The effect of gastrointestinal graft-versus-host disease and diarrhea on the pharmacokinetic profile of sotrovimab in hematopoietic stem cell transplant recipients.

BACKGROUND: Monoclonal antibodies (mAbs) are utilized broadly to treat cancer and infectious diseases, and mAb exposure (serum concentration over time) is one predictor of overall treatment efficacy. Herein, we present findings from a clinical trial evaluating the pharmacokinetics (PK) of the long-acting mAb sotrovimab targeting SARS-CoV-2 in hematopoietic cell transplant (HCT) recipients. METHODS: All participants received an intravenous infusion of sotrovimab within one week prior to initiating the pre-transplant preparative regimen. The serum concentration of sotrovimab was measured longitudinally for up to 24 weeks post-transplant. RESULTS: Compared to non-HCT participants, we found that mAb clearance was 10% and 26% higher in autologous and allogeneic HCT recipients, respectively. Overall sotrovimab exposure was approximately 15% lower in HCT recipients compared to non-HCT recipients. Exposure was significantly reduced in HCT recipients who developed diarrhea and lower gastrointestinal (GI) graft-versus-host disease (GVHD) post-transplant. CONCLUSIONS: These data show that sotrovimab exposure may be reduced in HCT recipients, possibly related to increased GI clearance in patients with GVHD. This phenomenon has implications for dose selection and duration of efficacy with sotrovimab and potentially other mAbs in this vulnerable patient population. Thus, mAb dose regimens developed in non-HCT populations may have to be optimized when applied to HCT populations.

Unveiling the proteome-wide autoreactome enables enhanced evaluation of emerging CAR T cell therapies in autoimmunity.

Given the global surge in autoimmune diseases, it is critical to evaluate emerging therapeutic interventions. Despite numerous new targeted immunomodulatory therapies, comprehensive approaches to apply and evaluate the effects of these treatments longitudinally are lacking. Here, we leveraged advances in programmable-phage immunoprecipitation methodology to explore the modulation, or lack thereof, of autoantibody profiles, proteome-wide, in both health and disease. Using a custom set of over 730,000 human-derived peptides, we demonstrated that each individual, regardless of disease state, possesses a distinct and complex constellation of autoreactive antibodies. For each individual, the set of resulting autoreactivites constituted a unique immunological fingerprint, or "autoreactome," that was remarkably stable over years. Using the autoreactome as a primary output, we evaluated the relative effectiveness of various immunomodulatory therapies in altering autoantibody repertoires. We found that therapies targeting B cell maturation antigen (BCMA) profoundly altered an individual's autoreactome, while anti-CD19 and anti-CD20 therapies had minimal effects. These data both confirm that the autoreactome comprises autoantibodies secreted by plasma cells and strongly suggest that BCMA or other plasma cell-targeting therapies may be highly effective in treating currently refractory autoantibody-mediated diseases.

Validation of Ligand Tetramers for the Detection of Antigen-Specific Lymphocytes.

The study of Ag-specific lymphocytes has been a key advancement in immunology over the past few decades. The development of multimerized probes containing Ags, peptide:MHC complexes, or other ligands was one innovation allowing the direct study of Ag-specific lymphocytes by flow cytometry. Although these types of study are now common and performed by thousands of laboratories, quality control and assessment of probe quality are often minimal. In fact, many of these types of probe are made in-house, and protocols vary between laboratories. Although peptide:MHC multimers can often be obtained from commercial sources or core facilities, few such services exist for Ag multimers. To ensure high quality and consistency with ligand probes, we have developed an easy and robust multiplexed approach using commercially available beads able to bind Abs specific for the ligand of interest. Using this assay, we have sensitively assessed the performance of peptide:MHC and Ag tetramers and have found considerable batch-to-batch variability in performance and stability over time more easily than using murine or human cell-based assays. This bead-based assay can also reveal common production errors such as miscalculation of Ag concentration. This work could set the stage for the development of standardized assays for all commonly used ligand probes to limit laboratory-to-laboratory technical variation and experimental failure caused by probe underperformance.

Cross-protective antibodies against common endemic respiratory viruses.

