Induction of antibody response to Chlamydia trachomatis in the genital tract by oral immunization

Vaccination with the recombinant major outer membrane protein elicits long-term protection in mice against vaginal shedding and infertility following a Chlamydia muridarum genital challenge

Implementation of a vaccine is likely the best approach to curtail Chlamydia trachomatis infections. The aim of this study was to determine the ability of a vaccine formulated with the recombinant major outer membrane protein (MOMP) and Th1 and Th2 adjuvants, delivered by combinations of systemic and mucosal routes, to elicit long-term protection in mice against a genital challenge with Chlamydia muridarum. As a negative control, mice were vaccinated with the recombinant Neisseria gonorrhoeae porinB, and the positive control group was immunized with C. muridarum live elementary bodies (EB). The four vaccines formulated with MOMP, as determined by the titers of IgG and neutralizing antibodies in serum, proliferative responses of T-cells stimulated with EB and levels of IFN-γ in the supernatants, elicited robust humoral and cellular immune responses over a 6-month period. Groups of mice were challenged genitally at 60, 120, or 180 days postimmunization. Based on the number of mice with positive vaginal cultures, number of positive cultures, length of time of shedding, and number of inclusion forming units recovered, MOMP vaccinated groups were significantly protected. To assess fertility, when the vaginal cultures became negative, female mice were caged with male mice and the outcome of the pregnancy evaluated. As determined by the number of pregnant mice and the number of embryos, two of the vaccine formulations protected mice up to 180 days postimmunization. To our knowledge this is the first subunit of Chlamydia vaccine that has elicited in mice significant long-term protection against a genital challenge.

Repeated oronasal exposure to lipopolysaccharide induced mucosal IgA responses in periparturient dairy cows

This study investigated the effects of repeated oronasal treatment with lipopolysaccharide (LPS) on the humoral immune responses in saliva, vaginal mucus, and the plasma markers of the acute phase response in periparturient dairy cows. One hundred pregnant Holstein cows were administered either 3 increasing doses of LPS (n = 50) as follows: 1) 0.01 µg/kg body weight (BW) on d −28, 2) 0.05 µg/kg BW on d −25, and −21, and 3) 0.1 µg/kg BW on d −18, and −14, or sterile saline solution (controls; n = 50) oronasally for 3 consecutive wk starting at 28 d before parturition. Intensive sampling was conducted on thirty cows (n = 15/group). Multiple saliva, vaginal mucus and blood samples were collected around parturition and analyzed for total immunoglobulin-(Ig)A, plasma serum amyloid A (SAA), lipopolysaccharide-binding protein (LBP), anti-LPS IgA, IgG, IgM, tumour necrosis factor(TNF)-α, and interleukin(IL)-1. Results regarding total secretory IgA (sIgA) antibodies showed greater concentrations in the saliva and an overall tendency for higher total sIgA in the vaginal mucus of the LPS-treated cows. Treatment had no effect on plasma sIgA, IgG, IgM anti-LPS antibodies, haptoglobin, SAA, LBP, TNF-α, and IL-1. Treatments by time interactions were observed for SAA and IL-1 with lowered concentrations of both variables in the plasma of LPS-treated cows after parturition. Overall, repeated oronasal LPS treatment clearly enhanced total sIgA antibodies in the saliva, stimulated their production in vaginal mucus shortly before calving, and lowered plasma IL-1 around parturition, but showed limited effects on markers of the acute phase response in the plasma in dairy cows around parturition.

Protective immunity against mouse upper genital tract pathology correlates with high IFNγ but low IL-17 T cell and anti-secretion protein antibody responses induced by replicating chlamydial organisms in the airway

To search for optimal immunization conditions for inducing protective immunity against upper genital tract pathologies caused by chlamydial intravaginal infection, we compared protection efficacy in mice immunized intranasally or intramuscularly with live or inactivated Chlamydia muridarum organisms. Mice immunized intranasally with live organisms developed strong protection against both vaginal shedding of infectious organisms and upper genital tract pathologies. The protection correlated with a robust antigen-specific T cell response with high IFNγ but low IL-17. Although a significant level of IL-5 was also detected, these mice maintained an overall Th1-dorminant immunity following immunization and challenge infection. On the contrary, mice immunized intranasally with inactivated organisms or intramuscularly with live or inactivated organisms produced high levels of IL-17 and still developed significant upper genital tract pathologies. High titers of antibodies against chlamydial secretion antigens were detected only in mice immunized intranasally with live organisms but not mice in other groups, suggesting that the intranasally inoculated live organisms were able to undergo replication and immune responses to the chlamydial secretion proteins may contribute to protective immunity. These observations have provided important information on how to develop subunit vaccines for inducing protective immunity against urogenital infection with Chlamydia trachomatis organisms.

Tonsillar application of AT-2 SIV affords partial protection against rectal challenge with SIVmac239

BACKGROUND

Although mucosal responses are important for preventing infections with HIV, the optimal strategies for inducing them remain unclear. To evaluate vaccine strategies targeting the oral mucosal lymphoid tissue inductive sites as an approach to provide immunity at distal sites, we vaccinated healthy macaques via the palatine/lingual tonsils with aldrithiol 2 (AT-2) inactivated Simian immunodeficiency virus (SIV)mac239, combined with CpG-C immunostimulatory oligonucleotide (CpG-C ISS-ODN, C274) as the adjuvant.

METHODS

Macaques received 5 doses of C274 or control ODN C661 and AT-2 SIV on the tonsillar tissues every 6 weeks before being challenged rectally with SIVmac239, 8 weeks after the last immunization.

RESULTS

Although no T-cell or B-cell responses were detected in the blood before challenge, antibody (Ab) responses were detected in the rectum. Immunization with AT-2 SIV significantly reduced the frequency of infection compared with nonimmunized controls, irrespective of adjuvant. In the vaccinated animals that became infected, peak viremias were somewhat reduced. SIV-specific responses were detected in the blood once animals became infected with no detectable differences between the differently immunized groups and the controls.

CONCLUSION

This work provides evidence that vaccine immunogens applied to the oral mucosal associated lymphoid tissues can provide benefit against rectal challenge, a finding with important implications for mucosal vaccination strategies.

Nouvelles voies d’administration : vaccinations par voie épidermique, intradermique, muqueuse

A successful vaccine triggers the interaction of various cells of the immune system as does a regular immune response. It is thus necessary to introduce the vaccine antigens into an anatomic site where they will contact immune cells. The route of administration is thus critical for the outcome of vaccination. Intramuscular or subcutaneous injections are the most popular. Antigens injected intramuscularly can form persistent precipitates that are dissolved and re-absorbed relatively slowly. If injecting antigens is a quick, easy and reproducible way to vaccination, it requires trained personnel. Alternatives exist, through non-invasive formulations which allow administration by the patient or a third party with no particular expertise. The skin, especially its epidermal layer, is an accessible and competent immune environment and an attractive target for vaccine delivery, through transcutaneous delivery or immunostimulant patches. Mucosal immunization is another strategy: its major rationale is that organisms invade the body via mucosal surfaces. Therefore, local protection at mucosal surface as well as systemic defense is beneficial. Various formulations of mucosal vaccines have been developed, such as the Sabin oral polio vaccine (OPV), rotavirus vaccines, cold-adapted influenza vaccines or vaccine against typhoid fever. Thus we are entering in an era where mucosal and transcutaneous immunisation will play an important role in disease management. However, it has not been so easy to obtain regulatory approval for mucosal or transcutaneous formulations and needle-based vaccines continue to dominate the market.

