Outer membrane protein of Neisseria meningitidis as a mucosal adjuvant for lipopolysaccharide of Brucella melitensis in mouse and guinea pig intranasal immunization models

Vertebrate and Invertebrate Animal and New In Vitro Models for Studying Neisseria Biology

The history of Neisseria research has involved the use of a wide variety of vertebrate and invertebrate animal models, from insects to humans. In this review, we itemise these models and describe how they have made significant contributions to understanding the pathophysiology of Neisseria infections and to the development and testing of vaccines and antimicrobials. We also look ahead, briefly, to their potential replacement by complex in vitro cellular models.

A Historical Review of Military Medical Strategies for Fighting Infectious Diseases: From Battlefields to Global Health

The environmental conditions generated by war and characterized by poverty, undernutrition, stress, difficult access to safe water and food as well as lack of environmental and personal hygiene favor the spread of many infectious diseases. Epidemic typhus, plague, malaria, cholera, typhoid fever, hepatitis, tetanus, and smallpox have nearly constantly accompanied wars, frequently deeply conditioning the outcome of battles/wars more than weapons and military strategy. At the end of the nineteenth century, with the birth of bacteriology, military medical researchers in Germany, the United Kingdom, and France were active in discovering the etiological agents of some diseases and in developing preventive vaccines. Emil von Behring, Ronald Ross and Charles Laveran, who were or served as military physicians, won the first, the second, and the seventh Nobel Prize for Physiology or Medicine for discovering passive anti-diphtheria/tetanus immunotherapy and for identifying mosquito Anopheline as a malaria vector and plasmodium as its etiological agent, respectively. Meanwhile, Major Walter Reed in the United States of America discovered the mosquito vector of yellow fever, thus paving the way for its prevention by vector control. In this work, the military relevance of some vaccine-preventable and non-vaccine-preventable infectious diseases, as well as of biological weapons, and the military contributions to their control will be described. Currently, the civil-military medical collaboration is getting closer and becoming interdependent, from research and development for the prevention of infectious diseases to disasters and emergencies management, as recently demonstrated in Ebola and Zika outbreaks and the COVID-19 pandemic, even with the high biocontainment aeromedical evacuation, in a sort of global health diplomacy.

The Profile of Immunoglobulin A and Immunoglobulin G Subclasses in Sprague Dawley Rats Experimentally Infected with Brucella abortus Biotype 1

This study measured total serum immunoglobulin A (IgA), immunoglobulin G (IgG)1, IgG2a response against whole cell antigen (WCA), outer membrane protein (OMP), periplasmic protein (PP), cytoplasmic protein (CP), and crude Brucella protein (CBP) of Brucella abortus in experimental brucellosis induced with B. abortus biotype 1 in Sprague Dawley (SD) rats during a 17-week infection period. Six- to 8-week-old SD rats (n = 44) were experimentally infected with 1 × 10⁹ colony forming unit of B. abortus biotype 1 through the intraperitoneal route. Serial serum samples were collected from the rat at 0, 3, 7, 14, 21, 28, 35, 42, 60, 90, and 120 days after inoculation. The sera were tested by enzyme linked immunosorbent assay. We have noticed a very low level and short persistence of IgA antibody in our experiment. The low level and short persistence of IgA antibody suggest that this antibody isotype might not be protective against brucellosis in rats. Both Th1 and Th2 specific immune responses were recorded in our study with the production of IgG1 and IgG2a antibody isotopes, respectively. We noticed significant dominant IgG2a antibody responses over IgG1 responses throughout the experiment (p < 0.001) against WCA and OMP. The mixed Th1 and Th2 dominant immune responses mediated by IgG2a and IgG1 antibody isotypes were observed against CP, PP, and CBP. Data of our study suggest that IgG2a dominant responses in the early stages of disease play the main role in conferring protection against brucellosis and with the progress of disease IgG1 dominant responses were elicited.