Respiratory syncytial virus (RSV), human metapneumovirus (HMPV), and human parainfluenza virus types one (HPIV1) and three (HPIV3) can cause severe disease and death in immunocompromised patients, the elderly, and those with underlying lung disease. A protective monoclonal antibody exists for RSV, but clinical use is limited to high-risk infant populations. Hence, therapeutic options for these viruses in vulnerable patient populations are currently limited. Here, we present the discovery, in vitro characterization, and in vivo efficacy testing of two cross-neutralizing monoclonal antibodies, one targeting both HPIV3 and HPIV1 and the other targeting both RSV and HMPV. The 3 × 1 antibody is capable of targeting multiple parainfluenza viruses; the MxR antibody shares features with other previously reported monoclonal antibodies that are capable of neutralizing both RSV and HMPV. We obtained structures using cryo-electron microscopy of these antibodies in complex with their antigens at 3.62 Å resolution for 3 × 1 bound to HPIV3 and at 2.24 Å for MxR bound to RSV, providing a structural basis for in vitro binding and neutralization. Together, a cocktail of 3 × 1 and MxR could have clinical utility in providing broad protection against four of the respiratory viruses that cause significant morbidity and mortality in at-risk individuals.

Anti-HLA antibodies in recipients of CD19 versus BCMA-targeted CAR T-cell therapy.

Antibodies against foreign human leukocyte antigen (HLA) molecules are barriers to successful organ transplantation. B cell-depleting treatments are used to reduce anti-HLA antibodies but have limited efficacy. We hypothesized that the primary source for anti-HLA antibodies is long-lived plasma cells, which are ineffectively targeted by B cell depletion. To study this, we screened for anti-HLA antibodies in a prospectively enrolled cohort of 49 patients who received chimeric antigen receptor T-cell therapy (CARTx), targeting naïve and memory B cells (CD19-targeted, n = 21) or plasma cells (BCMA-targeted, n = 28) for hematologic malignancies. Longitudinal samples were collected before and up to 1 year after CARTx. All individuals were in sustained remission. We identified 4 participants with anti-HLA antibodies before CD19-CARTx. Despite B cell depletion, anti-HLA antibodies and calculated panel reactive antibody scores were stable for 1 year after CD19-CARTx. Only 1 BCMA-CARTx recipient had pre-CARTx low-level anti-HLA antibodies, with no follow-up samples available. These data implicate CD19neg long-lived plasma cells as an important source for anti-HLA antibodies, a model supported by infrequent HLA sensitization in BCMA-CARTx subjects receiving previous plasma cell-targeted therapies. Thus, plasma cell-targeted therapies may be more effective against HLA antibodies, thereby enabling improved access to organ transplantation and rejection management.

T cell receptor sequencing identifies prior SARS-CoV-2 infection and correlates with neutralizing antibodies and disease severity.

BACKGROUNDMeasuring the immune response to SARS-CoV-2 enables assessment of past infection and protective immunity. SARS-CoV-2 infection induces humoral and T cell responses, but these responses vary with disease severity and individual characteristics.METHODSA T cell receptor (TCR) immunosequencing assay was conducted using small-volume blood samples from 302 individuals recovered from COVID-19. Correlations between the magnitude of the T cell response and neutralizing antibody (nAb) titers or indicators of disease severity were evaluated. Sensitivity of T cell testing was assessed and compared with serologic testing.RESULTSSARS-CoV-2-specific T cell responses were significantly correlated with nAb titers and clinical indicators of disease severity, including hospitalization, fever, and difficulty breathing. Despite modest declines in depth and breadth of T cell responses during convalescence, high sensitivity was observed until at least 6 months after infection, with overall sensitivity ~5% greater than serology tests for identifying prior SARS-CoV-2 infection. Improved performance of T cell testing was most apparent in recovered, nonhospitalized individuals sampled > 150 days after initial illness, suggesting greater sensitivity than serology at later time points and in individuals with less severe disease. T cell testing identified SARS-CoV-2 infection in 68% (55 of 81) of samples with undetectable nAb titers (<1:40) and in 37% (13 of 35) of samples classified as negative by 3 antibody assays.CONCLUSIONThese results support TCR-based testing as a scalable, reliable measure of past SARS-CoV-2 infection with clinical value beyond serology.TRIAL REGISTRATIONSpecimens were accrued under trial NCT04338360 accessible at clinicaltrials.gov.FUNDINGThis work was funded by Adaptive Biotechnologies, Frederick National Laboratory for Cancer Research, NIAID, Fred Hutchinson Joel Meyers Endowment, Fast Grants, and American Society for Transplantation and Cell Therapy.