A novel surface protein of Trichomonas vaginalis is regulated independently by low iron and contact with vaginal epithelial cells

BACKGROUND

Trichomonosis caused by Trichomonas vaginalis is the number one, non-viral sexually transmitted disease (STD) that affects more than 250 million people worldwide. Immunoglobulin A (IgA) has been implicated in resistance to mucosal infections by pathogens. No reports are available of IgA-reactive proteins and the role, if any, of this class of antibody in the control of this STD. The availability of an IgA monoclonal antibody (mAb) immunoreactive to trichomonads by whole cell (WC)-ELISA prompted us to characterize the IgA-reactive protein of T. vaginalis.

RESULTS

An IgA mAb called 6B8 was isolated from a library of mAbs reactive to surface proteins of T. vaginalis. The 6B8 mAb recognized a 44-kDa protein (TV44) by immunoblot analysis, and a full-length cDNA clone encoded a protein of 438 amino acids. Southern analysis revealed the gene (tv44) of T. vaginalis to be single copy. The tv44 gene was down-regulated at both the transcriptional and translational levels in iron-depleted trichomonads as well as in parasites after contact with immortalized MS-74 vaginal epithelial cells (VECs). Immunofluorescence on non-permeabilized organisms confirmed surface localization of TV44, and the intensity of fluorescence was reduced after parasite adherence to VECs. Lastly, an identical protein and gene were present in Tritrichomonas foetus and Trichomonas tenax.

CONCLUSION

This is the first report of a T. vaginalis gene (tv44) encoding a surface protein (TV44) reactive with an IgA mAb, and both gene and protein were conserved in human and bovine trichomonads. Further, TV44 is independently down-regulated in expression and surface placement by iron and contact with VECs. TV44 is another member of T. vaginalis genes that are regulated by at least two independent signaling mechanisms involving iron and contact with VECs.

Intranasal administration of recombinant Neisseria gonorrhoeae transferrin binding proteins A and B conjugated to the cholera toxin B subunit induces systemic and vaginal antibodies in mice

The transferrin binding proteins (TbpA and TbpB) comprise the gonococcal transferrin receptor and are considered potential antigens for inclusion in a vaccine against Neisseria gonorrhoeae. Intranasal (IN) immunization has shown promise in development of immunity against sexually transmitted disease pathogens, in part due to the induction of antigen-specific genital tract immunoglobulin A (IgA) and IgG. Conjugation of antigens to the highly immunogenic cholera toxin B subunit (Ctb) enhances antibody responses in the serum and mucosal secretions following IN vaccination. In the current study, we characterized the anti-Tbp immune responses following immunization of mice IN with recombinant transferrin binding proteins (rTbpA and rTbpB) conjugated to rCtb. We found that both rTbpA-Ctb and rTbpB-Ctb conjugates administered IN induced antibody responses in the serum and genital tract. IN immunization resulted in both IgA and IgG in the genital tract; however, subcutaneous immunization mainly generated IgG. Surprisingly, rTbpA alone was immunogenic and induced serum and mucosal antibody responses similar to those elicited against the rTbpA-Ctb conjugate. Overall, rTbpB was much more immunogenic than rTbpA, generating serum IgG levels that were greater than those elicited against rTbpA. Bactericidal assays conducted with sera collected from mice immunized IN with TbpA and/or TbpB indicated that both antigens generated antibodies with bactericidal activity. Anti-TbpA antibodies were cross-bactericidal against heterologous gonococcal strains, whereas TbpB-specific antibodies were less cross-reactive. By contrast, antibodies elicited via subcutaneous immunization were not cross-bactericidal against heterologous strains, indicating that IN vaccination could be the preferred route for elicitation of biologically functional antibodies.

Vaccination strategies against Tritrichomonas foetus

Immunoprophyloxis for bovine trichomoniosis has been a priority because of the high prevalence o f the disease, the considerable economic loss due to the infection and the lack of approved chemotherapeutic agents. The commercial availability of first-generation vaccines provides hope not only for even more effective immunization regimens far this disease, but also for other protozoal infections and for sexually transmitted diseases (STDs) caused by a wide variety of infectious agents. At present, efficacious vaccines for protozoal diseases and for STDs are rare. Since information gained on immunization against Tritrichomonas foetus may have broad significance for control of these two classes of infection,it is important to explore the biological basis of protection against this protozoal infection of the reproductive tract In this paper, Lynette Corbeil reviews data on host-parasite relationships in bovine trichomoniasis as a basis for developing vaccine strategies.

A unique population of extrathymically derived alpha beta TCR+CD4-CD8- T cells with regulatory functions dominates the mouse female genital tract

A better understanding of the regulatory role of genital tract T cells is much needed. In this study, we have analyzed the phenotype, distribution, and function of T lymphocytes in the female genital tract of naive, pregnant, or Chlamydia trachomatis-infected C57BL/6 mice. Unexpectedly, we found that the dominant lymphocyte population (70-90%) in the genital tract was that of CD3(+)alphabetaTCR(int)CD4(-)CD8(-) T cells. Moreover, these cells were CD90(low) but negative for the classical T cell markers CD2 and CD5. The CD3(+)B220(low) cells were NK1.1 negative and found in nude mice as well as in mice deficient for MHC class II, beta(2)-microglobulin, and CD1, indicating extrathymic origin. They dominated the KJ126(+)Vbeta8.2(+) population in the genital tract of DO11.10 OVA TCR-transgenic mice, further supporting the idea that the CD3(+)B220(low) cells are truly T cells. The function of these T cells appeared not to be associated with immune protection, because only CD4(+) and CD8(+) T cells increased in the genital tract following chlamydial infection. Notwithstanding this, the infected, as well as the uninfected and the pregnant, uterus was dominated by a high level of the CD3(+)CD4(-)CD8(-)B220(low) cells. Following in vitro Ag or polyclonal stimulation of the CD3(+)CD4(-)CD8(-)B220(low) cells, poor proliferative responses were observed. However, these cells strongly impaired splenic T cell proliferation in a cell density-dependent manner. A large fraction of the cells expressed CD25 and produced IFN-gamma upon anti-CD3 plus anti-CD28 stimulation, arguing for a strong regulatory role of this novel T cell population in the mouse female genital tract.