Immunoglobulin profiles in acute Brucellosis experimentally induced by Brucella canis in BALB/c mice

This study evaluated profiles of immunoglobulin (Ig; IgA, IgG, IgG1, and IgG2a) response in experimental brucellosis induced with Brucella canis in BALB/c mice during an 8-week infection period. Six- to 8-week-old BALB/c mice (n = 36) were experimentally infected with 1 × 10(9) CFU of B. canis via the intraperitoneal route. Serial serum samples were collected from the mice at 0, 3, 7, 14, 21, 28, 35, 42, 49, and 56 days after inoculation. The sera were tested by the rapid slide agglutination test (RSAT) and 2-mercaptoethanol-RSAT and indirect enzyme-linked immunosorbent assay. Sera tested positive for B. canis by the RSAT and 2-mercaptoethanol-RSAT beginning from 7 days after inoculation until the end of the experiment. The IgA response was detected at 14 days after infection and reached peak levels at 21 days after infection. The IgG antibody responses were detected at 7 days after infection and reached the peak value at 35 days after infection. Data of our study demonstrated IgG2a-dominant responses over IgG1 during the course of infection (p > 0.05).

Intranasal administration of a detoxified endotoxin vaccine protects mice against heterologous Gram-negative bacterial pneumonia

When given passively or elicited actively, antibodies induced by a detoxified Escherichia coli J5 mutant lipopolysaccharide (J5dLPS)-group B meningococcal outer membrane protein (-OMP) vaccine previously protected animals from lethal sepsis. To assess the use of this vaccine for the treatment of Gram-negative bacillary pneumonia, we vaccinated mice, with or without the adjuvant CpG, by intranasal (i.n.) or intraperitoneal (i.p.) routes of administration. Local and systemic IgG levels were 2-3 logs higher following i.p. immunization compared to i.n. However, i.n. immunization elicited both local and systemic IgA, unlike i.p. administration. The addition of CpG to the vaccine, by either route of administration, elicited greater levels of antibody. Intranasal immunization protected mice against lethal heterologous Gram-negative bacillary pneumonia and post-immunization serum and broncho-alveolar lavage fluid mediated enhanced bacterial killing with peritoneal and alveolar macrophages in vitro. We conclude that further studies on the use of J5dLPS-OMP for the prevention of nosocomial pneumonia are warranted.

Oral vaccination: where we are?

As early as 900 years ago, the Bedouins of the Negev desert were reported to kill a rabid dog, roast its liver and feed it to a dog-bitten person for three to five days according to the size and number of bites [1] . In sixteenth century China, physicians routinely prescribed pills made from the fleas collected from sick cows, which purportedly prevented smallpox. One may dismiss the wisdom of the Bedouins or Chinese but the Nobel laureate, Charles Richet, demonstrated in 1900 that feeding raw meat can cure tuberculous dogs - an approach he termed zomotherapy. Despite historical clues indicating the feasibility of oral vaccination, this particular field is notoriously infamous for the abundance of dead-end leads. Today, most commercial vaccines are delivered by injection, which has the principal limitation that recipients do not like needles. In the last few years, there has been a sharp increase in interest in needle-free vaccine delivery; new data emerges almost daily in the literature. So far, there are very few licensed oral vaccines, but many more vaccine candidates are in development. Vaccines delivered orally have the potential to take immunization to a fundamentally new level. In this review, the authors summarize the recent progress in the area of oral vaccines.

