Coinfection with Borrelia burgdorferi and the agent of human granulocytic ehrlichiosis suppresses IL-2 and IFN gamma production and promotes an IL-4 response in C3H/HeJ mice

Natural Co-Exposure to Borrelia burgdorferi s.l. and Anaplasma phagocytophilum: Unraveling the Hematological Profile in Sheep

The occurrence of co-infected hosts and questing ticks with more than one tick-borne pathogen-as in the case of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato-is expected in endemic regions. Their synergy-in terms of pathogenesis and disease severity-has been suggested previously in humans. Limited data exist on the clinicopathological alterations in co-infected sheep. In this study, we investigated the impact of A. phagocytophilum and B. burgdorferi s.l. seropositivity, alone and in combination, on the hematological parameters of naturally infected sheep. A complete blood count was performed, and indirect immunofluorescence assays were used to detect IgG antibodies against A. phagocytophilum and IgG and IgM antibodies against B. burgdorferi s.l. Single natural exposure to B. burgdorferi s.l. was characterized by low Packed Cell Volume (PCV) values and platelet (PLT) counts, while single exposure to A. phagocytophilum was characterized by low PCV values, low white blood cell (WBC) counts, and an increased risk for leukopenia and neutropenia. Co-exposure resulted in the most severe blood abnormalities; all the blood parameters decreased, and the sheep presented an increased risk for anemia. Our study showed that natural co-exposure to A. phagocytophilum and B. burgdorferi s.l. in sheep leads to more severe blood abnormalities and enhances the pathogenic processes. More studies are needed to clarify the possible background mechanisms.

Transmission Cycle of Tick-Borne Infections and Co-Infections, Animal Models and Diseases

Tick-borne pathogens such as species of Borrelia, Babesia, Anaplasma, Rickettsia, and Ehrlichia are widespread in the United States and Europe among wildlife, in passerines as well as in domestic and farm animals. Transmission of these pathogens occurs by infected ticks during their blood meal, carnivorism, and through animal bites in wildlife, whereas humans can become infected either by an infected tick bite, through blood transfusion and in some cases, congenitally. The reservoir hosts play an important role in maintaining pathogens in nature and facilitate transmission of individual pathogens or of multiple pathogens simultaneously to humans through ticks. Tick-borne co-infections were first reported in the 1980s in white-footed mice, the most prominent reservoir host for causative organisms in the United States, and they are becoming a major concern for public health now. Various animal infection models have been used extensively to better understand pathogenesis of tick-borne pathogens and to reveal the interaction among pathogens co-existing in the same host. In this review, we focus on the prevalence of these pathogens in different reservoir hosts, animal models used to investigate their pathogenesis and host responses they trigger to understand diseases in humans. We also documented the prevalence of these pathogens as correlating with the infected ticks’ surveillance studies. The association of tick-borne co-infections with other topics such as pathogens virulence factors, host immune responses as they relate to diseases severity, identification of vaccine candidates, and disease economic impact are also briefly addressed here.

Update on mosquito bite reaction: Itch and hypersensitivity, pathophysiology, prevention, and treatment

Mosquito bites are endured by most populations worldwide. Reactions to mosquito bites range from localized wheals and papules with associated pruritus to rare systemic reactions and anaphylaxis in certain populations. The mechanism of itch is due to introduction of mosquito saliva components into the cutaneous tissue, although the exact pathophysiology is unclear. Histamine is thought to be a key player through mosquito saliva itself or through activation of mast cells by IgE or through an IgE-independent pathway. However, other salivary proteins such as tryptase and leukotrienes may induce non-histaminergic itch. Some individuals have a genetic predisposition for mosquito bites, and people with hematologic cancers, HIV, and other conditions are susceptible to robust reactions. Prevention of mosquito bites is key with physical barriers or chemical repellents. Treatment consists of second-generation antihistamines and topical corticosteroids. Further research on topical treatments that target neural-mediated itch is needed.

Induced Transient Immune Tolerance in Ticks and Vertebrate Host: A Keystone of Tick-Borne Diseases?

Ticks and tick transmitted infectious agents are increasing global public health threats due to increasing abundance, expanding geographic ranges of vectors and pathogens, and emerging tick-borne infectious agents. Greater understanding of tick, host, and pathogen interactions will contribute to development of novel tick control and disease prevention strategies. Tick-borne pathogens adapt in multiple ways to very different tick and vertebrate host environments and defenses. Ticks effectively pharmacomodulate by its saliva host innate and adaptive immune defenses. In this review, we examine the idea that successful synergy between tick and tick-borne pathogen results in host immune tolerance that facilitates successful tick infection and feeding, creates a favorable site for pathogen introduction, modulates cutaneous and systemic immune defenses to establish infection, and contributes to successful long-term infection. Tick, host, and pathogen elements examined here include interaction of tick innate immunity and microbiome with tick-borne pathogens; tick modulation of host cutaneous defenses prior to pathogen transmission; how tick and pathogen target vertebrate host defenses that lead to different modes of interaction and host infection status (reservoir, incompetent, resistant, clinically ill); tick saliva bioactive molecules as important factors in determining those pathogens for which the tick is a competent vector; and, the need for translational studies to advance this field of study. Gaps in our understanding of these relationships are identified, that if successfully addressed, can advance the development of strategies to successfully disrupt both tick feeding and pathogen transmission.

Utility of Borrelia burgdorferi sensu stricto C6 Peptide for Serologic Confirmation of Erythema-Free Ixodid Tick-Borne Borrelioses in Russia

We evaluated the utility of Borrelia burgdorferi sensu stricto (Bb) peptide C6 for serologic confirmation of Ixodid Tick-Borne Borrelioses (ITBB) in Russia. Serum samples (N = 1089) were from erythema migrans (EM) (N = 327) and the EM-free (EMF) patients (N = 115); in some patients, the disease was accompanied by human granulocytic anaplasmosis or tick-borne encephalitis. The sera were investigated by multiplex phosphorescence analysis (PHOSPHAN) for IgM to Bb C6, recombinant OspC and VlsE proteins, and IgG to C6 from Bb, B. garinii (Bg), and B. afzelii (Ba). Detection of Bb C6 IgM/IgG provided effective serologic confirmation of ITBB in both EM and EMF patients early after disease onset. In the EM-free patients, however, this test needed to be supplemented with detection of VlsE IgM in convalescent-phase sera due to delay in development of the antibody responses for C6 IgG. In general, positive PHOSPHAN reactions were observed in 81.9% and 86.7% of the EM and EMF patients, respectively, as well as in 59 of 65 (90.8%) patients, whose blood contained B. burgdorferi sensu lato DNA. Additional detection of IgG to Bg C6 or Ba C6 had no significant contribution to serologic diagnosis of ITBB in both patient groups.

