Factors Affecting Selection of TraineE for Neurointervention (FASTEN)

BACKGROUND AND IMPORTANCE

Neurointervention is a very competitive specialty in the United States due to the limited number of training spots and the larger pool of applicants. The training standards are continuously updated to ensure solid training experiences. Factors affecting candidate(s) selection have not been fully established yet. Our study aims to investigate the factors influencing the selection process.

METHODS

A 52-question survey was distributed to 93 program directors (PDs). The survey consisted of six categories: (a) Program characteristics, (b) Candidate demographics, (c) Educational credentials, (d) Personal traits, (e) Research and extracurricular activities, and (f) Overall final set of characteristics. The response rate was 59.1%. As per the programs' characteristics, neurosurgery was the most involved specialty in running the training programs (69%). Regarding demographics, the need for visa sponsorship held the greatest prominence with a mean score of 5.9 [standard deviation (SD) 2.9]. For the educational credentials, being a graduate from a neurosurgical residency and the institution where the candidate's residency training is/was scored the highest [5.4 (SD = 2.9), 5.4 (SD = 2.5), respectively]. Regarding the personal traits, assessment by faculty members achieved the highest score [8.9 (SD = 1)]. In terms of research/extracurricular activities, fluency in English had the highest score [7.2 (SD = 1.9)] followed by peer-reviewed/PubMed-indexed publications [6.4 (SD = 2.2)].

CONCLUSION

Our survey investigated the factors influencing the final decision when choosing the future neurointerventional trainee, including demographic, educational, research, and extracurricular activities, which might serve as valuable guidance for both applicants and programs to refine the selection process.

Eptifibatide use following emergent carotid stenting in acute anterior circulation ischemic stroke with tandem occlusion

BACKGROUND

Early revascularization of the extracranial internal carotid artery in acute anterior circulation ischemic stroke (ACIS) is feasible and may improve clinical outcome. When a stent is deployed, antithrombotic agents should be administered peri-procedurally to ensure stent patency. Our institution implemented a protocol for the use of eptifibatide as a means of maintaining stent patency in the treatment of ACIS associated with cervical internal carotid artery occlusion.

METHODS

Our internal database was queried for patients who received emergent endovascular therapy (ET) for ACIS with stent placement and eptifibatide administration between July 2016 and 2019.

RESULTS

Twenty nine patients met the study criteria. The etiology was large artery atherosclerosis in 26 cases. Two patients had a dissection (7%), and one had a carotid occlusion related to a recent carotid endarterectomy. Mean NIHSS was 14. Sixteen patients received IVrtPA. Extracranial-intracranial tandem occlusion (TO) was present in 21 of cases. All patients received an eptifibatide bolus followed by an infusion for approximately 24 hours post stent deployment. Head CT was obtained prior to initiation of oral dual antiplatelet therapy with aspirin and clopidogrel. Successful recanalization was achieved in all patients with no evidence of downstream embolization. Symptomatic intracerebral hemorrhage occurred in one patient. Stent occlusion occurred in two patients, only one of which was symptomatic. Favorable clinical outcome with mRS ≤ 2 at 3 months was achieved in seventeen patients.

CONCLUSIONS

The use of eptifibatide post procedure was associated with low risk of symptomatic intracranial hemorrhage, including in patients treated with rtPA.

Multicenter Postmarket Analysis of the Neuroform Atlas Stent for Stent-Assisted Coil Embolization of Intracranial Aneurysms

BACKGROUND AND PURPOSE

The Neuroform Atlas is a new microstent to assist coil embolization of intracranial aneurysms that recently gained FDA approval. We present a postmarket multicenter analysis of the Neuroform Atlas stent.

MATERIALS AND METHODS

On the basis of retrospective chart review from 11 academic centers, we analyzed patients treated with the Neuroform Atlas after FDA exemption from January 2018 to June 2019. Clinical and radiologic parameters included patient demographics, aneurysm characteristics, stent parameters, complications, and outcomes at discharge and last follow-up.

