Detection of the surface-exposed 18-kilodalton binding protein in Chlamydia trachomatis by immunogold staining.

Dot-blot analysis of Chlamydia trachomatis elementary bodies (EBs) with monospecific polyclonal antibodies demonstrated that the 18-kilodalton binding protein is surface exposed. Immunoelectron microscopy with whole serovar L2 EBs and ultrathin sections confirmed this finding. In addition, only the extracellular EBs and not the intracellular reticulate bodies were labeled with immunogold.     

Arrays of hemispheric surface projections on Chlamydia psittaci and Chlamydia trachomatis observed by scanning electron microscopy.

Scanning microscopy of two strains of Chlamydia psittaci and four strains of Chlamydia trachomatis representative of the wide diversity in origin and behavior of members of the genus revealed patches of regular arrays of hemispheric projections on the surfaces of elementary bodies of all six strains. These distinctive and perhaps unique surface structure are probably present in all populations of chlamydiae.     

Identification of surface-exposed components of MOMP of Chlamydia trachomatis serovar F

The identification of surface-exposed components of the major outer membrane protein (MOMP) of Chlamydia is critical for modeling its three-dimensional structure, as well as for understanding the role of MOMP in the pathogenesis of Chlamydia-related diseases. MOMP contains four variable domains (VDs). In this study, VDII and VDIV of Chlamydia trachomatis serovar F were proven to be surface-located by immuno-dot blot assay using monoclonal antibodies (MAbs). Two proteases, trypsin and endoproteinase Glu-C, were applied to digest the intact elementary body of serovar F under native conditions to reveal the surface-located amino acids. The resulting peptides were separated by SDS-PAGE and probed with MAbs against these VDs. N-terminal amino acid sequencing revealed: (1) The Glu-C cleavage sites were located within VDI (at Glu61) and VDIII (at Glu225); (2) the trypsin cleavage sites were found at Lys79 in VDI and at Lys224 in VDIII. The tryptic peptides were then isolated by HPLC and analyzed with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer and a quadrupole-orthogonal-TOF mass spectrometer coupled with a capillary liquid chromatograph. Masses and fragmentation patterns that correlated to the peptides cleaved from VDI and VDIII regions, and C-terminal peptides Ser333-Arg358 and Ser333-Lys350 were observed. This result demonstrated that these regions are surface-exposed. Data derived from comparison of nonreduced outer membrane complex proteolytic fragments with their reduced fractions revealed that Cys26, 29, 33, 116, 208, and 337 were involved in disulfide bonds, and Cys26 and 337, and 116 and 208 were paired. Based on these data, a new two-dimensional model is proposed.     

Detection of Chlamydia trachomatis by nucleic acid sandwich hybridization

Abstract Chromosomal DNA fragments from Chlamydia trachomatis serotype L2 were shotgun-cloned into pBR322. A C. trachomatis -specific clone was further subcloned to produce specific DNA reagents for the identification of C. trachomatis by nucleic acid sandwich hybridization. The chosen DNA reagents from serotype L2 also hybridized with all the other chlamydial serotypes tested, but not with the DNA from 41 unrelated organisms. The sensitivity of the sandwich hybridization test was 10⁶ DNA molecules. The applicability of the test for routine diagnostic use was demonstrated by a pilot study in which C. trachomatis was directly detected from genital specimens.     

