Reassortment events in the evolution of hantaviruses

Boris Klempa

doi:10.1007/s11262-018-1590-z

Abstract

Hantaviruses (order Bunyavirales, family Hantaviridae), known as important zoonotic human pathogens, possess the capacity to exchange genome segments via genetic reassortment due to their tri-segmented genome. Although not as frequent as in the arthropod-borne bunyaviruses, reports indicating reassortment events in the evolution of hantaviruses have been recently accumulating. The intra- and inter-lineage reassortment between closely related variants has been repeatedly reported for several hantaviruses including the rodent-borne human pathogens such as Sin Nombre virus, Puumala virus, Dobrava-Belgrade virus, or Hantaan virus as well as for the more recently recognized shrew-borne hantaviruses, Imjin and Seewis. Reassortment between more distantly related viruses was rarely found but seems to play a beneficial role in the process of crossing the host species barriers. Besides the findings based on phylogenetic studies of naturally occurring strains, hantavirus reassortants were generated also in in vitro studies. Interestingly, only reassortants with exchanged M segments could be generated suggesting that a high degree of genetic compatibility is required for the S and L segments while the exchange of M segment is better tolerated or is particularly beneficial. Altogether, the numerous reports on hantavirus reassortment, summarized in this review, clearly demonstrate that reassortment events play a significant role in hantavirus evolution and contributed to the currently recognized hantavirus diversity.

Highlights

First reports that genome segment exchange, in other words genetic reassortment events, could have been occurring in the evolution of hantaviruses are rather old and emerged soon after the discovery of hantavirus cardiopulmonary syndrome-causing Sin Nombre virus (SNV) in the United States [1, 2]
In the S segment analyses, Jabora virus (JABV) clusters only with Ape Aime-Itapúa virus (AAIV) and occupies the most ancestral position within the South American hantaviruses [65]. These findings indicate that reassortment events involving distantly related hantaviruses are directly connected with or play a role in the processes of host-switching
Diploid viruses were observed in all studies on in vitro generated reassortants mentioned above. These findings indicate that the hantavirus assembly process is not tightly controlled and more than three genome segments can be packed into the viral particle

Summary

Introduction

First reports that genome segment exchange, in other words genetic reassortment events, could have been occurring in the evolution of hantaviruses are rather old and emerged soon after the discovery of hantavirus cardiopulmonary syndrome-causing Sin Nombre virus (SNV) in the United States [1, 2]. Recent phylogenetic analyses including the more recently discovered shrew-, mole-, and bat-borne hantaviruses revealed a complex evolutionary history where virus-host co-divergence and cross-species transmission and ancient reassortment events played a role. Another well-documented example within the Bunyamwera serogroup viruses is the hemorrhagic fever causing Ngari virus (and its isolate Garissa virus) which is a reassortant containing S and L segments of Bunyamwera virus and M segment of Batai virus This is interesting because Ngari virus can be associated with large outbreaks of severe illness in East Africa while its parents are reported to cause rather mild symptoms in humans but more severe symptoms including abortions and teratogenic effects in livestock [37–40].

Conclusions

Findings

Compliance with ethical standards