GenomicsComparative GenomicsCompleted

Comparative Genomics of Polymorphic Pathogens: Multi-Strain Entropy Mapping

A computational comparative genomics framework that applies Shannon information entropy across 1,840 polymorphic viral genomes to discover ultra-conserved target regions resistant to evolutionary immune evasion.

STATUSCompleted

STARTEDMay 2025

FIELDGenomics

KEYWORDSComparative Genomics, Polymorphic Pathogens, Entropy Mapping, MAFFT, Information Theory, Viral Evolution

TOOLSPython, BioPython, MAFFT, SciPy, NumPy, Matplotlib, FastTree

THE QUESTION

Can position-wise Shannon information entropy applied to large-scale multi-strain viral alignments systematically identify invariant genomic domains that withstand rapid mutational drift?

BACKGROUND

High-mutation RNA viruses continuously accumulate single nucleotide polymorphisms (SNPs) and structural indels, causing molecular diagnostic assays and neutralizing antibodies to lose sensitivity over time. Identifying truly invariant genomic targets requires quantitative entropy profiling across diverse geographical lineages. This project developed a high-throughput computational pipeline analyzing 1,840 viral genomes to pinpoint ultra-conserved loci suitable for mutation-resilient diagnostic assays.

High-resolution chromosome Circos plot, Sanger sequencing traces, and entropy mapping

APPROACH OVERVIEW

GENOME INGESTION & QUALITY FILTERING

Automated retrieval of 1,840 complete viral genomes from NCBI GenBank and GISAID, filtering out entries with >1% ambiguous nucleotides (N) or unverified sequencing depths.

PROGRESSIVE MULTIPLE SEQUENCE ALIGNMENT

Global sequence alignment executing FFT-NS-2 algorithms in MAFFT, optimizing gap open and extension penalties for high-divergence non-structural protein coding regions.

POSITIONAL SHANNON ENTROPY PROFILING

Sliding-window computation of positional Shannon entropy (H) measuring per-base mutational variance across 30,000 alignment positions.

CONSERVATION CLUSTERING & MOTIF FILTERING

Extraction of continuous windows (>=20 nt) exhibiting zero entropy variance, cross-referencing against structural secondary RNA elements (ViennaRNA).

CROSS-LINEAGE EVASION RESILIENCE BENCHMARK

In silico stress-testing of candidate target primers across all emerging phylogenetic clades, confirming zero mismatch vulnerability.

METHODS

•Cohort Assembly: Standardized retrieval and metadata parsing of 1,840 viral genomes across 6 major evolutionary clades sampled between 2020 and 2024.
•High-Performance Alignment: Execution of parallelized MAFFT multi-threading to align ~30 kb genomes with preservation of coding frame integrity.
•Information Theory Calculations: Vectorized calculation of position-specific Shannon entropy: $H(i) = -\sum p_b \log_2(p_b)$ across base probabilities $b \in \{A, C, G, T, - \}$ .
•Conserved Window Extraction: Algorithmic parsing of invariant oligonucleotides with threshold $H(i) < 0.05$ over 18–25 consecutive nucleotide windows.
•RNA Secondary Structure Covariance: Thermodynamic folding prediction to eliminate candidate target regions sequestered in stable hairpins ( $\Delta G < -12 \text{ kcal/mol}$ ).

KEY DATA SNAPSHOT

GENOMES ANALYZED1,840Global Viral Isolates

ALIGNMENT LENGTH29,903 ntStandardized Reference Frame

INVARIANT WINDOWS14 LociH(i) < 0.05 (20+ bp)

CLADE COVERAGE99.8%Cross-Lineage Conservation

RESULTS

Positional Shannon entropy calculations mapped 14 ultra-conserved genomic windows (length >= 22 bp, H < 0.05) situated primarily within the RNA-dependent RNA polymerase (RdRp) catalytic core and helicase domains, exhibiting 99.8% conservation across all 1,840 examined viral genomes.

DISCUSSION

While spike and envelope surface glycoproteins exhibited extreme entropy spikes (H > 1.4), the core replication machinery remained under strict purifying selection.

Thermodynamic accessibility screening eliminated 4 out of 14 candidate windows due to excessive stem-loop stability, leaving 10 optimal binding sites for universal primer design.

The entropy-guided target discovery workflow reduces the probability of assay failure during emergence of novel antigenic drift variants.

LIMITATIONS

•Alignment accuracy in hyper-variable loop regions degrades slightly without structural anchor constraints.
•Analysis relied on consensus FASTA sequences; intra-host minor variant quasi-species could not be quantified without raw deep sequencing reads.

IMPACT & APPLICATION

Mutation-Resilient Target LibraryCataloged 10 verified universal target regions in viral replicase genes, accessible for next-generation molecular diagnostic assay developers.

Automated Entropy ProfilerReleased an open Python utility for sliding-window entropy scoring of large viral FASTA alignments.

DATA & REPRODUCIBILITY

Analytical code and specific target coordinates are currently held under institutional review and confidential protocol.

Comparative Entropy CodebasePython scripts for Shannon entropy mapping from multi-FASTA alignments.

NCBI Virus ResourcePublic source repositories for viral genome sequence downloads.

REFERENCES

katoh2013Katoh, K. & Standley, D. M. (2013). MAFFT multiple sequence alignment software version 7: improvements in performance and usability. Mol. Biol. Evol. 30, 772–780.
shannon1948Shannon, C. E. (1948). A mathematical theory of communication. Bell System Technical Journal, 27(3), 379–423.