Vaccination strategies for mucosal immune responses

Mucosal administration of vaccines is an important approach to the induction of appropriate immune responses to microbial and other environmental antigens in systemic sites and peripheral blood as well as in most external mucosal surfaces. The development of specific antibody- or T-cell-mediated immunologic responses and the induction of mucosally induced systemic immunologic hyporesponsiveness (oral or mucosal tolerance) depend on complex sets of immunologic events, including the nature of the antigenic stimulation of specialized lymphoid structures in the host, antigen-induced activation of different populations of regulatory T cells (Th1 versus Th2), and the expression of proinflammatory and immunoregulatory cytokines. Availability of mucosal vaccines will provide a painless approach to deliver large numbers of vaccine antigens for human immunization. Currently, an average infant will receive 20 to 25 percutaneous injections for vaccination against different childhood infections by 18 months of age. It should be possible to develop for human use effective, nonliving, recombinant, replicating, transgenic, and microbial vector- or plant-based mucosal vaccines to prevent infections. Based on the experience with many dietary antigens, it is also possible to manipulate the mucosal immune system to induce systemic tolerance against environmental, dietary, and possibly other autoantigens associated with allergic and autoimmune disorders. Mucosal immunity offers new strategies to induce protective immune responses against a variety of infectious agents. Such immunization may also provide new prophylactic or therapeutic avenues in the control of autoimmune diseases in humans.

Vaccination strategies for mucosal immune responses

Mucosal administration of vaccines is an important approach to the induction of appropriate immune responses to microbial and other environmental antigens in systemic sites and peripheral blood as well as in most external mucosal surfaces. The development of specific antibody- or T-cell-mediated immunologic responses and the induction of mucosally induced systemic immunologic hyporesponsiveness (oral or mucosal tolerance) depend on complex sets of immunologic events, including the nature of the antigenic stimulation of specialized lymphoid structures in the host, antigen-induced activation of different populations of regulatory T cells (Th1 versus Th2), and the expression of proinflammatory and immunoregulatory cytokines. Availability of mucosal vaccines will provide a painless approach to deliver large numbers of vaccine antigens for human immunization. Currently, an average infant will receive 20 to 25 percutaneous injections for vaccination against different childhood infections by 18 months of age. It should be possible to develop for human use effective, nonliving, recombinant, replicating, transgenic, and microbial vector- or plant-based mucosal vaccines to prevent infections. Based on the experience with many dietary antigens, it is also possible to manipulate the mucosal immune system to induce systemic tolerance against environmental, dietary, and possibly other autoantigens associated with allergic and autoimmune disorders. Mucosal immunity offers new strategies to induce protective immune responses against a variety of infectious agents. Such immunization may also provide new prophylactic or therapeutic avenues in the control of autoimmune diseases in humans.

Immunological memory in B-cell-deficient mice conveys long-lasting protection against genital tract infection with Chlamydia trachomatis by rapid recruitment of T cells

The role of antibodies and antigen deposition for the development of immunological memory has been incompletely investigated. We addressed whether long-term protection and T-cell memory can be stimulated against a genital tract infection with human Chlamydia trachomatis serovar D in B-cell-deficient (muMT) mice. At 6 months following a primary infection with C. trachomatis, both muMT and wild-type (WT) mice exhibited strong and comparable protection against reinfection. Evidence of long-lasting CD4+ T-cell memory was found in both muMT and WT mice, typified by comparable delayed-type hypersensitivity (DTH) reactions against chlamydial antigens. No bacterial or chlamydial DNA was found in the genital tract of muMT memory mice, suggesting that immunological memory was maintained in the absence of antigen. Whereas few T cells were present in the genital tract of memory mice, rapid recruitment of CD4+, and some CD8+, T cells into the genital tract tissue was observed after challenge with live bacteria. Accumulation of T cells in the genital tract was preceded by a short transient infection of similar magnitude in both muMT and WT memory mice, arguing against a long-term protective role of local antibodies. The rapid recruitment of CD4+ T cells into the genital tract was associated with a transient detection of interferon-gamma (IFN-gamma) mRNA in the genital tract in chlamydia-immune memory mice, which was not found in naïve, challenged mice. Thus, long-term protection in the genital tract against C. trachomatis infection is conveyed by IFN-gamma-producing CD4+ memory T cells, which appear to be maintained in the absence of antibodies and local antigen deposition.

Genital antibody responses in mice after intranasal infection with an attenuated candidate vector strain of Bordetella pertussis

Intranasal administration of live attenuated Bordetella pertussis, from which the pertussis toxin gene has been deleted, has previously been shown to give rise to high levels of serum immunoglobulin G (IgG) antibodies against both the protective antigen filamentous hemagglutinin (FHA) and heterologous antigens genetically fused to FHA. Here, we extend these results by demonstrating that anti-FHA IgA and IgG antibodies are also produced in the genital tract of mice, both in the vagina and in the uterus, after a single intranasal administration of B. pertussis. By comparing the immune responses induced after infection with wild-type virulent B. pertussis with that induced by infection with an attenuated pertussis toxin-deficient strain, we conclude that pertussis toxin produced by the virulent bacteria does not modify antibody production to FHA in the genital tract of B. pertussis-infected mice. The intranasal infection with either the attenuated or the virulent B. pertussis strain also led to the development of immunologic memory that could be efficiently boosted with purified FHA administered either intranasally or intravaginally to give rise to a significant increase in the levels of specific IgA and IgG produced locally in the genital tract, as well as of specific antibodies in the serum. These observations suggest that attenuated B. pertussis could be a promising vector for intranasal administration to induce antibody responses against antigens from sexually transmitted pathogens fused to FHA.

Characterization of the mucosal immune response in breast milk after peroral immunization of chimpanzees (Pan troglodytes) with Streptococcus mutans

The characteristics of the mucosal immune response to Streptococcus mutans cells, antigen A, antigen B, glucosyltransferases and glucan-binding proteins were examined in four pregnant chimpanzees that had been immunized perorally with Strep. mutans. Six pregnant chimpanzees served as non-immunized controls. None of the chimpanzees harbored S. mutans. Samples of milk were collected from all animals throughout the experiment. Peroral immunization resulted in an overall 17-fold median increase in SIgA in milk. Although SIgA1 comprised almost two-thirds of milk SIgA, Strep. mutans whole-cell antibody activity was contained predominantly in the SIgA2 subclass. The difference between the specific activities of anti-Strep. mutans SIgA1 and SIgA2 antibodies compared over time reached the borderline of statistical significance (p = 0.08). The avidity of anti-Strep. mutans antibodies was low in three of four chimpanzees and there was no evidence of affinity maturation. SIgA antibodies from the milk of all four immunized chimpanzees recognized antigen A. In three animals these antibodies were restricted to the SIgA1 subclass and, in one animal, anti-A antibodies were confined to SIgA2. Antibodies from all of the immunized chimpanzees recognized degradation products of antigen B in both the SIgA1 and the SIgA2 subclasses. Only two of four immunized chimpanzees responded to glucosyltransferases and these antibodies were restricted to the SIgA1 subclass. None of the chimpanzees responded to the 74-kDa glucan-binding protein. However, three animals produced SIgA1 antibodies against the 59-kDa glucan-binding protein and two of these also produced SIgA2 antibodies against this protein.

