Susceptibility to anthrax lethal toxin is controlled by three linked quantitative trait loci - PubMed (original) (raw)

Comparative Study

Susceptibility to anthrax lethal toxin is controlled by three linked quantitative trait loci

Ryan D McAllister et al. Am J Pathol. 2003 Nov.

Abstract

Anthrax lethal toxin (LT) is the principal virulence factor associated with lethal pathologies following infection with Bacillus anthracis. Macrophages are the primary effector cells mediating lethality since macrophage-depleted mice are resistant to LT challenge. Recently, Ltxs1, the gene controlling differential susceptibility of murine macrophages to cytolysis following in vitro exposure to LT, was identified as Kif1c. To directly assess the in vivo role of Kif1c alleles in mortality, we studied a panel of interval-specific recombinant congenic lines carrying various segments of central chromosome 11 derived from LT-resistant DBA/2 mice on the LT-susceptible BALB/c background. The results of this study reveal that mortality is controlled by three linked quantitative trait loci (QTL): Ltxs1/Kif1c (42-43 cM), Ltxs2 (35-37 cM), and Ltxs3 (45-47 cM). The Ltxs3 interval encompasses Nos2, which is an attractive candidate gene for Ltxs3. In this regard, we demonstrate that selective, pharmacologically based inhibition of Nos2 activity in vivo partially overrides genetic resistance to LT and that Nos2 expression as determined by reverse transcription-polymerase chain reaction differs significantly between DBA/2 and BALB/c macrophages. Additionally, to recapitulate dominant resistance to mortality as seen in (BALB/c x DBA/2) F(1) hybrids, DBA/2 alleles are required at all three QTL.

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Figures

Figure 1.

Figure 1.

A: Anthrax LT dose-response curves for BALB/c mice. All mice received intravenous injections of LT on day 0. The data are expressed as % mortality (number of animals dead on a given day/number of animals studied × 100) and are the cumulative combined results obtained with male and female BALB/cByJ, BALB/cAnN and BALB/cJax mice. B: Mortality in BALB/c, DBA/2, and CD2 F1 hybrid mice following the intravenous injection of 125:25 LT (125 μg PA:25 μg LF) on day 0. The data are expressed as % mortality (number of animals dead on a given day/number of animals studied × 100) and are the cumulative combined results for male and female mice by strain and/or substrain.

Figure 2.

Figure 2.

Mortality in C.D2 ISRC lines following the intravenous injection of 125:25 LT on day 0. The data are expressed as % mortality and are the cumulative combined results for both male and female mice for each ISRC line.

Figure 3.

Figure 3.

Selective, pharmacologically based inhibition of Nos2 activity partially overrides genetic resistance to LT in vivo. The data are expressed as % mortality and are the combined results for both male and female mice.

Figure 4.

Figure 4.

Nos2 expression differs between DBA/2 and BALB/c peritoneal macrophages. Resident peritoneal macrophages were isolated by lavage from DBA/2 and BALB/c mice and Nos2 expression levels assessed by Taqman PCR using cDNA generated by reverse transcription of mRNA isolated from equal numbers of cells stimulated for 24 hours with 100 ng/ml LPS and 25 U/ml mouse IFNγ. Nos2 levels are normalized with respect to DBA/2 levels. Data are presented as the normalized means ± SD (P value <0.05).

Figure 5.

Figure 5.

Mortality studies in C.D2 ISRC F1 hybrid mice indicate that protection requires resistance alleles at Ltxs1, Ltxs2, and Ltxs3 for complete protection from LT. Solid bars represent DBA/2 alleles, open bars represent BALB/c alleles and gray bars represent heterozygous regions. The mortality values are the cumulative totals observed at day 9 following the intravenous injection of 125:25 LT.

References

    1. Leppla SH: Anthrax toxin. Moss J Iglewski B Vaughan M Tu AT eds. Bacterial Toxins and Virulence Factors in Disease. 1995:pp 543-572 Dekker New York
    1. Bradley KA, Mogridge J, Mourez M, Collier RJ, Young JA: Identification of the cellular receptor for anthrax toxin. Nature 2001, 414:225-229 - PubMed
    1. Leppla SH: Anthrax toxin edema factor: a bacterial adenylate cyclase that increases cyclic AMP concentrations in eukaryotic cells. Proc Natl Acad Sci USA 1982, 79:3162-3166 - PMC - PubMed
    1. Klimpel KR, Arora N, Leppla SH: Anthrax toxin lethal factor contains a zinc metalloprotease consensus sequence which is required for lethal toxin activity. Mol Microbiol 194, 13:1093-1100 - PubMed
    1. Duesbery NS, Webb CP, Leppla SH, Gordon VM, Klimpel KR, Copeland TD, Ahn NG, Oskarsson MK, Fukasawa K, Paul KD, Vande Woude GF: Proteolytic inactivation of MAP-kinase-kinase by anthrax lethal factor. Science 1998, 280:734-737 - PubMed

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