The neutralization epitope(s) of the hepatitis E virus (HEV) was studied by an in vitro neutralization assay using antibodies obtained by immunization of mice with 51 overlapping 30-mer synthetic peptides spanning the region 221-660 amino acids (aa) of the HEV open reading frame 2 encoded protein (pORF2) and 31 overlapping recombinant proteins of different sizes derived from the entire pORF2 of the HEV Burma strain. Antibodies against synthetic peptides and short recombinant proteins of approximately 100 aa did not neutralize HEV, suggesting the HEV neutralization epitope(s) is conformation-dependent. However, one recombinant protein of approximately 400 aa in length comprising the pORF2 sequence at position 274-660 aa as well as all truncated derivatives of this protein containing region 452-617 aa elicited antibodies, demonstrating HEV neutralizing activity. These findings establish for the first time that the minimal size fragment, designated pB166, that can efficiently model the neutralization epitope(s) is 166 aa in length and is located at position 452-617 aa of the HEV pORF2. Additionally, antibodies against pB166 were found to cross-neutralize three different HEV genotypes, suggesting that a common neutralization epitope(s) may exist within the different HEV genotypes. Thus, recombinant proteins constructed in this study may be considered as potential candidates for the development of an HEV subunit vaccine as well as for the development of highly sensitive and specific diagnostic tests.

The IgG and secretory IgA (S-IgA) responses to the HIV-1 envelope (gp160 antigen) were analyzed in the colostrum (Col) and in the cervicovaginal fluid (CVF) of HIV-l-infected women. We show IgG antibodies (Abs) to the recombinant gp160 to be predominant as compared with the corresponding S-IgA isotype. The low level of the S-IgA response cannot be related to a general disturbance of the mucosal-associated Iymphoid tissue (MALT) because the level of a current Ab to a caries-associated antigen from Streptococcus sobrinus was in the normal range in these secretions. The major subclass of IgA to gp160 was of the alpha1 isotype both in Col and in CVF. However, the specific activities of S-IgA1 and S-IgA2 were different when expressed as the ratio of the anti-gp160 related to total Ig of each subclass. Indeed, the specific activity of the S-IgA2 was predominant over S-IgA1 in the Col, whereas the reciprocal results were found in CVF, showing a subcompartmentalization of these secretions. The ability of S-IgA and IgG to block one of the pathways involved in the HIV-1 penetration across mucosa, i.e., transcytosis through epithelial cells, was evaluated using a functional in vitro assay. Both S-IgA and IgG Abs impaired virus transcytosis, irrespective of the level of antigp160 specific activities. However, specific S-IgA was more efficient than IgG. These features suggest that mucosal specific S-IgA to HIV-1 could be relevant in decreasing infectivity of HIV-1 in corporal fluids.

Paired sera and cervicovaginal secretions (CVS) from 30 women infected with human immunodeficiency virus (HIV) type 1 (before AIDS) were analyzed for IgG and IgA antibodies to HIV and for IgG, IgA, and human serum albumin. Subjects were compared with 30 aged-matched healthy controls. In HIV-infected women, cervicovaginal immunoglobulins were markedly increased, and IgG predominated. An increased immunoglobulin transudation was implicated, since cervicovaginal albumin levels were 2.3-fold above those of normal controls. Furthermore, IgG excretion by reference to albumin was increased 1.9-fold, whereas the IgA secretion tended to decrease, suggesting a possible enhanced local IgG synthesis. Mean IgG and IgA anti-HIV antibody titers were, respectively, 30- and 12-fold higher in serum than in CVS, but their mean specific activities were higher in CVS than in serum, suggesting a local synthesis of both isotypes. The IgA antibody response to HIV remained poor compared with the strong IgG response.

density at 492 nm [OD4921) similar to those of the corresponding serum dilutions measured in the same plate. Dilutions of a 3957

The molecular status of Abs in the vaginal fluid is reconsidered as a basis for immunization strategies for women' vaccination against HIV. Analysis of separated immunoglobulins (Igs) shows a large proportion of uncleaved IgG, whereas the low amount of IgA includes SIgA, monomers and fragments. SIgM is at a very low level, while free SC molecules are abundant. In addition to the already documented local synthesis, vaginal IgG contains serum-derived tetanus antitoxins. The IgG could reach the lumen by diffusion, and/or be transported by an Fc receptor-associated mechanism as suggested by the subclass imbalance in favour of the IgG1 isotype. VAginal SIgA contains very low levels of antibodies o the cell-well carbohydrates from a dental caries-associated streptococcus confirming the participation of the secretory immune system. IN addition, the low percentage of IgA2 suggests tha a proportion of vaginal SIgA can also derive from actively transported serum polymers. In agreement with our previous studies showing induction of vaginal tetanus antitoxins by intramuscular immunization, these results are in favour of classical, parenteral vaccinations to induce protection of the human vagina.

No abstract

No abstract

The role of salivary antibodies in protection against cariogenic bacteria is actually a matter of debate. Correlation between caries experience and naturally occurring antibodies was extensively investigated. Comparison of salivary antibodies from 21 caries-resistant and 22 caries-susceptible subjects was carried out by using a new quantitative method. Secretory immunoglobulin A (S-IgA) antibodies to Streptococcus sobninus and Streptococcus sanguis cells were detected in all salivas and at similar levels in both groups. When assayed with two major antigens from S. sobrinus, i.e., protein antigen VI/I and cell wall carbohydrates, only specific activities of antibodies to the protein component were increased (P < 0.001), but this occurred unexpectedly in the caries-susceptible group. Western blot (immunoblot) analysis with the culture supernatant and cell wall proteins from S. sobrinus showed the same antibody specificity in both groups. No selective increase of the protease-resistant S-IgA2 subclass was found, and avidities of antibodies to both antigen I/I and cell wall carbohydrates were similar. Our results demonstrate that naturally induced S-IgA antibodies against S. sanguis, S. sobninus, and the major antigens of the latter are not sufficient to inhibit caries development.