RESULTS

Overall, 128 aneurysms in 128 patients (median age, 62 years) were treated with 138 stents. Risk factors included smoking (59.4%), multiple aneurysms (27.3%), and family history of aneurysms (16.4%). Most patients were treated electively (93.7%), and 8 (6.3%) underwent treatment within 2 weeks of subarachnoid hemorrhage. Previous aneurysm treatment failure was present in 21% of cases. Wide-neck aneurysms (80.5%), small aneurysm size (<7 mm, 76.6%), and bifurcation aneurysm location (basilar apex, 28.9%; anterior communicating artery, 27.3%; and middle cerebral artery bifurcation, 12.5%) were common. A single stent was used in 92.2% of cases, and a single catheter for both stent placement and coiling was used in 59.4% of cases. Technical complications during stent deployment occurred in 4.7% of cases; symptomatic thromboembolic stroke, in 2.3%; and symptomatic hemorrhage, in 0.8%. Favorable Raymond grades (Raymond-Roy occlusion classification) I and II were achieved in 82.9% at discharge and 89.5% at last follow-up. mRS ≤2 was determined in 96.9% of patients at last follow-up. The immediate Raymond-Roy occlusion classification grade correlated with aneurysm location (P < .0001) and rupture status during treatment (P = .03).

CONCLUSIONS

This multicenter analysis provides a real-world safety and efficacy profile for the treatment of intracranial aneurysms with the Neuroform Atlas stent.

Abstract WP78: Outcomes After Off-Label Use of the Pipeline Embolization Device for Intracranial Aneurysms: a Multicenter Cohort Study

Objectives: The aim of this retrospective multicenter cohort study is to examine the outcomes of the Pipeline embolization device (PED) for the treatment of intracranial aneurysms outside of United States Food and Drug Administration approved (off-label) indications.

Methods: Data from aneurysm patients treated with the PED for off-label indications was pooled from four different centers. The primary endpoints were decline in modified Rankin Scale (mRS) by at least 1 point and angiographic aneurysm occlusion at follow-up.

Results: The study cohort was comprised of 109 patients. The mean aneurysm size was , 20% were located in the posterior circulation, and 12% were ruptured. The most common reasons for off-label use were aneurysm size (57%), location (11%) or both (12%). The mean follow-up was 9 months. Complete occlusion was achieved in 82% of cases at last angiographic follow-up and mRS decline was found in 18.8% of the cases. In the univariate analysis, only ruptured aneurysm presentation was significantly associated with mRS decline (p=0.016) (Table 1). In the multivariate analysis, size as the indication for off-label use was associated with higher odds of complete aneurysm occlusion on final angiography (Table 2).

Conclusion: The off-label use of the PED has a reasonable risk to benefit profile for appropriately selected aneurysms. Posterior circulation location and fusiform morphology do not appear to be associated with worse clinical or angiographic outcomes.

Concurrent stenting of multiple cerebrovascular stenotic lesions: technical note

INTRODUCTION

Until recently, the treatment of intracranial atherosclerosis has remained limited. Due to advances in endovascular technology and technique, angioplasty and stenting has become an accepted treatment for medically-refractory intracranial atherosclerosis. Patients with intracranial atherosclerosis frequently have multiple lesions, however, the clinical significance of each individual lesion is not always evident. In these instances the treating physician must decide which lesions should be managed conservatively, and which should be treated.

TECHNIQUE

Emphasizing decision-making, we describe a patient in whom 3 separate atherosclerotic lesions in the same vascular territory underwent endovascular treatment in one treatment session. Each of the lesions was treated with angioplasty and stent placement.

CONCLUSION

This may be a relatively safe and efficacious technique that allows for the treatment of multiple lesions without the risks associated with multiple cerebral angiograms.

Human herpesvirus 6A accelerates AIDS progression in macaques

Although HIV is the necessary and sufficient causative agent of AIDS, genetic and environmental factors markedly influence the pace of disease progression. Clinical and experimental evidence suggests that human herpesvirus 6A (HHV-6A), a cytopathic T-lymphotropic DNA virus, fosters the progression to AIDS in synergy with HIV-1. In this study, we investigated the effect of coinfection with HHV-6A on the progression of simian immunodeficiency virus (SIV) disease in pig-tailed macaques (Macaca nemestrina). Inoculation of HHV-6A resulted in a rapid appearance of plasma viremia associated with transient clinical manifestations and followed by antibody seroconversion, indicating that this primate species is susceptible to HHV-6A infection. Whereas animals infected with HHV-6A alone did not show any long-term clinical and immunological sequelae, a progressive loss of CD4(+) T cells was observed in all of the macaques inoculated with SIV. However, progression to full-blown AIDS was dramatically accelerated by coinfection with HHV-6A. Rapid disease development in dually infected animals was heralded by an early depletion of both CD4(+) and CD8(+) T cells. These results provide in vivo evidence that HHV-6A may act as a promoting factor in AIDS progression.

