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PubMed2005

Vaccination with the Chlamydia trachomatis major outer membrane protein can elicit an immune response as protective as that resulting from inoculation with live bacteria.

BALB/c mice were vaccinated by the intramuscular (i.m.) and subcutaneous (s.c.) routes with a native preparation of the Chlamydia trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP), using Montanide ISA 720 and CpG-1826 as adjuvants. A negative control group was immunized with ovalbumin and the two adjuvants, and a positive control group was immunized intranasally (i.n.) with 10(4) inclusion-forming units (IFU) of C. trachomatis. Four weeks after the last i.m.-plus-s.c. immunization, mice were challenged in the ovarian bursa with 10(5) IFU of C. trachomatis MoPn. Six weeks after the genital challenge, animals were mated, and the pregnancies were monitored. After vaccination with MOMP, the mice developed strong Chlamydia-specific humoral and cellular immune responses. Following the genital challenge, of the mice vaccinated with the MOMP, only 15% (3/20) had positive vaginal cultures, while 85% (17/20) of the animals immunized with ovalbumin had positive cultures over the 6 weeks of observation (P < 0.05). Also, only 14% (3/21) of the animals inoculated i.n. with Chlamydia had positive vaginal cultures. After mating, 75% (15/20) of the mice vaccinated with MOMP carried embryos in both uterine horns. Of the animals vaccinated i.n. with the Chlamydia, 81% (17/21) had embryos in both uterine horns (P > 0.05). In contrast, only 10% (2/20) of the mice immunized with ovalbumin had embryos in both uterine horns (P < 0.05). In conclusion, immunization with a purified preparation of the MOMP is as effective as vaccination with viable C. trachomatis in eliciting a protective immune response against a genital challenge in mice.

Animals↗

PubMed1986

Sequence analysis of the major outer membrane protein gene from Chlamydia trachomatis serovar L2.

The structural gene for the major outer membrane protein (MOMP) from Chlamydia trachomatis was cloned and sequenced. A lambda gt11 recombinant (lambda gt11/L2/33) that contains a portion of the MOMP coding sequence was used to probe a lambda 1059 library constructed from DNA obtained from C. trachomatis serovar L2. Selected lambda 1059 recombinants were mapped with endonuclease restriction enzymes. The MOMP gene was mapped to the 5' end of a BamHI fragment of approximately 9 kilobases. Contiguous endonuclease restriction fragments identified within this region permitted the selection of specific fragments for subcloning and DNA sequencing. The MOMP gene consisted of a 1,182-base-pair open reading frame that encoded 394 amino acids and ended with three stop codons. The known amino-terminal amino acid was preceded by 22 amino acids whose sequence was compatible with a leader or signal sequence. The primary structure of MOMP determined from the translated DNA sequence demonstrated nine cysteine residues and a remarkably homogeneous distribution of charged and hydrophobic residues.

Amino Acid Sequence↗

PubMed1991

Detection and strain differentiation of Chlamydia psittaci mediated by a two-step polymerase chain reaction.

Specific and sensitive amplification of major outer membrane protein (MOMP) gene DNA sequences of Chlamydia psittaci was achieved in a two-step polymerase chain reaction. First, oligonucleotide primers specific for 5' and 3' nontranslated regulatory regions of the MOMP gene were used in a polymerase chain reaction to amplify a DNA fragment of approximately 1,400 bp. A portion of this DNA fragment was amplified in a second reaction using a degenerate oligonucleotide primer specific for a DNA sequence contained within the 1,400-bp DNA fragment and one of the first-step primers. This method detected 10 cognate chlamydial genomes. C. psittaci MOMP genes from two avian strains and from mammalian serovars 1, 7, and 8 were amplified and analyzed by restriction endonuclease digestion. MOMP genes from mammalian serovars 2 through 6 and 9 and from strains of C. trachomatis and C. pneumoniae could not be amplified. Restriction endonuclease analysis with HaeIII indicated a close relationship between C. psittaci strains of avian and mammalian serovar 1 lineage, while those of mammalian serovars 7 and 8 exhibited distinct restriction patterns. DNA sequences corresponding to the mammalian serovar 1-wild type parakeet MOMP genotype of C. psittaci were detected in two of seven milk samples from cases of bovine mastitis.

