suggesting that chronic pathogen exposure modulated host immune responses. All non-SPF macaques were infected with RhCMV, suggesting that chronic RhCMV infection was a major contributor to altered immune function in non-SPF macaques, although a causative relationship was not established and outside the scope of these studies. Further, we showed that immunological differences between SPF-2 and non-SPF macaques were already apparent in adolescent macaques, potentially predisposing RhCMV-infected animals to age-related pathologies.

CONCLUSIONS

Our data validate rhesus macaques as a relevant animal model to study how chronic viral infections modulate host immunity and impact immunosenescence. Comparative studies in SPF-2 and non-SPF macaques could identify important mechanisms associated with inflammaging and thereby lead to new therapies promoting healthy aging in humans.

Cross-species transmission of a novel adenovirus associated with a fulminant pneumonia outbreak in a new world monkey colony

Adenoviruses are DNA viruses that naturally infect many vertebrates, including humans and monkeys, and cause a wide range of clinical illnesses in humans. Infection from individual strains has conventionally been thought to be species-specific. Here we applied the Virochip, a pan-viral microarray, to identify a novel adenovirus (TMAdV, titi monkey adenovirus) as the cause of a deadly outbreak in a closed colony of New World monkeys (titi monkeys; Callicebus cupreus) at the California National Primate Research Center (CNPRC). Among 65 titi monkeys housed in a building, 23 (34%) developed upper respiratory symptoms that progressed to fulminant pneumonia and hepatitis, and 19 of 23 monkeys, or 83% of those infected, died or were humanely euthanized. Whole-genome sequencing of TMAdV revealed that this adenovirus is a new species and highly divergent, sharing <57% pairwise nucleotide identity with other adenoviruses. Cultivation of TMAdV was successful in a human A549 lung adenocarcinoma cell line, but not in primary or established monkey kidney cells. At the onset of the outbreak, the researcher in closest contact with the monkeys developed an acute respiratory illness, with symptoms persisting for 4 weeks, and had a convalescent serum sample seropositive for TMAdV. A clinically ill family member, despite having no contact with the CNPRC, also tested positive, and screening of a set of 81 random adult blood donors from the Western United States detected TMAdV-specific neutralizing antibodies in 2 individuals (2/81, or 2.5%). These findings raise the possibility of zoonotic infection by TMAdV and human-to-human transmission of the virus in the population. Given the unusually high case fatality rate from the outbreak (83%), it is unlikely that titi monkeys are the native host species for TMAdV, and the natural reservoir of the virus is still unknown. The discovery of TMAdV, a novel adenovirus with the capacity to infect both monkeys and humans, suggests that adenoviruses should be monitored closely as potential causes of cross-species outbreaks.

Infection from adenoviruses, viruses that cause a variety of illnesses in humans, monkeys, and other animals, has conventionally been thought to be species-specific. We used the Virochip, a microarray designed to detect all viruses, to identify a new species of adenovirus (TMAdV, or titi monkey adenovirus) that caused a deadly outbreak in a colony of New World titi monkeys at the California National Primate Research Center (CNPRC), and also infected a human researcher. One-third of the monkeys developed pneumonia and liver inflammation, and 19 of 23 monkeys died or were humanely euthanized. The unusually high death rate (83%) makes titi monkeys unlikely to be natural hosts for TMAdV, and the genomic sequence of TMAdV revealed that it is very different from any other known adenovirus. The researcher developed an acute respiratory illness at the onset of the outbreak, and was found to be infected by TMAdV by subsequent antibody testing. A clinically ill family member with no prior contact with the CNPRC also tested positive. Further investigation is needed to identify whether TMAdV originated from humans, monkeys, or another animal. The discovery of TMAdV suggests that adenoviruses should be monitored closely as potential causes of cross-species outbreaks.

Chronic administration of tenofovir to rhesus macaques from infancy through adulthood and pregnancy: summary of pharmacokinetics and biological and virological effects

