Polysaccharide conjugate vaccine responses in bone marrow transplant patients

Invasive pneumococcal serotype 3 infection following pneumococcal vaccination in a hematopoietic stem cell transplant patient: A case report

Given the high mortality rate of invasive pneumococcal disease (IPD) in hematopoietic stem cell transplant (HSCT) recipients, vaccination is recommended. These recipients respond to most vaccines; however, their immune response is typically weaker during the first months or years after transplantation, compared with that of healthy individuals. Here, we report a case of IPD with serotype 3 pneumonia and empyema in an HSCT recipient who had received three doses of the 13-valent pneumococcal conjugate vaccine (PCV) and one dose of the 23-valent pneumococcal polysaccharide vaccine; furthermore, the recipient had no relapse, graft-versus-host disease, or use of immunosuppressive agents after allogeneic HSCT for acute myeloid leukemia. Moreover, we discussed the characteristics of serotype 3 Streptococcus pneumoniae, a case series of breakthrough infections with S. pneumoniae in HSCT recipients who received pneumococcal vaccines, and the potential implications for the upcoming PCV15 and PCV20 vaccines for serotype 3.

Clinical Effectiveness of Conjugate Pneumococcal Vaccination in Hematopoietic Stem Cell Transplantation Recipients

Hematopoietic stem cell transplantation (HSCT) recipients are vulnerable to invasive pneumococcal disease (IPD), with reported IPD rates ranging from 3.81 to 22.5/1000 HSCT. This IPD risk could relate to immunodeficiency, low vaccination uptake, and poor immunogenicity of pneumococcal polysaccharide vaccine (PPV). Literature comparing the clinical effectiveness of pneumococcal conjugate vaccination (PCV) and PPV after HSCT is limited. In this retrospective analysis of HSCT recipients at our center from 2004 to 2015, we evaluated vaccination uptake and compared IPD rates in patients receiving PPV (pre-2010 group) and PCV (post-2010 group). IPD was determined from microbiological results for all HSCT recipients from January 2004 to June 30, 2019. Eight hundred patients had a total of 842 HSCT events, including autologous HSCT (auto-HSCT; n = 562) and allogeneic HSCT (allo-HSCT; n = 280). More than 90% of the HSCT recipients were enrolled, and >93% of surviving HSCT recipients completed the vaccination protocol. Fifteen IPD episodes occurred in 13 patients between 2004 and June 30, 2019. Thirteen episodes occurred in the pre-2010 group, even though 9 of 13 (69%) serotyped isolates were covered by PPV. Two episodes occurred in the post-2010 group; neither serotype was covered by PCV. Thus, with PCV introduction, IPD rate was significantly reduced from 38.5/1000 unique HSCTs pre-2010 to 4.0/1000 unique HSCTs post-2010 (P < .001). A significant reduction was seen in both auto-HSCTs (from 29.4 to 3.1 /1000 unique auto-HSCTs; P = .011) and allo-HSCTs (from 58.3 to 5.6/1000 unique allo-HSCTs; P = .011). PCV demonstrated superior clinical effectiveness over PPV, highlighting its importance in preventing infectious complications after HSCT. Robust vaccination programs at transplantation centers are needed to optimize vaccination uptake and completion.

Trends in Invasive Pneumococcal Disease in Cancer Patients After the Introduction of 7-valent Pneumococcal Conjugate Vaccine: A 20-year Longitudinal Study at a Major Urban Cancer Center

Background

Rates of invasive pneumococcal disease (IPD) declined since routine childhood immunization with the 7-valent pneumococcal conjugate vaccine (PCV7) in 2000. We studied the impact of PCV7 on the incidence of IPD in cancer patients.

Methods

This was a retrospective analysis of adult and pediatric patients treated at Memorial Sloan Kettering Cancer Center from 1992 to 2012. Recovery of Streptococcus pneumoniae from a sterile site defined IPD. IPD incidence was calculated as cases per 1,000 unique patient-visits per year (UPV). IPD incidence was calculated for the periods: "before PCV7" (1992-2000), "after PCV7" (2001-2010) and "after PCV13" (2011-2012).

Results

Of 343 IPD cases, 165, 155, and 23 cases occurred "before PCV7," "after PCV7" and "after PCV13" respectively. The IPD incidence declined from 0.43 "before PCV7" to 0.17 "after PCV7" (95% confidence interval [CI]: 0.33-0.46, P < .001) and 0.11 "after PCV13" (95% CI: 0.42-0.96, P = .004). Adults with hematologic malignancies and children had the highest incidence. In patients 1-4 years old, the incidence declined from 11.2 "before PCV7" to 2.38 "after PCV7" (79% decrease, 95% CI: 0.1-0.4, P < .001). In patients with hematologic malignancies, the incidence declined from 2.55 "before PCV7" to 0.92 "after PCV7" (64% decrease, 95% CI: 0.27-0.47, P < .001).

