Critical features of antigen-specific and allospecific recognition by cytotoxic T lymphocytes

In general, CD8+ T lymphocytes respond to a single class I MHC/peptide complex, a phenomenon known as MHC self-restriction . We previously reported that CD8+ CTLs from C57BL/6 mice were restricted to both H-2Kb and H-2Db when responding to the horse cyt c-derived peptide, p41--49. In Part I of this dissertation, we examine structural features of H-2Kb/cyt c and H-2Db/cyt c complexes responsible for dual recognition. B6.H-4.1c, a representative cloned CTL, was induced by similar concentrations of native peptide added to either H-2Kb- or H-2Db-expressing targets. Furthermore, the dissociation rates for both H-2Kb/cyt c and H-2D b/cyt c were comparable, but the optimal concentration of native peptide significantly increased for both H-2Kb/cyt c and H-2Db/cyt c in peptide competition assays. Based on computer-generated models, we proposed that the Pro 44-Gly45 sequence was critical for B6.H-4.1c recognition and therefore constructed single Ala substitution analogues of cyt c, designated p41--49/44A and p41--49/45A. Although p41--49/44A binds as well to H-2Kb and H-2Db as the native peptide, B6.H-4.1c recognition was ablated. The H-2Kb/p41--49/45A and H-2Db/p41--49/45A complexes were lysed, but required significantly higher peptide concentrations than the native peptide. Molecular models for cyt c, p41--49/44A and p41--49/45A demonstrated that disrupting the Pro44-Gly45 sequence altered peptide configuration and inhibited B6.H-4.1c recognition. Nonspecific immunosuppressive agents are critical in clinical transplantation success, but cause generalized T cell inhibition and leave patients susceptible to elevated rates of infection and malignancy. In part II of this dissertation, we propose that removing allospecific CTLs that selectively expand in vitro will ablate the alloreactive response. We show that five CD8+ Vbeta families in bm19 anti-C57BL/6 cultures proliferate, but cytolytic analysis implicates only Vbeta9+ and Vbeta12 + CTLs as responders against H-2Kb-expressing targets. Removal of both Vbeta9/12+ alloreactive CTLs did not affect the response to Kb-restricted antigens, nor to unrelated H-2d alloantigens. Depletion of both Vbeta9/12 + families significantly prolonged B6 allograft survival in bm19 mice. In addition, bm19 mice mounted a cell-mediated response against L. monocytogenes despite removing Vbeta9/12+ CTLs. These studies demonstrate the synergistic effect of two Vbeta families on alloreactivity and confirm that depletion of allograft-specific Vbeta+ CTLs prolong graft survival without disrupting host immune responsiveness

The Weekly Adjustment Indicators Checklist: An Application in the Child Welfare Field

Research on the effectiveness of various home-based interventions implemented in the 1980s and 1990s indicates that results have been equivocal. Because of the unique and complex behavioral challenges presented by each family and the need for individualized treatments and long-term interventions for these families, group research and evaluation designs are often insufficient in assessing effectiveness of home-based interventions. Alternative evaluation strategies are needed. The purpose of this exploratory study was two-fold: (a) to investigate the applicability and acceptability of the Weekly Adjustment Indicators Checklist (WAIC) in monitoring adult and child behaviors and (b) to monitor, on an on-going basis, the progress of a family referred to an urban family preservation and reunification program. The target family on whom data were collected consisted of a 13-year old girl and her foster parent who was her maternal aunt. The findings of this study indicate that the WAIC is applicable in monitoring the progress of children and adults in care and that it has the endorsement of its user, namely, the direct care provider. Other results of the study, limitations of the study, and future research needs are discussed

Mechanisms and Factors that Influence High Frequency Retroviral Recombination

With constantly changing environmental selection pressures, retroviruses rely upon recombination to reassort polymorphisms in their genomes and increase genetic diversity, which improves the chances for the survival of their population. Recombination occurs during DNA synthesis, whereby reverse transcriptase undergoes template switching events between the two copackaged RNAs, resulting in a viral recombinant with portions of the genetic information from each parental RNA. This review summarizes our current understanding of the factors and mechanisms influencing retroviral recombination, fidelity of the recombination process, and evaluates the subsequent viral diversity and fitness of the progeny recombinant. Specifically, the high mutation rates and high recombination frequencies of HIV-1 will be analyzed for their roles in influencing HIV-1 global diversity, as well as HIV-1 diagnosis, drug treatment, and vaccine development

Lack of Detection of Xenotropic Murine Leukemia Virus-Related Virus in HIV-1 Lymphoma Patients

Xenotropic murine leukemia virus-related virus (XMRV) is a gammaretrovirus reported to be associated with human prostate cancer and chronic fatigue syndrome. Since retroviruses cause various cancers, and XMRV replication might be facilitated by HIV-1 co-infection, we asked whether certain patients with HIV-associated lymphomas are infected with XMRV. Analysis of PMBCs and plasma from 26 patients failed to detect XMRV by PCR, ELISA, or Western blot, suggesting a lack of association between XMRV and AIDS-associated lymphomas

Feasibility of Using a Commercial Fitness Tracker as an Adjunct to Family-Based Weight Management Treatment: Pilot Randomized Trial.