Evaluation of NF-κB concentration in patients with tick-borne encephalitis, neuroborreliosis, anaplasmosis and Anaplasma phagocythophilum with tick-borne encephalitis virus co-infection

OBJECTIVES

The aim of the study was the evaluation of NF-κB concentration in serum and cerebrospinal fluid (CSF) of patients with diagnosis of tick-borne diseases: tick-borne encephalitis (TBE), neuroborreliosis (NB), anaplasmosis (ANA) and patients co-infected with tick-borne encephalitis virus and Anaplasma phagocythophilum (TBE+ANA). Additionally NF-κB concentration during acute and convalescent period was compared.

METHODS

Sixty-seven patients with diagnosis of tick-borne diseases were included in the study. The control group (CG) consisted of 18 patients hospitalized because of headaches and had lumbar puncture performed. The NF-κB was measured by human inhibitory subunit of NF-κB ELISA Kit during acute and convalescent period.

RESULTS

In serum the significant differences were observed only in patients with TBE+ANA co-infection. In CSF the concentration of NF-κB was significantly higher in patients with TBE, TBE+ANA co-infection, and patients with NB than in CG. Receiver operating characteristic (ROC) curves analysis showed that NF-κB concentration in CSF differentiated patients with NB with CG; patients co-infected with TBE and ANA with CG and patients with TBE with CG. NF-κB concentration in serum differentiated patients co-infected with TBE and ANA with NB and with ANA, with TBE and with CG. In TBE group the serum NF-κB concentration significantly decreased in convalescent period, while in NB and TBE groups significant CSF decrease of NF-κB concentration was observed.

CONCLUSIONS

Suppression of Long-Lived Humoral Immunity Following Borrelia burgdorferi Infection

Lyme Disease caused by infection with Borrelia burgdorferi is an emerging infectious disease and already by far the most common vector-borne disease in the U.S. Similar to many other infections, infection with B. burgdorferi results in strong antibody response induction, which can be used clinically as a diagnostic measure of prior exposure. However, clinical studies have shown a sometimes-precipitous decline of such antibodies shortly following antibiotic treatment, revealing a potential deficit in the host’s ability to induce and/or maintain long-term protective antibodies. This is further supported by reports of frequent repeat infections with B. burgdorferi in endemic areas. The mechanisms underlying such a lack of long-term humoral immunity, however, remain unknown. We show here that B. burgdorferi infected mice show a similar rapid disappearance of Borrelia-specific antibodies after infection and subsequent antibiotic treatment. This failure was associated with development of only short-lived germinal centers, micro-anatomical locations from which long-lived immunity originates. These showed structural abnormalities and failed to induce memory B cells and long-lived plasma cells for months after the infection, rendering the mice susceptible to reinfection with the same strain of B. burgdorferi. The inability to induce long-lived immune responses was not due to the particular nature of the immunogenic antigens of B. burgdorferi, as antibodies to both T-dependent and T-independent Borrelia antigens lacked longevity and B cell memory induction. Furthermore, influenza immunization administered at the time of Borrelia infection also failed to induce robust antibody responses, dramatically reducing the protective antiviral capacity of the humoral response. Collectively, these studies show that B. burgdorferi-infection results in targeted and temporary immunosuppression of the host and bring new insight into the mechanisms underlying the failure to develop long-term immunity to this emerging disease threat.

Infections with the Lyme Disease agent, Borrelia burgdorferi, often fail to generate long-term protective immunity. We show here that this is because the immune system of the Borrelia-infected host generates only short-lived, structurally abnormal and non-functional germinal centers. These germinal centers fail to induce memory B cells and long-lived antibody-producing plasma cells, leaving the host susceptible to reinfection with Bb. This inability to induce long-term immunity was not due to the nature of Borrelia antigens, as even T-dependent antigens of Borrelia were unable to induce such responses. Moreover, influenza vaccine antigens, when applied during Borrelia-infection, failed to induce strong antibody responses and immune-protection from influenza challenge. This data illustrate the potent, if temporal, immune suppression induced by Borrelia-infection. Collectively, the data reveal a new mechanism by which B. burgdorferi subverts the adaptive immune response.

Borrelia burgdorferi promotes the establishment of Babesia microti in the northeastern United States

Babesia microti and Borrelia burgdorferi, the respective causative agents of human babesiosis and Lyme disease, are maintained in their enzootic cycles by the blacklegged tick (Ixodes scapularis) and use the white-footed mouse (Peromyscus leucopus) as primary reservoir host. The geographic range of both pathogens has expanded in the United States, but the spread of babesiosis has lagged behind that of Lyme disease. Several studies have estimated the basic reproduction number (R₀) for B. microti to be below the threshold for persistence (<1), a finding that is inconsistent with the persistence and geographic expansion of this pathogen. We tested the hypothesis that host coinfection with B. burgdorferi increases the likelihood of B. microti transmission and establishment in new areas. We fed I. scapularis larva on P. leucopus mice that had been infected in the laboratory with B. microti and/or B. burgdorferi. We observed that coinfection in mice increases the frequency of B. microti infected ticks. To identify the ecological variables that would increase the probability of B. microti establishment in the field, we integrated our laboratory data with field data on tick burden and feeding activity in an R₀ model. Our model predicts that high prevalence of B. burgdorferi infected mice lowers the ecological threshold for B. microti establishment, especially at sites where larval burden on P. leucopus is lower and where larvae feed simultaneously or soon after nymphs infect mice, when most of the transmission enhancement due to coinfection occurs. Our studies suggest that B. burgdorferi contributes to the emergence and expansion of B. microti and provides a model to predict the ecological factors that are sufficient for emergence of B. microti in the wild.

Ectoparasitic Syndemics: Polymicrobial Tick-borne Disease Interactions in a Changing Anthropogenic Landscape

Based on an assessment of the available research, this article uses syndemic theory to suggest the role of adverse bio-social interactions in increasing the total disease burden of tick-borne infections in local populations. Given the worldwide distribution of ticks, capacity for coinfection, the anthropogenic role in environmental changes that facilitate tick dissemination and contact, evidence of syndemic interaction in tick-borne diseases, and growing impact of ticks on global health, tick-borne syndemics reveal fundamental ways in which human beings are not simply agents of environmental change but objects of that change as well.

