RESUMO
Real-time PCR of Amblyomma imitator tick egg masses obtained in Nuevo Leon State, Mexico, identified a Rickettsia species. Sequence analyses of 17-kD common antigen and outer membrane protein A and B gene fragments showed to it to be R. rickettsii, which suggested a potential new vector for this bacterium.
Assuntos
Insetos Vetores/microbiologia , Rickettsia rickettsii/isolamento & purificação , Febre Maculosa das Montanhas Rochosas/transmissão , Carrapatos/microbiologia , Animais , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/genética , Sequência de Bases , DNA Bacteriano/química , DNA Bacteriano/genética , Feminino , Humanos , Insetos Vetores/ultraestrutura , Masculino , México , Microscopia Eletrônica , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Rickettsia rickettsii/genética , Análise de Sequência de DNA , Carrapatos/ultraestruturaRESUMO
BACKGROUND: Tick modulation of host defenses facilitates both blood feeding and pathogen transmission. Several tick species deviate host T cell responses toward a Th2 cytokine profile. The majority of studies of modulation of T cell cytokine expression by ticks were performed with lymphocytes from infested mice stimulated in vitro with polyclonal T cell activators. Those reports did not examine tick modulation of antigen specific responses. We report use of a transgenic T cell receptor (TCR) adoptive transfer model reactive with influenza hemagglutinin peptide (110-120) to examine CD4+ T cell intracellular cytokine responses during infestation with the metastriate tick, Dermacentor andersoni, or exposure to salivary gland extracts. RESULTS: Infestation with pathogen-free D. andersoni nymphs or administration of an intradermal injection of female or male tick salivary gland extract induced significant increases of IL-4 transcripts in skin and draining lymph nodes of BALB/c mice as measured by quantitative real-time RT-PCR. Furthermore, IL-10 transcripts were significantly increased in skin while IL-2 and IFN-gamma transcripts were not significantly changed by tick feeding or intradermal injection of salivary gland proteins, suggesting a superimposed Th2 response. Infestation induced TCR transgenic CD4+ T cells to divide more frequently as measured by CFSE dilution, but more notably these CD4+ T cells also gained the capacity to express IL-4. Intracellular levels of IL-4 were significantly increased. A second infestation administered 14 days after a primary exposure to ticks resulted in partially reduced CFSE dilution with no change in IL-4 expression when compared to one exposure to ticks. Intradermal inoculation of salivary gland extracts from both male and female ticks also induced IL-4 expression. CONCLUSION: This is the first report of the influence of a metastriate tick on the cytokine profile of antigen specific CD4+ T cells. Blood feeding by D. andersoni pathogen-free nymphs or intradermal injection of salivary gland extracts programs influenza hemagglutinin influenza peptide specific TCR transgenic CD4+ T cells to express IL-4.