The cost-effectiveness of interventions in diabetes: a review of published economic evaluations in the UK setting, with an eye on the future.

AIM: To synthesise key outcomes data from cost-effectiveness studies in diabetes, in the UK setting, and describe a narrative for the evidence-base, in order to understand the direction that future health economics research in this field could be heading. METHODS: The peer-reviewed literature was searched at http://www.pubmed.com for health economics analyses in diabetes in the UK setting published between 1995 and 2008, using the keywords: "costs", "cost-effectiveness", "diabetes", "UK". Studies on screening for diabetes or prevention of diabetes were excluded, along with studies that looked purely at cost of diabetes treatment or monitoring. RESULTS: There were over 350 hits on MEDLINE. A total of 23 articles were identified and reviewed. 18 studies were in type 2, two in type 1 and three studies in both types 1 and type 2 diabetes. All studies evaluated treatment from the perspective of the NHS, with the time horizons varying from 12 months to patient lifetimes. 13 studies estimated quality-adjusted life expectancy (QALE). The majority of studies used health economics modelling techniques to project clinical benefit and cost outcomes beyond the context of clinical trials, with Markov-type models predominating. The United Kingdom Prospective Study of Diabetes was the most frequently cited source of clinical effectiveness and cost data. Most studies were funded by the pharmaceutical industry and evaluated more expensive products, rather than cheaper generic therapies such as human insulin and metformin monotherapy. CONCLUSION: Treatment-to-target in patients with diabetes in the UK is generally cost-effective and sometimes cost-saving vs. standard care. Ongoing health economics analysis in diabetes is essential as new clinical data are published. Future analysis of clinical and cost outcomes in diabetes could be expected to look beyond the impact of interventions on HbA1c in isolation, as manufacturers seek to differentiate innovative products in the market. Furthermore, it is anticipated that the competitiveness in the market for interventions in diabetes will lead to future cost-effectiveness analysis taking more interest in comparisons of off-patent medication and generic, fixed-dose combination therapies.

Cost-effectiveness of intensified versus conventional multifactorial intervention in type 2 diabetes: results and projections from the Steno-2 study.

OBJECTIVE: To assess the cost-effectiveness of intensive versus conventional therapy for 8 years as applied in the Steno-2 study in patients with type 2 diabetes and microalbuminuria. RESEARCH DESIGN AND METHODS: A Markov model was developed to incorporate event and risk data from Steno-2 and account Danish-specific costs to project life expectancy, quality-adjusted life expectancy (QALE), and lifetime direct medical costs expressed in year 2005 Euros. Clinical and cost outcomes were projected over patient lifetimes and discounted at 3% annually. Sensitivity analyses were performed. RESULTS: Intensive treatment was associated with increased life expectancy, QALE, and lifetime costs compared with conventional treatment. Mean +/- SD undiscounted life expectancy was 18.1 +/- 7.9 years with intensive treatment and 16.2 +/- 7.3 years with conventional treatment (difference 1.9 years). Discounted life expectancy was 13.4 +/- 4.8 years with intensive treatment and 12.4 +/- 4.5 years with conventional treatment. Lifetime costs (discounted) for intensive and conventional treatment were euro45,521 +/- 19,697 and euro41,319 +/- 27,500, respectively (difference euro4,202). Increased costs with intensive treatment were due to increased pharmacy and consultation costs. Discounted QALE was 1.66 quality-adjusted life-years (QALYs) higher for intensive (10.2 +/- 3.6 QALYs) versus conventional (8.6 +/- 2.7 QALYs) treatment, resulting in an incremental cost-effectiveness ratio of euro2,538 per QALY gained. This is considered a conservative estimate because accounting prescription of generic drugs and capturing indirect costs would further favor intensified therapy. CONCLUSIONS: From a health care payer perspective in Denmark, intensive therapy was more cost-effective than conventional treatment. Assuming that patients in both arms were treated in a primary care setting, intensive therapy became dominant (cost- and lifesaving).

Exenatide versus insulin glargine in patients with type 2 diabetes in the UK: a model of long-term clinical and cost outcomes.

