Probiotic Therapy During Vaccination Alters Antibody Response to Simian-Human Immunodeficiency Virus Infection But Not to Commensals

The induction of robust circulating antibody titers is a key goal of HIV-1 vaccination. Probiotic supplementation is an established strategy to enhance microbiota and boost antibody responses to vaccines. A recent study tested whether oral probiotics could enhance vaccine-specific mucosal immunity by testing vaccination with and without supplementation in a Rhesus macaque Simian-Human Immunodeficiency Virus challenge model. Although supplementation was not associated with protection, the effects of probiotics on immunity after infection were not examined. To address this question, we measured antibody titers to HIV Env and commensal bacteria in plasma from the vaccination/supplementation time points as well as after Simian-Human Immunodeficiency Virus (SHIV) acquisition. We found that a trend toward lower HIV Env-specific titers in the animals given probiotics plus vaccine became greater after SHIV infection. Significantly lower Immunoglobulin (Ig) A titers were observed in animals vaccinated and supplemented compared with vaccine alone due to a delay in antibody kinetics at week 2 postinfection. We observed no difference, however, in titers to commensal bacteria during probiotic supplementation or after SHIV infection. These results suggest that probiotic supplementation may be a strategy for reducing IgA-specific HIV antibodies in the plasma, a correlate associated with increased HIV infection in the RV144 clinical trial.

The Defenders of the Alveolus Succumb in COVID-19 Pneumonia to SARS-CoV-2 and Necroptosis, Pyroptosis and Panoptosis

Alveolar type II (ATII) pneumocytes as defenders of the alveolus are critical to repairing lung injury. We investigated the ATII reparative response in COVID-19 pneumonia, because the initial proliferation of ATII cells in this reparative process should provide large numbers of target cells to amplify SARS-CoV-2 virus production and cytopathological effects to compromise lung repair. We show that both infected and uninfected ATII cells succumb to tumor necrosis factor-α (TNF)-induced necroptosis, Bruton's tyrosine kinase (BTK)-induced pyroptosis and a new PANoptotic hybrid form of inflammatory cell death mediated by a PANoptosomal latticework that generates distinctive COVID-19 pathologies in contiguous ATII cells. Identifying TNF and BTK as the initiators of programmed cell death and SARS-CoV-2 cytopathic effects provides a rationale for early antiviral treatment combined with inhibitors of TNF and BTK to preserve ATII cell populations, reduce programmed cell death and associated hyperinflammation, and restore functioning alveoli in COVID-19 pneumonia.

Outpatient treatment of Covid-19 with metformin, ivermectin, and fluvoxamine and the development of Long Covid over 10-month follow-up

Background

Long Covid is an emerging chronic illness potentially affecting millions, sometimes preventing the ability to work or participate in normal daily activities. COVID-OUT was an investigator-initiated, multi-site, phase 3, randomized, quadruple-blinded placebo-controlled clinical trial (NCT04510194). The design simultaneously assessed three oral medications (metformin, ivermectin, fluvoxamine) using two by three parallel treatment factorial assignment to efficiently share placebo controls and assessed Long Covid outcomes for 10 months to understand whether early outpatient treatment of SARS-CoV-2 with metformin, ivermectin, or fluvoxamine prevents Long Covid.

Methods

This was a decentralized, remotely delivered trial in the US of 1,125 adults age 30 to 85 with overweight or obesity, fewer than 7 days of symptoms, and enrolled within three days of a documented SARS-CoV-2 infection. Immediate release metformin titrated over 6 days to 1,500mg per day 14 days total; ivermectin 430mcg/kg/day for 3 days; fluvoxamine, 50mg on day one then 50mg twice daily through 14 days. Medical-provider diagnosis of Long Covid, reported by participant by day 300 after randomization was a pre-specified secondary outcome; the primary outcome of the trial was severe Covid by day 14.