Conclusions

The incidence of IPD among cancer patients sharply declined after introduction of PCV7; especially in high risk groups. The decline in adults suggests an indirect effect from PCV7 childhood vaccination.

B Cell Reconstitution and Influencing Factors After Hematopoietic Stem Cell Transplantation in Children

B cell reconstitution after hematopoietic stem cell transplantation (HSCT) is variable and influenced by different patient, donor, and treatment related factors. In this review we describe B cell reconstitution after pediatric allogeneic HST, including the kinetics of reconstitution of the different B cell subsets and the development of the B cell repertoire, and discuss the influencing factors. Observational studies show important roles for stem cell source, conditioning regimen, and graft vs. host disease in B cell reconstitution. In addition, B cell recovery can play an important role in post-transplant infections and vaccine responses to encapsulated bacteria, such as pneumococcus. A substantial number of patients experience impaired B cell function and/or dependency on Ig substitution after allogeneic HSCT. The underlying mechanisms are largely unresolved. The integrated aspects of B cell recovery after HSCT, especially BCR repertoire reconstitution, are awaiting further investigation using modern techniques in order to gain more insight into B cell reconstitution and to develop strategies to improve humoral immunity after allogeneic HSCT.

Vaccination of haemopoietic stem cell transplant recipients: guidelines of the 2017 European Conference on Infections in Leukaemia (ECIL 7)

Infection is a main concern after haemopoietic stem cell transplantation (HSCT) and a major cause of transplant-related mortality. Some of these infections are preventable by vaccination. Most HSCT recipients lose their immunity to various pathogens as soon as the first months after transplant, irrespective of the pre-transplant donor or recipient vaccinations. Vaccination with inactivated vaccines is safe after transplantation and is an effective way to reinstate protection from various pathogens (eg, influenza virus and Streptococcus pneumoniae), especially for pathogens whose risk of infection is increased by the transplant procedure. The response to vaccines in patients with transplants is usually lower than that in healthy individuals of the same age during the first months or years after transplant, but it improves over time to become close to normal 2-3 years after the procedure. However, because immunogenic vaccines have been found to induce a response in a substantial proportion of the patients as early as 3 months after transplant, we recommend to start crucial vaccinations with inactivated vaccines from 3 months after transplant, irrespectively of whether the patient has or has not developed graft-versus-host disease (GvHD) or received immunosuppressants. Patients with GvHD have higher risk of infection and are likely to benefit from vaccination. Another challenge is to provide HSCT recipients the same level of vaccine protection as healthy individuals of the same age in a given country. The use of live attenuated vaccines should be limited to specific situations because of the risk of vaccine-induced disease.

Vaccines in pediatric transplant recipients-Past, present, and future

Infections significantly impact outcomes for solid organ and hematopoietic stem cell transplantation in children. Vaccine-preventable diseases contribute to morbidity and mortality in both early and late posttransplant time periods. Several infectious diseases and transplantation societies have published recommendations and guidelines that address immunization in adult and pediatric transplant recipients. In many cases, pediatric-specific studies are limited in size or quality, leading to recommendations being based on adult data or mixed adult-pediatric studies. We therefore review the current state of evidence for selected immunizations in pediatric transplant recipients and highlight areas for future investigation. Specific attention is given to studies that enrolled only children.

Vaccinating donors for hematopoietic cell transplantation: A systematic review and future perspectives

Allogeneic hematopoietic cell transplantation (Allo-HCT) recipients are at an increased risk of infectious complications, which is a major cause of morbidity and mortality post-transplant. Vaccination of donors is one of the strategies that has been studied to improve immune reconstitution post-transplant, however the efficacy and safety of this strategy is not well reviewed in the literature. In this systematic review we sought to evaluate the current strategies of donor vaccination along with their immunogenicity, effectiveness and safety. Utilizing strict selection criteria with defined MeSH terminology, an electronic search was conducted from the following databases: Medline, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews and Scopus. Abstracts of various professional society meetings were also screened and hand searching of various reviews and guideline articles was carried out. The full text of 52 articles were reviewed, from which 5 articles satisfied the inclusion/exclusion criteria for effectiveness and immunogenicity trials and 1 article was included for safety data. Jadad score was used to assess the quality of included studies. The results of the included studies were inconsistent, and the studies were generally of suboptimal methodological quality. Most of the included studies (n = 3) investigated the use of more than one vaccine, however not all commonly used vaccines in HCT were investigated. None of the studies reported any long-term benefits for HCT recipients of vaccinated donors. Only one study reported safety data of using vaccination in donors. Given the suboptimal quality of the studies, and questionable effectiveness, donor vaccination cannot be recommended for all. Prospective high-quality vaccine trials in HCT donors are needed.

