The N-terminus of the Montano virus nucleocapsid protein possesses broadly cross-reactive conformation-dependent epitopes conserved in rodent-borne hantaviruses

The hantavirus nucleocapsid (N) protein is an important immunogen that stimulates a strong and cross-reactive immune response in humans and rodents. A large proportion of the response to N protein has been found to target its N-terminus. However, the exact nature of this bias towards the N-terminus is not yet fully understood. We characterized six monoclonal antibodies (mAbs) against the N protein of Montano virus (MTNV), a Mexican hantavirus. Five of these mAbs recognized eight American hantaviruses and six European and Asian hantaviruses, but not the Soricomorpha-borne Thottapalayam hantavirus. The N protein-reactive binding regions of the five mAbs were mapped to discontinuous epitopes within the N-terminal 13-51 amino acid residues, while a single serotype-specific mAb was mapped to residues 1-25 and 49-75. Our findings suggest that discontinuous epitopes at the N-terminus are conserved, at least in rodent-borne hantaviruses, and that they contribute considerably to N protein cross-reactivity.     

Ecology of hantaviruses in Mexico: Genetic identification of rodent host species and spillover infection

In our recent epidemiological survey conducted in Mexico for hantavirus infection, we identified three distinct viruses circulating in Mexican wild rodents, namely Montano virus (MTNV), Huitzilac virus (HUIV), and Carrizal virus (CARV). To gain a detailed understanding of hantavirus epidemiology and its associated hosts, 410 rodents were captured at eight collecting points in Morelos and Guerrero, Mexico, and examined for hantavirus seroprevalence, the presence of viral RNA, and rodent host species identification using cytochrome b gene sequences. Of the 32 species captured, seven species were positive for hantavirus: Peromyscus beatae (31/127; 24.4%), Reithrodontomys sumichrasti (6/15; 40%), Reithrodontomys megalotis (2/25; 8%), Peromyscus aztecus evides (1/1; 100%), Peromyscus megalops (1/41; 2.4%), Megadontomys thomasi (1/9; 11.1%), and Neotoma picta (1/6; 16.7%), with an overall prevalence of 10.5%; virus genome persisted in the majority of seropositive rodents. Nucleotide sequence and phylogenetic analysis showed that the viruses belonged mainly to the three lineages previously identified. The data showed that MTNV and CARV were primarily carried by P. beatae and R. sumichrasti, respectively. In addition, the data revealed an apparent complex interaction between hantaviruses and their hosts, suggesting active transmission and/or spillover infections within sympatric rodent species.     

Sediment Metal Contamination in the Kafue River of Zambia and Ecological Risk Assessment

Zambia’s Kafue River receives wastes from various sources, resulting in metal pollution. This study determined the degree of contamination of 13 metals (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg and Pb) in Kafue River sediment and the associated ecological risks at six sites in three different seasons. The level of contamination for most metals showed significant site and seasonal differences. The contamination factor and pollution load index indicated that concentrations of most metals particularly copper (Cu), cobalt (Co), manganese (Mn) and arsenic (As) were very high at sites within the Copperbelt mining area. The geoaccumulation index showed an absence of anthropogenic enrichment with Cd and Hg at all the study sites and extreme anthropogenic enrichment with Cu at sites in the Copperbelt mining area. Potential ecological risk showed that Cu and As were likely to cause adverse biological effects to aquatic organisms in the Copperbelt mining region of the Kafue River.     

Genetic diversity of rabies virus in different host species and geographic regions of Zambia and Zimbabwe

Virus Genes - Rabies is endemic in Zambia and Zimbabwe. The previously investigated strains of rabies virus in central Zambia belong to the Africa 1b lineage, with similar circulating virus strains...     

Development of a tick-borne encephalitis serodiagnostic ELISA using recombinant Fc-antigen fusion proteins

Current diagnostic tests for tick-borne encephalitis virus (TBEV) infections require high-biosafety facilities for antigen preparation and can cross-react with other flaviviruses. There is, therefore, a need to develop safe, inexpensive serodiagnostic tools with high specificity and sensitivity. In this study, a recombinant plasmid that expresses the membrane and envelope (E) proteins of TBEV fused to the Fc domain of rabbit IgG was constructed and expressed in mammalian cells. The E-Fc proteins were secreted as soluble homodimers, which retained reactivity with anti-TBEV and anti-rabbit IgG antibodies. The E-Fc proteins were then used to develop an enzyme-linked immunosorbent assay (ELISA) to detect TBEV antibodies in rodent and human sera. Compared with the neutralization test, the ELISA had over 90% sensitivity and specificity. In addition, the assay showed no cross-reactivity with Japanese encephalitis virus antibodies. These findings suggest that the E-Fc ELISA may be a useful tool for TBEV serodiagnosis.     

