Analysis of human immune responses in quasi-experimental settings: tutorial in biostatistics

<p>Abstract</p> <p>Background</p> <p>Human immunology is a growing field of research in which experimental, clinical, and analytical methods of many life science disciplines are utilized. Classic epidemiological study designs, including observational longitudinal birth cohort studies, offer strong potential for gaining new knowledge and insights into immune response to pathogens in humans. However, rigorous discussion of methodological issues related to designs and statistical analysis that are appropriate for longitudinal studies is lacking.</p> <p>Methods</p> <p>In this communication we address key questions of quality and validity of traditional and recently developed statistical tools applied to measures of immune responses. For this purpose we use data on humoral immune response (IR) associated with the first cryptosporidial diarrhea in a birth cohort of children residing in an urban slum in south India. The main objective is to detect the difference and derive inferences for a change in IR measured at two time points, before (pre) and after (post) an event of interest. We illustrate the use and interpretation of analytical and data visualization techniques including generalized linear and additive models, data-driven smoothing, and combinations of box-, scatter-, and needle-plots.</p> <p>Results</p> <p>We provide step-by-step instructions for conducting a thorough and relatively simple analytical investigation, describe the challenges and pitfalls, and offer practical solutions for comprehensive examination of data. We illustrate how the assumption of time irrelevance can be handled in a study with a pre-post design. We demonstrate how one can study the dynamics of IR in humans by considering the timing of response following an event of interest and seasonal fluctuation of exposure by proper alignment of time of measurements. This alignment of calendar time of measurements and a child's age at the event of interest allows us to explore interactions between IR, seasonal exposures and age at first infection.</p> <p>Conclusions</p> <p>The use of traditional statistical techniques to analyze immunological data derived from observational human studies can result in loss of important information. Detailed analysis using well-tailored techniques allows the depiction of new features of immune response to a pathogen in longitudinal studies in humans. The proposed staged approach has prominent implications for future study designs and analyses.</p

Differential onset of apoptosis in avian influenza H5N1 and seasonal H1N1 virus infected human bronchial and alveolar epithelial cells: an in vitro and ex vivo study

INTRODUCTION: Human disease caused by highly pathogenic avian influenza (HPAI) H5N1 virus is associated with fulminant viral pneumonia and mortality rates in excess of 60%.1 Cytokine dysregulation is thought to contribute to its pathogenesis.2,3 We previously found delayed onset of apoptosis in H5N1 infected human macrophages and, therefore, a longer survival time of the target cells for prolonged virus replication and cytokine and chemokine secretion, which may contribute to the pathogenesis of H5N1 disease in humans.4 As bronchial and alveolar epithelial cells are target cells of influenza virus because of their proximal physiological location and interaction with macrophages, we further investigated if the differential onset of apoptosis could be found in influenza H5N1 and seasonal influenza H1N1 infected human respiratory epithelia. We dissected the apoptotic pathways triggered by influenza virus infection …link_to_OA_fulltex

Replication and innate host response of influenza A virus in lung microvascular endothelial cells: new insights into systemic infection and pathogenesis

INTRODUCTION: Though influenza A virus replication kinetics and host responses have been previously studied in umbilical vein endothelial cell or transformed endothelial cell lines, the tropism of influenza A virus including H5N1 and pandemic H1N1pdm for primary human lung microvascular endothelial cell has not been well defined.1 In this study we employed primary human lung microvascular endothelial cells, which are more physiologically relevant for understanding pathogenesis of influenza in the lung as to obtain a better understanding of the links of endothelial cell infection to systematic virus dissemination and multiple organ involvement in severe human influenza …link_to_OA_fulltex

Tropism and innate host response of the 2009 pandemic H1N1 influenza virus compared with related swine influenza viruses and reassortants in ex vivo and in vitro cultures of the human respiratory tract and conjunctiva

BACKGROUND: Pandemic influenza H1N1 (H1N1pdm) virus of swine-origin causes mild disease, but occasionally is associated with acute respiratory distress syndrome and death.1,2 It is important to understand the pathogenesis of this new disease. Previously we showed a comparable virus tropism and host innate immune responses between H1N1pdm and seasonal H1N1 influenza virus in the human respiratory tract,3 however H1N1pdm virus differed from seasonal H1N1 influenza virus in its ability to replicate in human conjunctiva, suggesting subtle differences in receptor-binding profile and highlighting the potential role of the conjunctiva as an additional route of infection. We now compare the tropism and host responses elicited by pandemic H1N1 with that of related swine influenza viruses and a pandemic-swine reassortant virus in ex vivo and in vitro cultures of the human respiratory tract and conjunctiva. We have used recombinant virus to investigate the role of the hemagglutinin (HA) and neuraminidase (NA) of H1N1pdm virus in its conjunctival tropism. These findings are relevant for understanding transmission and therapy …link_to_OA_fulltex

Study design and baseline results of an open-label cluster randomized community-intervention trial to assess the effectiveness of a modified mass deworming program in reducing hookworm infection in a tribal population in southern India

Introduction: Hookworm infection is a leading cause of iron deficiency anemia and malnutrition in resource-poor settings. Periodic mass deworming with anthelminthic drugs remains the cornerstone of hookworm control efforts worldwide. Reinfection following treatment occurs, reflecting the human host's inability to acquire immunity following exposure to an untreated reservoir of infection. This cluster randomized trial will evaluate the effectiveness of a modified, population-based, mass deworming strategy in reducing hookworm infection in an endemic southern Indian population. Methods: Forty five tribal villages were randomized into three groups: one received annual treatment; the second received two rounds of treatment at 1-month intervals; and the third received four rounds of treatment e two rounds 1 month apart at the beginning, followed by another two after 6 months. Stool samples collected through cross-sectional parasitological surveys pre- and post-intervention, and at 3- monthly intervals for a period of 1 year were tested for presence of hookworm ova. Long-term effectiveness of treatment will be assessed through another survey conducted 2 years after the last treatment cycle. Results: From a population of 11,857 individuals, 8681 (73.2%) were found to be eligible and consented to participate, out-migration being the primary reason for non-participation. Baseline stool samples were obtained from 2082 participants, with 18.5% having hookworm infection, although majority were low intensity infections (<2000 eggs per gram of feces). Discussion: This study will help identify the optimal mass deworming strategy that can achieve the greatest impact in the shortest period of time, particularly in settings where long-term program sustainability is a challeng