Lipopolysaccharide from an Escherichia coli htrB msbB mutant induces high levels of MIP-1 alpha and MIP-1 beta secretion without inducing TNF-alpha and IL-1 beta

OBJECTIVE

To identify a lipopolysaccharide (LPS) that retains the capacity to induce beta-chemokine secretion without the concomitant activation of pyrogenic cytokines.

METHODS

LPS was extracted from strain MLK986 (mLPS), an htrB1::Tn10, msbB::ocam mutant of Escherichia coli that is defective for lipid A synthesis, and from wild-type parent E coli strains, W3110 (wtLPS). The capacity of these LPS preparations to induce tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and macrophage inflammatory proteins 1 alpha (MIP-1 alpha) and MIP-1 beta was assessed using a human peripheral blood mononuclear cell (PBMC) activation assay.

RESULTS

Stimulation of PBMCs with mLPS did not induce measurable levels of pyrogenic cytokines TNF-alpha and IL-1 beta, whereas wtLPS induced high levels of these cytokines. Furthermore, mLPS antagonized the induction of TNF-alpha secretion by wtLPS. Nonetheless, mLPS retained a discrete agonist activity that induced MIP-1 alpha and MIP-1 beta secretion by PBMCs. This latter agonist activity appears to be unique to mLPS, since two previously documented LPS antagonists, Rhodobacter sphaeroides diphosphoryl lipid A and synthetic lipid IVA, did not induce MIP-1 alpha and MIP-1 beta secretion. Furthermore, synthetic lipid IVA was an antagonist of MIP-1 alpha and MIP-1 beta induction by mLPS.

CONCLUSION

These results show that mLPS exhibits a novel bipartite activity, being an effective antagonist of TNF-alpha induction by wtLPS, while paradoxically being an agonist of MIP-1 alpha and MIP-1 beta secretion.

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.

Role of the extracellular domain of human herpesvirus 7 glycoprotein B in virus binding to cell surface heparan sulfate proteoglycans

In an attempt to identify the human herpesvirus 7 (HHV-7) envelope protein(s) involved in cell surface binding, the extracellular domain of the HHV-7 glycoprotein B (gB) homolog protein was cloned and expressed as a fusion product with the Fc domain of human immunoglobulin G heavy chain gamma1 (gB-Fc) in an eukaryotic cell system. Indirect immunofluorescence followed by flow cytometric analysis revealed specific binding of gB-Fc to the membrane of SupT1 cells but not to other CD4+ T-lymphoblastoid cell lines, such as Jurkat or PM1, clearly indicating that gB-Fc did not bind to the CD4 molecule. This was also suggested by the ability of gB-Fc to bind to CD4-negative fibroblastoid Chinese hamster ovary (CHO) cells. The binding was abrogated by enzymatic removal of cell surface heparan sulfate proteoglycans by heparinase and heparitinase but not by treatment with condroitinase ABC. In addition, binding of the gB-Fc fusion protein to CHO cells was severely impaired in the presence of soluble heparin, as well as when heparan sulfate-deficient mutant CHO cells were used. Consistent with these findings, soluble heparin was found to block HHV-7 infection and syncytium formation in the SupT1 cell line. Although the CD4 antigen is a critical component of the receptor for the T-lymphotropic HHV-7, these findings suggest that heparin-like molecules also play an important role in HHV-7-cell surface interactions required for infection and that gB represents one of the HHV-7 envelope proteins involved in the adsorption of virus-to-cell surface proteoglycans.