Pneumococcal polysaccharide vaccination in allogeneic hematopoietic stem cell transplantation recipients: a prospective single-center study

Few studies have evaluated the response of allogeneic hematopoietic stem cell transplantation [allo-HSCT] recipients to pneumococcal polysaccharide vaccine-23 [PPSV23] in the modern transplant era when more elderly patients undergo allo-HSCT. We administered a single dose of PPSV23 to 30 allo-HSCT recipients and evaluated serotype-specific antibody responses using IgG measured by enzyme-linked immunosorbent assay and opsonophagocytic assay [OPA] titers in a multiplexed opsonophagocytic killing assay. The median patient age was 54 years [range, 23-68], and the interval from allo-HSCT to vaccination was 756 days [range, 389-1903]. No severe adverse effects were observed. The median positive response rates at 1 month and 1 year post-vaccination for the 7 serotypes measured by IgG were the same at 43% [range, 33-57], while those for 8 serotypes measured by OPA were 72% [range, 55-86] and 55% [range, 52-62], respectively. Peripheral blood stem cell transplantation improved vaccine response based on OPA titers at 1 month post-vaccination. During the median follow-up period of 1135 days post-vaccination, one patient developed pneumococcal bacteremia at 998 days. Our study suggests that PPSV23 vaccination in allo-HSCT recipients is safe and may result in a serological response.

Infectious diseases in allogeneic haematopoietic stem cell transplantation: prevention and prophylaxis strategy guidelines 2016

Infectious complications after allogeneic haematopoietic stem cell transplantation (allo-HCT) remain a clinical challenge. This is a guideline provided by the AGIHO (Infectious Diseases Working Group) of the DGHO (German Society for Hematology and Medical Oncology). A core group of experts prepared a preliminary guideline, which was discussed, reviewed, and approved by the entire working group. The guideline provides clinical recommendations for the preventive management including prophylactic treatment of viral, bacterial, parasitic, and fungal diseases. The guideline focuses on antimicrobial agents but includes recommendations on the use of vaccinations. This is the updated version of the AGHIO guideline in the field of allogeneic haematopoietic stem cell transplantation utilizing methods according to evidence-based medicine criteria.

Vaccinations in patients with hematological malignancies

Patients with hematological malignancies are at risk for a number of infections that are potentially preventable by vaccinations such as pneumococcal infections and influenza. Treatment, especially with anti-B-cell antibodies and hematopoietic stem cell transplantation (HSCT), negatively impacts the response to vaccination for several months. It is therefore recommended that patients be vaccinated before initiating immunosuppressive therapy if possible. The risk of side-effects with inactivated vaccines is low, but care has to be taken with live vaccines, such as varicella-zoster virus vaccine, since severe and fatal complications have been reported. HSCT patients require repeated doses of most vaccines to achieve long-lasting immune responses. New therapeutic options for patients with hematological malignancies that are rapidly being introduced into clinical practice will require additional research regarding the efficacy of vaccinations. New vaccines are also in development that will require well-designed studies to ascertain efficacy and safety.

Pretransplant vaccinations in allogeneic stem cell transplantation donors and recipients: an often-missed opportunity for immunoprotection?

Immune deficiency following hematopoietic cell transplantation predisposes the patient to potentially deadly infections. Vaccinations can improve immunity and thus reduce the morbidity and mortality associated with these infections. Over the years different sets of guidelines have been published the most recent by the Infectious Diseases Society of American (IDSA). There is limited evidence that vaccination of donors and/or recipients before transplantation may improve immunity. However, despite the possibility of augmented immunity, there remain logistical, ethical and medical concerns about such a vaccination strategy.

Analysis of factors affecting immune recovery and initial response to tetanus after DTaP vaccination in pediatric allogeneic HSCT patients

Transfer of donor immunity after allo-HSCT is limited, requiring re-vaccination after HSCT. The CDC 2009 guidelines introduced earlier vaccination post-HSCT with a uniform vaccination strategy. This study objective was to describe predictors of immune recovery and initial response to tetanus after DTaP vaccination post-HSCT. We conducted a retrospective chart review of pediatric allo-HSCT patients transplanted between July 1, 2007-June 30, 2012 who survived >1 yr without relapse (N = 27). Response to tetanus one month after the initial dose of DTaP was defined as a ≥4 fold increase in tetanus titers ≥1 month after vaccination. Wilcoxon rank-sum exact test and Kruskall-Wallis tests were used to analyze CD4, CD8, and CD19 counts. Exact conditional logistic regression was utilized to analyze initial tetanus vaccination response. A statistically significant increase in median CD4, CD8, and CD19 counts occurred from six to 12 months post-HSCT (p ≤ 0.0001, 0.005, 0.004). Only 36% of patients had initial tetanus vaccination response at first attempt post-HSCT. None of the variables tested were statistically significant in predicting initial tetanus response to vaccination. There was no association between predictors of immune recovery or transplant variables and initial tetanus response. A uniform vaccination strategy is unlikely to provide protective antibodies for many post-HSCT patients and should be evaluated in larger studies.

Pneumococcal immunization in immunocompromised hosts: where do we stand?

