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This study analyzes the base pair differences between subjects with significantly different T-cell rates. The research aims to identify specific nucleotide differences that contribute to the increase or decline of CD4 T-cells.
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Analyzing Base Pair Differences Between Subjects with Significantly Different T-Cell Rate Alex George J’aime Moehlman Amanda Wavrin Loyola Marymount University March 2, 2010
Outline • Introduction • Materials/Methods • Results • Discussion • References
Introduction to HIV-1 • HIV-1 relation to CD4 T-Cells. • Significance of the Env gene • gp 120 • Studies suggest adaptation leads to pathogenicity of HIV-1.
Our Proposed Question • Is there a specific base pair difference between the subjects with a high rate of CD4 T-Cell decline versus the subjects with an increase in CD4 T-Cells?
1st Hypothesis • H1: There will be a specific nucleotide difference between each group that is responsible for CD4 T-Cell increase or decline. • Two Groups: • Group 1 (Decline): Subjects 10, 11, 15 • Group 2 (Increase): Subjects 6, 12 13
Methods for Hypothesis 1 • We selected all clones from all subjects from Visit 4. • Unrooted Tree of all Six Subjects. • Multiple Sequence Alignment within groups on Biology Workbench. • Compared similarities within Group 1 to similarities within Group 2.
Unrooted Tree for S6,10,11,12,13,15 S6 S12 S10 S11 S15 S13
Example Comparison between S10 and S6 S10,V4-1 S6, V4-1
Results • The similar sequences were identical for both groups. • Our hypothesis is rejected: • H0: There was no constant DNA sequence in Group 1 that differed from sequences in Group 2. • These results led us to formulate a second hypothesis.
2nd Hypothesis • H2: The range of difference in Group 1 will be larger than the range of difference for Group 2. • Two Groups: • Group 1 (Decline): Subjects 10, 11, 15 • Group 2 (Increase): Subjects 6, 12, 13
Methods for Hypothesis 2 • Observed differences from original Unrooted Tree. • Use Clustdist tool in Biology Workbench to generate distance matrices for each group. • Multiplied Min. and Max. by 285 to calculate raw number of differences.
Unrooted Tree for S6,10,11,12,13,15 S6 S12 S10 S11 S15 S13
Table Comparing Minimum and Maximum Difference between Groups 1 and 2 Data table shows no convincing difference in range between the two groups.
Results • The range difference of Group 1 was larger than Group 2, but is not convincing. • In the V3 region, the similarities within Group 1 were identical to the similarities within Group 2.
Discussion • The V3 region does not have the most adaptive events. • The base pair differences could lie in a different region of the gene. • Future Research: • Analyze other regions of the gene in a similar manner to find differences in base pairs.
References • Williamson, Scott. 2003. Adaptation in the env Gene of HIV-1 and Evolutionary Theories of Disease Progression. Molecular Biology Evolution. 20(8):1318–1325 • Markham RB, Wang WC, Weisstein AE, Wang Z, Munoz A, Templeton A, Margolick J, Vlahov D, Quinn T, Farzadegan H, and Yu XF. Patterns of HIV-1 evolution in individuals with differing rates of CD4 T cell decline. Proc Natl Acad Sci U S A 1998 Oct 13; 95(21) 12568-73. pmid:9770526.