Animals↗

PubMed1993

Comparison of plasmid- and chromosome-based polymerase chain reaction assays for detecting Chlamydia trachomatis nucleic acids.

Several laboratories have demonstrated that the polymerase chain reaction (PCR) is more sensitive than culture or enzyme immunoassay (EIA) for detecting Chlamydia trachomatis in genitourinary tract specimens when various DNA targets are used for amplification, including the cryptic plasmid, major outer membrane protein (MOMP), or rRNA genes. We compared the performances of five different PCR assays, including assays with two plasmid, two MOMP, and one rRNA targets, by amplifying serial dilutions of C. trachomatis DNA and testing genitourinary tract specimens. By using published procedures, two different plasmid primers had sensitivities of 0.1 fg for C. trachomatis plasmid DNA and 10 fg for total cellular DNA. The sensitivities of the assays with the two MOMP primers were 0.1 and 10 pg, and the sensitivity for the assay with the rRNA primers was 1 pg for cellular DNA. Both plasmid-based assays detected 38 of 38 confirmed Chlamydiazyme-positive specimens, whereas the assays with the MOMP and rRNA primers detected 36 of 38 and 29 of 38 confirmed Chlamydiazyme-positive specimens, respectively. Six of 18 Chlamydiazyme-negative specimens collected from individuals whose specimens were positive by culture or immunofluorescence were positive by both plasmid-based PCRs; 4 of these were positive by PCR with the MOMP primers and 3 were positive by PCR with the rRNA primers. The results obtained with both purified DNA and genitourinary tract specimens indicated that the plasmid-based PCRs are more sensitive than bacterial chromosome-based PCRs for detecting C. trachomatis.

Bacterial Outer Membrane Proteins↗

PubMed1991

A single peptide from the major outer membrane protein of Chlamydia trachomatis elicits T cell help for the production of antibodies to protective determinants.

The protective immune response to infection with Chlamydia trachomatis is associated with antibody reactivity to serovar-specific determinants on the major outer membrane protein (MOMP). Because this immunity is T cell dependent, it is essential to define those Th cell determinants that promote natural boosting of the protective antibody response. The gene for MOMP of serovar B was separated into nine overlapping fragments that represent the five C and four V regions. These fragments were expressed as fusion peptides with GST and used to identify the regions of the MOMP that contain T cell determinants recognized in BALB/c mice. We identified peptides that elicit a T cell response to Chlamydia by immunizing mice with the fusion peptides and testing the proliferative response of T cells in vitro to intact organism. For analysis of determinants seen after infection, animals were inoculated with live organism and the T cell proliferative response to each fusion peptide was measured in vitro. In contrast to proliferative analysis in which several regions of the MOMP elicited T cell responses, functional analysis demonstrated that a single fusion peptide, containing V segment three, elicited T cell help in vivo for the production of high titered antisera, specific for protective determinants on the MOMP.

Animals↗

PubMed1991

Rapid genotyping of the Chlamydia trachomatis major outer membrane protein by the polymerase chain reaction.

Twenty one Chlamydia trachomatis reference strains and 40 clinical isolates belonging to the lymphogranuloma venerum (LGV) and trachoma biovars were genotyped by differential restriction mapping of the major-outer-membrane-protein gene (MOMP) obtained by the polymerase-chain reaction (PCR). AluI digestion of the PCR product distinguishes eight MOMP-genotypes corresponding to 8 serovars. Six additional enzymes (NlaIII, CfoI, EcoRI, HinfI, DdeI and FokI) further permit the discrimination of 10 MOMP-genotypes corresponding to the 10 remaining serovars of the species. AluI alone allows direct typing of 78% of the clinical isolates. AluI digestion patterns of mouse C. trachomatis biovar, a C. pneumoniae and two C. psittaci strains, studied for comparison, were clearly distinguishable from one another and from the C. trachomatis LGV and trachoma strains. These results indicate that MOMP genotyping by PCR is a valuable molecular tool for studying C. trachomatis epidemiology.

Bacterial Outer Membrane Proteins↗

PubMed1994

Remarkable sequence relatedness in the DNA encoding the major outer membrane protein of Chlamydia psittaci (koala type I) and Chlamydia pneumoniae.

