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Establishment of HSV1 latency in immunodeficient mice facilitates efficient in vivo reactivation.

Ramakrishna C, Ferraioli A, Calle A, Nguyen TK, Openshaw H, Lundberg PS, Lomonte P, Cantin EM - PLoS Pathog. (2015)

Bottom Line: The establishment of latent infections in sensory neurons is a remarkably effective immune evasion strategy that accounts for the widespread dissemination of life long Herpes Simplex Virus type 1 (HSV1) infections in humans.An in-depth understanding of the mechanisms regulating the maintenance of latency and reactivation are essential for developing new approaches to block reactivation.Transfer of HSV1 memory but not OVA specific or naïve T cells prior to HS blocked IVR, revealing the utility of this powerful Rag latency model for studying immune mechanisms involved in control of reactivation.

View Article: PubMed Central - PubMed

Affiliation: Department of Virology, Beckman Research Institute of City of Hope; Duarte, California, United States of America.

ABSTRACT
The establishment of latent infections in sensory neurons is a remarkably effective immune evasion strategy that accounts for the widespread dissemination of life long Herpes Simplex Virus type 1 (HSV1) infections in humans. Periodic reactivation of latent virus results in asymptomatic shedding and transmission of HSV1 or recurrent disease that is usually mild but can be severe. An in-depth understanding of the mechanisms regulating the maintenance of latency and reactivation are essential for developing new approaches to block reactivation. However, the lack of a reliable mouse model that supports efficient in vivo reactivation (IVR) resulting in production of infectious HSV1 and/or disease has hampered progress. Since HSV1 reactivation is enhanced in immunosuppressed hosts, we exploited the antiviral and immunomodulatory activities of IVIG (intravenous immunoglobulins) to promote survival of latently infected immunodeficient Rag mice. Latently infected Rag mice derived by high dose (HD), but not low dose (LD), HSV1 inoculation exhibited spontaneous reactivation. Following hyperthermia stress (HS), the majority of HD inoculated mice developed HSV1 encephalitis (HSE) rapidly and synchronously, whereas for LD inoculated mice reactivated HSV1 persisted only transiently in trigeminal ganglia (Tg). T cells, but not B cells, were required to suppress spontaneous reactivation in HD inoculated latently infected mice. Transfer of HSV1 memory but not OVA specific or naïve T cells prior to HS blocked IVR, revealing the utility of this powerful Rag latency model for studying immune mechanisms involved in control of reactivation. Crossing Rag mice to various knockout strains and infecting them with wild type or mutant HSV1 strains is expected to provide novel insights into the role of specific cellular and viral genes in reactivation, thereby facilitating identification of new targets with the potential to block reactivation.

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IVIG protection of Rag mice is HSV1 dose dependent.(A) B6-Rag or (B) 129-Rag mice infected with HSV1 at 10x, 32x or 100x LD50 were treated with either PBS or 4 mg IVIG at 24 h pi and monitored for survival (n = 12–28 mice / treatment group). (C) 129-Rag mice infected with HSV1 at 100x LD50 were treated with PBS or IVIG (1x) at 24 h pi and given either a second dose of IVIG at day 12 pi (2x), or a 7-day course of ACV treatment beginning day 10 pi (blue line) or day 12 pi (red line); (2–4 experiments, n = 12–32 mice / group). (D) Mononuclear cells isolated from pooled BS of 4 mice treated with 1x IVIG (control) at day 12 pi, 1x IVIG + d12 ACV (d12 ACV) or 2x IVIG (d12 IVIG) at day 15 pi were analyzed for infiltrating cell subsets by flow cytometry. (E) HD infected B6-Rag or (F) 129-Rag mice were treated with IVIG at 24 h pi. After the first dose, some mice received 1 (1x), 2 (2x) or 3 (3x) additional doses of IVIG given every 12 days (n = 20–65 mice / group). (*p<0.05 **p<0.01, ***p<0.001, ****p<0.0001).
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ppat.1004730.g002: IVIG protection of Rag mice is HSV1 dose dependent.(A) B6-Rag or (B) 129-Rag mice infected with HSV1 at 10x, 32x or 100x LD50 were treated with either PBS or 4 mg IVIG at 24 h pi and monitored for survival (n = 12–28 mice / treatment group). (C) 129-Rag mice infected with HSV1 at 100x LD50 were treated with PBS or IVIG (1x) at 24 h pi and given either a second dose of IVIG at day 12 pi (2x), or a 7-day course of ACV treatment beginning day 10 pi (blue line) or day 12 pi (red line); (2–4 experiments, n = 12–32 mice / group). (D) Mononuclear cells isolated from pooled BS of 4 mice treated with 1x IVIG (control) at day 12 pi, 1x IVIG + d12 ACV (d12 ACV) or 2x IVIG (d12 IVIG) at day 15 pi were analyzed for infiltrating cell subsets by flow cytometry. (E) HD infected B6-Rag or (F) 129-Rag mice were treated with IVIG at 24 h pi. After the first dose, some mice received 1 (1x), 2 (2x) or 3 (3x) additional doses of IVIG given every 12 days (n = 20–65 mice / group). (*p<0.05 **p<0.01, ***p<0.001, ****p<0.0001).