Lyme disease: point/counterpoint

Lyme disease represents a growing public health threat. The controversial science and politics of Lyme disease have created barriers to reliable diagnosis and effective treatment of this protean illness. Two major clinical hurdles are the absence of a therapeutic end point in treating Borrelia burgdorferi, the spirochetal agent of Lyme disease, and the presence of tickborne coinfections with organisms such as Babesia, Anaplasma, Ehrlichia and Bartonella that may complicate the course of the disease. From a pathophysiologic standpoint, the affinity of Borrelia burgdorferi for multiple cell types and the presence of nonreplicating forms of the Lyme disease spirochete have contributed to persistent infection and failure of simple antibiotic regimens. Newer approaches to the treatment of Lyme disease should take into account its clinical complexity in coinfected patients and the possible need for prolonged combination therapy in patients with persistent symptoms of this potentially debilitating illness. The optimal antibiotic regimen for chronic Lyme disease remains to be determined.

Prevalence of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), and Babesia microti (Piroplasmida: Babesiidae) in Ixodes scapularis (Acari: Ixodidae) collected from recreational lands in the Hudson Valley Region, New York State

ABSTRACT Blacklegged ticks, Ixodes scapularis Say, were collected from 27 sites in eight New York State counties from 2003 to 2006 to determine the prevalence and distribution of tick-borne pathogens in public-use areas over a 4-yr period. In total, 11,204 I. scapularis (3,300 nymphs and 7,904 adults) were individually analyzed using polymerase chain reaction to detect the presence of Borrelia burgdorferi (causative agent of Lyme disease), Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila, causative agent of human granulocytic anaplasmosis), and Babesia microti (causative agent of human babesiosis). Overall prevalence of B. burgdorferi, A. phagocytophilum, and B. microti was 14.4, 6.5, and 2.7% in nymphs and 45.7, 12.3, and 2.5% in adult ticks, respectively. Rates varied geographically and temporally during the time period examined, and were related to measurements of tick density. Average rate ofpolymicrobial infection for nymphs and adults, respectively, was 1.5 and 8.5% overall, with 0.5 and 6.3% coinfection of B. burgdorferi and A. phagocytophilum, 1.0 and 1.5% B. burgdorferi and B. microti, and 0.05 and 0.6% A. phagocytophilum and B. microti. Thirty-three individual adult ticks from seven study sites in Westchester, Putnam, Dutchess, and Rockland counties tested positive for simultaneous infection with all three agents by multiplex polymerase chain reaction assay.

Complex interaction between proliferative kidney disease, water temperature and concurrent nematode infection in brown trout

Proliferative kidney disease (PKD) is a temperature-dependent disease caused by the myxozoan Tetracapsuloides bryosalmonae. It is an emerging threat to wild brown trout Salmo trutta fario populations in Switzerland. Here we examined (1) how PKD prevalence and pathology in young-of-the-year (YOY) brown trout relate to water temperature, (2) whether wild brown trout can completely recover from T. bryosalmonae-induced renal lesions and eliminate T. bryosalmonae over the winter months, and (3) whether this rate and/or extent of the recovery is influenced by concurrent infection. A longitudinal field study on a wild brown trout cohort was conducted over 16 mo. YOY and age 1+ fish were sampled from 7 different field sites with various temperature regimes, and monitored for infection with T. bryosalmonae and the nematode Raphidascaris acus. T. bryosamonae was detectable in brown trout YOY from all sampling sites, with similar renal pathology, independent of water temperature. During winter months, recovery was mainly influenced by the presence or absence of concurrent infection with R. acus larvae. While brown trout without R. acus regenerated completely, concurrently infected brown trout showed incomplete recovery, with chronic renal lesions and incomplete translocation of T. bryosalmonae from the renal interstitium into the tubular lumen. Water temperature seemed to influence complete excretion of T. bryosalmonae, with spores remaining in trout from summer-warm rivers, but absent in trout from summer-cool rivers. In the following summer months, we found PKD infections in 1+ brown trout from all investigated river sites. The pathological lesions indicated a re-infection rather than a proliferation of remaining T. bryosalmonae. However, disease prevalence in 1+ trout was lower than in YOY.

Para-clinico-pathological observations of insidious incidence of canine hepatozoonosis from a mongrel dog: a case report

A rare case of canine hepatozoonosis in a mongrel dog with para-clinico-pathological observations has been reported. The study included detailed haemato-biochemical changes at two stages, i.e. before treatment and after treatment with adopted therapy. Before therapy, blood picture revealed normocytic hypochromic anaemia and neutrophilic leucocytosis with variable counts of platelets. Thirty-seven percent of neutrophils were found infected with gametocytes of Hepatozoon canis. Following treatment, further decrease in haemoglobin value with a relative increase in lymphocyte count was seen. Biochemically, increase in alkaline phosphatase, blood urea nitrogen and creatinine levels along with hyperproteinemia was seen. The 14 days chemotherapy did not bring a respite for the dog and the level of parasitaemia was 33% after the treatment. The alkaline phosphatase and creatinine level further rose up following therapy with sulphadiazine and clindamycin. Continual study is required to explain the best possible therapeutic combination to deal H. canis.

Chronic Lyme Disease and Co-infections: Differential Diagnosis

In Lyme disease concurrent infections frequently occur. The clinical and pathological impact of co-infections was first recognized in the 1990th, i.e. approximately ten years after the discovery of Lyme disease. Their pathological synergism can exacerbate Lyme disease or induce similar disease manifestations. Co-infecting agents can be transmitted together with Borrelia burgdorferi by tick bite resulting in multiple infections but a fraction of co-infections occur independently of tick bite. Clinically relevant co-infections are caused by Bartonella species, Yersinia enterocolitica, Chlamydophila pneumoniae, Chlamydia trachomatis, and Mycoplasma pneumoniae. In contrast to the USA, human granulocytic anaplasmosis (HGA) and babesiosis are not of major importance in Europe. Infections caused by these pathogens in patients not infected by Borrelia burgdorferi can result in clinical symptoms similar to those occurring in Lyme disease. This applies particularly to infections caused by Bartonella henselae, Yersinia enterocolitica, and Mycoplasma pneumoniae. Chlamydia trachomatis primarily causes polyarthritis. Chlamydophila pneumoniae not only causes arthritis but also affects the nervous system and the heart, which renders the differential diagnosis difficult. The diagnosis is even more complex when co-infections occur in association with Lyme disease. Treatment recommendations are based on individual expert opinions. In antibiotic therapy, the use of third generation cephalosporins should only be considered in cases of Lyme disease. The same applies to carbapenems, which however are used occasionally in infections caused by Yersinia enterocolitica. For the remaining infections predominantly tetracyclines and macrolides are used. Quinolones are for alternative treatment, particularly gemifloxacin. For Bartonella henselae, Chlamydia trachomatis, and Chlamydophila pneumoniae the combination with rifampicin is recommended. Erythromycin is the drug of choice for Campylobacter jejuni.