Chlamydial colonization of multiple mucosae following infection by any mucosal route

Chlamydia trachomatis inoculated by any mucosal route colonized multiple murine mucosae and, in most cases, the spleen, liver, and kidneys. Cell-to-cell transmission, systemic dissemination, and autoinoculation of infectious fluids may have contributed to chlamydial spread. Intermucosal trafficking of protective T cells cannot be accurately evaluated by using live chlamydial challenges.

Mucosal vaccination strategies for women

Women were immunized orally, rectally, or vaginally with a recombinant cholera toxin B-containing vaccine to determine which of these mucosal immunization routes generate the greatest levels of antibody in the female genital tract and rectum. ELISA was used to measure concentrations of cholera toxin B-specific IgA and IgG antibody in serum and secretions before and after three immunizations. Each immunization route similarly increased specific IgG in serum and specific IgA in saliva. Only the vaginal route increased IgA antibodies in genital tract secretions and could be shown to induce a local IgG response. However, vaginal immunization failed to produce antibody in the rectum. In a similar fashion, rectal immunization elicited highest concentrations of locally derived IgA and IgG antibody in the rectum but was ineffective for generating antibody in the genital tract. The data suggest that local immunization may induce the greatest immune responses in the female genital tract and rectum of humans.

Specific-antibody-secreting cells in the rectums and genital tracts of nonhuman primates following vaccination

To determine optimal strategies to induce specific-antibody-secreting cells (specific ASC) in the rectal and vaginal mucosae, we immunized monkeys with a prototype mucosal immunogen, cholera toxin (CT), given locally or via gastric or parenteral administration. Repeated rectal or vaginal CT immunizations induced strong mucosal and systemic ASC responses. The mucosal responses were, however, confined to the immunization sites and comprised high levels of both specific antitoxin immunoglobulin A (IgA) and IgG. Large numbers of specific IgA and IgG ASC were detected in cell suspensions from dissociated genital and rectal tissues, demonstrating local accumulation of effector B cells at these sites. Intragastric immunization with CT did not per se give rise to cervicovaginal or rectal ASC responses but did prime for a rectal IgA ASC response to local booster immunization. Both rectal and vaginal immunizations also induced circulating blood IgG ASC and IgA ASC. In conclusion, these results show that local administration of antigen to the rectal or vaginal mucosa results in higher ASC responses than systemic or distant mucosal delivery. Furthermore, both the vaginal and the rectal mucosae can serve as inductive sites for systemic ASC responses. These observations should be relevant to the development of vaccines against sexually transmitted diseases such as that caused by human immunodeficiency virus.

Differential kinetics and distribution of antibodies in serum and nasal and vaginal secretions after nasal and oral vaccination of humans

Although nasal vaccination has emerged as an interesting alternative to systemic or oral vaccination, knowledge is scarce about the immune responses after such immunization in humans. In the present study, we have compared the kinetics and organ distribution of the antibody responses after nasal and oral vaccination. We immunized female volunteers nasally or orally with cholera toxin B subunit (CTB) and determined the specific antibody levels in serum and nasal and vaginal secretions, as well as the number of circulating antibody-secreting cells, before immunization and 1, 2, 3, 6, and 26 weeks thereafter. Nasal vaccination induced 9-fold CTB-specific immunoglobulin A (IgA) and 56-fold specific IgG antibody increases in nasal secretions, whereas no significant IgA increase was seen after oral vaccination. Both oral and nasal vaccination resulted in 5- to 6-fold CTB-specific IgA and 20- to 30-fold specific IgG increases in vaginal secretions. Strong serum responses to CTB were also induced by both routes of vaccination. A notable difference between nasal and oral vaccination was that the nasal route elicited a specific antibody response with a later onset but of much longer duration than did the oral route. We conclude from this study that the nasal route is superior to the oral route for administering at least nonliving vaccines against infections in the upper respiratory tract, whereas either oral or nasal vaccination might be used for eliciting antibody responses in the female genital tract.

Mucosal immunogenicity elicited in mice by oral vaccination with phosphorylcholine encapsulated in poly (D,L-lactide-co-glycolide) microspheres

Poly(D,L-lactide-co-glycolide) microspheres loaded with phosphorylcholine linked to thyroglobulin (PC-Thyr) as protein carrier were prepared. The entrapment efficiency reached 80% when the initial protein:polymer ratio was 1:8. Ninety-four percent of the loaded microspheres had a diameter < or = 10 microns. The encapsulation process did not alter PC-Thyr absorbance nor PC antigenic reactivity. Oral administration of these microspheres induced a specific IgA response in intestinal, pulmonary and vaginal secretions, as well as a strong specific systemic immune response in female Balb/c mice. This suggests the need to explore further the potential ability of PC-Thyr loaded microspheres to protect against infections caused by PC-bearing microorganisms which invade or colonize different mucosal sites.

Vaginal immunization with recombinant gram-positive bacteria

PROBLEM

Many viral and bacterial pathogens enter the body through the genital mucosa. Therefore, one of the major goals of a vaccine against sexually transmitted diseases (STDs) should be to induce an immune response in the genital mucosa capable of controlling the entry of the pathogen. Our approach for the development of vaccines against STDs is based on the use of nonpathogenic Gram-positive bacteria as live vaccine vectors.

METHOD OF STUDY

Recombinant Gram-positive bacteria expressing vaccine antigens were constructed using genetic systems developed in our laboratory. Balb/c mice and Cynomolgus monkeys were inoculated by the vaginal route and vaginal samples were collected using absorbent wicks. Colonization was evaluated by the presence of recombinant bacteria in the vaginal samples. Local and systemic immune responses were studied.

RESULTS

We have developed genetic systems for the expression of heterologous antigens on the surface of the human commensals Streptococcus gordonii and Lactobacillus spp. Both S. gordonii and L. casei stably colonized the murine vagina after a single inoculum. Vaginal colonization of mice with recombinant strains of S. gordonii, expressing human papillomavirus (HPV) and human immunodeficiency virus (HIV) antigens, induced antigen-specific vaginal immunoglobulin A (IgA) and serum IgG. Local and systemic immune responses also were detected in monkeys immunized intravaginally with recombinant S. gordonii.

CONCLUSION

The results obtained indicated that the approach of using colonizing Gram-positive bacteria as live vectors has a great potential for the development of vaccines against STDs.

