OBJECTIVE: Human adenovirus Ad-36 induces adiposity and lowers total serum cholesterol in chickens, mice and marmosets and Ad-36 antibodies are associated with human obesity. We examined the early effects of Ad-36 inoculation on plasma cholesterol levels in hamsters fed a hyperlipidemic diet. DESIGN: A total of 32 male Golden Syrian hamsters were divided into two equal weight-matched groups and intranasally inoculated with Ad-36 (INF: infected) or media (CON: control). In each group, the animals were fed either a purified diet (PF, n = 8) 40%en fat ± 194 mg cholesterol/1000 kcal or chow (C, n = 8) ad libitum. Animals were killed 5 weeks postinoculation. RESULTS: Nested PCR assay detected Ad-36 DNA in the lung, liver, visceral adipose tissue and skeletal muscle of the INF group, but not in the CON animals. Ad-36 antibodies were detected in the INF group only. For all animals, total plasma cholesterol (TC) was not significantly affected by Ad-36 treatment (203 ± 92 vs 193 ± 75 mg/dl, P = NS; INF vs CON, respectively). In 5 weeks, Ad-36 infection had no effect on TC concentration in hamsters fed chow (128 ± 39 vs 130 ± 27 mg/dl, INF-C vs CON-C, respectively) or those fed PF (269 ± 70 vs 256 ± 47 mg/dl, INF-P vs CON-P, respectively). However, lipoproteins isolated by density gradient ultracentrifugation showed a greater proportion of LDL cholesterol in INF animals, as compared to CON (28.4 ± 1.6% vs 16.4 ± 1.2%, P = 0.02), regardless of dietary treatment (INF-P vs CON-P: 27.3 ± 2.1 vs 15.7 ± 1.5%, P = 0.07; and INF-C vs CON-C: 29.4 ± 1.2 vs 17.0 ± 1.1%, P = 0.009). This shift appears to be from HDL cholesterol to the LDL fractions. CONCLUSION: These data suggest that in the hamster (a model resembling several aspects of human lipoprotein metabolism), Ad-36 infection may acutely affect the intravascular processing of lipoproteins resulting in a more atherogenic lipoprotein profile.