Typical and atypical manifestations of Anaplasma phagocytophilum infection in dogs

Eighteen clinically ill dogs, naturally infected with Anaplasma phagocytophilum, were examined at a veterinary practice in Baxter, Minnesota. A clinical examination, complete blood cell count, enzyme- linked immunosorbent assay (ELISA) for A phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and Dirofilaria immitis antigen, and a polymerase chain reaction test for A phagocytophilum DNA were obtained for all dogs. Physical examination findings included fever, arthropathy, lymphadenopathy, epistaxis, acute gastritis, cervical hyperpathia, and central nervous system dysfunction. Complete blood cell count abnormalities included thrombocytopenia, morulae in neutrophils, anemia, leukopenia, eosinopenia, lymphopenia, and monocytosis. Seroreactivity to A phagocytophilum was found in 61%, B burgdorferi antibodies in 17%, and D immitis antigen in 5% of the dogs. Fever, arthropathy, neurologic dysfunction, and epistaxis are clinical syndromes that can be associated with A phagocytophilum infection. Treatment with doxycycline resulted in rapid resolution of clinical signs in all dogs.

Immunoregulation of bovine macrophages by factors in the salivary glands of Rhipicephalus microplus

Background

Alternative strategies are required to control the southern cattle tick, Rhipicephalus microplus, due to evolving resistance to commercially available acaricides. This invasive ectoparasite is a vector of economically important diseases of cattle such as bovine babesiosis and anaplasmosis. An understanding of the biological intricacies underlying vector-host-pathogen interactions is required to innovate sustainable tick management strategies that can ultimately mitigate the impact of animal and zoonotic tick-borne diseases. Tick saliva contains molecules evolved to impair host innate and adaptive immune responses, which facilitates blood feeding and pathogen transmission. Antigen presenting cells are central to the development of robust T cell responses including Th1 and Th2 determination. In this study we examined changes in co-stimulatory molecule expression and cytokine response of bovine macrophages exposed to salivary gland extracts (SGE) obtained from 2-3 day fed, pathogen-free adult R. microplus.

Methods

Peripheral blood-derived macrophages were treated for 1 hr with 1, 5, or 10 μg/mL of SGE followed by 1, 6, 24 hr of 1 μg/mL of lipopolysaccharide (LPS). Real-time PCR and cytokine ELISA were used to measure changes in co-stimulatory molecule expression and cytokine response.

Results

Changes were observed in co-stimulatory molecule expression of bovine macrophages in response to R. microplus SGE exposure. After 6 hrs, CD86, but not CD80, was preferentially up-regulated on bovine macrophages when treated with 1 μg/ml SGE and then LPS, but not SGE alone. At 24 hrs CD80, CD86, and CD69 expression was increased with LPS, but was inhibited by the addition of SGE. SGE also inhibited LPS induced upregulation of TNFα, IFNγ and IL-12 cytokines, but did not alter IL-4 or CD40 mRNA expression.

Conclusions

Molecules from the salivary glands of adult R. microplus showed bimodal concentration-, and time-dependent effects on differential up-regulation of CD86 in bovine macrophages activated by the TLR4-ligand, LPS. Up regulation of proinflammatory cytokines and IL-12, a Th1 promoting cytokine, were inhibited in a dose-dependent manner. The co-stimulatory molecules CD80, as well as the cell activation marker, CD69, were also suppressed in macrophages exposed to SGE. Continued investigation of the immunomodulatory factors will provide the knowledge base to research and develop therapeutic or prophylactic interventions targeting R. microplus-cattle interactions at the blood-feeding interface.

Clinical evidence for rapid transmission of Lyme disease following a tickbite

Lyme disease transmission to humans by Ixodes ticks is thought to require at least 36-48 h of tick attachment. We describe 3 cases in which transmission of Borrelia burgdorferi, the spirochetal agent of Lyme disease, appears to have occurred in less than 24 h based on the degree of tick engorgement, clinical signs of acute infection, and immunologic evidence of acute Lyme disease. Health care providers and individuals exposed to ticks should be aware that transmission of Lyme disease may occur more rapidly than animal models suggest. A diagnosis of Lyme disease should not be ruled out based on a short tick attachment time in a subject with clinical evidence of B. burgdorferi infection.

Spatial distribution of seroprevalence for Anaplasma phagocytophilum, Borrelia burgdorferi, Ehrlichia canis, and Dirofilaria immitis in dogs in Washington, Oregon, and California

BACKGROUND

In the US little spatially defined information regarding exposure to most vector-borne pathogens in dogs is available for the states of California (CA), Oregon (OR), and Washington (WA).

OBJECTIVES

The purpose of the present study was to evaluate the spatial distribution of seroprevalence for 4 vector-borne pathogens, Anaplasma phagocytophilum, Borrelia burgdorferi, Ehrlichia canis, and Dirofilaria immitis, across the 3 western coastal states of the contiguous United States that extend from the northern Mexican to the southern Canadian border.

METHODS

A convenience sample, targeting blood from 20 pet dogs per county across CA, OR, and WA, was evaluated using a canine point-of-care ELISA kit. Geographic coordinates of home zip code were displayed using a geographic information system. A total of 2431 dogs from CA, OR, and WA were tested.

