Molecular basis of age-dependent gastric inactivation of rhesus rotavirus in the mouse.

Rotavirus requires specific proteolytic activation by trypsin for efficient replication in tissue culture. To observe the nature of intestinal proteolytic activation of rotavirus in vivo, metabolically labeled rhesus rotavirus (RRV) grown in the presence of trypsin inhibitors was administered to adult and 10-d-old suckling mice by gavage. In the adult stomach, vp4 was cleaved in a manner distinct from in vitro trypsin cleavage. In the suckling stomach, RRV vp4 remains largely uncleaved. The alternative cleavage in the adult stomach was associated with a profound decrease in viral infectivity. vp4 from RRV recovered from the suckling small intestinal lumen was cleaved in a pattern similar or identical to in vitro trypsin-activated virus with bands comigrating with vp5* and vp8*. In contrast, vp4 was not observed in any recognizable form in RRV recovered from adult intestines. Comparison of infectivity of virus recovered from suckling and adult intestines revealed a 10,000-fold decrease in titer in the virus recovered from the adult intestine. In vitro digestions of RRV revealed that pepsin digestion can cleave RRV vp4 and markedly enhance acid-induced loss of rotavirus infectivity. Subsequent digestion with chymotrypsin removes most of the pepsin cleavage products of vp4. Virus injected directly into jejunal loops of adult mice and virus administered orally to adult mice pretreated with antiacid drugs retained infectivity. These studies indicate the development of gastric acid and pepsin secretion may be an important host defense factor in rotavirus gastroenteritis.

Liposome-mediated transfection of intact viral particles reveals that plasma membrane penetration determines permissivity of tissue culture cells to rotavirus.

Rotaviruses are an important cause of gastroenteritis in human infants. In vivo, rotavirus displays striking cell tropism with viral replication generally restricted to the villus tip enterocytes of the small intestine. We studied a panel of cell lines that vary significantly in their permissivity to rotavirus infection. L cells and HEp2 cells were relatively resistant to rotavirus infection compared with permissive Ma104 cells and HT29 cells. RNA transcription among the cell lines was proportional to antigen synthesis making a translational or posttranslational block an unlikely source of observed differences in susceptibility. All of the cell lines bound and internalized radiolabeled virus equally well, as measured by escape from surface protease treatment. Analysis of the escape of cell bound virus from neutralizing monoclonal antibody revealed that rotavirus did not immediately enter an eclipse phase in nonpermissive cells, but was internalized in an infectious form for several hours, possibly sequestered within endocytic vacuoles. L cells and HEp2 cells were as permissive as Ma104 and HT29 cells when rotavirus infection was mediated by transfection of single- or double-shelled rotavirus particles with cationic liposomes (Lipofectin). Rotavirus cell tropism in tissue culture cells is determined by the ability of infecting virions to traverse the plasma membrane of the cells into the cytoplasmic compartment.

Travel vaccines.

Travel-related infectious diseases are exceedingly common, difficult to diagnose, and sometimes preventable. Vaccination is one tool for reducing the risk of infectious disease for some travelers. Both healthcare providers and travelers need to be aware of the new travel vaccines, and new formulations of older vaccines that now are available. This article presents an update on vaccines for cholera, Japanese encephalitis, rabies, rotavirus, typhoid, and malaria.

The transition from caregiving to bereavement: the relationship of care-related strain and adjustment to death.

This study examines two competing hypotheses about the relationship between care-related strain and the difficulty adjusting to the impaired relative's death. One hypothesis, and the limited available empirical evidence, suggests that family members who perceive caregiving as stressful will experience some relief when their relative dies because care responsibilities end. An alternative hypothesis, derived from several conceptualizations, posits the opposite relationship, with greater care-related strain predictive of greater strain during bereavement. Panel data from spouse and adult-child caregivers collected before and after the death support the second hypothesis. Respondents who appraise caregiving as more difficult and those who report more negative caregiving consequences for the family assess bereavement as more difficult and report greater bereavement strain for the family.

