Molecular epidemiology and divergence of HIV type 1 protease codon 35 inserted strains among treatment-naive patients in Hong Kong

This study reported the prevalence and pattern of viral replication-associated HIV-1 protease codon 35 amino acid insertions among treatment-naive patients in Hong Kong. The transmission and divergence date of these inserted strains was also investigated. The pol gene of 264 local HIV-1 isolates was sequenced and phylogenetic analysis was performed. The transmission history of protease codon 35-inserted HIV-1 strains in Hong Kong was estimated by the Bayesian coalescent method. This insertion was detected in 12 (4.55%) among 264 treatment-naive subtype B HIV-1 patients in Hong Kong, which was 20-times higher than the prevalence in the western countries. Among these strains, eight carried a glutamic acid (GAA) insertion (E35E_E), two carried an aspartic acid (GAC) insertion (E35E_D), and two carried a glycine (GGA) insertion (E35E_G). E35E_D and E35E_E insertions were the first to be reported. All the 12 inserted sequences clustered in the same lineage of the phylogenetic tree, indicating the possibility of transmission of this insertion. Epidemiological investigation revealed the major route of infection for this inserted strain in Hong Kong was associated mainly among homosexual Chinese males. The evolutionary rate of these inserted strains was similar to other subtype B HIV-1 strains. Through coalescent-based analysis, the divergence date of the protease codon 35-inserted strains in Hong Kong was 1995. Our findings demonstrate the epidemic pathways of viral fitness-related HIV-1 protease codon 35-inserted isolates in Hong Kong. The effect of these novel insertions on viral fitness and drug susceptibility requires further investigation.