Humoral immunogenicity of the seasonal influenza vaccine before and after CAR-T-cell therapy: a prospective observational study.

Recipients of chimeric antigen receptor-modified T (CAR-T) cell therapies for B cell malignancies have profound and prolonged immunodeficiencies and are at risk for serious infections, including respiratory virus infections. Vaccination may be important for infection prevention, but there are limited data on vaccine immunogenicity in this population. We conducted a prospective observational study of the humoral immunogenicity of commercially available 2019-2020 inactivated influenza vaccines in adults immediately prior to or while in durable remission after CD19-, CD20-, or B cell maturation antigen-targeted CAR-T-cell therapy, as well as controls. We tested for antibodies to all four vaccine strains using neutralization and hemagglutination inhibition (HAI) assays. Antibody responses were defined as at least fourfold titer increases from baseline. Seroprotection was defined as a HAI titer ≥40. Enrolled CAR-T-cell recipients were vaccinated 14-29 days prior to (n=5) or 13-57 months following therapy (n=13), and the majority had hypogammaglobulinemia and cellular immunodeficiencies prevaccination. Eight non-immunocompromised adults served as controls. Antibody responses to ≥1 vaccine strain occurred in 2 (40%) individuals before CAR-T-cell therapy and in 4 (31%) individuals vaccinated after CAR-T-cell therapy. An additional 1 (20%) and 6 (46%) individuals had at least twofold increases, respectively. One individual vaccinated prior to CAR-T-cell therapy maintained a response for >3 months following therapy. Across all tested vaccine strains, seroprotection was less frequent in CAR-T-cell recipients than in controls. There was evidence of immunogenicity even among individuals with low immunoglobulin, CD19+ B cell, and CD4+ T-cell counts. These data support consideration for vaccination before and after CAR-T-cell therapy for influenza and other relevant pathogens such as SARS-CoV-2, irrespective of hypogammaglobulinemia or B cell aplasia. However, relatively impaired humoral vaccine immunogenicity indicates the need for additional infection-prevention strategies. Larger studies are needed to refine our understanding of potential correlates of vaccine immunogenicity, and durability of immune responses, in CAR-T-cell therapy recipients.

Methods to Measure Antibody Neutralization of Live Human Coronavirus OC43.

The human Betacoronavirus OC43 is a common cause of respiratory viral infections in adults and children. Lung infections with OC43 are associated with mortality, especially in hematopoietic stem cell transplant recipients. Neutralizing antibodies play a major role in protection against many respiratory viral infections, but to date a live viral neutralization assay for OC43 has not been described. We isolated a human monoclonal antibody (OC2) that binds to the spike protein of OC43 and neutralizes the live virus derived from the original isolate of OC43. We used this monoclonal antibody to develop and test the performance of two readily accessible in vitro assays for measuring antibody neutralization, one utilizing cytopathic effect and another utilizing an ELISA of infected cells. We used both methods to measure the neutralizing activity of the OC2 monoclonal antibody and of human plasma. These assays could prove useful for studying humoral responses to OC43 and cross-neutralization with other medically important betacoronaviruses.

Fatal infection with enterocolitis from methicillin-resistant Staphylococcus aureus and the continued value of culture in the era of molecular diagnostics.

MRSA enterocolitis is under-recognized in the setting of PCR testing. In this case report, we describe risk factors, the importance of stool culture, and the third published case of MRSA enterocolitis in a patient with leukemia. In addition, we performed a retrospective analysis of all stool cultures at our institution that have grown Staphylococcus aureus, and we describe an additional five cases. We also report the diagnostic yield of organisms detected by culture, but not on the FilmArray panel. While rare, these cases demonstrate that MRSA in stool may indicate a severe and potentially life-threatening infection, particularly in immunocompromised persons.

Humoral immunogenicity of the seasonal influenza vaccine before and after CAR-T-cell therapy.