DNA encoding the major outer membrane protein (MOMP) of the koala type-I strain of Chlamydia psittaci (pathogen responsible for blindness and infertility in koalas) was cloned and sequenced. Comparison with momp gene sequences from other chlamydial species revealed a remarkable degree of homology (> 97%) with that of the human pathogen, Chlamydia pneumoniae. In comparison, the sequence only shared 75% DNA sequence homology with other C. psittaci members and 69% homology with C. trachomatis. The open reading frame consisted of 1167 bp encoding a 389-amino acid (aa) pre-MOMP including a leader sequence of 23 aa, similar to the C. pneumoniae gene. These genes were closely related even within the four variable domains (86-100% homology). Specific antibodies were capable of distinguishing between koala type I and C. pneumoniae. This very high degree of relatedness between C. pneumoniae, a human pathogen, and an individual strain of C. psittaci in the momp gene raises further questions on the host specificity, classification and evolutionary relationships of the different chlamydial species.

Amino Acid Sequence↗

PubMed2006

At the gates of death.

Apoptosis that proceeds via the mitochondrial pathway involves mitochondrial outer membrane permeabilization (MOMP), responsible for the release of cytochrome c and other proteins of the mitochondrial intermembrane space. This essential step is controlled and mediated by proteins of the Bcl-2 family. The proapoptotic proteins Bax and Bak are required for MOMP, while the antiapoptotic Bcl-2 proteins, including Bcl-2, Bcl-xL, Mcl-1, and others, prevent MOMP. Different proapoptotic BH3-only proteins act to interfere with the function of the antiapoptotic Bcl-2 members and/or activate Bax and Bak. Here, we discuss an emerging view, proposed by Certo et al. in this issue of Cancer Cell, on how these interactions result in MOMP and apoptosis.

Animals↗

PubMed2004

Influence of maternal antibodies on Chlamydophila psittaci-specific immune responses in turkeys elicited by naked DNA.

Plasmid DNA (pcDNA1::MOMP D) expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain was tested for its ability to induce protective immunity against C. psittaci challenge in the presence of maternal antibodies. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was used. Following pcDNA1::MOMP vaccination, both T helper and B cell memory were primed. However, high maternal antibodies titres affected the induction of vaccine-specific antibody responses as assessed by MOMP-specific antibody levels in enzyme-linked immunosorbent assay (ELISA). Cell-mediated immunity was unaltered as demonstrated by the significantly heightened proliferative responses of peripheral blood lymphocytes (PBL) following vaccination. DNA vaccination could significantly reduce clinical symptoms, pharyngeal and cloacal excretion as well as Chlamydophila replication, even in the presence of maternal antibodies.

Administration, Intranasal↗

PubMed2005

CpG motifs as adjuvant in DNA vaccination against Chlamydophila psittaci in turkeys.

Plasmid DNA (pcDNA1::MOMP) expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain and recombinant MOMP (rMOMP) with or without the immunomodulating CpG oligonucleotides (CpG ON) were tested for their ability to elicit an immune response and to induce protection in turkeys against homologous challenge. Two CpG ON were chosen for in vivo application based on their in vitro capacity to stimulate the production of nitric oxide (NO) in chicken macrophages and their in vitro capacity to induce turkey lymphocyte proliferation. Priming and boosting of turkeys with pcDNA1::MOMP was able to prevent severe clinical signs and bacterial replication in a turkey model of C. psittaci infection. rMOMP boosting induced high antibody titers, but these did not correlate with the level of protection. Although the CpG ON induced a significant in vitro response, the presence of the CpG ON as an adjuvant generated no significant effect on the immune response or on the protective capacity of the tested vaccination methods.

Animals↗

PubMed2000

Design, expression and functional characterization of a synthetic gene encoding the Chlamydia trachomatis major outer membrane protein.

A synthetic gene coding for the Chlamydia trachomatis serovar L2 major outer membrane protein (MOMP) was designed, constructed and expressed in Escherichia coli. The native amino acid sequence was reverse translated and the resulting nucleotide combinations manipulated in order to evenly distribute 25 unique restriction sites along the length of the gene while retaining the native amino acid sequence. The synthetic gene was cloned into a T7 promoter-controlled plasmid (pET-3a) and the expressed product was analyzed to assess antigenicity, cellular localization and function. Monoclonal antibodies specific for native MOMP reacted to the expressed product by immunoblot. Outer membrane fractionation confirmed that the processed protein was located in the outer membrane. MOMP expressed in E. coli and present in the outer membrane was shown to function as a general diffusion porin. This system provides the means to produce readily modifiable MOMP either in purified form or as a membrane-associated protein, and so facilitate the investigation of its functional, structural and antigenic properties.

