Study of Biological Characteristics of Spotted Fever Group Rickettsial Genotypes RpA4, DnS14, and DnS28

The modern study of nonpathogenic rickettsiae assumes a search of the new methodological approaches for their detection and cultivation. Some species of spotted fever group (SFG) rickettsiae can’t be cultivated using traditional models (guinea pigs, hamsters, chicken embryos) (for example, R. peacockii ). Even cell culture cultivation has limited success. 1 So we have developed an alternative model for studying rickettsia using experimental modeling of the natural cycle of metamorphosis of infected ticks. Ticks ( Dermacentor nuttalli from Altai, D. silvarum from Central Kazakhstan, D. silvarum from Buryatiya), which are naturally infected with SFG rickettsiae, are used for cultivation and study of levels of transovarial (TOT) and transstadial (TST) transmission of rickettsiae in carriers. Feeding of pairs of ticks (female and male) was conducted on adult laboratory animals (white mice and guinea pigs). The descendants were contained in serial feedings-sheddings “larva-nymph-imago.” Suckling white mice were used for feeding larvae and nymphs. For definition of availability of rickettsiae in descendant samples, larvae (100 − 150 copies) and nymphs (20 − 50 copies) were investigated in IIFA with polyclonal antibodies individually, both in a hungry condition and after satiation. The study of antigenic structure of rickettsiae in experimental lines was conducted in IIFA with monoclonal antibodies. 2 Now, as a result of application of PCR and sequence analysis, with the help of the tick experimental model (TEM), the strains of rickettsiae concerned are genotypes RpA4, DnS14, DnS28. 3