Interaction between human polymorphonuclear leucocytes and Chlamydia trachomatis elementary bodies: electron microscopy and chemiluminescent response

Incubation of human polymorphonuclear leucocytes (HPMN) with highly purified Chlamydia trachomatis serotype L2/434/Bu elementary bodies (EB), in the presence and absence of specific antibody, resulted in a 10(3)-fold reduction of viable count after 24 h incubation. Electron microscopy observations indicated activation of the HPMN by the EB. Attachment of the EB to the HPMN cell membrane, formation of a cytoplasmic cup and EB-containing vacuoles were observed. In addition, two types of phagocytic vacuoles were observed after 30 min incubation; in one type, a single EB was tightly surrounded by the vacuolar membrane, while the other type was enlarged and held one or more intact EB or degenerated EB or both. A fuzzy coat was observed on EB located in the HPMN vacuoles only in the presence of specific antibody. Empty vacuoles containing degenerated EB were observed in the HPMN after 24 h incubation. HPMN exposed to EB of C. trachomatis produced a marked chemiluminescent response with a peak 14 times greater than the peak value of the control. A second stimulation with phorbol 12-myristate 13-acetate and zymosan was achieved. The chemiluminescent peak value in the presence of heat-treated EB (56 degrees C, 20 min) was 50% of that obtained in the presence of untreated EB. The significance of the chemiluminescent response in the killing mechanism of C. trachomatis EB by HPMN is discussed.     

Surface-exposed epitopes on the major outer-membrane protein of Chlamydia trachomatis defined with peptide antisera

The surface exposure of computer-predicted, linear B-cell epitopes on the major outer-membrane protein (MOMP) of Chlamydia trachomatis serovar B was assessed using antibodies raised against synthetic peptides in conjunction with immunogold transmission electron microscopy. Several of the chosen peptides elicited antibodies which reacted with both denatured and native MOMP. The majority of the exposed epitopes were found within the variable segments of MOMP. For each of the epitopes identified, the extent of their surface accessibility varied both among individual organisms and different developmental forms. Evidence for two distinct subspecies-specific epitopes within VS4 is presented.     

Demonstration of immune complexes on erythrocytes by scanning electron microscopy

If anti-sera are combined with native whole blood by an in-vitro technique, immunocomplexes are formed. They are fixed to erythrocytes and can be made visible by a scanning electron microscope on blood smears especially pretreated.     

Detection by multiplex polymerase chain reaction and typing of Chlamydia trachomatis isolates

Abstract The multiplex polymerase chain reaction (PCR) was applied for the detection of the Chlamydia trachomatis chromosome and plasmid. The multiplex PCR demonstrated a sensitivity of 0.8 fg of chlamydial DNA, corresponding to the detection of about 5 copies of the plasmid. Analysis of 195 genital specimens collected randomly from a female population, showed that the multiplex PCR is more sensitive and rapid than culturing for detecting Chlamydia trachomatis . Moreover, sequencing of the II variable domain of the ompl gene, directly from DNA of the clinical specimens, appears to be a simple and rapid method for determining serovar isolates.     

Detection of Chlamydia trachomatis in clinical specimens by nucleic acid spot hybridization

A nucleic acid spot hybridization assay was used to detect Chlamydia trachomatis DNA. The hybridization probes included DNA isolated from elementary bodies of lymphogranuloma venereum (LGV) strains and cloned fragments of both chromosomal and plasmid DNA. The sensitivity of the test was in the range 10 to 100 pg homologous DNA and 10 in vitro infected cells. Cross-reactivity with bacterial DNA was avoided when purified chlamydia-specific DNA fragments were used as probes. C. trachomatis was detectable in most of the clinical specimens with large amounts of infectious particles. Also some isolation-negative specimens gave a positive signal in the test.     