Result

The median age was 45 years (IQR 37 to 54), 56% female of whom 7% were pregnant. Two percent identified as Native American; 3.7% as Asian; 7.4% as Black/African American; 82.8% as white; and 12.7% as Hispanic/Latino. The median BMI was 29.8 kg/m2 (IQR 27 to 34); 51% had a BMI >30kg/m2. Overall, 8.4% reported having received a diagnosis of Long Covid from a medical provider: 6.3% in the metformin group and 10.6% in the metformin control; 8.0% in the ivermectin group and 8.1% in the ivermectin control; and 10.1% in the fluvoxamine group and 7.5% in the fluvoxamine control. The Hazard Ratio (HR) for Long Covid in the metformin group versus control was 0.58 (95% CI 0.38 to 0.88); 0.99 (95% CI 0.592 to 1.643) in the ivermectin group; and 1.36 in the fluvoxamine group (95% CI 0.785 to 2.385).

Conclusions

There was a 42% relative decrease in the incidence of Long Covid in the metformin group compared to its blinded control in a secondary outcome of this randomized phase 3 trial.

The Defenders of the Alveolus Succumb in COVID-19 Pneumonia to SARS-CoV-2, Necroptosis, Pyroptosis and Panoptosis

The alveolar type II (ATII) pneumocyte has been called the defender of the alveolus because, amongst the cell’s many important roles, repair of lung injury is particularly critical. We investigated the extent to which SARS-CoV-2 infection incapacitates the ATII reparative response in fatal COVID-19 pneumonia, and describe massive infection and destruction of ATI and ATII cells. We show that both type I interferon-negative infected ATII and type I-interferon-positive uninfected ATII cells succumb to TNF-induced necroptosis, BTK-induced pyroptosis and a new PANoptotic hybrid form of inflammatory cell death that combines apoptosis, necroptosis and pyroptosis in the same cell. We locate pathway components of these cell death pathways in a PANoptosomal latticework that mediates emptying and disruption of ATII cells and destruction of cells in blood vessels associated with microthrombi. Early antiviral treatment combined with inhibitors of TNF and BTK could preserve ATII cell populations to restore lung function and reduce hyperinflammation from necroptosis, pyroptosis and panoptosis.

Graphic

Highlights

In fatal COVID-19 pneumonia, the initial destruction of Type II alveolar cells by SARS-CoV-2 infection is amplified by infection of the large numbers of spatially contiguous Type II cells supplied by the proliferative reparative response.Interferon-negative infected cells and interferon-positive uninfected cells succumb to inflammatory forms of cell death, TNF-induced necroptosis, BTK-induced pyroptosis, and PANoptosis.All of the cell death pathway components, including a recently identified NINJ1 component, are localized in a PANoptosome latticework that empties in distinctive patterns to generate morphologically distinguishable cell remnants.Early combination treatment with inhibitors of SARS-CoV-2 replication, TNF and BTK could reduce the losses of Type II cells and preserve a reparative response to regenerate functional alveoli.

Spatial correction improves accuracy of catheter positioning during ablation of premature ventricular contractions: differences between ventricular outflow tracts and other localizations

BACKGROUND

Hybrid activation mapping is a novel tool to correct for spatial displacement of the mapping catheter due to asymmetrical contraction of myocardium during premature ventricular contractions (PVC). The aim of this study is to describe and improve our understanding of spatial displacement during PVC mapping as well as options for correction using hybrid activation mapping.

METHODS AND RESULTS

We analyzed 5798 hybrid mapping points in 40 acquired hybrid maps of 22 consecutive patients (age 63 ± 16 years, 45% female) treated for premature ventricular contractions (PVCs). Median PVC-coupling interval was 552 ms (IQR 83 ms). Spatial displacement was determined by measuring the dislocation of the catheter tip during PVC compared to the preceding sinus beat. Mean spatial displacement was 3.8 ± 1.5 mm for all maps. The displacement was 1.3 ± 0.4 mm larger for PVCs with non-outflow-tract origin compared to PVCs originating from the ventricular outflow tracts (RVOT/LVOT; p = 0.045). Demographic parameters, PVC-coupling-interval and chamber of origin had no significant influence on the extent of spatial displacement.

