Studies of a "new" rickettsiosis "Astrakhan" spotted fever.

The acute febrile disease with characteristic rash seen in Astrakhan region and named as "viral exanthema of unknown etiology" was proved to be a spotted fever group rickettsiosis. Serological examination of humans from endemic areas by complement fixation test revealed antibodies to R. conorii, R. akari and strains Netsvetaev and AR-74 of R. sibirica in titres from 20 to 640 in sera from ill persons. Of 429 sera from healthy persons, 5.1% were serologically positive in a titre of 20-40. The presence of spotted fever group rickettsiae was detected in 8 of 104 Rhipicephalus sanguineus ticks removed from dogs and tested by haemocyte test with Gimenez staining and indirect immunofluorescence technique. Attempts at isolation of rickettsiae in guinea pigs and cell cultures resulted in appearance of specific spotted fever group rickettsiae antibodies in guinea pigs (4 of 8 samples examined were positive) and detection of rickettsiae by immunofluorescence technique in cell cultures (in 2 of 12 samples tested).

[Importance of T-lymphocytes in antibody production in experimental typhus infection]. / Znachenie T-limfotsitov v produktsii antitel pri éksperimental'noi sypnotifoznoi infektsii.

The study of antibody production in cotton rats infected with Rickettsia prowazekii B and TB has revealed that R. prowazekii antigens, inducing the production of antibodies determined in the complement fixation, indirect hemolysis, and passive hemagglutination tests, are T-independent. The study of the nonspecific reactivity of T-lymphocytes in cotton rats infected with R. prowazekii TB has indicated that in case of the prolonged persistence of the infective agent in the animals no secondary immune deficiency develops.

Thymus-independent antibody production to the antigen of Rickettsia prowazekii.

Antibody production has been studied in cotton B-rats and in CBA B-mice during immunization with chemical typhus vaccine (CTV) and during infection with Rickettsia prowazekii. Studies of the immune response to rickettsial antigen in T-deficient animals have shown a high immunogenicity of CTV and independence of antibody production on T-lymphocytes. Active antibody synthesis was also observed in B-rats and B-mice during Rickettsia prowazekii infection. The absence of T-lymphocyte dependence in experimental animals was tested by administration of sheep red blood cells (SRBC).

[Macrophage migration inhibition reaction in Marseilles fever]. / Reaktsiia tormozheniia migratsii makrofagov pri éksperimental'noi Marsel'skoi likhoradke.

Delayed type hypersensitivity (DTH) was studied in the macrophage migration inhibition test, antibody titers in the CFT and functional activity of spleen macrophages, obtained from guinea-pigs infected with R. conori, in cell cultures. No direct correlation between antibody synthesis and functional macrophage activity accompanied by the development of DTH was revealed. The most pronounced protective function of macrophages could be observed during the decrease of antibody titers and the extinction of DTH.

Differences in the susceptibility of mouse lines to the rickettsial pox agent.

A definite correlation between the susceptibility of spleen macrophage cultures derived from a highly susceptible mouse line (C57Bl/6) and a line with low susceptibility (DBA/2) and the susceptibility of these mouse lines to infection with Rickettsia acari was established. Intensive replication of the rickettsiae in cultures from highly susceptible animals caused marked disorders in cell metabolism and eventually death of the culture. Cell cultures derived from resistant mice gradually eliminated the rickettsiae by intracellular digestion; necrobiotic changes in them were insignificant.

[Intracellular development of Rickettsia]. / Vnutrikletochnoe razvitie Rikketsii.

Microcinematography, cytological and cytochemical studies revealed new features of D. sibericus, D. murinus, and R. tsutsugamushi biology, mainly a very active movement in the cell. In contrast to D. sibericus, development of D. murinus and R. tsutsugamushi in cells is characterized by severe irritation of the infected cells early in the infection, a greater speed of movement of rickettsiae and their active release from the affected cells, as well as the development of necrobiotic changes in the latter. The mitotic activity of the cells increased early in cultures infected with Cox. burneti, R. prowazeki, D. sibericus, and T. tsutsugamushi. Subsequently, cell nuclei shrink and different cytotic changes develop in various rickettsia. Studies on the metabolism of the affected cells revealed activation of nucleic metabolism and redox enzymes associated with mitochondria in the course of the first 3 days followed by a low activity in 5 postinfection days. The lysosomal apparatus of the cells underwent drastic changes and the activity of acid phosphatase increased markedly with further elevation in the permeability of lysosomal membranes.

Enzymatic activity of blood lymphocytes experimental tsutsugamushi fever in mice.

The influence of tsutsugamushi fever infection on the metabolism of blood lymphocytes of mice differing in susceptibility to Rickettsia tsutsugamushi and of rifampicine and tetracycline treatment was studied. In susceptible mice, the activity of oxidation-reduction processes in lymphocytes increased at 7--10 days of the disease and became normal upon recovery of the animals. In mice with low susceptibility this increase of the activity began and terminated much earlier, at 3--5 days. Treatment of the infection with antibiotics resulted in a rapid arrest of the disease and normalization of the lymphocyte activity. The relationship between susceptibility of the animals to R. tsutsugamushi and the activity of oxidation-reduction enzymes is discussed on the example of succinate dehydrogenase.

Cytological investigation of Rickettsia tsutsugamushi infection of mice with different allotypic susceptibility to the agent.

Cytological and cytochemical studies on Swiss and random-bred white mice susceptible to Rickettsia tsutsugamushi infection as well as resistant C57 Black 6 and CBA mice revealed a clear-cut relationship between the severity of infection and the pattern of macrophage reaction. In highly susceptible mice the fatal infection was accompanied by death of macrophages and necrotisation of the peritoneal exudate cells. The resistant mice showed no clinical signs but developed an intensive macrophage reaction, and the main mass of the inoculated rickettsiae died at the inoculation site, the macrophages remaining viable. Phagocytosis and digestion of rickettsiae were accompanied by markedly increased activities of hydrolytic and oxidizing-reducing enzymes.