<p>In this paper, we establish an HIV infection model with general incidence rate, CTL immune response and immune impairment. The model emphasizes the role of inflammatory cytokines in viral infection and investigates the impact of the time delays on viral transmission, including intracellular delay <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation>, virus replication delay <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\tau _2\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> and immune delay <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\tau _3\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>3</mn> </msub> </math></EquationSource> </InlineEquation>. Firstly, we make some reasonable hypotheses about the general incidence rates. Based on these hypotheses, three feasible equilibria and two key thresholds are obtained. Secondly, theoretical research demonstrates that for all <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\tau _1\geqslant 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>τ</mi> <mn>1</mn> </msub> <mo>⩾</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\tau _2\geqslant 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>τ</mi> <mn>2</mn> </msub> <mo>⩾</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\tau _3\geqslant 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>τ</mi> <mn>3</mn> </msub> <mo>⩾</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, the stability of the infection-free equilibrium <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(E_0\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation> as well as the immune-inactivated equilibrium <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(E_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> is entirely determined by the virus reproductive number <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(R_0\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>R</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation> and the immunity-activated reproductive number <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(R_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>R</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation>. When <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(R_1&gt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>R</mi> <mn>1</mn> </msub> <mo>&gt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\tau _3=0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>τ</mi> <mn>3</mn> </msub> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>, the immune-activated equilibrium <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(E^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>E</mi> <mo>∗</mo> </msup> </math></EquationSource> </InlineEquation> is stable. However, as <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\tau _3\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>3</mn> </msub> </math></EquationSource> </InlineEquation> increases, the dynamical behavior of equilibrium <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(E^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>E</mi> <mo>∗</mo> </msup> </math></EquationSource> </InlineEquation> changes, and Hopf bifurcation occurs. Finally, we provide a specific model for numerical simulations to validate the corresponding theoretical results.</p>

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Threshold dynamics of a cytokine-enhanced general viral infection model with delayed CTL immune response

  • Zihao Hu,
  • Lili Lv,
  • Junxian Yang,
  • Qiang Li

摘要

In this paper, we establish an HIV infection model with general incidence rate, CTL immune response and immune impairment. The model emphasizes the role of inflammatory cytokines in viral infection and investigates the impact of the time delays on viral transmission, including intracellular delay \(\tau _1\) τ 1 , virus replication delay \(\tau _2\) τ 2 and immune delay \(\tau _3\) τ 3 . Firstly, we make some reasonable hypotheses about the general incidence rates. Based on these hypotheses, three feasible equilibria and two key thresholds are obtained. Secondly, theoretical research demonstrates that for all \(\tau _1\geqslant 0\) τ 1 0 , \(\tau _2\geqslant 0\) τ 2 0 and \(\tau _3\geqslant 0\) τ 3 0 , the stability of the infection-free equilibrium \(E_0\) E 0 as well as the immune-inactivated equilibrium \(E_1\) E 1 is entirely determined by the virus reproductive number \(R_0\) R 0 and the immunity-activated reproductive number \(R_1\) R 1 . When \(R_1>1\) R 1 > 1 and \(\tau _3=0\) τ 3 = 0 , the immune-activated equilibrium \(E^*\) E is stable. However, as \(\tau _3\) τ 3 increases, the dynamical behavior of equilibrium \(E^*\) E changes, and Hopf bifurcation occurs. Finally, we provide a specific model for numerical simulations to validate the corresponding theoretical results.