C57bl 6 cd45.1 mice

All work with infectious RVFV was completed in a biosafety level (BSL)-3 laboratory. Female 6–10-week-old WT C57BL/6 J and CD45.1 C57BL/6 mice were obtained from Jackson Laboratories and housed within ABSL-3 laboratories in microisolator pans in HEPA filtration racks, following standard barrier techniques. In all experiments, mice were evaluated for clinical signs of disease at least once daily and were euthanized according to a predetermined clinical illness scoring algorithm^{37 (link)}. At the time of euthanasia, mice were anesthetized with isoflurane and terminally bled. Collected specimens included liver, spleen, brain, popliteal lymph node, and/or whole blood. Splenocytes and other tissues were processed using manual disruption^{38 (link)}.
Stocks of recombinant WT RVFV (strain ZH501) and RVFV lacking NSs (DelNSsRVFV) were produced using reverse genetics and grown to passage 2^{12 (link),39 (link)}. Titers of all viral stocks were determined as the 50% tissue culture infective dose (TCID₅₀) on Vero E6 cells and visualized by indirect fluorescent-antibody assay (IFA) using a monoclonal mouse IgG1 anti-RVFV N primary antibody (custom, Genscript). Virus sequence identity was verified prior to use.

Zbtb46^gfp mice [027618], Cx3cr1^CreERT2 mice [020940], Rosa26-stop-TdTomato mice [007914], Cx3cr1^GFP/+ mice [005582] and CD45.1⁺ C57BL/6 mice [002014] were from The Jackson Laboratory. All the mice are in C57BL/6 background. Normal C57BL/6 mice (CD45.2⁺) were purchased from Shanghai Research Center for Model Organisms. All mice used in this study without specific explanation were 8- to 12-week-old males. Mice were housed in a standard animal facility, with a 12-hr light/dark cycle, in specific-pathogen-free environment. All animal experiments were approved by the Institutional Animal Care and Use Committee at Zhejiang University (protocol ZJU20190135).

STAT5 mutants were generated as described (Yamaji et al., 2013 (link)). Briefly, mice lacking the entire Stat5 locus (Stat5a/b^+/-) were crossed with mice lacking one-allele of Stat5a (Stat5a^+/- Stat5b^+/+) or Stat5b (Stat5a^+/+ Stat5b^+/-) to produce 8 combinations of Stat5 alleles (Figure 1A). We refer to each genotype according to the total number of Stat5 alleles that are retained. For example, two-allele Stat5a-deficient mice lack both Stat5a alleles but retain two Stat5b alleles (Stat5a^-/- Stat5b^+/+), while one-allele Stat5a-deficient mice lack both Stat5a alleles but retain one Stat5b allele (Stat5a^-/- Stat5b^+/-). CD45.1⁺ C57BL/6 mice were purchased from Jackson Labs (Bar Harbor, ME). Animals were handled in accordance with NIH guidelines and all experiments approved by the NIAMS Animal Care and Use Committee.