Antibodies and antibody-secreting cells in the female genital tract after vaginal or intranasal immunization with cholera toxin B subunit or conjugates

We studied the antibody response including antibody-secreting cells (ASC) in the female genital tract of mice after mucosal immunizations with the recombinant B subunit of cholera toxin (rCTB) perorally, intraperitoneally, vaginally, and intranasally (i.n.). The strongest genital antibody responses as measured with a novel perfusion-extraction method were induced after vaginal and i.n. immunizations, and these routes also gave rise to specific immunoglobulin A (IgA) and IgG ASC in the genital mucosa. Specific ASC in the iliac lymph nodes, which drain the female genital tract, were seen only after vaginal immunization. Progesterone treatment increased the ASC response in the genital tissue after all mucosal immunizations but most markedly after vaginal immunization. We also tested rCTB as a carrier for human gamma globulin (HGG) and the effect of adding cholera toxin (CT) as an adjuvant for the induction of systemic and genital antibody responses to HGG after vaginal and i.n. immunizations. Vaginal immunizations with HGG conjugated to rCTB resulted in high levels of genital anti-HGG antibodies whether or not CT was added, while after i.n. immunization the strongest antibody response was seen with the conjugate together with CT. In summary, vaginal and i.n. immunization give rise to a specific mucosal immune response including ASC in the genital tissue, and vaginal immunization also elicits ASC in the iliac lymph nodes. We have also shown that rCTB can act as an efficient carrier for a conjugated antigen for induction of a specific antibody response in the genital tract of mice after vaginal or i.n. immunization.

Characterization of B-cell responses to Chlamydia trachomatis antigens in humans with trachoma

The circulating B-cell responses to Chlamydia trachomatis of 60 children and 34 adults in The Gambia were characterized in a cross-sectional study of different grades of trachoma, using the enzyme-linked immunospot (ELISPOT) assay. Antibody-secreting cells (ASCs) specific to chlamydial major outer membrane protein (MOMP), heat shock protein 60, and whole elementary bodies were detected in children with no evidence of ocular disease, and the immunoglobulin (IgA) response was significantly increased in those with follicular trachoma. In marked contrast, children with the most intense ocular inflammation paradoxically had an almost completely absent B-cell response of all isotypes and to all chlamydial antigens, but with normal serum IgG and IgA responses, which was even lower than in the group with no ocular inflammation. Adults with or without evidence of trachomatous scarring had equivalent numbers of circulating B cells, principally IgA, to all chlamydial antigens. Plasmablasts secreting antibodies to MOMP were present in the urine of children in the absence of urogenital infection detectable by PCR, and relative numbers were 8 to 25 times higher than in blood, suggesting site-specific homing within a common mucosal immune system. These results suggest that ELISPOT assay of ongoing B-cell responses detects suppression of chlamydia-specific IgA ASCs during the proinflammatory response to ocular chlamydial infection seen in intense trachoma, which may play a role in tissue damage leading to trachomatous scarring.

B-cell-deficient mice develop complete immune protection against genital tract infection with Chlamydia trachomatis

We evaluated the ability of mice made genetically deficient for B cells to resolve a primary infection and to develop protective immunity against vaginal challenge with a human isolate of Chlamydia trachomatis bacteria. The B-cell-deficient microMT mice cleared a primary ascending infection with similar or faster kinetics compared with wild-type mice. The presence of chlamydial inclusion bodies and the degree of inflammation in the upper genital tract was comparable and showed similar kinetics in microMT as in wild-type mice. Following resolution of the primary infection the mice were challenged by 100 ID50 of live bacteria and the level of protection and the extent of local inflammation was assessed. Strikingly, all microMT mice, as well as most of the wild-type mice, demonstrated complete immune protection with no bacterial shedding. While high titres of chlamydia-specific antibodies were stimulated locally and systemically in wild-type mice, no antibodies were detected in microMT mice. However, in both strains, immunohistochemical analysis of the upper genital tract demonstrated the presence of large numbers of CD4+ T cells and increased levels of interferon-gamma (IFN-gamma)-producing cells. The results unequivocally demonstrate that antibodies are not required for full protection to develop against ascending infection with a high dose of C. trachomatis in the female genital tract. Our study confirms the notion that cell-mediated immunity, in particular that owing to CD4+ T helper I (Th1)-type cells, is critical for host resistance against C. trachomatis in mice.

Commensal bacteria as vectors for mucosal vaccines against sexually transmitted diseases: vaginal colonization with recombinant streptococci induces local and systemic antibodies in mice

There is a need to develop vaccines to control the spread of sexually transmitted diseases (STDs). Novel immunization strategies that elicit a mucosal immune response in the genital tract, may show improved protection by preventing or at least limiting entry of the pathogenic micro-organism. However, it has proven difficult to obtain a local immune response in the vaginal mucosa. Our approach is based on the use of recombinant bacteria capable of colonizing mucosal surfaces as live vaccine vectors. The human commensal Streptococcus gordonii, engineered to express the E7 protein of human papillomavirus type 16, was used for intravaginal immunization of mice. A single inoculum of recombinant bacteria was sufficient to establish colonization of the murine vagina and therefore induce papillomavirus-specific vaginal IgA and serum IgG. Evidence that mucosal colonization with recombinant commensal bacteria can induce a local immune response in the female genital tract represents a significant step toward the development of new vaccines against STDs.

Intranasal vaccination of humans with recombinant cholera toxin B subunit induces systemic and local antibody responses in the upper respiratory tract and the vagina

Forty-five volunteers were vaccinated twice intranasally with 10, 100, or 1,000 microg of cholera toxin B subunit (CTB). Blood and nasal and vaginal secretions were collected before and 1 week after the second vaccination from all volunteers, and the specific and total immunoglobulin A (IgA) and IgG titers were determined by enzyme-linked immunosorbent assay. Samples were also taken 6 months (n = 16) and 1 year (n = 14) after the vaccination. The 10- and 100-microg doses were well tolerated by the volunteers, but the 1,000-microg dose induced increased secretions from the nose and repetitive sneezings for several hours. The CTB-specific serum IgA and IgG increased 21- and 7-fold, respectively, 1 week after vaccination with the medium dose and increased 61- and 37-fold, respectively, after the high dose. In nasal secretions the specific IgA and IgG increased 2- and 6-fold after the medium dose and 2- and 20-fold after the high dose, respectively. In vaginal secretions the specific IgA and IgG increased 3- and 5-fold after the medium dose and 56- and 74-fold after the high dose, respectively. The lowest dose did not induce any significant antibody titer increases in serum or in secretions. The specific IgA and IgG levels in secretions were still elevated after 6 months but were decreasing 1 year after the vaccination. These results show that intranasal vaccination of humans with CTB induces strong systemic and mucosal antibody responses and suggest that CTB may be used as a carrier for antigens that induce protective immunity against systemic as well as respiratory and genital infections.

Mucosal immunization with a DNA vaccine induces immune responses against HIV-1 at a mucosal site

Mucosal immunity is the first defense system in protection against mucosal infection by sexually transmitted diseases and subsequent systemic dissemination of infection. Development of vaccines which can induce protective mucosal immunity would have great promise for preventing sexually transmitted diseases including AIDS. DNA vaccines have recently shown certain advantages over other types of vaccines in safety and elicitation of specific immune responses. We have hypothesized that direct delivery of a DNA plasmid coding the HIV-1 envelope (pcMN160) via mucosal routes will stimulate mucosal immunity against HIV-1. The expression of DNA plasmid inoculated intravaginally was detected in various tissues. Intravaginal inoculation of pcMN160 elicits production of vaginal immunoglobulins which specifically bind to the HIV-1 envelope and neutralize HIV-1 infectivity in vitro. These results indicate the feasibility of inducing mucosal immunity following mucosal inoculation of DNA vaccines. When coupled with systemic inoculation of appropriate DNA constructs, effective mucosal and systemic immunity may be generated.