Aerosol infection of BALB/c mice with Brucella melitensis and Brucella abortus and protective efficacy against aerosol challenge

Brucellosis is a zoonotic disease with a worldwide distribution that can be transmitted via intentional or accidental aerosol exposure. In order to engineer superior vaccine strains against Brucella species for use in animals as well as in humans, the possibility of challenge infection via aerosol needs to be considered to properly evaluate vaccine efficacy. In this study, we assessed the use of an aerosol chamber to infect deep lung tissue of mice to elicit systemic infections with either Brucella abortus or B. melitensis at various doses. The results reveal that B. abortus causes a chronic infection of lung tissue in BALB/c mice and peripheral organs at low doses. In contrast, B. melitensis infection diminishes more rapidly, and higher infectious doses are required to obtain infection rates in animals similar to those of B. abortus. Whether this difference translates to severity of human infection remains to be elucidated. Despite these differences, unmarked deletion mutants BADeltaasp24 and BMDeltaasp24 consistently confer superior protection to mice against homologous and heterologous aerosol challenge infection and should be considered viable candidates as vaccine strains against brucellosis.

Comparison of protective efficacy of subcutaneous versus intranasal immunization of mice with a Brucella melitensis lipopolysaccharide subunit vaccine

Groups of mice were immunized either subcutaneously or intranasally with purified Brucella melitensis lipopolysaccharide (LPS) or with LPS as a noncovalent complex with Neisseria meningitidis group B outer membrane protein (LPS-GBOMP). Control mice were inoculated with sterile saline. Two doses of vaccine were given 4 weeks apart. Mice were challenged intranasally with virulent B. melitensis strain 16M 4 weeks after the second dose of vaccine. Sera, spleens, lungs, and livers of mice were harvested 8 weeks after challenge. The bacterial loads in the organs were determined by culture on brucella agar plates. Protective efficacy was determined by comparing the clearance of bacteria from organs of immunized mice with the clearance of bacteria from organs of control mice. At 8 weeks postchallenge there was significant protection from disseminated infection of spleens and livers of mice intranasally immunized with either vaccine compared to infection of control mice (P < 0.01). There was no significant difference in clearance of bacteria from the lungs of immunized mice and control mice. However, mice immunized subcutaneously with either LPS or LPS-GBOMP vaccine showed significant protection against infection of the spleen (P < 0.001), liver (P < 0.001), and lungs (P < 0.05). These results show that intranasal immunization of mice with either vaccine provided significant protection against disseminated infection of the spleen and liver but subcutaneous immunization of mice with the vaccines conferred significant protection against infection of the spleen, liver, and lungs.

Contribution of immunological memory to protective immunity conferred by a Bacillus anthracis protective antigen-based vaccine

Protective antigen (PA)-based vaccination is an effective countermeasure to anthrax infection. While neutralizing anti-PA antibody titers elicited by this vaccine serve as good correlates for protection against anthrax (S. Reuveny, M. D. White, Y. Y. Adar, Y. Kafri, Z. Altboum, Y. Gozes, D. Kobiler, A. Shafferman, and B. Velan, Infect. Immun. 69:2888-2893, 2001), no data are available on the contribution of the immunological memory for PA itself to protection. We therefore developed a guinea pig model in which a primary immunization with threshold levels of PA can induce a long-term T-cell immunological memory response without inducing detectable anti-PA antibodies. A revaccination of primed animals with the same threshold PA levels was effective for memory activation, yielding a robust and rapid secondary response. A challenge with a lethal dose (40 50% lethal doses; 2,000 spores) of spores after the booster vaccinations indicated that animals were not protected at days 2, 4, and 6 postboosting. Protection was achieved only from the 8th day postboosting, concomitant with the detection of protective levels of neutralizing antibody titers in the circulation. The practical implications from the studies reported herein are that, as expected, the protective capacity of memory depends on the PA dose used for the primary immunization and that the effectiveness of booster immunizations for the postexposure treatment of anthrax may be very limited when no detectable antibodies are present in primed animals prior to Bacillus anthracis spore exposure. Therefore, to allow for the establishment of memory-dependent protection prior to the expected onset of disease, booster immunizations should not be used without concomitant antimicrobial treatment in postexposure scenarios.

Pathologic changes associated with brucellosis experimentally induced by aerosol exposure in rhesus macaques ( Macaca mulatta )

OBJECTIVE

To develop an aerosol exposure method for induction of brucellosis in rhesus macaques (Macaca mulatta).

