HIV infects activated CD4 ؉ T cells and induces their depletion. Progressive HIV infection leading to AIDS is fueled by chronic immune hyperactivation, mediated by inflammatory cytokines like TNF␣. This has been related to intestinal epithelial damage and microbial LPS translocation into the circulation. Using 11-color flow cytometry, cell sorting, and cell culture, we investigated the numbers and TNF␣ production of fully defined circulating dendritic cell and monocyte populations during HIV-1 infection. In 15 viremic, untreated patients, compared with 8 treated, virologically suppressed patients or to 13 healthy blood donors, circulating CD141 (BDCA-3) ؉ and CD1c (BDCA-1) ؉ dendritic cell counts were reduced. Conversely, CD14 ؉ CD16 ؉؉ monocyte counts were increased, particularly those expressing M-DC8, while classical CD14 ؉؉ CD16 ؊ M-DC8 ؊ monocyte numbers were unchanged. Blood mononuclear cells from viremic patients produced more TNF␣ in response to LPS than those from virologically suppressed patients. M-DC8 ؉ monocytes were mostly responsible for this overproduction. Moreover, M-DC8 ؉ monocytes differentiated in vitro from classical monocytes using M-CSF and GM-CSF, which is increased in viremic patient's plasma. This M-DC8 ؉ monocyte population, which is involved in the pathogenesis of chronic inflammatory diseases like Crohn disease, might thus be considered as a major actor in the immune hyperactivation fueling HIV infection progression. (Blood. 2012;120(11): 2259-2268) IntroductionHIV-1 infection induces the depletion of CD4 ϩ T lymphocytes in blood and lymphoid organs, particularly in the gut-associated lymphoid tissue. [1][2][3] The absence of immune activation during the chronic phase of the infection distinguishes nonprogressive from progressive infections in patients as well as in nonhuman primate models of HIV infection. [4][5][6] Systemic immune activation is correlated to the increased translocation of gut luminal microbial products such as the Gram-negative bacterial lipopolysaccharide (LPS). 7 LPS stimulates the production of proinflammatory cytokines, particularly TNF␣. In HIV-1-infected patients, TNF␣ serum levels increase in correlation with disease progression and drop to normal levels after treatment only in patients with good virologic and immunologic responses. 3,8 By activating the NF-B pathway, TNF␣ induces viral replication in HIV-infected CD4 ϩ T lymphocytes. 3,9 In chronic inflammatory bowel diseases, TNF␣ affects mucosal integrity, leading to microbial product systemic translocation. 10 Granulocyte/macrophage colony-stimulating factor (GM-CSF) and LPS also induce HIV replication in infected myeloid cells. 11,12 GM-CSF and TNF␣ are produced by monocytes and dendritic cells (DCs) after LPS stimulation.During chronic HIV infection, circulating plasmacytoid and myeloid DC (pDC and mDC) numbers are reduced. [13][14][15] Myeloid DCs were mostly studied in HIV-infected patients using CD11c as a marker. Now, they are further subdivided into BDCA-1 ϩ and BDCA-3 ϩ mDC subsets, the latter r...

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The induction of a mucosal immunity provides an additional principle of vaccination by preventing the entry of pathogens in the body. Albeit the fact that intensive research has been conducted on local vaccines, the major mucosal vaccine commercially available for human use remains the oral polio vaccine. We have previously demonstrated that parenteral vaccination in humans with tetanus toxoid (TT) results in a genital immunoglobulin (Ig)G antibody (Ab) response. Here, we show that injections of TT with no adjuvant induces an anti-TT response in the mucosal tissues of normal BALB/c mice. The response is multiregional, involves both IgG and IgA isotypes, and is long-lasting. Similarly, injections of haptens coupled to TT or to other diffusible proteins may induce mucosal Abs. These results led us to immunize normal BALB/c mice with a viral peptide coupled to TT by disulfide bridging. The hapten was a 17 amino acid peptide containing the ELDKWA sequence of human immunodeficiency virus (HIV)-1 gp41. A significant IgG and IgA Ab response to the immunizing peptide was induced in various mucosal tissues despite the presence of a suboptimal Ab response in the spleen. The results indicate that mucosal immunity to peptides that are candidates for human vaccinations may be achieved by parenteral adjuvant-free immunization with peptide coupled to TT. Dr J.-P. Bouvet, INSERM U430, Ho Ãpital Broussais,

