The differential short- and long-term effects of HIV-1 latency-reversing agents on T cell function

Despite the extraordinary success of HIV-1 antiretroviral therapy in prolonging life, infected individuals face lifelong therapy because of a reservoir of latently-infected cells that harbor replication competent virus. Recently, compounds have been identified that can reverse HIV-1 latency in vivo. These latency- reversing agents (LRAs) could make latently-infected cells vulnerable to clearance by immune cells, including cytolytic CD8+ T cells. We investigated the effects of two leading LRA classes on CD8+ T cell phenotype and function: the histone deacetylase inhibitors (HDACis) and protein kinase C modulators (PKCms). We observed that relative to HDACis, the PKCms induced much stronger T cell activation coupled with non-specific cytokine production and T cell proliferation. When examining antigen-specific CD8+ T cell function, all the LRAs except the HDACi Vorinostat reduced, but did not abolish, one or more measurements of CD8+ T cell function. Importantly, the extent and timing of these effects differed between LRAs. Panobinostat had detrimental effects within 10 hours of drug treatment, whereas the effects of the other LRAs were observed between 48 hours and 5 days. These observations suggest that scheduling of LRA and CD8+ T cell immunotherapy regimens may be critical for optimal clearance of the HIV-1 reservoir.

Neurocognitive effects of treatment interruption in stable HIV-positive patients in an observational cohort

OBJECTIVE

Prior studies have shown improved neurocognition with initiation of antiretroviral treatment (ART) in HIV. We hypothesized that stopping ART would be associated with poorer neurocognitive function.

METHODS

Neurocognitive function was assessed as part of ACTG 5170, a multicenter, prospective observational study of HIV-infected subjects who elected to discontinue ART. Eligible subjects had CD4 count >350 cells/mm(3), had HIV RNA viral load <55,000 cp/mL, and were on ART (>or=2 drugs) for >or=6 months. Subjects stopped ART at study entry and were followed for 96 weeks with a neurocognitive examination.

RESULTS

A total of 167 subjects enrolled with a median nadir CD4 of 436 cells/mm(3) and 4.5 median years on ART. Significant improvements in mean neuropsychological scores of 0.22, 0.39, 0.53, and 0.74 were found at weeks 24, 48, 72, and 96 (all p < 0.001). In the 46 subjects who restarted ART prior to week 96, no significant changes in neurocognitive function were observed.

CONCLUSION

Subjects with preserved immune function found that neurocognition improved significantly following antiretroviral treatment (ART) discontinuation. The balance between the neurocognitive cost of untreated HIV viremia and the possible toxicities of ART require consideration.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that discontinuing ART is associated with an improvement in 2 neuropsychological tests (Trail-Making Test A & B and the Wechsler Adult Intelligence Scale-Revised Digit Symbol subtest) for up to 96 weeks. Resuming ART was not associated with a decline in these scores for up to 45 weeks.

A prospective evaluation of the effect of atazanavir on the QTc interval and QTc dispersion in HIV-positive patients

BACKGROUND

Atazanavir (ATV), an HIV protease inhibitor (PI) that may be preferred for the treatment of HIV-infected patients with cardiovascular comorbidities because of its favourable effects on plasma lipids, has been associated with cardiac rhythm disturbances.

OBJECTIVE

To quantify the effect of ATV on corrected QT (QTc) and QTc dispersion (QTd), markers of the potential for cardiac dysrhythmia, in patients switching from other PIs to ATV.

METHODS

In this prospective, single-centre, open-label study, 12-lead electrocardiograms were performed for subjects at baseline, 2 h after the first dose of ATV, and 1 month after initiation of ATV.

RESULTS

Twenty-one patients (19 received ritonavir-boosted ATV) completed the study. There was a trend towards an increase in the QTc at 2 h after the first dose [mean+/-standard deviation 3.19+/-8.0 ms; 95% confidence interval (CI) -0.47 to 6.85 ms; P=0.084]. There was no difference between QTc values at baseline and at 1 month (-1.5+/-8.75 ms; 95% CI -5.50 to 2.46; P=0.43). There was a nonsignificant decrease in the QTd between baseline and 2 h (-5.1+/-15.19 ms; 95% CI -13.22 to 2.96; P=0.197) and between baseline and 1 month (-0.61+/-15.04 ms; 95% CI -8.1 to 6.87; P=0.865). A significant increase in the PR interval (7.4+/-10.7 ms; 95% CI 2.5 to 12.25 ms; P=0.005) was observed at 1 month.