Monoclonal immunoglobulin A antibody to the major outer membrane protein of the Chlamydia trachomatis mouse pneumonitis biovar protects mice against a chlamydial genital challenge

In order to analyze the protective role that IgA may play in a chlamydial infection two IgA monoclonal antibodies (mAb), MoPn 4-2 and MoPn 13-2, were raised against the major outer membrane protein (MOMP) of the Chlamydia trachomatis mouse pneumonitis (MoPn) biovar. mAb MoPn 4-2 was found to be serovar specific while mAb MoPn 13-2 was species specific. mAb MoPn 4-2 recognized a surface exposed conformational epitope as shown by its ability to bind to native EBs and nonreduced MOMP while failing to bind to heat and trypsin treated EBs, to reduced MOMP and to synthetic MOMP peptides. In contrast, mAb MoPn 13-2 recognized a nonconformational epitope since it was able to bind treated EBs, to reduced MOMP and to the synthetic peptide MTTWNPTISGSGI located in variable domain 4 of the MOMP. Both mAbs agglutinated intact EBs and had in vitro neutralizing activity. However, mAb MoPn 4-2 had a 20-fold higher in vitro neutralizing ability when compared to mAb MoPn 13-2 (50% neutralization at 5 micrograms ml-1 vs 100 micrograms ml-1). In an in vitro in vivo infectivity assay, mAb MoPn 4-2 protected mice against infertility when C. trachomatis MoPn elementary bodies were preincubated with the mAb before inoculation. In addition, passive transfer of mAb MoPn 4-2 resulted in significant protection as measured by a decrease in the number of mice infected, and in the intensity and duration of vaginal shedding. These results support previous findings suggesting that IgA antibodies can play a role in protection against a chlamydial infection, and further encourage work to develop vaccination strategies that elicit mucosal immunity.

Comparison of the oral, rectal, and vaginal immunization routes for induction of antibodies in rectal and genital tract secretions of women

To determine which mucosal immunization routes may be optimal for induction of antibodies in the rectum and female genital tract, groups of women were immunized a total of three times either orally, rectally, or vaginally with a cholera vaccine containing killed Vibrio cholerae cells and the recombinant cholera toxin B (CTB) subunit. Systemic and mucosal antibody responses were assessed at 2-week intervals by quantitation of CTB-specific antibodies in serum and in secretions collected directly from mucosal surfaces of the oral cavity, rectum, cervix, and vagina with absorbent wicks. The three immunization routes increased levels of specific immunoglobulin G (IgG) in serum and specific IgA in saliva to similar extents. Rectal immunization was superior to other routes for inducing high levels of specific IgA and IgG in rectal secretions but was least effective for generating antibodies in female genital tract secretions. Only vaginal immunization significantly increased both specific IgA and specific IgG in both the cervix and the vagina. In addition, local production of CTB-specific IgG in the genital tract could be demonstrated only in vaginally immunized women. Vaginal immunization did not generate antibodies in the rectum, however. Thus, generation of optimal immune responses to sexually transmitted organisms in both the rectal and the genital mucosae of women may require local immunization at both of these sites.

Genital tract infection with Chlamydia trachomatis fails to induce protective immunity in gamma interferon receptor-deficient mice despite a strong local immunoglobulin A response

CD4+ T cells have been found to play a critical role in immune protection against Chlamydia trachomatis infection. Since both humoral and cell-mediated antichlamydial immunity have been implicated in host protection, the crucial effector functions provided by the CD4+ T cells may rely on Th1 or Th2 functions or both. In the present study, we evaluated the development of natural immunity following vaginal infection with C. trachomatis serovar D in female gamma interferon receptor-deficient (IFN-gammaR-/-) mice with a disrupted Th1 effector system. We found that in comparison with wild-type mice, the IFN-gammaR-/- mice exhibited a severe ascending primary infection of prolonged duration which stimulated almost 10-fold-stronger specific local immunoglobulin A (IgA) and IgG responses in the genital tract. Following resolution of the primary infection and despite the augmented antibody responses to chlamydiae, the IFN-gammaR-/- mice were completely unprotected against reinfection, suggesting that local antibodies play a subordinate role in host protection against chlamydial infection. Immunohistochemical analysis of frozen sections of the genital tract revealed many CD4+ T cells in the IFN-gammaR-/- mice, with a dominance of interleukin 4-containing cells in mice following resolution of the secondary infection. However, in contrast to the findings with wild-type mice, the typical clusters of CD4+ T cells were not found in the IFN-gammaR-/- mice. Few and similarly distributed CD8+ T cells were observed in IFN-gammaR-/- and wild-type mice. Whereas chlamydia-infected macrophages from wild-type mice had no inclusion bodies (IB) and produced significant amounts of nitric oxide (NO) in the presence of IFN-gamma, macrophages from IFN-gammaR-/- mice contained many IB but no NO. These results indicate that CD4+ Th1 cells and IFN-gamma, rather than local antibodies, are critical elements in host immune protection stimulated by a natural ascending C. trachomatis infection in the female genital tract.

Intranasal immunization induces long-term protection in mice against a Chlamydia trachomatis genital challenge

In an attempt to confer long-term protective immunity, BALB/c female mice were immunized intranasally with 10(4) inclusion-forming units (IFU) of the Chlamydia trachomatis mouse pneumonitis biovar (MoPn). Animals were subsequently challenged in the ovarian bursa with 10(5) C. trachomatis MoPn IFU at 60, 120, or 180 days post-intranasal immunization. Two control groups were included in the study. One control was sham immunized and mock challenged, and another group was sham immunized and challenged with 10(5) C. trachomatis MoPn IFU. Vaginal cultures were collected at regular intervals following the intrabursal challenge. In comparison with the sham-immunized mice, the animals that were intranasally immunized with C. trachomatis had significant protection, as shown by a reduction in the number of animals that had positive vaginal cultures and by a decrease in the intensity and length of the shedding. Furthermore, histopathological characterization of the genital tract following challenge, in the three groups of mice, showed a minimal inflammatory infiltrate in the C. trachomatis-immunized animals, when compared with the sham-immunized control group. Subsequently, the three groups of female mice that were challenged at 60, 120 and 180 days postimmunization were mated at 6 weeks following the challenge. Overall, in the mice intranasally immunized with C. trachomatis the fertility rates and the number of embryos were similar to those in the sham-immunized and mock-challenged group. In contrast, there was a significant increase in infertility in the groups of mice that were sham immunized and C. trachomatis challenged. In conclusion, intranasal immunization with C. trachomatis induces long-term protection against a genital challenge as shown by a decrease in the infection and infertility rates when compared with sham-immunized animals. Thus, this model may help to characterize the parameters of the immune response that are important in maintaining long-term protection and may aid in identifying the antigenic determinants involved in eliciting protection.