Immunocompromised patients are all at risk of invasive pneumococcal disease, of different degrees and timings. However, considerable progress in pneumococcal immunization over the last 30 years should benefit these patients. The 23-valent polysaccharide vaccine has been widely evaluated in these populations, but due to its low immunogenicity, its efficacy is sub-optimal, or even low. The principle of the conjugate vaccine is that, through the protein conjugation with the polysaccharide, the vaccine becomes more immunogenic, T-cell dependent, and thus providing a better early response and a boost effect. The 7-valent conjugate vaccine has been the first one to be evaluated in different immunocompromised populations. We review here the efficacy and safety of the different antipneumococcal vaccines in cancer, transplant and HIV-positive patients and propose a critical appraisal of the current guidelines.

2013 IDSA clinical practice guideline for vaccination of the immunocompromised host

An international panel of experts prepared an evidenced-based guideline for vaccination of immunocompromised adults and children. These guidelines are intended for use by primary care and subspecialty providers who care for immunocompromised patients. Evidence was often limited. Areas that warrant future investigation are highlighted.

Vaccination of immunocompromised patients

Vaccination of immunocompromised patients is challenging both regarding efficacy and safety. True efficacy data are lacking so existing recommendations are based on immune responses and safety data. Inactivated vaccines can generally be used without risk but the patients who are most at risk for infectious morbidity and mortality as a result of their severely immunosuppressed state are also those least likely to respond to vaccination. However, vaccination against pneumococci, Haemophilus influenzae and influenza are generally recommended. Live vaccines must be used with care because the risk for vaccine-associated disease exists.

Immune reconstitution after hematopoietic cell transplantation

PURPOSE OF REVIEW

Successful immune reconstitution is important for decreasing posthematopoietic cell transplant (post-HCT) infections, relapse, and secondary malignancy, without increasing graft-versus-host disease (GVHD). Here we review how different parts of the immune system recover, and the relationship between recovery and clinical outcomes.

RECENT FINDINGS

Innate immunity (e.g., neutrophils, natural killer cells) recovers within weeks, whereas adaptive immunity (B and T cells) recovers within months to years. This has been known for years; however, more recently, the pattern of recovery of additional immune cell subsets has been described. The role of these subsets in transplant complications like infections, GVHD and relapse is becoming increasingly recognized, as gleaned from studies of the association between subset counts or function and complications/outcomes, and from studies depleting or adoptively transferring various subsets.

SUMMARY

Lessons learned from observational studies on immune reconstitution are leading to new strategies to prevent or treat posttransplant infections. Additional knowledge is needed to develop effective strategies to prevent or treat relapse, second malignancies and GVHD.

Immunity after (re)vaccination of paediatric patients following haematopoietic stem cell transplantation

AIMS

Loss of specific immunity follows allogeneic haematopoietic stem cell transplantation (HSCT) in the majority of cases. Responses to (re)vaccinations can be used as indicators of a functional immunological recovery.

METHODS

Twenty-three paediatric recipients of HSCT were enrolled in a single centre setting and responses to scheduled immunizations analysed.

RESULTS

Immunity to vaccine-preventable diseases was impaired post HSCT, but (re)vaccinations induced protective responses in 59-100%, depending on the vaccine, regardless of prior graft-versus-host disease (GVHD) history.

CONCLUSION

Despite the marked impact of moderate to severe chronic prior GVHD on both the qualitative and quantitative T-cell recovery post allogenic HSCT, most paediatric recipients of allogeneic stem cell grafts appear to attain protective antibody levels after immunization.

NCI, NHLBI/PBMTC first international conference on late effects after pediatric hematopoietic cell transplantation: persistent immune deficiency in pediatric transplant survivors

Defective immune reconstitution is a major barrier to successful hematopoietic cell transplantation (HCT), and has important implications in the pediatric population. There are many factors that affect immune recovery, including stem cell source and graft-versus-host disease (GVHD). Complete assessment of immune recovery, including T and B lymphocyte evaluation, innate immunity, and response to neoantigens, may provide insight as to infection risk and optimal time for immunizations. The increasing use of cord blood grafts requires additional study regarding early reconstitution and impact upon survival. Immunization schedules may require modification based upon stem cell source and immune reconstitution, and this is of particular importance as many children have been incompletely immunized, or not at all, before school entry. Additional studies are needed in children post-HCT to evaluate the impact of differing stem cell sources upon immune reconstitution, infectious risks, and immunization responses.

Immunization in special populations

In summary, immunizations in special populations require understanding the underlying disease and how it might affect the immune system's ability to mount an antibody response to vaccines or predispose certain patient populations to developing certain serious infections. There is still a great need for research on the optimal timing of vaccines after transplants, how to assess protection and development of a protective antibody response after immunization, and whether certain groups (eg, HIV) need to be revaccinated after a certain amount of time if their antibody levels decline. In addition, there are limited data on efficacy of the newer vaccines in these special patient populations, which also requires further investigation.

