Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.

A B S T R A C TERV3 (HERV-R) is a complete human endogenous retrovirus located on the long arm of chromosome 7. It is expressed in several human tissues as LTR env spliced transcripts (9 and 3.5 kb). The highest level of expression is to be found in placenta and virus expression is down-regulated in choriocarcinoma cell lines. By means of in situ hybridization, the expression of ERV3 =was studied in selected human reproductive and embryonic tissues. It is concluded that (a) ERV3 env is expressed in syncytiotrophoblasts not only in the placenta but also in hydatidiform moles and choriocarcinomas ( irrespective of origin) (b) ERV3 expression in placenta correlates to cell fusion but probably not to the fertilization process itself (c) ERV3 %is highly expressed in certain cells in spermatogenesis but not in the Sertoli or Leydig cells, and finally (d) ERV3 env is expressed in certain embryonic tissues such as the adrenal gland and nervous tissues.

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