To improve the mucosal antibody response against a short amino acid (aa) sequence (ELDKWA) of HIV gp41, we have investigated a construction including this peptide in-line with the Pan DR epitope (PADRE). ELDKWA is a conserved peptide playing a key role in the pathogenicity of HIV transmission. PADRE is a non-natural peptide with multipotential immunogenic properties. The results show striking differences between mucosal and systemic immune systems, with a preferential response of the mucosal organs. In contrast with most mucosal immunizations, the intracellular response persists for over two months after the last injection. This strongly suggests that further investigations of conserved key epitopes from various pathogens may lead to safe and chemically defined mucosal vaccines with synthetic peptides. These candidate vaccines with free peptides may be suitable for mass campaigns even in developing countries.

Secretory immunity protects against mucosal transmission of viruses, as demonstrated with the oral poliovirus vaccine. In a previous study we showed that this immunity could be induced in mice by injection of a fusion peptide consisting of an unnatural peptide-like sequence (PADRE) and a viral epitope (ELDKWASLW). PADRE is a T-helper-cell epitope able to bind most major histocompatibility complex class II molecules of different haplotypes in mice and humans and to increase antibody responses. ELDKWA is a well-known consensual sequence of gp41 involved in a key structure of human immunodeficiency virus (HIV) type 1. Here, the antibody response to the native form of ELDKWA was mainly of the immunoglobulin A isotype and selectively occurred in mucosa. Adjuvants, such as cholera toxin and cytosine polyguanine, were useless and even competed with PADRE for the response. Interestingly, these antibodies were cross-reactive with the three major variants of the epitope, as shown both by direct enzyme-linked immunosorbent assay and by inhibition. This unconventional route of mucosal immunization allows control of the administered dose. The lack of adjuvant and the cross-reactivity of the antibodies increase the safety and the spectrum of the candidate vaccine, respectively. The drug-like nature of the construct suggests further improvements by synthesis of more antigenic sequences. The reasonable cost of short peptides at the industrial level and their purity make this approach of interest for future vaccines against mucosal transmission of HIV or other pathogens.

In a previous study, it was shown that an intramuscular administration of amino acid PADRE-ELDKWA sequence induced a mucosal immune response to a conserved epitope of human immunodeficiency virus in mice. In the same model, here it is shown that this method can be used with a selected peptide from the M protein of group A streptococci. The PADRE-ASREAK sequence was injected in mice by the intramuscular route. Antibodies against M protein were detected in extracts of mucosal tissues and in serum. The repertoire isotypes of serum immunoglobulin G (IgG) and mucosal IgA and IgG antibodies varied, according to the dose of injected peptide. The highest mucosal IgA antibody response was obtained with 0.01 mg of antigen per injection, whereas the systemic IgG antibody response increased with 10 mg of antigen. Mucosal antibody production against streptococci was confirmed by immunofluorescence analysis. These results provide evidence that this novel approach of mucosal vaccination may be of advantage for bacterial systems and suggest a new field of investigation based on synthetic peptide analogues.

Les anticorps des muqueuses comprennent diffé rentes immunoglobulines, principalement desIgA sécrétoires et des IgG locales, qui forment la première ligne de défense immunitaire contre les agents patho gènes. Ils constituent la majeure partie des immuno globulines synthétisées par l'organisme et proviennent principalement du système immunitaire sécrétoire, qui est indépendant du reste du système immunitaire. Ces anticorps agissent par deux mécanismes origi naux : l'exclusion et l'élimination immunes. Ils com prennent des anticorps classiques, induits par l'anti gène, ainsi que des anticorps naturels polyréactifs préimmuns. Les progrès récents dans ce domaine suggèrent de nouvelles approches du problème des vaccinations muqueuses. SUMMARY Properties of mucosal antibodies Mucosal antibodies consist of a variety of mole cules, including secretory IgA and local IgG, involved in the first immune barrier of defence against patho gens. They account for the majority of daily synthe sized imm unoglobulins in the body and mostly depend on the secretory immune system which is independent from its systemic counterpart. Acting by immune exclusion and immune elimination, these immunoglobulins correspond to preimmune polyreactive natural antibodies and to antigen-induced antibodies. Recent progress in this field have sugges ted new approaches of mucosal vaccines preventing the entry of pathogens in the body.