Biomedical subjects

Cristiana Iosef

Publications and source records attributed to Cristiana Iosef.

9 recordsLinked to original sources

PubMed2006

High titers of circulating maternal antibodies suppress effector and memory B-cell responses induced by an attenuated rotavirus priming and rotavirus-like particle-immunostimulating complex boosting vaccine regimen.

We investigated maternal antibody (MatAb) effects on protection and immune responses to rotavirus vaccines. Gnotobiotic pigs were injected intraperitoneally at birth with pooled serum from sows hyperimmunized with human rotavirus (HRV); control pigs received no sow serum. Pigs with or without MatAbs received either sequential attenuated HRV (AttHRV) oral priming and intranasal boosting with VP2/VP6 virus-like particle (VLP)-immunostimulating complex (ISCOM) (AttHRV/VLP) or intranasal VLP-ISCOM prime/boost (VLP) vaccines at 3 to 5 days of age. Subsets of pigs were challenged at 28 or 42 days postinoculation with virulent Wa HRV to assess protection. Isotype-specific antibody-secreting cell (ASC) responses to HRV were quantitated by enzyme-linked immunospot assay to measure effector and memory B-cell responses in intestinal and systemic lymphoid tissues pre- and/or postchallenge. Protection rates against HRV challenge (contributed by active immunity and passive circulating MatAbs) were consistently (but not significantly) lower in the MatAb-AttHRV/VLP groups than in the corresponding groups without MatAbs. Intestinal B-cell responses in the MatAb-AttHRV/VLP group were most suppressed with significantly reduced or no intestinal immunoglobulin A (IgA) and IgG effector and memory B-cell responses or antibody titers pre- and postchallenge. This suppression was not alleviated but was enhanced after extending vaccination/challenge from 28 to 42 days. In pigs vaccinated with nonreplicating VLP alone that failed to induce protection, MatAb effects differed, with intestinal and systemic IgG ASCs and prechallenge memory B cells suppressed but the low intestinal IgA and IgM ASC responses unaffected. Thus, we demonstrate that MatAbs differentially affect both replicating and nonreplicating HRV vaccines and suggest mechanisms of MatAb interference. This information should facilitate vaccine design to overcome MatAb suppression.

Animals↗

PubMed2005

Low titer maternal antibodies can both enhance and suppress B cell responses to a combined live attenuated human rotavirus and VLP-ISCOM vaccine.

We investigated effects of low titer (Lo) circulating MatAb on protection and immunogenicity of attenuated (Att) human rotavirus (HRV) priming and 2/6-virus-like particle (VLP)-immunostimulating complex (ISCOM) boosting (AttHRV/VLP) or VLP-ISCOM alone vaccines. LoMatAb had both enhancing and suppressing effects on B cell responses, depending on tissue, antibody isotype and vaccine. Differential effects of LoMatAb on IgA responses in different tissues suggest that LoMatAb did not suppress induction of IgA effector and memory B cells but impaired homing of these cells to secondary lymphoid or effector tissues, reducing IgA antibody secreting cells and antibodies at these sites. The AttHRV/VLP vaccine partially overcame LoMatAb suppression, conferred moderate protection against virulent HRV (as measured by reduced viral shedding and diarrhea) and represents a new candidate for rotavirus vaccines for both humans and animals.

Adjuvants, Immunologic↗

PubMed2005

Mucosal and systemic antibody responses and protection induced by a prime/boost rotavirus-DNA vaccine in a gnotobiotic pig model.

A live rotavirus prime/DNA boost vaccine regimen was evaluated in a gnotobiotic pig model for human rotavirus (HRV) diarrhea. Plasmid DNA expressing rotavirus inner capsid VP6 was administered to pigs intramuscularly (IM) twice after oral priming with attenuated (Att) Wa strain HRV (AttHRV/VP6DNA2x). Other groups included: (1) VP6 DNA IM 2x then AttHRV orally (VP6DNA2x/AttHRV); (2) VP6 DNA IM 3x (VP6DNA3x) and controls. Significant protection (70%) against virus shedding, but lower protection against diarrhea (30%) was achieved only in the AttHRV/VP6DNA2x group after challenge (virulent Wa HRV). The other vaccines (VP6DNA2x/AttHRV and VP6DNA3x) were less effective. Higher protection rates were associated with the highest IgA antibody responses induced by the AttHRV/VP6DNA2x regimen. Interestingly, the VP6 DNA vaccine, although not effective when administered alone, boosted neutralizing and VP4 antibody titers in pigs previously primed with AttHRV, possibly mediated by cross-reactive T helper cells.

Administration, Oral↗

PubMed2004

Magnitude of serum and intestinal antibody responses induced by sequential replicating and nonreplicating rotavirus vaccines in gnotobiotic pigs and correlation with protection.

