Interferon-dependent immunity is essential for resistance to primary dengue virus infection in mice, whereas T- and B-cell-dependent immunity are less critical - PubMed (original) (raw)

Interferon-dependent immunity is essential for resistance to primary dengue virus infection in mice, whereas T- and B-cell-dependent immunity are less critical

Sujan Shresta et al. J Virol. 2004 Mar.

Abstract

Dengue virus (DEN) causes dengue fever and dengue hemorrhagic fever/dengue shock syndrome, which are major public health problems worldwide. The immune factors that control DEN infection or contribute to severe disease are neither well understood nor easy to examine in humans. In this study, we used wild-type and congenic mice lacking various components of the immune system to study the immune mechanisms in the response to DEN infection. Our results demonstrate that alpha/beta interferon (IFN-alpha/beta) and IFN-gamma receptors have critical, nonoverlapping functions in resolving primary DEN infection. Furthermore, we show that IFN-alpha/beta receptor-mediated action limits initial DEN replication in extraneural sites and controls subsequent viral spread into the central nervous system (CNS). In contrast, IFN-gamma receptor-mediated responses seem to act at later stages of DEN disease by restricting viral replication in the periphery and eliminating virus from the CNS. Mice deficient in B, CD4(+) T, or CD8(+) T cells had no increased susceptibility to DEN; however, RAG mice (deficient in both B and T cells) were partially susceptible to DEN infection. In summary, (i) IFN-alpha/beta is critical for early immune responses to DEN infection, (ii) IFN-gamma-mediated immune responses are crucial for both early and late clearance of DEN infection in mice, and (iii) the IFN system plays a more important role than T- and B-cell-dependent immunity in resistance to primary DEN infection in mice.

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Figures

FIG. 1.

FIG. 1.

(A) Susceptibility of wild-type and IFN receptor-deficient mice to primary DEN2 infection. 129/Sv/Ev wild-type (WT129), IFN-α/β receptor−/− (A129), IFN-γ receptor−/− (G129), and IFN-α/β receptor−/− × IFN-γ receptor−/− (AG129) mice were inoculated via the tail vein with 108 PFU of DEN2 (PL046 strain). Mice were euthanized as soon as they developed paralysis, as per the guidelines of the Office of Laboratory Animal Care at UC Berkeley. Kaplan-Meier analysis was performed, and the log rank test yielded P values of <0.0001 for WT129 versus AG129 and 0.0171 for WT129 versus G129. The survival curves shown represent combined data from three to five separate experiments (n = number of mice per group). (B) Dose dependence of AG129 mice for DEN2 infection. Mice were intravenously injected with 105, 106, 107, or 108 PFU of DEN2 (PL046 strain), and their times of survival (see above) were recorded until day 30 p.i. Results from two to three different experiments were pooled (n = total number of mice per group) and plotted as Kaplan-Meier survival curves. All experiments shown were terminated at day 30 p.i.

FIG. 2.

FIG. 2.

Scatter plots of the titers of infectious DEN in the brains and spinal cords of paralytic AG129 mice. AG129 mice were infected with 108 PFU of DEN2 (PL046 strain), and the viral loads in the brain and spinal cord homogenates of 15 AG129 mice with paralysis were titrated by use of a direct plaque assay on BHK cells. Values are expressed as PFU per gram (tissue weight). Each symbol represents an individual mouse (▪, brain; ▴, spinal cord), the line indicates the mean, and n is the total number of mice. Paralytic mice from two independent experiments are represented, and the limit of detection of the assay is 10 PFU per gram (tissue weight).

FIG. 3.

FIG. 3.

Levels of infectious DEN2 in tissues of AG129 mice at day 3 and day 7 p.i. AG129 mice were inoculated with 108 PFU of DEN2 (PL046 strain), and viral titers in the spleen, lymph nodes, brain, and spinal cord at days 3 and 7 after infection were quantitated by a direct plaque assay of BHK cells. Results are expressed as PFU per gram (tissue weight) and are shown as the averages of results from two to three experiments ± standard deviations (n = 7 mice for day 3 and n = 9 mice for day 7). The limit of sensitivity of the plaque assay is 10 PFU per gram (tissue weight).

FIG. 4.

FIG. 4.

Susceptibility of mice deficient in IFN receptors to infection with DEN1. Groups of wild-type (WT129), IFN-α/β receptor−/− (A129), IFN-γ receptor−/− (G129), and IFN-α/β receptor−/− × IFN-γ receptor−/− (AG129) 129/Sv/Ev mice were infected intravenously with 4.4 × 104 PFU of DEN1 (Mochizuki strain). Mice were monitored daily for the development of paralysis until day 30 p.i. and were euthanized as soon as they exhibited paralysis. (A) Kaplan-Meier survival curves. Data from three to five separate experiments were pooled. A log rank test revealed significant differences between WT129 and AG129 mice (P < 0.0001) and between WT129 and G129 mice (P = 0.0073). (B) Levels of infectious virus in AG129 mice with paralysis. Brains and spinal cords were harvested from mice that were euthanized due to the onset of paralysis. Samples were homogenized and subjected to a direct plaque assay. Each symbol represents a mouse, and results for two different infections are shown. ▪, brain; ▴, spinal cord, —, mean; n, total number of mice.

FIG. 5.

FIG. 5.

Susceptibility of wild-type and T- and B-cell-deficient (RAG2−/−) mice in the 129/Sv/Ev background to primary DEN infection. Wild-type (WT129) and RAG2−/− (RAG129) mice were intravenously inoculated with 4.4 × 104 PFU of DEN1 (Mochizuki strain) (A) or 108 PFU of DEN2 (PL046 strain) (B). Mice were observed for paralysis on a daily basis until day 30 p.i. and were euthanized immediately after the onset of paralysis (see above). Data were combined from four or five independent experiments (n = total number of mice per group) and graphed as Kaplan-Meier survival curves. The log rank test revealed a significant difference between WT129 and RAG129 mice after DEN1 infection (P = 0.0002) (A), whereas no significant difference was observed between WT129 and RAG129 mice after DEN2 infection (P = 0.0548) (B).

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