CONCLUSION

Ectopic activation of the ventricular myocardium during PVCs results in spatial displacement of mapping points that is significantly larger for PVCs with non-outflow-tract origin. The correction for spatial displacement may improve accuracy of radiofrequency current (RFC)-application in catheter ablation of PVCs.

Selective intracardiac sympathetic denervation acutely modulates left ventricular control

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Centre for Cardiovascular Research (DZHK)

Background

The sympathetic nervous system plays an integral role in cardiac physiology. Neuromodulation is emerging as a treatment option for ventricular arrhythmias, but selective intracardiac approaches are rare. Sympathetic nerve fibers innervating the left ventricle have been demonstrated to be amenable to transvenous catheter stimulation along the coronary sinus (CS).

Purpose

The aim of the present study was to modulate left ventricular control by selective sympathetic denervation using epicardial or standard catheter ablation for intracardiac axotomy at the level of the CS.

Methods

First, the impact of epicardial CS ablation on cardiac electrophysiology was studied in a Langendorff model of murine hearts (n=10 each, ablation and control). Second, the impact of transvenous, anatomically-driven axotomy by catheter-based radiofrequency ablation along the CS was evaluated in a healthy ovine in vivo model (n=8) before and during left stellate ganglion stimulation (LSGS).

Results

CS ablation for intracardiac sympathetic axotomy prolonged epicardial ventricular refractory period (VRP) without (41.8±8.4 ms vs. 53.0±13.5 ms; P=0.0487) and with beta1-2-adrenergic receptor blockade (47.8±2.8 ms vs. 73.1±5.0 ms; P=0.0009) and enhanced the increasing effect of beta1-2-adrenergic receptor blockade on epicardial VRP (∆VRP 6.3±7.0 ms vs. 20.0±7.5 ms; P=0.0045) in mice (Figure, A). Mean epicardial wave propagation velocity in the left ventricle was faster in ablated hearts than in controls (1.13±0.05 m/s vs. 1.00±0.02 m/s; P=0.0463), but did not differ in the right ventricle (1.15±0.05 m/s vs. 1.20±0.08 m/s; P=0.7938). Transvenous catheter ablation of the CS reduced systolic (SBP, 57.7±5.0 mmHg vs. 46.9±3.6 mmHg; P=0.0428) and diastolic blood pressure (DBP, 35.5±3.0 mmHg vs. 26.7±1.8 mmHg; P=0.0106) and diminished the blood pressure increase during LSGS in sheep (∆SBP 21.9±3.8 mmHg vs. 10.5±4.2 mmHg; P=0.0234; ∆DBP 9.0±1.9 mmHg vs. 3.0±1.2 mmHg; P=0.0391) (Figure, B, C). Cycle length remained unchanged by LSGS, both before (baseline 653.2±20.6 ms vs. LSGS 627.8±27.5 ms; P=0.2309) and after CS ablation (baseline 734.8±24.2 ms vs. LSGS 746.2±37.3 ms; P=0.7145).

Conclusions

Anatomically-driven axotomy targeting nerve fibers along the CS enables selective intracardiac sympathetic denervation resulting in acute modulation of left ventricular control.

Blue Monday: Co-occurring Stimulant Use and HIV Persistence Predict Dysregulated Catecholamine Synthesis

BACKGROUND

This longitudinal study examined whether co-occurring stimulant use and HIV disease processes predicted greater risk for depression via dysregulated metabolism of amino acid precursors for neurotransmitters.

