RESUMO
Antibodies are required to control blood-stage forms of African trypanosomes in humans and animals. Here, we report that intradermal infections by low numbers of African trypanosomes are controlled by innate resistance but prime the adaptive immune response to increase susceptibility to a subsequent challenge. Mice were found 100 times more resistant to intradermal infections by Trypanosoma congolense or Trypanosoma brucei than to intraperitoneal infections. B cell-deficient and RAG2(-/-) mice are as resistant as wild-type mice to intradermal infections, whereas inducible nitric oxide synthase (iNOS)(-/-) mice and wild-type mice treated with antibody to tumor necrosis factor (TNF) α are more susceptible. We conclude that primary intradermal infections with low numbers of parasites are controlled by innate defense mediated by induced nitric oxide (NO). CD1d(-/-) and major histocompatibility complex (MHC) class II(-/-) mice are more resistant than wild-type mice to primary intradermal infections. Trypanosome-specific spleen cells, as shown by cytokine production, are primed as early as 24 h after intradermal infection. Infecting mice intradermally with low numbers of parasites, or injecting them intradermally with a trypanosomal lysate, makes mice more susceptible to an intradermal challenge. We suggest that intradermal infections with low numbers of trypanosomes or injections with trypanosomal lysates prime the adaptive immune system to suppress protective immunity to an intradermal challenge.
Assuntos
Suscetibilidade a Doenças/imunologia , Imunidade Inata/fisiologia , Tripanossomíase Africana/imunologia , Animais , Anticorpos Antiprotozoários/sangue , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Feminino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Tripanossomíase Africana/parasitologiaRESUMO
Aeromonas hydrophila secretes a number of protein toxins across the outer membrane via the type II secretion system (T2SS). Assembly of the secretion channel ExeD secretin into the outer membrane is dependent on the peptidoglycan binding domain of ExeA. In this study, the peptidoglycan binding domain PF01471 family members were divided into a prokaryotic group and a eukaryotic group. By comparison of their sequence conservation profiles and their representative crystal structures, we found the prokaryotic members to have a highly conserved pocket(s) that is not present in the eukaryotic members. Substitution mutations of nine amino acids of the pocket were constructed in ExeA. Five of the substitution derivatives showed greatly decreased lipase secretion, accompanied by defects in secretin assembly. In addition, using in vivo cross-linking and in vitro cosedimentation assays, we showed that these mutations decreased ExeA-peptidoglycan interactions. These results suggest that the highly conserved pocket in ExeA is the binding site for its peptidoglycan ligand and identify residues critical for this binding.
Assuntos
Aeromonas hydrophila/metabolismo , Proteínas de Bactérias/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Peptidoglicano/metabolismo , Secretina/metabolismo , Aeromonas hydrophila/genética , Sequência de Aminoácidos , Substituição de Aminoácidos , Proteínas de Bactérias/genética , Sítios de Ligação , Lipase/metabolismo , Proteínas de Membrana Transportadoras/genética , Modelos Moleculares , Dados de Sequência Molecular , Ligação Proteica , Estrutura Terciária de Proteína , Secretina/genéticaRESUMO
Trypanosomes encode a family of proteins known as Major Surface Metalloproteases (MSPs). We have identified six putative MSPs encoded within the partially sequenced T. congolense genome. Phylogenic analysis indicates that T. congolense MSPs belong to five subfamilies that are conserved among African trypanosome species. Molecular modeling, based on the known structure of Leishmania Major GP63, reveals subfamily-specific structural variations around the putative active site despite conservation of overall structure, suggesting that each MSP subfamily has evolved to recognize distinct substrates. We have cloned and purified a protein encoding the amino-terminal domain of the T. congolense homologue TcoMSP-D (most closely related to Leishmania GP63). We detect TcoMSP-D in the serum of T. congolense-infected mice. Mice immunized with the amino-terminal domain of TcoMSP-D generate a persisting IgG1 antibody response. Surprisingly, a low-dose challenge of immunized mice with T. congolense significantly increases susceptibility to infection, indicating that immunity to TcoMSP-D is a factor affecting virulence.
Assuntos
Metaloproteases/fisiologia , Proteínas de Protozoários/fisiologia , Trypanosoma congolense/enzimologia , Sequência de Aminoácidos , Análise de Variância , Animais , Anticorpos Antiprotozoários/metabolismo , Antígenos de Protozoários/genética , Antígenos de Protozoários/imunologia , Antígenos de Protozoários/metabolismo , Modelos Animais de Doenças , Feminino , Imunoglobulina G/metabolismo , Metaloproteases/genética , Metaloproteases/imunologia , Metaloproteases/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Modelos Moleculares , Dados de Sequência Molecular , Filogenia , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Proteínas de Protozoários/metabolismo , Coelhos , Alinhamento de Sequência , Tripanossomíase AfricanaRESUMO
The sensitivity of delta red-gam delta ren mutants of bacteriophage lambda to Rex exclusion by lambda rexA+ rexB+ lysogens is modulated by the prophage cI repressor allele. We show the following: (i) lambda spi156 delta nin5 forms plaques on a cI+-rexA+-rexB+ lysogen with 10(5)-fold higher efficiency than on cI[Ts]-rexA+-rexB+ derivatives. (ii) The cI[Ts]857 allele augmentation of Rex exclusion is recessive to cI+. (iii) The cI857-mediated increase in Rex exclusion activity involves the participation of a genetic element mapping outside of cI-rexA-rexB.