The reverse transcriptase (RT) inhibitor tenofovir (TFV) is highly effective in the simian immunodeficiency virus (SIV) macaque model of human immunodeficiency virus infection. The current report describes extended safety and efficacy data on 32 animals that received prolonged (>or=1- to 13-year) daily subcutaneous TFV regimens. The likelihood of renal toxicity (proximal renal tubular dysfunction [PRTD]) correlated with plasma drug concentrations, which depended on the dosage regimen and age-related changes in drug clearance. Below a threshold area under the concentration-time curve for TFV in plasma of approximately 10 microg x h/ml, an exposure severalfold higher than that observed in humans treated orally with 300 mg TFV disoproxil fumarate (TDF), prolonged TFV administration was not associated with PRTD based on urinalysis, serum chemistry analyses, bone mineral density, and clinical observations. At low-dose maintenance regimens, plasma TFV concentrations and intracellular TFV diphosphate concentrations were similar to or slightly higher than those observed in TDF-treated humans. No new toxicities were identified. The available evidence does not suggest teratogenic effects of prolonged low-dose TFV treatment; by the age of 10 years, one macaque, on TFV treatment since birth, had produced three offspring that were healthy by all criteria up to the age of 5 years. Despite the presence of viral variants with a lysine-to-arginine substitution at codon 65 (K65R) of RT in all 28 SIV-infected animals, 6 animals suppressed viremia to undetectable levels for as long as 12 years of TFV monotherapy. In conclusion, these findings illustrate the safety and sustained benefits of prolonged TFV-containing regimens throughout development from infancy to adulthood, including pregnancy.

Effects of the macrolide drug tylosin on chronic diarrhea in rhesus macaques (Macaca mulatta)

Diarrhea is the gastrointestinal disease most frequently encountered in captive rhesus macaques. The precise pathogenic mechanisms underlying chronic diarrhea in nonhuman primates are not well understood, but a persistent inflammatory component has been implicated strongly. This study evaluated the inflammatory changes in the colon of macaques with diarrhea and assessed the efficacy of a 10-d course of tylosin in a cohort of 21 animals with chronic diarrhea. Stool quality was evaluated daily, and fecal consistency was scored. Colonoscopies were performed; biopsy samples were characterized histologically and assayed for expression of TNFalpha mRNA. Blood samples collected pre-, mid-, and post-treatment were assayed for C-reactive protein (CRP). The results indicated that 63% of the animals receiving tylosin showed improvement in stool quality, compared with 10% in the sham-treated group. Histologically, 82% of animals in the tylosin-treated group had a reduction in the severity of colonic lesions post-treatment, compared with 40% of animals in the sham group. The amount of TNFalpha mRNA before treatment did not differ from that afterward in either tylosin- or sham-treated animals. CRP levels serially decreased in tylosin-treated monkeys; the average post-treatment CRP value for tylosin-treated animals was 11.96 +/- 3.86 microg/ml compared with 26.48 +/- 4.86 microg/ml for sham-treated controls. In conclusion, tylosin significantly improved the fecal consistency score, significantly decreased colonic inflammation, and significantly decreased serum CRP levels post-treatment in rhesus macaques with chronic diarrhea.

Effects of environmental tobacco smoke on the developing immune system of infant monkeys

BACKGROUND

Exposure to environmental tobacco smoke (ETS) is associated with an increased incidence of allergic and infectious diseases among children that is thought to be partly due to the immaturity of the immune system.

OBJECTIVE

We sought to investigate the effects of ETS exposure on immune development during the first year of life in the nonhuman primate.

METHODS

Fifteen neonatal rhesus monkeys studied to 13 months of postnatal age were randomized into 3 groups: (1) exposure to filtered air, (2) continuous ETS exposure beginning at gestation day 50 (perinatal ETS); and (3) exposure to ETS beginning at 6 months of age (6-month ETS). Complete blood counts, lymphocyte subsets, and mRNA levels of 12 cytokines in PBMCs were measured.

RESULTS

Fetal/infant exposure to ETS altered the normal maturation of mRNA levels of IFN-gamma, IL-2, and IL-10, as well as the ratio of CD4 to CD8 lymphocytes, compared with filtered-air control levels. Blood lymphocyte subset distribution also significantly differed based on the onset of exposure to ETS. Subacute exposure to ETS for 2 weeks in 6-month-old infants was found to increase levels of peripheral blood neutrophils and IL-6 mRNA.

CONCLUSIONS

Short-term exposure to ETS can induce an acute systemic inflammatory response in the neonatal nonhuman primate, and long-term exposure to ETS beginning in utero or at 6 months of postnatal age can significantly alter immune effectors.

CLINICAL IMPLICATIONS

Normal immune system development is compromised by in utero and postnatal exposure to ETS and might contribute to ETS-related childhood diseases.

Compared with cyclosporine, ISATX247 significantly prolongs renal-allograft survival in a nonhuman primate model

BACKGROUND

ISATX247 is a novel calcineurin inhibitor that has shown more potency than cyclosporine in vitro. This is the first study to compare the survival times of renal allografts in nonhuman primates treated with either ISATX247 or cyclosporine.