METHODS

In total, 110 sexual minority men (ie, gay, bisexual, and other men who have sex with men) living with HIV who had biologically confirmed recent methamphetamine use were enrolled in a randomized controlled trial. The kynurenine/tryptophan (K/T) and phenylalanine/tyrosine (P/T) ratios were measured over 15 months to index dysregulated metabolism of amino acid precursors for serotonin and catecholamines. Markers of gut-immune dysregulation such as lipopolysaccharide binding protein and soluble CD14 (sCD14), HIV persistence in immune cells (ie, proviral HIV DNA), and stimulant use were examined as predictors. These bio-behavioral measures, including the K/T and P/T ratios, were also examined as predictors of greater risk for depression over 15 months.

RESULTS

Higher time-varying sCD14 levels (β = 0.13; P = 0.04) and time-varying detectable viral loads (β = 0.71; P < 0.001) were independent predictors of a higher K/T ratio. Time-varying reactive urine toxicology results for stimulants (β = 0.53; P < 0.001) and greater proviral HIV DNA at baseline (β = 0.34; P < 0.001) independently predicted an increased P/T ratio. Greater time-varying, self-reported methamphetamine use uniquely predicted higher odds of screening positive for depression (Adjusted Odds Ratio = 1.08; 95% confidence interval: 1.01 to 1.17).

CONCLUSIONS

Ongoing stimulant use and HIV persistence independently predict dysregulated metabolism of amino acid precursors for catecholamines, but this did not explain amplified risk for depression.

Outcome after practical isthmus ablation of scar-related atrial tachycardia guided by high-density mapping

Background

High-density mapping (HDM) has been found to precisely identify the practical isthmus of scar-related atrial tachycardia (AT) circuits. Since practical isthmuses have been found to be shorter than the usual anatomical isthmuses targeted ablation has been proposed. However, outcome data are sparse. Here we describe HDM-guided catheter ablation by targeting the practical isthmus in patients with scar-related ATs.

Methods and results

In 250 consecutive patients with scar-related ATs HDM-guided catheter ablation with the support of a 64-electrode mini-basket catheter has been performed. Most patients underwent a prior catheter ablation (98%) while 13% had a prior cardiac valve surgery and 6% an underlying congenital heart disease. A total of 355 ATs occurred in the index procedure, of which 64% had a macro-, 26% a micro-reentry and 10% a focal mechanism. The ATs had a mean cycle length of 304±4.3 ms and in 237 patients (95%) an acute termination into sinus rhythm was achieved. They were mainly located in the left atrium (72%) but also in the right atrium (25%), bi-atrially (5%) or in the CS (3%) (see figure). Targeting the practical isthmus revealed arrhythmia freedom in 53% of patients after a single procedure during a mid-term follow-up (median 489 days, range 95–1407 days). Freedom from any arrhythmia could be achieved in 74% of patients after multiple procedures and in 93% of patients after multiple procedures and optimal clinical therapy, including pharmaceutical or electrical cardioversion.

Conclusions

HDM-guided catheter ablation of the practical isthmus in patients with scar-related ATs leads to a high acute success rate. Nevertheless, multiple procedures are necessary in a relevant number of patients resulting in a low recurrence rate.

Funding Acknowledgement

Type of funding source: None

Candida rugosa lipase alters the gastrointestinal environment in wild-type mice

Diet and commercially available supplements can significantly impact the gut microbial composition; however, the effects of supplements often lack scientific data demonstrating the effects on healthy and diseased individuals. Hence, it was investigated, whether a frequently used supplement in humans, Candida rugosa lipase (CRL), gets delivered active beyond the stomach in the intestinal tract of C57BL/6 J mice and its impact on the gut microbial community and environment. We showed for the first time the movement of CRL in an active state through the mouse digestive tract by determination of intestinal CRL activity and free fatty acids concentrations. The short- and long-term administration of CRL resulted in significant alterations of the gut microbiome, favoring the growth of, for instance, Verrucomicrobia but also other species associated with normal body mass index (BMI) or butyrate expression, both considered beneficial. In addition, we showed that these changes persisted after supplementation and that gut barrier integrity was unaffected by the treatment. In conclusion, CRL can be delivered in an active state beyond the stomach and supplementation altered the murine gut microbiome favoring beneficial bacterial species, which may be of relevance in humans in healthy but also potentially in disease states.

