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Susceptibilities of nonhuman primates to chronic wasting disease.

Race B, Meade-White KD, Miller MW, Barbian KD, Rubenstein R, LaFauci G, Cervenakova L, Favara C, Gardner D, Long D, Parnell M, Striebel J, Priola SA, Ward A, Williams ES, Race R, Chesebro B - Emerging Infect. Dis. (2009)

Bottom Line: Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids.In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection.Thus, these 2 species differed in susceptibility to CWD.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, Hamilton, Montana 59840, USA. raceb@niaid.nih.g

ABSTRACT
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy, or prion disease, that affects deer, elk, and moose. Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids. We used 2 nonhuman primate species, cynomolgus macaques and squirrel monkeys, as human models for CWD susceptibility. CWD was inoculated into these 2 species by intracerebral and oral routes. After intracerebral inoculation of squirrel monkeys, 7 of 8 CWD isolates induced a clinical wasting syndrome within 33-53 months. The monkeys' brains showed spongiform encephalopathy and protease-resistant prion protein (PrPres) diagnostic of prion disease. After oral exposure, 2 squirrel monkeys had PrPres in brain, spleen, and lymph nodes at 69 months postinfection. In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection. Thus, these 2 species differed in susceptibility to CWD. Because humans are evolutionarily closer to macaques than to squirrel monkeys, they may also be resistant to CWD.

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A) Western blot of chronic wasting disease (CWD) inocula showing protease-resistant prion protein (PrPres) in 8 CWD brain homogenate pools used for infecting nonhuman primates. Lane 1, 0.2-mg tissue equivalents of uninfected elk brain not treated with proteinase K; lanes 2–9, samples treated with proteinase K: lanes 2, 6, and 7, 0.12-mg tissue equivalents; lanes 3–5, 8, and 9, 0.67 mg tissue equivalents. PrPres was detected by using antibody L42 against PrP and enhanced chemiluminescence (GE Healthcare, Piscataway, NJ, USA). To provide optimal exposure for viewing PrP in all lanes, blot was exposed to film for 20 min. In this exposure, lanes 2, 6, 7, and 8 were exposed beyond the linear range; this blot could not be used to quantify relative PrPres levels. Values on the left are in kDa. For more accurate quantitations of PrPres, other gels with different amounts loaded were exposed for multiple times (see panel C). B) Titration of MD-3 CWD inoculum. End-point infectivity titrations were calculated for each CWD inoculum by inoculating 50 μL of serial 10-fold dilutions of each brain homogenate into transgenic mice expressing deer PrP, starting with a 1% (10–2) brain homogenate. Shown are data for an MD-3 inoculum. As the inoculum became more dilute, the incubation period (in days) and variability within a group increased. Each open circle represents 1 mouse in which clinical CWD developed. One mouse inoculated with a 10–6 dilution and 5 mice inoculated with a 10–7 dilution did not become sick after 625 days (solid circles). C) Infectivity titer and PrPres levels of each CWD pool. Titers are 50% infectious dose/g of brain homogenate. Relative level (%) of PrPres in each pool was measured by Western blot with a combination of serial dilutions and sequential exposure times in the linear response range for each sample. Data obtained from these comparisons are summarized in the PrPres column. All pools were compared with the pool with the highest PrPres signal (Elk-2), which was set at 100%.
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Figure 1: A) Western blot of chronic wasting disease (CWD) inocula showing protease-resistant prion protein (PrPres) in 8 CWD brain homogenate pools used for infecting nonhuman primates. Lane 1, 0.2-mg tissue equivalents of uninfected elk brain not treated with proteinase K; lanes 2–9, samples treated with proteinase K: lanes 2, 6, and 7, 0.12-mg tissue equivalents; lanes 3–5, 8, and 9, 0.67 mg tissue equivalents. PrPres was detected by using antibody L42 against PrP and enhanced chemiluminescence (GE Healthcare, Piscataway, NJ, USA). To provide optimal exposure for viewing PrP in all lanes, blot was exposed to film for 20 min. In this exposure, lanes 2, 6, 7, and 8 were exposed beyond the linear range; this blot could not be used to quantify relative PrPres levels. Values on the left are in kDa. For more accurate quantitations of PrPres, other gels with different amounts loaded were exposed for multiple times (see panel C). B) Titration of MD-3 CWD inoculum. End-point infectivity titrations were calculated for each CWD inoculum by inoculating 50 μL of serial 10-fold dilutions of each brain homogenate into transgenic mice expressing deer PrP, starting with a 1% (10–2) brain homogenate. Shown are data for an MD-3 inoculum. As the inoculum became more dilute, the incubation period (in days) and variability within a group increased. Each open circle represents 1 mouse in which clinical CWD developed. One mouse inoculated with a 10–6 dilution and 5 mice inoculated with a 10–7 dilution did not become sick after 625 days (solid circles). C) Infectivity titer and PrPres levels of each CWD pool. Titers are 50% infectious dose/g of brain homogenate. Relative level (%) of PrPres in each pool was measured by Western blot with a combination of serial dilutions and sequential exposure times in the linear response range for each sample. Data obtained from these comparisons are summarized in the PrPres column. All pools were compared with the pool with the highest PrPres signal (Elk-2), which was set at 100%.