Immunization of hematopoietic stem cell transplant recipients against vaccine-preventable diseases

Worldwide, over 40,000 hematopoietic cell transplants (HCT) are carried out each year, with the majority of patients surviving long term. Owing to their new immune systems, these patients are susceptible to a variety of preventable infectious diseases. The 2009 influenza pandemic, the increase in pertussis and antibiotic-resistant pneumococcus, as well as recent outbreaks of measles and mumps in immunocompetent individuals further highlight the need for effective revaccination of HCT recipients. Post-transplant vaccine guidelines, including those published in 2009, recommend immunization of all patient groups at fixed times post-HCT. Although early vaccination to protect against vaccine-preventable diseases is desirable, there are still limited data on whether this approach is efficacious in patient groups whose immune recovery differs from recipients of an unmodified HLA-matched sibling transplant. In the absence of such data, prospective trials are needed to better define the optimal timing for immunizing recipients of alternative donors. Ideally, such trials should be designed to identify biological markers that will predict an optimal and durable vaccine response.

Transfer of influenza vaccine-primed costimulated autologous T cells after stem cell transplantation for multiple myeloma leads to reconstitution of influenza immunity: results of a randomized clinical trial

Severe immune deficiency follows autologous stem cell transplantation for multiple myeloma and is associated with significant infectious morbidity. This study was designed to evaluate the utility of a pretransplantation vaccine and infusion of a primed autologous T-cell product in stimulating specific immunity to influenza. Twenty-one patients with multiple myeloma were enrolled from 2007 to 2009. Patients were randomly assigned to receive an influenza-primed autologous T-cell product or a nonspecifically primed autologous T-cell product. The study endpoint was the development of hemagglutination inhibition titers to the strain-specific serotypes in the influenza vaccine. Enzyme-linked immunospot assays were performed to confirm the development of influenza-specific B-cell and T-cell immunity. Patients who received the influenza-primed autologous T-cell product were significantly more likely to seroconvert in response to the influenza vaccine (P = .001). Seroconversion was accompanied by a significant B-cell response. No differences were observed in the global quantitative recovery of T-cell and B-cell subsets or in global T-cell and B-cell function. The provision of a primed autologous T-cell product significantly improved subsequent influenza vaccine responses. This trial was registered at www.clinicaltrials.gov as #NCT00499577.

Post-hematopoietic stem cell transplant immunization practices in the Pediatric Blood and Marrow Transplant Consortium

BACKGROUND

A survey of National Marrow Donor Program transplant centers in 1995 demonstrated a wide range of immunization practices in post-hematopoietic stem cell transplant (HSCT) recipients, which led to the 2000 Centers for Disease Control and Prevention (CDC) recommendations for vaccination after HSCT. We surveyed the principal investigators of the Pediatric Blood and Marrow Transplant Consortium (PBMTC) to identify immunization practice patterns after HSCT and assess compliance with the 2000 CDC guidelines.

PROCEDURE

Approval was obtained from the Medical University of South Carolina Institutional Review Board. A 33 question survey using surveymonkey.com was distributed by email to principal investigators in the PBMTC.

RESULTS

Forty-one (40%) of the 102 pediatric HSCT centers participating in the PBMTC responded. Thirty of the responding centers completed the entire survey. For individual vaccines, compliance with the CDC guidelines ranged from 22% to 93%. Less than 20% of the centers reported schedules consistent with the 2000 CDC recommendations for both allogeneic and autologous HSCT recipients.

CONCLUSION

Despite the 2000 CDC guidelines, wide variation in post-HSCT immunization practices still exists. Updated guidelines have been needed, particularly to address the use of the pneumococcal conjugate vaccine. In conjunction with multiple other groups, the CDC recently released new immunization guidelines in October 2009. Additional data are still needed to adequately address the utility of incorporating immunologic parameters with the timing of vaccination after HSCT.

Reconstitution of the immune system after hematopoietic stem cell transplantation in humans

Hematopoietic stem cell transplantation is associated with a severe immune deficiency. As a result, the patient is at high risk of infections. Innate immunity, including epithelial barriers, monocytes, granulocytes, and NK cells recovers within weeks after transplantation. By contrast, adaptive immunity recovers much slower. B- and T-cell counts normalize during the first months after transplantation, but in particular, T-cell immunity may remain impaired for years. During the last decade, much of the underlying mechanisms have been identified. These insights may provide new therapies to accelerate recovery.

