[The role of large-scale testing platform in the prevention and control of the COVID-19 pandemic: an empirical study based on a novel numerical model]

Objective: China adopted an unprecedented province-scale quarantine since January 23rd 2020, after the novel coronavirus (COVID-19) broke out in Wuhan in December 2019. Responding to the challenge of limited testing capacity, large-scale (>20 000 tests per day) standardized and fully-automated laboratory (Huo-Yan) was built as an ad-hoc measure. There is so far no empirical data or mathematical model to reveal the impact of the testing capacity improvement since quarantine. Methods: Based on the suspected case data released by the Health Commission of Hubei Province and the daily testing data of Huo-Yan Laboratory, the impact of detection capabilities on the realization of "clearing" and "clearing the day" of supected cases was simulated by establishing a novel non-linear and competitive compartments differential model. Results: Without the establishment of Huo-Yan, the suspected cases would increase by 47% to 33 700, the corresponding cost of quarantine would be doubled, the turning point of the increment of suspected cases and the achievement of "daily settlement" (all newly discovered suspected cases are diagnosed according to the nucleic acid testing result) would be delayed for a whole week and 11 days. If the Huo-Yan Laboratory could ran at its full capacity, the number of suspected cases could start to decrease at least a week earlier, the peak of suspected cases would be reduced by at least 44%, and the quarantine cost could be reduced by more than 72%. Ideally, if a daily testing capacity of 10 500 tests was achieved immediately after the Hubei lockdown, "daily settlement" for all suspected cases could be achieved. Conclusions: Large-scale, standardized clinical testing platform, with nucleic acid testing, high-throughput sequencing, and immunoprotein assessment capabilities, need to be implemented simultaneously in order to maximize the effect of quarantine and minimize the duration and cost of the quarantine. Such infrastructure, for both common times and emergencies, is of great significance for the early prevention and control of infectious diseases.

[Urban Aerosol Hygroscopicity During Haze Weather]

The hygroscopicity of aerosols has an important influence on atmospheric visibility and is one of the main causes of haze pollution. Based on observations of the aerosol hygroscopic growth factor (GF), water soluble inorganic ions, and organic carbon/elemental carbon (OC/EC) data during haze weather from April 17 to May 21, in 2014, the hygroscopic properties of aerosols and corresponding effects on haze in Nanjing were analyzed. The results showed that the distribution of GF was bimodal and varied from 1.12 to 1.64. With the increase of particle size, the average hygroscopic growth factor (GF_mean) changed less and the standard deviation of wettability (σ) increased gradually; meanwhile, the degree of external mixing of chemical components increased gradually. The hygroscopicity of aerosol particles in the day was better than that at night, but the mixing degree was weaker than that at night; in non-haze weather, the hygroscopicity of aerosol particles was stronger and the degree of external mixing was higher, while the hygroscopicity and mixing degree of haze particles showed opposite trends. With the increase of haze levels, the hygroscopicity of aerosol particles grew weaker and the degree of external mixing decreased further. Relative humidity can have a significant impact on the chemical components of aerosols and their hygroscopic capacity. Under a low humidity background, the main chemical components of aerosols included NH₄⁺, NO₃^-, SO₄^2-, OC, and EC, and the content of OC/EC in aerosols during haze days was more abundant; in haze weather with low relative humidity, abundant organic matter was the main reason for the decrease of the moisture absorption capacity of small-scale aerosols. The level of relative humidity in the haze weather was also an important factor affecting the hygroscopic capacity of aerosols. The contents of (NH₄)₂SO₄, OC, and insoluble substances in aerosols were the highest, followed by NH₄NO₃. The contents of these chemical components showed obvious diurnal variation characteristics, which resulted in significant diurnal variation of the hygroscopicity of the aerosols. κ_chem calculated by the chemical composition and κ_mean acquired by observations using H-TDMA showed good consistency, and the correlation coefficient was 0.8903. In haze weather, the correlation between them was further enhanced. Therefore, the major chemical components of aerosols could be used to predict the hygroscopic properties of aerosols.

[Characteristics of Key Size Spectrum of PM2.5 Affecting Winter Haze Pollution in Taiyuan]

PM_2.5 is generally considered as a main pollutant causing the formation of haze. Based on meteorological parameters, aerosol distribution, and PM monitoring data in Taiyuan during November and December 2016, the characteristics of the key size spectrum of PM_2.5 affecting haze were discussed. During the observation period, haze was frequent and serious. Heavy haze time accounts for 25.35% of the total haze time. Haze events occurred frequently when the relative humidity was greater than 80% and wind speed was less than 1.5 m·s^-1, especially for severe haze. Mild and moderate level haze occurred frequently when the relative humidity was less than 80% and greater than 40% and when wind speed was less than 1.5 m·s^-1. Slight haze mainly occurred when the relative humidity was 20%-40% and the wind speed was 1.25-2.55 m·s^-1. The average mass concentration of PM_2.5 was 209.45 μg·m^-3, which was three times the level during non-haze events. With an increase in the haze level, the mass concentration of PM_2.5 and the ratio of PM_2.5/PM₁₀ increased. PM₁ was the key particle size affecting haze in the low humidity environment. PM_0.5 was the key particle size that affects slight haze, mild haze, and moderate haze in the high humidity environment, while PM₁ was the key particle size that affects heavy haze. The contribution of surface concentration to visibility decreased with high humidity, but the particle size increased by moisture absorption leading to an increase in the extinction efficiency factor, which compensated for the lack of surface concentration. The increase in the particle size parameter was an important factor for PM_2.5 affecting the haze pollution with high humidity.

