Serological methods for detection of infection with shrew-borne hantaviruses: Thottapalayam, Seewis, Altai, and Asama viruses

Development of a seroepidemiological tool for bat-borne and shrew-borne hantaviruses and its application using samples from Zambia

BACKGROUND

Rodent-borne orthohantaviruses are the causative agents of hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. Apart from the classic rodent-borne hantaviruses, numerous species of hantaviruses have been identified in shrews and bats; however, their antigenicity and pathogenicity are unknown. This study focused on developing a serological method to detect antibodies against bat- and shrew-borne hantaviruses.

METHODOLOGY/PRINCIPAL FINDINGS

Five bat-borne (Brno, Dakrong, Quezon, Robina, and Xuan Song) and 6 shrew-borne (Asama, Altai, Cao Bang, Nova, Seewis, and Thottapalayam) viruses were selected based on the phylogenetic differences in their N proteins. The recombinant N (rN) proteins of these viruses were expressed as antigens in Vero E6 and 293T cell lines using the pCAGGS/MCS vector. Antisera against the Nus-tagged rN fusion proteins of these viruses (mouse anti-Brno, Dakrong, Quezon, Robina, Xuan Song, Asama, Cao Bang, and Nova, while rabbit anti-Altai, Seewis and Thottapalayam) were also generated. Antigenic cross-reactivity was examined in antisera and rN-expressing Vero E6 cells. The rN proteins of almost all the tested viruses, except for the Quezon and Robina viruses, showed independent antigenicity. For serological screening of bat samples, 5 rNs of the bat-borne viruses were expressed together in a single transfection protocol. Similarly, 6 rNs of shrew-borne viruses were expressed. Reactivities of the mixed antigen system were also examined across the singly transfected Vero cell lines to ensure that all antigens were expressed. Using these antigens, bat serum samples collected from Zambia were screened using the indirect immunofluorescence antibody test (IFAT). Selected positive samples were individually tested for the respective antigens by IFAT and western blot assays using rN-expressing 293T cell lysates. Of the 1,764 bat serum samples tested, 11.4% and 17.4% were positive for bat and shrew mixed antigens, respectively. These samples showed positive reactions to the Brno, Dakrong, Quezon, Xuan Son, Robina, Asama, Altai, Cao Bang, or Thottapalayam virus antigens.

CONCLUSIONS/SIGNIFICANCE

These observations suggest that the mixed-antigen screening system is useful for serological screening For Orthohantavirus infections and that bats in Zambia are likely exposed to not only bat-borne hantaviruses but also to shrew-borne hantaviruses.

[Shrew-borne hantaviruses (Hantaviridae: Orthohantavirus) in the Far East of Russia]

INTRODUCTION

Insectivores are newly recognized hantaviral reservoir worldwide. Four distinct shrew-borne hantaviruses (family Hantaviridae) have been identified in two regions located in southern and northern part of the Russian Far East, two genetic variants of Seewis virus (SWSV), Lena River virus (LENV), Kenkeme virus (KKMV) and Yakeshi virus (YKSV). Here, we describe geographic distribution of shrew-borne hantaviruses in southern part of the Russian Far East: Jewish Autonomous region, Khabarovsk Krai, Primorsky Krai and Sakhalin region.

MATERIALS AND METHODS

Lung samples from shrews of genus Sorex, captured in the four regions of Far Eastern Russia, were examined for hantavirus RNA using reverse transcription polymerase chain reaction (RT-PCR). Phylogenetic analysis of the partial nucleotide sequences of viral genome was conducted using MEGA X software.

RESULTS

New genetic variant of YKSV was identified in new reservoir host, long-clawed shrew (S. ungiuculatus) from Sakhalin Island. Genetic variant of SWSV, ARTV-Sc, has been found to circulate among S. caecutiens on the seacoast of Khabarovsk and Primorsky Krai. KKMV virus and second genetic variant of SWSV, ARTV-St, were found in S. roboratus and S. tundrensis, respectively from Jewish Autonomous region.

CONCLUSION

Sorex-borne hantaviruses were found in all studied regions of Far Eastern Russia. Our results demonstrated co-evolution of SWSV, KKMV, and YKSV viruses throughout the geographic distribution of its hosts.

The Serological Cross-Detection of Bat-Borne Hantaviruses: A Valid Strategy or Taking Chances?

Bats are hosts of a range of viruses, and their great diversity and unique characteristics that distinguish them from all other mammals have been related to the maintenance, evolution, and dissemination of these pathogens. Recently, very divergent hantaviruses have been discovered in distinct species of bats worldwide, but their association with human disease remains unclear. Considering the low success rates of detecting hantavirus RNA in bat tissues and that to date no hantaviruses have been isolated from bat samples, immunodiagnostic tools could be very helpful to understand pathogenesis, epidemiology, and geographic range of bat-borne hantaviruses. In this sense, we aimed to identify in silico immunogenic B-cell epitopes present on bat-borne hantaviruses nucleoprotein (NP) and verify if they are conserved among them and other selected members of Mammantavirinae, using a combination of (the three most used) different prediction algorithms, ELLIPRO, Discotope 2.0, and PEPITO server. To support our data, we in silico modeled 3D structures of NPs from representative members of bat-borne hantaviruses, using comparative and ab initio methods due to the absence of crystallographic structures of studied proteins or similar models in the Protein Data Bank. Our analysis demonstrated the antigenic complexity of the bat-borne hantaviruses group, showing a low sequence conservation of epitopes among members of its own group and a minor conservation degree in comparison to Orthohantavirus, with a recognized importance to public health. Our data suggest that the use of recombinant rodent-borne hantavirus NPs to cross-detect antibodies against bat- or shrew-borne viruses could underestimate the real impact of this virus in nature.

[Hantavirus infection as a risk for chronic kidney disease of unknown etiology (CKDu) in Sri Lanka]

Chronic kidney disease of unknown etiology (CKDu) has emerged in endemic areas of Sri Lanka since the 1990s. The disease is a chronic but fatal disease. Until now, heavy metals and agrochemicals have been suspected as the cause of CKDu, but it has been still unknown. Recently, we have found a high seroprevalence to hantavirus in CKDu patients and reported that hantavirus infection is a risk of CKDu. Hantaviruses are rodent-borne zoonotic viruses. Here, I would like to introduce a story of the research from sero-epidemiology to the search for host animals.