CONCLUSIONS

The use of ATV did not result in increases in the QTc interval or QTd. However, PR interval monitoring may be warranted in patients with underlying heart block or those treated with atrioventricular nodal blocking agents.

A pilot study of the use of mycophenolate mofetil as a component of therapy for multidrug-resistant HIV-1 infection

Mycophenolic acid (MPA) increases the activity of both abacavir (ABC) and didanosine (ddI) in vitro against wild-type and multinucleoside-resistant HIV. We treated 7 patients with diagnosed AIDS who did not respond to eight or more antiretroviral therapies in an open label pilot study with mycophenolate mofetil (MMF), ABC, ddI, amprenavir (APV), and ritonavir (RTV), with or without efavirenz (EFV). Therapy was well tolerated despite the patients' advanced disease states. No significant decline in lymphocyte or other blood counts was observed. Median HIV RNA was 5.26 log10 copies/ml at entry, 4.53 log10 copies/ml at 4 weeks, and 5.13 log10 copies/ml at 16 weeks. Median CD4+ count was 34 cells/microl at entry and 39 cells/microl at 16 weeks of therapy. CD4+ counts increased further in five study subjects on extended therapy to 25 weeks (median 27 cells/microl at entry, 66 cells/microl at close), despite loss of virologic suppression in 4 of 5 cases. MPA can induce apoptosis in lymphocytes in vitro. However despite viral rebound, cell surface markers of apoptosis and activation declined in total CD3+ cells and CD3+/CD4+ cells twofold to fourfold in 4 of 5 adherent study subjects at 16 weeks, reaching levels comparable with those found in seronegative donors. Although low-dose MMF appears safe in late-stage HIV disease, this study did not demonstrate virologic efficacy. Higher doses of MMF may be more effective. With careful monitoring of toxicities and pharmacokinetics, MMF deserves further testing in HIV therapy.

The human factors YY1 and LSF repress the human immunodeficiency virus type 1 long terminal repeat via recruitment of histone deacetylase 1

Enigmatic mechanisms restore the resting state in activated lymphocytes following human immunodeficiency virus type 1 (HIV-1) infection, rarely allowing persistent nonproductive infection. We detail a mechanism whereby cellular factors could establish virological latency. The transcription factors YY1 and LSF cooperate in repression of transcription from the HIV-1 long terminal repeat (LTR). LSF recruits YY1 to the LTR via the zinc fingers of YY1. The first two zinc fingers were observed to be sufficient for this interaction in vitro. A mutant of LSF incapable of binding DNA blocked repression. Like other transcriptional repressors, YY1 can function via recruitment of histone deacetylase (HDAC). We find that HDAC1 copurifies with the LTR-binding YY1-LSF repressor complex, the domain of YY1 that interacts with HDAC1 is required to repress the HIV-1 promoter, expression of HDAC1 augments repression of the LTR by YY1, and the deacetylase inhibitor trichostatin A blocks repression mediated by YY1. This novel link between HDAC recruitment and inhibition of HIV-1 expression by YY1 and LSF, in the natural context of a viral promoter integrated into chromosomal DNA, is the first demonstration of a molecular mechanism of repression of HIV-1. YY1 and LSF may establish transcriptional and virological latency of HIV, a state that has recently been recognized in vivo and has significant implications for the long-term treatment of AIDS.

USF/c-Myc enhances, while Yin-Yang 1 suppresses, the promoter activity of CXCR4, a coreceptor for HIV-1 entry

Transcription factors USF1 and USF2 up-regulate gene expression (i.e. , HIV-1 long terminal repeats) via interaction with an E box on their target promoters, which is also a binding site for c-Myc. The c-Myc oncoprotein is important in control of cellular proliferation and differentiation, while Yin-Yang 1 (YY1) has been shown to control the expression of a number of cellular and viral genes. These two proteins physically interact with each other and mutually inhibit their respective biological functions. In this study, we show that USF/c-Myc up-regulates, while YY1 down-regulates the promoter activity of CXCR4, a coreceptor for T cell-tropic HIV-1 entry. We have identified an E box around -260 and a YY1 binding site around -300 relative to the transcription start site. Mutation of the E box abolished USF/c-Myc-mediated up-regulation of CXCR4 promoter activity, and mutation of the YY1 binding site was associated with unresponsiveness to YY1-mediated inhibition. These data suggest that USF/c-Myc and YY1 may play an important role in the HIV-1-replicative cycle, by modulating both the viral fusion/entry process and viral expression.