ANIMALS

10 adult rhesus macaques.

PROCEDURE

8 rhesus macaques were challenge exposed with 10(2) to 10(5) colony-forming units of Brucella melitensis 16M by use of an aerosol-exposure technique, and 2 served as control animals. All macaques were euthanatized 63 days after challenge exposure. Gross and microscopic lesions, bacterial burden in target organs, and histologic changes in tissues were evaluated.

RESULTS

Grossly, spleen weights were increased in exposed macaques, compared with spleen weights in control macaques. Histologically, there was inflammation in the liver, kidneys, spleen, testes, and epididymides in exposed macaques. The spleen and lymph nodes had increased numbers of lymphohistiocytic cells. Morphometrically, the spleen also had an increased ratio of white pulp to red pulp. Areas of hepatitis and amount of splenic white pulp increased with increasing exposure dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Pathologic findings in rhesus macaques after aerosol exposure to B melitensis are similar to those observed in humans with brucellosis.

IMPACT FOR HUMAN MEDICINE

These results may aid in the development of a vaccine against brucellosis that can be used in humans.

Protection of mice against brucellosis by intranasal immunization with Brucella melitensis lipopolysaccharide as a noncovalent complex with Neisseria meningitidis group B outer membrane protein

Intranasal immunization of mice with purified Brucella melitensis lipopolysaccharide (LPS) as a noncovalent complex with Neisseria meningitidis group B outer membrane protein (GBOMP) elicited a high-titer anti-LPS systemic antibody response and a significant mucosal antibody response. The anti-LPS immunoglobulin G (IgG) antibody was predominantly of the IgG1 subtype, although there was some response of the IgG2a, IgG2b, and IgG3 subtypes. The antibody titer remained high for 16 weeks postimmunization. Immunized mice and sham-immunized control mice were challenged intranasally with 10(4) CFU of virulent B. melitensis strain 16 M 4 weeks after the second dose of vaccine. The numbers of bacteria in lungs, livers, and spleens at 3 days, 9 days, and 8 weeks postchallenge were determined. Bacteria were found in lungs of all mice on day 3, but there was no disseminated infection of liver or spleen. By day 9, 40% of the mice had infected spleens and livers. At 8 weeks postchallenge, spleens of 25 of 62 immunized mice were infected, compared to 61 of 62 control mice (P < 0.0001). The livers of 12 of 43 immunized mice were infected, compared to 22 of 36 control mice (P = 0.005). In contrast, the lungs of 26 of 46 immunized mice were still infected, compared to 27 of 44 control mice. The numbers of bacterial CFU in lungs of immunized and control animals were identical. These studies show that intranasal immunization with B. melitensis LPS-GBOMP subunit vaccine significantly protects mice against intranasal challenge with virulent B. melitensis. Vaccination reduces bacterial dissemination to spleen and liver but has no effect on the course of lung infection.

Bacteriologic and histologic features in mice after intranasal inoculation of Brucella melitensis

OBJECTIVE

To characterize effects of intranasal inoculation of virulent Brucella melitensis strain 16M in mice.

ANIMALS

Female Balb/c mice, 6 to 8 weeks old.

PROCEDURE

Studies were designed to elucidate gross morphologic lesions, bacterial burden in target organs, and histologic changes in tissues following experimental intranasal inoculation of mice with B melitensis 16M, which could be used to characterize a model for testing vaccine efficacy.

