Localization of Dengue Virus in Nude Mice

Abstract

Dengue virus (DV) is known to replicate in the brain tissue of mice when injected intracerebrally. However, other organs and tissues do not easily support the replication of DV. We have reported that a highly mouse-adapted strain of DV caused acute lethal infection in mice even when injected intraperitoneally (ip), and that host responses to DV infection, i.e., antibody production and mononuclear cell infiltration in the infected brain, were different in athymic nude (nul nu) mice and in their heterozygous littermates (nu/+) (6). Viral replication was detected not only in the brain but also in other organs and tissues of both kinds of mice. In this paper we present additional data, particularly on the morphological aspects such as localization of DV in the infected mice.DV type 1, Mochizuki strain (7), in the form of the supernatant of suckling mouse brain homogenates, was used. Four to six-week-old male Balbjc-nu/nu and nul+ mice were procured from Japan Clea Co., Ltd. Each mouse was inoculated ip with 10 7 • 0 to 10 7 • 8 plaque-forming units (PFU) of DV. At fixed times thereafter, each mouse was bled and the organs were removed. The organs were then divided into two or more portions, which were used for virus titration and histological examination, including hematoxylin-eosin (HE), periodic acid-Schiff (PAS), and indirect fluorescent antibody (FA) stains as well as electron microscopic (EM) observation. Figure I shows the growth curve and concentration of virus in the brain, skeletal muscle and heart of infected nu/nu mice.The virus was first clearly detected 4 days after infection, increased in amount and reached maximum titers at the time paralysis appeared. In the paralyzed mice, the highest virus titers were found in the brain (ca. 10 8 PFUIg), and the second highest in the skeletal muscle and heart (ca. 10 4 PFUIg). Our previous findings that the virus concentration in the heart of nu/nu mice was higher than in nul+ mice (6) were repeatedly confirmed. Lymph node, lung, liver, spleen and kidney also contained virus, although the titers varied from one sample to another. In our previous experiments it was not certain whether the virus content in the lymph node and spleen were of the same level or not, but the present studies clearly indicate that the infected lymph node had a higher concentration of virus than the spleen (Fig. 2).

Enhancement of dengue virus type 2 replication in mouse macrophage cultures by bacterial cell walls, peptidoglycans, and a polymer of peptidoglycan subunits

“…Studies for the past several years have revealed that dengue virus multiplies in human peripheral blood monocytes (3,9,10,26), members of the mononuclear phagocyte system (32). In previous studies we noted that mononuclear phagocytes of athymic nude mice supported the multiplication of dengue virus (13,14). More recently, we have further shown that mouse peritoneal macrophage cultures treated with some activators, such as bacterial lipopolysaccharide and phytohemagglutinin, showed increased susceptibility to dengue virus infection and produced larger amounts of virus than did untreated control cultures (12).…”

Potential of ancestral sylvatic dengue-2 viruses to re-emerge

“…However, economic and animal facility limitations preclude widespread utility of nonhuman primates as a useful model for DENV replication. Several murine models (Boonpucknavig et al, 1981;Chaturvedi et al, 1991;Cole and Wisseman, 1969;Hotta et al, 1981) developed to evaluate protective immune responses, have proven to be ineffective due to the absence of DENV replication and illness or the requirement for murine-adapted DENV (Cole and Wisseman, 1969;Sabin, 1952). Human peripheral blood lymphocytes (hu-PBL) engrafted in SCID mice (Wu et al, 1995) infected with DENV produce high viremia and virus loads in the spleen and lymph nodes.…”

Pathobiology of the Flaviviruses

“…Although not extensively studied, the extraneural sites of replication of these viruses in the mouse appear similar to other flaviviruses and include lymph nodes, spleen, and cardiac and skeletal muscle (Hotta et al, 1981a,b;David-West, 1975). Dengueinfected nulnu and nul + mice develop infection (demonstrated by immunofluorescence) and acidophilic hyaline necrosis of Kupffer cells without evidence for progression to hepatocellular infection (Hotta et al, 1981b), and suckling mice infected with YF virus may show focal degeneration of liver cells (David-West and Smith, 1971); in these models, however, the brain is the eventual principal target organ for viral growth and pathogenesis. The only lower mammal that manifests a viscerotropic response to YF virus similar to monkeys and humans is the European hedgehog (Erinaceus europeaus) (Findlay and Clarke, 1934).…”