The influence of caregiving and bereavement support on adjusting to an older relative's death.

This study examines the influence of both caregiving social support to an impaired older relative and bereavement social support to a surviving caregiver on that caregiver's bereavement adjustment. Although past research has considered the link between bereavement support and adjustment to a loved one's death, the influence of support to the care recipient has not been investigated. Analyses of prospective panel data from 73 spouse and adult-child caregivers show caregiving support characteristics to be more important for bereavement adjustment than support provided to the surviving caregiver after their relative's death.

Predicting the volume of health and social services: integrating cognitive impairment into the modified Andersen framework.

This investigation examined cognitive impairment as a predictor of the volume of community services used by older adults. Predictors of service volume were selected according to the modified Andersen framework and tested with 97 health care and 246 social service clients of a large multiservice agency. Results for health care clients showed that the effects of four predictors differ depending on clients' level of cognitive impairment; living arrangement, presence of secondary caregivers, client depression and task burden of the primary caregiver. No differences in predictor of social service use were observed for cognitively impaired and lucid clients.

The moderating influence of service use on negative caregiving consequences.

This investigation adapts the social support conceptual framework to examine the moderating influence of community service use by impaired older persons on the negative consequences of caregiving for informal helpers. The model is modified by defining services as a type of social support that can counteract the stress associated with various care recipient impairments. Results from multivariate analyses of data from 401 caregivers suggest that certain services for care recipients can reduce the adverse effects of certain impairments on informal caregivers. The use of health care service by care recipients who are more disabled is related to lower levels of caregiver depression, health deterioration, and social isolation. Personal care service use consistently offsets the negative effects of care recipients' behavioral problems. Additionally, the use of household service when care recipients exhibit behavioral problems is associated with lower levels of caregiver depression.

The buffering effect of a computer support network on caregiver strain.

ComputerLink was a computer support network for family caregivers of people with Alzheimer's disease. In a 12-month experiment, 102 caregivers were randomly assigned to an experimental group that had access to ComputerLink or to a control group that did not. This investigation examined whether caregivers in the experimental group had greater reductions in four types of care-related strain by the end of the 1-year study. ComputerLink reduced certain types of strain if caregivers also had larger informal support networks, were spouses, or did not live alone with their care receivers. More frequent use of the communication function was related to significantly reduced strain for caregivers who were initially more stressed and for non-spouse caregivers. Greater use of the information function was related to significantly lower strain among caregivers who lived alone with care receivers. Overall, ComputerLink appeared to be an effective tool for reducing strain for some caregivers.

Predictors of in-home and out-of-home service use by family caregivers of Alzheimer's disease patients.

Few studies have examined whether the use of different types of services is predicted by different characteristics of elderly care recipients and primary kin caregivers. Most research aggregates services into a single category, thereby assuming that different services have the same predictors. This investigation differs from the aggregation approach by comparing four groups of elderly care recipients: in-home service of users, out-of-home service users, users of both in- and out-of-home services, and those who do not use services. Data come from personal interviews with 171 family caregivers of mild to moderate dementia patients who reside in the community. Using the modified Andersen framework and multiple group discriminant analysis, results show that care recipients who do not use services and those using only in-home services have inadequate informal supports, more emotionally strained caregivers, and more functionally impaired care recipients compared with users of out-of-home or both in- and out-of-home services.

Care-related stress. A comparison of spouse and adult-child caregivers in shared and separate households.

This research examines the role that relationship and household arrangement have in explaining the levels of care-related stress effects experienced by spouse and adult-child caregivers in shared and separate residences. Data from 180 spouse and adult-child caregivers were analyzed to identify differences in caregiver health decline, relationship strain, and activity restriction across these settings when the effects of elder impairment, caregiver age, and use of social supports are controlled. Results show that spouse and adult children in shared households experience similar levels of care-related strain. However, comparison of adult children in shared and separate households show considerable cross-setting differences in strain, with those in shared households having significantly greater activity restriction but less relationship strain. These findings have implications for the delivery of social services, specifically for targeting health monitoring, respite, and family counseling services.

