HIV-1 Infection of Long-Lived Hematopoietic Precursors In Vitro and In Vivo

Abstract

Latent reservoirs in human-immunodeficiency-virus-1 (HIV-1)-infected individuals represent a major obstacle in finding a cure for HIV-1. Hematopoietic stem and progenitor cells (HSPCs) have been described as potential HIV-1 targets, but their roles as HIV-1 reservoirs remain controversial. Here we provide additional evidence for the susceptibility of several distinct HSPC subpopulations to HIV-1 infection in vitro and in vivo. In vitro infection experiments of HSPCs were performed with different HIV-1 Env-pseudotyped lentiviral particles and with replication-competent HIV-1. Low-level infection/transduction of HSPCs, including hematopoietic stem cells (HSCs) and multipotent progenitors (MPP), was observed, preferentially via CXCR4, but also via CCR5-mediated entry. Multi-lineage colony formation in methylcellulose assays and repetitive replating of transduced cells provided functional proof of susceptibility of primitive HSPCs to HIV-1 infection. Further, the access to bone marrow samples from HIV-positive individuals facilitated the detection of HIV-1 gag cDNA copies in CD34+ cells from eight (out of eleven) individuals, with at least six of them infected with CCR5-tropic HIV-1 strains. In summary, our data confirm that primitive HSPC subpopulations are susceptible to CXCR4- and CCR5-mediated HIV-1 infection in vitro and in vivo, which qualifies these cells to contribute to the HIV-1 reservoir in patients.

Targeting HIV persistence in the tissue

“…Evidence of HIV persistence in most tissues across the human body have been reported [78]. Recent literature shows detection of viral DNA and/or RNA at multiple additional tissue sites [79], including hepatocytes and liver-infiltrating CD4 + T cells [80 ▪ ], lung bronchoalveolar lavage samples [81], hematopoietic progenitor cells in bone marrow [82,83], kidney [84], urethra [10,31 ▪▪ ], testicles [85] and prostate [3]. Further, inflammation at a particular site, such as the gingival tissue [86] or the CNS [15 ▪▪ ], may act as the spark that unmasks persistent reservoirs, likely in the form of antigen-specific CD4 + T RM that remained in a particular tissue to provide long-term memory.…”

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

“…In general, in vitro infection with either wt or pseudotyped replication competent viruses involves a self-spreading infection among the target cells unless the time of the assay is shortened by design. Reporter genes are often inserted into the genome of pseudotyped viruses to assess the level of infection 90,94,95,[101][102][103] as an alternative to measuring viral proteins, nucleic acids, or cytopathic effects 91,98,100,104 . Target cells, stably transfected to express a reporter gene(s) when infected can also be used to quantify virus infection and assess the activity of antivirals, including neutralizing antibodies 101,[105][106][107][108][109] .…”

“…For the generation of enveloped VLP, retroviral (HIV-1 or murine leukemia virus derived) or rhabdoviral (VSV) based packaging vector systems are commonly used 110,119 , although other vectors are also described 101,108,121 . As with the pseudotyped viruses, to facilitate the assessment of VLP cell fusion and entry, VLP are often engineered to include a reporter gene encoding an enzyme or a fluorescent protein (luciferase, alkaline phosphatase, βgalactosidase, green fluorescent protein), where expression reflects the level of infection 97,99,102,103,113,114,122 .…”

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

“…In general, in vitro infection with either wt or pseudotyped replication competent viruses involves a self-spreading infection among the target cells, unless the time of the assay is shortened by design. Reporter genes are often inserted into the genome of pseudotyped viruses to assess the level of infection [ 98 , 102 , 103 , 109 , 110 , 111 ] as an alternative to measuring viral proteins, nucleic acids, or cytopathic effects [ 99 , 106 , 108 , 112 ]. Target cells, which are stably transfected to express the reporter gene(s) when infected, can also be used to quantify virus infection and assess the activity of antivirals, including neutralizing antibodies [ 109 , 113 , 114 , 115 , 116 , 117 ].…”

“…For the generation of enveloped VLP, retroviral- (HIV-1 or murine leukemia virus derived) or rhabdoviral (VSV)-based packaging vector systems are commonly used [ 118 , 127 ], although other vectors are also described [ 109 , 116 , 129 ]. As with the pseudotyped viruses, to facilitate the assessment of VLP cell fusion and entry, VLPs are often engineered to include a reporter gene encoding an enzyme or a fluorescent protein (luciferase, alkaline phosphatase, β-galactosidase, green fluorescent protein), where expression reflects the level of infection [ 105 , 107 , 110 , 111 , 121 , 122 , 130 ].…”