Interactions between viruses and the host antibody immune response are critical in the development and control of disease, and antibodies are also known to interfere with the efficacy of viral vector-based gene delivery. The adeno-associated viruses (AAVs) being developed as vectors for corrective human gene delivery have shown promise in clinical trials, but preexisting antibodies are detrimental to successful outcomes. However, the antigenic epitopes on AAV capsids remain poorly characterized. Cryo-electron microscopy and three-dimensional image reconstruction were used to define the locations of epitopes to which monoclonal fragment antibodies (Fabs) against AAV1, AAV2, AAV5, and AAV6 bind. Pseudoatomic modeling showed that, in each serotype, Fabs bound to a limited number of sites near the protrusions surrounding the 3-fold axes of the T=1 icosahedral capsids. For the closely related AAV1 and AAV6, a common Fab exhibited substoichiometric binding, with one Fab bound, on average, between two of the three protrusions as a consequence of steric crowding. The other AAV Fabs saturated the capsid and bound to the walls of all 60 protrusions, with the footprint for the AAV5 antibody extending toward the 5-fold axis. The angle of incidence for each bound Fab on the AAVs varied and resulted in significant differences in how much of each viral capsid surface was occluded beyond the Fab footprints. The AAV-antibody interactions showed a common set of footprints that overlapped some known receptor-binding sites and transduction determinants, thus suggesting potential mechanisms for virus neutralization by the antibodies.
Polyomaviruses are ubiquitous pathogens that cause severe disease in immunocompromised individuals. JC polyomavirus (JCPyV) is the causative agent of the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML), whereas BK polyomavirus (BKPyV) causes polyomavirus-induced nephropathy and hemorrhagic cystitis. Vaccines or antiviral therapies targeting these viruses do not exist, and treatments focus on reducing the underlying causes of immunosuppression. We demonstrate that retro-2cycl, an inhibitor of ricin and Shiga-like toxins (SLTs), inhibits infection by JCPyV, BKPyV, and simian virus 40. Retro-2cycl inhibits retrograde transport of polyomaviruses to the endoplasmic reticulum, a step necessary for productive infection. Retro-2cycl likely inhibits polyomaviruses in a way similar to its ricin and SLT inhibition, suggesting an overlap in the cellular host factors used by bacterial toxins and polyomaviruses. This work establishes retro-2cycl as a potential antiviral therapy that broadly inhibits polyomaviruses and possibly other pathogens that use retrograde trafficking.
The human polyomaviruses JC polyomavirus (JCPyV) and BK polyomavirus (BKPyV) cause rare but severe diseases in individuals with reduced immune function. During immunosuppression, JCPyV disseminates from the kidney to the central nervous system and destroys oligodendrocytes, resulting in the fatal disease progressive multifocal leukoencephalopathy. Kidney transplant recipients are at increased risk of BKPyV-induced nephropathy, which results in kidney necrosis and loss of the transplanted organ. There are currently no effective therapies for JCPyV and BKPyV. We show that a small molecule named retro-2cycl protects cells from infection with JCPyV and BKPyV by inhibiting intracellular viral transport. Retro-2cycl treatment reduces viral spreading in already established infections and may therefore be able to control infection in affected patients. Further optimization of retro-2cycl may result in the development of an effective antiviral therapy directed toward pathogens that use retrograde trafficking to infect their hosts.
The impact of psychosocial research participation has not been examined systematically in palliative care settings. Concerns are often raised regarding the potential for distress among terminally ill patients. This is particularly true when death and dying are the focus of research. Therefore, it is important to understand the specific ways psychosocial research could potentially harm or be helpful to participants.
To assess the burden and benefits of participation in psychosocial research addressing end-of-life issues among patients receiving inpatient palliative care.
Sixty-eight terminally ill patients with cancer who had an average life expectancy of less than 2 months, were administered a brief self-report questionnaire to assess whether participation in psychosocial research was burdensome and/or beneficial. The specific factors that contributed to their perceptions were also identified.
The majority of patients reported no burden associated with participation (75%) and found the experience as moderately to highly beneficial (68%). Factors most frequently identified as burdensome included the length of the interview (21%), structure of the questionnaires (18%), and difficulty discussing end-of life issues (12%). Although some patients reported some distress while discussing end-of-life issues (19%), few endorsed a high level of distress (6%). Factors most frequently identified as beneficial were the social interaction (75%), sense of contributing to society (57%), and the opportunity to discuss their illness (47%).