Recipients of chimeric antigen receptor-modified T (CAR-T) cell therapies for B-cell malignancies are immunocompromised and at risk for serious infections. Vaccine immunogenicity is unknown in this population. We conducted a prospective observational study of the humoral immunogenicity of 2019-2020 inactivated influenza vaccines (IIV) in children and adults immediately prior to (n=7) or 13-57 months after (n=15) CD19-, CD20-, or BCMA-targeted CAR-T-cell therapy, as well as controls (n=8). Individuals post-CAR-T-cell therapy were in remission. We tested for antibodies to 4 vaccine strains at baseline and ≥1 time point after IIV using neutralization and hemagglutination inhibition assays. An antibody response was defined as a ≥4-fold titer increase from baseline at the first post-vaccine time point. Baseline A(H1N1) titers in the CAR-T cohorts were significantly lower compared to controls. Antibody responses to ≥1 vaccine strain occurred in 2 (29%) individuals before CAR-T-cell therapy; one individual maintained a response for >3 months post-CAR-T-cell therapy. Antibody responses to ≥1 vaccine strain occurred in 6 (40%) individuals vaccinated after CAR-T-cell therapy. An additional 2 (29%) and 6 (40%) individuals had ≥2-fold increases (at any time) in the pre- and post-CAR-T cohorts, respectively. There were no identified clinical or immunologic predictors of antibody responses. Neither severe hypogammaglobulinemia nor B-cell aplasia precluded antibody responses. These data support consideration for vaccination before and after CAR-T-cell therapy for influenza and other relevant pathogens such as SARS-CoV-2, irrespective of hypogammaglobulinemia or B-cell aplasia. Larger studies are needed to determine correlates of vaccine immunogenicity and durability in CAR-T-cell therapy recipients. KEY POINTS: Influenza vaccination was immunogenic pre- and post-CAR-T-cell therapy, despite hypogammaglobulinemia and B-cell aplasia.Vaccination with inactivated vaccines can be considered before CAR-T-cell therapy and in individuals with remission after therapy.

Antibodies against vaccine-preventable infections after CAR-T cell therapy for B cell malignancies.

BACKGROUNDLittle is known about pathogen-specific humoral immunity after chimeric antigen receptor-modified T (CAR-T) cell therapy for B cell malignancies.METHODSWe conducted a prospective cross-sectional study of CD19-targeted or B cell maturation antigen-targeted (BCMA-targeted) CAR-T cell therapy recipients at least 6 months posttreatment and in remission. We measured pathogen-specific IgG against 12 vaccine-preventable infections and the number of viral and bacterial epitopes to which IgG was detected ("epitope hits") using a serological profiling assay. The primary outcome was the proportion of participants with IgG levels above a threshold correlated with seroprotection for vaccine-preventable infections.RESULTSWe enrolled 65 children and adults a median of 20 months after CD19- (n = 54) or BCMA- (n = 11) CAR-T cell therapy. Among 30 adults without IgG replacement therapy (IGRT) in the prior 16 weeks, 27 (90%) had hypogammaglobulinemia. These individuals had seroprotection to a median of 67% (IQR, 59%-73%) of tested infections. Proportions of participants with seroprotection per pathogen were comparable to population-based studies, but most individuals lacked seroprotection to specific pathogens. Compared with CD19-CAR-T cell recipients, BCMA-CAR-T cell recipients were half as likely to have seroprotection (prevalence ratio, 0.47; 95% CI, 0.18-1.25) and had fewer pathogen-specific epitope hits (mean difference, -90 epitope hits; 95% CI, -157 to -22).CONCLUSIONSeroprotection for vaccine-preventable infections in adult CD19-CAR-T cell recipients was comparable to the general population. BCMA-CAR-T cell recipients had fewer pathogen-specific antibodies. Deficits in both groups support the need for vaccine and immunoglobulin replacement therapy studies.FUNDINGSwiss National Science Foundation (Early Postdoc Mobility grant P2BSP3_188162), NIH/National Cancer Institute (NIH/NCI) (U01CA247548 and P01CA018029), NIH/NCI Cancer Center Support Grants (P30CA0087-48 and P30CA015704-44), American Society for Transplantation and Cellular Therapy, and Juno Therapeutics/BMS.

Protective antibodies against human parainfluenza virus type 3 infection.

