HIV can cross the intact epithelium of genital mucosae via Langerhans cells. Fresh Langerhans cells are known to express CD4 and CCR5. The presence of CXCR4 on the surface of cultured but not freshly isolated Langerhans cells has been described. In the present study, we demonstrate that CXCR4 was expressed by fresh Langerhans cells isolated and purified from epidermis. However, the percentage of Langerhans cells expressing CXCR4 or CCR5 increased during maturation of the cells in culture, especially in the presence of exogenous granulocyte-macrophage colony-stimulating factor. To determine whether CXCR4 was functional, freshly isolated Langerhans cells were infected with HIV LAI, a T-cell-tropic strain, and p24 protein production was measured in culture supernatants. p24 production was observed when infected Langerhans cells were cocultured with SupT1 cells. However, the presence of HIV provirus DNA was evidenced within the infected Langerhans cells by nested PCR. Ultrastructural studies confirmed the formation of syncytia when Langerhans cells were cocultured with SupT1 cells. Preincubation of Langerhans cells with azidothyinidine or SDF-1-alpha, a natural ligand for CXCR4, prevented infection. These data demonstrated that CXCR4 is present on the surface of Langerhans cells freshly isolated from human skin epidermis and that this expression is functional.

Les muqueuses constituent la principale voie de contamination par le virus de l'immunodeficience humaine de type 1 (VIH-1) a la suite de rapports heterosexuels ou homosexuels. Les IGA secretoires constituent la premiere barriere immunologique au niveau des muqueuses ; leur fonction essentielle est d'empecher la colonisation et l'infestation des muqueuses par des agents infectieux. Par ce travail, nous avons montre une profonde alteration fonctionnelle des muqueuses, presente aux differents stades de l'infection a VIH-1. Des IGA secretoires specifiques d'antigenes au contact des muqueuses ont ete frequemment retrouvees dans le serum des patients seropositifs. Les taux d'immunoglobulines et la reponse anticorps dans les lavages broncho-alveolaires et la salive parotidienne etaient nettement diminues, ce qui pourrait expliquer en partie les frequentes pathologies associees aux muqueuses au cours de la maladie. Des IGA secretoires specifiques des antigenes du VIH sont presentes dans les secretions. Les IGA de la salive parotidienne etaient capables de neutraliser une souche virale de laboratoire ainsi qu'un isolat primaire chez certains malades. La neutralisation n'etait pas correlee avec les specificites anti-V3 et anti-eldkwa. L'etude des mecanismes et l'identification des cibles de la neutralisation presentent un grand interet pour l'elaboration d'un vaccin par voie muqueuse

ABSTRACTAn enzyme-linked immunosorbent assay and a Western blot analysis were developed to study the antibody response toPneumocystis cariniiin serum and bronchoalveolar lavage fluid from 27 human immunodeficiency virus 27 (HIV)-infected patients withP. cariniipneumonia (Pcp), 32 patients without Pcp, and 51 HIV-negative controls. Urea was used for the correct dilution of epithelial lining fluid, and albumin was used to evaluate transudation from plasma for the assessment of local production of antibodies toP. carinii. By contrast with those of immunoglobulin G (IgG), IgA responses toP. cariniiwere increased in serum from HIV-positive patients compared to negative controls. Local production of antibodies toP. carinii, especially IgA, was decreased in patients with Pcp. In a study of 10 patients of each group, IgG and IgA responses to gp116 fromP. cariniiwere lower in patients with Pcp than in other groups. These results suggest that, in addition to alveolar macrophages, local antibodies may play a role in host defense againstP. carinii.

Infection with human immunodeficiency virus type 1 (HIV-1) has been shown to elicit a serum antibody response with neutralizing activity against T cell line-adapted HIV strains and primary HIV-1 isolates. Mucosal surfaces are the primary route of HIV-1 infection. Evidence is presented here for the presence of HIV-neutralizing antibodies in secretions. Infection of mucosal cells with HIV stimulates systemic and mucosal immune responses and results in the generation of neutralizing antibodies. Serum IgG and IgA neutralize HIV-1MN infection of susceptible T cell lines; serum IgG inhibits more effectively. Mucosal IgA purified from parotid saliva of HIV-1-seropositive individuals could neutralize both a T cell line-adapted strain and a primary isolate. The neutralizing activity of IgA was not directed against the anti-third-variable-loop or the anti-ELDKWA epitope. Thus, the specificity of mucosal IgA for HIV-1 neutralization epitopes remains to be determined and may provide insight into development of a mucosal vaccine.

Thirty-two children with Henoch–Schönlein purpura with or without renal symptoms were studied to characterize the IgA hyperglobulinemia observed in the serum of most patients. It was shown that only the IgA1 subclass concentration was increased. Secretory IgA and IgA to gliadin levels were frequently increased in serum, with a good correlation between them. Circulating IgA immune complexes were detected often and contained high activity to gliadin. In contrast, IgA activity to tetanus toxoid did not change. We failed to show any differences in renal involvement. These data suggest that elevation of serum IgA in Henoch–Schönlein purpura is due in part to a disturbance of the gut mucosal immune system, and the presence of circulating IgA immune complexes with dietary antigens can be postulated but cannot explain the occurrence of urinary symptoms.

