Generation of Variability in Chrysodeixis includens Nucleopolyhedrovirus (ChinNPV): The Role of a Single Variant.

Eduardo Aguirre,Trevor Williams,Inés Beperet,Primitivo Caballero

doi:10.3390/v13101895

Eduardo Aguirre, Trevor Williams + Show 2 more

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https://doi.org/10.3390/v13101895

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Journal: Viruses	Publication Date: Sep 22, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Universidad Publica de Navarra, Instituto de Ecología

Abstract

The mechanisms generating variability in viruses are diverse. Variability allows baculoviruses to evolve with their host and with changes in their environment. We examined the role of one genetic variant of Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) and its contribution to the variability of the virus under laboratory conditions. A mixture of natural isolates (ChinNPV-Mex1) contained two genetic variants that dominated over other variants in individual larvae that consumed high (ChinNPV-K) and low (ChinNPV-E) concentrations of inoculum. Studies on the ChinNPV-K variant indicated that it was capable of generating novel variation in a concentration-dependent manner. In cell culture, cells inoculated with high concentrations of ChinNPV-K produced OBs with the ChinNPV-K REN profile, whereas a high diversity of ChinNPV variants was recovered following plaque purification of low concentrations of ChinNPV-K virion inoculum. Interestingly, the ChinNPV-K variant could not be recovered from plaques derived from low concentration inocula originating from budded virions or occlusion-derived virions of ChinNPV-K. Genome sequencing revealed marked differences between ChinNPV-K and ChinNPV-E, with high variation in the ChinNPV-K genome, mostly due to single nucleotide polymorphisms. We conclude that ChinNPV-K is an unstable genetic variant that is responsible for generating much of the detected variability in the natural ChinNPV isolates used in this study.

Highlights

(108 occlusion bodies (OBs)/mL) resulted in 100% mortality and 99 out of 100 recovered larvae showed the Chrysodeixis includens nucleopolyhedrovirus (ChinNPV)-K variant Restriction Endonuclease Analysis (REN) profile, whereas the single remaining insect had the dominant profile of the ChinNPV-E variant (Figure 1A)
The remaining 18 insects (56%) presented one of six different variant profiles in different frequencies (Figure 5B). These results suggest that: (i) pooling the OBs of multiple variants may result in a variant K-type consensus REN profile and (ii) that the pooled OBs behaved to pure ChinNPV-K variant inoculum in that the ChinNPV-K variant profile predominated in most larvae that died from high concentration pooled inoculum, whereas considerable diversity was observed in larvae that died from low concentration pooled inoculum
The unstable ChinNPV-K variant was capable of generating a range of genotypes that appeared on multiple occasions and at varying prevalence in insects inoculated with low concentrations of ChinNPV-K OBs

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Baculoviruses are double-stranded DNA viruses, with a large circular genome ranging from 80 to 180 Kb [1]. Due to the negative correlation between mutation rate and genome length, baculoviruses are supposed to be less prone to mutation than most other DNA viruses [2]. Natural isolates of baculoviruses are known to comprise mixtures of genotypes [3], which suggests that phenomena such as recombination, mutation, and transposition take place frequently during baculovirus replication [4,5,6,7,8]. Single nucleotide polymorphisms (SNPs) can be generated during the replication of viral

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