METHODS

Adult, male cynomolgus monkeys were divided into blood-group compatible and mixed-lymphocyte, stimulation-mismatched, donor-recipient pairs. Heterotopic renal transplantation and bilateral native nephrectomies were performed. The monkeys were placed into either an ISATX247 or cyclosporine treatment group. Both groups were dosed twice daily to maintain a 12-hour drug-trough level of 150 ng/mL. Whole-blood concentrations of ISATX247 and cyclosporine, complete blood counts, and serum chemistry profiles were performed three times a week. Euthanasia was performed if the serum creatinine concentration became 7 or more mg/dL or a serious complication developed.

RESULTS

The group receiving ISATX247 (n=8) survived significantly (P=0.0036) longer than the group receiving cyclosporine (n=7). The mean trough blood concentration of ISATX247 was 120 +/- 32 ng/mL and cyclosporine was 189 +/- 130 ng/mL. The average area under the curve 0-12 for ISATX247 was 6045 +/- 1679 ng/mL/hr and for cyclosporine was 4919 +/- 823 ng/mL/hr. The average calcineurin inhibition at trough blood concentrations was 80 +/- 11% for ISATX247 and 48 +/- 12% for cyclosporine.

CONCLUSIONS

Allografts in monkeys treated with ISATX247 survived significantly longer than those treated with cyclosporine. On the basis of survival times and degree of calcineurin inhibition, ISATX247 is a more potent immunosuppressive agent than cyclosporine in this nonhuman primate model of renal-allograft transplantation.

Subsets of T cells in healthy rhesus macaques (Macaca mulatta) infected with simian T-lymphotropic virus type 1

Simian T-lymphotropic virus type 1 (STLV-1) is a C-type retrovirus of nonhuman primates that is genetically and antigenically related to human T-lymphotropic virus type 1 (HTLV-1). Infection with STLV-1 has been reported in many species of Old World monkeys and apes, including rhesus macaques (Macaca mulatta). Similar to HTLV infection in humans, STLV infection has been associated with T-cell lymphoproliferative disease or lymphoma in a small proportion of infected animals, predominantly African species. There are conflicting reports of T-cell subset alterations in healthy HTLV-1 carriers. To the authors' knowledge, analysis of T-cell subsets in healthy STLV-1 carrier rhesus macaques has not been reported. Subsets of T cells in peripheral blood from healthy, STLV-1-seropositive rhesus macaques (n = 17) and seronegative controls matched for age and sex (n = 17) were determined by use of fluorescence-activated cell sorter analysis. Parameters measured included CD3, CD4, CD8, CD25, CD28, CD38, and HLA-DR cell sets. Significant differences in T-cell subsets or hematologic parameters were not observed between healthy STLV-seropositive and seronegative groups.

Biological effects of short-term or prolonged administration of 9-[2-(phosphonomethoxy)propyl]adenine (tenofovir) to newborn and infant rhesus macaques

The reverse transcriptase inhibitor 9-[2-(phosphonomethoxy)propyl]adenine (PMPA; tenofovir) was previously found to offer strong prophylactic and therapeutic benefits in an infant macaque model of pediatric human immunodeficiency virus (HIV) infection. We now summarize the toxicity and safety of PMPA in these studies. When a range of PMPA doses (4 to 30 mg/kg of body weight administered subcutaneously once daily) was administered to 39 infant macaques for a short period of time (range, 1 day to 12 weeks), no adverse effects on their health or growth were observed; this included a subset of 12 animals which were monitored for more than 2 years. In contrast, daily administration of a high dose of PMPA (30 mg/kg subcutaneously) for prolonged periods of time (>8 to 21 months) to 13 animals resulted in a Fanconi-like syndrome (proximal renal tubular disorder) with glucosuria, aminoaciduria, hypophosphatemia, growth restriction, bone pathology (osteomalacia), and reduced clearance of PMPA. The adverse effects were reversible or were alleviated following either complete withdrawal of PMPA treatment or reduction of the daily regimen from 30 mg/kg to 2.5 to 10 mg/kg subcutaneously. Finally, to evaluate the safety of a prolonged low-dose treatment regimen, two newborn macaques were started on a 10-mg/kg/day subcutaneous regimen; these animals are healthy and have normal bone density and growth after 5 years of daily treatment. In conclusion, our findings suggest that chronic daily administration of a high dose of PMPA results in adverse effects on kidney and bone, while short-term administration of relatively high doses and prolonged low-dose administration are safe.

