Delayed type-hypersensitivity response of inbred strains of Syrian golden hamsters (Mesocricetus auratus) to lethal or non-lethal lymphocytic choriomeningitis virus (LCMV) infections

Implications of infectious agents on results of animal experiments

Report of the Working Group on Hygiene of the Gesellschaft für Versuchstierkunde–Society for Laboratory Animal Science (GV-SOLAS)

GV-SOLAS Working Group on Hygiene: Werner Nicklas (Chairman), Felix R. Homberger, Brunhilde Illgen-Wilcke, Karin Jacobi, Volker Kraft, Ivo Kunstyr, Michael Mähler, Herbert Meyer & Gabi Pohlmeyer-Esch

Environmental enrichment enhances delayed-type hypersensitivity in both short- and long-day Siberian hamsters

Darwinian fitness reflects trade-offs between reproduction and survival. Mechanisms have evolved in small nontropical mammals and birds to maximize reproductive output during the summer when thermoregulatory demands are relatively low and food is abundant and to shunt energy to processes that presumably increase the odds of survival during the winter when thermoregulatory demands are high and food is scarce. In order to predict the onset of winter, many seasonally-breeding mammals use day length (photoperiod) information. Seasonal adjustments of immune responses may be one mechanism to enhance survival; short days enhance cell-mediated immune function in seasonally-breeding rodents. The goal of the present study was to determine whether delayed-type hypersensitivity in hamsters is constrained or if photoperiod merely establishes a baseline level of immune response that can then be fined tuned by other environmental conditions. To test this, we used environmental enrichment, a manipulation that enhances many aspects of immune function. Hamsters were assigned to either long or short photoperiods and further assigned into either singly-housed or environmentally-enriched cages. After 10 weeks of concurrent photoperiod and housing treatment, delayed-type hypersensitivity (DTH) was induced. Although short days enhanced DTH responses compared with long days, environmental enrichment enhanced swelling responses in both short days and long days, suggesting that even during potential energetic bottlenecks or during maximal reproductive investment, hamsters can modulate their investment in immune function.

Short day lengths enhance skin immune responses in gonadectomised Siberian hamsters

In Siberian hamsters and other photoperiodic rodents, exposure to short photoperiods simultaneously inhibits gonadal hormone secretion and enhances some measures of immune function. The present study tested whether gonadal hormones mediate the effects of short days on skin immune function (delayed-type hypersensitivity reactions) in male Siberian hamsters. The magnitude of delayed-type hypersensitivity reactions was greater in hamsters exposed to short days relative to those in long days. Comparable effects of photoperiod were obtained in castrated hamsters bearing empty or testosterone-filled implants. The data suggest that contemporary gonadal hormone secretion is neither necessary, nor sufficient to mediate the effects of short photoperiods on skin immune function.

Photoperiod influences the effects of exercise and food restriction on an antigen-specific immune response in Siberian hamsters

Environmental conditions influence the onset and severity of illness and infection and may compromise survival. Energetically challenging conditions during winter may directly induce death through hypothermia, starvation, or shock. The ability to forecast and prepare for the arrival of challenging conditions associated with winter (e.g. low temperatures, decreased food) likely confers survival advantages. Siberian hamsters (Phodopus sungorus) stop reproduction and reduce body mass (approximately 25%) during short, winter-like day lengths, resulting in energetic savings. Hamsters also increase circulating glucocorticoids and lymphocytes (e.g. T cells, NK cells), and exhibit enhanced antigen-specific delayed-type-hypersensitivity (DTH) responses in the skin during short days (SDs). We tested the hypothesis that Siberian hamsters use SD lengths to signal the onset of winter to mediate the energetic trade-offs among body mass, reproductive function, and immune function. Long-day (LD; 16 h light, 8 h dark) and SD (8 h light, 16 h dark) hamsters were either food restricted (25%) or provided ad libitum (ad lib) food for 4 wk; half of all hamsters in each food condition had voluntary access to a running wheel, and half remained sedentary. SD hamsters enhanced DTH responses compared with LD hamsters under sedentary ad lib conditions. Exercise enhanced DTH in LD hamsters regardless of food intake. Furthermore, food-restriction did not significantly influence DTH in LD hamsters. In contrast, food-restriction suppressed DTH in SD hamsters regardless of activity condition, and exercise modestly enhanced DTH only in SD hamsters with ad lib access to food. In sum, moderate energetic deficiency suppressed DTH in SD (but not LD) hamsters, and this suggests that hamsters may have evolved to enhance immune responses during winter in preparation for increased metabolic stressors.

Parainfluenza virus type 3 (PIV3)-specific and non-virus-specific delayed type hypersensitivity responses in cotton rats given different PIV3 antigen preparations

Virus-specific, T-lymphocyte-mediated delayed type hypersensitivity (DTH) responses were studied in cotton rats using replicating (wild-type parainfluenza virus type 3 (PIV3) and recombinant vaccinia virus expressing PIV3 haemagglutinin-neuraminidase (HN) or fusion (F) glycoproteins), and non-replicating (detergent-solubilized, affinity chromatography purified HN and F glycoproteins or inactivated whole PIV3) virus preparations. Significant virus-specific DTH responses were observed in all test groups 1-2 weeks after a single antigen inoculation or 5 days after two inoculations given 3 weeks apart. Peak swelling of ear pinnas in these animals generally occurred 24 h after elicitation and was marked by a cellular infiltration consisting of mono- and polymorphonuclear leucocytes. A considerable non-virus-specific inflammatory response, presumably due to tissue culture or media components in the priming antigen preparations, was observed 3 weeks after priming. No significant differences in DTH responses were observed in cotton rats primed with any of the PIV3 preparations. The possible roles and significance of both the virus-specific and non-virus-specific DTH responses in paramyxovirus-induced disease in humans and cotton rats are discussed.