Mario Santiago, PhD
Associate Professor, Medicine-Infectious Disease

Graduate School :
  • PhD, University of Alabama at Birmingham (2003)
Department: Medicine-Infectious Disease

Professional Titles

  • Associate Professor

Research Interests

Our laboratory studies the interplay between the innate and adaptive immune response against retroviruses to conceptually advance vaccine and cure strategies against HIV/AIDS and SARS-CoV-2. We are specifically interested in “restriction factors” – host proteins that could directly inhibit viruses but we discovered also play critical roles in shaping adaptive immune responses. These factors could be regulated by Type I interferons, thus highlighting possibilities for clinical translation.


  • Hasenkrug KJ, Feldmann F, Myers L, Santiago ML, Guo K, Barrett BS, Mickens KL, Carmody A, Okumura A, Rao D, Collins MM, Messer RJ, Lovaglio J, Shaia C, Rosenke R, van Doremalen N, Clancy C, Saturday G, Hanley P, Smith BJ, Meade-White K, Shupert WL, Hawman DW, Feldmann H. Recovery from Acute SARS-CoV-2 Infection and Development of Anamnestic Immune Responses in T Cell-Depleted Rhesus Macaques. mBio. 2021 Aug 31;12(4):e0150321. PubMed PMID: 34311582
  • Castleman MJ, Dillon SM, Thompson TA, Santiago ML, McCarter MD, Barker E, Wilson CC. Gut Bacteria Induce Granzyme B Expression in Human Colonic ILC3s In Vitro in an IL-15-Dependent Manner. J Immunol. 2021 Jun 15;206(12):3043-3052. PubMed PMID: 34117105
  • Guo K, Barrett BS, Mickens KL, Vladar EK, Morrison JH, Hasenkrug KJ, Poeschla EM, Santiago ML. Interferon Resistance of Emerging SARS-CoV-2 Variants. bioRxiv. 2021 Dec 10. PubMed PMID: 33758840
  • Guo K, Shen G, Kibbie J, Gonzalez T, Dillon SM, Smith HA, Cooper EH, Lavender K, Hasenkrug KJ, Sutter K, Dittmer U, Kroehl M, Kechris K, Wilson CC, Santiago ML. Qualitative Differences Between the IFNa subtypes and IFNß Influence Chronic Mucosal HIV-1 Pathogenesis. PLoS Pathog. 2020 Oct;16(10):e1008986. PubMed PMID: 33064743
  • Ickler J, Francois S, Widera M, Santiago ML, Dittmer U, Sutter K. HIV infection does not alter interferon a/ß receptor 2 expression on mucosal immune cells. PLoS One. 2020;15(1):e0218905. PubMed PMID: 31935222
  • Miller CM, Barrett BS, Chen J, Morrison JH, Radomile C, Santiago ML, Poeschla EM. Systemic Expression of a Viral RdRP Protects against Retrovirus Infection and Disease. J Virol. 2020 Apr 16;94(9). PubMed PMID: 32051266
  • Agazio A, Cimons J, Shotts KM, Guo K, Santiago ML, Pelanda R, Torres RM. Histone H2A-Reactive B Cells Are Functionally Anergic in Healthy Mice With Potential to Provide Humoral Protection Against HIV-1. Front Immunol. 2020;11:1565. PubMed PMID: 32849530
  • Dillon SM, Guo K, Castleman MJ, Santiago ML and Wilson CC. Quantifying HIV-1-Mediated Gut CD4+ T cell death in the Lamina Propria Aggregate Culture (LPAC) Model. Bio-Protocol. 2020;10(2):e3486.
  • Uchil PD, Pi R, Haugh KA, Ladinsky MS, Ventura JD, Barrett BS, Santiago ML, Bjorkman PJ, Kassiotis G, Sewald X, Mothes W. A Protective Role for the Lectin CD169/Siglec-1 against a Pathogenic Murine Retrovirus. Cell Host Microbe. 2019 Jan 9;25(1):87-100.e10. PubMed PMID: 30595553
  • Castleman MJ, Dillon SM, Purba CM, Cogswell AC, Kibbie JJ, McCarter MD, Santiago ML, Barker E, Wilson CC. Commensal and Pathogenic Bacteria Indirectly Induce IL-22 but Not IFN? Production From Human Colonic ILC3s via Multiple Mechanisms. Front Immunol. 2019;10:649. PubMed PMID: 30984202