Interferon gamma and interleukin 1, but not interferon alfa, inhibit rotavirus entry into human intestinal cell lines.

BACKGROUND & AIMS: Rotavirus, an important agent of gastroenteritis in children, causes diarrhea by infecting differentiated villus enterocytes in the small intestine. The aim of this study was to determine whether cytokines that can be expressed by mucosal cells have an effect on the rotavirus susceptibility of cultured human enterocytes. METHODS: Caco-2 and HT-29 cells were pretreated with various cytokines before challenge with rotavirus. RESULTS: Interleukin (IL)-1, interferon (IFN)-alpha, and IFN-gamma pretreatment led to a dose-dependent resistance to rotavirus infection. Maximum effects occurred after 72 hours of pretreatment, whereas no detectable inhibition occurred with <12 hours of pretreatment. Liposomal transfection of single-shelled and double-shelled rotavirus particles bypassed the block to rotavirus replication in IFN-gamma- and IL-1-treated but not IFN-alpha-treated cells. Binding studies with purified, metabolically labeled rotavirus showed no significant difference among IFN-gamma- and IFN-alpha-treated and control Caco-2 cells. Viral entry into Caco-2 cells was significantly inhibited by IFN-gamma and IL-1 but not IFN-alpha. CONCLUSIONS: IFN-alpha and IFN-gamma induce rotavirus resistance by different mechanisms, suggesting that cytokines play a role in host defense against viral agents by changing the phenotype of intestinal epithelial cells.

Service use by caregivers of elderly receiving case management.

This article reports on findings from survey interviews with 401 informal caregivers of impaired older persons who were clients of nonprofit case management agencies in Cleveland, OH. The issue addressed is the role of the case manager as a facilitator of caregiver service use when the older person receives case management service. Caregiver services under investigation include respite care, help finding or arranging for service, emotional support or counseling, caregiver education and training, and assistance with other responsibilities such as child care. The study questions are: to what extent do caregivers in this sample utilize these services? What are the predictors of caregiver service use? What implications do the findings have for case management practice?

Symptoms of mental impairment among elderly adults and their effects on family caregivers.

Research that has examined the relationship between caregiving stress and elders' symptoms of mental impairment has focused primarily on cognitive incapacity. This research expands the symptoms of mental impairment to include caregivers' reports of problems in elders' social functioning and the presence of disruptive behavior, in addition to the traditional measure of cognitive incapacity. Results from a study of 614 families living with and caring for an impaired elder show cognitive incapacity to have a less important direct effect on caregiving stress than disruptive behavior and impaired social functioning. Cognitive incapacity does have an important indirect effect through its influence on disruptive behavior and social functioning.

Characterization of human serotype 1 astrovirus-neutralizing epitopes.

Astroviruses are important agents of pediatric gastroenteritis. To better understand astrovirus antigenic structure and the basis of protective immunity, monoclonal antibodies (MAbs) were produced against serotype 1 human astrovirus. Four MAbs were generated. One MAb (8G4) was nonneutralizing but reacted to all seven serotypes of astrovirus by enzyme-linked immunosorbentassay (ELISA) and immunoperoxidase staining of infected cells. Three MAbs were found to have potent neutralizing activity against astrovirus. The first (5B7) was serotype 1 specific, another (7C2) neutralized all seven human astrovirus serotypes, while the third (3B2) neutralized serotypes 1 and 7. Immunoprecipitation of radiolabeled astrovirus proteins from supernatants of astrovirus-infected cells showed that all three neutralizing antibodies reacted with VP29. MAb 5B7 also reacted strongly with VP26. A competition ELISA showed that all three neutralizing antibodies competed with each other for binding to purified astrovirus virions, suggesting that their epitopes were topographically in close proximity. None of the neutralizing MAbs competed with nonneutralizing MAb 8G4. The neutralizing MAbs were used to select antigenic variant astroviruses, which were then studied in neutralization assays. These assays also suggested a close relationship between the respective epitopes. All three neutralizing MAbs were able to prevent attachment of radiolabeled astrovirus particles to human Caco 2 intestinal cell monolayers. Taken together, these data suggest that the astrovirus capsid protein VP29 may be important in viral neutralization, heterotypic immunity, and virus attachment to target cells.