OBJECTIVES: The aim of this study was to evaluate the long-term clinical and economic outcomes associated with exenatide or insulin glargine, added to oral therapy in individuals with type 2 diabetes inadequately controlled with combination oral agents in the UK setting. METHODS: A published and validated computer simulation model of diabetes was used to project long-term complications, life expectancy, quality-adjusted life expectancy and direct medical costs. Probabilities of diabetes-related complications were derived from published sources. Treatment effects and patient characteristics were extracted from a recent randomised controlled trial comparing exenatide with insulin glargine. Simulations incorporated published quality of life utilities and UK-specific costs from 2004. Pharmacy costs for exenatide were based on 20, 40, 60, 80 and 100% of the US value (as no price for the UK was available at the time of analysis). Future costs and clinical benefits were discounted at 3.5% annually. Sensitivity analyses were performed. RESULTS: In the base-case analysis exenatide was associated with improvements in life expectancy of 0.057 years and in quality-adjusted life expectancy of 0.442 quality-adjusted life years (QALYs) versus insulin glargine. Long-term projections demonstrated that exenatide was associated with a lower cumulative incidence of most cardiovascular disease (CVD) complications and CVD-related death than insulin glargine. Using the range of cost values, evaluation results showed that exenatide is likely to fall in a range between dominant (cost and life saving) at 20% of the US price and cost-effective (with an ICER of 22,420 pounds per QALY gained) at 100% of the US price, versus insulin glargine. CONCLUSIONS: Based on the findings of a recent clinical trial, long-term projections indicated that exenatide is likely to be associated with improvement in life expectancy and quality-adjusted life expectancy compared to insulin glargine. The results from this modelling analysis suggest that that exenatide is likely to represent good value for money by generally accepted standards in the UK setting in individuals with type 2 diabetes inadequately controlled on oral therapy.

A French cost-consequence analysis of the renoprotective benefits of irbesartan in patients with type 2 diabetes and hypertension.

OBJECTIVES: We performed a cost-consequence analysis in a French setting of the renoprotective benefit of irbesartan in hypertensive type 2 diabetes patients over a 25-year period. RESEARCH DESIGN AND METHODS: A previously published Markov model simulated progression from microalbuminuria to overt nephropathy, doubling of serum creatinine, end-stage renal disease and death. Three treatment strategies with analogous blood pressure control were compared: (A) control--conventionally medicated antihypertensive therapy (excluding angiotensin converting enzyme inhibitors, other angiotensin-2-receptor antagonists and dihydropyridine calcium channel blockers) initiated at microalbuminuria; (B) early irbesartan--(300 mg daily added to control, initiated with microalbuminuria) and (C) late irbesartan--(300 mg daily, initiated with overt nephropathy). Probabilities came from the Irbesartan in Reduction of Microalbuminuria-2 study, Irbesartan in Diabetic Nephropathy Trial and other sources. Clinical and economic outcomes were projected over 25 years. Annual discount rates were 3%. RESULTS: Compared to control, early use of irbesartan added (mean +/- standard deviation) 1.51 +/- 0.08 undiscounted life years (discounted: 0.94 +/- 0.05 years), while late irbesartan added 0.07 +/- 0.01 (0.04 +/- 0.01) years/patient. Early irbesartan added 1.03 +/- 0.06 discounted quality-adjusted life years (QALYs), while late irbesartan added 0.06 +/- 0.01 QALYs. Early and late irbesartan treatments were projected to save 22,314 +/- 1273 euro and 6619 +/- 820 euro/patient, respectively versus control. Sensitivity analysis showed that even over short time horizons both irbesartan treatments were superior to the control group. CONCLUSIONS: In France, early irbesartan treatment improved quality and length of life and reduced costs in hypertensive patients with type 2 diabetes and microalbuminuria. Late irbesartan therapy is beneficial, but earlier irbesartan leads to better outcomes.

Counting the costs of overweight and obesity: modeling clinical and cost outcomes.