In Vitro Techniques for Studies of HIV-1 Promoter Activity

A rather unique feature of the human immunodeficiency virus type-1 (HIV-1) is the structural complexity of the regulatory sequences located in the long-terminal repeat (LTR) promoter region and the number of cellular and viral transcription factors known to interact with these sequences and modulate HIV gene expression see ref. 1). The HIV-1 LTR can be schematically divided into four functional regions: (1) the negative regulatory element (NRE) encompassing nuceotides -350 to -190 with respect to the transcription start site; (2) the enhancer (-140 to-81), containing two binding sites for the transcription factor NFκB; (3) the basal promoter (located between -80 and +1), including a typical TATAA box and three binding sites for the transcription factor Sp1; and (4) the trans-activation response (TAR) element, a bulged stem-and-loop structure present in the nascent RNA (+1 to +59) transcript that provides a binding site for Tat activation of HIV-1 transcription. In addition, a novel regulatory DNA element, named IST (Initiator of Short Transcripts), has been shown to be present in the HIV-1 LTR (position (-)5 to (+)26), encompassing the binding site for transcription factors YY1 and late SV40 transcription factor (LSF, or CP-2, or LBP-1) (see refs. 2 and 3). IST directs the RNA polymerase II to synthesize short (59-61 nt), correctly initiated, nonpolyadenylated transcripts that prematurely terminate at the TAR stem-loop structure. The function of these transcripts remains unclear (see ref. 4).

Activation of CD8+ T lymphocytes through the T cell receptor turns on CD4 gene expression: implications for HIV pathogenesis

T cell activation through the T cell receptor is necessary to achieve a specific and effective immune response. We report here that stimulation of CD8+ T cells through the T cell receptor complex leads to de novo expression of the CD4 antigen on the cell surface that results in susceptibility of CD8+ T cells to HIV infection. In addition, activation of peripheral blood mononuclear cells from HIV-infected individuals results in the appearance of double-positive CD4+/CD8+ T cells, which become infected by endogenous HIV. HIV DNA sequences could be detected in uncultured and sorted mature CD3+CD8+ T cells from HIV+ individuals. These results suggest a new mechanism by which HIV could attack the immune system and may help to explain the CD8+ T cell defects in AIDS patients.

Repression of human immunodeficiency virus type 1 through the novel cooperation of human factors YY1 and LSF

A subpopulation of stably infected CD4+ cells capable of producing virus upon stimulation has been identified in human immunodeficiency virus (HIV)-positive individuals (T.-W. Chun, D. Finzi, J. Margolick, K. Chadwick, D. Schwartz, and R. F. Siliciano, Nat. Med. 1:1284-1290, 1995). Few host factors that directly limit HIV-1 transcription and could support this state of nonproductive HIV-1 infection have been described. YY1, a widely distributed human transcription factor, is known to inhibit HIV-1 long terminal repeat (LTR) transcription and virus production. LSF (also known as LBP-1, UBP, and CP-2) has been shown to repress LTR transcription in vitro, but transient expression of LSF has no effect on LTR activity in vivo. We report that both YY1 and LSF participate in the formation of a complex that recognizes the initiation region of the HIV-1 LTR. Further, we have found that these factors cooperate in the repression of LTR expression and viral replication. This cooperative function may account for the divergent effects of LSF previously observed in vitro and in vivo. Thus, the cooperation of two general cellular transcription factors may allow for the selective downregulation of HIV transcription. Through this mechanism of gene regulation, YY1 and LSF could contribute to the establishment and maintenance of a population of cells stably but nonproductively infected with HIV-1.

A 74-year-old man with persistent fevers

An elderly man with a history of extensive world travel presents with a chronic illness and fevers. The febrile illness has been present for eight years, and no diagnosis has been made despite extensive evaluation and testing. The differential diagnosis of this unusual case of fever of unknown origin is discussed.

