25-Hydroxycholesterol Protects Host against Zika Virus Infection and Its Associated Microcephaly in a Mouse Model

Abstract

Zika virus (ZIKV) has become a public health threat due to its global transmission and link to severe congenital disorders. The host immune responses to ZIKV infection have not been fully elucidated, and effective therapeutics are not currently available. Herein, we demonstrated that cholesterol-25-hydroxylase (CH25H) was induced in response to ZIKV infection and that its enzymatic product, 25-hydroxycholesterol (25HC), was a critical mediator of host protection against ZIKV. Synthetic 25HC addition inhibited ZIKV infection in vitro by blocking viral entry, and treatment with 25HC reduced viremia and conferred protection against ZIKV in mice and rhesus macaques. 25HC suppressed ZIKV infection and reduced tissue damage in human cortical organoids and the embryonic brain of the ZIKV-induced mouse microcephaly model. Our findings highlight the protective role of CH25H during ZIKV infection and the potential use of 25HC as a natural antiviral agent to combat ZIKV infection and prevent ZIKV-associated outcomes, such as microcephaly.

Keywords: 25HC; CH25H; ZIKV; antiviral immunity; microcephaly.

Figure 1. ZIKV-Triggered Induction of CH25H Plays an Important Role in Host Anti-ZIKV Immunity

(A) A549 cells were infected with ZIKV (GZ01/2016 strain, MOI 5) for 24 hr, RNA-seq was performed, and the top 50 genes upregulated by ZIKV infection in A549 cells were shown. (B) A549 cells were infected with indicated MOI of ZIKV (GZ01/2016 strain) for 24 hr, CH25H mRNA expression was measured by qRT-PCR. (C and D) WT and CH25H^−/− A549 cells were infected with ZIKV (GZ01/2016 strain, MOI 0.1) for 48 hr, ZIKV in cell lysates, and the supernatant was measured by qRT-PCR (C) and plaque assay (D), respectively. (E) HeLa cells were transfected with plasmids expressing GFP, IRF1, CH25H, or CH25H-M (hydroxylase activity-dead mutant) for 24 hr, followed by infecting cells with ZIKV (GZ01/2016 strain) for 48 hr at MOI of 0.1. The titer of ZIKV in the supernatant was quantified by plaque assay. (F) BHK-21 cells were treated with conditioned media from HeLa cells expressing the indicated genes for 12 hr and infected with ZIKV (GZ01/2016 strain, 200PFU). Then, the BHK-21 cells were subjected to plaque assay. Data of (B)–(F) are shown as mean ± SEM from three independent experiments. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, unpaired Student’s t test. See also Figure S1–S3.

Figure 2. 25HC Broadly Inhibits Flaviviruses Infection

(A and B) Vero cells were pretreated with EtOH or indicated dose of 25HC for 8 hr, followed by ZIKV infection (GZ01/2016 strain, MOI 0.1). The titer of ZIKV in the supernatant was quantified by (A) plaque assay and (B) qRT-PCR. (C–F) Vero cells were pretreated with indicated amount of 25HC for 8 hr and then infected with (C) ZIKV GZ01/2016 strain, (D) DENV, (E) YFV, and (F) WNV at MOI 0.1. Viral RNA copies in cell lysates were quantified by qRT-PCR. IC₅₀ of 25HC to ZIKV, DENV, YFV, and WNV were calculated and indicated. All data are shown as mean ± SEM from three independent experiments. **p ≤ 0.01, unpaired Student’s t test. See also Figure S4.

Figure 3. 25HC Suppressed ZIKV Infection by Blocking Viral Entry

(A) BHK-21 cells were treated with EtOH, 1 and 5 µM 25HC, and NITD008 for 12 hr, followed by infecting cells with ZIKV (GZ01/2016 strain, 200 PFU/well) at 4°C for 1 hr. Cells were washed with cold PBS and incubated at 37°C for 1 hr. The titer of internalized virus was measured with plaque assay. (B) C6/36 cells were infected with DENV (MOI 0.2) for 4 days and treated with 25HC for another 8 hr. Syncythia formation was stimulated with medium (pH 5.8) for 2 hr and then replaced with fresh regular medium. 24 hr post stimulation, C6/36 cells were stained with Giemsa. 4G2 and NITD008 were used as positive and negative controls, respectively. Syncythias were defined as the cells containing four or more nuclei. The number of syncythias in samples with EtOH was set to 100%. (C) A549 cells were pretreated with indicated concentration of Liposome, and 25HC or EtOH, for 8 hr. Cells were infected with ZIKV (GZ01/2016 strain, MOI 0.3) in 37°C, followed by plaque assay at 48 hpi. (D) BHK-21 cells were transfected with RNA from ZIKV/DENV replicon. 6 hr post transfection, 25HC was added into cells, and subsequently, renilla luciferase activity in cell lysates was determined at 48 hr post transfection. NITD008 was used as positive control. All data are shown as mean ± SEM from three independent experiments, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, unpaired Student’s t test. See also Figure S5.