Mentions: To account for differential IVIG protection of 129-Rag and B6-Rag mice, we examined the effect of varying the HSV1 inoculum dose. Having determined an LD50 of 30 and 100 PFU for 129-Rag and B6-Rag mice respectively, we treated Rag mice infected at 10x, 32x and 100x LD50 with PBS or IVIG at 24 h pi and monitored them for survival. A single dose of IVIG protected all B6-Rag mice inoculated at 10x and 32x LD50 but not 100x LD50 (Fig. 2A). Although, the majority of IVIG treated 129-Rag mice inoculated at 10x and 32x LD50 survived, protection was less robust than for B6-Rag mice as shown by the progressive decline in protection with inocula of 32x and 100x LD50 (Fig. 2B). All B6-Rag and 129-Rag mice inoculated at 100x LD50 succumbed despite treatment with IVIG (Fig. 2A and 2B). Virtually all B6-Rag and 129-Rag mice that survived HSV1 challenge of 10x and 32x LD50 (>90%) harbored latent infections in the Tg as revealed by reactivation of HSV1 in Tg explant cultures.


Establishment of HSV1 latency in immunodeficient mice facilitates efficient in vivo reactivation.

Ramakrishna C, Ferraioli A, Calle A, Nguyen TK, Openshaw H, Lundberg PS, Lomonte P, Cantin EM - PLoS Pathog. (2015)

IVIG protection of Rag mice is HSV1 dose dependent.(A) B6-Rag or (B) 129-Rag mice infected with HSV1 at 10x, 32x or 100x LD50 were treated with either PBS or 4 mg IVIG at 24 h pi and monitored for survival (n = 12–28 mice / treatment group). (C) 129-Rag mice infected with HSV1 at 100x LD50 were treated with PBS or IVIG (1x) at 24 h pi and given either a second dose of IVIG at day 12 pi (2x), or a 7-day course of ACV treatment beginning day 10 pi (blue line) or day 12 pi (red line); (2–4 experiments, n = 12–32 mice / group). (D) Mononuclear cells isolated from pooled BS of 4 mice treated with 1x IVIG (control) at day 12 pi, 1x IVIG + d12 ACV (d12 ACV) or 2x IVIG (d12 IVIG) at day 15 pi were analyzed for infiltrating cell subsets by flow cytometry. (E) HD infected B6-Rag or (F) 129-Rag mice were treated with IVIG at 24 h pi. After the first dose, some mice received 1 (1x), 2 (2x) or 3 (3x) additional doses of IVIG given every 12 days (n = 20–65 mice / group). (*p<0.05 **p<0.01, ***p<0.001, ****p<0.0001).
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ppat.1004730.g002: IVIG protection of Rag mice is HSV1 dose dependent.(A) B6-Rag or (B) 129-Rag mice infected with HSV1 at 10x, 32x or 100x LD50 were treated with either PBS or 4 mg IVIG at 24 h pi and monitored for survival (n = 12–28 mice / treatment group). (C) 129-Rag mice infected with HSV1 at 100x LD50 were treated with PBS or IVIG (1x) at 24 h pi and given either a second dose of IVIG at day 12 pi (2x), or a 7-day course of ACV treatment beginning day 10 pi (blue line) or day 12 pi (red line); (2–4 experiments, n = 12–32 mice / group). (D) Mononuclear cells isolated from pooled BS of 4 mice treated with 1x IVIG (control) at day 12 pi, 1x IVIG + d12 ACV (d12 ACV) or 2x IVIG (d12 IVIG) at day 15 pi were analyzed for infiltrating cell subsets by flow cytometry. (E) HD infected B6-Rag or (F) 129-Rag mice were treated with IVIG at 24 h pi. After the first dose, some mice received 1 (1x), 2 (2x) or 3 (3x) additional doses of IVIG given every 12 days (n = 20–65 mice / group). (*p<0.05 **p<0.01, ***p<0.001, ****p<0.0001).
Mentions: To account for differential IVIG protection of 129-Rag and B6-Rag mice, we examined the effect of varying the HSV1 inoculum dose. Having determined an LD50 of 30 and 100 PFU for 129-Rag and B6-Rag mice respectively, we treated Rag mice infected at 10x, 32x and 100x LD50 with PBS or IVIG at 24 h pi and monitored them for survival. A single dose of IVIG protected all B6-Rag mice inoculated at 10x and 32x LD50 but not 100x LD50 (Fig. 2A). Although, the majority of IVIG treated 129-Rag mice inoculated at 10x and 32x LD50 survived, protection was less robust than for B6-Rag mice as shown by the progressive decline in protection with inocula of 32x and 100x LD50 (Fig. 2B). All B6-Rag and 129-Rag mice inoculated at 100x LD50 succumbed despite treatment with IVIG (Fig. 2A and 2B). Virtually all B6-Rag and 129-Rag mice that survived HSV1 challenge of 10x and 32x LD50 (>90%) harbored latent infections in the Tg as revealed by reactivation of HSV1 in Tg explant cultures.