  • Dittmer U, Sutter K, Kassiotis G, Zelinskyy G, Bánki Z, Stoiber H, Santiago ML, Hasenkrug KJ. Friend retrovirus studies reveal complex interactions between intrinsic, innate and adaptive immunity. FEMS Microbiol Rev. 2019 Sep 1;43(5):435-456. PubMed PMID: 31087035
  • Hasenkrug KJ, Lavender KJ, Santiago ML, Sutter K, Dittmer U. Different Biological Activities of Specific Interferon Alpha Subtypes. mSphere. 2019 Jul 24;4(4). PubMed PMID: 31341068
  • Dickow J, Francois S, Kaiserling RL, Malyshkina A, Drexler I, Westendorf AM, Lang KS, Santiago ML, Dittmer U, Sutter K. Diverse Immunomodulatory Effects of Individual IFNa Subtypes on Virus-Specific CD8( ) T Cell Responses. Front Immunol. 2019;10:2255. PubMed PMID: 31608062
  • Miller SM, Miles B, Guo K, Folkvord J, Meditz AL, McCarter MD, Levy DN, MaWhinney S, Santiago ML, Connick E. Follicular Regulatory T Cells Are Highly Permissive to R5-Tropic HIV-1. J Virol. 2017 Sep 1;91(17). PubMed PMID: 28615202
  • Getahun A, Wemlinger SM, Rudra P, Santiago ML, van Dyk LF, Cambier JC. Impaired B cell function during viral infections due to PTEN-mediated inhibition of the PI3K pathway. J Exp Med. 2017 Apr 3;214(4):931-941. PubMed PMID: 28341640
  • Dillon SM, Kibbie J, Lee EJ, Guo K, Santiago ML, Austin GL, Gianella S, Landay AL, Donovan AM, Frank DN, McCARTER MD, Wilson CC. Low abundance of colonic butyrate-producing bacteria in HIV infection is associated with microbial translocation and immune activation. AIDS. 2017 Feb 20;31(4):511-521. PubMed PMID: 28002063
  • Wang Y, Schmitt K, Guo K, Santiago ML, Stephens EB. Role of the single deaminase domain APOBEC3A in virus restriction, retrotransposition, DNA damage and cancer. J Gen Virol. 2016 Jan;97(1):1-17. PubMed PMID: 26489798
  • Dillon SM, Lee EJ, Donovan AM, Guo K, Harper MS, Frank DN, McCarter MD, Santiago ML, Wilson CC. Enhancement of HIV-1 infection and intestinal CD4 T cell depletion ex vivo by gut microbes altered during chronic HIV-1 infection. Retrovirology. 2016 Jan 14;13:5. PubMed PMID: 26762145
  • Li SX, Barrett BS, Guo K, Kassiotis G, Hasenkrug KJ, Dittmer U, Gibbert K, Santiago ML. Tetherin/BST-2 promotes dendritic cell activation and function during acute retrovirus infection. Sci Rep. 2016 Feb 5;6:20425. PubMed PMID: 26846717
  • Li SX, Barrett BS, Guo K, Santiago ML. Tetherin/BST-2: Restriction Factor or Immunomodulator?. Curr HIV Res. 2016;14(3):235-46. PubMed PMID: 26957198
  • Lavender KJ, Gibbert K, Peterson KE, Van Dis E, Francois S, Woods T, Messer RJ, Gawanbacht A, Müller JA, Münch J, Phillips K, Race B, Harper MS, Guo K, Lee EJ, Trilling M, Hengel H, Piehler J, Verheyen J, Wilson CC, Santiago ML, Hasenkrug KJ, Dittmer U. Interferon Alpha Subtype-Specific Suppression of HIV-1 Infection In Vivo. J Virol. 2016 Jul 1;90(13):6001-13. PubMed PMID: 27099312
  • Wang Y, Wang Z, Pramanik A, Santiago ML, Qiu J, Stephens EB. A chimeric human APOBEC3A protein with a three amino acid insertion confers differential HIV-1 and adeno-associated virus restriction. Virology. 2016 Nov;498:149-63. PubMed PMID: 27584592
  • Rubtsova K, Rubtsov AV, Halemano K, Li SX, Kappler JW, Santiago ML, Marrack P. T Cell Production of IFN? in Response to TLR7/IL-12 Stimulates Optimal B Cell Responses to Viruses. PLoS One. 2016 Nov 23;11(11):e0166322. PubMed PMID: 27880772
  • Dillon SM, Kibbie J, Lee EJ, Guo K, Santiago ML, Austin GL, Gianella S, Landay AL, Donovan AM, Frank DN, McCarter MD, Wilson CC. Low abundance of colonic butyrate-producing bacteria in HIV infection is associated with microbial translocation and immune activation. AIDS. 2016 Dec 19. [Epub ahead of print] PubMed PMID: 28002063