Figure 4. 25HC Reduces ZIKV Viremia and Improves Survival in Mice

(A) 3- to 4 week-old female BALB/c mice were injected i.p. with 25HC (50 mg/kg) or vehicle HβCD for 12 hr and subjected to ZIKV infection i.p. (1 × 10⁵ PFU GZ01/2016 strain). The viral copy number in serum was quantified by qRT-PCR at 1 dpi. Vehicle: n = 6; 25HC: n = 9. (B–E) 3- to 4-week-old female A129 mice were pretreated with 25HC or vehicle as described in (A) and 12 hr later were infected i.p. with 2 × 10⁵ PFU (B) or 2 × 10³ PFU (C–E) ZIKV (GZ01/2016 strain). 25HC or vehicle were administrated daily for seven days. (B) The rate of mice survival until 21 dpi and (C) the level of ZIKV RNA in serum at 4 dpi (D) and 7 dpi (E) and in the brain were measured by qRT-PCR. Log-Rank (Mantel-Cox) test were used in (B), vehicle: n = 6; 25HC: n = 8 *p ≤ 0.05. Median value of (A, C–E) has been shown, vehicle: n = 7; 25HC: n = 8 (C and D); vehicle/25HC: n = 5 (E). *p ≤ 0.05, **p ≤ 0.01, unpaired Student’s t test.

Figure 5. 25HC Protects Rhesus Monkeys from ZIKV Infection

(A and B) Rhesus monkeys were injected i.v. with 25HC (1.5 mg/kg) (n = 2) or the vehicle control EtOH (n = 3), followed by infection with 1×10³ PFU of ZIKV (GZ01/2016 strain) i.m. Animals were treated with 25HC or EtOH daily for 7 days. Viral copy numbers in (A) serum and (B) urine of control monkeys or 25HC-pretreated were measured by qRT-PCR. (C) The level of IFN-γ, IL-15, and CXCL9 in the serum of infected animals was measured at 0, 3, and 7 dpi by Luminex assay. Data of (C) are shown as mean ± SD from three experimental replicates, *p ≤ 0.05, **p ≤ 0.01, unpaired Student’s t test. See also Figure S6.

Figure 6. 25HC Inhibits ZIKV Infection in Human Cortical Organoids

Human cortical organoids were differentiated from hES. On day 20, these organoids were inoculated with ZIKV (PRVABC59/2015 strain, MOI 1). (A–C) Organoids were inoculated with ZIKV for indicated time, and expression of ZIKV genomic RNA (A), IFNB (B), and CH25H (C) was quantified by qRT-PCR. (D–F) Human cortical organoids were pretreated with indicated dose of 25HC or EtOH for 15 hr and then infected with ZIKV for 48 hr. ZIKV genomic RNA and titer were quantified by (D) qRT-PCR or (E) plaque assay. (F) Left: ZIKV E protein in these organoids was stained by immunofluorescence assay. Right: ZIKV⁺ cells were also quantified. Green: ZIKV E protein; blue: HOECHST; red: CTIP2. Scale bars; left, 500 µm; right, 100 µm. Data of (A–E) are shown as mean ± SEM from three independent experiments, **p ≤ 0.01, ***p ≤ 0.001, unpaired Student’s t test. Data of (F) are representative of three independent experiments.

Figure 7. 25HC Protects the Embryonic Brains from ZIKV-Induced Microcephaly

Embryonic brains were injected with ZIKV (SZ01/2016, 650 PFU/brain) or medium at E13.5 and inspected at E18.5 with or without treatment with 25HC (50 mg/kg, i.p.) (A) Coronal sections were stained with ZIKV antiserum (green, left panel) and ZIKV⁺ cells were quantified (right panel). Virus+25HC: n = 9; Virus+Vehicle: n = 10. (B) ZIKV genomic RNA copies were measured by qRT-PCR, n = 3. (C) Similar positions of coronal sections were Nissl-stained, scale bars, 1mm. (D) Nissl staining was shown for the ZIKV-infected cortices with or without 25HC treatment (left). The thickness of different layers was measured (right), n = 20 for each group. MZ: marginal zone; CP: cortical plate; SP: sub-plate; IZ: intermediate zone; SVZ: sub-ventricle zone; VZ: ventricle zone. (E) Cortices were stained for Tbr1 (early born post-mitotic neuron marker, red) and NeuN (general post-mitotic neuron marker, white) (left). The thickness of the layers with individual markers was stained. Mock+Vehicle: n = 14 (Tbr1⁺), 8 (NeuN⁺); Mock+25HC: n = 15 (Tbr1⁺), 12 (NeuN⁺); Virus+Vehicle: n = 15 (Tbr1⁺), 11 (NeuN⁺); Virus+25HC: n = 12 (Tbr1⁺), 11 (NeuN⁺). (F) Cortices were stained with Phospho-Histone H3 (red, left). Relative P-H3⁺ cells in the cortex were quantified (right). (G) Cortices were stained with the activated form of caspase3 (red) and DAPI (blue) (left), caspase3⁺ cells were quantified (right). Data of (A), (B), and (D)–(G) are shown as means ± SEM from three independent experiments, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001, unpaired Student’s t test. Scale bars for (A) and (D)–(G): 100 µm.