Pathogenicity and distribution of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs

The pathogenesis of highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) strain (HuN4) is poorly understood. Therefore, highly pathogenic PRRSV strain (HuN4) and its derivative strain (HuN4-F112) (obtained by propagation in MARC145 cells for 112 passages) were inoculated into a total of 48 PRRSV-sero-negative pigs (age: 4-5 weeks) by the intranasal route. Virological, pathological and in situ hybridization analyses were performed. The results exhibited that pigs infected with HuN4 showed a loss of appetite, decrease in body weight, raised body temperature and respiratory symptoms, along with interstitial pneumonia lesions. In the HuN4 group, multifocal interstitial pneumonia with macrophage infiltration was found in the lung. The lesions in the lymph node were characterized by collapsed follicles, depletion of germinal centres and reduction in lymphocytes. Perivascular cuffing and glial nodules were observed in the brains of some pigs. By comparison, the HuN4-F112 group had milder lesions. PRRSV was detected in macrophages, alveolar epithelial cells and vascular endothelial cells in the tonsil and lymph nodes. The PRRSV amounts in the pigs infected with HuN4 were 10(5) -10(9) copies/ml in the blood and 10(10) -10(11) copies/g in the lung tissues, whereas the virus amounts with HuN4-F112 were 10(2.15) -10(3.13) copies/ml in the blood and 10(3.0) -10(3.6) copies/g in the lung. Our results demonstrate that the PRRS HuN4 virus infects alveolar epithelial cells, macrophages and vascular endothelial cells causing diffuse alveolar damage and lymph node necrosis. Its higher pathogenicity compared with HuN4-F112 virus may be explained in part by higher replication rate in the previously mentioned organs.

Expression profiling suggests a regulatory role of gallbladder in lipid homeostasis

AIM: To examine expression profile of gallbladder using microarray and to investigate the role of gallbladder in lipid homeostasis.

METHODS: 33P-labelled cDNA derived from total RNA of gallbladder tissue was hybridized to a cDNA array representing 17000 cDNA clusters. Genes with intensities ≥2 and variation <0.33 between two samples were considered as positive signals with subtraction of background chosen from an area where no cDNA was spotted. The average gray level of two gallbladders was adopted to analyze its bioinformatics. Identified target genes were confirmed by touch-down polymerase chain reaction and sequencing.

RESULTS: A total of 11 047 genes expressed in normal gallbladder, which was more than that predicted by another author, and the first 10 genes highly expressed (high gray level in hybridization image), e.g., ARPC5 (2225.88±90.46), LOC55972 (2220.32±446.51) and SLC20A2 (1865.21±98.02), were related to the function of smooth muscle contraction and material transport. Meanwhile, 149 lipid-related genes were expressed in the gallbladder, 89 of which were first identified (with gray level in hybridization image), e.g., FASN (11.42±2.62), APOD (92.61±8.90) and CYP21A2 (246.11±42.36), and they were involved in each step of lipid metabolism pathway. In addition, 19 of those 149 genes were gallstone candidate susceptibility genes (with gray level in hybridization image), e.g., HMGCR (10.98±0.31), NPC1 (34.88±12.12) and NR1H4 (16.8±0.65), which were previously thought to be expressed in the liver and/or intestine tissue only.

CONCLUSION: Gallbladder expresses 11 047 genes and takes part in lipid homeostasis.

Effect of oral beta interferon on subsequent immune responsiveness

Oral administration of myelin antigens reduces the incidence and severity of EAE in rat and mouse models and decreases the frequency of MBP-reactive cells and the frequency of attacks in some patients with multiple sclerosis. Low-dose oral tolerance has been shown to be mediated by Th2-type regulatory cells that secrete TGFbeta and IL-4/IL-10. Adjuvants and cytokines may modulate oral tolerance. The addition of betaIFN to the experimental therapy regimen, either orally or by intraperitoneal injection, has been shown to enhance the suppressive effects of oral myelin antigens when either are fed the suboptimal dosing regimen to suppress EAE. The current studies were conducted to elucidate the mechanism of the observed in vivo synergy of betaIFN and antigen feeding. Analysis of the in vitro proliferative response and cytokine production by lymphocytes from fed animals in response to specific antigen in culture shows that the synergistic effect may be related to both independent suppression of the immune response by oral betaIFN and enhanced production of TGFbeta and IL-4/IL-10. There was an unexpected increase in the production of gammaIFN by lymphocytes in vitro after three doses of oral betaIFN in vivo. These observations have important implications for the use of cytokines to modulate oral tolerance.