Philosophiae Doctor - PhD / Sequencing an HIV quasispecies with next generation sequencing technologies yields a dataset with significant amplification bias and errors resulting from both the PCR and sequencing steps. Both the amplification bias and sequencing error can be reduced by labelling each cDNA (generated during the reverse transcription of the viral RNA to DNA prior to PCR) with a random sequence tag called a Primer ID (PID). Processing PID data requires additional computational steps, presenting a barrier to the uptake of this method. MotifBinner is an R package designed to handle PID data with a focus on resolving potential problems in the dataset. MotifBinner groups sequences into bins by their PID tags, identifies and removes false unique bins, produced from sequencing errors in the PID tags, as well as removing outlier sequences from within a bin. MotifBinner produces a consensus sequence for each bin, as well as a detailed report for the dataset, detailing the number of sequences per bin, the number of outlying sequences per bin, rates of chimerism, the number of degenerate letters in the final consensus sequences and the most divergent consensus sequences (potential contaminants). We characterized the ability of the PID approach to reduce the effect of sequencing error, to detect minority variants in viral quasispecies and to reduce the rates of PCR induced recombination. We produced reference samples with known variants at known frequencies to study the effectiveness of increasing PCR elongation time, decreasing the number of PCR cycles, and sample partitioning, by means of dPCR (droplet PCR), on PCR induced recombination. After sequencing these artificial samples with the PID approach, each consensus sequence was compared to the known variants. There are complex relationships between the sample preparation protocol and the characteristics of the resulting dataset. We produce a set of recommendations that can be used to inform sample preparation that is the most useful the particular study. The AMP trial infuses HIV-negative patients with the VRC01 antibody and monitors for HIV infections. Accurately timing the infection event and reconstructing the founder viruses of these infections are critical for relating infection risk to antibody titer and homology between the founder virus and antibody binding sites. Dr. Paul Edlefsen at the Fred Hutch Cancer Research Institute developed a pipeline that performs infection timing and founder reconstruction. Here, we document a portion of the pipeline, produce detailed tests for that portion of the pipeline and investigate the robustness of some of the tools used in the pipeline to violations of their assumptions.

The ability to obtain deoxyribonucleic acid (DNA) profiles is generally considered a powerful tool when examining evidence associated with a crime scene. However, variability in peak heights associated with short tandem repeats (STR) signal complicates DNA interpretation; particularly, low-template complex mixtures, which are regularly encountered during evidentiary analysis. In order to elucidate the sources that cause peak height variability a dynamic model, which simulates; 1) the serial dilution process; 2) polymerase chain reaction (PCR); and 3) capillary electrophoresis (CE) was built and used to generate simulated DNA evidentiary profiles. In order to develop the dynamic model, PCR efficiencies were characterized. This was accomplished using empirical quantitative polymerase chain reaction (qPCR) data. Specifically, the ratios of fluorescent readings of two consecutive cycles were evaluated. It was observed that the efficiency fluctuated at early cycles; stabilized during the middle cycles; and plateaued during later cycles. The relationship between the change in efficiency and the concentration of amplicons was modeled as an exponential function. Subsequently, this exponential relationship was incorporated into the dynamic model as a part of the PCR module. Using the dynamic laboratory model, the effect of serially diluting a concentrated DNA extract to a low-template concentration was assessed in an effort to determine whether serially diluted samples are a good representation of evidence samples which contain low copy number of cells. To accomplish this, peak height variances and the frequency of drop-out between serially and non-serially diluted samples were compared. The results showed that diluting the sample had a substantial influence on allelic drop-out. However, the distributions of the observed peak heights did not consistently change; though, changes in peak height distributions became more pronounced with samples at lower targets. The peak height equivalency (PHE) was also used to aid in the determination of the effect of serial dilutions on reproducibility. There was not a major change in PHE between serially and non-serially diluted samples.

Influenza is a viral infection that affects global health and economy with its endemic and sometimes pandemic spread. Rapid detection of Influenza viruses enables antiviral use and can bring financial savings. It is also essential for the global surveillance of prevalent Influenza strains. RT-PCR is considered the most specific and sensitive method for detection of Influenza, but Influenza mutates at a high rate and it is therefore crucial that RT-PCR methods are updated regularly. In 2014, Cepheid released their Xpert Flu/RSV XC assay, which can detect Influenza A and B and RSV by multiplex RT-PCR in approximately one hour. The aim of this study was to evaluate this assay at Laboratoriemedicin Västernorrland by using the laboratory’s previous PCR assay for detection of Influenza viruses as reference method. Real-time RT-PCR was used to compare Xpert Flu/RSV XC to the reference method. A dilution series was performed to estimate the methods’ PCR efficiencies and precision was calculated from quadruplicates of a positive control sample. Clinical specimens (n=42) were used to evaluate the diagnostic sensitivity and specificity of Xpert Flu/RSV XC. Objective statistical analysis of PCR data was performed and discussed. The Xpert Flu/RSV XC was equivalent to the reference method and demonstrated high diagnostic sensitivity and specificity. Estimated PCR efficiencies were however low. With the introduction of Xpert Flu/RSV XC to the laboratory follows many potential benefits, primarily in form of a simplified pre analytical procedure and a shortened analysis time. The Xpert Flu/RSV XC assay enables fast diagnosis of Influenza infection.

Real-time PCR method is a type of PCR which allows continual monitoring of DNA amplification during every cycle of its process. It is mostly used for gene expression analysis. Based on the results of previous experiments, we decided to test out the effect of anticoagulants EDTA, heparin, sodium citrate and CPDA on the expression of selected genes of the immunological spectrum and further, to test how the time period between drawing the blood and processing of blood sample influences mRNA levels of selected genes that are determined by changes in gene expression and/or mRNA degradation. To quantify mRNA of the studied genes, we isolated total RNA from the peripheral blood leucocytes and transcribed it into cDNA by using the reverse transcription PCR. This cDNA served as a template for the real-time PCR. To examine the changes of the expression caused by the effect of each particular anticoagulants, peripheral blood derived from 10 volunteers was used (each donor's blood was taken into 3 vacuum tubes with EDTA, heparin and sodium citrate anticoagulant agents). Next to that, we obtained 10 buffy coat samples in transfusion blood bags with CPDA anticoagulant agent. Compared to blood cells influenced by one of the three anticoagulant agents present in vacuum tubes, cells from transfusion bags affected...