Expression of CD26 does not correlate with the replication of macrophage-tropic strains of HIV-1 in T-cell lines

Strains of human immunodeficiency virus type 1 (HIV-1) differ significantly in both genetic content and biological properties. One of the earliest discovered differences between HIV-1 strains was divergence in the relative ability of different strains to replicate in either T-cell lines or monocytes/macrophages. This observation has led to the suggestion that molecules present on the surface of HIV-susceptible cells other than CD4 may interact with gp120 in facilitating the entry of HIV-1 into host cell populations. Several reports have suggested that CD26, a cell surface protease expressed on many cells of the immune system including some CD4+ T-cells and macrophage, may be an accessory molecule for HIV-1 entry. Recently, it has also been reported that the expression of high levels of CD26 correlates with the entry and replication of macrophage-tropic strains of HIV-1 in a T-cell line. In this report, we demonstrate that replication of macrophage-tropic strains of HIV-1 in T-cell lines is independent of CD26 expression. From this observation, we conclude that CD26 plays no role in the entry of HIV-1 into these cells.

Interference between human herpesvirus 7 and HIV-1 in mononuclear phagocytes

Human herpesvirus 7 (HHV-7) uses CD4 as a cellular membrane receptor and thereby interferes with infection of CD4+ T cells by HIV-1. We studied the interactions between HHV-7 and a macrophage-tropic HIV-1 isolate (HIV-1BaL) in terminally differentiated human peripheral blood monocyte-derived macrophages, another critical target for infection by HIV-1 in vivo. Exposure of macrophages to HHV-7 alone yielded no signs of virus replication or cytopathic effects. Nevertheless, when macrophages were pre-exposed to either live or UV-inactivated HHV-7 and subsequently infected with HIV-1BaL, a significant dose-dependent inhibition of HIV-1 replication was documented. At day 7 postinfection, the average level of HIV-1 p24 Ag in cultures from five different donors was reduced by 91.7 +/- 8.3% by pretreatment with live HHV-7 and by 91.8 +/- 8.2% by pretreatment with UV-inactivated HHV-7. Moreover, the synthesis of HIV-1 proviral DNA in macrophages pretreated with HHV-7 was completely inhibited during the early stages after infection, suggesting that HHV-7 blocks HIV-1 at the level of interaction with the CD4 receptor. Consistent with this concept, both macrophage and CD4+ T cell cultures with pre-established HIV-1 infection were not susceptible to inhibitory effects of HHV-7. The proliferative response of PBMC to mitogens was only marginally inhibited by exposure to HHV-7 before mitogen stimulation, indicating that the inhibition of HIV-1 infection was not due to a negative effect on cell proliferation. These data demonstrate that HHV-7 is a powerful inhibitor of HIV-1 infection in cells of the mononuclear phagocytic lineage, despite its inability to replicate actively in such cells.

Interference between human herpesvirus 7 and HIV-1 in mononuclear phagocytes

Human herpesvirus 7 (HHV-7) uses CD4 as a cellular membrane receptor and thereby interferes with infection of CD4+ T cells by HIV-1. We studied the interactions between HHV-7 and a macrophage-tropic HIV-1 isolate (HIV-1BaL) in terminally differentiated human peripheral blood monocyte-derived macrophages, another critical target for infection by HIV-1 in vivo. Exposure of macrophages to HHV-7 alone yielded no signs of virus replication or cytopathic effects. Nevertheless, when macrophages were pre-exposed to either live or UV-inactivated HHV-7 and subsequently infected with HIV-1BaL, a significant dose-dependent inhibition of HIV-1 replication was documented. At day 7 postinfection, the average level of HIV-1 p24 Ag in cultures from five different donors was reduced by 91.7 +/- 8.3% by pretreatment with live HHV-7 and by 91.8 +/- 8.2% by pretreatment with UV-inactivated HHV-7. Moreover, the synthesis of HIV-1 proviral DNA in macrophages pretreated with HHV-7 was completely inhibited during the early stages after infection, suggesting that HHV-7 blocks HIV-1 at the level of interaction with the CD4 receptor. Consistent with this concept, both macrophage and CD4+ T cell cultures with pre-established HIV-1 infection were not susceptible to inhibitory effects of HHV-7. The proliferative response of PBMC to mitogens was only marginally inhibited by exposure to HHV-7 before mitogen stimulation, indicating that the inhibition of HIV-1 infection was not due to a negative effect on cell proliferation. These data demonstrate that HHV-7 is a powerful inhibitor of HIV-1 infection in cells of the mononuclear phagocytic lineage, despite its inability to replicate actively in such cells.