Identification of linear B‐cell epitopes within Tarp of Chlamydia trachomatis

Chlamydia trachomatis is one of the most prevalent sexually transmitted pathogens. There is currently no commercially available vaccine against C. trachomatis. Chlamydial translocated actin‐recruiting phosphoprotein (Tarp) can induce cellular and humoral immune responses in murine models and has been regarded as a potential vaccine candidate. In this report, the amino acid sequence of Tarp was analyzed using computer‐assisted techniques to scan B‐cell epitopes, and six possible linear B‐cell epitopes peptides (aa80–95, aa107–123, aa152–170, aa171–186, aa239–253 and aa497–513) with high predicted antigenicity and high conservation were investigated. Sera from mice immunized with these potential immunodominant peptides was analyzed by ELISA, which showed that epitope 152–170 elicited serum immunoglobulin G (IgG) response and epitope 171–186 elicited both serum IgG and mucosal secretory immunoglobulin A response. The response of immune sera of epitope 171–186 to endogenous Tarp antigen obtained from the Hela229 cells infected with C. trachomatis was confirmed by Western blot and indirect fluorescence assay. In addition, binding of the antibodies against epitope 171–186 to endogenous Tarp was further confirmed by competitive ELISA. Our results demonstrated that the putative epitope (aa171–186) was an immunodominant B‐cell epitope of Tarp. If proven protective and safe, this epitope, in combination with other well‐documented epitopes, might be included into a candidate epitope‐based vaccine against C. trachomatis. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

衣原体和淋球菌检测技术

从理论和应用方面介绍衣原体和淋球菌的各种检测技术,比较了各种检测技术的优缺点以及检测的敏感性、特异性,并展望了今后的应用前景。     

Protective monoclonal antibodies recognize epitopes located on the major outer membrane protein of Chlamydia trachomatis

A panel of monoclonal antibodies (MAb) was generated against Chlamydia trachomatis serovar B, an etiologic agent of blinding trachoma. The specificities of MAb were determined by dot blot assay by using viable elementary bodies of 13 C. trachomatis serovars and two C. psittaci strains. The dot blot assay was used to identify those antigens that were unique and immunoaccessible on the chlamydial surface. MAb were identified that recognized bi-specific (serovars B and Ba) or subspecies-specific (various B complex serovars) surface-exposed antigenic determinants that were either resistant or sensitive to heat denaturation (56 degrees C, 30 min). All of the MAb recognized the major outer membrane protein as determined by either immunoblotting or radioimmunoprecipitation. MAb specific for immunoaccessible major outer membrane protein epitopes protected mice from toxic death after i.v. injection of B serovar elementary bodies and neutralized the infectivity of the organism for monkey eyes. In contrast, MAb reactive against non-immunoaccessible subspecies- or species-specific major outer membrane protein epitopes or against an immunoaccessible genus-specific epitope located on chlamydial lipopolysaccharide did not protect mice from toxic death or neutralize infectivity of the parasite for monkey eyes. These data suggest that those major outer membrane protein antigenic determinants that are serovar or serogroup specific and are accessible to antibody on the chlamydial cell surface may be useful as a recombinant subunit vaccine for trachoma.     

Cell-mediated immune responses to Chlamydia trachomatis in mothers and infants

Cell-mediated immunity to Chlamydia trachomatis was studied in pregnant women with chlamydial infection of the cervix, in infants born vaginally to these women, and in infants presenting with chlamydial conjunctivitis. Uninfected pregnant women and their infants were studied as controls. McCoy cell cultures were used to isolate C. trachomatis from clinical specimens. Cell-mediated immunity was measured by lymphocyte proliferative responses in vitro to stimulation by chlamydial antigens. Chlamydial IgG antibody in serum specimens was detected by a microenzyme-linked immunosorbent assay technique. The mean lymphocyte proliferative responses to chlamydial antigens were greater in infected women than in uninfected women both during pregnancy and in the postpartum period. Lymphocyte responsiveness in infected pregnant women, however, was less than in postpartum women. Despite failure to detect chlamydial infection in exposed infants, lymphocyte proliferative responses were greater in umbilical cord blood and later in peripheral blood samples from neonates born to infected mothers than in infants born to uninfected mothers. These responses were also greater in infants with chlamydial conjunctivitis than in infants of uninfected mothers. These data suggest that cellular immune responses to chlamydial antigens are increased in infected mothers and infants and that infants may acquire chlamydial cell-mediated immunity transplacentally.     

