Protection of sheep by vaccination against experimental challenge with Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona.

AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and L. interrogans serovar Pomona. METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney-cross lambs, aged 9-11 weeks, were randomly allocated to a vaccinated group and a control group. Vaccinated lambs each received two 1.5-mL S/C doses of a multivalent leptospiral and clostridial vaccine, 4 weeks apart, and animals in the control groups received the same dose of saline. Groups of 12 vaccinated and 12 control lambs were randomly selected in each study for challenge with serovars Hardjo or Pomona. Challenge was initiated 16 weeks following the second vaccination with three daily doses of live leptospires by intranasal and conjunctival routes. Following challenge, urine samples were collected weekly for 6 weeks, for dark field microscopy and leptospiral culture; 6 weeks after challenge the lambs were slaughtered and kidneys collected for leptospiral culture. RESULTS: In lambs challenged with serovar Hardjo, 8/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive for leptospires following culture, compared with 0/12 lambs in the vaccinated group (p=0.001). In lambs challenged with serovar Pomona, 9/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive following culture, compared with 0/12 lambs in the vaccinated group (p<0.001). Prevention of renal colonisation and urinary shedding, expressed as the prevented fraction, was 100 (95% CI=61.7-100)% and 100 (95% CI=68.3-100)% against challenge with serovars Hardjo and Pomona, respectively, at 4 months after vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Use of a multivalent leptospiral and clostridial vaccine demonstrated protection against challenge from New Zealand strains of serovars of Hardjo and Pomona 4 months after vaccination in lambs first vaccinated at 9-11 weeks of age. Further studies are required to assess the duration of immunity against challenge in sheep.

The mouse Sb1.8 gene located at the distal end of the X chromosome is subject to X inactivation.

The mouse homolog of the human DXS423E (SB1.8) gene has been isolated by screening a mouse cDNA library. Like its human counterpart, the mouse Sb1.8 gene is X-linked, as shown by Southern blot analysis and by in situ hybridization to metaphase chromosomes. Sb1.8 was sublocalized to band F of the mouse X chromosome, distal to Alas2 and proximal to DXPas1, which confirms a region of conservation between band Xp11.21-p11.22 in human and band XF in mouse. In situ hybridization also showed that the Smcx (Xe169) gene maps near Sb1.8 in band F. The Sb1.8 gene was shown to be highly conserved in mammals; partial DNA sequence analysis indicates 92% identity between the mouse and human genes. In contrast to the human DXS423E gene, the mouse Sb1.8 gene is subject to X inactivation, as shown by restriction enzyme and sequence analysis of mRNA from mice with Searle's translocation (T(X;16)16H). Absence of Sb1.8 expression from the inactive mouse X chromosome in vitro was confirmed by analysis of a cell line (Hobmski) in which the M. spretus X chromosome is inactivated. The Sb1.8 gene is a new member of a group of genes that escape X inactivation in human, but are inactivated in mouse.

Linkage of the structural gene for uroporphyrinogen I synthase to markers on mouse chromosome 9 in a cross between feral and inbred mice.

The Ups locus has been mapped to mouse chromosome 9 in a three-point cross. The observed gene order is centromere-Ups-15-Mpi-1-22-Mod-1. Ups is unlinked to Lv, which encodes the previous enzyme in the heme biosynthesis pathway. Feral mice collected at Skive, Denmark, have been characterized at several biochemical loci; multiple differences from inbred strains make this a useful stock for linkage analysis.