Role of maternal antibody in natural infection of Peromyscus maniculatus with Sin Nombre virus.

Data from naturally infected deer mice (Peromyscus maniculatus) were used to investigate vertical transmission of Sin Nombre virus (SNV) and SNV-specific antibody. The antibody prevalence in juvenile mice (14 g or less) was inversely proportional to the mass of the animal, with juvenile deer mice weighing less than 11 g most likely to be antibody positive (26.9%) and juvenile mice weighing between 13 and 14 g least likely to be antibody positive (12.9%). Although a significant sex bias in seropositivity was detected in adult deer mice, no significant sex bias in seropositivity was detected in juvenile animals. Ten juvenile deer mice were identified that had initially tested positive for SNV-specific immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA) but had subsequently tested negative when recaptured as adults. SNV RNA was detected by reverse transcriptase PCR (RT-PCR) in the blood of ELISA-positive adult deer mice but not in the blood of ELISA-positive juveniles. One of the juvenile mice initially tested negative for SNV RNA but later tested positive when recaptured as an ELISA-positive adult. The RT-PCR results for that individual correlated with the disappearance and then reappearance of SNV-specific IgG, indicating that the presence of SNV RNA at later time points was due to infection with SNV via horizontal transmission. SNV-specific antibody present in both ELISA-positive juvenile and adult mice was capable of neutralizing SNV. Additionally, our data indicate that SNV is not transmitted vertically.

Characterization of La Crosse virus RNA in autopsied central nervous system tissues.

A reverse transcription-PCR (RT-PCR) technique was used to detect La Crosse (LAC) virus RNA in the central nervous system (CNS) tissues of two patients who died of LAC encephalitis in 1960 and 1978. Viral RNA was readily detected by RT-PCR although the tissues had been stored frozen for up to 37 years. LAC virus was detected in the cerebral cortex but not in other CNS tissues. RT-PCR allowed detection of replicative forms of the virus, indicating that the virus was actively replicating in the specific CNS tissues. The small (S) RNA segments of the viruses from the CNS samples were demonstrated to be genetically similar by single-strand conformation polymorphism analyses. These S RNA segments were then sequenced; only two base changes were demonstrated between the 1960 and the 1978 samples, suggesting that LAC virus is genetically stable in areas of endemicity. The RT-PCR analyses of analyte directly from CNS tissues allows study of the virus without passage in cell culture.

Revival and identification of bacterial spores in 25- to 40-million-year-old Dominican amber.

A bacterial spore was revived, cultured, and identified from the abdominal contents of extinct bees preserved for 25 to 40 million years in buried Dominican amber. Rigorous surface decontamination of the amber and aseptic procedures were used during the recovery of the bacterium. Several lines of evidence indicated that the isolated bacterium was of ancient origin and not an extant contaminant. The characteristic enzymatic, biochemical, and 16S ribosomal DNA profiles indicated that the ancient bacterium is most closely related to extant Bacillus sphaericus.

Bacillus DNA in fossil bees: an ancient symbiosis?

We report here the isolation of DNA from abdominal tissue of four extinct stingless bees (Proplebeia dominicana) in Dominican amber, PCR amplification of a 546-bp fragment of the 16S rRNA gene from Bacillus spp., and their corresponding nucleotide sequences. These sequences were used in basic local alignment search tool searches of nonredundant nucleic acid data bases, and the highest scores were obtained with 16S rRNA sequences from Bacillus spp. Phylogenetic inference analysis by the maximum-likelihood method revealed close phylogenetic relationships of the four presumed ancient Bacillus sequences with Bacillus pumilus, B. firmus, B. subtilis, and B. circulans. These four extant Bacillus spp. are commonly isolated from abdominal tissue of stingless bees. The close phylogenetic association of the extracted DNA sequences with these bee colonizers suggests that a similar bee-Bacillus association existed in the extinct species P. dominicana.