Human parainfluenza virus type III (HPIV3) is a common respiratory pathogen that afflicts children and can be fatal in vulnerable populations, including the immunocompromised. There are currently no effective vaccines or therapeutics available, resulting in tens of thousands of hospitalizations per year. In an effort to discover a protective antibody against HPIV3, we screened the B cell repertoires from peripheral blood, tonsils, and spleen from healthy children and adults. These analyses yielded five monoclonal antibodies that potently neutralized HPIV3 in vitro. These HPIV3-neutralizing antibodies targeted two non-overlapping epitopes of the HPIV3 F protein, with most targeting the apex. Prophylactic administration of one of these antibodies, PI3-E12, resulted in potent protection against HPIV3 infection in cotton rats. Additionally, PI3-E12 could also be used therapeutically to suppress HPIV3 in immunocompromised animals. These results demonstrate the potential clinical utility of PI3-E12 for the prevention or treatment of HPIV3 in both immunocompetent and immunocompromised individuals.

Clinical, laboratory, and temporal predictors of neutralizing antibodies against SARS-CoV-2 among COVID-19 convalescent plasma donor candidates.

BACKGROUNDSARS-CoV-2-specific antibodies may protect from reinfection and disease, providing rationale for administration of plasma containing SARS-CoV-2-neutralizing antibodies (nAbs) as a treatment for COVID-19. Clinical factors and laboratory assays to streamline plasma donor selection, and the durability of nAb responses, are incompletely understood.METHODSPotential convalescent plasma donors with virologically documented SARS-CoV-2 infection were tested for serum IgG against SARS-CoV-2 spike protein S1 domain and against nucleoprotein (NP), and for nAb.RESULTSAmong 250 consecutive persons, including 27 (11%) requiring hospitalization, who were studied a median of 67 days since symptom onset, 97% were seropositive on 1 or more assays. Sixty percent of donors had nAb titers ≥1:80. Correlates of higher nAb titers included older age (adjusted OR [AOR] 1.03 per year of age, 95% CI 1.00-1.06), male sex (AOR 2.08, 95% CI 1.13-3.82), fever during illness (AOR 2.73, 95% CI 1.25-5.97), and disease severity represented by hospitalization (AOR 6.59, 95% CI 1.32-32.96). Receiver operating characteristic analyses of anti-S1 and anti-NP antibody results yielded cutoffs that corresponded well with nAb titers, with the anti-S1 assay being slightly more predictive. nAb titers declined in 37 of 41 paired specimens collected a median of 98 days (range 77-120) apart (P < 0.001). Seven individuals (2.8%) were persistently seronegative and lacked T cell responses.CONCLUSIONnAb titers correlated with COVID-19 severity, age, and sex. SARS-CoV-2 IgG results can serve as useful surrogates for nAb testing. Functional nAb levels declined, and a small proportion of convalescent individuals lacked adaptive immune responses.FUNDINGThe project was supported by the Frederick National Laboratory for Cancer Research with support from the NIAID under contract number 75N91019D00024, and was supported by the Fred Hutchinson Joel Meyers Endowment, Fast-Grants, a New Investigator award from the American Society for Transplantation and Cellular Therapy, and NIH contracts 75N93019C0063, 75N91019D00024, and HHSN272201800013C, and NIH grants T32-AI118690, T32-AI007044, K08-AI119142, and K23-AI140918.

Predictive Value of Respiratory Viral Detection in the Upper Respiratory Tract for Infection of the Lower Respiratory Tract With Hematopoietic Stem Cell Transplantation.

BACKGROUND: Hematopoietic cell transplant (HCT) recipients are frequently infected with respiratory viruses (RVs) in the upper respiratory tract (URT), but the concordance between URT and lower respiratory tract (LRT) RV detection is not well characterized. METHODS: Hematopoietic cell transplant candidates and recipients with respiratory symptoms and LRT and URT RV testing via multiplex PCR from 2009 to 2016 were included. Logistic regression models were used to analyze risk factors for LRT RV detection. RESULTS: Two-hundred thirty-five HCT candidates or recipients had URT and LRT RV testing within 3 days. Among 115 subjects (49%) positive for a RV, 37% (42 of 115) had discordant sample pairs. Forty percent (17 of 42) of discordant pairs were positive in the LRT but negative in the URT. Discordance was common for adenovirus (100%), metapneumovirus (44%), rhinovirus (34%), and parainfluenza virus type 3 (28%); respiratory syncytial virus was highly concordant (92%). Likelihood of LRT detection was increased with URT detection (oods ratio [OR] = 73.7; 95% confidence interval [CI], 26.7-204) and in cytomegalovirus-positive recipients (OR = 3.70; 95% CI, 1.30-10.0). CONCLUSIONS: High rates of discordance were observed for certain RVs. Bronchoalveolar lavage sampling may provide useful diagnostic information to guide management in symptomatic HCT candidates and recipients.