Prevalence of antibodies to selected viruses in a long-term closed breeding colony of rhesus macaques (Macaca mulatta) in Brazil

The rhesus macaque breeding colony of the Oswaldo Cruz Foundation (FIOCRUZ) was established in 1932 from a founding stock of 100 animals. This population has remained closed to new animal introductions for almost 70 years. A serologic survey was performed to determine the prevalence of antibodies to selected viruses as a first approach to identifying viral pathogens endemic in this population. Banked serum samples were tested for antibodies to simian immunodeficiency virus (SIV), simian T-lymphotropic virus (STLV), simian type D retrovirus (SRV), cercopithecine herpesvirus type-1 (B virus), rhesus cytomegalovirus (RhCMV), measles virus (MV), and hepatitis A virus (HAV). All samples were negative for antibodies against the simian retroviruses. The overall prevalence of antibodies was 95% for RhCMV, 45% for B virus, 35% for HAV, and 1% for MV. Prevalence was found to vary by age group.

Comparative efficacy of a canine distemper-measles and a standard measles vaccine for immunization of rhesus macaques (Macaca mulatta)

Measles virus (MV), a highly infective paramyxovirus, has caused sporadic epizootics characterized by high morbidity and increased mortality in nonhuman primates. Measles vaccines for human use, although effective, are cost prohibitive for use in primate colonies. We compared the efficacy of one or two doses of Vanguard D-M, a canine distemper-measles (CD-M) vaccine, with a single dose of Attenuvax, a human measles vaccine. Compared with 81% of animals inoculated with Attenuvax, all animals inoculated with one or two doses of Vanguard developed detectable MV antibodies. One year after immunization, six juveniles from each vaccine group, along with three unvaccinated controls, were challenged with pathogenic MV and were monitored for clinical signs of disease, viremia, viral shedding, and immune response. All uninoculated controls developed clinical disease and viremia, and shed virus in nasopharangeal secretions. Subclinical viremia without viral shedding was identified in two Attenuvax- and two single-dose Vanguard-inoculated animals. Viremia was not detected in any two-dose Vanguard-inoculated animals. Significantly higher neutralization antibody titers were observed in animals receiving Vanguard. Results of this study indicate that Vanguard is at least as efficacious as Attenuvax for protection of rhesus macaques. The considerably lower cost of Vanguard makes vaccination against measles in large breeding colonies economically feasible.

T-cell lymphoproliferative disorder in an aged rhesus macaque

A CD8+ T-cell leukemia was diagnosed in an aged female rhesus macaque. Although leukemia and lymphoma in nonhuman primates are commonly associated with simian T-lymphotropic virus, gibbon ape leukemia virus, oncogenic herpesviruses, and types C, D, and E retroviruses, this monkey was not infected with any of these viruses. However, the monkey did have antibodies against herpesvirus saimiri. This likely represents cross-reactivity of the herpesvirus saimiri assay with rhesus monkey rhadinovirus (RRV) antibodies; RRV was first described in rhesus macaques that were identified as having antibodies against herpesvirus saimiri. Rhesus rhadinovirus is a gamma herpesvirus, related antigenically to herpesvirus saimiri and Kaposi's sarcoma-associated herpesvirus (KSHV), which have been linked to lymphoproliferative disorders in primates and humans, respectively. Moreover, an oncogene has been recently identified in the RRV genome that is equivalent in position to the herpesvirus saimiri and KSHV oncogenes. Presently, the association of RRV infection with disease in nonhuman primates is unknown.

9-[2-(Phosphonomethoxy)propyl]adenine therapy of established simian immunodeficiency virus infection in infant rhesus macaques

The long-term therapeutic and toxic effects of 9-[2-(phosphonomethoxy)propyl]adenine (PMPA) were evaluated in simian immunodeficiency virus (SIV)-infected newborn rhesus macaques. Four untreated SIV-infected newborn macaques developed persistently high levels of viremia, and three of the four animals had rapidly fatal disease within 3 months. In contrast, long-term PMPA treatment of four newborn macaques starting 3 weeks after virus inoculation resulted in a rapid, pronounced, and persistent reduction of viremia in three of the four animals. Emergence of virus with fivefold-decreased susceptibility to PMPA occurred in all four PMPA-treated animals and was associated with the development of a lysine-to-arginine substitution at amino acid 65 (K65R mutation) and additional mutations in the reverse transcriptase; however, the clinical implications of this low-level drug resistance are nuclear. No toxic side effects have been seen, and all PMPA-treated animals have remained disease-free for more than 13 months. Our data suggest that PMPA holds much promise for the treatment of human immunodeficiency virus-infected human infants and adults.