In order to study the humoral immune defences in the respiratory tract during HIV-1 infection, we measured the levels, local productions and anti-HIV and antibacterial activities of IgG and IgA in the bronchoalveolar lavage fluid (BALF) and serum of 61 adult patients with severe HIV infection and of 56 HIV- controls. Albumin was used as the serum transudation factor. The increase of immunoglobulin levels in the serum of HIV-infected patients was confirmed. The IgG level was also increased in epithelial lining fluid (ELF), whereas the total IgA level was unchanged and secretory IgA (SIgA) level was decreased. The ELF/serum immunoglobulin ratios suggested that the IgG present in ELF resulted mainly from transudation, in contrast to SIgA, which was synthesized locally in controls but greatly diminished in HIV-infected patients. IgG to HIV-1 could be detected in BALF of all the patients, but IgA to HIV-1 only in 30% of patients. BAL IgG reacted more consistently and with a broader array of HIV-1 antigens than did IgA. BAL IgA, when present in samples, reacted primarily with viral envelope antigens. Because IgA specificities to some HIV-1 antigens were detected more intensively by BAL than by serum immunoglobulins, we conclude that the mucosal immune response is distinct from that in serum. IgG antibody activity to Streptococcus pneumoniae was decreased in HIV-infected patients' sera, and IgA antibody activities to S. pneumoniae and to Pseudomonas aeruginosa were decreased in ELF in HIV-infected patients.

Paired sera and parotid saliva from 75 HIV-1-infected patients, divided in three equal groups with CD4+ cell counts > 500, 200-500 and < 200/mm3, respectively, were analysed for IgG, IgA and secretory IgA (sIgA) concentrations and for IgG and IgA antibody directed to HIV-1. Twenty-nine age-matched HIV-subjects were used as controls. In serum the concentrations of immunoglobulins were significantly increased in HIV-infected subjects compared with controls, and a progressive increase of IgA and sIgA was noticed while the CD4+ cell count decreased. In contrast, concentrations of IgA and sIgA were not different in parotid saliva between the four subject groups. By an ELISA test directed towards HIV-1 proteins, 73 of the 75 serum specimens from the HIV-infected subjects (97%) and 43 of the corresponding saliva (57%) were found positive for specific IgA antibodies to HIV-1, with an even distribution among the three groups of patients. By Western blotting multiple specificities of IgA to HIV-1 proteins were not frequently found in patients. By contrast, in spite of an IgG concentration in saliva about 100 times lower than that of IgA, reactivities were significantly higher for IgG than for IgA antibodies, especially to env and to pol HIV-1 products. Altogether, these data suggest that the regulation of IgA production in HIV-infected subjects is independent in serum and in parotid saliva. This imbalance of IgA/IgG antibodies to HIV-1 at the mucosal level appears to be a specific feature of HIV-1 infection, and may raise important issues in terms of local protection after immunization.

This study was performed in 77 HIV1 seropositive adult patients to characterise the IgA hyperglobulinaemia seen in the serum during the course of HIV infection. It was shown that both IgA1 and IgA2 subclass concentrations were simultaneously increased but the IgA1 increase was predominant. Secretory IgA (SIgA) concentration was significantly increased and IgA activity to gliadin, bovine serum albumin, and casein could be detected and was correlated with SIgA concentration. In contrast, IgA activity to cytomegalovirus and to tetanus toxoid did not correlate with total IgA concentration. These data suggest the presence of IgA from gut mucosal origin in the serum of these patients. Hyper IgA was inversely correlated with the CD4+ cell number. The increase of all parameters studied varied according to the total IgA concentration in the serum but was also directly related to the stage of immune deficiency in patients with hyper IgA.

This study was performed in 27 HIV-1+ children to characterize the IgA hyperglobulinaemia observed in the serum during the course of HIV-1 infection. By contrast with serum IgG, which increased very early, IgA elevation was related to the decrease of CD4+ cell percentage. It was demonstrated that IgA1 subclass increased selectively. Secretory IgA (SIgA) and IgA and IgG activity to gliadin, bovine serum albumin (BSA) and at a lower level to casein could be detected in the serum at the early stages of HIV infection, but SIgA levels and IgA activity to gliadin further increased during the course of immunodeficiency. By contrast, IgA and IgG activity to tetanus toxoid did not change. These data demonstrate that the hyper IgA, closely related to the degree of immunodeficiency, could be due in part to a disturbance of the gut mucosal immune system. Moreover, impaired intestinal immunity seems to appear very early, and to progress during the course of paediatric HIV-1 infection.

Serum specimens from 66 HIV-1-infected subjects were tested by ELISA for the presence of IgA antibodies to HIV-1: 44 samples were found positive and 37 were confirmed by immunoblot. In these subjects, the presence of anti-HIV IgA antibodies was studied in relation to the total count of circulating CD4+ lymphocytes and to the level of serum IgA. A significative correlation (P < 0.03) was found between the absence of IgA to the subunit p68 of the reverse transcriptase and a count of CD4+ cell < 400/mm3 or total IgA level over 4.25 g/l. The same pattern was observed for the IgA antibodies to the p52 subunit but the association was just not significant (P < 0.07). No significant decrease was noted for the IgA directed towards the other proteins of HIV-1, especially the products of the gag gene.