Recombinant Tula hantavirus shows reduced fitness but is able to survive in the presence of a parental virus: analysis of consecutive passages in a cell culture

Plyusnina, Angelina; Plyusnin, Alexander

Hantaviruses (genus Hantavirus, family Bunyaviridae) have a tripartite genome comprising the L segment encoding the RNA-polymerase, the M segment encoding two external glycoproteins, and the S segment encoding the nucleocapsid (N) protein [12] . Hantaviruses are maintained in nature in persistently infected rodents, each hantavirus type being predominantly associated with a distinct rodent host species [13] . When transmitted to humans, some hantaviruses cause hemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome, whereas other hantaviruses are apathogenic [14, 15] . Persistent infection in natural hosts allows for the simultaneous presence of more than one genetically distinct hantavirus variant in the same rodent. This may result in hantavirus genome reassortment [16, 17] or recombination, as proposed in the above-mentioned study of Sibold et al [10] who showed a mosaic-like structure of the S RNA segment and the N protein of Tula hantavirus (TULV). Most recently, we have shown transfection-mediated rescue of TULV with recombinant S segment, in which nt 1-332 originate from the cell culture isolate Moravia/Ma5302V/ 94 (or TULV02, for short) [18] , nt 369-1853 originate from the strain Tula/Ma23/87 [19] , and nt 333-368, that are identical in both variants, can be of either origin. Both M and L segments of the recombinant virus (recTULV) originate from TULV02 [11] . RecTULV was functionally competent but less competitive than TULV02. One reason for the observed lower fitness of the recTULV might be that it was generated in the presence of the wt variant, with which it has to compete, and thus not given enough time to to establish a well balanced, mature quasi-species population. We, therefore, decided to compare fitness of TULV02 with that of recTULV that underwent several passages in cell culture.