1289. Douching and Rectal Inflammation in Sexual Minority Men: Implications for HIV Acquisition

Background

Rectal douching is the practice of rinsing the anus and rectum prior to, or after, anal sex. Among gay, bisexual, and other men who have sex with men (sexual minority men), rectal douching is likely to enhance HIV acquisition by amplifying inflammation of the rectal mucosa. This study evaluated the association of rectal douching with rectal inflammation among sexual minority men at risk for HIV infection.

Methods

HIV uninfected sexual minority men who reported receptive anal intercourse in the past 3 months (N = 197) were recruited from four STI clinics in South Florida, the leading region for new HIV infections among sexual minority men in the United States. A brief survey assessed rectal douching practices and sexual behaviors in the previous 3 months. Rectal inflammation was assessed by measuring 13 human rectal inflammatory cytokines/chemokines in rectal swabs using the LEGENDplex Human Inflammation Panel in a sample of 38 participants who reported douching and condomless receptive anal intercourse (CRAI).

Results

Average age was 35.8 years (SD=15.4). The sample was multi-ethnic: 42% Caucasian, 38% Hispanic/Latino, 13% Black/African American, and 7% other ethnic minority. Approximately two-thirds of participants (65%) reported any rectal douching in the past 3 months and the median number times participants douched was five. Participants who douched had more CRAI partners (Cohen’s d = 0.4587; P < 0.01), and more CRAI partners to ejaculation (Cohen’s d = 0.4813; P < 0.01) compared with participants who did not douche. Participants who reported douching five or more times in the past 3 months displayed significantly higher levels of IL-8 (Cohen’s d = 0.79; P = 0.02) than those who douched less than five times.

Conclusion

Among sexual minority men who engage in CRAI, more frequent douching is associated with higher levels of rectal inflammation. Assessment of rectal douching should be included when evaluating HIV prevention interventions among sexual minority men, as those who douche are more likely to engage in CRAI and are at higher risk for acquisition of HIV and other sexually transmitted infection. Further mechanistic studies are needed to assess the role of rectal douching in promoting rectal inflammation.

Disclosures

All authors: No reported disclosures.

P3778Long-term outcome of non-pharmacologial treatment of atrial fibrillation in hypertrophic cardiomyopathy: a large single-centre experience

Introduction

Atrial fibrillation (AF) is common in hypertrophic cardiomyopathy (HCM) and is generally associated with a significant deterioration of clinical status. Non-pharmacological treatment such as surgical and catheter ablation has become an established therapy for symptomatic AF but in patients with HCM often having a chronically increased left atrial pressure and extensive atrial cardiomyopathy the long-term outcome is uncertain.

Purpose

The present study aimed to analyse the long-term outcome of AF ablation in HCM and the mechanism of recurrent atrial arrhythmias using high-density mapping systems.

Methods

A total of 65 patients (age 64.5±9.9 years, 42 (64.6%) male) with HCM undergoing AF ablation for symptomatic AF were included in our study. The ablation strategy for catheter ablation included pulmonary vein isolation in all patients and biatrial ablation of complex fractionated electrograms with additional ablation lines if appropriate. In patients with suspected atrial tachycardia (AT) high-density activation and substrate mapping were performed. A surgical ablation at the time of an operative myectomy for left ventricular outflow tract obstruction was performed in 8 (12.3%) patients. The outcome was analysed using clinical assessment, Holter ECG and continuous rhythm monitoring of cardiac implantable electric devices.

