High rates of molecular evolution in hantaviruses

Hantaviruses are rodent-borne Bunyaviruses that infect the Arvicolinae, Murinae, and Sigmodontinae subfamilies of Muridae. The rate of molecular evolution in the hantaviruses has been previously estimated at approximately 10(-7) nucleotide substitutions per site, per year (substitutions/site/year), based on the assumption of codivergence and hence shared divergence times with their rodent hosts. If substantiated, this would make the hantaviruses among the slowest evolving of all RNA viruses. However, as hantaviruses replicate with an RNA-dependent RNA polymerase, with error rates in the region of one mutation per genome replication, this low rate of nucleotide substitution is anomalous. Here, we use a Bayesian coalescent approach to estimate the rate of nucleotide substitution from serially sampled gene sequence data for hantaviruses known to infect each of the 3 rodent subfamilies: Araraquara virus ( Sigmodontinae), Dobrava virus ( Murinae), Puumala virus ( Arvicolinae), and Tula virus ( Arvicolinae). Our results reveal that hantaviruses exhibit shortterm substitution rates of 10(-2) to 10(-4) substitutions/site/year and so are within the range exhibited by other RNA viruses. The disparity between this substitution rate and that estimated assuming rodent-hantavirus codivergence suggests that the codivergence hypothesis may need to be reevaluated.

Natural Host Relationships and Genetic Diversity of Rodent-Associated Hantaviruses in Southeastern Brazil

Objective: Hantaviruses are rodent-borne RNA viruses that have caused hantavirus cardiopulmonary syndrome in several Brazilian regions. In the present study, geographical distribution, seroprevalence, natural host range, and phylogenetic relations of rodent-associated hantaviruses collected from seven counties of Southeastern Brazil were evaluated. Methods: ELISA, RT-PCR and phylogenetic analysis were used in this study. Results: Antibodies to hantavirus were detected in Bolomys lasiurus, Akodon sp. and Oligoryzomys sp., performing an overall seroprevalence of 5.17%. All seropositive rodents were associated with grasslands or woods surrounded by sugar cane fields. Phylogenetic analysis of partial S- and M-segment sequences showed that viral sequences isolated from B. lasiurus specimens clustered with Araraquara virus. However, a sequence from Akodon sp. shared 100% similarity with Argentinian/Chilean viruses based on the partial S- segment amino acid sequence. Conclusion: These results indicate that there are associations between rodent reservoirs and hantaviruses in some regions of Southeastern Brazil, and suggest the existence of additional hantavirus genetic diversity and host ecology in these areas. Copyright (C) 2008 S. Karger AG, Basel

Detection of hantaviruses in Brazilian rodents by SYBR-Green-based real-time RT-PCR

Current knowledge of the pathogenic hantavirus indicates that wild rodents are its primary natural reservoir. Specific primers to detect the presence of viral genomes were developed using an SYBR-Green-based real-time RT-PCR protocol. One hundred sixty-four rodents native to the Atlantic Forest biome were captured in So Paulo State, Brazil, and their tissues were tested. The presence of hantavirus RNA was detected in sixteen rodents: three specimens of Akodon montensis, three of Akodon cursor, two of Necromys lasiurus, one of Juliomys sp., one of Thaptomys nigrita, five of Oligoryzomys nigripes, and one of Oryzomys sp. This SYBR Green real-time RT-PCR method for detection of hantavirus may be useful for surveying hantaviruses in Brazil.

A serosurvey for hantavirus infection in wild rodents from the states of Rio de Janeiro and Pernambuco, Brazil

Sera from 269 rodents obtained during the routine surveillance operations in plague areas of Rio de Janeiro and Pernambuco states, Brazil were tested by ELISA for specific IgG antibodies against a recombinant nucleocapsid (N) protein of Araraquara hantavirus. ELISA-positive sera were submitted to reverse transcriptase-polymerase chain reaction (RT-PCR) for amplification of the virus genome and later sequencing for identification of the viral variant. The samples from the state of Pernambuco were antibody negative, and although four from Rio de Janeiro were ELISA-positive, they failed to yield viral cDNA by RT-PCR. This is the first report of the presence of antibodies to a hantavirus among rodents from Rio de Janeiro and suggests the possibility of human cases of hantavirus pulmonary syndrome (HPS) in that state, although no case has yet been reported. (C) 2008 Elsevier B.V. All rights reserved.