Sergey P. Morzunov

Hantaviruses: Molecular Biology, Evolution and Pathogenesis

Hantaviruses are tri-segmented negative sense single stranded RNA viruses that belong to the family Bunyaviridae. In nature, hantaviruses are exclusively maintained in the populations of their specific rodent hosts. In their natural host species, hantaviruses usually develop a persistent infection with prolonged virus shedding in excreta. Humans become infected by inhaling virus contaminated aerosol. Unlike asymptomatic infection in rodents, hantaviruses cause two acute febrile diseases in humans: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). The mortality rate varies from 0.1% to 40% depending on the virus involved. Hantaviruses are distributed world wide, with over 150,000 HFRS and HPS cases being registered annually. In this review we summarize current knowledge on hantavirus molecular biology, epidemiology, genetic diversity and co-evolution with rodent hosts. In addition, special attention was given in this review to describing clinical manifestation of HFRS and HPS, and advances in our current understanding of the host immune response, treatment, and prevention.

Generation of a Recombinant Cytomegalovirus for Expression of a Hantavirus Glycoprotein

ABSTRACT A cytomegalovirus (CMV) was isolated from its natural host, Peromyscus maniculatus, and was designated Peromyscus CMV (PCMV). A recombinant PCMV was constructed that contained Sin Nombre virus glycoprotein G1 (SNV-G1) fused in frame to the enhanced green fluorescent protein (EGFP) gene inserted into a site homologous to the human CMV UL33 (P33) gene. The recombinant CMV was used for expression and immunization of deer mice against SNV-G1. The results of the study indicate that P. maniculatus could be infected with as few as 10 virus particles of recombinant virus. Challenge of P. maniculatus with either recombinant or wild-type PCMV produced no overt pathology in infected animals. P. maniculatus immunized with recombinant virus developed an antibody response to SNV and EGFP. When rechallenged with recombinant virus, animals exhibited an anamnestic response against SNV. Interestingly, a preexisting immune response against PCMV did not prevent reinfection with recombinant PCMV.

Prevalence of Hantavirus in Four Species of Neotoma from Arizona and Utah

Sin Nombre virus (SNV), a hantavirus, can cause severe respiratory illness and death in humans. The primary carrier is the deer mouse, Peromyscus maniculatus , but other species of rodents may be infected with the virus. We screened four species of woodrats ( Neotoma ) for hantavirus using both enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) tests. Woodrats were collected from a variety of habitats in Arizona and Utah. Only Neotoma lepida tested serologically positive in an ELISA assay for hantavirus and also contained SNV RNA. Moreover, across three distinct populations of N. lepida , individuals that tested serum positive were restricted to one population near Jericho, Utah. The prevalence of hantavirus in this population was 27% (4 of 15).

Genetic analysis of the M RNA segment of Crimean-Congo hemorrhagic fever virus strains involved in the recent outbreaks in Russia.

Summary.Crimean-Congo hemorrhagic fever (CCHF) is a severe zoonosis with a high fatality rate. In Russia, local CCHF outbreaks have occurred in the Stavropol Territory, and the Volgograd and Astrakhan Regions during 2000 and 2001. Seven strains of CCHF virus (CCHFV) were isolated from infected patients and collected ticks. Two fragments of the CCHF virus M genome segment were PCR amplified and their nucleotide sequences were determined. All these virus strains appear to be closely related (up to 5.8% nucleotide sequence differences) and form a distinct clade on the CCHFV phylogenetic tree. Within this clade, CCHFV strains from Stavropol and Astrakhan cluster together, whereas those from Volgograd form a separate subgroup.

Hantaviral Proteins: Structure, Functions, and Role in Hantavirus Infection

Hantaviruses are the members of the family Bunyaviridae that are naturally maintained in the populations of small mammals, mostly rodents. Most of these viruses can easily infect humans through contact with aerosols or dust generated by contaminated animal waste products. Depending on the particular Hantavirus involved, human infection could result in either hemorrhagic fever with renal syndrome or in Hantavirus cardiopulmonary syndrome. In the past few years, clinical cases of the Hantavirus caused diseases have been on the rise. Understanding structure of the Hantavirus genome and the functions of the key viral proteins are critical for the therapeutic agents’ research. This paper gives a brief overview of the current knowledge on the structure and properties of the Hantavirus nucleoprotein and the glycoproteins.

Multiplex Analysis of Serum Cytokines in Humans with Hantavirus Pulmonary Syndrome

Hantavirus pulmonary syndrome (HPS) is an acute zoonotic disease transmitted primarily through inhalation of virus-contaminated aerosols. Hantavirus infection of endothelial cells leads to increased vascular permeability without a visible cytopathic effect. For this reason, it has been suggested that the pathogenesis of HPS is indirect with immune responses, such as cytokine production, playing a dominant role. In order to investigate their potential contribution to HPS pathogenesis, we analyzed the serum of hantavirus-infected subjects and healthy controls for 68 different cytokines, chemokines, angiogenic, and growth factors. Our analysis identified differential expression of cytokines that promote tissue migration of mononuclear cells including T lymphocytes, natural killer cells, and dendritic cells. Additionally, we observed a significant upregulation of cytokines known to regulate leukocyte migration and subsequent repair of lung tissue, as well as cytokines known to increase endothelial monolayer permeability and facilitate leukocyte transendothelial migration. Conversely, we observed a downregulation of cytokines associated with platelet numbers and function, consistent with the thrombocytopenia observed in subjects with HPS. This study corroborates clinical findings and extends our current knowledge regarding immunological and laboratory findings in subjects with HPS.