Participants in psychosocial end-of-life research are unlikely to experience significant burden from participation and, in fact, may benefit.
Summary: Progressive multifocal leukoencephalopathy (PML) is a debilitating and frequently fatal central nervous system (CNS) demyelinating disease caused by JC virus (JCV), for which there is currently no effective treatment. Lytic infection of oligodendrocytes in the brain leads to their eventual destruction and progressive demyelination, resulting in multiple foci of lesions in the white matter of the brain. Before the mid-1980s, PML was a relatively rare disease, reported to occur primarily in those with underlying neoplastic conditions affecting immune function and, more rarely, in allograft recipients receiving immunosuppressive drugs. However, with the onset of the AIDS pandemic, the incidence of PML has increased dramatically. Approximately 3 to 5% of HIV-infected individuals will develop PML, which is classified as an AIDS-defining illness. In addition, the recent advent of humanized monoclonal antibody therapy for the treatment of autoimmune inflammatory diseases such as multiple sclerosis (MS) and Crohn's disease has also led to an increased risk of PML as a side effect of immunotherapy. Thus, the study of JCV and the elucidation of the underlying causes of PML are important and active areas of research that may lead to new insights into immune function and host antiviral defense, as well as to potential new therapies.
JC polyomavirus (JCV) is an important human pathogen that causes the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML). In this study we further delineate the early events of JCV entry in human glial cells and demonstrate that a pentameric subunit of the viral capsid is able to recapitulate early events in viral trafficking. We show that JCV traffics to the endoplasmic reticulum (ER) by 6 h post infection, and that VP1 pentamers arrive at the ER with similar kinetics. Further, this JCV localization to the ER is critical for infection, as treatment of cells with agents that prevent ER trafficking, ER function, or ER quality control reduce JCV infectivity. These pentamers represent a new tool to study polyomavirus entry, and will be particularly useful in studying recently identified polyomaviruses that are difficult to propagate.
JC polyomavirus; Endoplasmic reticulum; Trafficking; Endocytosis
An increasingly important concern for clinicians who care for patients at the end of life is their spiritual well-being and sense of meaning and purpose in life. In response to the need for short-term interventions to address spiritual well-being, we developed Meaning Centered Group Psychotherapy (MCGP) to help patients with advanced cancer sustain or enhance a sense of meaning, peace and purpose in their lives, even as they approach the end of life.
Patients with advanced (stage III or IV) solid tumor cancers (N = 90) were randomly assigned to either MCGP or a supportive group psychotherapy (SGP). Patients were assessed before and after completing the 8-week intervention, and again 2 months after completion. Outcome assessment included measures of spiritual well-being, meaning, hopelessness, desire for death, optimism/pessimism, anxiety, depression and overall quality of life.
MCGP resulted in significantly greater improvements in spiritual well-being and a sense of meaning. Treatment gains were even more substantial (based on effect size estimates) at the second follow-up assessment. Improvements in anxiety and desire for death were also significant (and increased over time). There was no significant improvement on any of these variables for patients participating in SGP.
MCGP appears to be a potentially beneficial intervention for patients’ emotional and spiritual suffering at the end of life. Further research, with larger samples, is clearly needed to better understand the potential benefits of this novel intervention.
psychotherapy; meaning; spiritual well-being; palliative care; existential
Fatigue is a highly prevalent and clinically significant symptom of advanced prostate cancer. To date, however, there are no published controlled trials of interventions for fatigue in men with prostate cancer.
This six-week, randomized, double-blind, placebo-controlled design, evaluated the efficacy of methylphenidate to treat fatigue in prostate cancer patients. Inclusion criteria included men with advanced prostate cancer and the presence of moderate to severe fatigue. Patients with major depression, hypothyroidism, uncontrolled hypertension, arrhythmia or anemia were excluded. Fatigue levels, blood pressure, pulse and other safety concerns were monitored regularly.
Thirty-two subjects were randomized to methylphenidate (N=16) or placebo (N=16). Brief Fatigue Inventory (BFI) total scores significantly decreased for both groups, however the methylphenidate group, as compared to placebo, reported greater decrease on BFI severity scores (p=.03) and a trend toward greater decrease on BFI total scores (p=.07). A significantly greater number of subjects in the methylphenidate group vs. the placebo group demonstrated clinically significant improvement in fatigue on total BFI scores (7/10 vs. 3/13) and BFI severity scores (8/10 vs. 3/13). Importantly, six subjects in the methylphenidate group discontinued due to increased blood pressure or tachycardia. There were no serious adverse events.