OBJECTIVE: To quantify changes in clinical and cost outcomes associated with increasing levels of body mass index (BMI) in a US setting. RESEARCH METHODS AND PROCEDURES: A semi-Markov model was developed to project and compare life expectancy (LE), quality-adjusted life expectancy (QALE) and direct medical costs associated with distinct levels of BMI in simulated adult cohorts over a lifetime horizon. Cohort definitions included age (20-65 years), gender, race, and BMI (24-45 kg m(-2)). Cohorts were exclusively male or female and either Caucasian or African-American. Mortality rates were adjusted according to these factors using published data. BMI progression over time was modeled. BMI-dependent US direct medical costs were derived from published sources and inflated to year 2004 values. A third party reimbursement perspective was taken. QALE and costs were discounted at 3% per annum. RESULTS: In young Caucasian cohorts LE decreased as BMI increased. However, in older Caucasian cohorts the BMI associated with greatest longevity was higher than 25 kg m(-2). A similar pattern was observed in young adult African-American cohorts. A survival paradox was projected in older African-American cohorts, with some BMI levels in the obese category associated with greatest longevity. QALE in all four race/gender cohorts followed similar patterns to LE. Sensitivity analyses demonstrated that simulating BMI progression over time had an important impact on results. Direct costs in all four cohorts increased with BMI, with a few exceptions. CONCLUSIONS: Optimal BMI, in terms of longevity, varied between race/gender cohorts and within these cohorts, according to age, contributing to the debate over what BMI level or distribution should be considered ideal in terms of mortality risk. Simulating BMI progression over time had a substantial impact on health outcomes and should be modeled in future health economic analyses of overweight and obesity.

Cost-effectiveness of irbesartan in diabetic nephropathy: a systematic review of published studies.

BACKGROUND: To review published studies on the cost-effectiveness of the use of irbesartan for treatment of advance overt nephropathy in patients with type 2 diabetes and hypertension. METHODS: Articles were identified based on a search of the PubMed databases using the keywords 'irbesartan', 'ESRD', 'cost-effectiveness', 'nephropathy' and 'costs', and by personal communication with the authors. Only studies published in the last 10 years were included. All costs data from the cost-effectiveness studies were inflated to 2003 Euros using published governmental conversion tables. RESULTS: Seven published studies were identified, spanning the following country settings: the US, Belgium and France, Germany, Hungary, Italy, Spain, and the UK. In each, the same pharmacoeconomic model was adapted using country-specific data to project and evaluate the clinical and cost outcomes of the treatment arms of the Irbesartan in Diabetic Nephropathy Trial (IDNT) (irbesartan, amlodipine or standard blood pressure control). Mean time to onset of ESRD was 8.23 years for irbesartan, 6.82 years for amlodipine and 6.88 years for the control (values were the same for Belgium, France, Germany, Hungary, Italy and Spain as transition probabilities for progression to ESRD were all derived from the IDNT). Mean cumulative incidence of ESRD was 36% with irbesartan, 49% with amlodipine and 45% with control treatment. Treatment with irbesartan was projected to improve life expectancy compared to both amlodipine and control in all seven published studies. Analysis of total lifetime costs showed that irbesartan treatment was cost saving compared to the other two treatment regimens, due to the associated reduction in ESRD cases. Cost savings with irbesartan became evident very early; after 2-3 years of treatment in most settings. CONCLUSIONS: Modelling studies based on the IDNT published to date suggest that irbesartan treatment in patients with type 2 diabetes, hypertension and advanced nephropathy is both life- and cost-saving compared to amlodipine or control.

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

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

Identification of a nef allele that causes lymphocyte activation and acute disease in macaque monkeys.

Residues 17 and 18 in nef of SIVmac239 were changed from RQ to YE to create a translated sequence of SRPSGDLYERLLRARGETYGRLLGEVEDGYSQSP from residues 10-43. The YXXL motifs in this context match very well with consensus sequences for SH2 binding domains and are similar to ones present in nef of the acutely lethal pathogen SIVpbj14. The YE variant of SIVmac239, unlike SIVmac239 but like SIVpbj14, replicated well in resting peripheral blood mononuclear cell cultures, caused extensive T lymphocyte activation, and produced an acute disease in rhesus and pigtailed monkeys characterized by severe diarrhea, rash, and extensive lymphoid proliferation in the gastrointestinal tract. The YEnef gene transformed NIH 3T3 cells in culture. Both 239nef and YEnef were found to associate with src in cotransfected COS cells, and both 60 kDa src and 34 kDa nef were phosphorylated at tyrosine in these cells. The extent of tyrosine phosphorylation of 239nef was considerably less than that of YEnef in these assays. These findings identify an important determinant of the SIVpbj14 phenotype, and they provide evidence of a role for nef in signal transduction and cellular activation.

Progression to AIDS in the absence of a gene for vpr or vpx.