A sequential mucosal prime-boost vaccine regimen of oral attenuated (Att) human rotavirus (HRV) priming followed by intranasal (i.n.) boosting with rotavirus protein VP2 and VP6 rotavirus-like particles (2/6-VLPs) has previously been shown to be effective for induction of intestinal antibody-secreting cell (ASC) responses and protection in gnotobiotic pigs. Because serum or fecal antibody titers, but not intestinal ASC responses, can be used as potential markers of protective immunity in clinical vaccine trials, we determined the serum and intestinal antibody responses to this prime-boost rotavirus vaccine regimen and the correlations with protection. Gnotobiotic pigs were vaccinated with one of the two sequential vaccines: AttHRV orally preceding 2/6-VLP (VLP2x) vaccination (AttHRV/VLP2x) or following VLP2x vaccination (VLP2x/AttHRV) given i.n. with a mutant Escherichia coli heat-labile toxin (mLT) as adjuvant. These vaccines were also compared with three i.n. doses of VLP+mLT (VLP3x) and one and three oral doses of AttHRV (AttHRV1x and AttHRV3x, respectively). Before challenge all pigs in the AttHRV/VLP2x group seroconverted to positivity for serum immunoglobulin A (IgA) antibodies. The pigs in this group also had significantly higher (P < 0.05) intestinal IgA antibody titers pre- and postchallenge and IgG antibody titers postchallenge compared to those in the other groups. Statistical analyses of the correlations between serum IgM, IgA, IgG, and virus-neutralizing antibody titers and protection demonstrated that each of these was an indicator of protective immunity induced by the AttHRV3x and the AttHRV/VLP2x regimens. However, only IgA and not IgM or IgG antibody titers in serum were highly correlated (R2 = 0.89; P < 0.001) with the corresponding isotype antibody (IgA) titers in the intestines among all the vaccinated groups, indicating that the IgA antibody titer is probably the most reliable indicator of protection.

Administration, Intranasal↗

PubMed2003

Disease-causing SAP mutants are defective in ligand binding and protein folding.

The X-linked lymphoproliferative (XLP) syndrome is caused by mutations or deletions in the SH2D1A gene that encodes an SH2 domain protein named SH2D1A or SAP. The identification of a number of missense mutations within the protein's SH2 domain, each of which can directly cause disease, provides a unique opportunity to investigate the function of an interaction protein module, SH2, in the pathogenesis of XLP. We show here that SAP mutants found in XLP patients are defective in binding its physiological ligands signaling lymphocyte activating molecule (SLAM), a co-receptor in T cell activation, and Fyn, a Src family protein tyrosine kinase. Consequently, these mutants are deficient in signaling through the SLAM receptor. This is reflected by compromised abilities for the mutants to recruit Fyn to SLAM and to activate Fyn, by reduced phosphorylation of the receptor, and by deficiencies for the mutants in blocking binding of SHP-2 to SLAM. Furthermore, all mutants examined are defective in protein folding as manifested by their significantly reduced melting temperatures upon thermal denaturation, compared to that of SAP. Taken together, these results suggest that defects in ligand binding, receptor signaling, and protein folding collectively contribute to the loss of function for disease-causing SAP mutants.

Amino Acid Sequence↗

PubMed2002

Dual functional roles for the X-linked lymphoproliferative syndrome gene product SAP/SH2D1A in signaling through the signaling lymphocyte activation molecule (SLAM) family of immune receptors.

The X-linked lymphoproliferative (XLP) syndrome gene encodes a protein named SAP or SH2D1A that is composed of a single Src homology 2 (SH2) domain. Two models have been proposed for its function in lymphocyte signaling. One postulates that it acts as an inhibitor of interactions between the phosphatase SHP-2 and the immune receptor SLAM. The other suggests that it functions as an adaptor to promote the recruitment of a kinase, FynT, to SLAM. Here, we provide evidence in support of both roles for SAP. Using an array of peptides derived from the SLAM family of receptors, we demonstrate that SAP binds with comparable affinities to the same sites in these receptors as do the SH2 domains of SHP-2 and SHIP, suggesting that these three proteins may compete against one another in binding to a given SLAM family receptor. Furthermore, in vitro and in vivo binding studies indicate that SAP is capable of binding directly to FynT, an interaction mediated by the FynT SH3 domain. In cells, FynT was shown to be indispensable for SLAM tyrosine phosphorylation, which, in turn, was drastically enhanced by SAP. Because SAP also blocked the recruitment of SHP-2 to SLAM in these cells, we propose a dual functional role for SAP in SLAM signaling by acting both as an adaptor for FynT and an inhibitor to SHP-2 binding. The physiological relevance of the dual functional role for SAP is underscored by the observation that disease-causing SAP mutants exhibited significantly reduced affinities to both FynT and SLAM.

Amino Acid Sequence↗

PubMed2002

Systemic and intestinal antibody secreting cell responses and protection in gnotobiotic pigs immunized orally with attenuated Wa human rotavirus and Wa 2/6-rotavirus-like-particles associated with immunostimulating complexes.