BACKGROUND: Fitness trackers can engage users through automated self-monitoring of physical activity. Studies evaluating the utility of fitness trackers are limited among adolescents, who are often difficult to engage in weight management treatment and are heavy technology users. OBJECTIVE: We conducted a pilot randomized trial to describe the impact of providing adolescents and caregivers with fitness trackers as an adjunct to treatment in a tertiary care weight management clinic on adolescent fitness tracker satisfaction, fitness tracker utilization patterns, and physical activity levels. METHODS: Adolescents were randomized to 1 of 2 groups (adolescent or dyad) at their initial weight management clinic visit. Adolescents received a fitness tracker and counseling around activity data in addition to standard treatment. A caregiver of adolescents in the dyad group also received a fitness tracker. Satisfaction with the fitness tracker, fitness tracker utilization patterns, and physical activity patterns were evaluated over 3 months. RESULTS: A total of 88 adolescents were enrolled, with 69% (61/88) being female, 36% (32/88) black, 23% (20/88) Hispanic, and 63% (55/88) with severe obesity. Most adolescents reported that the fitness tracker was helping them meet their healthy lifestyle goals (69%) and be more motivated to achieve a healthy weight (66%). Despite this, 68% discontinued use of the fitness tracker by the end of the study. There were no significant differences between the adolescent and the dyad group in outcomes, but adolescents in the dyad group were 12.2 times more likely to discontinue using their fitness tracker if their caregiver also discontinued use of their fitness tracker (95% CI 2.4-61.6). Compared with adolescents who discontinued use of the fitness tracker during the study, adolescents who continued to use the fitness tracker recorded a higher number of daily steps in months 2 and 3 of the study (mean 5760 vs 4148 in month 2, P=.005, and mean 5942 vs 3487 in month 3, P=.002). CONCLUSIONS: Despite high levels of satisfaction with the fitness trackers, fitness tracker discontinuation rates were high, especially among adolescents whose caregivers also discontinued use of their fitness tracker. More studies are needed to determine how to sustain the use of fitness trackers among adolescents with obesity and engage caregivers in adolescent weight management interventions

Meaning vs. Power: Are Thick Description and Power Analysis intrinsically at odds? Response to Interpretation, Explanation, and Clifford Geertz

This essay clarifies and defends the methodological multidimensionality and improvisational character of Clifford Geertz’s account of interpretation and explanation. In contrast to accounts of power analysis offered by Michel Foucault and Talal Asad, I argue that Geertz’s work can simultaneously attend to meaning, power, identity, and experience in understanding and assessing religious practices and cultural formations

Obesity hormone leptin: a new target in breast cancer?

Leptin is a multifunctional hormone produced mainly by the adipose tissue and involved in the regulation of food intake and energy balance. In addition, leptin can stimulate mitogenic and angiogenic processes in peripheral organs. Because leptin levels are elevated in obese individuals and excess body weight has been shown to increase breast cancer risk in postmenopausal women, attempts have been made to evaluate whether leptin can promote breast cancer. Data obtained in cell and animal models and analyses of human breast cancer biopsies indeed suggest such an involvement. Furthermore, a recent report clearly shows that targeting leptin signaling may reduce mammary carcinogenesis. Thus, leptin should become a new attractive target in breast cancer

Crystal structure of the catalytic domain of HIV-1 restriction factor APOBEC3G in complex with ssDNA

The human APOBEC3G protein is a cytidine deaminase that generates cytidine to deoxy-uridine mutations in single-stranded DNA (ssDNA), and capable of restricting replication of HIV-1 by generating mutations in viral genome. The mechanism by which APOBEC3G specifically deaminates 5\u27-CC motifs has remained elusive since structural studies have been hampered due to apparently weak ssDNA binding of the catalytic domain of APOBEC3G. We overcame the problem by generating a highly active variant with higher ssDNA affinity. Here, we present the crystal structure of this variant complexed with a ssDNA substrate at 1.86 A resolution. This structure reveals atomic-level interactions by which APOBEC3G recognizes a functionally-relevant 5\u27-TCCCA sequence. This complex also reveals a key role of W211 in substrate recognition, implicating a similar recognition in activation-induced cytidine deaminase (AID) with a conserved tryptophan