Rhesus monkeys (Macaca mulatta) were experimentally infected with strains of simian immunodeficiency virus (SIV) derived from SIVmac239 lacking vpr, vpx, or both vpr and vpx genes. These auxiliary genes are not required for virus replication in cultured cells but are consistently conserved within the SIVmac/human immunodeficiency virus type 2/SIVsm group of primate lentiviruses. All four rhesus monkeys infected with the vpr deletion mutant showed an early spike in plasma antigenemia, maintained high virus burdens, exhibited declines in CD4+ lymphocyte concentrations, and had significant changes in lymph node morphology, and two have died to date with AIDS. The behavior of the vpr deletion mutant was indistinguishable from that of the parental, wild-type virus. Rhesus monkeys infected with the vpx deletion mutant showed lower levels of plasma antigenemia, lower virus burdens, and delayed declines in CD4+ lymphocyte concentrations but nonetheless progressed with AIDS to a terminal stage. The vpr+vpx double mutant was severely attenuated, with much lower virus burdens and no evidence of disease progression. These and other results indicate that vpr provides only a slight facilitating advantage for wild-type SIVmac replication in vivo. Thus, progression to AIDS and death can occur in the absence of a gene for vpr or vpx.

A comparative study of higher primate foamy viruses, including a new virus from a gorilla.

Few foamy (spuma) retroviruses have been investigated in molecular detail, despite their previous isolation from several mamalian species, including ten neutralization serotypes from various primates. Here, we have studied a new gorilla foamy virus (SFV-Gg) and investigated its functional and phylogenetic relationship to the human (HFV) and other primate foamy viruses, including that recently described in orangutans (SFV-11). Nucleotide sequencing of PCR products obtained from the R/U5 region of the LTR, gag, and pol genes revealed a close relationship between HFV and three chimpanzee isolates (SFV-6, SFV-7, and SFV-cpz). The SFV-Gg, SFV-11, rhesus macaque (SFV-1), and African green monkey (SFV-3) isolates were more divergent. To explore functional relationships, primate foamy virus transactivation of HFV LTR driven beta-galactosidase expression in a newly constructed cell line, BHLL, was investigated. HFV, SFV-6, and SFV-7 potently transactivated HFV LTR driven lacZ gene expression, SFV-Gg induced expression approximately 10-fold less efficiently, and SFV types 1, 2, 3, and 11 did not significantly transactivate the HFV LTR. It was, thus, possible to assay serum neutralizing activity in SFV-infected primates against HFV, SFV-6, and SFV-7 by reduction of beta-galactosidase activity following infection of the indicator cell line. Sera from infected chimpanzees and gorillas neutralized, to varying degrees, each of these three viruses, whereas orangutan sera did not. Our results, based on DNA sequences and functional assays, support the conclusion that HFV is closely related to foamy viruses of chimpanzee origin.

Reactivity of primate sera to foamy virus Gag and Bet proteins.

In order to establish criteria for the serodiagnosis of foamy virus infections we investigated the extent to which sera from infected individuals of human and primate origin react with structural and non-structural virus proteins in immunoblot assays. Using lysates from infected cells as the source of virus antigen, antibodies were preferentially detected against the Gag proteins and the non-structural Bet protein. Both the Gag precursor molecules of 70 and 74K apparent M(r) and the cytoplasmic 60K M(r) Bet protein were found to be phosphorylated, the latter being synthesized in large amounts in infected cells. Rabbit antiserum raised against recombinant human foamy virus (HFV) Gag major capsid protein cross-reacted with foamy viruses of chimpanzee, gorilla, orang-utan, rhesus monkey and African green monkey origin. This was reflected by a broad cross-reactivity of the respective monkey sera to the Gag proteins of the various foamy virus isolates. Cross-reactivity of antisera against the Bet protein was restricted to viruses from man and the great apes. Recombinant Gag and Bet proteins expressed in prokaryotes or in insect cells were readily recognized by foamy virus-positive primate sera. Screening serum samples from chimpanzees with HFV Gag and Bet proteins expressed by recombinant baculoviruses revealed that 18 out of 35 (52%) were positive for Gag antibodies. Of these, 13 (72%) showed antibodies against the Bet protein, indicating that Bet antigen is of value in serological screening for foamy virus infections.

The role of upstream U3 sequences in the pathogenesis of simian immunodeficiency virus-induced AIDS in rhesus monkeys.