Results

Paroxysmal AF was present in 27 (41.6%), persistent AF in 37 (56.9%) and primary AT in 1 (1.5%) patients. The mean left atrial diameter was 54.1±12.5 ml. In 11 (16.9%) patients with AT high-density mapping was used to characterize the mechanism of the ongoing tachycardia. After 1.9±1.2 ablation procedures and a follow-up of 48.5±37.2 months, ablation success was demonstrated in 58.9% of patients. The success rate for paroxysmal and persistent AF was 70.0% and 55.8%, respectively (p=0.023). Of those patients with AT high-density mapping guided ablation was successful in 44.4% of patients. The LA diameter of patients with a successful ablation was smaller (52.2 vs. 58.1 mm; p=0.003).

Conclusion

Non-pharmacological treatment of AF in HCM is effective during long-term follow-up. Paroxysmal AF and a smaller LA diameter are favourable for successful ablation. In patients with complex AT the use of high-density mapping can guide ablation resulting in further ablation success in a reasonable number of patients.

The Evolving Facets of Bacterial Vaginosis: Implications for HIV Transmission

Bacterial vaginosis (BV) is a common yet poorly understood vaginal condition that has become a major focus of HIV transmission and immunology research. Varied terminologies are used by clinicians and researchers to describe microbial communities that reside in the female reproductive tract (FRT), which is driven, in part, by microbial genetic and metabolic complexity, evolving diagnostic and molecular techniques, and multidisciplinary perspectives of clinicians, epidemiologists, microbiologists, and immunologists who all appreciate the scientific importance of understanding mechanisms that underlie BV. This Perspectives article aims to clarify the varied terms used to describe the cervicovaginal microbiota and its “nonoptimal” state, under the overarching term of BV. The ultimate goal is to move toward language standardization in future literature that facilitates a better understanding of the impact of BV on FRT immunology and risk of sexually transmitted infections, including HIV.

A Summary of the Third Annual HIV Microbiome Workshop

Our microbial cotravelers have increasingly apparent roles in both maintaining health and causing disease in several organ systems. Investigators gather annually at the National Institutes of Health to present new discoveries regarding the role of the microbiome in human health and a special focus on persons living with HIV. Here, we summarize the discussions from the third annual Virology Education workshop on the microbiome in HIV, which took place in October of 2017.

Dynamic vaginal microbiota in pigtail macaques is associated with menstrual cycle and inflammation (MUC9P.753)

A challenge in prevention of mucosal HIV transmission is incomplete understanding of correlates of vaginal transmission, including mucosal inflammation. Vaginal SIV/SHIV transmission in pigtail macaques (Macaca nemestrina) is an excellent model for HIV transmission, however little is known about how genital microbes may influence inflammation and transmission. Broad-range 16S rRNA gene PCR and pyrosequencing was performed on vaginal swabs to assess vaginal microbiome in healthy pigtail macaques. Bacteria were identified to the species or genus level. Luminex was used to measure cytokine and chemokine levels in vaginal swabs. Pigtail macaques had diverse bacterial communities at all phases of the menstrual cycle, with a range of dominant bacteria. Several species were identified that are commonly found in bacterial vaginosis (BV) in humans, and three animals exhibitied Lactobacillus-dominance. Longitudinal sampling demonstrated that the vaginal microbiome is dynamic and possibly influenced by the menstrual cycle. Animals with Lactobacillus-dominant vaginal microbiota had decreased IL-8 (p=0.009) and IL-1Ra (p=0.044). In conclusion, the macaque vaginal microbiota is diverse, dynamic, and can resemble the human vaginal microbiota, including BV-associated bacteria as well as Lactobacillus spp, which is associated with decreased innate inflammation. These data provide a foundation for understanding how the vaginal microbiome may impact risk of HIV/SIV transmission.