Immunity to reinfection and immunization of male guinea pigs against urethral infection with the agent of guinea pig inclusion conjunctivitis

BACKGROUND AND OBJECTIVES

There is little information available on immunity of males to chlamydial infection after recovering from a primary urethral infection or after immunization with chlamydial antigen. The guinea pig model of genital infection using the chlamydial agent of guinea pig inclusion conjunctivitis was utilized to evaluate the protective immune response in these circumstances.

GOAL

To determine whether immunity to reinfection develops after a primary urethral infection and whether immunity develops as a result of immunization with inactivated chlamydiae.

STUDY DESIGN

Groups of five male guinea pigs each in two separate experiments were infected in the urethra with chlamydiae and challenged with a fresh inoculum at either 30, 75, or 150 days after infection. The course of the challenge infection was then determined. Similarly, guinea pigs were immunized subcutaneously with ultraviolet-inactivated chlamydial elementary bodies and the course of urethral infection was determined when inoculated 2 weeks after immunization.

RESULTS

Male guinea pigs were highly resistant to reinfection after a primary urethral infection. Animals that were immunized with inactivated chlamydiae generally became infected upon challenge, but the intensity of the infection was markedly reduced.

CONCLUSIONS

Male guinea pigs possess protective mechanisms that make them more resistant to repeat chlamydial genital infection for a longer period of time than is seen in female guinea pigs. In addition, immunization of males with inactivated chlamydial antigen by a parenteral route is able to elicit a protective response to urethral infection with chlamydiae.

The immunobiology and immunopathology of chlamydial infections

Chlamydiae are obligate intracellular bacterial pathogens of eukaryotic cells responsible for a wide variety of important human and animal infections. In humans, chlamydial infections are generally localised to superficial epithelial or mucosal surfaces, are frequently asymptomatic and may persist for long periods of time if untreated, inducing little protective immunity. Nevertheless, neutralising antibodies of limited efficacy are produced against the main chlamydial outer envelope protein, while gamma interferon (IFN gamma) is chlamydiastatic and paradoxically may play a role both in chlamydial persistence and in protective immunity. Delayed hypersensitivity responses to chlamydiae caused by repeated or persistent infection are thought to be important in the development of the severe scarring sequelae characteristic of cicatricial trachoma and of chronic salpingitis. Chlamydial heat shock proteins bearing close homology with their human equivalents may be major targets for immunopathological responses and their expression is upregulated in IFN gamma induced persistent infection. C. pneumoniae, a common cause of acute respiratory infection in humans, may persist in coronary arteries and is strongly implicated as a risk factor in atherosclerosis and in acute myocardial infarction. This paper reviews the immunology and immunopathology of chlamydial infections in the context of the unique biology of this fascinating but challenging group of organisms.

Immunization of mice with HPV vaccinia virus recombinants generates serum IgG, IgM, and mucosal IgA antibodies

To assess the utility of vaccinia virus recombinants in the development of an immune response against HPV capsid antigens, 5-week-old C57B16 female mice were administered either purified HPV 1 capsids produced by a vaccinia virus recombinant or the recombinant vaccinia virus itself. Animals were boosted at Week 4 with either agent. Mice developed a serum IgG antibody response in all the administration protocols that was directed mainly against native L1 epitopes. Mice injected initially with the vaccinia virus recombinant and boosted with purified capsids had a higher titer antibody response (P = 0.024) with more mice responding to a greater extent. All mice produced a serum IgM response that preceded the IgG response by approximately 2 weeks and lasted 1-3 weeks. The IgM response was directed against native L1 epitopes. Although no serum IgA was detected, IgA could be detected in vaginal secretions of mice that were immunized or boosted with the vaccinia virus vector. These results indicate that an extensive humoral immune response to HPV can be elicited using vaccinia virus recombinants.

A new computer model for estimating the impact of vaccination protocols and its application to the study of Chlamydia trachomatis genital infections

We describe a new computer model for studying the impact of vaccination protocols on the prevalence of disease. This state transition model uses two parameters, the forward rate and the cure rate, that are derived from epidemiological data to compute the percentage of individuals infected in the population. The cure rate is the percentage of individuals that are cured within one time step (which in this study is one year) and the forward rate is used to calculate the number of new infections due to transmission. The forward rate and the cure rate are incorporated into an update function that has the property that if the vaccination efficacy is 0%, or no vaccination is applied, then the percentage of individuals infected stays constant. We present computer simulations of this model designed to assess the influence of two variables on the prevalence of Chlamydia trachomatis infection in a study population. More specifically, we determined the effect of vaccines with efficacies ranging from 50% to 100% and we analysed the impact on the population for vaccines efficacious for periods of 10, 20 and 40 years. The results of the computer simulation show that even the least efficacious vaccination programme rapidly decreases the prevalence of C. trachomatis infection in the population. On the other hand, a vaccine that is efficacious for a period of only 1 year had minimal impact on the prevalence of the disease in the total population.

Lipid matrix-based vaccines for mucosal and systemic immunization

For more than a decade our laboratories have been combining concepts in biochemistry, virology, and immunology in order to develop a conceptual basis for vaccine design. Our long-term goals have been to construct simple and well-defined immunogens that would stimulate specific immune responses in vivo. Using this approach, we hypothesized that it should be possible to define the structural and biochemical parameters of an immunogen that are necessary and sufficient to stimulate designated effector arms of the immune system. Through the use of covalently coupled peptide complexes, we have been able to define minimal requirements for the induction of humoral immune responses (Mannino et al., 1992). This represents a significant advance in eliciting an immune response to peptides, because it requires only peptides and phospholipids in the absence of additional adjuvants. It is different from the previous use of peptides and liposomes since here the peptides are covalently linked to a hydrophobic anchor and integrated into the phospholipid complex, rather than passively adsorbed or encapsulated. The presentation of peptide as part of a peptide-phospholipid complex (in contrast to encapsulation or nonspecific absorption) may be more similar to the natural presentation of an epitope in the context of an in vivo antigenic challenge. This technology also allows us to incorporate B and Th epitopes in a number of forms--as a single peptide, as two peptides in the same liposome, or as a peptide with viral glycoproteins in the same liposome. These data also demonstrate that Th epitopes do not have to be covalently linked to the B-cell epitope in order to provide help for that epitope. The implications of the data reported here are significant for both basic science and applied technologies. In basic science, the peptide-phospholipid complexes are potentially useful for analyzing the cooperative effects of B- and T-cell epitopes in the in vivo immune response. Since the peptide-phospholipid complexes are totally synthetic and highly immunogenic, they may be constructed in any formulation required to answer questions on the roles of B and T cells in promoting an immune response. Furthermore, since the number of antigenic sites is limited only by the number of peptides included in the peptide-phospholipid complexes, these constructs may be useful in producing antisera or monoclonal antibodies to weakly antigenic regions of a large protein, since the lack of antigenic competition should enhance the immunogenicity of these regions. Clinically, this technology will expand the potential for subunit vaccines.(ABSTRACT TRUNCATED AT 400 WORDS)