Amino Acid Sequence↗

PubMed1994

Isolation and partial characterization of the major protein of the outer membrane of Pasteurella haemolytica and Pasteurella multocida.

The N-terminal amino acid sequence of the 35 kDa (p35) major outer membrane protein (MOMP) of P. multocida shared a strong homology with those of homotrimeric nonspecific porins of gram-negative bacteria. The capacity of outer membrane protein (OMP) preparations of P. multocida to bind to respiratory mucosal surface preparations was inhibited significantly by using a polyclonal anti-p35 antiserum in an adhesion ELISA. Anti-p35 antiserum cross-reacted with a 44 kDa (p44) MOMP of P. haemolytica. N-terminal sequencing of MOMP p44 revealed a homology of 81% with the putative porin MOMP p35 of P. multocida.

Amino Acid Sequence↗

PubMed1997

Synthetic peptides based on Chlamydia trachomatis antigens identify cytotoxic T lymphocyte responses in subjects from a trachoma-endemic population.

CD8+ cytotoxic T lymphocytes (CTL) recognize peptide antigens in the context of class I MHC antigen molecules. To identify peptides capable of eliciting anti-Chlamydia trachomatis CTL responses, 13 synthetic peptides conforming to human leucocyte antigen (HLA)-B8- or -B35-predicted binding motifs were synthesized using sequences based on C. trachomatis major outer membrane protein (MOMP) and heat shock protein 60 (hsp60). Two of 11 HLA-B35-predicted binding peptides were able to stabilize HLA-B35 in an in vitro binding assay. All peptides were tested in CTL assays using peripheral blood mononuclear cells (PBMC) isolated from 26 HLA-B8 or -B35 individuals resident in a trachoma-endemic community. Responses to MOMP and hsp60 peptides were identified in a minority of both HLA-B8 and -B35 individuals. Two of 12 HLA-B8 subjects responded to MOMP and 1/13 to hsp60 peptides. Responses in HLA-B35 subjects were similar, 1/13 subjects responding to MOMP and 2/13 to hsp60 peptides. CTL responses were observed only in children resolving current infection and in adults without scarring of the conjunctiva. These results suggest that anti-chlamydial CTL occur at low levels in peripheral blood, but may be important in the resolution of naturally acquired human ocular chlamydial infection.

Adult↗

PubMed1988

Mapping antigenic domains expressed by Chlamydia trachomatis major outer membrane protein genes.

Chlamydia trachomatis is an obligate prokaryotic intracellular pathogen of humans that infects mucosal epithelial cells. Exposed domains of its major outer membrane protein (MOMP) are both serotyping and protective antigenic determinants. To identify these domains, we have cloned and epitope-mapped the genes of serovars A, C (C serogroup) and L2, B (B serogroup) with a panel of monoclonal antibodies (mAbs). Predominantly conserved regions of the genes of both serogroups are interspersed with four short variable domains (I-IV). Recombinant phage clones expressing specific MOMP antigenic determinants revealed that protective serotype-specific recognized epitopes in variable domains I and II. Protective subspecies and serogroup-specific mAbs recognized overlapping determinants in variable domain IV near the C terminus. A nonprotective species-specific mAb mapped to an invariant peptide of nine residues contained within variable domain IV. In the intact chlamydial organism of serovar B, variable domains II and IV were susceptible to proteolytic digestion, whereas both N and C termini were protected. These results suggest an arrangement of MOMP in the outer membrane in which three of the four variable domains are exposed to the outside and in which both N and C termini are presumably oriented toward the periplasmic space. This molecular analysis of MOMP antigenic determinants and their surface topology on intact chlamydiae will be useful toward the development of a recombinant subunit or synthetic chlamydial vaccine.

Amino Acid Sequence↗

PubMed1988

High-resolution mapping of serovar-specific and common antigenic determinants of the major outer membrane protein of Chlamydia trachomatis.

