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. 2022 Apr 30;14(5):942.
doi: 10.3390/v14050942.

Genomic and In Vitro Phenotypic Comparisons of Epidemic and Non-Epidemic Getah Virus Strains

Noor-Adila Mohamed-Romai-Noor  1   2 , Sing-Sin Sam  1 , Boon-Teong Teoh  1 , Zur-Raiha Hamim  1   2 , Sazaly AbuBakar  1
Affiliations

Genomic and In Vitro Phenotypic Comparisons of Epidemic and Non-Epidemic Getah Virus Strains

Noor-Adila Mohamed-Romai-Noor et al. Viruses. .

Abstract

Getah virus is an emerging mosquito-borne animal pathogen. Four phylogenetic groups of GETV, Group I (GI), GII, GIII and GIV, were identified. However, only the GETV GIII was associated with disease epidemics suggesting possible virulence difference in this virus group. Here, we compared the genetic and in vitro phenotypic characteristics between the epidemic and non-epidemic GETV. Our complete coding genome sequence analyses revealed several amino acid substitutions unique to the GETV GIII and GIV groups, which were found mainly in the hypervariable domain of nsP3 and E2 proteins. Replication kinetics of the epidemic (GIII MI-110 and GIII 14-I-605) and non-epidemic GETV strains (prototype GI MM2021 and GIV B254) were compared in mammalian Vero cells and mosquito C6/36 and U4.4 cells. In all cells used, both epidemic GETV GIII MI-110 and GIII 14-I-605 strains showed replication rates and mean maximum titers at least 2.7-fold and 2.3-fold higher than those of GIV B254, respectively (Bonferroni posttest, p < 0.01). In Vero cells, the epidemic GETV strains caused more pronounced cytopathic effects in comparison to the GIV B254. Our findings suggest that higher virus replication competency that produces higher virus titers during infection may be the main determinant of virulence and epidemic potential of GETV.

Keywords: Getah virus; alphavirus; arbovirus; emerging; infectious diseases; tropical.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Comparison of (A) non-structural and (B) structural polyprotein amino acids between different groups of GETV. The dots represent similar amino acids in comparison to the GII GETV Sagiyama virus. The shaded areas represent the amino acid substitutions exclusive to the GETV GIII and GIV (in the box). The GETV GIII with homologous sequences are clustered together and indicated as GIIIa, GIIIb, GIIIc, GIIId, and GIIIe.
Figure 2
Figure 2
Plaque morphology of various GETV strains in Vero cells. Plaques shown were at 72 hpi; (A) GI GETV MM2021, (B) GIV GETV B254, (C) GIII GETV MI-110, (D) GIII GETV 14-I-605 (5× magnification).
Figure 3
Figure 3
Replication kinetics of various GETV strains in Vero, C6/36 and U4.4 cells. Cells were infected with GETV at MOI = 0.1. Extracellular virus RNA levels at 0, 8, 24, 48, 72, and 96 hpi were quantitated using qRT-PCR. (A) Growth curves of different GETV strains in respective cell lines. (B) Bar graphs represent the growth of GETV in the cells. Data plots show the mean viral RNA copies and standard deviation (SD) of three independent replicates. Error bars indicate SD. Asterisks indicate statistical significance (* p < 0.05, ** p < 0.01, *** p < 0.001) as determined by Bonferroni test.
Figure 4
Figure 4
Cytopathic effects of GETV infection in Vero, C6/36, and U4.4 cells. Cells were infected with various strains of GETV at MOI of 0.1 and cytopathic effects (CPE) was observed at 48 hpi (200× magnification). Relatively more apparent CPEs were observed in the GETV-infected Vero and C6/36 cells, where the cells were shrunk, rounded, and refractile-appearing as compared to the larger and dark-appearing cells in the mock infections. No apparent CPE was observed in the GETV-infected U4.4 cells.
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