Protection against infertility in a BALB/c mouse salpingitis model by intranasal immunization with the mouse pneumonitis biovar of Chlamydia trachomatis

Female BALB/c mice were immunized intranasally with the mouse pneumonitis biovar of Chlamydia trachomatis and subsequently challenged in the ovarian bursa (C. trachomatis immunized, C. trachomatis challenged). Two groups of mice served as controls. One group was sham immunized intranasally with mock-infected HeLa 229 cell extracts and was challenged in the ovarian bursa with C. trachomatis MoPn (sham immunized, C. trachomatis challenged). The second control group was sham immunized and not challenged (sham immunized, nonchallenged). Before challenge, the C. trachomatis-immunized, C. trachomatis-challenged animals mounted a significant humoral response as shown by high immunoglobulin G (IgG), IgM, and IgA levels and high levels of neutralizing antibodies in serum and moderate IgG and IgA titers in vaginal secretions. Reactivity by Western blot (immunoblot) to the lipopolysaccharide, 30-, 40- (major outer membrane protein), and 60-kDa cysteine-rich proteins and 75- and 100-kDa chlamydial components could be demonstrated. However, reactivity to the 60-kDa heat shock protein was only observed 22 days after challenge. In addition, this group of animals mounted a significant immune response to chlamydial antigens, as shown by a lymphocyte proliferation assay, compared with the sham-immunized nonchallenged mice. After intrabursal challenge, there was no C. trachomatis shedding from the vagina in the C. trachomatis-immunized, C. trachomatis-challenged animals, while 63% of the sham-immunized, C. trachomatis-challenged mice had a positive C. trachomatis culture. In addition, histological sections from the genital tract showed, at 2 weeks postchallenge, a marked acute inflammatory reaction in the sham-immunized, C. trachomatis-challenged animals while in the C. trachomatis-immunized, C. trachomatis-challenged mice there was minimal inflammatory reaction. When the animals were mated, only 12% of the mice from the sham-immunized, C. trachomatis-challenged mice were fertile. In contrast, 94 and 80% of the sham-immunized, nonchallenged and C. trachomatis-immunized, C. trachomatis-challenged mice, respectively, were fertile.

New strategies for using mucosal vaccination to achieve more effective immunization

Future progress in vaccination will be significantly advanced by application of emerging technologies for immunization of mucosal surfaces. It should now be possible to maximize the antigenicity of many vaccines and facilitate their interaction with appropriate lymphoid tissues to induce protective cellular and humoral responses. Mucosal vaccines requiring no more than two doses are achievable with current technologies. Living vaccines have been among the most promising candidates for mucosal vaccination, but with few exceptions their promise is still to be realized. Development of new microencapsulated delivery systems and adjuvants has made non-living vaccines reasonable options for mucosal immunization. To be practical, such vaccines should be developed as combined agent vaccines, possibly deliverable by multiple mucosal routes. Although strategies to be used for specific mucosal vaccines will depend upon a number of factors pertinent to the disease agent, in concept an adjuvant administered with inactivated but maximally antigenic pathogens or their recombinant adhesive subcomponents could prove to be among the more practical mucosal vaccine options for use globally.

Induction of specific immunoglobulin A in the small intestine, colon-rectum, and vagina measured by a new method for collection of secretions from local mucosal surfaces

In order study patterns of local antibody responses following mucosal immunization of mice via different routes, a method for collection of secretions directly from mucosal surfaces was developed. Mice were immunized on days 0, 10, 17, and 24 by administration of cholera toxin into the oral cavity, stomach, colon-rectum, or vagina. At sacrifice on day 32, absorbent wicks were placed in the oral cavity and, via an applicator tube, into the vagina and distal colon-rectum and along the entire small intestine after flushing of luminal contents. Protein was quantitatively extracted from wicks, and specific anti-cholera toxin immunoglobulin A (IgA) and IgG were measured by enzyme-linked immunosorbent assay. Concentrations of specific IgA in secretions at various mucosal sites were dramatically influenced by the route of immunization. Oral immunization effectively induced IgA in saliva, and the intragastric route was optimal for induction of IgA in the small intestine. High levels of specific IgA appeared on the colonic-rectal mucosal surface only after rectal delivery of antigen. Oral, gastric, and rectal immunizations also produced distant responses in the vagina. Following vaginal immunization, however, neither local nor distant IgA responses were detected. These results suggest that vaccines intended for protection of colonic-rectal and vaginal mucosal surfaces might best be administered by the rectal route.

Some aspects of the immune response of koalas (Phascolarctos cinereus) and in vitro neutralization of Chlamydia psittaci (koala strains)

Western-blot analysis was used to study the reaction of koala antisera, two specific polyclonal antibodies and one monoclonal antibody, with chlamydial antigens in koalas infected with Chlamydia psittaci. The koala sera recognized four C. psittaci surface antigens, corresponding to the major outer membrane protein (39.5 kDa), 31 kDa protein, 18 kDa protein and lipopolysaccharide. The S25-23 LPS specific monoclonal antibody inhibited chlamydial infection (55-67%) with both koala strains (type I and type II). Both koala antiserum and rabbit polyclonal antibodies against either type of chlamydia significantly reduced the number of infected cells resulting from type II infections at a dilution of 1 in 20. Rabbit antiserum against type II was effective in neutralizing infection by type II elementary bodies, but was less effective against type I infection. In addition, no koala antiserum was effective in neutralizing type I infection.

Secretory immune responses to Mycoplasma pulmonis

Formalinized Mycoplasma pulmonis, along with aluminum hydroxide as an adjuvant, was used to subcutaneously immunize rats in the vicinity of the salivary gland to examine the characteristics of the secretory immune response to this pathogen. The induction of specific antibody to this microorganism was detected in serum and the exocrine fluids, namely, saliva and lung lavage fluid. Both immunoglobulin G (IgG) and IgA isotype antibodies were detected in each of these fluids after primary and secondary local immunizations. Serum responses from immunized animals were significantly greater than in the control group, but a dose response was not observed in either IgG or IgA antibody at the dosages selected for immunization. Salivary IgG antibody responses peaked early after both the primary and secondary immunizations, exhibiting a clear dose response. Salivary IgA in immunized groups was significantly greater than that in the control group but displayed little dose-dependent kinetics, and, at the termination of the experiment, this response had not yet peaked. Lung lavage IgG and IgA were minimal after the primary immunization when the antibody was normalized to total protein but displayed dose-dependent kinetics after a secondary challenge. IgG peaked immediately after a secondary challenge, while IgA peak responses were observed only after 20 days. A positive correlation was noted between the serum, saliva, and lung lavage fluid IgGs after both primary and secondary immunizations and only after a secondary challenge for IgA. In this study we were able to elicit a secretory immune response, consisting of both IgG and IgA, which exhibited a dose-dependent characteristic in lung lavage fluid to this immunogen. Additionally, a positive correlation of antibody levels between saliva and lung lavage fluid suggests that saliva could be used as an indicator for monitoring specific antibody to M. pulmonis in lung lavage secretions without requiring invasive, deleterious procedures.