Evaluation of Copper Levels in Dental Calculus of OSF Patients with Chewing Dried Areca-Nut Quids in Hunan Province of Mainland China.

Dental calculus is a potential material that can be used for assessing chronic exposure to trace heavy metals in oral cavity as it is a long-term reservoir. The aim of this study was to investigate the correlation between dental calculus copper levels and risk of oral submucous fibrosis (OSF) due to chewing dried areca-nut quids in Mainland China. This study included 34 OSF (grade 1) sufferers with dried areca-nut quids chewing as the patient group and 23 healthy individuals without areca-nut chewing as the control group. The dental calculus sample was obtained from all 57 participants and evaluated by inductively coupled plasma mass spectrometry (ICP-MS) for dental calculus level of copper. This work revealed that the mean copper level of dental calculus was significantly higher in OSF (grade 1) sufferers with areca-nut chewing than those in healthy individuals without areca-nut chewing (p < 0.001). This work provided an evidence to support that there may be a positive correlation between elevated levels of copper in dental calculus caused by chewing dried areca-nut quids and an increased risk of developing OSF in Mainland China.

The effects of CTL immune response on HIV infection model with potent therapy, latently infected cells and cell-to-cell viral transmission.

In this paper, a mathematical model is formulated to investigate the effect of cytotoxic T lymphocyte (CTL) immune response on human immunodeficiency virus (HIV) infection dynamics. The model includes latently infected cells, antiretroviral therapy, cell-free virus infection and cell-to- cell viral transmission. By constructing Lyapunov functionals, the global stability of three equilibria is obtained. More specifically, the infection-free equilibrium $E_{f}$ is globally asymptotically stable when the basic reproductive numbers $\mathcal{R}_{0}<1 implying="" that="" the="" virus="" can="" be="" eventually="" cleared="" the="" infected="" equilibrium="" without="" immune="" response="" e_="" w="" is="" globally="" asymptotically="" stable="" when="" the="" ctl="" immune="" response="" reproduction="" number="" mathcal="" r="" _="" 1="" is="" less="" than="" one="" and="" mathcal="" r="" _="" 0="" is="" greater="" than="" one="" implying="" that="" the="" infection="" becomes="" chronic="" but="" ctl="" immune="" response="" has="" not="" been="" established="" the="" infected="" equilibrium="" with="" immune="" response="" e_="" c="" is="" globally="" asymptotically="" stable="" when="" mathcal="" r="" _="" 1="">1$, implying that the infection becomes chronic with persistent CTL immune response. Numerical simulations confirm the above theoretical results. Moreover, the inclusion of CTL immune response can generate a higher level of uninfected CD4+ T cells, and significantly reduce infected cells and viral load. These results may help to improve the understanding of HIV infection dynamics.

Modeling Citrus Huanglongbing transmission within an orchard and its optimal control.

Citrus Huanglongbing (HLB) is the most devastating citrus disease worldwide. In this paper, a deterministic dynamical model is proposed to explore the transmission dynamics of HLB between citrus tree and Asian citrus psyllid (ACP). Using the theory of dynamical system, the dynamics of the model are rigorously analyzed. The results show that the disease-free equilibrium is globally asymptotically stable when the basic reproduction number $\mathscr{R}_0 < 1$, and when $\mathscr{R}_0 > 1$ the system is uniformly persistent. Applying the global sensitivity analysis of $\mathscr{R}_0$, some parameters that have the greatest impact on HLB transmission dynamics are obtained. Furthermore, the optimal control theory is applied to the model to study the corresponding optimal control problem. Both analytical and numerical results show that: (1) the infected ACP plays a decisive role in the transmission of HLB in citrus trees, and eliminating the ACP will be helpful to curtail the spread of HLB; (2) optimal control strategy is superior to the constant control strategy in decreasing the prevalence of the diseased citrus trees, and the cost of implementing optimal control is much lower than that of the constant control strategy; and (3) spraying insecticides is more effective than other control strategies in reducing the number of ACP in the early phase of the transmission of HLB. These theoretical and numerical results may be helpful in making public policies to control HLB in orchards more effectively.

Global dynamics of a vector-host epidemic model with age of infection.

In this paper, a partial differential equation (PDE) model is proposed to explore the transmission dynamics of vector-borne diseases. The model includes both incubation age of the exposed hosts and infection age of the infectious hosts which describe incubation-age dependent removal rates in the latent period and the variable infectiousness in the infectious period, respectively. The reproductive number R0 is derived. By using the method of Lyapunov function, the global dynamics of the PDE model is further established, and the results show that the basic reproduction number R0 determines the transmission dynamics of vector-borne diseases: the disease-free equilibrium is globally asymptotically stable if R0 ≤ 1, and the endemic equilibrium is globally asymptotically stable if R0 > 1. The results suggest that an effective strategy to contain vector-borne diseases is decreasing the basic reproduction number R0 below one.