Mentions: When the 8 pools of CWD (representing both wild and captive deer and elk) used as inocula were analyzed by immunoblot, PrPres in the 8 pools showed similar electrophoretic mobilities and glycoform patterns (Figure 1, panel A), but PrPres levels differed when quantitatively compared (Figure 1, panel C). To measure the level of infectivity in these pools, we titered each pool in transgenic mice expressing deer PrP (line 33; tgDeerPrP) (18). A typical endpoint dilution titration is shown in Figure 1, panel B. The 8 pools had 50% infectious dose (ID50) titers ranging from 6.3 × 107 to 5.0 × 108 ID50/g of brain homogenate (Figure 1, panel C). Comparison of titers with PrPres levels showed a partial correlation (Figure 1, panel C). For example, the CWD pool with the lowest infectivity titer (MD-2) was also the pool with the lowest PrPres level. However, for some pools, these tests showed discrepant values.


Susceptibilities of nonhuman primates to chronic wasting disease.

Race B, Meade-White KD, Miller MW, Barbian KD, Rubenstein R, LaFauci G, Cervenakova L, Favara C, Gardner D, Long D, Parnell M, Striebel J, Priola SA, Ward A, Williams ES, Race R, Chesebro B - Emerging Infect. Dis. (2009)

A) Western blot of chronic wasting disease (CWD) inocula showing protease-resistant prion protein (PrPres) in 8 CWD brain homogenate pools used for infecting nonhuman primates. Lane 1, 0.2-mg tissue equivalents of uninfected elk brain not treated with proteinase K; lanes 2–9, samples treated with proteinase K: lanes 2, 6, and 7, 0.12-mg tissue equivalents; lanes 3–5, 8, and 9, 0.67 mg tissue equivalents. PrPres was detected by using antibody L42 against PrP and enhanced chemiluminescence (GE Healthcare, Piscataway, NJ, USA). To provide optimal exposure for viewing PrP in all lanes, blot was exposed to film for 20 min. In this exposure, lanes 2, 6, 7, and 8 were exposed beyond the linear range; this blot could not be used to quantify relative PrPres levels. Values on the left are in kDa. For more accurate quantitations of PrPres, other gels with different amounts loaded were exposed for multiple times (see panel C). B) Titration of MD-3 CWD inoculum. End-point infectivity titrations were calculated for each CWD inoculum by inoculating 50 μL of serial 10-fold dilutions of each brain homogenate into transgenic mice expressing deer PrP, starting with a 1% (10–2) brain homogenate. Shown are data for an MD-3 inoculum. As the inoculum became more dilute, the incubation period (in days) and variability within a group increased. Each open circle represents 1 mouse in which clinical CWD developed. One mouse inoculated with a 10–6 dilution and 5 mice inoculated with a 10–7 dilution did not become sick after 625 days (solid circles). C) Infectivity titer and PrPres levels of each CWD pool. Titers are 50% infectious dose/g of brain homogenate. Relative level (%) of PrPres in each pool was measured by Western blot with a combination of serial dilutions and sequential exposure times in the linear response range for each sample. Data obtained from these comparisons are summarized in the PrPres column. All pools were compared with the pool with the highest PrPres signal (Elk-2), which was set at 100%.
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Related In: Results  -  Collection

