The CTLA-4 and PD-1/PD-L1 inhibitory pathways independently regulate host resistance to Plasmodium-induced acute immune pathology

PLoS Pathog. 2012 Feb;8(2):e1002504. doi: 10.1371/journal.ppat.1002504. Epub 2012 Feb 2.

Abstract

The balance between pro-inflammatory and regulatory immune responses in determining optimal T cell activation is vital for the successful resolution of microbial infections. This balance is maintained in part by the negative regulators of T cell activation, CTLA-4 and PD-1/PD-L, which dampen effector responses during chronic infections. However, their role in acute infections, such as malaria, remains less clear. In this study, we determined the contribution of CTLA-4 and PD-1/PD-L to the regulation of T cell responses during Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM) in susceptible (C57BL/6) and resistant (BALB/c) mice. We found that the expression of CTLA-4 and PD-1 on T cells correlates with the extent of pro-inflammatory responses induced during PbA infection, being higher in C57BL/6 than in BALB/c mice. Thus, ECM develops despite high levels of expression of these inhibitory receptors. However, antibody-mediated blockade of either the CTLA-4 or PD-1/PD-L1, but not the PD-1/PD-L2, pathways during PbA-infection in ECM-resistant BALB/c mice resulted in higher levels of T cell activation, enhanced IFN-γ production, increased intravascular arrest of both parasitised erythrocytes and CD8(+) T cells to the brain, and augmented incidence of ECM. Thus, in ECM-resistant BALB/c mice, CTLA-4 and PD-1/PD-L1 represent essential, independent and non-redundant pathways for maintaining T cell homeostasis during a virulent malaria infection. Moreover, neutralisation of IFN-γ or depletion of CD8(+) T cells during PbA infection was shown to reverse the pathologic effects of regulatory pathway blockade, highlighting that the aetiology of ECM in the BALB/c mice is similar to that in C57BL/6 mice. In summary, our results underscore the differential and complex regulation that governs immune responses to malaria parasites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Differentiation / immunology*
  • Antigens, Differentiation / metabolism
  • B7-H1 Antigen / immunology*
  • B7-H1 Antigen / metabolism
  • CD8-Positive T-Lymphocytes / immunology*
  • CD8-Positive T-Lymphocytes / metabolism
  • CTLA-4 Antigen / immunology*
  • CTLA-4 Antigen / metabolism
  • Erythrocytes / parasitology
  • Interferon-gamma / immunology
  • Lymphocyte Activation / immunology
  • Malaria, Cerebral / immunology
  • Malaria, Cerebral / microbiology
  • Malaria, Cerebral / pathology
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Plasmodium berghei / immunology
  • Plasmodium berghei / pathogenicity*
  • Programmed Cell Death 1 Receptor

Substances

  • Antigens, Differentiation
  • B7-H1 Antigen
  • CTLA-4 Antigen
  • Cd274 protein, mouse
  • Pdcd1 protein, mouse
  • Programmed Cell Death 1 Receptor
  • Interferon-gamma