Long-lasting chronic high load carriage of Epstein-Barr virus is more common in young pediatric renal transplant recipients.

BACKGROUND: Epstein-Barr virus (EBV) infections can induce post-transplant lymphoproliferative disorder (PTLD). A chronic high load (CHL), as indicated by long-term high EBV DNA levels after transplantation, has been associated with an enhanced risk of PTLD. We aimed to evaluate incidence, time of occurrence, risk factors, and outcome of EBV CHL carrier state after pediatric renal transplantation. METHODS: A retrospective study of 58 children aged 1-17 years (median 10), who underwent renal transplantation between January 2004 and June 2017 at a single medical center. EBV IgG antibodies in serum were analyzed before and yearly after transplantation. EBV DNA in whole blood were analyzed weekly for the first 3 months post-transplant, monthly up to 1 year and then at least once yearly. CHL was defined as EBV DNA ≥ 4.2 log10 Geq/ml in > 50% of the samples during ≥ 6 months. RESULTS: At transplantation, 31 (53%) patients lacked EBV IgG and 25 (81%) of them developed primary EBV infection post-transplant. Of the 27 seropositive patients, 20 (74%) experienced reactivation of EBV. Altogether, 14 (24%) children developed CHL, starting at a median of 69 days post-transplant and lasting for a median time of 2.3 years (range 0.5-6.5), despite reduction of immunosuppression. Patients with CHL were younger and 11/14 were EBV seronegative at transplantation. No child developed PTLD during median clinical follow-up of 7.8 years (range 0.7-13). CONCLUSIONS: CHL was frequent, long lasting, and occurred mainly in young transplant recipients. The absence of PTLD suggests that monitoring of EBV DNA to guide immunosuppression was effective.

Long-term study showed that vaccination protected paediatric renal transplant recipients from life-threatening varicella zoster virus.

AIM: Renal transplant patients are particularly susceptible to highly contagious diseases due to their reduced immunity. We studied transplant recipients to gauge their varicella zoster virus (VZV) serology status over time and the outcome of any VZV infections. METHOD: This retrospective study comprised 85 children who underwent renal transplants in Gothenburg, Sweden, from 1986 to 2014, at a mean age of eight (1-18) years. The children's medical records were reviewed and 47 had the VZV infection pre-transplant and 38 had been vaccinated pre-transplant. Clinical outcomes were available for 85 children and serology results for 72. RESULTS: At transplantation, the VZV seropositivity rate was 50% in the vaccination group and 94% in the infection group and the antibody titres were significantly lower in the vaccination group (p = 0.031). During the median follow-up period of five years post-transplant, 28% of the vaccinated children and 97% of the infection group remained seropositive and the varicella infection affected eight children: one in the infection group and seven in the vaccination group. The herpes zoster was observed in two children in the infection group. CONCLUSION: This study demonstrated that VZV vaccination protected from symptomatic infections to a lesser extent than natural infection, but provided effective protection from life-threatening disease.

Induction of long term mucosal immunological memory in humans by an oral inactivated multivalent enterotoxigenic Escherichia coli vaccine.

UNLABELLED: We have evaluated the capacity of an oral multivalent enterotoxigenic Escherichia coli (ETEC) vaccine (MEV) to induce mucosal immunological memory. MEV consists of four inactivated E. coli strains over-expressing the major colonization factors (CFs) CFA/I, CS3, CS5 and CS6 and the LTB-related toxoid LCTBA. Memory responses were analyzed by comparing the magnitudes and kinetics of intestine-derived antibody-secreting cell responses to a single dose of MEV in three groups of adult Swedish volunteers (n=16-19 subjects per group) in a Phase I trial: non-immunized controls (I) and subjects who in a previous Phase I trial 13-23 months earlier had received two biweekly doses of MEV (II) or MEV+double mutant LT (dmLT) adjuvant (III). Responses against CFs and LTB were analyzed in antibodies in lymphocyte secretions (ALS) of blood mononuclear cells collected before (day 0) and 4/5 and 7 days after immunization. Specific circulating memory B cells present at the time of the single dose vaccination were also studied to determine if such cells may reflect mucosal memory. Considerably higher and significantly more frequent IgA ALS responses against all CFs and LTB were induced by the single vaccine dose in the previously immunized than in non-immunized volunteers. Furthermore, peak IgA ALS responses against all antigens were observed on days 4/5 in most of the previously immunized subjects whereas only a few previously non-vaccinated individuals responded before day 7. Priming with adjuvant did not influence memory responses. Circulating vaccine specific IgA memory B cells were not detected, whereas anti-toxin IgG memory B cells were identified 13-23 months after priming vaccination. We conclude that MEV induces functional mucosal immunological memory which remains at least 1-2 years. Furthermore, our results support that analysis of antibody-secreting cell responses after booster vaccination may be a useful approach to evaluate longstanding mucosal immunological memory in humans. CLINICAL TRIALS REGISTRATION: ISRCTN27096290.

