O'Connor MA, Green WR. The role of indoleamine 2,3-dioxygenase in LP-BPM5 murine retroviral disease progression.
Virol J 2013;
10:154. [PMID:
23680027 PMCID:
PMC3751850 DOI:
10.1186/1743-422x-10-154]
[Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 05/06/2013] [Indexed: 11/10/2022] Open
Abstract
Background
Indoleamine 2,3-dioxygenase (IDO) is an immunomodulatory intracellular enzyme involved in tryptophan degradation. IDO is induced during cancer and microbial infections by cytokines, ligation of co-stimulatory molecules and/or activation of pattern recognition receptors, ultimately leading to modulation of the immune response. LP-BM5 murine retroviral infection induces murine AIDS (MAIDS), which is characterized by profound and broad immunosuppression of T- and B-cell responses. Our lab has previously described multiple mechanisms regulating the development of immunodeficiency of LP-BM5-induced disease, including Programmed Death 1 (PD-1), IL-10, and T-regulatory (Treg) cells. Immunosuppressive roles of IDO have been demonstrated in other retroviral models, suggesting a possible role for IDO during LP-BM5-induced retroviral disease progression and/or development of viral load.
Methods
Mice deficient in IDO (B6.IDO−/−) and wildtype C57BL/6 (B6) mice were infected with LP-BM5 murine retrovirus. MAIDS and LP-BM5 viral load were assessed at termination.
Results
As expected, IDO was un-inducible in B6.IDO−/− during LP-BM5 infection. B6.IDO−/− mice infected with LP-BM5 retrovirus succumbed to MAIDS as indicated by splenomegaly, serum hyper IgG2a and IgM, decreased responsiveness to B- and T-cell mitogens, conversion of a proportion of CD4+ T cells from Thy1.2+ to Thy1.2-, and increased percentages of CD11b+Gr-1+ cells. LP-BM5 infected B6.IDO−/− mice also demonstrated the development of roughly equivalent disease kinetics as compared to infected B6 mice. Splenic viral loads of B6 and B6.IDO−/− mice were also equivalent after infection as measured by LP-BM5-specific Def Gag and Eco Gag viral mRNA, determined by qRT-PCR.
Conclusions
Collectively, these results demonstrate IDO neither plays an essential role, nor is required, in LP-BM5-induced disease progression or LP-BM5 viral load.
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