A mathematical model of HTLV-I infection with two time delays

Xuejuan Lu1, Lulu Hui, Shengqiang Liu

  • 1Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, 3041#, 2 Yi-Kuang street, Harbin, 150080, China. lujuan02@163.com.

Insights

This study models Human T-cell leukaemia virus type I (HTLV-I) infection dynamics with time delays. Immune delays can destabilize T-cell responses, while intracellular delays may offer stability, creating complex viral dynamics.

Area of Science:

  • Mathematical biology
  • Immunology
  • Virology

Background:

  • Human T-cell leukaemia virus type I (HTLV-I) causes chronic infections.
  • CD8+ cytotoxic T lymphocytes (CTLs) are crucial for controlling viral infections.
  • Time delays in immune responses can significantly alter disease dynamics.

Purpose of the Study:

  • To develop a mathematical model for HTLV-I infection incorporating intracellular and immune time delays.
  • To analyze the impact of these delays on the stability of viral and immune responses.
  • To understand the conditions leading to viral clearance, chronic infection, or persistent CTL response.

Main Methods:

  • Mathematical modeling of CD8+ cytotoxic T lymphocytes (CTLs) response to HTLV-I.
  • Analysis of global dynamics based on reproductive numbers R0 and R1.
  • Investigation of equilibrium stability and Hopf bifurcations.
  • Numerical simulations to explore the effects of time delays.

Main Results:

  • Viral clearance occurs if R0 < 1.
  • Chronic infection without persistent CTL response if R1 < 1 < R0.
  • Persistent CTL response and chronic infection if R1 > 1.
  • Immune delay can destabilize the persistent CTL response equilibrium (HAM/TSP).

Conclusions:

  • The model's dynamics are governed by viral (R0) and immune (R1) reproductive numbers.
  • Time delays, particularly immune delays, play a critical role in HTLV-I infection stability.
  • Intracellular delays may stabilize, while immune delays destabilize the system, leading to complex dynamics.