  • Warren CJ, Xu T, Guo K, Griffin LM, Westrich JA, Lee D, Lambert PF, Santiago ML, Pyeon D. APOBEC3A functions as a restriction factor of human papillomavirus. J Virol. 2015 Jan;89(1):688-702. PubMed PMID: 25355878
  • Halemano K, Barrett BS, Heilman KJ, Morrison TE, Santiago ML. Requirement for Fc effector mechanisms in the APOBEC3/Rfv3-dependent neutralizing antibody response. J Virol. 2015 Apr;89(7):4011-4. PubMed PMID: 25589647
  • Guo K, Halemano K, Schmitt K, Katuwal M, Wang Y, Harper MS, Heilman KJ, Kuwata T, Stephens EB, Santiago ML. Immunoglobulin VH gene diversity and somatic hypermutation during SIV infection of rhesus macaques. Immunogenetics. 2015 Jul;67(7):355-70. PubMed PMID: 25994147
  • Harper MS, Guo K, Gibbert K, Lee EJ, Dillon SM, Barrett BS, McCarter MD, Hasenkrug KJ, Dittmer U, Wilson CC, Santiago ML. Interferon-a Subtypes in an Ex Vivo Model of Acute HIV-1 Infection: Expression, Potency and Effector Mechanisms. PLoS Pathog. 2015 Nov;11(11):e1005254. PubMed PMID: 26529416
  • Gibbert K, Francois S, Sigmund AM, Harper MS, Barrett BS, Kirchning CJ, Lu M, Santiago ML, Dittmer U. Friend retrovirus drives cytotoxic effectors through Toll-like receptor 3. Retrovirology. 2014 Dec 24;11(1):1. [Epub ahead of print] PubMed PMID: 25539593
  • Connick E, Folkvord JM, Lind KT, Rakasz EG, Miles B, Wilson NA, Santiago ML, Schmitt K, Stephens EB, Kim HO, Wagstaff R, Li S, Abdelaal HM, Kemp N, Watkins DI, MaWhinney S, Skinner PJ. Compartmentalization of simian immunodeficiency virus replication within secondary lymphoid tissues of rhesus macaques is linked to disease stage and inversely related to localization of virus-specific CTL. J Immunol. 2014 Dec 1;193(11):5613-25. PubMed PMID: 25362178
  • Barrett BS, Guo K, Harper MS, Li SX, Heilman KJ, Davidson NO, Santiago ML. Reassessment of murine APOBEC1 as a retrovirus restriction factor in vivo. Virology. 2014 Nov;468-470:601-8. PubMed PMID: 25303118
  • Katuwal M, Wang Y, Schmitt K, Guo K, Halemano K, Santiago ML, Stephens EB. Cellular HIV-1 inhibition by truncated old world primate APOBEC3A proteins lacking a complete deaminase domain. Virology. 2014 Nov;468-470:532-44. PubMed PMID: 25262471
  • Li SX, Barrett BS, Heilman KJ, Messer RJ, Liberatore RA, Bieniasz PD, Kassiotis G, Hasenkrug KJ, Santiago ML. Tetherin promotes the innate and adaptive cell-mediated immune response against retrovirus infection in vivo. J Immunol. 2014 Jul 1;193(1):306-16. PubMed PMID: 24872193
  • Halemano K, Guo K, Heilman KJ, Barrett BS, Smith DS, Hasenkrug KJ, Santiago ML. Immunoglobulin somatic hypermutation by APOBEC3/Rfv3 during retroviral infection. Proc Natl Acad Sci U S A. 2014 May 27;111(21):7759-64. PubMed PMID: 24821801
  • Steele AK, Lee EJ, Manuzak JA, Dillon SM, Beckham JD, McCarter MD, Santiago ML, Wilson CC. Microbial exposure alters HIV-1-induced mucosal CD4 T cell death pathways Ex vivo. Retrovirology. 2014 Feb 4;11:14. PubMed PMID: 24495380
  • Cavrois M, Neidleman J, Santiago ML, Derdeyn CA, Hunter E, Greene WC. Enhanced fusion and virion incorporation for HIV-1 subtype C envelope glycoproteins with compact V1/V2 domains. J Virol. 2014 Feb;88(4):2083-94. PubMed PMID: 24335304
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General Information

Graduate Schools:
  • PhD, University of Alabama at Birmingham (2003)
Department: Medicine-Infectious Disease
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Campus Box C290
Aurora, CO 80045

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