Methylphenidate is effective in treating fatigue in men with prostate cancer; however, oncologists need to monitor for possible pulse and blood pressure elevations.
The kinetochore is the macromolecular complex that assembles onto centromeric DNA and orchestrates the segregation of duplicated chromosomes. More than 60 components make up the budding yeast kinetochore, including inner kinetochore proteins that bind to centromeric chromatin and outer proteins that directly interact with microtubules. However, little is known about how these components assemble into a functional kinetochore and whether there are quality control mechanisms that monitor kinetochore integrity. We previously developed a method to isolate kinetochore particles via purification of the conserved Dsn1 kinetochore protein. We find that the Mub1/Ubr2 ubiquitin ligase complex associates with kinetochore particles through the CENP-CMif2 protein. Although Mub1/Ubr2 are not stable kinetochore components in vivo, they regulate the levels of the conserved outer kinetochore protein Dsn1 via ubiquitylation. Strikingly, a deletion of Mub1/Ubr2 restores the levels and viability of a mutant Dsn1 protein, reminiscent of quality control systems that target aberrant proteins for degradation. Consistent with this, Mub1/Ubr2 help to maintain viability when kinetochores are defective. Together, our data identify a previously unknown regulatory mechanism for the conserved Dsn1 kinetochore protein. We propose that Mub1/Ubr2 are part of a quality control system that monitors kinetochore integrity, thus ensuring genomic stability.
The flawless execution of cell division is essential to the survival of all organisms. The loss or gain of a single chromosome, the state called aneuploidy, is a hallmark of cancer cells and is the leading cause of spontaneous miscarriages and hereditary birth defects. Segregation is mediated by the kinetochore, the macromolecular complex that assembles on each chromosome and attaches to spindle microtubules to pull chromosomes to opposite poles when cells divide. It is therefore critical to understand how kinetochores are assembled and maintained. Here, we find that the levels of a conserved kinetochore protein are regulated by proteolysis. We propose that cells have quality control systems that ensure kinetochore integrity and thus genome stability.
To determine factors associated with students’ comfort in addressing patients’ sexuality in the clinical context.
The authors invited students enrolled in MD-degree-granting and osteopathic medical schools in the United States and Canada to participate in an anonymous Internet survey between February and July 2008. The survey assessed ethnodemographic factors and sexual history. Respondents also completed the Center for Epidemiologic Studies Depression Scale. Male respondents completed the International Index of Erectile Function and the Premature Ejaculation Diagnostic Tool. Female respondents completed the Female Sexual Function Index and the Index of Sex Life. The authors used descriptive statistics, ANOVA, and multivariable logistic regression to analyze responses.
The authors’ analyses included 2,261 completed survey responses: 910 from men, 1,343 from women, and 8 from individuals who self-identified as “other” gendered. Over 53% of respondents (n = 1,206) stated that they felt they had not received sufficient training in medical school to address sexual concerns clinically. Despite this, 81% of students (n = 1,827) reported feeling comfortable dealing with their patients’ sexuality issues. Students with limited sexual experience, students at risk for sexual problems, and students who felt that they had not been trained adequately were less likely to report being comfortable talking to patients about sexual health issues.
Perception of inadequate sexuality training in medical school and personal issues pertaining to sex may be associated with students’ difficulty in addressing patients’ sexuality. Adequate training is preeminently associated with feeling comfortable addressing patients’ sexuality and should be a priority for medical education.
Avian polyomavirus (APV) causes a fatal, multi-organ disease among several bird species. Using cryogenic electron microscopy and other biochemical techniques, we investigated the structure of APV and compared it to that of mammalian polyomaviruses, particularly JC polyomavirus and simian virus 40. The structure of the pentameric major capsid protein (VP1) is mostly conserved; however, APV VP1 has a unique, truncated C-terminus that eliminates an intercapsomere-connecting β-hairpin observed in other polyomaviruses. We postulate that the terminal β-hairpin locks other polyomavirus capsids in a stable conformation and that absence of the hairpin leads to the observed capsid size variation in APV. Plug-like density features were observed at the base of the VP1 pentamers, consistent with the known location of minor capsid proteins VP2 and VP3. However, the plug density is more prominent in APV and may include VP4, a minor capsid protein unique to bird polyomaviruses.
arginine; capsomere connections; cryo-electron microscopy; homology model; human JC polyomavirus; simian virus 40; size-exclusion chromatography; three-dimensional reconstruction; virus assembly; virus structure
To review the literature on depression in cancer patients with a particular focus on depression assessment and barriers to mental health treatment in older cancer patients.