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Figure 1: A) Western blot of chronic wasting disease (CWD) inocula showing protease-resistant prion protein (PrPres) in 8 CWD brain homogenate pools used for infecting nonhuman primates. Lane 1, 0.2-mg tissue equivalents of uninfected elk brain not treated with proteinase K; lanes 2–9, samples treated with proteinase K: lanes 2, 6, and 7, 0.12-mg tissue equivalents; lanes 3–5, 8, and 9, 0.67 mg tissue equivalents. PrPres was detected by using antibody L42 against PrP and enhanced chemiluminescence (GE Healthcare, Piscataway, NJ, USA). To provide optimal exposure for viewing PrP in all lanes, blot was exposed to film for 20 min. In this exposure, lanes 2, 6, 7, and 8 were exposed beyond the linear range; this blot could not be used to quantify relative PrPres levels. Values on the left are in kDa. For more accurate quantitations of PrPres, other gels with different amounts loaded were exposed for multiple times (see panel C). B) Titration of MD-3 CWD inoculum. End-point infectivity titrations were calculated for each CWD inoculum by inoculating 50 μL of serial 10-fold dilutions of each brain homogenate into transgenic mice expressing deer PrP, starting with a 1% (10–2) brain homogenate. Shown are data for an MD-3 inoculum. As the inoculum became more dilute, the incubation period (in days) and variability within a group increased. Each open circle represents 1 mouse in which clinical CWD developed. One mouse inoculated with a 10–6 dilution and 5 mice inoculated with a 10–7 dilution did not become sick after 625 days (solid circles). C) Infectivity titer and PrPres levels of each CWD pool. Titers are 50% infectious dose/g of brain homogenate. Relative level (%) of PrPres in each pool was measured by Western blot with a combination of serial dilutions and sequential exposure times in the linear response range for each sample. Data obtained from these comparisons are summarized in the PrPres column. All pools were compared with the pool with the highest PrPres signal (Elk-2), which was set at 100%.
Mentions: When the 8 pools of CWD (representing both wild and captive deer and elk) used as inocula were analyzed by immunoblot, PrPres in the 8 pools showed similar electrophoretic mobilities and glycoform patterns (Figure 1, panel A), but PrPres levels differed when quantitatively compared (Figure 1, panel C). To measure the level of infectivity in these pools, we titered each pool in transgenic mice expressing deer PrP (line 33; tgDeerPrP) (18). A typical endpoint dilution titration is shown in Figure 1, panel B. The 8 pools had 50% infectious dose (ID50) titers ranging from 6.3 × 107 to 5.0 × 108 ID50/g of brain homogenate (Figure 1, panel C). Comparison of titers with PrPres levels showed a partial correlation (Figure 1, panel C). For example, the CWD pool with the lowest infectivity titer (MD-2) was also the pool with the lowest PrPres level. However, for some pools, these tests showed discrepant values.

Bottom Line: Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids.In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection.Thus, these 2 species differed in susceptibility to CWD.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, Hamilton, Montana 59840, USA. raceb@niaid.nih.g

ABSTRACT
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy, or prion disease, that affects deer, elk, and moose. Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids. We used 2 nonhuman primate species, cynomolgus macaques and squirrel monkeys, as human models for CWD susceptibility. CWD was inoculated into these 2 species by intracerebral and oral routes. After intracerebral inoculation of squirrel monkeys, 7 of 8 CWD isolates induced a clinical wasting syndrome within 33-53 months. The monkeys' brains showed spongiform encephalopathy and protease-resistant prion protein (PrPres) diagnostic of prion disease. After oral exposure, 2 squirrel monkeys had PrPres in brain, spleen, and lymph nodes at 69 months postinfection. In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection. Thus, these 2 species differed in susceptibility to CWD. Because humans are evolutionarily closer to macaques than to squirrel monkeys, they may also be resistant to CWD.

Show MeSH
Related in: MedlinePlus