Viable <i>C</i>. <i>parvum</i> priming provides greater protection against re-challenge than either CpG-ODN or <i>S</i>. Typhi.

Abstract

<p>(A, B) Comparison of protective immunity following priming with either viable and heat-inactivated (Δ) <i>C</i>. <i>parvum</i> 10⁶. (A) Growth of PD-fed mice through 23 days post-priming with either 4x10⁶ viable (<i>C</i>. <i>parvum</i>) or 4x10⁶ heat-inactivated (Δ<i>C</i>. <i>parvum</i>). Mice were challenged with viable 4<i>x</i>10⁷ <i>C</i>. <i>parvum</i> oocysts on day 20 post-priming. *<i>P</i><0.05 for Δ<i>C</i>. <i>parvum-C</i>. <i>parvum</i> vs. <i>C</i>. <i>parvum</i>-<i>C</i>. <i>parvum</i> (d3 and d23); ^^<i>P</i><0.01 for <i>C</i>. <i>parvum</i>-PBS vs PBS-<i>C</i>. <i>parvum</i> (d23); ^###<i>P</i><0.001 for <i>C</i>. <i>parvum</i>-<i>C</i>. <i>parvum</i> vs. PBS-<i>C</i>. <i>parvum</i> (d23). (B) RT-PCR of <i>Cryptosporidium</i> stool shedding on experimental days 21 and 23 (day 1 and day 3 after <i>C</i>. <i>parvum</i> 10⁷ challenge, respectively). *<i>P</i><0.05 and *<i>P</i><0.01 for <i>C</i>. <i>parvum</i>-<i>C</i>. <i>parvum</i> vs either PBS-<i>C</i>. <i>parvum</i> or Δ<i>C</i>. <i>parvum-C</i>. <i>parvum</i>. (C,D) 3-week-old C57Bl/6 mice were conditioned on PD for 7 days prior to orogastric inoculation with 10⁶ <i>C</i>. <i>parvum</i>, intranasal (i.n.) 10⁹ <i>S</i>. Typhi 908<i>htr</i>, i.n. CpG-ODN 1668 (100 mcg), or PBS (100 mcl) as indicated (n = 10/group). On day 21, mice were re-challenged with either PBS or <i>C</i>. <i>parvum</i> 10⁷. (C) Growth as percentage of initial weight, normalized to the day of 10⁷ <i>C</i>. <i>parvum</i> challenge (Day 0). The group labeled “All uninfected” includes animals that received either PBS during both inoculations, CpG followed by PBS, or <i>S</i>. Typhi followed by PBS (n = 5/group x 3 = 15) given all three groups grew similarly and were never exposed to <i>C</i>. <i>parvum</i> (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004820#pntd.0004820.s004" target="_blank">S4 Fig</a>). *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001 for PBS–<i>C</i>.<i>p</i>.10⁷ (red) vs <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷, ^<i>P</i><0.05 for CpG-<i>C</i>.<i>p</i>.10⁷ (yellow) vs <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷, and ^#<i>P</i><0.05 for <i>S</i>. Typhi-<i>C</i>.<i>p</i>.10⁷ (green) vs <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷). Horizontal lines designate significant differences at <i>P</i><0.05 between CpG-<i>C</i>.<i>p</i>.10⁷ (yellow), <i>S</i>. Typhi-<i>C</i>.<i>p</i>.10⁷ (green), and PBS-<i>C</i>.<i>p</i>.10⁷ (red) vs. All uninfected controls, respectively. (D) Parasite fecal shedding in serial fecal pellets collected on indicated experimental days post <i>C</i>. <i>parvum</i> 10⁷ challenge. *<i>P</i><0.05 for PBS–<i>C</i>.<i>p</i>.10⁷ vs. <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷, ^<i>P</i><0.05 for CpG-<i>C</i>.<i>p</i>.10⁷ vs <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷, and ^#<i>P</i><0.05 for <i>S</i>. Typhi-<i>C</i>.<i>p</i>.10⁷ vs <i>C</i>.<i>p</i>.10^6-<i>C</i>.<i>p</i>.10⁷. Data is representative of two replicate experiments.</p