The nef reading frame overlaps about 70% of the U3 region of the 3' long terminal repeat (LTR) in primate lentiviruses. We investigated the functional role of these overlapping U3 sequences by analyzing the properties of three mutant forms of the pathogenic SIVmac239 clone. In mutant UScon, 90 of 275 bp in the upstream sequences (US) of U3 were changed in a conservative fashion without changing the predicted nef coding sequence. In mutant USnon, 101 of 275 bp in this region were changed in a nonconservative fashion, again without changing the predicted nef coding sequence. In mutant delta US, 275 bp in this region were deleted. Full-size, immunoreactive nef protein was synthesized in cells infected with the UScon and USnon mutants. The USnon and delta US mutants replicated with similar kinetics and to similar extents as wild-type, parental SIVmac239 in primary rhesus monkey peripheral blood mononuclear cell (PBMC) cultures. The UScon mutant replicated with slightly delayed kinetics in rhesus monkey PBMC cultures. In the CEMx174 cell line, the delta US mutant replicated similarly to the wild type, but the UScon and USnon mutants replicated with significantly delayed kinetics. Analysis of LTR-driven chloramphenicol acetyltransferase (CAT) activity and the effects of 5-azacytidine on virus replication suggested that the growth defect of the point mutants in CEMx174 cells was due in whole or in part to the introduction of multiple CG methylation sites in proviral DNA. Rhesus monkeys were experimentally infected with the UScon and USnon mutants, and the characteristics of the infection were compared with those of the parental SIVmac239. Analysis of the levels of plasma antigenemia, virus load, and CD4+ cells in PBMC revealed no decreased virulence of the mutant viruses. Analysis of lymph node biopsies taken from animals that received mutant viruses revealed histologic changes and levels of virus expression indistinguishable from those of the wild type. Furthermore, the wild-type behavior of the mutant viruses in rhesus monkeys occurred without any specific reversional events through at least 20 weeks of infection. These results, and the recent results of Kirchhoff et al. (F. Kirchoff, H. W. Kestler III, and R. C. Desrosiers, J. Virol. 68:2031-2037, 1994), suggest that these upstream sequences in U3 are primarily or exclusively nef coding sequence.

High-titer immune responses elicited by recombinant vaccinia virus priming and particle boosting are ineffective in preventing virulent SIV infection.

Eighteen rhesus monkeys were vaccinated with recombinant vaccinia viruses expressing SIVmac antigens in 3 separate rounds of experiments. Twelve of the monkeys were primed with a trivalent vaccinia virus recombinant expressing Gag, Pol, and Env polypeptides that can assemble into SIV pseudovirion particles and boosted with SIV particles in adjuvant. Four of the monkeys were primed with different vaccinia virus recombinants expressing env or gag+env followed by SIV particle boosts; two received vaccinia virus recombinants alone (env or env+gag). Despite the induction of vigorous immune responses, 17 of 18 rhesus monkeys became infected on challenge with a low dose of virulent SIVmac. The single protected animal was one of three challenged with homologous cloned SIV exactly matched to the clone used for construction of trivalent vaccinia virus recombinant and particles. Vaccination may have diminished SIV burdens and rates of CD4+ cell declines in some of the animals, but vaccinated/challenge/infected animals eventually developed fatal disease similar to control animals. These results highlight the extreme difficulty in achieving vaccine protection against virulent SIVmac infection even under idealized laboratory conditions.

Disseminated B virus infection in a cynomolgus monkey.

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

Targeted inhibition of immunodeficiency virus replication in lymphocytes through retroviral mediated gene transfer.

To test the feasibility of gene therapy for AIDS patients, an animal model is needed to evaluate the efficacy and safety of this approach. Antiviral genes (encoding antisense RNA or viral protein) derived from Simian immunodeficiency virus (SIV) were efficiently targeted into CD4+ lymphocytes through retroviral-mediated gene transfer. After challenging with infectious viruses, the transduced lymphocytes that received antiviral genes were not only protected from SIV infection, but also from infection with HIV, for at least 25 days. Furthermore, little or no cytolytic effect (syncytium formation) was observed in the protected cells. These data demonstrated that SIV or HIV replication could be effectively blocked by antisense sequence(s) or negative dominant factors which were introduced into targeted cells through retroviral-mediated gene transfer.

Protective effects of a live attenuated SIV vaccine with a deletion in the nef gene.