Parallel analysis of mucosally derived B- and T-cell responses to an oral typhoid vaccine using simplified methods.

There is a great need for simple methods for analysis of immune responses to mucosal vaccines that can be used on small blood volumes in field trials in both children and adults. We have investigated if mucosally derived B- and T-cell responses can be monitored in parallel by analysis of antibodies and T-cell effector molecules in culture supernatants from circulating blood lymphocytes obtained from orally vaccinated Swedes. Immunization with a live oral model vaccine, i.e. Salmonellaenterica serovar Typhi Ty21a, gave rise to secretion of typhoid specific IgA and IgM antibodies from peripheral blood mononuclear cells (PBMCs) and this response could be equally well detected by ELISA and ELISPOT 7 days after vaccination. The ELISA based assay could be further simplified by using buffy coat cells, but not by using whole blood or frozen PBMCs. Vaccine induced T-cell responses appeared later than the B-cell responses, but could be detected by ELISA assessment of IFN-gamma and granzymes in supernatants from antigen stimulated PBMCs 21 days after vaccination. Thus, both B- and T-cell responses could be detected using simple ELISA based assays that would be practical to use in large-scale vaccine trials.

Influence of exogenous reproductive hormones on specific antibody production in genital secretions after vaginal vaccination with recombinant cholera toxin B subunit in humans.

The objective of this study was to investigate the influence of exogenous reproductive hormones on the local and systemic production of specific immunoglobulin A (IgA) and IgG antibodies after vaginal vaccination with recombinant cholera toxin subunit B (CTB). Three groups of women using either progesterone-containing intrauterine devices (n=9), oral contraceptives (n=8), or no hormonal contraceptive methods (n=9) were vaginally immunized twice, 2 weeks apart. Cervical secretions, vaginal fluids, and serum were collected before and after vaccination. Total and CTB-specific IgA and IgG antibodies in genital secretions and serum were analyzed by enzyme-linked immunosorbent assay. A majority of the women presented strong CTB-specific IgA and IgG antibody responses in cervicovaginal secretions after vaccination, whereas the antitoxin responses in serum were weaker. Exogenously administered steroid hormones did not seem to have any impact on the production of specific antibodies. Both the frequencies and the magnitudes of IgA and IgG antitoxin responses in genital secretions were comparable among the three immunization groups. An association, in particular for IgA, was found between the magnitudes of the CTB-specific antibody responses in cervical secretions and vaginal fluids after vaccination. The sensitivities and positive predictive values of vaginal antibody analyses to reflect responses in cervical secretions were also high, suggesting that vaginal fluids alone might be used for evaluation of genital immune responses in large-scale vaccination studies in the future.

Kinetics of local and systemic immune responses after vaginal immunization with recombinant cholera toxin B subunit in humans.