RESULTS

The overall seroprevalence was highest for A. phagocytophilum (2.4%), followed by B. burgdorferi (1.2%), and E. canis (0.7%). The prevalence of infection with D. immitis was 0.7%. At the individual dog level, there was a significant association between seropositivity to B. burgdorferi and A. phagocytophilum (odds ratio=18.7, 95% confidence interval=6.8-47.1). For most positive results, prevalence tended to decrease with increasing latitude; thus, the highest rates of seropositivity occurred in CA, followed by OR, and then WA; one exception was seropositivity for B. burgdorferi, which was higher in WA (0.38%) than in OR (0.15%), but considerably lower than in CA (2.00%). In WA, dogs that tested positive for A. phagocytophilum, E. canis, and B. burgdorferi were in the southern Puget Sound area. For D. immitis, none of the dogs in WA was positive.

CONCLUSIONS

Seropositivity for vector-borne pathogens is broadly but patchily distributed in dogs in CA, OR, and WA.

Associations between coinfection prevalence of Borrelia lusitaniae, Anaplasma sp., and Rickettsia sp. in hard ticks feeding on reptile hosts

An increasing number of studies reveal that ticks and their hosts are infected with multiple pathogens, suggesting that coinfection might be frequent for both vectors and wild reservoir hosts. Whereas the examination of associations between coinfecting pathogen agents in natural host-vector-pathogen systems is a prerequisite for a better understanding of disease maintenance and transmission, the associations between pathogens within vectors or hosts are seldom explicitly examined. We examined the prevalence of pathogen agents and the patterns of associations between them under natural conditions, using a previously unexamined host-vector-pathogen system--green lizards Lacerta viridis, hard ticks Ixodes ricinus, and Borrelia, Anaplasma, and Rickettsia pathogens. We found that immature ticks infesting a temperate lizard species in Central Europe were infected with multiple pathogens. Considering I. ricinus nymphs and larvae, the prevalence of Anaplasma, Borrelia, and Rickettsia was 13.1% and 8.7%, 12.8% and 1.3%, and 4.5% and 2.7%, respectively. The patterns of pathogen prevalence and observed coinfection rates suggest that the risk of tick infection with one pathogen is not independent of other pathogens. Our results indicate that Anaplasma can play a role in suppressing the transmission of Borrelia to tick vectors. Overall, however, positive effects of Borrelia on Anaplasma seem to prevail as judged by higher-than-expected Borrelia-Anaplasma coinfection rates.

Lyme disease: the next decade

Although Lyme disease remains a controversial illness, recent events have created an unprecedented opportunity to make progress against this serious tick-borne infection. Evidence presented during the legally mandated review of the restrictive Lyme guidelines of the Infectious Diseases Society of America (IDSA) has confirmed the potential for persistent infection with the Lyme spirochete, Borrelia burgdorferi, as well as the complicating role of tick-borne coinfections such as Babesia, Anaplasma, Ehrlichia, and Bartonella species associated with failure of short-course antibiotic therapy. Furthermore, renewed interest in the role of cell wall-deficient (CWD) forms in chronic bacterial infection and progress in understanding the molecular mechanisms of biofilms has focused attention on these processes in chronic Lyme disease. Recognition of the importance of CWD forms and biofilms in persistent B. burgdorferi infection should stimulate pharmaceutical research into new antimicrobial agents that target these mechanisms of chronic infection with the Lyme spirochete. Concurrent clinical implementation of proteomic screening offers a chance to correct significant deficiencies in Lyme testing. Advances in these areas have the potential to revolutionize the diagnosis and treatment of Lyme disease in the coming decade.

Rhipicephalus microplus salivary gland molecules induce differential CD86 expression in murine macrophages

Background

Tick parasitism is a major impediment for cattle production in many parts of the world. The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an obligate hematophagous parasite of domestic and wild animals that serves as vector of infectious agents lethal to cattle. Tick saliva contains molecules evolved to modulate host innate and adaptive immune responses which facilitates blood feeding and pathogen transmission. Tick feeding promotes CD4 T cell polarization to a Th2 profile usually accompanied by down-regulation of Th1 cytokines through as yet undefined mechanisms. Co-stimulatory molecules on antigen presenting cells are central to development of T cell responses including Th1 and Th2 responses. Tick induced changes to antigen presenting cell signal transduction pathways are largely unknown. Here we document the ability of R. microplus salivary gland extracts (SGE) to effect differential CD86 expression.

Results

We examined changes in co-stimulatory molecule expression in murine RAW 264.7 cells in response to R. microplus SGE exposure in the presence of the toll-like receptor 4 (TLR4) ligand, LPS. After 24 hrs, CD86, but not CD80, was preferentially up-regulated on mouse macrophage RAW 264.7 cells when treated with SGE and then LPS, but not SGE alone. CD80 and CD40 expression was increased with LPS, but the addition of SGE did not alter expression. Higher concentrations of SGE were less effective at increasing CD86 RNA expression. The addition of mitogen or extracellular kinase (MEK) inhibitor, PD98059, significantly reduced the ability for SGE to induce CD86 expression, indicating activation of MEK is necessary for SGE induced up-regulation.

Conclusions

Molecules in SGE of R. microplus have a concentration-dependent effect on differential up-regulation of CD86 in a macrophage cell line activated by the TLR4 ligand, LPS. This CD86 up-regulation is at least partially dependent on the ERK1/2 pathway and may serve to promote Th2 polarization of the immune response.

Tick-borne agents in rodents, China, 2004-2006

Many rodent species may be involved in the enzootic maintenance of these agents.

A total of 705 rodents from 6 provinces and autonomous regions of mainland People’s Republic of China were tested by PCRs for tick-borne agents (Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, spotted fever group rickettsiae, and Francisella tularensis). Infection rates were 5.5%, 6.7%, 9.1% and 5.0%, respectively. Eighteen (2.6%) rodents of 10 species were positive for 2 or 3 agents. Sequence analysis of PCR products confirmed the presence and genotypes of detected agents. These findings demonstrate that these tick-borne agents cocirculate and that a variety of rodent species may be involved in their enzootic maintenance.