We conducted a review of the literature on depression and barriers to mental health treatment in older cancer patients.
Depression is prevalent in cancer patients. However, little is known about prevalence rates of depression in older adults with cancer, assessing depression in older cancer patients and barriers that impede proper mental health treatment in this sample.
Improved diagnostic clarity and a better understanding of barriers to mental health treatment can help clarify and facilitate mental health referrals and ultimately improve access to care among older cancer patients in need. Continuing to consider the complexities associated with diagnosing depression in older cancer patients is necessary. Further work may be needed to develop new diagnostic measures for such detection, determine the prevalence of depression among older cancer and ways in which to overcome barriers to mental health care.
depression; cancer; older; barriers to mental health treatment; assessment
The human JC polyomavirus (JCV) causes a fatal demyelinating disease, Progressive Multifocal Leukoencephalopathy (PML), in immunocompromised individuals. Current treatment options for PML are inadequate. Sialylated oligosaccharides and the serotonin receptor are known to be necessary for JCV entry, but the molecular interactions underlying JCV attachment remain unknown. Using glycan array screening and viral infectivity assays, we identify a linear sialylated pentasaccharide with the sequence NeuNAc-α2,6-Gal-β1,4-GlcNAc-β1,3-Gal-β1,4-Glc (LSTc) present on host glycoproteins and glycolipids as a specific JCV recognition motif. The crystal structure of the JCV capsid protein VP1 was solved alone and in complex with LSTc. It reveals extensive interactions with the terminal sialic acid of the LSTc motif and specific recognition of an extended conformation of LSTc. Mutations in the JCV oligosaccharide binding sites abolish cell attachment, viral spread and infectivity, further validating the importance of this interaction. Our findings provide a powerful platform for the development of antiviral compounds.
Kinetochores are macromolecular machines that couple chromosomes to dynamic microtubule tips during cell division, thereby generating force to segregate the chromosomes1,2. Accurate segregation depends on selective stabilization of correct ‘bi-oriented’ kinetochore-microtubule attachments, which come under tension due to opposing forces exerted by microtubules3. Tension is thought to stabilize these bi-oriented attachments indirectly, by suppressing the destabilizing activity of a kinase, Aurora B4,5. However, a complete mechanistic understanding of the role of tension requires reconstitution of kinetochore-microtubule attachments for biochemical and biophysical analyses in vitro. Here we show that native kinetochore particles retaining the majority of kinetochore proteins can be purified from budding yeast and used to reconstitute dynamic microtubule attachments. Individual kinetochore particles maintain load-bearing associations with assembling and disassembling ends of single microtubules for >30 min, providing a close match to the persistent coupling seen in vivo between budding yeast kinetochores and single microtubules6. Moreover, tension increases the lifetimes of the reconstituted attachments directly, via a catch bond-like mechanism that does not require Aurora B7-10. Based on these findings, we propose that tension selectively stabilizes proper kinetochore-microtubule attachments in vivo through a combination of direct mechanical stabilization and tension-dependent phosphoregulation.
This review article discusses the complexities of diagnosing depression in older, geriatric cancer patients. There has been little research conducted with this population on the assessment, recognition and treatment of depression, and thus increased attention is required to improve care for these individuals. Depressive symptoms often manifest themselves differently in both cancer patients and in older patients, and therefore a modified and adapted way of assessment must be employed when thinking about diagnosing and treating these patients.
Depression Diagnosis; Cancer; Geriatrics
The present study evaluated intimacy as a mechanism for the effects of relationship-enhancing (self-disclosure, mutual constructive communication) and relationship-compromising communication (holding back, mutual avoidance, and demand-withdraw communication) on couples' psychological distress.
Seventy-five men diagnosed with localized prostate cancer in the past year and their partners completed surveys about communication, intimacy, and distress.
Multi-level models with the couple as unit of analyses indicated that the association between mutual constructive communication, mutual avoidance, and patient demand-partner withdraw and distress could be accounted for by their influence on relationship intimacy. Self-disclosure, holding back, and partner demand-patient withdraw did not mediate the associations between communication and distress.