Vaginal vaccination seems to be the best strategy for inducing specific immunoglobulin A (IgA) and IgG antibody responses in the female genital tract. The relative efficiencies of one, two, and three vaginal doses of recombinant cholera toxin B subunit (CTB) in generating mucosal and systemic immune responses in healthy women were evaluated, and the kinetics of the immune responses were monitored for responding volunteers for up to 12 months after the last vaccination. A single dose of CTB failed to generate CTB-specific IgA antibody responses in cervical secretions. Two vaccinations induced significant increases in IgA antitoxin titers in seven of nine volunteers, and four volunteers also developed IgG antitoxin responses. The magnitudes of the responses were 20-fold for IgA antitoxin and 7.1-fold for IgG antitoxin. A third vaccination did not significantly increase the antitoxin responses, although the frequency of IgG responses was slightly higher than that after the second vaccination. In serum, CTB-specific antibodies were observed already after a single vaccination. However, two vaccinations were required to induce marked IgA as well as IgG antitoxin titer increases in the majority of volunteers. The postvaccination levels of antitoxin antibodies in serum were comparable after two and three vaccinations. At 12 months after vaccination, significantly elevated IgA and IgG antitoxin levels in cervical secretions could still be detected in approximately half of the volunteers who had initially responded to the vaccine. Antitoxin titer increases in serum were found in most of the vaccinees at follow-up.

T- and B-cell immune responses of patients who had undergone colectomies to oral administration of Salmonella enterica serovar Typhi Ty21a vaccine.

The capacity of an oral live attenuated Salmonella enterica serovar Typhi Ty21a vaccine to induce immune responses in patients who had undergone colectomies because of ulcerative colitis was evaluated, and these responses were compared with those of healthy volunteers. Purified CD4(+) and CD8(+) T cells from peripheral blood were stimulated in vitro by using the heat-killed Ty21a vaccine strain, and the proliferation and gamma interferon (IFN-gamma) production were measured before and 7 or 8 days after vaccination. Salmonella-specific immunoglobulin A (IgA) and IgG antibody responses in serum along with IgA antibody responses in ileostomy fluids from the patients who had undergone colectomies were also evaluated. Three doses of vaccine given 2 days apart failed to induce proliferative T-cell responses in all the six patients who had undergone colectomies, and increases in IFN-gamma production were found only among the CD8(+) cells from three of the patients. In contrast, both proliferative responses and increased IFN-gamma production were observed among CD4(+) and CD8(+) T cells from 3 and 6 of 10 healthy volunteers, respectively. Salmonella-specific IgA and/or IgG antibody responses in serum were observed for five (56%) of nine patients who had undergone colectomies and in 15 (88%) of 17 healthy volunteers. In ileostomy fluids, significant anti-Salmonella IgA antibody titer increases were detected in six (67%) of nine patients who had undergone colectomies. The impaired T- and B-cell immune responses found after vaccination in the circulation of patients who have undergone colectomies may be explained by a diminished colonization of the Ty21a vaccine strain due to the lack of a terminal ileum and colon.

Introductory evaluation of an oral, killed whole cell enterotoxigenic Escherichia coli plus cholera toxin B subunit vaccine in Egyptian infants.

BACKGROUND: We conducted the first trial to assess the safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli plus cholera toxin B-subunit vaccine in children <2 years old. METHODS: Three doses of vaccine or killed E. coli K-12 control were given at 2-week intervals to 64 Egyptian infants, 6 to 18 months old, in a randomized, double blind manner. Adverse events were monitored for 3 days after each dose. Blood was collected before immunization and 7 to 10 days after each dose to assess vaccine-specific serologic responses. RESULTS: There was no statistically significant intergroup difference in the percentage of subjects reporting the primary safety endpoint (diarrhea or vomiting) after the first (31%, vaccine; 30%, control) or third (14%, vaccine; 18%, control) dose, whereas there was a trend toward greater reporting in the vaccine group after Dose 2 (36%, vaccine; 18%, control; P = 0.052). The percentage of children showing IgA seroconversion after any dose was higher in the vaccine than the control group for recombinant cholera toxin B-subunit (97% vs. 46%), colonization factor antigen I (61% vs. 18%) and coli surface antigen 4 (39% vs. 4%) (P < 0.001 for each comparison). IgG seroconversion rates in the vaccine and control groups were 97 and 21% to recombinant cholera toxin B-subunit (P < 0.001), 64 and 29% for colonization factor antigen I (P < 0.01), 53 and 21% for coli surface antigen 2 (P < 0.05) and 58 and 4% for coli surface antigen 4 (P < 0.001), respectively. The third vaccine dose was followed by augmented IgG antitoxin titers. CONCLUSION: The oral enterotoxigenic E. coli vaccine was safe and immunogenic in this setting in Egyptian infants.