Cross-Reactivity with Self-Antigen Tunes the Functional Potential of Naive B Cells Specific for Foreign Antigens.

Upon Ag exposure, naive B cells expressing BCR able to bind Ag can undergo robust proliferation and differentiation that can result in the production of Ab-secreting and memory B cells. The factors determining whether an individual naive B cell will proliferate following Ag encounter remains unclear. In this study, we found that polyclonal naive murine B cell populations specific for a variety of foreign Ags express high levels of the orphan nuclear receptor Nur77, which is known to be upregulated downstream of BCR signaling as a result of cross-reactivity with self-antigens in vivo. Similarly, a fraction of naive human B cells specific for clinically-relevant Ags derived from respiratory syncytial virus and HIV-1 also exhibited an IgMLOW IgD+ phenotype, which is associated with self-antigen cross-reactivity. Functionally, naive B cells expressing moderate levels of Nur77 are most likely to proliferate in vivo following Ag injection. Together, our data indicate that BCR cross-reactivity with self-antigen is a common feature of populations of naive B cells specific for foreign Ags and a moderate level of cross-reactivity primes individual cells for optimal proliferative responses following Ag exposure.

Techniques to Study Antigen-Specific B Cell Responses.

Antibodies against foreign antigens are a critical component of the overall immune response and can facilitate pathogen clearance during a primary infection and also protect against subsequent infections. Dysregulation of the antibody response can lead to an autoimmune disease, malignancy, or enhanced infection. Since the experimental delineation of a distinct B cell lineage in 1965, various methods have been developed to understand antigen-specific B cell responses in the context of autoimmune diseases, primary immunodeficiencies, infection, and vaccination. In this review, we summarize the established techniques and discuss new and emerging technologies for probing the B cell response in vitro and in vivo by taking advantage of the specificity of B cell receptor (BCR)-associated and secreted antibodies. These include ELISPOT, flow cytometry, mass cytometry, and fluorescence microscopy to identify and/or isolate primary antigen-specific B cells. We also present our approach to identify rare antigen-specific B cells using magnetic enrichment followed by flow cytometry. Once these cells are isolated, in vitro proliferation assays and adoptive transfer experiments in mice can be used to further characterize antigen-specific B cell activation, function, and fate. Transgenic mouse models of B cells targeting model antigens and of B cell signaling have also significantly advanced our understanding of antigen-specific B cell responses in vivo.

Pathogen receptor discovery with a microfluidic human membrane protein array.

The discovery of how a pathogen invades a cell requires one to determine which host cell receptors are exploited. This determination is a challenging problem because the receptor is invariably a membrane protein, which represents an Achilles heel in proteomics. We have developed a universal platform for high-throughput expression and interaction studies of membrane proteins by creating a microfluidic-based comprehensive human membrane protein array (MPA). The MPA is, to our knowledge, the first of its kind and offers a powerful alternative to conventional proteomics by enabling the simultaneous study of 2,100 membrane proteins. We characterized direct interactions of a whole nonenveloped virus (simian virus 40), as well as those of the hepatitis delta enveloped virus large form antigen, with candidate host receptors expressed on the MPA. Selected newly discovered membrane protein-pathogen interactions were validated by conventional methods, demonstrating that the MPA is an important tool for cellular receptor discovery and for understanding pathogen tropism.

The Rel/NF-κB pathway and transcription of immediate early genes in T cell activation are inhibited by microgravity.