These findings indicate that the way in which couples talk about as well as the degree to which one or both partners avoid talking about cancer-related concerns can either facilitate or reduce relationship closeness, and that it is largely by this mechanism that these three communication strategies impact psychological distress.
Implications for Cancer Survivors
Relationship intimacy and how patients and partners communicate to achieve this intimacy is important for the psychological adjustment of early stage prostate cancer survivors and their partners.
Couple communication; relationship intimacy; prostate cancer
Geriatric issues in cancer are becoming prominent. Depression is a significant concern for both the elderly and patients with cancer, yet identifying depression in these patients is difficult and often leads to under-recognition. We conducted a systematic review to determine which depression instruments are appropriate for use in geriatric patients with cancer.
We identified the most commonly used self-report depression instruments. We then used the criteria established in the US Food and Drug Administration Draft Guidance on Patient-Reported Outcome Measures to determine the extent of validation evidence of these measures in geriatric cancer populations. Finally, we determined which instruments captured depressive symptoms that are common among elderly patients with cancer.
Eight measures were selected as the most commonly used instruments. These were the Beck Depression Inventory-II, Brief Symptom Inventory-18, Center for Epidemiologic Studies–Depression Scale, Geriatric Depression Scale-15, Hospital Anxiety and Depression Scale, Patient Health Questionnaire-9, Profile of Mood States–Short Form, and Zung Self-Rating Depression Scale. Many have been validated for use with geriatric adults and patients with cancer; however, data addressing content validity and responder definition were lacking. To date, there is no validation information for geriatric patients with cancer. Furthermore, symptom profile analysis revealed that these measures do not identify many symptoms signaling depression in geriatric patients with cancer.
The validation evidence for use of common depression instruments in geriatric patients with cancer is lacking. This, and the possibility that these measures may not assess common depressive symptoms in geriatric patients with cancer, questions the adequacy of these scales in this population.
This study aims to develop a theoretical framework of the relationship among religiosity, spirituality, and depression, potentially explaining the often mixed and inconsistent associations between religiosity and depression.
In this cross-sectional study, 367 men (average age of 66 ± 9 years) with prostate cancer completed measures of religiosity (extrinsic/intrinsic), spirituality (FACIT Spiritual Well-Being Scale), quality of life (FACT-G) and depression (Hospital Anxiety and Depression Scale).
There was a small relationship between intrinsic religiosity and depression (r = −0.23, p<0.05) but a strong association between spirituality and depression (r = −0.58, p<0.01). Using a mediation model, the meaning/peace subscale of the spirituality measure mediated the relationship between intrinsic religiosity and depression. This model controlled for age, marital status, stage of disease, time since diagnosis, hormone therapy, quality of life, and anxiety.
When examining religiosity and spirituality, the main component that may help reduce depression is a sense of meaning and peace. These results highlight the potential importance of developing a patient’s sense of meaning through activities/interventions (not exclusive to religious involvement) to achieve this goal.
To determine the predictors of distress in older patients with cancer.
Patients and Methods
Patients age ≥ 65 years with a solid tumor or lymphoma completed a questionnaire that addressed these geriatric assessment domains: functional status, comorbidity, psychological state, nutritional status, and social support. Patients self-rated their level of distress on a scale of zero to 10 using a validated screening tool called the Distress Thermometer. The relationship between distress and geriatric assessment scores was examined.
The geriatric assessment questionnaire was completed by 245 patients (mean age, 76 years; standard deviation [SD], 7 years; range, 65 to 95 years) with cancer (36% stage IV; 71% female). Of these, 87% also completed the Distress Thermometer, with 41% (n = 87) reporting a distress score of ≥ 4 on a scale of zero to 10 (mean score, 3; SD, 3; range, zero to 10). Bivariate analyses demonstrated an association between higher distress (≥ 4) and poorer physical function, increased comorbid medical conditions, poor eyesight, inability to complete the questionnaire alone, and requiring more time to complete the questionnaire. In a multivariate regression model based on the significant bivariate findings, poorer physical function (increased need for assistance with instrumental activities of daily living [P = .015] and lower physical function score on the Medical Outcomes Survey [P = .018]) correlated significantly with a higher distress score.
Significant distress was identified in 41% of older patients with cancer. Poorer physical function was the best predictor of distress. Further studies are needed to determine whether interventions that improve or assist with physical functioning can help to decrease distress in older adults with cancer.