Infection of Hantaan virus strain AA57 leading to pulmonary disease in laboratory mice

Hantaan virus (HTNV) is a causative agent of hemorrhagic fever with renal syndrome (HFRS). The pathogenesis of HFRS has not been fully elucidated, mainly due to the lack of a suitable animal model. In laboratory mice, HTNV causes encephalitis. However, that symptom is dissimilar to human hantavirus infections. We found that HTNV strain AA57 (isolated from Apodemus agrarius in Far East Russia) caused pulmonary disease in 2-week-old ICR mice. The clinical signs of the infected mice were piloerection, trembling, hunching, labored breathing, and body-weight loss. A large volume of pleural effusion was collected from thoracic cavities of the dead mice. Overall, 45% of the mice inoculated with 3000 focus forming units (FFU) of the virus began to show clinical symptoms at 8 days post-inoculation, and 25% of the inoculated mice died within 3 days of onset of the disease. The morbidity and mortality rates of the mice inoculated with 30-30,000 FFU of HTNV strain AA57 were roughly equivalent. The highest rates of virus positivity (11/12) and the highest titers of HTNV strain AA57 were detected in the lungs of the dead mice, while lower detection rates and viral titers were found in the heart, kidneys, spleen, and brain. Interstitial pneumonia, perivascular edema, hemorrhage, inflammatory infiltration and vascular failure were observed in the lungs of the sick mice. Hantaviral antigens were detected in the lung endothelial cells of the sick mice. The symptoms and pathology of this mouse model resemble those of hantavirus pulmonary syndrome (HPS) and, to a certain extent, those of HFRS. This is the first report that, in laboratory mice, the HFRS-related hantavirus causes a HPS-like disease and shares some symptom similarities with HFRS.     

Genetic diversity of hantaviruses in Mexico: identification of three novel hantaviruses from Neotominae rodents

A variety of hantaviruses are harbored by rodents in North and South America, some of which can cause hantavirus pulmonary syndrome. To obtain greater evolutionary insight into hantaviruses in the Americas, a total of 211 rodents were captured in the Mexican states of Guerrero and Morelos in 2006. Anti-hantavirus antibodies were detected in 27 of 211 serum samples (12.8%) by ELISA. The distribution of seropositive rodents was: 17 Peromyscus beatae, 1 Megadontomys thomasi, 1 Neotoma picta, 6 Reithrodontomys sumichrasti, and 2 Reithrodontomys megalotis. The hantavirus small (S), medium (M), and large (L) genome segments from P. beatae, R. sumichrasti, and R. megalotis were amplified and the sequences covering the open reading frames were determined. The hantaviruses from P. beatae, R. sumichrasti, and R. megalotis were provisionally designated Montano (MTN), Carrizal (CAR), and Huitzilac (HUI), respectively. The M segment amino acid identities among the Mexican hantaviruses were 80.8-93.0%. When these M segments were compared to those of known hantaviruses, MTN virus was most closely related to Limestone Canyon (LSC) virus (88.9% amino acid identity), while the CAR and HUI viruses were most closely related to El Moro Canyon (ELMC) virus (90-91% identity). Phylogenetic analysis revealed that the MTN, CAR, and HUI viruses occupy a monophyletic clade with the LSC, ELMC, and Rio Segundo viruses, which are harbored by Peromyscus boylii, R. megalotis, and Reithrodontomys mexicanus, respectively. The data obtained in this study provide important information for understanding the evolution of hantaviruses in the Americas.     

Isolation and characterization of hantaviruses in Far East Russia and etiology of hemorrhagic fever with renal syndrome in the region

Hemorrhagic fever with renal syndrome (HFRS) is a serious public health issue in Far East Russia. Two different hantaviruses were isolated from rodents captured in the Khabarovsk region: Amur virus (AMRV; Khekhtsir/AP209/2005 strain from Apodemus peninsulae) and Hantaan virus (HTNV; Galkino/AA57/2002 strain from A. agrarius). Genetic analysis of the new isolates revealed that the M and L segments were apparently different between AMRV and HTNV, but S segments of the two viruses were closer. The antigenicities of AMRV, HTNV, and Seoul virus (SEOV) were differentiated by cross-neutralization. Serological differential diagnoses of 67 HFRS patients in the Prymorsky and Khabarovsk regions of Far East Russia were conducted using a neutralization test. The results revealed that the major cause of HFRS varied with location in Far East Russia: SEOV for Vladivostok city in the Prymorsky region, AMRV in rural areas of the Primorsky region, and probably HTNV for the Khabarovsk region.