Human transcription factor YY1 represses human immunodeficiency virus type 1 transcription and virion production

The transcriptional activity of human immunodeficiency virus type 1 (HIV-1) is affected by many cellular factors. Homologies near the HIV-1 initiator region to the DNA-binding sequences of YY1, a multifunctional transcription factor known to regulate diverse viral and cellular promoters, suggested that YY1 might regulate HIV-1. Antibody to YY1 blocked the formation of complexes by HeLa cell nuclear extract and a DNA oligonucleotide encoding the HIV-1 initiator region. HIV-1 long terminal repeat (LTR) expression, as measured the expression of a transfected LTR-CAT reporter gene, was repressed more than 12-fold by the cotransfection of a YY1 expression vector. HIV-1 production by both COS-1 and CEM cells after transfection of an infectious molecular HIV-1 clone was repressed 7- to 20-fold by cotransfection of a YY1 expression vector. HIV-1 production was also decreased threefold in a CD4-positive lymphocyte cell line chronically infected with HIV-1 (8E5) after transfection of YY1. In situ hybridization studies confirmed that YY1 reduced HIV-1 RNA expression. YY1 may play an important role in the regulation of HIV-1 LTR expression in vivo and virus production by infected cells.

Induction and enhancement of immune responses to herpes simplex virus type 2 in humans by use of a recombinant glycoprotein D vaccine

A vaccine for a chronic or recurrent viral infection should induce immune responses that protect against primary disease or that augment preexisting defenses sufficiently to diminish the likelihood of disease recurrence or progression. Such a vaccine was sought for genital herpes, a sexually transmitted infection of epidemic proportion. Vaccine containing recombinant herpes simplex virus type 2 glycoprotein D expressed in CHO cells was given repeatedly and safely to 24 human volunteers. In previously uninfected subjects, the vaccine induced primary antigen-specific and neutralizing antibody responses nearing or exceeding those seen at entry in subjects with genital herpes. Primary cellular immune responses were also evoked. Vaccination of previously seropositive subjects boosted antibody titers to levels that remained, for > or = 1 year, severalfold above those attained in recurrent genital herpes. Either the quantity or mode of presentation of antigen permitted this vaccine to exhibit previously unachieved immunogenicity, which may prove adequate for antiviral immunoprophylaxis or treatment of genital herpes.

A cutaneous lesion in a patient with AIDS: an unusual presentation of infection due to Mycobacterium avium complex

A patient with AIDS developed a purplish, necrotic skin lesion followed by fevers, constitutional symptoms, and watery diarrhea. Stains of samples from the skin lesion and of stool and bone marrow revealed acid-fast bacilli, and Mycobacterium avium was isolated from cultures of these specimens and blood. With the initiation of multiagent oral antimycobacterial therapy, the patient's symptoms abated and the cutaneous lesion reepithelialized. We believe this lesion to be a manifestation of disseminated infection due to Mycobacterium avium complex (MAC). As the population of patients with AIDS who have CD4 cell counts of < 100/mm3 increases, new and unusual manifestations of disseminated MAC infection can be expected. New oral agents with increased activity against MAC may make early recognition and treatment of MAC infections more rewarding.

HSV-1 activation of HIV-1 transcription is augmented by a cellular protein that binds near the initiator element

A cellular DNA binding protein, which we term Leader Binding Protein-2 (LBP-2), binds near the transcriptional initiation site of the human immunodeficiency virus type 1 (HIV-1) promoter. This protein recognizes a motif similar to that of LBP-1, a putative repressor of transcription (Kato, H., et al., Science, 251, 1476-1479, 1991). LBP-2 is associated with transcriptional activation of HIV-1 by herpes simplex virus type 1 (HSV-1). Electrophoretic mobility shift assays showed that nuclear levels of this protein increase markedly following HSV-1 infection. Mutations of the LBP binding motif eliminate LBP-2 binding and interfere with HIV-1 activation by HSV-1. When inserted into an unrelated promoter, this motif confers transcriptional responsiveness to HSV-1 infection. Proteins that bind near the initiator element may be important regulators of HIV-1 gene expression.