Current research suggests that older cancer patients report less distress compared to younger cancer patients. However, this research has generally not teased apart the differences between general distress, anxiety, and depression.
We conducted a secondary analysis of merged datasets using cross-sectional data on 736 men with prostate cancer (Mean Age 68±10 years of age, range 50 to 93). Approximately half the participants were recruited from doctors’ offices throughout the United States and the other half from Memorial Sloan-Kettering Cancer Center (New York, NY). Participants were asked to complete the Distress Thermometer, the Hospital Anxiety and Depression Scale (HADS), the FACT-P Quality of Life questionnaire, and a demographic questionnaire.
Aging was related to reduced distress (r=−0.14), less anxiety (r=−0.22), and increased emotional quality of life (r= 0.16). In contrast, aging was associated with greater depressive symptoms in these cancer patients (r= 0.18). The mean depression scores of 5-year cohorts consistently trended upward. The significant association between age and depression remained after controlling for stage of disease, hormone therapy use, time since diagnosis, and social, physical and functional well-being.
Despite theoretical and empirical evidence that older cancer patients may cope more effectively than younger cancer patients, depressive symptoms remain an important concern for aging cancer patients and greater attention to this area is warranted. The increase in depression is in contrast to some findings in the general aging literature, raising the possibility that this trend is unique to older cancer patients.
Psychological distress; Depression; Anxiety; Prostate Cancer; Aging
Accurate chromosome segregation depends on sister kinetochores coming under tension when they make bioriented attachments to microtubules from opposite poles. The spindle checkpoint halts the cell cycle in response to defects in generating proper attachments or tension on kinetochores [1, 2], although the precise signal that triggers the checkpoint is unclear because tension and attachment are coupled . The target of the checkpoint is the Cdc20 protein that initiates the anaphase promoting complex (APC)-dependent degradation of the anaphase inhibitor Pds1/securin . Although the molecular details of spindle checkpoint activation are still being elucidated, phosphorylation by at least four kinases is a crucial requirement . However, less is known about the mechanisms that silence the checkpoint once kinetochores biorient. Here, we show that the catalytic subunit of the budding yeast protein phosphatase I, Glc7, regulates exit from the checkpoint. Glc7 overexpression prevents spindle checkpoint activation in response to both tension and attachment defects. Although glc7 mutant cells are able to efficiently release from a non-checkpoint-mediated metaphase arrest, they are uniquely sensitive to transient spindle checkpoint activation due to a failure in spindle checkpoint exit. We therefore propose that PP1 activity silences the checkpoint by reversing key phosphorylation events.
The current review summarizes some of the key psychosocial issues related to prostate cancer both generally and for an older adult population. The review focuses on three main areas: (1) quality of life issues, (2) psychosocial implications and (3) treatment choices. More generally, the article presents information on the general background, screening guidelines, common side effects of treatment, and current psychiatric and psychological management strategies in prostate cancer. The article addresses the clinical approaches as well as the complexities that surface when deciding the treatment for patients with prostate cancer. Clinical and future implications are discussed.
prostate cancer; treatment; psychiatric management
The structures of canine parvovirus (CPV) and feline parvovirus (FPV) complexed with antibody fragments from eight different neutralizing monoclonal antibodies were determined by cryo-electron microscopy (cryoEM) reconstruction to resolutions varying from 8.5 to 18 Å. The crystal structure of one of the Fab molecules and the sequence of the variable domain for each of the Fab molecules have been determined. The structures of Fab fragments not determined crystallographically were predicted by homology modeling according to the amino acid sequence. Fitting of the Fab and virus structures into the cryoEM densities identified the footprints of each antibody on the viral surface. As anticipated from earlier analyses, the Fab binding sites are directed to two epitopes, A and B. The A site is on an exposed part of the surface near an icosahedral threefold axis, whereas the B site is about equidistant from the surrounding five-, three-, and twofold axes. One antibody directed to the A site binds CPV but not FPV. Two of the antibodies directed to the B site neutralize the virus as Fab fragments. The differences in antibody properties have been linked to the amino acids within the antibody footprints, the position of the binding site relative to the icosahedral symmetry elements, and the orientation of the Fab structure relative to the surface of the virus. Most of the exposed surface area was antigenic, although each of the antibodies had a common area of overlap that coincided with the positions of the previously mapped escape mutations.