Response to pneumococcal (PNCRM7) and haemophilus influenzae conjugate vaccines (HIB) in pediatric and adult recipients of an allogeneic hematopoietic cell transplantation (alloHCT)

Young children and allogeneic hematopoietic cell transplantation (HCT) recipients respond poorly to polysaccharide antigens, rendering them susceptible to severe infections because of encapsulated bacteria. This study evaluated the responses of 127 HCT patients, median age 23.0 years, vaccinated with PNCRM7 and Haemophilus influenzae (HIB) conjugate, 2 conjugate vaccines highly immunogenic in healthy children. Median time to vaccination was 1.1 years after HCT. Sixty-two percent of patients responded to PNCRM7 (45 of 51 children, 34 of 76 adults, P < .001). Overall response to HIB was 86%, including 77% of PNCRM7 nonresponders. Although PNCRM7 response was adversely affected by older age (P < .001), individuals > or =50 years old responded significantly better if vaccinated following acquisition of specific minimal milestones of immune competence, CD4 >200/microL, IgG >500 mg/dL, PHA within 60% lower limit of normal (11 of 19 versus 0 of 8, P < .006). A similar trend was observed in patients with limited chronic graft-versus-host disease (cGVHD). In all patients, higher levels of circulating CD4(+)CD45RA cells correlated with improved PNCRM7 response. These data demonstrate that PNCRM7 is immunogenic in allogeneic HCT patients, including older adults, but suggest that vaccination at fixed intervals after HCT, irrespective of immune competence, may limit its effectiveness. Prospective, multicenter trials assessing the best strategy to administer this vaccine and its impact on pneumococcal infections following transplantation are warranted.

Haemophilus influenzae type b vaccine failure in children is associated with inadequate production of high-quality antibody

BACKGROUND

Despite the excellent immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccines, breakthrough cases of Hib disease still affect a small proportion of vaccinated children in the United Kingdom. We performed a retrospective study to compare the avidity of antibody directed against the Hib polysaccharide capsule (PRP) in children who experienced Hib vaccine failure in the United Kingdom among 3 historical cohorts and with age-matched healthy control subjects.

METHODS

Serum samples from vaccinated children with invasive Hib disease were collected beginning in 1992 as part of enhanced surveillance for Hib disease following vaccine introduction. A total of 251 children who experienced Hib vaccine failure were identified from 3 historical cohorts (1992-1995, 1996-1999, and 2000-2003). The anti-PRP antibody concentration and avidity from healthy age-matched control subjects was obtained for the 3 contemporary time points (1995, 1999, and 2002). Serum anti-PRP antibody concentration was measured in each of the samples using a standard Hib ELISA, and antibody avidity was determined using thiocyanate elution.

RESULTS

Within the first 60 days after disease onset, there was no change in the anti-PRP antibody avidity, and there was no statistically significant difference in the geometric mean Hib antibody avidity over the 3 study periods. However, the children who experienced Hib vaccine failure had significantly lower Hib antibody avidity than did healthy control subjects, despite a marked antibody response following infection.

CONCLUSIONS

Children who experience Hib disease despite vaccination appear to have a defect in immunological priming, leading to a qualitative difference in Hib-specific memory B cells. Low anti-PRP antibody avidity decreases the functional activity of anti-PRP antibody in the sera of these children experiencing vaccine failure, leading to disease susceptibility.

Vaccinations in children treated with standard-dose cancer therapy or hematopoietic stem cell transplantation

Most children with cancer are immunocompromised during therapy and for a variable period after completion of therapy. They are at an increased risk of infections, including vaccine-preventable infections. There is a reduction in immunity to vaccine-preventable diseases after completion of standard-dose chemotherapy and after hematopoietic stem cell transplant. It is important to protect these children against vaccine-preventable diseases by reimmunization.

Immunologic approaches to ovarian cancer treatment

The clinical course of ovarian cancer is often marked by periods of relapse and remission until chemotherapy resistance develops. Patients in remission with minimal disease burdens are ideally suited for the evaluation of immune-based strategies. The role of immune surveillance in improving outcome has been supported by the correlation of increased survival with the presence or absence of tumor-infiltrating lymphocytes in a given patient. Major obstacles to the development of successful immune strategies include the identification of tumor-restricted immunogenic targets, generation of a sufficient immune response to cause tumor rejection, and approaches to overcome evasion of immune attack. As optimal strategies are being developed, many questions remain. Some of the questions are as follows: What is the best antigen form (eg, peptides, proteins, or tumor lysates)? What are the appropriate adjuvants? Are monovalent or multivalent vaccines likely to be more effective? What is the optimal frequency and duration of vaccination? How should antigen-specific responses be monitored? How should the anticancer response be maintained? In this review, we will explore representative examples of immune strategies under investigation for patients with ovarian carcinoma that illustrate many of these issues. We will review ongoing phase III studies for patients in first clinical remission. Basic principles generic to all these immunotherapeutic approaches will be discussed in the hopes of yielding the most promising results as the field continues to evolve.

Anti-pneumococcal antibody titre measurement: what useful information does it yield?

Measuring and interpretation of the immune response to pneumococcal polysaccharides is a complex field, owing to the diversity of the pneumococcal polysaccharide capsular types, different vaccine formulations including both polysaccharide and conjugate vaccines, diverse pneumococcal serological assays, lack of immunogenicity data for the conjugate in a number of at-risk groups and complex vaccine schedules. Even the reasons for performing pneumococcal serology can be complex, as assays may be performed for one of two reasons: either to assess an individual's immune status to the pneumococcus or to discriminate between normal and abnormal humoral immunity. This review details a history of the pneumococcal serological assays and provides some insight into when serology can prove useful, including vaccination data for certain at-risk groups.

