In experiments on the intracerebral inoculation of herpes virus, type I, into 38 CBA mice the phagocytic activity of peritoneal exudate, cells, spontaneous migration of leukocytes and their response to phytohemagglutinin (PHA), the activity of key enzymes of gluconeogenesis, lipid peroxidation in liver tissue, as well as the level of glucose and glycosylated hemoglobin in the blood, were determined simultaneously with the histological study of the brain and the main internal organs of the animals, receiving thymalin treatment and not receiving it. As demonstrated in these experiments, the development of experimental infection was accompanied by the inhibition of the phagocytic activity of peritoneal macrophages and response of leukocytes to PHA, as well as metabolic shifts in liver tissue. Treatment with thymalin produced a combined immunomodulating and metabolic effect.