Genetic analyses reveal differences in the VP7 and VP4 antigenic epitopes between human rotaviruses circulating in Belgium and rotaviruses in Rotarix and RotaTeq

Abstract

Two live-attenuated rotavirus group A (RVA) vaccines, Rotarix (G1P[8]) and RotaTeq (G1-G4, P[8]), have been successfully introduced in many countries worldwide, including Belgium. The parental RVA strains used to generate the vaccines were isolated more than 20 years ago in France (G4 parental strain in RotaTeq) and the United States (all other parental strains). At present, little is known about the relationship between currently circulating human RVAs and the vaccine strains. In this study, we determined sequences for the VP7 and VP4 outer capsid proteins of representative G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], and G12P[8] RVAs circulating in Belgium during 2007 to 2009. The analyses showed that multiple amino acid differences existed between the VP7 and VP4 antigenic epitopes of the vaccine viruses and the Belgian isolates, regardless of their G and P genotypes. However, the highest variability was observed among the circulating G1P[8] RVA strains and the G1 and P[8] components of both RVA vaccines. In particular, RVA strains of the P[8] lineage 4 (OP354-like) showed a significant number of amino acid differences with the P[8] VP4 of both vaccines. In addition, the circulating Belgian G3 RVA strains were found to possibly possess an extra N-linked glycosylation site compared to the G3 RVA vaccine strain of RotaTeq. These results indicate that the antigenic epitopes of RVA strains contained in the vaccines differ substantially from those of the currently circulating RVA strains in Belgium. Over time, these differences might result in selection for strains that escape the RVA neutralizing-antibody pressure induced by vaccines.

Fig 1

Distance matrix for VP7 and VP4 based on amino acid identities. Intragenotype similarities with Rotarix are colored in green. Intragenotype similarities with RotaTeq are colored in blue.

Fig 2

Phylogenetic analysis of the VP7 (A) and VP4 (B) proteins of circulating Belgian RVA strains and Rotarix and RotaTeq vaccine strains. Neighbor-joining trees were constructed using on the complete amino acid sequences of VP7 and VP4. Pigeon RVA strain PO-13 was used as the outgroup. Belgian strains are indicated with a red triangle. Rotarix and RotaTeq sequences are indicated with green and blue circles, respectively. Bootstrap values (500 replicates) of ≥70% are shown.

Fig 3

(A) Alignment of antigenic residues in VP7 between the strains contained in Rotarix and RotaTeq and strains circulating in Belgium. Antigenic residues are divided in three epitopes (7-1a, 7-1b, and 7-2). Amino acids that differ between Rotarix and RotaTeq are indicated in boldface. Blue colored residues are residues that are different from Rotarix, and green colored residues are different from the most similar genotype in RotaTeq. Residues colored in blue/green are different from both Rotarix and RotaTeq, with exception of G9 and G12 strains in which green residues were different from all VP7 genotypes contained in RotaTeq. Amino acid changes that have been shown to escape neutralization with monoclonal antibodies (37) are indicated with a red triangle. (B) Surface representation of the VP7 trimer (PDB 3FMG). Antigenic epitopes are colored in red (7-1a), salmon (7-1b), and purple (7-2). Surface-exposed residues that differ between circulating strains in Belgium and the strains contained in Rotarix or RotaTeq are shown in cyan.

Fig 4

(A) Alignment of antigenic residues in VP4 between the strains contained in Rotarix and RotaTeq and strains circulating in Belgium. Antigenic residues are divided in three antigenic epitopes in VP8* and five antigenic epitopes in VP5*. Residues are color coded similar as described for Fig. 3. Amino acid changes that have been shown to escape neutralization with monoclonal antibodies (17) are indicated with a red triangle. (B) Surface representation of the VP8* core (PDB 1KQR). The left images show VP8* from the front. The right images are rotated 180° compared to the left images and show VP8* from the back. Antigenic epitopes are colored in red (8-1), pink (8-2), purple (8-3), and green (8-4). Surface-exposed residues that differ between circulating strains in Belgium and the strains contained in Rotarix and RotaTeq are shown in cyan. The N-acetylneuraminic (sialic) acid binding site (17) is indicating by the yellow stick model of a sialoside.