Transactivation of the HIV-1 LTR by HSV-1 immediate-early genes

Herpes simplex virus type 1 (HSV-1) activates transcription from the long terminal repeat (LTR) promoter region of the human immunodeficiency virus type 1 (HIV-1). HSV-1 immediate-early (IE) genes ICP0 and ICP4 are thought to be important mediators of this process, which is known to involve the induction of the cellular activators NF-kappa B and Sp1. We demonstrate that ICP0 and ICP4 transactivation of the LTR is largely dependent on the presence of NF-kappa B and Sp1 binding sites. However, in Jurkat CD4-positive lymphocytes, HSV-1 activates LTR constructs lacking all NF-kappa B or Sp1 Binding sequences. This effect is still evident when all sequences upstream of the TATA motif are removed. Such enhancer-independent transactivation can be produced by cotransfection of ICP0 and ICP4. Thus HSV-1 IE genes transactivate the HIV-1 LTR both through the induction of NF-kappa B and Sp1 and through another as yet undefined cellular factor.

Trimethoprim-sulfamethoxazole prophylaxis in the management of chronic granulomatous disease

Long-term oral antimicrobial prophylaxis is accepted practice in the management of patients with chronic granulomatous disease (CGD). Reports of adverse outcome with trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis in other patient groups, and the recent occurrence of several severe fungal infections in patients followed at the National Institutes of Health (NIH), prompted a review of the NIH experience to examine the incidence of nonfungal and fungal infections in CGD patients with and without TMP-SMX prophylaxis. Prophylaxis decreased the incidence of nonfungal infections from 7.1 to 2.4 per 100 patient-months in patients with autosomal CGD (P less than .01) and from 15.8 to 6.9 infections per 100 patient-months (P = .06) in X-linked CGD patients. There was no significant change in the incidence of fungal infection in CGD patients on TMP-SMX (1.5-0.3 fungal infections/100 patient-months in autosomal CGD and 1.7-0.2 fungal infections/100 patient-months in X-linked CGD patients). TMP-SMX prophylaxis is indicated for the management of patients with CGD and decreases the incidence of non-fungal infections without increasing the incidence of fungal infections.

Effect of the weaver (wv) mutation on cerebellar neuron differentiation. I. Qualitative observations of neuron behavior in culture

A mutant gene dose-dependent inhibition of cerebellar granule cell neuron survival and neurite growth in dissociated cultures of cerebellum from 7-day-old heterozygous (+/wv) and homozygous (wv/wv) weaver mutant mice (M. Willinger, D. M. Margolis, and R. L. Sidman. (1981), J. Supramol. Struc. 17, 79-86) has previously been observed. In the present phase-contrast study time-lapse microcinematography was performed between 10 and 80 hr in culture to determine which properties of neurite growth and neuron migration are affected by weaver gene expression. Neurite growth in +/+ cultures is rapid and discontinuous. Neurites are thin and cylindrical. Membrane movement occurs only at the growth cone. Growth cone contact with cell aggregates or glial somas results in the cessation of cone advancement and the induction of translocation of the neuronal soma toward the astrocyte. In cultures of +/wv and wv/wv cerebellar cells, abnormal neurite growth is characterized by frequent neurite retractions and reinitiations. Neuronal somas and neurite shafts are motile during elongation. Homozygous neurites and cones are pleomorphic. Normal, +/wv, and wv/wv neurons undergo nuclear translocation. Like +/+ neurons, +/wv neurons migrate in response to growth cone-cell soma contact. In contrast, homozygous soma frequently reverse direction and migrate independently of cell contact. Granule cell death occurs with increasing frequency with increasing gene dosage. Neurons are unusually active prior to the rapid onset of cell death. In summary, the weaver mutation impairs granule cell differentiation by affecting neurite maintenance, membrane motility, and neuron morphology. The loss of viability appears to be independent of, or secondary to, these targets of gene action.