The principal surface protein antigen of Chlamydia trachomatis is the major outer membrane protein (MOMP). The MOMP is antigenically complex. Among the 15 serovars of C. trachomatis, mAbs define serovar-, subspecies-, and species-specific determinants on MOMP. The molecular basis of the antigenic diversity of these proteins is reflected in amino acid variable sequence domains. We have mapped the dominant topographic antigenic determinants of MOMP that are defined by mAbs. Using recombinant DNA approaches we have identified the linear distribution of two antigenic domains. One domain contains a serovar-specific determinant and the other contains subspecies- and species-specific determinants. These antigenic domains correspond to two amino acid sequence variable domains. Synthetic peptides were immunogenic and these resolved the serovar-specific determinant within a 14-amino acid peptide. The subspecies- and species-specific determinants were overlapping within a 16-amino acid peptide.

Amino Acid Sequence↗

PubMed1998

Identification of T cells that respond to serovar-specific regions of the Chlamydia trachomatis major outer membrane protein in persons with serovar E infection.

Protection from Chlamydia trachomatis infection is serovar-specific and T cell-dependent; however, the T cell epitopes identified to date have not been serovar-specific. The chlamydial major outer membrane protein (MOMP) contains serovar-specific B cell epitopes in four regions of the molecule whose amino acid sequence varies among serovars, the variable segments (VS). Serovar-specific T cell epitopes were sought by examining proliferation of blood mononuclear cells (PBMC) from Chlamydia-infected patients in response to VS peptides of serovar E MOMP. Serovar E-specific peptides from VS1, VS2, and VS4 stimulated PBMC to a greater extent in serovar E-infected than in non-E-infected subjects. Peptides containing constant regions of MOMP were recognized equally by all infected persons. The observed responses were attributable to T cells. T cell recognition of serovar-specific regions of MOMP is common and may contribute to the serovar-specific protection previously observed.

Amino Acid Sequence↗

PubMed1984

Chlamydial pneumonitis and its serodiagnosis in infants.

Sera from 30 infants with suspected chlamydial pneumonitis were studied by enzyme immunoassay (EIA) with three antigens: reticulate bodies (RB), purified major outer membrane protein ( MOMP ) of Chlamydia trachomatis strain L2, and purified lipopolysaccharide from Re mutants of Salmonella (Re LPS), which shows complete cross-reaction with chlamydial glycolipid. The immunofluorescence test (I/RB IFAT), which detected IgM antibodies (titer of greater than or equal to 1:64) in 16 patients whose clinical picture was consistent with chlamydial pneumonitis, was the standard method. EIA measured IgM antibodies to the purified antigens but not to RB; 15 sera were positive with the MOMP antigen and two with the Re LPS antigen. High-titered IgG antibodies were detected by I/RB IFAT in 15 and by MOMP EIA in 13 of the 30 sera. By the RB EIA, 17 sera were positive. The MOMP EIA was thus as sensitive and specific as the I/RB IFAT. Because the EIA can be automated, it would make possible the screening of all children younger than six months of age with respiratory-tract symptoms and IgM antibodies to Chlamydia.

Bacterial Outer Membrane Proteins↗

PubMed1992

Evaluation of the humoral immune response in trachoma to Chlamydia trachomatis major outer membrane proteins by sequence-defined immunoassay.

The Chlamydia trachomatis immunodominant major outer membrane protein (MOMP) is both a target of neutralizing antibodies and the serotyping antigen and thus has been a focus of diagnostic, seroepidemiologic, and experimental investigations. The microimmunofluorescence (MIF) test has been the principal tool in serologic investigations of chlamydial infections but is difficult and expensive for routine use; moreover, since it uses whole organisms as antigen, it is incapable of revealing the molecular specificity of the humoral response to infection. These limitations were resolved by using synthetic peptides corresponding to serovar-specific antigenic regions of MOMP in an ELISA-based format to analyze the serospecificity of sera from trachoma cases. The ELISA reaction to the surface-exposed MOMP sequence variable segment 1 was immunodominant and serovar-specific and was in concordance with serovar specificity according to paired MIF test determinations. Understanding the patterns of humoral responses to MOMP determinants in patient populations will advance our knowledge of their role in the immunobiology of naturally acquired infection.

Amino Acid Sequence↗