Analyzing Codon Usage Patterns in Human Papillomavirus Type 18

Human papillomavirus type 18, a high-risk oncogenic strain, significantly contributes to cervical and anogenital/oropharyngeal cancers. This investigation examines the codon usage patterns of Human papillomavirus type 18 to understand its evolutionary adaptation and therapeutic implications. Analysis of 178 viral genomes assessed nucleotide composition, relative synonymous codon usage, dinucleotide distribution, and codon adaptation indices. Findings demonstrated a strong bias toward codons terminating with adenine/uracil (A/U), with third-position guanine-cytosine content below 34% and limited codon bias (effective number of codons = 49.34). Dinucleotide profiling revealed suppressed ApA, CpG, and UpC frequencies alongside elevated CpA and UpG levels, potentially reflecting CpG motif avoidance for immune evasion. Neutrality analysis, parity rule 2 plots and effective number of codons-plots demonstrated predominant natural selection (86.61% influence) over mutational pressure in shaping codon usage. The Relative Codon Deoptimization Index (approximately 2) indicated balanced viral adaptation to human translation systems, enabling efficient replication while competing for host resources. This systematic characterization of Human papillomavirus type 18 codon usage patterns elucidates host-pathogen coevolution mechanisms critical for optimizing vaccine design and targeted antiviral interventions against this oncogenic pathogen.