The undesirable side effects and variable efficacy of some oral live rotavirus vaccines in infants have necessitated alternative vaccine approaches. We evaluated a recombinant RFVP2/WaVP6 rotavirus-like-particle (2/6VLP) oral vaccine, using an immunostimulating complex (ISCOM) matrix as adjuvant, in a gnotobiotic (Gn) pig model of human rotavirus (HRV) disease. The 2/6VLPs adhered to the ISCOM-matrix (2/6VLP-ISCOM ) and were antigenic, but they failed to induce protection. However, when combined with attenuated (Att) HRV for oral priming, the 2/6VLP-ISCOM vaccine was effective as a booster and induced partial protection against virulent Wa HRV. The 250 microg 2/6VLP dose was more effective than 100 microg. The highest mean numbers of IgA antibody secreting cells evaluated by ELISPOT in intestinal lymphoid tissues were in pigs receiving AttHRV+2/6VLP-ISCOM or three doses of AttHRV and were associated with the highest protection rates.

Administration, Oral↗

PubMed2002

Systemic and intestinal antibody responses to NSP4 enterotoxin of Wa human rotavirus in a gnotobiotic pig model of human rotavirus disease.

Antibody responses to the Wa human rotavirus (HRV) nonstructural protein NSP4, a viral enterotoxin, were evaluated in neonatal gnotobiotic (Gn) pigs. Gn pigs were inoculated orally with one dose of 10(5) fluorescent focus units (FFU) of virulent Wa HRV (HRV-V), to mimic natural infection, or with three doses of 5 x 10(7) FFU attenuated Wa HRV (HRV-A) at 10-day intervals, to mimic oral attenuated rotavirus vaccines, or they were mock inoculated (mock). Subsets of pigs were challenged with 10(6) FFU of virulent Wa HRV at post-inoculation day 28 (PID 28). Post-challenge, the HRV-V pigs were completely protected against diarrhea and virus shedding, whereas the HRV-A pigs had a 50% protection rate against diarrhea and a 67% protection rate against virus shedding. All mock-inoculated pigs shed virus and had diarrhea post-challenge. Isotype antibody titers to NSP4 were compared in serum and intestinal contents, at post-inoculation day (PID) 28 and at post-challenge day 7 (PCD 7/PID 35) by indirect ELISA, using purified recombinant NH2-6xHis-tagged NSP4 of virulent Wa HRV. Pre-challenge, both the HRV-V and HRV-A-inoculated pigs had similar moderate titers of serum IgG antibodies to NSP4. However, only the HRV-V-inoculated pigs developed detectable serum and intestinal IgA antibody titers to NSP4 pre-challenge, compared with the HRV-A-inoculated pigs. The mock-inoculated pigs had no IgM, IgA, or IgG antibodies to NSP4 pre-challenge. All Wa HRV-inoculated pigs developed low to moderate titers of serum IgM, IgG, and IgA antibodies to NSP4 post-challenge, but the mock-inoculated pigs had only IgM antibodies post-challenge. Both Wa HRV-inoculated groups developed low titers of IgA antibody to NSP4 in the small intestinal contents post-challenge, but titers were 5.8-fold higher in the HRV-V pigs. Our results concur with findings that both rotavirus vaccinated and naturally infected children seroconvert with modest IgG antibodies to NSP4 [Johansen et al. (1999) J Med Virol 59:369-367]. These data suggest that Gn pigs could be a useful model to evaluate serum and intestinal IgA antibodies to NSP4 and their role in protection against HRV infection. Further experiments may clarify whether (1) the NSP4 antibodies detected pre-challenge in the HRV-V pigs contribute to the higher protection rates observed, or (2) the reduced or delayed NSP4 antibody responses of the HRV-A pigs are associated with the lower protection rates in these pigs.

Animals↗

PubMedDate not supplied

Apoptosis in human embryo development: 1. Cerebral cortex.

We investigated the apoptosis at the beginning of human cerebral cortex development, in the 6th week of embryogenesis, Carnegie stages 16 and 17. Attention was focused on the dorsal wall of the telencephalon to the ventricular zone of proliferation and to the postmitotic zone with beginning of neuronal migration. We identified apoptotic cells in tissue sections by propidium iodide staining, TUNEL and immunohistochemistry for Fas(APO-1/CD95). We determined the distribution and the percentage (reported to the propidium iodide stained nuclei) of apoptotic TUNEL-positive and Fas(APO-1/CD95)-positive cells. TUNEL-positive apoptotic cells in the proliferative zone were 20% in stage 16 and 60% in stage 17. TUNEL-positive apoptotic cells in the postmitotic zone were 8% in stage16 and 30% in stage 17. CD95-positive apoptotic cells in the proliferative zone were 5% in stage 16 and 2% in stage 17. There were no CD95-positive cells in the postmitotic zone. We evidentiated the presence of the suicide receptor Fas(APO-1/CD95) only on a small population of apoptotic neuroblasts in the proliferative zone. The differences between apoptotic distribution and receptors in early corticogenesis suggest that different apoptotic pathways drive the selection of neuronal populations.

Journal Article↗