Vaccination with‘concealed’antigens: myth or reality?

Cattle infested with the tick Boophilus microplus produce antibodies to intrinsic membrane glycoproteins of the tick, as well as to Bm86, a well characterized antigen from the tick gut. Several factors explain how cattle could produce antibody to such antigens, which one would expect to be 'concealed' from the host's immune system, during natural infestation. It has been shown that the carbohydrate determinants on many tick glycoproteins are cross-reactive immunologically and that the reaction of bovine antibodies with intrinsic membrane glycoprotein is at least partially blocked by low molecular weight carbohydrate. Further, antisera from cattle exposed to ticks react with a glycosylated, native Bm86 but not with a non-glycosylated, recombinant Bm86. Thus the reaction of concealed antigens with antibodies produced as a result of tick infestation appears to be due to a relatively non-specific reaction with carbohydrate determinants on tick glycoprotein. Evidence is also presented that antibodies directed against carbohydrate determinants of Bm86 are not protective. Care must therefore be exercised in interpreting the results of antibody reaction with glycoproteins in such complex organisms.     

广州地区犬染蜱季节消长规律调查

目的：调查广泛地区犬染蜱的季节消长规律。方法：体表检查法。结果：优势蜱种为血红扇头蜱，该蜱全年均有活动，高峰期在9月份。结论：广州地区血红扇头蜱的季节消长规律与华北地区有明显差异，应采取相关措施加强防制。     

Relationships between the Rhipicephalus sanguineus complex ecology and mediterranean spotted fever epidemiology in France

The authors examine the epidemiologic features of Meditteranean spotted fever in France in light of the bioecological pecularities of each of the three known member of the Rhipicephalus sanguineus tick group (R. sanguineus, R. turanicus, R. pusillus). The results show that R. sanguineus is the main vector. Certain aspects of this tick species are of interest: affinity for man, close contact with humans for a long periods, peak of tick population (preimaginal stages) at the same time as the peak of the disease. The largest populations of R. sanguineus are noted in the endemic zone of human rickettsiosis. The fact that immature stages are more prevalent during the hot season and these forms' ability to bite humans is important and may suggest a role for them in the epidemiology of the disease. The sporadic isolation of this species outside the endemic zone may explain the occurrence of isolated cases of the disease in these areas. We cannot currently exclude vector roles for the two other species, which can parasitize humans, though none of our data supports this hypothesis.     

Spatial and temporal variation in Rhipicephalus appendiculatus size in eastern Zambia

The size of Rhipicephalus appendiculatus collected at different altitudes in the Eastern Province of Zambia between February 1985 and May 1986 and between October 1994 and December 1996 showed distinct variation dependent on altitude and season. The ticks were smallest during the dry season and at the start of the rains, and specimens were larger as the rainy season progressed. Second-generation adults where on average smaller than first-generation ticks. At higher altitudes, where a one-generation-per-annum phenology dominates, ticks were larger than at intermediate altitudes, where two generations per year are common. Larger size, associated with increased survival, is also favoured in low-lying, drier areas. Selective mortality of smaller adult ticks in years with a delayed rainy season appears to play an important role in the variation in size between years.     

Hereford cattle immunized and protected against Boophilus microplus with soluble and membrane-associated antigens from the midgut of ticks

Hereford cattle were immunized with membranes and soluble components extracted from the midgut of Boophilus microplus. Membrane vaccines protected cattle (91%) against challenge with 3 x 20,000 larval ticks administered at intervals of 7 days. Vaccines made from soluble antigens did not protect cattle. Antibody levels measured by enzyme-linked immunosorbent assay (ELISA) related to the levels of protection induced by vaccination.     

Anti-interleukin-8 activity of tick salivary gland extracts

Interleukin-8 (IL-8) is one of many mammalian chemokines (chemotactic cytokines) that direct mammalian inflammatory and immune cells to sites of injury and infection. Chemokines are produced locally and act on leucocytes through selective receptors. The principal role of IL-8 is to control the movement and activity of neutrophils. To date, several tick species have been shown to modulate the production or activity of certain cytokines but none of these are chemokines. Using an IL-8 specific ELISA, we showed that salivary gland extracts (SGE) from several ixodid tick species (Dermacentor reticulatus, Amblyomma variegatum, Rhipicephalus appendiculatus, Haemaphysalis inermis and Ixodes ricinus) reduced the level of detectable IL-8. Analyses of fractionated SGE revealed one similar peak of activity for D. reticulatus, A. variegatum and R. appendiculatus; a second peak, observed for D. reticulatus and A. variegatum, differed between the two species. Using radiolabelled IL-8, SGE and peak activity fractions of D. reticulatus were shown to bind the chemokine, and to inhibit binding of IL-8 to its receptors on human granuolocytes enriched for neutrophils. The biological significance of these observations was demonstrated by the ability of SGE to inhibit IL-8 induced chemotaxis of human blood granulocytes. Future isolation and characterization of the active molecules will enable determination of their functional roles in bloodfeeding and effect on tick-borne pathogen transmission.     

Isolation on « VERO » cells of a Spotted Fever Group Rickettsia « Mortilli strain » from Rhipicephalus sanguineus

The isolation of a Spotted Fever Group (SFG) Rickettsia « Mortilli strain » from brown dog ticks Rhipicephalu.s sanguineus removed from dogs associated with a confirmed case of Boutonneuse Fever (BF) in a site of a Western Sicily is reported. The need is stressed for isolation and adaption on cell cultures of SFG rickettsial strains for analysis of antigenic structure employing modern methodology.Corresponding author     

Spotted Fever Group Rickettsioses in Israel, 2010–2019

In a multicenter, nationwide, retrospective study of patients hospitalized with spotted fever group rickettsiosis in Israel during 2010–2019, we identified 42 cases, of which 36 were autochthonous. The most prevalent species was the Rickettsia conorii Israeli tick typhus strain (n = 33, 79%); infection with this species necessitated intensive care for 52% of patients and was associated with a 30% fatality rate. A history of tick bite was rare, found for only 5% of patients; eschar was found in 12%; and leukocytosis was more common than leukopenia. Most (72%) patients resided along the Mediterranean shoreline. For 3 patients, a new Rickettsia variant was identified and had been acquired in eastern, mountainous parts of Israel. One patient had prolonged fever before admission and clinical signs resembling tickborne lymphadenopathy. Our findings suggest that a broad range of Rickettsia species cause spotted fever group rickettsiosis in Israel.     

The position of repetitive DNA sequence in the southern cattle tick genome permits chromosome identification

Fluorescent in-situ hybridization (FISH) using meiotic chromosome preparations and highly repetitive DNA from the southern cattle tick, Rhipicephalus microplus, was undertaken to investigate genome organization. Several classes of highly repetitive DNA elements were identified by screening a R. microplus bacterial artificial chromosome (BAC) library. A repeat unit of approximately 149 bp, RMR-1 was localized to the subtelomeric regions of R. microplus autosomes 1–6 and 8–10. A second repeat unit, RMR-2 was localized to the subtelomeric regions of all autosomes and the X chromosome. RMR-2 was composed of three distinct repeat populations, RMR-2a, RMR-2b and RMR-2c of 178, 177 and 216 bp in length, respectively. Localization of an rDNA probe identified a single nucleolar organizing region on one autosome. Using a combination of labeled probes, we developed a preliminary karyotype for R. microplus. We present evidence that R. microplus has holocentric chromosomes and explore the implications of these findings for tick chromosome biology and genomic research. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.