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A J Rossini

Publications and source records attributed to A J Rossini.

8 recordsLinked to original sources
PubMed2006

Statistical evaluation of HIV vaccines in early clinical trials.

The HIV pandemic is a pressing threat to global public health; HIV vaccine development is critical. Clinical evaluation of HIV vaccine candidates differs from the standard therapeutics trial framework primarily due to the fact that healthy individuals are studied. We present an early stage evaluation program developed for the HIV Vaccine Trials Network (HVTN) motivated by characteristics unique to the vaccine setting. The program consists of 3 prototypical stages (Phase I, Ib, II) that provide a unified yet flexible approach to the safety and immunogenicity evaluation of diverse vaccine regimens. The goal of these early trials is to narrow the number of candidate vaccines to the most promising candidates worthy of further study in efficacy trials.

AIDS Vaccines↗
PubMed2005

Two-sample tests for comparing intra-individual genetic sequence diversity between populations.

Consider a study of two groups of individuals infected with a population of a genetically related heterogeneous mixture of viruses, and multiple viral sequences are sampled from each person. Based on estimates of genetic distances between pairs of aligned viral sequences within individuals, we develop four new tests to compare intra-individual genetic sequence diversity between the two groups. This problem is complicated by two levels of dependency in the data structure: (i) Within an individual, any pairwise distances that share a common sequence are positively correlated; and (ii) for any two pairings of individuals which share a person, the two differences in intra-individual distances between the paired individuals are positively correlated. The first proposed test is based on the difference in mean intra-individual pairwise distances pooled over all individuals in each group, standardized by a variance estimate that corrects for the correlation structure using U-statistic theory. The second procedure is a nonparametric rank-based analog of the first test, and the third test contrasts the set of subject-specific average intra-individual pairwise distances between the groups. These tests are very easy to use and solve correlation problem (i). The fourth procedure is based on a linear combination of all possible U-statistics calculated on independent, identically distributed sequence subdatasets, over the two levels (i) and (ii) of dependencies in the data, and is more complicated than the other tests but can be more powerful. Although the proposed methods are empirical and do not fully utilize knowledge from population genetics, the tests reflect biology through the evolutionary models used to derive the pairwise sequence distances. The new tests are evaluated theoretically and in a simulation study, and are applied to a dataset of 200 HIV sequences sampled from 21 children.

Base Sequence↗
PubMed2003

Expression array annotation using the BioMediator biological data integration system and the BioConductor analytic platform.

This paper presents the implementation of a model for expression array annotation (EAA) using the BioMediator biological data integration system along with BioConductor, an analytic tools platform. The model presented addresses the need for annotation sources identified during BioConductor inverted exclamation mark s development. Annotation provides us with well-curated genomic background knowledge for expression array analysis and interpretation. Annotation requests are constructed and posted to the query interface of the EAA package (the EAA model implemented as a component of BioConductor). The software enumerates all possible annotation paths for queries. These are then transformed to PQL queries and processed by BioMediator. Annotation entities returned from the EAA package answer the annotation request.

Computational Biology↗
PubMed1996

Checking adequacy of the semiparametric location shift model with censored data.

The location shift model is commonly used to quantify the difference between groups in a two-arm study. Nonparametric inference procedures for the location shift parameter with censored observations have recently been extensively studied. However, the validity of these procedures depends heavily on the model assumption. In this article, a class of graphical and numerical methods are proposed for checking the adequacy of the location shift model. Our graphical procedures are much less subjective than the eye-ball method based on the standard Q-Q plot. The proposed methods are illustrated with real-life examples.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[Role of Mycoplasma pneumoniae in the etiology of acute respiratory infections in Ribeirao Preto, Sao Paulo, Brazil].

Mycoplasma pneumoniae isolation was attempted in respiratory fluids from 64 patients with respiratory infection Complement fixation test (CF) and counterimmunoelectrophoresis (CIE) were used for Mycoplasma antibody detection using the patient sera. Mycoplasma pneumoniae was not isolated. Serologic diagnosis were positives in 3.1% (2/64) by CF test and 1.6% (1/64) by CIE. Serologic tests done in 200 health controls showed 4% (8/200) positives by CIE and 1% (2/200) by CF. The results showed differences in sensitivity among the serologic tests. CF seems to be more indicated for Mycoplasma infection diagnosis while, CIE could be used for Mycoplasmas serosurveys. The prevalence of Mycoplasma pneumoniae infections was low (3.1%) in the 64 patients during our study period.

Acute Disease↗