CTLA-4 blockade following relapse of malignancy after allogeneic stem cell transplantation is associated with T cell activation but not with increased levels of T regulatory cells.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a key negative regulator of T cell activation and proliferation. Ipilimumab is a human monoclonal antibody that specifically blocks the binding of CTLA-4 to its ligand. To test the hypothesis that blockade of CTLA-4 by ipilimumab could augment graft-versus-malignancy (GVM) effects without a significant impact on graft-versus-host disease (GVHD), we conducted a phase I clinical trial of ipilimumab infusion in patients with relapsed malignancy following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, we report the analysis of peripheral blood T lymphocyte reconstitution, T regulatory cell (Treg) expression, and T cell activation markers after a single dose of ipilimumab in 29 patients. Peripheral blood samples were collected from all patients before and after ipilimumab infusion. Lymphocyte immunophenotyes, including levels of CD4(+)CD25(high) cells and T cell activation markers, were analyzed in all cases. Levels of CD4(+)CD25(high)Foxp3(+) cells and intracellular CTLA-4 in CD4(+) T cells also were evaluated in the last 11 cases. We found lower baseline levels of CD4(+) and CD45RO(+) T cells in patients compared with normal controls. More than 50% of the patients had abnormally low lymphocyte counts (CD4 or/and CD8 T cells), and some had no circulating B lymphocytes. The percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells were significantly higher in patients before ipilimumab infusion than in healthy donors. Twenty of 29 patients exhibited an elevated level of CD4(+)CD25(low) activated T cells at baseline, compared with only 3 of 26 healthy donors. Both CD4(+) and CD8(+) T lymphocyte counts were significantly increased after ipilimumab infusion. There was no consistent change in absolute lymphocyte count or in the number of T cells expressing the activation marker CD69. However, increases in CD4(+)CD25(low) T cells were seen in 20 of 29 patients and increases in CD4(+)HLA-DR(+) T cells were seen in the last 10 patients in the first 60 days after ipilimumab infusion. Although the percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells decreased significantly during the observation period, the absolute cell counts did not change. Intracellular CTLA-4 expression in CD4(+)CD25(lo/-) T cells increased significantly after ipilimumab infusion. We conclude that CTLA-4 blockade by a single infusion of ipilimumab increased CD4(+) and CD4(+)HLA-DR(+) T lymphocyte counts and intracellular CTLA-4 expression at the highest dose level. There was no significant change in Treg cell numbers after ipilimumab infusion. These data demonstrate that significant changes in T cell populations occur on exposure to a single dose of ipilimumab. Further studies with multiple doses are needed to explore this phenomenon further and to correlate changes in lymphocyte subpopulations with clinical events.

Descriptive analysis of immunization policy decision making in the Americas / Análisis descriptivo de la toma de decisión sobre políticas de vacunación en las Américas

OBJECTIVES: Reducing and eliminating vaccine-preventable diseases requires evidence-based and informed policy decision making. Critical to determining the functionality of the decision-making process for introduction of a new vaccine is understanding the role of the national immunization technical advisory group (ITAG) in each country. The aim of this study is to document the current situation of national level immunization policy decision making for use in the Pan American Health Organization (PAHO) ProVac Initiative. METHODS: A structured 66-variable questionnaire developed by the World Health Organization (WHO) in collaboration with the University of Ottawa was distributed to all WHO regions; it was composed of dichotomous, multiple-choice, and open-ended questions. Questionnaires were e-mailed or faxed to the six WHO regional offices and the offices distributed them to all member states. This paper analyzes surveys from the Americas as part of PAHO's ProVac Initiative. RESULTS: Twenty-nine countries of the Americas answered the survey. They conveyed that immunization policy making needed to be improved and further supported by organizations such as PAHO. Areas of improvement ranged from organization and technical support to strengthening capacity and infrastructure to improved coordination among stakeholders. This survey also highlighted a variety of ITAG processes that need further investigation. CONCLUSION: This survey supports the efforts of PAHO's ProVac Initiative to disseminate knowledge and best practices for an immunization policy decision-making framework through the development of clear definitions and guidelines. By highlighting each problem noted in this study, ProVac will assist countries in Latin America and the Caribbean to build national capacity for making evidence-based decisions about introduction of new vaccines.

OBJETIVOS: Para reducir y eliminar las enfermedades prevenibles por vacunación se requiere tomar decisiones basadas en datos científicos y una política informada. Con el fin de determinar la funcionalidad del proceso de toma de decisiones para introducir una nueva vacuna es vital comprender el papel de los grupos técnicos asesores nacionales sobre vacunación (GTAN) de cada país. En este trabajo se documenta la situación actual de la toma de decisión sobre políticas de vacunación a nivel nacional como insumo de la Iniciativa ProVac de la Organización Panamericana de la Salud (OPS). MÉTODOS: Se distribuyó a todas las regiones de la Organización Mundial de la Salud (OMS) un cuestionario estructurado con 66 variables, desarrollado por la OMS en colaboración con la Universidad de Ottawa, Canadá. El cuestionario contenía preguntas abiertas, dicotómicas y de selección múltiple y se envió por correo electrónico o fax a las seis oficinas regionales de la OMS y estas lo distribuyeron a todos los estados miembros. En este manuscrito se analizan las respuestas procedentes de las Américas, como parte de la Iniciativa ProVac de la OPS. RESULTADOS: Respondieron la encuesta 29 países de las Américas. Todos coincidieron en que la formulación de políticas de vacunación debe mejorar y se necesita más apoyo de organizaciones como la OPS. Las áreas que requieren mejoras van desde la organización y el apoyo técnico hasta el fortalecimiento de la capacidad y la infraestructura, y el perfeccionamiento de la coordinación entre los diferentes actores. También se destacan algunos procesos de los GTAN que requieren mayor investigación. CONCLUSIÓN: Esta encuesta apoya los esfuerzos de la iniciativa ProVac de la OPS para diseminar el conocimiento y las mejores prácticas para elaborar un marco de trabajo para la toma de decisiones sobre políticas de vacunación mediante el desarrollo de definiciones y directivas claras. Al poner de manifiesto cada problema observado ...

Descriptive analysis of immunization policy decision making in the Americas.

OBJECTIVES: Reducing and eliminating vaccine-preventable diseases requires evidence-based and informed policy decision making. Critical to determining the functionality of the decision-making process for introduction of a new vaccine is understanding the role of the national immunization technical advisory group (ITAG) in each country. The aim of this study is to document the current situation of national level immunization policy decision making for use in the Pan American Health Organization (PAHO) ProVac Initiative. METHODS: A structured 66-variable questionnaire developed by the World Health Organization (WHO) in collaboration with the University of Ottawa was distributed to all WHO regions; it was composed of dichotomous, multiple-choice, and open-ended questions. Questionnaires were e-mailed or faxed to the six WHO regional offices and the offices distributed them to all member states. This paper analyzes surveys from the Americas as part of PAHO's ProVac Initiative. RESULTS: Twenty-nine countries of the Americas answered the survey. They conveyed that immunization policy making needed to be improved and further supported by organizations such as PAHO. Areas of improvement ranged from organization and technical support to strengthening capacity and infrastructure to improved coordination among stakeholders. This survey also highlighted a variety of ITAG processes that need further investigation. CONCLUSION: This survey supports the efforts of PAHO's ProVac Initiative to disseminate knowledge and best practices for an immunization policy decision-making framework through the development of clear definitions and guidelines. By highlighting each problem noted in this study, ProVac will assist countries in Latin America and the Caribbean to build national capacity for making evidence-based decisions about introduction of new vaccines.