RESULTS

Measurable splenomegaly was evident at 3 and 7 weeks after inoculation. A demonstrable increase in splenic colony-forming units (CFU) from infected mice increased over time with increasing dose when comparing inocula of 10(3), 10(4), and 10(5) CFU. Recovery of brucellae from the lungs was possible early in infection with 10(1), 10(3), and 10(5) CFU, but only the group inoculated with 10(5) CFU consistently yielded quantifiable bacteria. At a dose of 10 CFU, few organisms were located in the spleen. Bacteria were recovered up to 140 days after inoculation in mice given 10(3) CFU. At an inoculum of 10(5) CFU, bacterial counts were highest early in infection. Histologic examination of tissues revealed an increase in white pulp and marginal zone in the spleen and lymphohistiocytic hepatitis.

CONCLUSION AND CLINICAL RELEVANCE

Changes in the spleen and liver increased with increases in dose and with increased time following intranasal inoculation with B melitensis 16M. Surprisingly, histologic changes were not observed in the lungs of inoculated mice.

Differential biological and adjuvant activities of cholera toxin and Escherichia coli heat-labile enterotoxin hybrids

Two bacterial products that have been demonstrated to function as mucosal adjuvants are cholera toxin (CT), produced by various strains of Vibrio cholerae, and the heat-labile enterotoxin (LT) produced by some enterotoxigenic strains of Escherichia coli. Although LT and CT have many features in common, they are clearly distinct molecules with biochemical and immunologic differences which make them unique. The goal of this study was to determine the basis for these biological differences by constructing and characterizing chimeric CT-LT molecules. Toxin gene fragments were subcloned to create two constructs, each expressing the enzymatically active A subunit of one toxin and the receptor binding B subunit of the other toxin. These hybrid toxins were purified, and the composition and assembly of CT A subunit (CT-A)-LT B subunit (LT-B) and LT A subunit (LT-A)-CT B subunit (CT-B) were confirmed. Hybrids were evaluated for enzymatic activity, as measured by the accumulation of cyclic AMP in Caco-2 cells, and the enterotoxicity of each toxin was assessed in a patent-mouse assay. The results demonstrated that LT-A-CT-B induces the accumulation of lower levels of cyclic AMP and has less enterotoxicity than either wild-type toxin or the other hybrid. Nonetheless, this hybrid retains adjuvant activity equivalent to or greater than that of either wild-type toxin or the other hybrid when used in conjunction with tetanus toxoid for intranasal immunization of BALB/c mice. Importantly, the ability of LT to induce a type 1 cytokine response was found to be a function of LT-A. Specifically, LT-A-CT-B was able to augment the levels of antigen-specific gamma interferon (IFN-gamma) and interleukin 5 to levels comparable to those achieved with native LT, while CT-A-LT-B and native CT both produced lower levels of antigen-specific IFN-gamma. Thus, these toxin hybrids possess unique biological characteristics and provide information about the basis for differences in the biological activities observed for CT and LT.

Impaired control of Brucella melitensis infection in Rag1-deficient mice

After intranasal inoculation, Brucella melitensis chronically infects the mononuclear phagocyte system in BALB/c mice, but it causes no apparent illness. Adaptive immunity, which can be transferred by either T cells or antibody from immune to naive animals, confers resistance to challenge infection. The role of innate, non-B-, non-T-cell-mediated immunity in control of murine brucellosis, however, is unknown. In the present study, we documented that BALB/c and C57BL/6 mice had a similar course of infection after intranasal administration of 16M, validating the usefulness of the model in the latter mouse strain. We then compared the course of infection in Rag1 knockout mice (C57BL/6 background) (referred to here as RAG-1 mice) which have no B or T cells as a consequence of deletion of Rag1 (recombination-activating gene 1), with infection in normal C57BL/6 animals after intranasal administration of B. melitensis 16M. C57BL/6 mice cleared brucellae from their lungs by 8 to 12 weeks and controlled infection in the liver and spleen at a low level. In contrast, RAG-1 mice failed to reduce the number of bacteria in any of these organs. From 1 to 4 weeks after inoculation, the number of splenic bacteria increased from 2 to 4.5 logs and remained at that level. In contrast to the consistently high numbers of brucellae observed in the spleens, the number of bacteria rose in the livers sampled for up to 20 weeks. Immunohistologic examination at 8 weeks after infection disclosed foci of persistent pneumonia and large amounts of Brucella antigen in macrophages in lung, liver, and spleen in RAG-1, but not C57BL/6, mice. These studies indicate that T- and B-cell-independent immunity can control Brucella infection at a high level in the murine spleen, but not in the liver. Immunity mediated by T and/or B cells is required for clearance of bacteria from spleen and lung and for control of bacterial replication in the liver.