Streptococcus pneumoniae infections in 47 hematopoietic stem cell transplantation recipients: clinical characteristics of infections and vaccine-breakthrough infections, 1989-2005

Streptococcus pneumoniae infections can cause serious systemic disease in patients following hematopoietic stem cell transplantation (HSCT), and the response to pneumococcal vaccine is inadequate in most HSCT recipients. We evaluated the clinical spectrum of pneumococcal disease and vaccine-breakthrough infections in HSCT recipients at our cancer center in a retrospective analysis of all consecutive episodes of S. pneumoniae infection from 1989 through 2005. During the study period, 7888 patients underwent HSCT at our center; we identified 47 HSCT recipients with 54 S. pneumoniae infections. The overall incidence of S. pneumoniae infection was 7 per 1000 HSCTs. The incidence was higher in recipients of allogeneic grafts than in recipients of autologous grafts (9 vs. 5 per 1000 HSCTs, respectively; p <or= 0.012). Thirty-two of the 47 patients (68%) had leukemia or lymphoma; 24 patients (51%) had a malignancy that was in complete remission. Seventeen patients (36%) had graft-versus-host disease, which was chronic in 16. The 54 episodes of S. pneumoniae infection occurred 433 +/- 669 days after HSCT; 5 patients (11%) had multiple episodes. Four episodes of S. pneumoniae infection occurred within 100 days following transplantation (45 +/- 49 d); 2 of these were during the pre-engraftment period and 3 were nosocomial infections. All 50 late post-transplant episodes (93%), which occurred 473 +/- 671 days following transplantation, were community-acquired infections (p < 0.00016). Thirty-three episodes (61%) presented as bacteremic pneumonia, 10 (19%) as pneumonia, and 8 (15%) as uncomplicated S. pneumoniae bacteremia alone. Logistic regression analysis showed that patients receiving systemic corticosteroids had increased risk for bacteremic pneumonia (odds ratio [OR], 11.7; 95% confidence intervals [CI], 1.371-99.280; p <or= 0.025). Patients with lymphoma (OR, 6.101; 95% CI, 1.106-33.640; p <or= 0.04) were more likely to develop pneumonia alone. In 27 episodes (93%) among 29 in which S. pneumoniae susceptibility testing was performed, the patients received concordant antimicrobials. Among the 6 patients (13%) who died of S. pneumoniae infection, 4 had S. pneumoniae bacteremic pneumonia and only 1 had chronic GVHD. Admission to a critical care unit at the onset of infection (OR, 15.5; 95% CI, 2.116-113.541; p <or= 0.007) and each unit increase in APACHE II score increase the probability of death (OR, 1.9; 95% CI, 1.181-3.054; p <or= 0.008). All 5 (11%) patients who developed vaccine-breakthrough S. pneumoniae infection (546 +/- 732 d following vaccination) had pneumonia, and in 4 patients concurrent bacteremia also occurred. A serious S. pneumoniae infection in HSCT recipients occurred more commonly in patients with lymphoma and patients receiving high-dose systemic corticosteroid therapy. It is noteworthy that there were no cases of extrapulmonary organ infection in HSCT recipients who presented with S. pneumoniae infection at our institution.

Revaccination with measles, tetanus, poliovirus, Haemophilus influenzae type B, meningococcus C, and pneumococcus vaccines in children after hematopoietic stem cell transplantation

BACKGROUND

There is a decrease in antibody levels after hematopoietic stem cell transplant (HSCT), and such patients may be at increased risk of acquiring vaccine-preventable infection. A simple and validated revaccination schedule is required. The aim of this study was to evaluate the immunogenicity of a revaccination schedule for pediatric HSCT recipients.

METHODS

Thirty-eight children (age, 1-18 years) who had undergone autologous or allogeneic HSCT for malignant diseases were recruited. All children received vaccinations in accordance with a predefined schedule. Antibody concentrations were measured before and 2-4 weeks after vaccination against tetanus; Haemophilus influenzae type b (Hib); meningococcus C; measles; poliovirus serotypes 1, 2, and 3; and 9 pneumococcus serotypes.