Parvovirus capsids are assembled from multiple forms of a single protein and are quite stable structurally. However, in order to infect cells, conformational plasticity of the capsid is required and this likely involves the exposure of structures that are buried within the structural models. The presence of functional asymmetry in the otherwise icosahedral capsid has also been proposed. Here we examined the protein composition of canine parvovirus capsids and evaluated their structural variation and permeability by protease sensitivity, spectrofluorometry, and negative staining electron microscopy. Additional protein forms identified included an apparent smaller variant of the virus protein 1 (VP1) and a small proportion of a cleaved form of VP2. Only a small percentage of the proteins in intact capsids were cleaved by any of the proteases tested. The capsid susceptibility to proteolysis varied with temperature but new cleavages were not revealed. No global change in the capsid structure was observed by analysis of Trp fluorescence when capsids were heated between 40°C and 60°C. However, increased polarity of empty capsids was indicated by bis-ANS binding, something not seen for DNA-containing capsids. Removal of calcium with EGTA or exposure to pHs as low as 5.0 had little effect on the structure, but at pH 4.0 changes were revealed by proteinase K digestion. Exposure of viral DNA to the external environment started above 50°C. Some negative stains showed increased permeability of empty capsids at higher temperatures, but no effects were seen after EGTA treatment.
Over the past decade, Prigerson and her colleagues have shown that symptoms of ‘complicated grief’—intense yearning, difficulty accepting the death, excessive bitterness, numbness, emptiness, and feeling uneasy moving on and that the future is bleak—are distinct from depression and anxiety and are independently associated with substantial morbidity. Little is known about complicated grief experienced by family caregivers prior to the death. This study sought to examine differences in caregiver age groups and potential risk factors for complicated grief pre-death.
Two hundred and forty eight caregivers from multiple sites nationwide (20–86 years of age) identified themselves as primary caregivers to a terminally ill cancer patient. Each caregiver was interviewed using the following measures: the Pre-Death Inventory of Complicated Grief-Caregiver Version; the Brief Interpersonal Support Evaluation List; the Structured Clinical Interview for the DSM-IV Axis I; the Life Orientation Test-Revised; the SEPRATE Measure of Stressful Life Events; the Covinsky Family Impact Survey; and mental health access questions.
The study found that those under 60 years old had higher levels of complicated grief pre-death than caregivers 60 and older (t(246) = 2.30, p<0.05). Significant correlations were also found between levels of complicated grief pre-loss and the following psychosocial factors: perceived social support (r = −0.415, p<0.001); history of depression (r = −0.169, p<0.05); current depression (r = −0.158, p<0.05); current annual income (Spearman rho = −0.210, p<0.01); annual income at time of patient's diagnosis (Spearman rho = −0.155, p = 0.05); pessimistic thinking (r = 0.320; p<0.001); and number of moderate to severe stressful life events (Spearman rho = 0.218, p = 0.001). In a multi-variate analysis (R2 = 0.368), pessimistic thinking (Beta = 0.208, p<0.05) and severity of stressful life events (Beta = 0.222, p<0.05) remained as important factors to developing complicated grief pre-death.
These results suggest that mental health professionals who work with caregivers should pay particular attention to pessimistic thinking and stressful life events, beyond the stress of the loved one's illness, that caretakers experience. Additionally, although not reaching significance, mental health professionals should also consider younger caregivers at greater risk for complicated grief pre-loss.
cancer; oncology; caregivers; complicated grief; pre-death
Antibody binding and neutralization are major host defenses against viruses, yet the mechanisms are often not well understood. Eight monoclonal antibodies and their Fab fragments were tested for neutralization of canine parvovirus and feline panleukopenia virus. All IgGs neutralized >90 percent of virus infectivity. Two Fabs neutralized when present at 5 nM, while the others gave little or no neutralization even at 20–100 nM. The antibodies bind two antigenic sites on the capsids which overlap the binding site of the host transferrin receptor (TfR). There was no specific correlation between Fab binding affinity and neutralization. All Fabs reduced capsid binding of virus to purified feline TfR in vitro, but the highly neutralizing Fabs were more efficient competitors. All partially prevented binding and uptake of capsids by feline TfR on cells. The virus appears adapted to allow some infectivity in the presence of at least low levels of antibodies.
antibody; immunity; neutralization; canine parvovirus; feline panleukopenia virus