Intranasal vaccination of mice against infection with Mycobacterium tuberculosis

The intranasal (i.n.) route of immunisation, has recently been of active interest in endeavours to improve the efficacy of vaccination against a number of respiratory infections. Here, we examined the outcome of tuberculous infection in BALB/c mice. I.n. application of the BCG-Pasteur strain was found to be highly protective against challenge infection with the pathogenic H37Rv strain given after a 4-week interval, reflected by the 100-fold reduction of CFUs in both lungs and spleens. Vaccination with the recombinant PstS-1 antigen and cholera toxin significantly protected against the challenge given 10 days later, but only marginally after 12 weeks. Histological examination showed, that i.n. vaccination abrogated the confluent infiltration of lungs with inflammatory cells, which surrounds the granulomas in H37Rv challenged control mice. In conclusion, the strong protection demonstrated by BCG suggests that the i.n. route of vaccine delivery deserves further attention toward improving vaccination against tuberculosis.

Immunization against potential biological warfare agents

The intentional release of biological agents by belligerents or terrorists is a possibility that has recently attracted increased attention. Law enforcement agencies, military planners, public health officials, and clinicians are gaining an increasing awareness of this potential threat. From a military perspective, an important component of the protective pre-exposure armamentarium against this threat is immunization. In addition, certain vaccines are an accepted component of postexposure prophylaxis against potential bioterrorist threat agents. These vaccines might, therefore, be used to respond to a terrorist attack against civilians. We review the development of vaccines against 10 of the most credible biological threats.

Bacterial toxins as mucosal adjuvants

The use of mucosally administered killed bacteria or viruses as vaccines has a number of attractive features over the use of viable attenuated organisms, including safety, cost, storage and ease of delivery. Unfortunately, mucosally administered killed organisms are not usually effective as vaccines. The use of LT(R192G), a genetically detoxified derivative of LT, as a mucosal adjuvant enables the use of killed bacteria or viruses as vaccines by enhancing the overall humoral and cellular host immune response to these organisms, especially the Th1 arm of the immune response. With this adjuvant, protective responses equivalent to those elicited by live attenuated organisms can be achieved with killed organisms without the potential side effects. These findings have significant implications for vaccine development and further support the potential of LT(R192G) to function as a safe, effective adjuvant for mucosally administered vaccines. There are a number of unresolved issues regarding the use of LT and CT mutants as mucosal adjuvants. Both active-site and protease-site mutants of LT and CT have been constructed and adjuvanticity reported for these molecules in various animal models and with different antigens. There needs to be a side-by-side comparison of CT, LT, active-site mutants, protease-site mutants and recombinant B subunits regarding the ability to induce specific, targeted immunological outcomes as a function of route of immunization and nature of the co-administered antigen. Those side-by-side comparisons have not been carried out and there is a substantial body of evidence indicating that the outcomes may very well be different. With that information, vaccine strategies could be designed employing the optimum adjuvant/antigen formulation and route of administration for a variety of bacterial and viral pathogens. Also lacking is an understanding of the underlying cellular and intracellular signaling pathways activated by these different molecules and an understanding of the mechanisms of adjuvanticity at the cellular level. These are important issues because they take us beyond the phenomenological observations of "enhanced immunity" to a more clear understanding of the mechanisms of adjuvant activity.

