Expansion of Activated Memory CD4+ T Cells Affects Infectivity of CCR5-Tropic HIV-1 in Humanized NOD/SCID/JAK3null Mice

Abstract

Humanized mice reconstituted with human hematopoietic cells have been developed as an experimental animal model for human immunodeficiency virus type 1 (HIV-1) infection. Myeloablative irradiation is usually performed to augment the engraftment of donor hematopoietic stem cells (HSCs) in recipient mice; however, some mouse strains are susceptible to irradiation, making longitudinal analysis difficult. We previously attempted to construct humanized NOD/SCID/JAK3null (hNOJ) mice, which were not irradiated prior to human HSC transplantation. We found that, over time, many of the reconstituted CD4+ T cells expanded with an activated effector memory phenotype. Therefore, the present study used hNOJ mice that were irradiated (hNOJ (IR+)) or not (hNOJ (IR−)) prior to human HSC transplantation to examine whether the development and cellularity of the reconstituted CD4+ T cells were influenced by the degree of chimerism, and whether they affected HIV-1 infectivity. Indeed, hNOJ (IR+) mice showed a greater degree of chimerism than hNOJ (IR−) mice. However, the conversion of CD4+ T cells to an activated effector memory phenotype, with a high percentage of cells showing Ki-67 expression, occurred in both hNOJ (IR+) and hNOJ (IR−) mice, probably as a result of lymphopenia-induced homeostatic expansion. Furthermore, when hNOJ (IR+) and hNOJ (IR−) mice, which were selected as naïve- and memory CD4+ T cell subset-rich groups, respectively, were infected with CCR5-tropic HIV-1 in vivo, virus replication (as assessed by the plasma viral load) was delayed; however, the titer subsequently reached a 1-log higher level in memory-rich hNOJ (IR−) mice than in naïve-rich hNOJ (IR+) mice, indicating that virus infectivity in hNOJ mice was affected by the different status of the reconstituted CD4+ T cells. Therefore, the hNOJ mouse model should be used selectively, i.e., according to the specific experimental objectives, to gain an appropriate understanding of HIV-1 infection/pathogenesis.

Humanized mice dually challenged with R5 and X4 HIV-1 show preferential R5 viremia and restricted X4 infection of CCR5+CD4+ T cells

“…In humans, CCR5 is expressed predominantly on memory CD4 þ T cells [30,31], and we previously demonstrated that the CCR5 þ CD4 þ T cell population in humanized mice comprises a high proportion of cells with an activated memory phenotype [18]. During the early stage of a primary HIV-1 infection, the virus preferentially targets activated CCR5 þ CD4 þ T cells rather than other CD4 þ T cell populations (such as resting naïve CD4 þ T cells) [32,33], thereby promoting efficient virus production [34].…”

“…Humanized NOJ (hNOJ) mice were constructed as described previously [18,21] with some modifications. Briefly, human umbilical cord blood was donated by the Tokyo Cord Blood Bank (Tokyo, Japan) after receiving written informed consent.…”

“…In addition, RNAs prepared from HIV-1 NL-E or HIV-1 NLAD8-D viral stocks were used as external controls. These virus copy numbers were determined by targeting to the gag region as described previously [18]. Based on the EGFP and DsRed copy numbers of external controls, those of samples from HIV-1-infected hNOJ mice were determined.…”

“…Cells were stained with suitable combinations of fluorescence-conjugated monoclonal antibodies as described previously [18]. The following antibodies were purchased from BioLegend (San Diego, CA): anti-human CD3 conjugated to PerCP or Pacific Blue; anti-human CD4 conjugated to FITC, Pacific Blue, PE-Cy7, or Alexa Fluor 700; anti-human CD8 conjugated to PE or Pacific Blue; and anti-human CD195/CCR5 conjugated to Alexa Fluor 647.…”

“…This allowed us to distinguish cells infected by these viruses in a dual infection model [17]. In addition, we recently developed a humanized mouse model of HIV-1 infection [18]. Here, we used both of these tools to clarify the dynamics of early phase R5 and X4 HIV-1 infection in vivo.…”