HSV-1 latent rabbits shed viral DNA into their saliva

Abstract

BackgroundRabbits latent with HSV-1 strain McKrae spontaneously shed infectious virus and viral DNA into their tears and develop recurrent herpetic-specific corneal lesions. The rabbit eye model has been used for many years to assess acute ocular infections and pathogenesis, antiviral efficacy, as well as latency, reactivation, and recurrent eye diseases. This study used real-time PCR to quantify HSV-1 DNA in the saliva and tears of rabbits latent with HSV-1 McKrae.MethodsNew Zealand white rabbits used were latent with HSV-1 strain McKrae and had no ocular or oral pathology. Scarified corneas were topically inoculated with HSV-1. Eye swabs and saliva were taken from post inoculation (PI) days 28 through 49 (22 consecutive days). Saliva samples were taken four times each day from each rabbit and the DNA extracted was pooled for each rabbit for each day; one swab was taken daily from each eye and DNA extracted. Real-time PCR was done on the purified DNA samples for quantification of HSV-1 DNA copy numbers. Data are presented as copy numbers for each individual sample, plus all the copy numbers designated as positive, for comparison between left eye (OS), right eye (OD), and saliva.ResultsThe saliva and tears were taken from 9 rabbits and from 18 eyes and all tested positive at least once. Saliva was positive for HSV-1 DNA at 43.4% (86/198) and tears were positive at 28.0% (111/396). The saliva positives had 48 episodes and the tears had 75 episodes. The mean copy numbers ± the SEM for HSV-1 DNA in saliva were 3773 ± 2019 and 2294 ± 869 for tears (no statistical difference).ConclusionRabbits latent with strain McKrae shed HSV-1 DNA into their saliva and tears. HSV-1 DNA shedding into the saliva was similar to humans. This is the first evidence that documents HSV-1 DNA in the saliva of latent rabbits.

Therapeutic Immunization with a Mixture of Herpes Simplex Virus 1 Glycoprotein D-Derived “Asymptomatic” Human CD8 + T-Cell Epitopes Decreases Spontaneous Ocular Shedding in Latently Infected HLA Transgenic Rabbits: Association with Low Frequency of Local PD-1 + TIM-3 + CD8 + Exhausted T Cells

“…Direct ocular infection of rabbits results in 100% of surviving animals developing latency in the ophthalmic branches of both TG with a high rate of spontaneous viral reaction (7,8,19). From a practical standpoint, rabbit corneas, conjunctivas, and TG are significantly larger than those of mice and offer plentiful amounts of tissues for phenotypic and functional characterization of HSV-specific T cells using individual tissues (21,22). In addition, compared to those in mice, the surfaces of the rabbit and human eyes are relatively immunologically isolated from systemic immune responses (47).…”

“…In contrast, spontaneous HSV-1 reactivations occur sporadically in latently infected rabbits, and reactivated infectious virus does return to the eye, can be detected in tear films, and can produce recurrent eye disease (7,8,19,21,22). Moreover, virus shedding occurs in latently infected rabbits at a rate similar to that in humans (ϳ10% of tears contain infectious virus) (7,8,19,21,22). Severe recurrent eye disease also occurs at a rate similar to that in humans.…”

“…Although HLA Tg mice can develop T-cell responses to human epitopes, unlike in humans, spontaneous HSV-1 reactivation either does not occur at all or occurs at very low levels (the so-called molecular reactivation) in mice (14). In contrast, spontaneous HSV-1 reactivations occur sporadically in latently infected rabbits, and reactivated infectious virus does return to the eye, can be detected in tear films, and can produce recurrent eye disease (7,8,19,21,22). Moreover, virus shedding occurs in latently infected rabbits at a rate similar to that in humans (ϳ10% of tears contain infectious virus) (7,8,19,21,22).…”

“…At the dose used (2 ϫ 10 5 PFU/eye) all surviving rabbits harbor latent virus in both TG with high spontaneous reactivation and shedding in tears of both eyes (7,8,19,21,22).…”

Herpes Simplex Virus 1 Infection of Tree Shrews Differs from That of Mice in the Severity of Acute Infection and Viral Transcription in the Peripheral Nervous System

“…Mouse and rabbit models have been used to characterize the HSV-1 infection, and guinea pigs have been favored for HSV-2 infection, at a pathological level, while in vitro tissue culture and primary cell culture models have been used to study molecular pathways of latency in more detail (2,41,42). Although we have learned a great deal from the mouse and rabbit models of human HSV-1 infection, there are many questions that could not be answered with these models.…”