Localization of erythrocyte membrane antigens by immune electron microscopy

Torus (T) protein was prepared by differential centrifugation of hemoglobin-free membranes after freezing, thawing and dialysis against water. Ferritin-labeled antibody to T protein failed to agglutinate erythrocytes or to sensitize them to complement lysis. Anti-T bound specifically to the internal aspect of ghosts and to the exterior of inverted vesicles prepared from them. The findings lend further support to the supposition that native T protein exists only on the inner aspect of intact erythrocyte membranes; its possible relation to spectrin is uncertain. In contrast, ferritin-labeled antibody to purified erythrocyte glycoprotein (virus receptor substance, VRS) agglutinated erythrocytes, sensitized them to complement lysis and by its specific reactivity with surface antigen afforded a basis for the electron microscopic quantitation of receptor sites on plasma membranes examined in thin section as well as with freeze-etching.     

Detection of Chlamydia trachomatis in Papanicolaou-stained cervical smears by an indirect immunoperoxidase method

A two-step (indirect) immunoperoxidase method directed against Chlamydia trachomatis was developed. The method was then used to evaluate the specificity of cytologic changes suggestive of C. trachomatis in Papanicolaou smears of cervical specimens from women who were culture-negative for the organism. Positive immunoperoxidase staining was detected in 9 of 21 cases (43%) tested. Technical problems, especially background staining, precluded interpretation in the remainder of the cases. Cervical cytology, as demonstrated by immunoperoxidase staining, may, in some instances, be more sensitive than the culture. However, because the etiology of cytologic changes not specifically identified by immunoperoxidase staining may be due to other organisms or factors, immunoperoxidase procedures, as described, should not replace culture for confirmation of cytologic findings suggestive of C. trachomatis.     

Identification of immunodominant linear B-cell epitopes within the major outer membrane protein of Chlamydia trachomatis

Chlamydia trachomatis is one of the most prevalent sexually transmitted pathogens. Chlamydial major outer membrane protein (MOMP) can induce strong cellular and humoral immune responses in murine models and has been regarded as a potential vaccine candidate. In this report, the amino acid sequence of MOMP was analyzed using computer-assisted techniques to scan B-cell epitopes, and three possible linear B-cell epitopes peptides (VLKTDVNKE, TKDASIDYHE, TRLIDERAAH) with high predicted antigenicity and high conservation were investigated. The DNA coding region for each potential epitope was cloned into pET32a(+) and expressed as Trx-His-tag fusion proteins in Escherichia coli. The fusion proteins were purified by Ni-NTA agarose beads and followed by SDS-PAGE and western blot analysis. We immunized mice with these three fusion proteins. The sera containing anti-epitope antibodies from the immunized mice could recognize C. trachomatis serovars D and E in ELISA. Antisera of these fusion proteins displayed an inhibitory effect on invasion of serovar E by in vitro neutralization assays. In addition, serum samples from convalescent C. trachomatis-infected patients were reactive with the epitope fusion proteins by western blot assay. Our results showed that the epitope sequences selected by bioinformatic analysis are highly conserved C. trachomatis MOMP B-cell epitopes, and could be good candidates for the development of subunit vaccines, which can be used in clinical diagnosis.     

Detection of parvoviruses in wolf feces by electron microscopy

One hundred fifteen wolf (Canis lupus) feces were collected between 1980 and 1984 from northeastern Minnesota and were examined for canine parvovirus by negative contrast electron microscopy. Of these, seven (6%) samples revealed the presence of parvovirus. Some of these viruses were able to grow in cell cultures forming intranuclear inclusion bodies and giant cells.     

Considerations on Chlamydia trachomatis disease expression

Chlamydia disease expression is the result of complex molecular and cellular interactions between the host and a pathogen which appears to have been sculpted by evolutionary forces. Recent genomic, immunologic, and epidemiologic findings are reviewed. A synthesis is offered which suggests that Chlamydia disease expression results from persistent infection and host immune responses.