Quantitative PCR for human herpesviruses 6 and 7

A quantitative PCR assay for the detection of human herpesvirus 6 (HHV-6) (variants A and B) and HHV-7 DNAs in clinical samples was developed. The assay uses a nonhomologous internal standard (IS) for each virus that is coamplified with the wild-type target sequence in the same vial and with the same pair of primers. This method allows for a correction of the variability of efficiency of the PCR technique. A standard curve is constructed for each experiment by coamplification of known quantities of the cloned HHV-6 or HHV-7 target templates with the respective IS. Absolute quantitation of the test samples is then achieved by determining the viral target/IS ratio of the hybridization signals of the amplification products and plotting this value against the standard curve. Using this assay, we quantitated the amount of HHV-6 or HHV-7 DNA in infected cell cultures and demonstrated an inhibitory effect of phosphonoformic acid on the replication of HHV-6 and HHV-7 in vitro. As the first clinical application of this procedure, we performed preliminary measurements of the loads of HHV-6 and HHV-7 in lymph nodes from patients with Hodgkin's disease and AIDS. Application of this quantitative PCR method should be helpful for elucidating the pathogenic roles of HHV-6 and HHV-7.

Infection of gamma/delta T lymphocytes by human herpesvirus 6: transcriptional induction of CD4 and susceptibility to HIV infection

Human herpesvirus 6 (HHV-6), a T-lymphotropic human herpesvirus, is a potentially immunosuppressive agent that has been suggested to play a role as a cofactor in the natural history of human immunodeficiency virus (HIV) infection. We studied the interactions between HHV-6 and gamma/delta T lymphocytes, a subset of T cells involved in the protective immune response against specific microorganisms. Polyclonal gamma/delta T cell populations, purified from the peripheral blood of healthy adults and activated in vitro with phytohemagglutinin, were exposed to HHV-6, strain GS (subgroup A), at the approximate multiplicity of infection (MOI) of 1. Signs of virus replication were detected as early as 72 h after infection, as documented by immunofluorescence, electron microscopy, and transmission of extracellular virus. Progression of the infection was associated with the appearance of typical cytomorphological changes and, eventually, massive cell death. In contrast, no signs of infection or cytopathic effects were detected after exposure of gamma/delta T lymphocytes to HHV-7, a CD4+ T-lymphotropic virus closely related to HHV-6. Polyclonal gamma/delta T cells displayed cytolytic activity against both autologous and heterologous target cells infected with HHV-6 and maintained this activity for at least 72 h after infection with HHV-6, despite the high MOI used. As previously documented in mature CD8+ alpha/beta T cells and natural killer cells, HHV-6 infection induced gamma/delta T lymphocytes to express de novo CD4 messenger RNA and protein, as detected by reverse transcriptase-polymerase chain reaction and fluorocytometry, respectively. Whereas purified CD4- gamma/delta T cell populations were per se refractory to HIV infection, they became susceptible to productive infection by HIV-1, strain IIIB, after induction of CD4 expression by HHV-6. These results demonstrate that gamma/delta T cells can be directly targeted and killed by a herpesvirus and may have implications for the potential role of HHV-6 in AIDS.

Detection of human herpesvirus 6 in plasma of children with primary infection and immunosuppressed patients by polymerase chain reaction

A sensitive and specific polymerase chain reaction method for the detection of human herpesvirus 6 (HHV-6) DNA in serum or plasma has been developed. In total, 157 human serum or plasma samples were studied. HHV-6 DNA was detected in 6 (85.7%) of 7 children with exanthem subitum, 3 (23.1%) of 13 bone marrow transplant (BMT) recipients, 4 (22.2%) of 18 human immunodeficiency virus (HIV)-infected patients, 1 (2.6%) of 39 patients with chronic fatigue syndrome, and none of 37 healthy adults. In the HHV-6-positive BMT recipients, HHV-6 plasma DNA was transiently detected during episodes of fever and respiratory infection. In children with exanthem subitum and in 1 HIV-infected patient, the HHV-6 strains were characterized as variant B, whereas variant A was detected in all other patients. Detection of viral DNA in serum or plasma is a marker of active infection that can be used to investigate the role of HHV-6 in human disease.