Andes-virus-induced cytokine storm is partially suppressed by ribavirin.

BACKGROUND Microbe-induced over-activation of cytokines, especially tumour necrosis factor (TNF)-α, is key to the pathogenesis of hantavirus infection leading to severe inflammation with high mortality rate. Although ribavirin showed promise in inhibiting viral replication in vitro, its clinical efficacy remains controversial. METHODS Various concentrations of ribavirin were used to determine its effect on cytokine activation in our infectious model system. RESULTS Ribavirin decreased the virus load and dose-dependently inhibited the accumulation of RANTES messenger RNA in Andes-virus (ANDV)-infected human endothelial cells, but failed to suppress TNF-α-induced activation of RANTES and interleukin-6 in ANDV-inoculated cultures. This report also shows, for the first time, that the deleterious over-stimulation by TNF-α is mediated by nuclear factor-κB, and describes the effect of ribavirin on cytokine production following ANDV infection. CONCLUSIONS Although highly effective in preventing ANDV replication and suppressing activation of select inflammatory mediators, the therapeutic efficacy of ribavirin is limited due to its inability to fully inhibit cytokine outburst triggered by hantavirus infection.

Human dendritic cells transfected with a human papilloma virus-18 construct display decreased mobility and upregulated cytokine production

The marked depletion of dendritic cells (DCs) in skin cancers, as well as preneoplastic and neoplastic cervical epithelium, suggests a central role for DCs in productive human papillomavirus (HPV) infection and cancer promotion. It has been suggested that HPV may facilitate tumor development by reducing DC density, contributing to a decrease in local immune surveillance. In this study, we have examined the response of human DCs transfected with a construct containing the HPV18 genome and their subsequent expression of papilloma virus proteins. Transfected cells expressed the L1 major capsid protein and upregulated E6 and E7 oncoprotein transcripts as detected by RT-PCR. Transfection of DCs also resulted in a significant increase in cytokine production. Finally, we observed that HPV18 transfection decreased the migratory activity of DCs. Our data indicate that HPV transfection of DCs leads to changes in migratory activity and cytokine production, which potentially can suppress or delay immune responses to viral antigens. Additionally, changes in cytokine production by HPV-transformed human fibroblasts and human cervical epithelial cells revealed that the migratory and antigen-presenting functions of DCs may be impaired by the suppressive effects of cytokines produced by HPV-infected epithelial and stromal cells.

Serum Cytokine Profiles Differentiating Hemorrhagic Fever with Renal Syndrome and Hantavirus Pulmonary Syndrome

Hantavirus infection is an acute zoonosis that clinically manifests in two primary forms, hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). HFRS is endemic in Europe and Russia, where the mild form of the disease is prevalent in the Tatarstan region. HPS is endemic in Argentina, as well as other countries of North and South American. HFRS and HPS are usually acquired via the upper respiratory tract by inhalation of virus-contaminated aerosol. Although the pathogenesis of HFRS and HPS remains largely unknown, postmortem tissue studies have identified endothelial cells as the primary target of infection. Importantly, cell damage due to virus replication, or subsequent tissue repair, has not been documented. Since no single factor has been identified that explains the complexity of HFRS or HPS pathogenesis, it has been suggested that a cytokine storm may play a crucial role in the manifestation of both diseases. In order to identify potential serological markers that distinguish HFRS and HPS, serum samples collected during early and late phases of the disease were analyzed for 48 analytes using multiplex magnetic bead-based assays. Overall, serum cytokine profiles associated with HPS revealed a more pro-inflammatory milieu as compared to HFRS. Furthermore, HPS was strictly characterized by the upregulation of cytokine levels, in contrast to HFRS where cases were distinguished by a dichotomy in serum cytokine levels. The severe form of hantavirus zoonosis, HPS, was characterized by the upregulation of a higher number of cytokines than HFRS (40 vs 21). In general, our analysis indicates that, although HPS and HFRS share many characteristic features, there are distinct cytokine profiles for these diseases. These profiles suggest a strong activation of an innate immune and inflammatory responses are associated with HPS, relative to HFRS, as well as a robust activation of Th1-type immune responses. Finally, the results of our analysis suggest that serum cytokines profiles of HPS and HFRS cases are consistent with the presence of extracellular matrix degradation, increased mononuclear leukocyte proliferation, and transendothelial migration.

Epidemiological dynamics of nephropathia epidemica in the Republic of Tatarstan, Russia, during the period of 1997–2013

This report summarizes epidemiological data on nephropathia epidemica (NE) in the Republic of Tatarstan, Russia. NE cases identified in the period 1997-2013 were investigated in parallel with the hantavirus antigen prevalence in small rodents in the study area. A total of 13 930 NE cases were documented in all but one district of Tatarstan, with most cases located in the central and southeastern districts. The NE annual incidence rate exhibited a cyclical pattern, with the highest numbers of cases being registered once in every 3-5 years. The numbers of NE cases rose gradually from July to November, with the highest morbidity in adult males. The highest annual disease incidence rate, 64·4 cases/100 000 population, was observed in 1997, with a total of 2431 NE cases registered. NE cases were mostly associated with visiting forests and agricultural activities. The analysis revealed that the bank vole Myodes glareolus not only comprises the majority of the small rodent communities in the region, but also consistently displays the highest hantavirus prevalence compared to other small rodent species.