Experimental Infection of Cynomolgus Macaques (Macaca fascicularis) with Aerosolized Monkeypox Virus

Monkeypox virus (MPXV) infection in humans results in clinical symptoms very similar to ordinary smallpox. Aerosol is a route of secondary transmission for monkeypox, and a primary route of smallpox transmission in humans. Therefore, an animal model for aerosol exposure to MPXV is needed to test medical countermeasures. To characterize the pathogenesis in cynomolgus macaques (Macaca fascicularis), groups of macaques were exposed to four different doses of aerosolized MPXV. Blood was collected the day before, and every other day after exposure and assessed for complete blood count (CBC), clinical chemistry analysis, and quantitative PCR. Macaques showed mild anorexia, depression, and fever on day 6 post-exposure. Lymphadenopathy, which differentiates monkeypox from smallpox, was observed in exposed macaques around day 6 post-exposure. CBC and clinical chemistries showed abnormalities similar to human monkeypox cases. Whole blood and throat swab viral loads peaked around day 10, and in survivors, gradually decreased until day 28 post-exposure. Survival was not dose dependent. As such, doses of 4×104 PFU, 1×105 PFU, or 1×106 PFU resulted in lethality for 70% of the animals, whereas a dose of 4×105 PFU resulted in 85% lethality. Overall, cynomolgus macaques exposed to aerosolized MPXV develop a clinical disease that resembles that of human monkeypox. These findings provide a strong foundation for the use of aerosolized MPXV exposure of cynomolgus macaques as an animal model to test medical countermeasures against orthopoxviruses

Serum chemistries in macaques exposed to aerosolized MPXV.

<p>The dotted lines indicate the normal reference range; n: number of animals. Graphs show average <b>A</b>) total protein, <b>B</b>) albumin, <b>C</b>) lactate dehydrogenase (LDH), <b>D</b>) C-reactive protein, <b>E</b>) aspartate transaminase (AST), <b>F</b>) and alanine transaminase (ALT), <b>G</b>) urea nitrogen.</p

Average number of leukocytes and platelets in macaques after exposed to aerosolized MPXV.

<p>The dotted lines indicate the normal reference range; n: number of animals. Graphs are shown for <b>A</b>) total white blood cells (WBC), <b>B</b>) percentage of granulocytes (GR), <b>C</b>) percentage of lymphocytes (LY), <b>D</b>) platelets (PLT) for all MPXV dosage groups, and survivors versus non-survivors (right).</p

Pathology and presence of MPXV antigen in lung tissue.

<p>Figures <b>A–D</b> are histological sections of lung tissues from cynomolgus macaques infected via aerosolized MPXV. Positive immunoreactivity for orthopoxvirus antigen, shown as brown staining, is associated with necrotizing lesions primarily concentrated around bronchi and bronchioles. [Immunoperoxidase method using rabbit polyclonal antibody to vaccinia virus; original magnification ×40 (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012880#pone-0012880-g006" target="_blank">Figure 6A</a>) or ×20 (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012880#pone-0012880-g006" target="_blank">Figure 6</a> B, C, D)]. <b>A</b>) 4×10⁴ PFU (day 10 post-exposure). <b>B</b>) 1×10⁵ PFU (day 8 post-exposure). <b>C</b>) 4×10⁵ PFU (day 11 post-exposure). <b>D</b>) 1×10⁶ PFU (day 9 post-exposure). <b>E</b>) Percent immunoreactivity in the lungs of non-survivors by dosage group, measured by digital microscopy image analysis.</p

Key histopathologic lesions in cynomolgus macaques exposed to aerosolized MPXV.

<p>* = lesion seen in survivors<b>.</b></p

Summary of inhaled doses, fever, and disease outcome in cynomolgus macaques exposed to aerosolized MPXV.

a<p>Defined as the first day with >8 h of significant temperature elevation (as determined by ARIMA modeling).</p>b<p>Calculated as the number of days (converted to hours) with 12 or more h of significant temperature elevation.</p>c<p>Calculated as the sum of the significant temperature elevations.</p>d<p>The maximum change in temperature.</p>e<p>Calculated by dividing fever hours by fever duration in hours.</p>f<p>Mean time-to-death.</p

Chronic kidney disease and aging differentially diminish bone material and microarchitecture in C57Bl/6 mice.