Effect of the weaver (wv) mutation on cerebellar neuron differentiation. II. Quantitation of neuron behavior in culture

Quantitative measurements of neuron behavior from time-lapse microcinematography of dissociated cultures of normal (+/+), heterozygous weaver (+/wv), and homozygous weaver (wv/wv) 7-day-old mouse cerebellum were performed to identify dose-dependent expressions of the mutant allele. Impaired neurite growth by granule cell neurons is a direct result of a dose-dependent increased frequency of neurite retraction and decreased rate of growth cone advancement. The number of retractions per neurite is 0.2, 1.0, and 2.0 for +/+, +/wv, and wv/wv neurites, respectively. Maximal rates of growth cone advancement are 1041, 443, and 250 micron/day for +/+, +/wv, and wv/wv granule cell neurites, respectively. Neurite initiation is actually increased in wv/wv cultures, though the neurites are not well sustained. The frequency of neurite initiation is 1.0, 1.7, and 2.2 for +/+, +/wv, and wv/wv neurons, respectively. Measurements of oscillations of somal position revealed that the cell center moves increasing distances over short times in proportion to the number of mutant genes. Nuclear translocation, the mode of somal migration in vivo and in vitro, occurs at the same frequency and rate in normal and mutant cultures. Weaver gene expression induces a cytopathology affecting various morphogenetic events rather than producing a block at a specific stage in granule cell differentiation. It is hypothesized that the dose-dependent impairments of cell motility reflect weaver gene action at the cell surface or cytoskeleton.

Neuronal differentiation in cultures of weaver (wv) mutant mouse cerebellum

In the present study we report for the first time a weaver (wv) gene dose effect on neuron survival and neurite formation in vitro. Dissociated cerebellar cells from postnatal 7- and 8-day-old normal (+/+), heterozygous weaver (+/wv) and homozygous weaver (wv/wv) mice were cultured as monolayers on poly-L-lysine coated glass. Cell death occurred rapidly in wv/wv cultures. Cell counts showed that less than 20% of the total neurons and neuronal precursors (identified by "birthday" radiolabeling techniques) survived by Day 3. Cell death was less extensive in +/wv cultures with 65% of the total neurons and 80% of the precursors surviving by Day 3. In contrast to wv/wv cultures, younger neurons survive better than the total population in +/wv cultures. The impairment of neurite formation over the first week is also proportional to the number of mutant genes as shown by quantitation of (a) the percentage of cells with neurites; (b) the percentage of cells with neurites of a given length class ith time; (c) the lengths of the longest process formed per cell. The mean longest neurite lengths obtained by computer digitization at 6 days in vitro were 41.8, 26.8, and 9.0 micron for +/+, +/wv, and wv/wv granule cells, respectively.

Upper gastrointestinal disease in chronic renal failure. A prospective evaluation

A prospective study was undertaken to determine the incidence of upper gastrointestinal disease in 85 chronic renal failure (CRF) patients on hemodialysis. Upper gastrointestinal x-rays were obtained for 83 patients, and enlarged gastric and duodenal folds were seen in 12% (10/83) and 42% (35/83) of the cases, respectively. Panendoscopy performed on 60 persons revealed gastritis in 22% (13/60), nodular duodenitis in 60% (35/60), and esophagitis in 13% (8/60). No peptic ulcers were identified either radiologically or endoscopically. Pathologic examination of mucosal biopsy specimens demonstrated gastritis in 46% (21/46) and duodenitis in 43% (22/51) of patients. A highly significant correlation was found between endoscopic and radiologic duodenitis (P less than .0001) and also between endoscopic and pathologic duodenitis. We have demonstrated a high incidence of mucosal inflammation but not ulcer disease in CRF patients. These lesions may predispose these individuals to gastrointestinal bleeding following renal transplantation.

Ischemic bowel disease following bilateral nephrectomy or renal transplant

In a 2 year period five patients developed pathologically proved ischemic bowel disease (IBD) following either renal transplantation or bilateral nephrectomy in preparations for transplantation. This entity accounted for 42% of all major gastrointestinal complications in this transplant unit. Three patients presented with abdominal pain and ileus, and two patients developed massive lower gastrointestinal hemorrhage. All five patients had nonocclusive ischemic disease because obstruction of a major intestinal vessel could not be documented in any case. Each patient was treated with bowel resection and three of the five patients survived. Although sepsis, shock, and large doses of immunosuppressive drugs have been implicated in predisposing such patients to IBD, these factors were not uniformly present in our cases. Blood volume redistribution with transient episodes of hypotension, especially during postoperative hemodialysis, may be significant. IBD in uremic patients can occur in the presence or absence of renal transplantation and may be the cause of massive intestinal hemorrhage in these individuals.