A novel sphingomyelinase-like enzyme in Ixodes scapularis tick saliva drives host CD4 T cells to express IL-4

Tick feeding modulates host immune responses. Tick-induced skewing of host CD4(+) T cells towards a Th2 cytokine profile facilitates transmission of tick-borne pathogens that would otherwise be neutralized by Th1 cytokines. Tick-derived factors that drive this Th2 response have not previously been characterized. In the current study, we examined an I. scapularis cDNA library prepared at 18-24 h of feeding and identified and expressed a tick gene with homology to Loxosceles spider venom proteins with sphingomyelinase activity. This I. scapularis sphingomyelinase-like (IsSMase) protein is a Mg(2+)-dependent, neutral (pH 7.4) form of sphingomyelinase. Significantly, in an in vivo TCR transgenic adoptive transfer assay IsSMase programmed host CD4(+) T cells to express the hallmark Th2 effector cytokine IL-4. IsSMase appears to directly programme host CD4 T cell IL-4 expression (as opposed to its metabolic by-products) because induced IL-4 expression was not altered when enzymatic activity was neutralized. TCR transgenic CD4 T cell proliferation (CFSE-dilution) was also significantly increased by IsSMase. Furthermore, a Th2 response is superimposed onto a virally primed Th1 response by IsSMase. Thus, IsSMase is the first identified tick molecule capable of programming host CD4(+) T cells to express IL-4.

Promoter analysis of macrophage- and tick cell-specific differentially expressed Ehrlichia chaffeensis p28-Omp genes

BACKGROUND

Ehrlichia chaffeensis is a rickettsial agent responsible for an emerging tick-borne illness, human monocytic ehrlichiosis. Recently, we reported that E. chaffeensis protein expression is influenced by macrophage and tick cell environments. We also demonstrated that host response differs considerably for macrophage and tick cell-derived bacteria with delayed clearance of the pathogen originating from tick cells.

RESULTS

In this study, we mapped differences in the promoter regions of two genes of p28-Omp locus, genes 14 and 19, whose expression is influenced by macrophage and tick cell environments. Primer extension and quantitative RT-PCR analysis were performed to map transcription start sites and to demonstrate that E. chaffeensis regulates transcription in a host cell-specific manner. Promoter regions of genes 14 and 19 were evaluated to map differences in gene expression and to locate RNA polymerase binding sites.

CONCLUSION

RNA analysis and promoter deletion analysis aided in identifying differences in transcription, DNA sequences that influenced promoter activity and RNA polymerase binding regions. This is the first description of a transcriptional machinery of E. chaffeensis. In the absence of available genetic manipulation systems, the promoter analysis described in this study can serve as a novel molecular tool for mapping the molecular basis for gene expression differences in E. chaffeensis and other related pathogens belonging to the Anaplasmataceae family.

Managing canine vector-borne diseases of zoonotic concern: part two

Despite recent achievements in scientific knowledge related to canine vector-borne diseases (CVBDs) of zoonotic concern, their management is still impaired by several neglected issues related to accurate diagnosis and effective treatment of both single and co-infections. A better understanding of the pathogenesis and the progression of clinical, hematological and biochemical abnormalities of CVBDs will be important in choosing appropriate diagnostic tests and in establishing the best strategies for treatment and control. Nonetheless, the diagnosis and control of zoonotic infections in clinically healthy dogs remain challenging. This review discusses the crucial aspects involved in the diagnosis, treatment, prevention and control of CVBDs of zoonotic concern.

Serological and molecular prevalence of Borrelia burgdorferi, Anaplasma phagocytophilum, and Ehrlichia species in dogs from Minnesota

A population of 731 naturally exposed pet dogs examined at a private practice in Baxter, Minnesota, an area endemic for Lyme disease and anaplasmosis, was tested by serological and molecular methods for evidence of exposure to or infection with selected vector-borne pathogens. Serum samples were tested by enzyme-linked immunosorbent assay (ELISA) for Anaplasma phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and for Dirofilaria immitis antigen. Blood samples from 273 dogs were also analyzed by polymerase chain reaction (PCR) for Anaplasma and Ehrlichia species DNA. Based on the owner history and the attending veterinarian's physical examination findings, dogs exhibiting illness compatible with anaplasmosis or borreliosis were considered clinical cases, and their results were compared to the healthy dog population. Antibodies to only A. phagocytophilum were detected in 217 (29%) dogs; to only B. burgdorferi, in 80 (11%) dogs; and seroreactivity to both organisms, in 188 (25%) dogs. Of 89 suspected cases of canine anaplasmosis or borreliosis, A. phagocytophilum or B. burgdorferi antibodies were detected in 22 dogs (25%) and 8 dogs (9%) respectively, whereas antibodies to both organisms were found in 38 dogs (43%). Ehrlichia canis antibodies and D. immitis antigen were each detected in 11 (1.5%) dogs. Anaplasma phagocytophilum DNA was amplified from 7 of 222 (3%) healthy dogs and 19 of 51 (37%) clinical cases. Seroreactivity to both A. phagocytophilum and B. burgdorferi was detected more frequently in suspected cases of anaplasmosis and/or borreliosis than seroreactivity to either organism alone. Based on PCR testing, A. phagocytophilum DNA was more prevalent in suspected cases of anaplasmosis or borreliosis than in healthy dogs from the same region.

Anaplasma phagocytophilum-Borrelia burgdorferi coinfection enhances chemokine, cytokine, and matrix metalloprotease expression by human brain microvascular endothelial cells

Borrelia burgdorferi and Anaplasma phagocytophilum coinfect and are transmitted by Ixodes species ticks. Clinical indicators suggest that A. phagocytophilum coinfection contributes to the severity, dissemination, and, possibly, sequelae of Lyme disease. Previous in vitro studies showed that spirochete penetration through human brain microvascular endothelial cells of the blood-brain barrier is facilitated by endothelial cell-derived matrix metalloproteases (MMPs). A. phagocytophilum-infected neutrophils continuously release MMPs and other vasoactive biomediators. We examined B. burgdorferi infection of brain microvascular barriers during A. phagocytophilum coinfection and showed that coinfection enhanced reductions in transendothelial electrical resistance and enhanced or synergistically increased production of MMPs (MMP-1, -3, -7, -8, and -9), cytokines (interleukin 6 [IL-6], IL-10, and tumor necrosis factor alpha), and chemokines (IL-8 and macrophage inflammatory protein 1alpha) known to affect vascular permeability and inflammatory responses.

Counterpoint: long-term antibiotic therapy improves persistent symptoms associated with lyme disease

BACKGROUND

Controversy exists regarding the diagnosis and treatment of Lyme disease. Patients with persistent symptoms after standard (2-4-week) antibiotic therapy for this tickborne illness have been denied further antibiotic treatment as a result of the perception that long-term infection with the Lyme spirochete, Borrelia burgdorferi, and associated tickborne pathogens is rare or nonexistent.