Bottom Line: The establishment of latent infections in sensory neurons is a remarkably effective immune evasion strategy that accounts for the widespread dissemination of life long Herpes Simplex Virus type 1 (HSV1) infections in humans.An in-depth understanding of the mechanisms regulating the maintenance of latency and reactivation are essential for developing new approaches to block reactivation.Transfer of HSV1 memory but not OVA specific or naïve T cells prior to HS blocked IVR, revealing the utility of this powerful Rag latency model for studying immune mechanisms involved in control of reactivation.

View Article: PubMed Central - PubMed

Affiliation: Department of Virology, Beckman Research Institute of City of Hope; Duarte, California, United States of America.

ABSTRACT
The establishment of latent infections in sensory neurons is a remarkably effective immune evasion strategy that accounts for the widespread dissemination of life long Herpes Simplex Virus type 1 (HSV1) infections in humans. Periodic reactivation of latent virus results in asymptomatic shedding and transmission of HSV1 or recurrent disease that is usually mild but can be severe. An in-depth understanding of the mechanisms regulating the maintenance of latency and reactivation are essential for developing new approaches to block reactivation. However, the lack of a reliable mouse model that supports efficient in vivo reactivation (IVR) resulting in production of infectious HSV1 and/or disease has hampered progress. Since HSV1 reactivation is enhanced in immunosuppressed hosts, we exploited the antiviral and immunomodulatory activities of IVIG (intravenous immunoglobulins) to promote survival of latently infected immunodeficient Rag mice. Latently infected Rag mice derived by high dose (HD), but not low dose (LD), HSV1 inoculation exhibited spontaneous reactivation. Following hyperthermia stress (HS), the majority of HD inoculated mice developed HSV1 encephalitis (HSE) rapidly and synchronously, whereas for LD inoculated mice reactivated HSV1 persisted only transiently in trigeminal ganglia (Tg). T cells, but not B cells, were required to suppress spontaneous reactivation in HD inoculated latently infected mice. Transfer of HSV1 memory but not OVA specific or naïve T cells prior to HS blocked IVR, revealing the utility of this powerful Rag latency model for studying immune mechanisms involved in control of reactivation. Crossing Rag mice to various knockout strains and infecting them with wild type or mutant HSV1 strains is expected to provide novel insights into the role of specific cellular and viral genes in reactivation, thereby facilitating identification of new targets with the potential to block reactivation.

Show MeSH
Related in: MedlinePlus