Genotype-specific neutralization determinants in envelope protein: implications for the improvement of Japanese encephalitis vaccine

Abstract

Japanese encephalitis remains the leading cause of viral encephalitis in children in Asia and is expanding its geographical range to larger areas in Asia and Australasia. Five genotypes of Japanese encephalitis virus (JEV) co-circulate in the geographically affected areas. In particular, the emergence of genotype I (GI) JEV has displaced genotype III (GIII) as the dominant circulating genotype in many Asian regions. However, all approved vaccine products are derived from GIII strains. In the present study, bioinformatic analysis revealed that GI and GIII JEV strains shared two distinct amino acid residues within the envelope (E) protein (E222 and E327). By using reverse genetics approaches, A222S and S327T mutations were demonstrated to decrease live-attenuated vaccine (LAV) SA14-14-2-induced neutralizing antibodies in humans, without altering viral replication. A222S or S327T mutations were then rationally engineered into the infectious clone of SA14-14-2, and the resulting mutant strains retained the same genetic stability and attenuation characteristics as the parent strain. More importantly, immunization of mice with LAV-A222S or LAV-S327T elicited increased neutralizing antibodies against GI strains. Together, these results demonstrated that E222 and E327 are potential genotype-related neutralization determinants and are critical in determining the protective efficacy of live Japanese encephalitis vaccine SA14-14-2 against circulating GI strains. Our findings will aid in the rational design of the next generation of Japanese encephalitis LAVs capable of providing broad protection against all JEV strains belonging to different genotypes.

Genotype I of Japanese Encephalitis Virus Virus-like Particles Elicit Sterilizing Immunity against Genotype I and III Viral Challenge in Swine

“…E amino acid sequences are different among five genotypes of JEV. Amino acid substitutions at positions 222 and 327 in the E protein of GI virus might be critically related to the immunogenicity of vaccine 53 . The neutralizing antibody titer was lower against GI virus than GIII virus: 5.9- to 10.2-fold lower titers among vaccinees receiving GIII-inactivated vaccines 22 , 23 , 2.1-fold lower titers among vaccinees receiving GIII live-attenuated vaccine 19 , and 14.6-fold lower titers among swine receiving GIII live-attenuated vaccine 20 .…”

Experimental Evaluation of the Role of Ecologically-Relevant Hosts and Vectors in Japanese Encephalitis Virus Genotype Displacement

“…At present, there is no data on cross-genotype protection information for G-V. Although currently available vaccines based on G-III protect against G-I infection, the protection may be sub-optimal [7,20,21,22,23], suggesting that displacement of G-III by G-I may adversely affect current vaccine effectiveness. The occurrence of genomic variation between genotypes has been thought to enable one genotype of JEV to become more fit than the other one in the ecological niches in which they circulate [9,13,24,25,26,27].…”

Single-Round Infectious Particle Antiviral Screening Assays for the Japanese Encephalitis Virus

“…The signal peptide of prM/M protein is sliced by a cell protease during maturation [5]. E protein (E) is responsible for virus attachment and membrane fusion and is also the crucial antigen to inducing neutralizing antibodies [6,7]. Non-structural proteins NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5, are responsible for viral replication [1,2,3].…”