METHODS

I review the pathophysiology of B. burgdorferi infection and the peer-reviewed literature on diagnostic Lyme disease testing, standard treatment results, and coinfection with tickborne agents, such as Babesia, Anaplasma, Ehrlichia, and Bartonella species. I also examine uncontrolled and controlled trials of prolonged antibiotic therapy in patients with persistent symptoms of Lyme disease.

RESULTS

The complex "stealth" pathology of B. burgdorferi allows the spirochete to invade diverse tissues, elude the immune response, and establish long-term infection. Commercial testing for Lyme disease is highly specific but relatively insensitive, especially during the later stages of disease. Numerous studies have documented the failure of standard antibiotic therapy in patients with Lyme disease. Previous uncontrolled trials and recent placebo-controlled trials suggest that prolonged antibiotic therapy (duration, >4 weeks) may be beneficial for patients with persistent Lyme disease symptoms. Tickborne coinfections may increase the severity and duration of infection with B. burgdorferi.

CONCLUSIONS

Prolonged antibiotic therapy may be useful and justifiable in patients with persistent symptoms of Lyme disease and coinfection with tickborne agents.

Coinfections acquired from ixodes ticks

The pathogens that cause Lyme disease (LD), human anaplasmosis, and babesiosis can coexist in Ixodes ticks and cause human coinfections. Although the risk of human coinfection differs by geographic location, the true prevalence of coinfecting pathogens among Ixodes ticks remains largely unknown for the majority of geographic locations. The prevalence of dually infected Ixodes ticks appears highest among ticks from regions of North America and Europe where LD is endemic, with reported prevalences of < or =28%. In North America and Europe, the majority of tick-borne coinfections occur among humans with diagnosed LD. Humans coinfected with LD and babesiosis appear to have more intense, prolonged symptoms than those with LD alone. Coinfected persons can also manifest diverse, influenza-like symptoms, and abnormal laboratory test results are frequently observed. Coinfecting pathogens might alter the efficiency of transmission, cause cooperative or competitive pathogen interactions, and alter disease severity among hosts. No prospective studies to assess the immunologic effects of coinfection among humans have been conducted, but animal models demonstrate that certain coinfections can modulate the immune response. Clinicians should consider the likelihood of coinfection when pursuing laboratory testing or selecting therapy for patients with tick-borne illness.

Tick immunobiology

Ticks are of vast medical and veterinary public health importance due to direct damage caused by feeding and their roles in transmitting well known and emerging infectious agents. Ticks and tick-borne pathogens stimulate the immune system of the host. Those immune interactions are of importance in tick biology, pathogen transmission and control of ticks and tick-borne diseases. Both innate and specific acquired immune defenses are involved in the responses of vertebrate hosts to infestation. Ticks have evolved countermeasures to circumvent host immune defenses. This review addresses the immunobiology of the tick-host interface from the perspectives of the pharmacology of tick saliva; relationship of tick saliva to pathogen transmission; host immune responses to infestation; tick modulation of host immune defences; and genomic/proteomic strategies for studying tick salivary gland molecules.

The immunomodulatory factors of arthropod saliva and the potential for these factors to serve as vaccine targets to prevent pathogen transmission

In general, attempts to develop vaccines for pathogens transmitted by arthropods have met with little or no success. It has been widely observed that the saliva of arthropods that transmit disease enhances the infectivity of pathogens the arthropod transmits to the vertebrate host. Indeed, it has been observed that vaccinating against components of the saliva of arthropods or against antigens expressed in the gut of arthropods can protect the host from infection and decrease the viability of the arthropod. These results suggest that multi-subunit vaccines that target the pathogen itself as well as arthropod salivary gland components and arthropod gut antigens may be the most effective at controlling arthropod-borne pathogens as these vaccines would target several facets of the lifecycle of the pathogen. This review covers known immunomodulators in arthropod salivary glands, instances when arthropod saliva has been shown to enhance infection and a limited number of examples of antiarthropod vaccines, with emphasis on three arthropods: sandflies, mosquitoes and hard ticks.

Lyme disease: the quest for magic bullets

Lyme disease represents a growing public health threat. Recent molecular and genetic studies have confirmed that Borrelia burgdorferi, the spirochetal agent of Lyme disease, is one of the most complex bacteria known to man. Affinity for multiple cell types and the presence of non-replicating forms of B. burgdorferi have contributed to persistent infection and failure of simple antibiotic regimens. The controversial clinical science of Lyme disease has impeded reliable diagnosis and effective treatment of this protean illness. Two major clinical hurdles are the absence of a therapeutic endpoint in treating Lyme disease and the presence of tick-borne coinfections that may complicate the course of the illness. New strategies for the diagnosis, treatment and prevention of Lyme disease are urgently needed.

Coinfection with Anaplasma phagocytophilum alters Borrelia burgdorferi population distribution in C3H/HeN mice

Borrelia burgdorferi, the agent of Lyme disease, and Anaplasma phagocytophilum, the agent of human anaplasmosis, are both transmitted by Ixodes sp. ticks and may occasionally coinfect a host. The population distributions of tick-transmitted B. burgdorferi infection were assessed using quantitative PCR targeting the flaB gene of B. burgdorferi in the ear, heart base, quadriceps muscle, skin, and tibiotarsal joint tissue of C3H mice previously infected with A. phagocytophilum. Population distributions of Anaplasma infection were assessed by targeting the p44 gene. A. phagocytophilum in blood and serologic response to both agents were evaluated. Spirochete numbers were increased in the ears, heart base, and skin of coinfected mice, but Anaplasma numbers remained constant. Antibody response to A. phagocytophilum, but not B. burgdorferi, was decreased in coinfected mice. These results suggest that coinfection with A. phagocytophilum and B. burgdorferi modulates pathogen burden and host antibody responses. This may be explained by the ability of A. phagocytophilum to functionally impair neutrophils, important cells in the early defense against B. burgdorferi infection.

Sustained-release formulation of doxycycline hyclate for prophylaxis of tick bite infection in a murine model of Lyme borreliosis

The prophylactic potential of a single injection of sustained-release doxycycline hyclate (Atridox) was compared to that of a single oral dose of doxycycline hyclate in a murine model of Lyme borreliosis. Prophylaxis, as measured by the lack of cultivable spirochetes and demonstrable pathology, was noted for 43% of orally treated mice; in contrast, the sustained-release doxycycline hyclate completely protected mice from infection and resultant pathology.

