Full-genome characterization of the RIVM-HAV16-090-like hepatitis A virus strains recovered from Japanese men who have sex with men, with sporadic acute hepatitis A.

AIM: The major transmission mode of hepatitis A virus (HAV) is the fecal-oral route via contaminated foods in Japan. In contrast, HAV infection is well documented as a sexually transmitted disease in Western countries. The present study was conducted to determine the full-genome sequence of HAV and trace the transmission route of HAV in Japanese men who have sex with men (MSM).

METHODS: In 2018, we encountered three Japanese MSM with acute hepatitis A co-infected with human immunodeficiency virus (HIV) for 4-12 years. Serum samples obtained from these patients were used for HAV full-genome analyses.

RESULTS: Isolated HAV strains were segregated into subgenotype IA. The 3 HAV strains shared 100% identity within the 481-nucleotide partial sequence. The entire nucleotide sequence demonstrated that the 3 strains were 99.97% similar to each other with only 2 nucleotide substitutions. At the amino acid level, the three strains differed from each other by only one or two amino acids. All three strains obtained in the present study were >99.6% identical to the 66 reported strains isolated from Taiwan and European countries during 2015-2017. In addition, these 66 strains include the RIVM-HAV16-090 (EuroPride) strain, which has been involved in HAV outbreaks among MSM worldwide.

CONCLUSIONS: We determined for the first time the full-genome sequence of HAV isolated from Japanese MSM with acute hepatitis A and found that the strains were identical to those from MSM worldwide. Thus, these HAV strains were imported to Japan from foreign countries through MSM.