CD4 is a critical component of the receptor for human herpesvirus 7: interference with human immunodeficiency virus

In this study, we demonstrate that the glycoprotein CD4, a member of the immunoglobulin superfamily, is a critical component of the receptor for human herpesvirus 7 (HHV-7), a recently discovered T-lymphotropic human herpesvirus. A selective and progressive downregulation of the surface membrane expression of CD4 was observed in human CD4+ T cells in the course of HHV-7 infection. Various murine monoclonal antibodies to CD4 and the recombinant soluble form of human CD4 caused a dose-dependent inhibition of HHV-7 infection in primary CD4+ T lymphocytes. Moreover, radiolabeled HHV-7 specifically bound to cervical carcinoma cells (HeLa) expressing human CD4. A marked carcinoma cells (HeLa) expressing human CD4. A marked reciprocal interference was observed between HHV-7 and human immunodeficiency virus (HIV), the retrovirus that causes the acquired immunodeficiency syndrome and also uses CD4 as a receptor. Previous exposure of CD4+ T cells to HHV-7 dramatically interfered with infection by both primary and in vitro-passaged HIV-1 isolates. Reciprocally, persistent infection with HIV-1 or treatment with the soluble form of gp120, the CD4-binding envelope glycoprotein of HIV-1, rendered CD4+ T cells resistant to HHV-7 infection. These data indicate that CD4 is critically involved in the receptor mechanism for HHV-7. The antagonistic effect between HHV-7 and HIV could be exploited to devise therapeutic approaches to AIDS.

In vitro susceptibility of Macaca nemestrina to human herpesvirus 6: a potential animal model of coinfection with primate immunodeficiency viruses

Human herpesvirus 6 (HHV-6), a lymphotropic herpesvirus, has been suggested as a potential cofactor in the acquired immunodeficiency syndrome (AIDS). Previous studies indicate that HHV-6 has a restricted range of susceptible species. In this study, we tested the in vitro susceptibility to HHV-6 of Macaca nemestrina (pig-tailed macaque), a species that has been found to be infectable by human immunodeficiency virus type I in vivo and that develops an AIDS-like syndrome following simian immunodeficiency virus (SIV) infection. Two different HHV-6 isolates (HHV-6GS and HHV-6BA), belonging to the two major HHV-6 variants (A and B, respectively), were employed. Both viruses induced a productive and cytopathic infection in phytohemagglutinin-stimulated peripheral blood T lymphocytes from M. nemestrina. In contrast, only HHV-6BA (variant B) was able to replicate in lymphocytes from Macaca mulatta (rhesus macaque). Moreover, HHV-6GS and SIVsmE660 productively coinfected individual M. nemestrina lymphocytes, resulting in increased levels of SIV replication. Genetic sequences of HHV-6 were not amplified by polymerase chain reaction from peripheral blood mononuclear cells of several adult M. nemestrina, suggesting that these animals, unlike humans, are not commonly infected by HHV-6, or a related virus. Thus, M. nemestrina may represent an optimal animal model system to investigate the in vivo interactions between HHV-6 and the primate immunodeficiency viruses.

Infection of natural killer cells by human herpesvirus 6

Natural killer (NK) cells are a functionally defined subset of non-T, non-B lymphocytes of bone marrow origin, which induce lysis of selected target cells, including neoplastic and virus-infected cells. The NK cell function provides an important mechanism of primary defence against viruses in vivo, as demonstrated by the occurrence of multiple herpesvirus infections in patients congenitally lacking NK cells. Here we show that functionally competent CD3- NK clones can be productively infected by human herpesvirus 6 (HHV-6), a T-lymphotropic DNA virus that may play a role in the acquired immunodeficiency syndrome (AIDS) and in the chronic fatigue syndrome, two disorders associated with a defective NK cell activity. The infection is cytopathic and induces de novo expression of CD4, an antigen not expressed within the NK lineage, thereby predisposing NK cells to infection by human immunodeficiency virus type 1 (HIV-1). These results provide evidence that a herpesvirus can directly target and kill NK cells, a potential strategy to suppress the natural anti-viral immunity of the host.