Immunogenicity of intranasally administered meningococcal native outer membrane vesicles in mice

Colonization of the human nasopharyngeal region by Neisseria meningitidis is believed to lead to natural immunity. Although the presence of bactericidal antibody in serum has been correlated with immunity to meningococcal disease, mucosal immunity at the portal of entry may also play an important role. This study was undertaken to examine in mice the possibility of safely using native outer membrane vesicles (NOMV) not exposed to detergent as an intranasal (i.n.) vaccine. The mucosal and systemic responses of mice to intranasal and intraperitoneal (i.p.) vaccination with NOMV were compared over a range of doses from 0.1 to 20 microgram. Intranasal vaccination of mice with NOMV induced a strong systemic bactericidal antibody response, as well as a strong local immunoglobulin A immune response in the lung as determined by assay of lung lavage fluid by enzyme-linked immunosorbent assay and lung antibody secreting cells by enzyme-linked immunospot assay. However, 8- to 10-fold-higher doses of NOMV were required i.n. compared to i.p. to elicit an equivalent bactericidal antibody response in serum. Some NOMV vaccine was aspirated into the lungs of mice during i.n. immunization and resulted in an acute inflammatory response that peaked at 1 to 2 days postimmunization and was cleared by day 7. These results indicate that i.n. delivery of meningococcal NOMV in mice is highly effective in eliciting the production of both a mucosal immune response and a systemic bactericidal antibody response.

Identification and characterization of a 14-kilodalton Brucella abortus protein reactive with antibodies from naturally and experimentally infected hosts and T lymphocytes from experimentally infected BALB/c mice

A low-molecular-weight recombinant Brucella abortus protein reactive with antibodies from a variety of naturally and experimentally infected hosts and T lymphocytes from experimentally infected mice was identified and given the designation BA14K. The gene encoding BA14K was cloned and characterized, and the predicted amino acid sequence of this immunoreactive protein showed no significant homology with previously described proteins. Sequences homologous to the cloned fragment encoding BA14K were identified by Southern blot analysis of genomic DNAs from representatives of all of the currently recognized Brucella species. Studies employing BA14K should contribute to our efforts to better understand the antigenic specificity of protective immunity to brucellosis.

HIV-1 Neutralizing Antibodies in the Genital and Respiratory Tracts of Mice Intranasally Immunized with Oligomeric gp160

Because mucosal surfaces are a primary route of HIV-1 infection, we evaluated the mucosal immunogenicity of a candidate HIV-1 vaccine, oligomeric gp160 (o-gp160). In prior studies, parenteral immunization of rabbits with o-gp160 elicited broad neutralizing serum Ab responses against both T cell line-adapted HIV-1 and some primary HIV-1 isolates. In this study, nasal immunization of mice with o-gp160, formulated with liposomes containing monophosphoryl lipid A (MPL), MPL-AF, proteosomes, emulsomes, or proteosomes with emulsomes elicited strong gp160-specific IgG and IgA responses in serum as well as vaginal, lung, and intestinal washes and fecal pellets. The genital, respiratory, and intestinal Abs were determined to be locally produced. No mucosal immune responses were measurable when the immunogen was given s.c. Abs from sera and from vaginal and lung washes preferentially recognized native forms of monomeric gp120, suggesting no substantial loss in protein tertiary conformation after vaccine formulation and mucosal administration. Inhibition of HIV-1MN infection of H9 cells was found in sera from mice immunized intranasally with o-gp160 formulated with liposomes plus MPL, proteosomes, and proteosomes plus emulsomes. Formulations of o-gp160 with MPL-AF, proteosomes, emulsomes, or proteosomes plus emulsomes elicited HIV-1MN-neutralizing Ab in lung wash, and formulations with proteosomes, emulsomes, or proteosomes plus emulsomes elicited HIV-1MN-neutralizing Ab in vaginal wash. These data demonstrate the feasibility of inducing both systemic and mucosal HIV-1-neutralizing Ab by intranasal immunization with an oligomeric gp160 protein.