Chronic kidney disease (CKD) is a common disease of aging and increases fracture risk over advanced age alone. Aging and CKD differently impair bone turnover and mineralization. We thus hypothesize that the loss of bone quality would be greatest with the combination of advanced age and CKD. We evaluated bone from young adult (6 mo.), middle-age (18 mo.), and old (24 mo.) male C57Bl/6 mice three months following either 5/6th nephrectomy, to induce CKD, or Sham procedures. CKD exacerbated losses of cortical and trabecular microarchitecture associated with aging. Aging and CKD each resulted in thinner, more porous cortices and fewer and thinner trabeculae. Bone material quality was also reduced with CKD, and these changes to bone material were distinct from those due to age. Aging reduced whole-bone flexural strength and modulus, micrometer-scale nanoindentation modulus, and nanometer-scale tissue and collagen strain (small-angle x-ray scattering [SAXS]. By contrast, CKD reduced work to fracture and variation in bone tissue modulus and composition (Raman spectroscopy), and increased percent collagen strain. The increased collagen strain burden was associated with loss of toughness in CKD. In addition, osteocyte lacunae became smaller, sparser, and more disordered with age for Sham mice, yet these age-related changes were not clearly observed in CKD. However, for CKD, larger lacunae positively correlated with increased serum phosphate levels, suggesting that osteocytes play a role in systemic mineral homeostasis. This work demonstrates that CKD reduces bone quality, including microarchitecture and bone material properties, and that loss of bone quality with age is compounded by CKD. These findings may help reconcile why bone mass does not consistently predict fracture in the CKD population, as well as why older individuals with CKD are at high risk of fragility

Chronic kidney disease and aging differentially diminish bone material and microarchitecture in C57Bl/6 mice.

Chronic kidney disease (CKD) is a common disease of aging and increases fracture risk over advanced age alone. Aging and CKD differently impair bone turnover and mineralization. We thus hypothesize that the loss of bone quality would be greatest with the combination of advanced age and CKD. We evaluated bone from young adult (6 mo.), middle-age (18 mo.), and old (24 mo.) male C57Bl/6 mice three months following either 5/6th nephrectomy, to induce CKD, or Sham procedures. CKD exacerbated losses of cortical and trabecular microarchitecture associated with aging. Aging and CKD each resulted in thinner, more porous cortices and fewer and thinner trabeculae. Bone material quality was also reduced with CKD, and these changes to bone material were distinct from those due to age. Aging reduced whole-bone flexural strength and modulus, micrometer-scale nanoindentation modulus, and nanometer-scale tissue and collagen strain (small-angle x-ray scattering [SAXS]. By contrast, CKD reduced work to fracture and variation in bone tissue modulus and composition (Raman spectroscopy), and increased percent collagen strain. The increased collagen strain burden was associated with loss of toughness in CKD. In addition, osteocyte lacunae became smaller, sparser, and more disordered with age for Sham mice, yet these age-related changes were not clearly observed in CKD. However, for CKD, larger lacunae positively correlated with increased serum phosphate levels, suggesting that osteocytes play a role in systemic mineral homeostasis. This work demonstrates that CKD reduces bone quality, including microarchitecture and bone material properties, and that loss of bone quality with age is compounded by CKD. These findings may help reconcile why bone mass does not consistently predict fracture in the CKD population, as well as why older individuals with CKD are at high risk of fragility

Inhibition of myostatin prevents microgravity-induced loss of skeletal muscle mass and strength.

The microgravity conditions of prolonged spaceflight are known to result in skeletal muscle atrophy that leads to diminished functional performance. To assess if inhibition of the growth factor myostatin has potential to reverse these effects, mice were treated with a myostatin antibody while housed on the International Space Station. Grip strength of ground control mice increased 3.1% compared to baseline values over the 6 weeks of the study, whereas grip strength measured for the first time in space showed flight animals to be -7.8% decreased in strength compared to baseline values. Control mice in space exhibited, compared to ground-based controls, a smaller increase in DEXA-measured muscle mass (+3.9% vs +5.6% respectively) although the difference was not significant. All individual flight limb muscles analyzed (except for the EDL) weighed significantly less than their ground counterparts at the study end (range -4.4% to -28.4%). Treatment with myostatin antibody YN41 was able to prevent many of these space-induced muscle changes. YN41 was able to block the reduction in muscle grip strength caused by spaceflight and was able to significantly increase the weight of all muscles of flight mice (apart from the EDL). Muscles of YN41-treated flight mice weighed as much as muscles from Ground IgG mice, with the exception of the soleus, demonstrating the ability to prevent spaceflight-induced atrophy. Muscle gene expression analysis demonstrated significant effects of microgravity and myostatin inhibition on many genes. Gamt and Actc1 gene expression was modulated by microgravity and YN41 in opposing directions. Myostatin inhibition did not overcome the significant reduction of microgravity on femoral BMD nor did it increase femoral or vertebral BMD in ground control mice. In summary, myostatin inhibition may be an effective countermeasure to detrimental consequences of skeletal muscle under microgravity conditions