Vaccine protection against the human immunodeficiency virus (HIV) and the related simian immunodeficiency virus (SIV) in animal models is proving to be a difficult task. The difficulty is due in large part to the persistent, unrelenting nature of HIV and SIV infection once infection is initiated. SIV with a constructed deletion in the auxiliary gene nef replicates poorly in rhesus monkeys and appears to be nonpathogenic in this normally susceptible host. Rhesus monkeys vaccinated with live SIV deleted in nef were completely protected against challenge by intravenous inoculation of live, pathogenic SIV. Deletion of nef or of multiple genetic elements from HIV may provide the means for creating a safe, effective, live attenuated vaccine to protect against acquired immunodeficiency syndrome (AIDS).

Genetic analysis of simian virus 40 from brains and kidneys of macaque monkeys.

Simian virus 40 (SV40) was isolated from the brains of three rhesus monkeys and the kidneys of two other rhesus monkeys with simian immunodeficiency virus-induced immunodeficiency. A striking feature of these five cases was the tissue specificity of the SV40 replication. SV40 was also isolated from the kidney of a Taiwanese rock macaque with immunodeficiency probably caused by type D retrovirus infection. Multiple full-length clones were derived from all six fresh SV40 isolates, and two separate regions of their genomes were sequenced: the origin (ori)-enhancer region and the coding region for the carboxy terminus of T antigen (T-ag). None of the 23 clones analyzed had two 72-bp enhancer elements as are present in the commonly used laboratory strain 776 of SV40; 22 of these 23 clones were identical in their ori-enhancer sequences, and these had only a single 72-bp enhancer element. We found no evidence for differences in ori-enhancer sequences associated with tissue-specific SV40 replication. The T-ag coding sequence that was analyzed was identical in all clones from kidney. However, significant variation was observed in the carboxy-terminal region of T-ag in SV40 isolated from brain tissues. This sequence variation was located in a region previously reported to be responsible for SV40 host range in cultured cell lines. Thus, SV40 appears to be an opportunistic pathogen in the setting of simian immunodeficiency virus-induced immunodeficiency, similarly to JC virus in human immunodeficiency virus-infected humans, the enhancer sequence organization generally attributed to SV40 is not representative of natural SV40 isolates, and sequence variation near the carboxy terminus of T-ag may play a role in tissue-specific replication of SV40.

Differences in neutralization of simian lentivirus (SIVMAC) in lymphocyte and macrophage cultures.

Comparison of neutralization of SIVmac251 in primary macrophage cultures with neutralization in lymphocytes (CEM174 cells) showed that neutralizing antibodies induced by SIV251 in infected rhesus macaques protected both macrophages and T lymphocytes against infection when the virus was preincubated with the antibodies. In macrophages, the neutralizing antibodies also protected against infection when added 1 hour after the virus. Addition of antisera to macrophages between 24 and 48 hours after virus inoculation resulted in infection with continuous release of small amounts of p24 into the supernatant fluids but these antibody-treated cultures failed to exhibit cytopathic virus replication. In contrast, the same neutralizing antisera did not protect lymphocytes against infection and subsequent cytopathic replication of the virus when added only 1 hour after virus inoculation. This distinction in the effect that neutralizing antibodies had on the development of cytopathic infection in lymphocytes and macrophages when added after virus inoculation, suggests that they could alter the dynamics of virus replication and therefore the pathogenesis of disease.

Cytokine influence on simian immunodeficiency virus replication within primary macrophages. TNF-alpha, but not GMCSF, enhances viral replication on a per-cell basis.

The control of HIV-1 or SIV replication within macrophages is probably influenced by a variety of viral and cellular factors. Of the cellular factors, the authors have studied cytokine influence on SIV replication in vitro utilizing simian alveolar macrophages and uncloned SIVmacMTV, a macrophage-tropic variant. The approach allowed quantification of viral replication on a per-cell basis. As reported for HIV-1 replication in macrophages, TNF-alpha significantly increased SIV production in these macrophage cultures. GMCSF also resulted in marked increases in SIV gag protein in culture supernatants. However, after correcting for differences in total cell numbers and numbers of gag-containing cells in the treated and untreated cultures, GMCSF did not upregulate SIV production on a per-cell basis. IL-6 increased SIV replication little if at all but induced significantly greater cytopathic changes in the treated cultures compared with infected, untreated cultures. In contrast, IFN-gamma greatly decreased replication. Our results for GMCSF, IFN-gamma, and IL-6 are in contrast to previously published reports of cytokine control of HIV-1 growth in target cells, and they stress the importance of cell number analyses and the use of primary cultures in the study of lentiviral replication kinetics in macrophages.