Immunogenicity and Safety of a Quadrivalent Meningococcal Tetanus Toxoid-Conjugate Vaccine (MenACYW-TT) in Meningococcal Vaccine-Naïve Participants across a Broad Age Range (2-55 Years) in Japan: a Phase III Randomized Study.

MenACYW-TT is a quadrivalent meningococcal tetanus toxoid-conjugate vaccine designed to prevent invasive meningococcal disease. The primary objective of this study was to demonstrate non-inferiority of the vaccine seroresponse to a single dose of MenACYW-TT compared with MCV4-DT, a licensed meningococcal quadrivalent diphtheria-conjugate vaccine. This Phase III double-blind, multicenter trial was conducted in meningococcal vaccine-naïve individuals aged 2-55 years in Japan (NCT04368429; jRCT2080225192). Participants were randomized 1:1 to receive either MenACYW-TT (n = 180) or MCV4-DT (n = 180). Functional antibodies against meningococcal serogroups A, C, W, and Y were measured using a serum bactericidal antibody assay with human complement (hSBA) at baseline (D0) and 30 days after vaccination (D30). Seroresponse was defined as a post-vaccination titer ≥1:16 in participants with a baseline titer <1:8; or a ≥4-fold increase in titer in participants with a baseline titer ≥1:8. Safety data were collected for 30 days. Non-inferiority of the seroresponse to MenACYW-TT vs. MCV4-DT was demonstrated on D30 for each serogroup tested (A: 85.6% vs. 65.4%; C: 96.6% vs. 62.6%; W: 87.4% vs. 49.2%; Y: 97.7% vs. 63.5%). MenACYW-TT was well tolerated with no safety concerns identified. A single dose of MenACYW-TT was well tolerated, with a non-inferior seroresponse compared with MCV4-DT. MenACYW-TT could thus be used as an alternative vaccine in meningococcal vaccine-naïve individuals.

Characterization of Meq proteins from field isolates of Marek's disease virus in Japan.

Serotype 1 strains of Marek's disease virus (MDV-1) cause malignant lymphomas in chickens (Marek's disease; MD). Although MD has been controlled by vaccination, field isolates of MDV-1 have tended to increase in virulence and cause MD even in vaccinated chickens. Meq, a putative MDV-1 oncoprotein, resembles the Jun/Fos family of basic leucine zipper (bZIP) transcription factors and can regulate the expression of viral and cellular genes as a homodimer or as a heterodimer with a variety of bZIP family proteins. Sequencing analysis of some of the viral genes of various MDV-1 strains revealed a distinct diversity of and point mutations in Meq, which may contribute to changes in the transcriptional activities of Meq and, consequently, to increases in MDV-1 oncogenicity. However, few reports have characterized MDV-1 strains isolated in Japan. In this study, we established the amino acid sequences of MDV-1 field isolates from Japan in order to determine whether they display a distinct diversity of and point mutations in Meq. In addition, we analyzed the transactivation activities of the Meq proteins in order to evaluate whether the observed mutations affect their functions. Japanese MDV-1 isolates displayed the distinct mutations in basic region 2 (BR2) and proline-rich repeats (PRRs) of the Meq proteins as well as some unique mutations. Reporter assays revealed that the amino acid substitutions in BR2 and the PRRs affected the Meq transactivation activity. These results suggest that the distinct mutations are also present in the Meq proteins of MDV-1 isolates from Japan and affect their transactivation activities.

Analysis of transcriptional activities of the Meq proteins present in highly virulent Marek's disease virus strains, RB1B and Md5.

Marek's disease virus (MDV) is an oncogenic herpesvirus that causes malignant lymphomas in chickens. Recent field isolates of MDV have tended to exhibit increasing virulence, and MDV strains are currently classified into four categories based on their relative virulence. Meq, a putative MDV oncoprotein, resembles the Jun/Fos family of basic leucine zipper (bZIP) transcription factors and can regulate the expression of viral and cellular genes as a homodimer or as a heterodimer with a variety of bZIP family proteins. MDV isolates display distinct diversity and point mutations in Meq, which may contribute to changes in the transcriptional activities of Meq and subsequently, to observed increases in MDV oncogenicity. In this study, we introduced mutations into the meq gene and used dual luciferase reporter assays to analyze the transcriptional activities of the resulting Meq proteins to determine whether distinct mutations in Meq could be responsible for differences in transcriptional activity among MDV strains. A proline-to-alanine substitution at position 217, the second position of one of the proline direct repeats in the transactivation domain, enhanced the transactivation activity of Meq. In addition, we found that two substitutions at positions 283 and 320 affected transactivation activity. These results suggest that the distinct diversity of and point mutations in the Meq proteins are responsible for differences in transactivation activity among MDV strains.