Developing animal models for polymicrobial diseases

Although polymicrobial diseases are not a new concept for microbiologists, they are experiencing a resurgence of interest owing to the development of suitable animal models and new molecular techniques that allow these diseases to be studied effectively. This broad review provides an excellent introduction to this fascinating topic.

Examples are included of each type of polymicrobial disease and the animal models that are used to study these diseases are discussed. In many instances, schematics for the animal model are presented.

Viral co-infections including bovine viral diarrhoeal viruses, porcine reproductive and respiratory syndrome, mixed hepatitis virus infections and HIV co-infection with hepatitis virus are discussed, together with attempts to model these diseases in animals.

Viral and bacterial co-infections are reviewed with a special focus on otitis media and the rodent models that have been used to probe this important childhood illness.

Of the polybacterial diseases, periodontitis is one of the best understood and a clinically relevant rodent model is now available. This model, and the role of biofilm formation in periodontitis are examined.

Fungal infections of humans are often referred to as 'opportunistic' but in fact these infections are often fungal co-infections with viruses such as HIV and fungal mixed co-infections. The roles of these infections in disease and the rodent models used to study them are discussed.

Parasite co-infections are thought to have a role in the severity of malaria and the severity of Lyme arthritis. These diseases and attempts to model them are evaluated.

Finally, co-infections that are associated with virus-induced immunosuppression are discussed, together with their animal models.

Polymicrobial diseases involve two or more microorganisms that act synergistically, or in succession, to mediate complex disease processes. Although polymicrobial diseases in animals and humans can be caused by similar organisms, these diseases are often also caused by organisms from different kingdoms, genera, species, strains, substrains and even by phenotypic variants of a single species. Animal models are often required to understand the mechanisms of pathogenesis, and to develop therapies and prevention regimes. However, reproducing polymicrobial diseases of humans in animal hosts presents significant challenges.

The Lyme Wars: time to listen

Lyme disease represents a public health threat of major proportions. The murky science and acrimonious politics of Lyme disease have created barriers to reliable diagnosis and effective treatment of this protean illness. Two major clinical problems with the disease are the absence of a therapeutic end point in treating Borrelia burgdorferi, the spirochetal agent of Lyme disease, and the presence of tick-borne co-infections, such as babesiosis, anaplasmosis and bartonellosis, that may complicate the course of the illness. From a pathophysiological standpoint, the affinity of B. burgdorferi for multiple cell types and the presence of non-replicating forms of the spirochete have contributed to persistent infection and failure of simple antibiotic regimens. Newer approaches to the treatment of Lyme disease should take into account its clinical complexity in co-infected patients and the possible need for prolonged combination therapy in patients with persistent symptoms of this potentially debilitating illness. The risk and prevention of human transmission of Lyme disease merit further study.

Epidemiology and impact of coinfections acquired from Ixodes ticks

Ixodes scapularis and other ticks in the Ixodes ricinus complex may transmit multiple pathogens, but research on coinfections has been limited. Coinfections occur with varying frequency in ticks, but single infections are more common than dual infections. The proportion of I. scapularis or I. ricinus ticks coinfected with both Borrelia burgdorferi sensu lato and Anaplasma phagocytophila is generally low, ranging from < 1% to 6% in six geographic areas. A higher prevalence of tick coinfection (26%) has been reported in Westchester County, New York. Genetic variants of the human disease-causing strain of A. phagocytophila are present in some tick populations, and they may affect the risk of coinfection or clinical illness. The proportion of Ixodes ticks coinfected with B. burgdorferi and Babesia microti has ranged from 2% in New Jersey to 19% on Nantucket Island, Massachusetts. In humans, cross-sectional seroprevalence studies have found markers of dual infection in 9-26% of patients with a tick-borne infection, but such studies often fail to distinguish simultaneous coinfection from sequential infections. Several studies have prospectively assessed the occurrence of acute coinfection. Among patients with a confirmed tick-borne infection, coinfection rates as high as 39% have been reported. The most commonly recognized coinfection in most of the eastern United States is Lyme borreliosis (LB) and babesiosis, accounting for approximately 80% of coinfections. LB and human granulocytic ehrlichiosis coinfections are less common, occurring in 3-15% of patients with a tick-borne infection in Connecticut or Wisconsin. Studies of clinical outcomes suggest that patients with acute Babesia coinfection have more severe symptoms and a longer duration of illness than patients with LB alone, but the risk of spirochete dissemination is similar. Coinfections can modify the immune response and alter the severity of arthritis in animal models. Future coinfection research should focus on long-term clinical outcomes, the role of genetic variants, immunologic effects, and the potential role of Bartonella species as tick-borne pathogens.

Disease-specific diagnosis of coinfecting tickborne zoonoses: babesiosis, human granulocytic ehrlichiosis, and Lyme disease

To determine whether a unique group of clinical and laboratory manifestations characterize certain major deer tick-transmitted human pathogens in North America, we compared the symptoms, short-term complications, and laboratory test results of New England residents who became ill due to > or =1 of these pathogens. Patients completed a uniformly structured questionnaire and submitted blood samples for serologic and polymerase chain reaction (PCR) testing after developing symptoms of Lyme disease, human babesiosis, or human granulocytic ehrlichiosis (HGE). Complete blood count with thin blood smear, PCR, and immunoglobulin M antibody tests helped differentiate the acute manifestations of these diseases. Physicians should consider use of tests designed to diagnose babesiosis and HGE in patients with Lyme disease who experience a prolonged flulike illness that fails to respond to appropriate antiborrelial therapy.

Characterization of a novel salivary immunosuppressive protein from Ixodes ricinus ticks

In tick salivary glands, several genes are induced during the feeding process, leading to the expression of new proteins. These proteins are typically secreted in tick saliva and are potentially involved in the modulation of the host immune and hemostatic responses. In a previous study, the construction and the analysis of a subtractive library led to the identification of Ixodes ricinus immunosuppressor (Iris), a novel protein, differentially expressed in I. ricinus salivary glands during the blood meal. In the present study, the data strongly suggest that this protein is secreted by tick salivary glands into the saliva. In addition, Iris is also found to modulate T lymphocyte and macrophage responsiveness by inducing a Th2 type response and by inhibiting the production of pro-inflammatory cytokines. In conclusion, these results suggest that Iris is an immunosuppressor, which might play an important role in the modulation of host immune response.