Asymptomatic infection of the central nervous system by the macaque immunosuppressive type D retrovirus, SRV-1

The aetiological agent of spontaneously occurring simian acquired immune deficiency syndrome (SAIDS) in rhesus monkeys (Macaca mulatta) at the California Primate Research Center is a type D retrovirus designated SAIDS retrovirus serotype 1 (SRV-1). SRV-1 DNA and RNA have previously been detected in the brains of rhesus monkeys with SAIDS in the absence of viral antigen or neuropathological lesions. In this study we further define the relationship between SRV-1 and the central nervous system (CNS) in rhesus monkeys by examining the CNS for infectious SRV-1, viral antigen and anti-SRV-1 antibodies. In addition, cerebrospinal fluid (CSF) was assayed for alterations in IgG and albumin levels, IgG/albumin ratios and cell count in comparison to uninfected control animals. No differences in CSF parameters were detected between infected and uninfected animals except for the presence of infectious SRV-1 which was isolated from the CSF from 13 out of 19 (68%) viraemic rhesus monkeys. The probable source of this virus was the choroid plexus, where approximately 1 in 1000 surface epithelial cells were found to contain viral antigen by immunohistochemistry. Antibodies against SRV-1 were not detected in the CSF even when present in the serum. Neither infectious virus nor viral antigen were found in the brain parenchyma of any animal examined. Thus infection of the CNS by SRV-1 appears to be subclinical without an intrathecal immune response. This may be related to the apparent restriction of productive infection in the CNS to cells of the choroid plexus.

Simian AIDS ELISA: sensitivity, specificity and predictive values based on a comparison with Western blot technique

Simian Acquired Immunodeficiency Syndrome (SAIDS) is an important disease in captive primates in the United States associated with an unusually high mortality rate. Isolation of a type D retrovirus as the cause of SAIDS was rapidly followed by the development of an enzyme linked immunosorbent assay (ELISA) to determine the exposure of rhesus macaques (Macaca mulatta) to this virus. With increased use of the ELISA, a better understanding for interpretation of results was needed. One hundred thirty-one rhesus macaques were tested for the presence of antibody against SAIDS type D retrovirus (SRV) by both ELISA and Western blot techniques. Sensitivity, specificity and predictive values for the SAIDS ELISA were calculated for two populations based on a comparison with Western blot results. Sera was tested from two distinct populations, an endemic and a control population. Seventy-one macaques from a half-acre outdoor corral where SAIDS was first recognized made up the endemic population. Sixty rhesus macaques from both indoor and outdoor areas where the disease was not recognized made up the control population. This study has shown the ELISA to be a useful screening tool based on its high sensitivity for both endemic and control populations. This screening method provides a rapid and economical way to diagnose and manage SAIDS in captive non-human primate colonies.

Pathogenesis of simian AIDS in rhesus macaques inoculated with the SRV-1 strain of type D retrovirus

Type D retrovirus was isolated from rhesus macaques with simian acquired immunodeficiency syndrome (SAIDS) and transmitted to healthy rhesus macaques with tissue culture medium containing the virus. The clinical, immunologic, and lymph node morphologic changes were observed in 9 rhesus macaques for 52 weeks after inoculation. A spectrum of clinical signs developed including early death, persistent SAIDS, and apparent remission. Animals that died or developed persistent SAIDS had characteristic lymphoid depletion, persistently depressed peripheral blood mononuclear cell (PBMC) mitogenic response, and decreased serum immunoglobulins. The SAIDS retrovirus (SRV) was recovered from PBMC of 8 of the animals after inoculation. Virus could not be recovered from PBMC of one animal in remission, but this animal developed serum-neutralizing antibodies to SRV after inoculation. Seven of the animals seroconverted to SRV after inoculation, all 9 were seronegative for human T-lymphotropic virus-III, and 5 animals tested were seronegative to human T-lymphotropic virus-I. These findings support the etiologic role of the type D retrovirus in SAIDS and further define the pathogenesis of this disease.

Hematologic abnormalities in simian acquired immune deficiency syndrome

Hematologic abnormalities were defined in 31 rhesus monkeys (Macaca mulatta) with simian acquired immune deficiency syndrome (SAIDS). Animals manifested anemia (hypochromic/microcytic), severe neutropenia and progressive lymphopenia, monocytosis and occasional thrombocytopenia. Bone marrow studies showed erythroid hyperplasia with a marked left shift and adequate megakaryocytes. Two animals showed profound hypoplasia of all hematopoietic elements. Most animals were iron deficient, but the course of the anemia suggested additional factors. There was no evidence of immune hemolysis. The pathogenesis of these abnormalities is not clear and will require further study. This reproducible disease will allow studies to elucidate the mechanisms of viral-induced hematologic abnormalities.