In vitro and In vivo Susceptibility of Baboons (Papio sp.) to Infection with and Apparent Antibody Reactivity to Simian Betaretrovirus (SRV)

Despite the lack of confirmed reports of an exogenous Simian betaretrovirus (SRV) isolated from baboons (Papio sp.), reports of simian endogenous gammaretrovirus (SERV) in baboons with complete genomes suggest that such viruses may be potentially infectious. In addition, serologic tests have repeatedly demonstrated antibody reactivity to SRV in baboons from multiple colonies. These findings complicate the management and use of such animals for research. To provide further insight into this situation, we performed in vitro and in vivo studies to determine if baboons are or can be infected with SRV. In our initial experiment, we were not able to isolate SRV from 6 seropositive or sero-indeterminate baboons by coculturing their peripheral blood mononuclear cells (PBMC) with macaque PBMC or permissive cell lines. In a subsequent experiment, we found that baboon PBMC infected in vitro with high dose SRV were permissive to virus replication. To test in vivo infectibil- ity, groups of naive baboons were infused intravenously with either (i) the same SRV tissue culture virus stocks used for the in vitro studies, (ii) SRV antibody positive and PCR positive macaque blood, (iii) SRV antibody positive or indeterminate, but PCR negative baboon blood, or (iv) SRV antibody and PCR negative baboon blood. Sustained SRV infection, as defined by reproducible PCR detection and/or antibody seroconversion, was confirmed in 2 of 3 baboons receiving tissue culture virus but not in any recipients of transfused blood from seropositive macaques or baboons. In conclusion, the data indicate that even though baboon cells can be infected experimentally with high doses of tissue culture grown SRV, baboons that are repeatedly SRV antibody positive and PCR negative are unlikely to be infected with exogenous SRV and thus are unlikely to transmit a virus that would threaten the SPF status of captive baboon colonies.

631 Interaction of Genotype and Temperature on the Floral Initiation of Pelargonium ×domesticum

Pelargonium ×domesticum has great potential as a flowering potted plant. Low-temperature requirements for floral initiation create an obstacle for mass production, and precise temperature requirements for floral initiation vary among cultivars. Our objective was to determine optimum temperature for floral initiation of six cultivars: Dandy, Debutante, Empress, Enchantment, Imperial, and Rapture. Four complete experiments were conducted at 1-month intervals beginning Oct. 1998. In each experiment, 120 culture-virus-indexed rooted cuttings were obtained commercially and planted into 15-cm plastic pots. After 1 week, terminals were removed and plants were allowed to grow for an additional 3 weeks. Plants then were subjected to three floral initiation treatments at 12, 15, and 18° C for 4 weeks under 16-h photoperiods in growth chambers. A control group was initiated in the greenhouse. Following initiation treatments, all plants were finished under standard greenhouse conditions, supplemented with HID light. On flowering, plants were evaluated for time to anthesis, number and size of inflorescences, and overall plant quality. The 15° C treatment consistently produced the highest quality plants, while the 12° C treatment scored lowest with regard to flowering and overall quality. Differences among the cultivars were observed for time to anthesis. `Imperial' and `Rapture' flowered earliest, followed by `Enchantment' and `Empress', with `Dandy' and `Debutante' requiring the most time.

Lesions of Experimental Equine Morbillivirus Pneumonia in Horses

Laboratory examinations of equine morbillivirus included experimental reproductions of the disease caused by the virus by transmission of mixed lung and spleen taken from two field equine cases into two horses and by inoculating tissue culture virus into a further two horses. The most distinctive gross lesions of the diseases that developed in three of the horses was that of pulmonary edema characterized by gelatinous distension of subpleural lymphatics. Histologically, the lesions in the lungs were those of serofibrinous alveolar edema, alveolar macrophages, hemorrhage, thrombosis of capillaries, and syncytial cells. Clearly defined vascular lesions in three horses that became clinically affected within 8 days of inoculation of virus included intramural hemorrhage, edema, and necrosis and syncytial cells in the endothelium of pulmonary vessels (∼40-70 μm in diameter). Vascular lesions accompanied by parenchymal degeneration were also seen in the heart, kidney, brain, spleen, lymph node, and stomach. A fourth horse, which survived for 12 days, had detectable lesions only in the lungs, which were more chronic than those in the other three horses, a greater degree of cellular infiltration, and fewer well-defined vascular lesions. Sections stained by an indirect immunocytochemical method showed equine morbillivirus antigen was present in the vascular lesions and along alveolar walls. When endothelial cells were examined by electron microscope, cytoplasmic virus inclusion bodies containing filamentous structures were seen that reacted to an immunogold test to equine morbillivirus antigen. The presence of the syncytia in the small blood vessels in the lungs and other organs was interpreted as an important characteristic of the disease and consistent with a reaction to a morbillivirus.

Evidence of hantavirus in wild rodents in Northern Ireland

SummaryA survey of evidence of rodent hantavirus infection in County Down, Northern Ireland was carried out by using immunofluorescence to detect virus antigen and antibody. Antibodies to hantavirus (R22 strain of Seoul virus and Hantaan 76–118) were found in 11/51 (21·6%) brown rats (Rattus norvegicus), 1/31 (3·2%) field mice (Apodemus sylvaticus) and 17/59 (28·8%) house mice (Mus domesticus). Seven rodents had evidence of hantavirus antigen in lung tissues. Antibody positive animals were significantly more likely to be adults than juveniles (P= 0·04) but and there was no sex difference between antibody positive and negative animals. House mice were more likely to be antibody positive if captured inside farm outbuildings (P= 0·08). Attempts to culture virus from the rodent material were unsuccessful. This work demonstrates a substantial rodent reservoir for hantavirus in Northern Ireland.