Home care for elderly persons: linkages between formal and informal caregivers.

Prior research has generally focused on characteristics of elderly persons that predict contact with community services or the volume of services used. In contrast, this study investigates how personal care and home health services are used in relation to assistance from primary kin caregivers. A typology was developed based on task sharing or segregation between kin caregivers and service providers, and four types of informal-formal linkages around these tasks were identified: kin independence, formal service specialization, dual specialization, and supplementation. Findings regarding predictors of the types showed that caregiver and care recipient need variables were most significant in differentiating among them, although caregiver gender also had some discriminatory power.

Proteolytic processing of the astrovirus capsid.

To further characterize the nature of proteolytic processing of the astrovirus capsid, we infected Caco-2 cells with a high multiplicity of astrovirus without trypsin in the presence of 5 to 10% fetal calf serum. These infections were characterized by pulse-chase labeling with [35S]Smethionine, electron microscopy, gel electrophoresis of purified viral particles, and analysis of infectivity of such particles with and without added trypsin. Pulse-chase experiments showed that the astrovirus capsid protein was initially translated as an approximately 87-kDa protein. The 87-kDa capsid protein was rapidly converted intracellularly to a 79-kDa form which was found in smaller amounts in the cell supernatant. Purification by differential centrifugation yielded particles that appeared quite similar to trypsin-grown astrovirus particles by negatively stained electron microscopy. These particles were antigenically distinct from trypsin-treated virions as demonstrated by their various reactions with monoclonal antibodies in a solid-phase immunoassay. The purified trypsin-free particles were mainly composed of the 79-kDa capsid protein which was found to have an amino terminus at residue 71 of the entire open reading frame 2 (ORF2) product. The cleavage site was identified in a highly conserved region of the astrovirus ORF2 product. These trypsin-free particles were minimally infectious in cultured Caco-2 cells but became highly infectious (10(5)-fold increase) after trypsin but not chymotrypsin treatment. This trypsin-enhanced infectivity correlated with conversion of the 79-kDa capsid protein to three smaller peptides of approximately 34, 29, and 26 kDa.

Murine intestinal mucins inhibit rotavirus infection.

BACKGROUND: Mucin, a population of polymeric glycoproteins, constitutes the primary component of the mucus layer that overlies the gastrointestinal tract. These studies aimed to determine whether murine intestinal mucins inhibit rotavirus infection. METHODS: Murine intestinal mucins were obtained by scraping segments of mouse intestine and purification via CsCl gradient centrifugation and sepharose 4B chromatography. Inhibition of infection was determined by quantitation of immunoperoxidase-stained cells after infection with mucin-rotavirus mixtures. RESULTS: Crude and purified intestinal mucins from suckling and adult mice are potent inhibitors of replication of a simian rotavirus, rhesus rotavirus (RRV), but weak inhibitors of other rotaviruses. In all preparations, colonic mucins were more potent inhibitors of RRV than small intestinal mucins. Suckling mucins neutralized RRV more effectively than adult mucins. In a panel of rotavirus reassortants, susceptibility to mucin inhibition correlated with the ability to hemagglutinate human type O erythrocytes and with RRV gene 4. Murine intestinal mucin inhibited RRV binding to MA104 cells, suggesting inhibition of virus-cell attachment to be the mechanism for neutralization. Mercaptoethanol or neuraminidase inhibited mucins' anti-RRV activities, implying the functional importance of mucins' polymeric structure and sialic acid content. CONCLUSIONS: These findings suggest that intestinal mucins represent a barrier to certain rotavirus infections.