This study tested the hypothesis that transcription of immediate early genes is inhibited in T cells activated in µg. Immunosuppression during spaceflight is a major barrier to safe, long-term human space habitation and travel. The goals of these experiments were to prove that µg was the cause of impaired T cell activation during spaceflight, as well as understand the mechanisms controlling early T cell activation. T cells from four human donors were stimulated with Con A and anti-CD28 on board the ISS. An on-board centrifuge was used to generate a 1g simultaneous control to isolate the effects of µg from other variables of spaceflight. Microarray expression analysis after 1.5 h of activation demonstrated that µg- and 1g-activated T cells had distinct patterns of global gene expression and identified 47 genes that were significantly, differentially down-regulated in µg. Importantly, several key immediate early genes were inhibited in µg. In particular, transactivation of Rel/NF-κB, CREB, and SRF gene targets were down-regulated. Expression of cREL gene targets were significantly inhibited, and transcription of cREL itself was reduced significantly in µg and upon anti-CD3/anti-CD28 stimulation in simulated µg. Analysis of gene connectivity indicated that the TNF pathway is a major early downstream effector pathway inhibited in µg and may lead to ineffective proinflammatory host defenses against infectious pathogens during spaceflight. Results from these experiments indicate that µg was the causative factor for impaired T cell activation during spaceflight by inhibiting transactivation of key immediate early genes.

The C proteins of human parainfluenza virus type 1 limit double-stranded RNA accumulation that would otherwise trigger activation of MDA5 and protein kinase R.

Human parainfluenza virus type 1 (HPIV1) is an important respiratory pathogen in young children, the immunocompromised, and the elderly. We found that infection with wild-type (WT) HPIV1 suppressed the innate immune response in human airway epithelial cells by preventing not only phosphorylation of interferon regulatory factor 3 (IRF3) but also degradation of IκBß, thereby inhibiting IRF3 and NF-κB activation, respectively. Both of these effects were ablated by a F170S substitution in the HPIV1 C proteins (F170S) or by silencing the C open reading frame [P(C-)], resulting in a potent beta interferon (IFN-ß) response. Using murine knockout cells, we found that IFN-ß induction following infection with either mutant relied mainly on melanoma-associated differentiation gene 5 (MDA5) rather than retinoic acid-inducible gene I (RIG-I). Infection with either mutant, but not WT HPIV1, induced a significant accumulation of intracellular double-stranded RNA (dsRNA). These mutant viruses directed a marked increase in the accumulation of viral genome, antigenome, and mRNA that was coincident with the accumulation of dsRNA. In addition, the amount of viral proteins was reduced compared to that of WT HPIV1. Thus, the accumulation of dsRNA might be a result of an imbalance in the N protein/genomic RNA ratio leading to incomplete encapsidation. Protein kinase R (PKR) activation and IFN-ß induction followed the kinetics of dsRNA accumulation. Interestingly, the C proteins did not appear to directly inhibit intracellular signaling involved in IFN-ß induction; instead, their role in preventing IFN-ß induction appeared to be in suppressing the formation of dsRNA. PKR activation contributed to IFN-ß induction and also was associated with the reduction in the amount of viral proteins. Thus, the HPIV1 C proteins normally limit the accumulation of dsRNA and thereby limit activation of IRF3, NF-κB, and PKR. If C protein function is compromised, as in the case of F170S HPIV1, the resulting PKR activation and reduction in viral protein levels enable the host to further reduce C protein levels and to mount a potent antiviral type I IFN response.

Selection of tumorigenic melanoma cells using ALDH.

Despite increasing knowledge regarding melanoma-initiating cells (MICs), questions persist regarding the number and phenotypic nature of cells with tumor-generating capability. Evidence for a phenotypically distinct human MIC has been found in NOD/SCID (non-obese diabetic/severe combined immunodeficiency) mice. However, a phenotypically distinct human MIC was not found in the NOD/SCIDIl2rg(-)/(-) (NSG) mouse model. The demonstration of a distinct population of human melanoma cells responsible for tumorigenesis and tumor cell self-renewal would provide an important target for new melanoma therapies. In this study, we show a 100-fold range in MIC frequency in human melanoma (1 in 18,000 to 1 in 1,851,000 cells) in the NOD/SCID mouse. In this model, human melanoma cells with high aldehyde dehydrogenase (ALDH) activity were enriched 16.8-fold in tumorigenic cells over unfractionated (UNF) cells, such that 1 in 21,000 cells was a MIC. In the NSG mouse, the ALDH expressing cell population was enriched 100-fold in tumorigenic cells over UNF cells, such that one in four cells was a MIC. Xenograft melanomas that developed from ALDH(+) cells displayed robust self-renewal, whereas those from ALDH(-) cells showed minimal self-renewal in vitro. Thus, ALDH(+) melanoma cells have enhanced tumorigenicity over ALDH(-) cells and superior self-renewal ability.