Rate of AIDS progression is associated with gastrointestinal dysfunction in SIV-infected pigtail macaques (P3045)

During HIV/SIV infection, mucosal immune system dysfunction and systemic immune activation are associated with progression to AIDS, however it is unclear to what extent pre-existing gastrointestinal damage relates to disease progression after infection. Pigtail macaques (PTM) are an excellent model in which to assess mucosal dysfunction in relation to HIV/SIV pathogenesis, as the majority of these animals have high levels of gastrointestinal damage, immune activation, and microbial translocation prior to infection, and rapidly progress to AIDS upon SIV infection. Here we characterized the mucosal immune environment prior to and throughout SIV infection in 13 uninfected PTM and 9 SIV-infected PTM, of which 3 were slow progressors. This small subset of slow progressors had limited innate immune activation in mucosal tissues in the periphery, which was associated with a more intact colonic epithelial barrier. Furthermore, we found that pre-infection levels of microbial translocation, as measured by lipopolysaccharide binding protein (LBP), in PTM correlated with the rate of progression to AIDS. These data suggest that pre-existing levels of microbial translocation and gastrointestinal tract dysfunction may influence the rate of HIV disease progression.

Correlates of preserved CD4(+) T cell homeostasis during natural, nonpathogenic simian immunodeficiency virus infection of sooty mangabeys: implications for AIDS pathogenesis

In contrast to HIV-infected humans, naturally SIV-infected sooty mangabeys (SMs) very rarely progress to AIDS. Although the mechanisms underlying this disease resistance are unknown, a consistent feature of natural SIV infection is the absence of the generalized immune activation associated with HIV infection. To define the correlates of preserved CD4(+) T cell counts in SMs, we conducted a cross-sectional immunological study of 110 naturally SIV-infected SMs. The nonpathogenic nature of the infection was confirmed by an average CD4(+) T cell count of 1,076 +/- 589/mm(3) despite chronic infection with a highly replicating virus. No correlation was found between CD4(+) T cell counts and either age (used as a surrogate marker for length of infection) or viremia. The strongest correlates of preserved CD4(+) T cell counts were a low percentage of circulating effector T cells (CD28(-)CD95(+) and/or IL-7R/CD127(-)) and a high percentage of CD4(+)CD25(+) T cells. These findings support the hypothesis that the level of immune activation is a key determinant of CD4(+) T cell counts in SIV-infected SMs. Interestingly, we identified 14 animals with CD4(+) T cell counts of <500/mm(3), of which two show severe and persistent CD4(+) T cell depletion (<50/mm(3)). Thus, significant CD4(+) T cell depletion does occasionally follow SIV infection of SMs even in the context of generally low levels of immune activation, lending support to the hypothesis of multifactorial control of CD4(+) T cell homeostasis in this model of infection. The absence of AIDS in these "CD4(low)" naturally SIV-infected SMs defines a protective role of the reduced immune activation even in the context of a significant CD4(+) T cell depletion.

A human schwannoma cell line supports the in vitro adhesion of Plasmodium falciparum infected erythrocytes to chondroitin-4-sulfate

The paucity of human cell lines expressing defined receptors for the cytoadhesion of erythrocytes infected with the human malarial parasite Plasmodium falciparumhas hampered the investigation of this important virulence property. Here, we investigate a permanent cell line derived from a human, malignant schwannoma, termed HMS-97, and show that this cell line expresses chondroitin-4-sulfate as the only surface receptor to which P. falciparum-infected erythrocytes can cytoadhere. Other common receptors for parasite adhesion, including CD36, vascular cellular adhesion molecule-1 (VCAM), intercellular adhesion molecule-1 (ICAM-1), and E-selectin are absent. Thus, HMS-97 cells are a useful tool for the study of P. falciparum adhesion to chondoitin-4-sulfate, the main receptor for parasite sequestration in the placenta. As chondoitin-4-sulfate can be readily cleaved from the cells, HMS-97 cells are also an ideal system for expressing recombinant adhesion receptors and studying their function in binding assays.