RESULTS

Before vaccination, protective antibody levels were found for tetanus in 95% of patients (geometric mean concentration [GMC], 0.07 IU/mL; 95% CI, 0.05-0.1 IU/mL), for Hib in 63% (GMC, 0.34 microg/mL; 95% CI, 0.21-0.57 microg/mL), for measles in 60% (GMC, 102 mIU/mL; 95% CI, 41-253 mIU/mL), for meningococcus C in 11% (geometric mean titer [GMT], 1:4; 95% CI, 1:2-1:8.4), for all 3 poliovirus serotypes in 29%, and for all 9 pneumococcal serotypes in 0%. Vaccination resulted in a significant increase (P < or = .05) in antibody levels to each vaccine antigen studied, with 100% of patients achieving protection against tetanus (GMC, 2.2 IU/mL; 95% CI, 1.8-2.7 IU/mL), 100% achieving protection against Hib (GMC, 8.4 microg/mL; 95% CI, 7.6-9.3 microg/mL), 100% achieving protection against measles (GMC, 2435 mIU/mL; 95% CI, 1724-3439 mIU/mL), 100% achieving protection against meningococcus C (GMT, 1:5706; 95% CI, 1:3510-1:9272), 92% achieving protection against the 3 poliovirus serotypes, and > or = 80% achieving protection against each of the heptavalent pneumococcal conjugate vaccine-associated serotypes. No factors relevant to age, underlying disease, or treatment type were found to significantly influence responses.

CONCLUSION

Revaccination of pediatric HSCT recipients in accordance with this revaccination schedule provides a high level of protection against these vaccine-preventable diseases.

A randomized study on donor immunization with tetanus–diphtheria, Haemophilus influenzae type b and inactivated poliovirus vaccines to improve the recipient responses to the same vaccines after allogeneic bone marrow transplantation

The HLA-identical sibling donors of 111 bone marrow transplantation (BMT) recipients were randomised to receive or not to receive tetanus-diphtheria (T-d), Haemophilus influenzae type b (Hib), and inactivated poliovirus (IPV) vaccines 2-10 weeks before BM harvest. Fifty-three (DV+ group) recipients received the graft from a vaccinated donor and 58 (DV- group) from an unvaccinated donor. All recipients were vaccinated with the T-d, Hib and IPV vaccines at 3, 6 and 12 months after BMT. Diphtheria and Hib antibody concentrations were consistently higher in the DV+ than in the DV- group from 6 months post transplantation onwards. The differences were significant at 6 and 13 months for diphtheria and at 12 months for Hib antibody concentrations. Tetanus, PV1, PV2 and PV3 antibody levels were similar in both groups. Patients transplanted from donors with high tetanus, diphtheria and Hib antibody concentrations had higher respective antibody concentrations after BMT than those transplanted from donors with low antibody concentrations. Especially patients whose donors have low-specific antibody concentrations may benefit from donor vaccination with protein and conjugate vaccines.

Reimmunization after hematopoietic stem cell transplantation

Hematopoietic stem cell transplant recipients lose immune memory of exposure to infectious agents and vaccines accumulated through a lifetime, and therefore need to be revaccinated. Reimmunization protocols vary greatly among hematopoietic stem cell transplant centers. Diphtheria and tetanus toxoids, pertussis vaccine, Haemophilus influenza type B conjugate, 23-valent pneumococcal polysaccharide, inactivated influenza and polio vaccine and live attenuated measles-mumps-rubella vaccine are the currently recommended vaccines to be included in a vaccination program after hematopoietic stem cell transplant. Other variables, such as stem cell source, new adjuvants, T-cell depleted transplants, nonmyeloablative conditioning and donor immunization have recently been introduced and a constant update of current recommendations are needed. Studies recently published, the use of other vaccines and the perspectives for different vaccination protocols are discussed in this review.

Influence of genetic and environmental factors on the immunogenicity of Hib vaccine in Gambian twins

The differences in incidence rates of Haemophilus influenzae type b disease and the variation in Hib conjugate vaccine efficacy achieved among different ethnic groups suggest genetic influences on the immune response to Hib vaccine. The serum anti-PRP antibody concentration of 43 monozygotic (MZ) and 147 dizygotic (DZ) twin pairs in the Gambia was measured using a standardised Hib ELISA. Intrapair correlations for MZ and DZ twin pairs were compared and heritability in antibody responses to Hib conjugate vaccine was estimated to be 51% (95% CI: 32-66%), indicating a significant genetic contribution in the response. We conclude that genetic factors may be involved in the variation in immune response to Hib vaccine observed in different populations and may contribute to cases of vaccine failure.

Immunity for tumors and microbes after autotransplantation: if you build it, they will (not) come

Relapses after autologous stem cell transplants for hematopoietic malignancies are frequent and post-transplant infections continue to cause significant post-transplant morbidity and even mortality. The post-transplant period is typically characterized by low lymphocyte counts and impaired immune cell function. Early restoration of immune function may contribute to better disease control and enhance protection from infections. Indeed the attainment of a 'minimal residual disease' status following high-dose therapy makes the early post-transplant period ideal for the introduction of antitumor immunotherapy. Attempts to generate immunity against tumor and microbial antigens after autotransplantation have included vaccinations, T cell infusions (both resting and activated) and combinations of vaccinations and adoptive T cell infusions. One successful strategy for generating robust immune responses against microbial antigens was the combination of pre and post-transplant immunizations along with an early (post-transplant) infusion of in vivo vaccine-primed and ex vivo co-stimulated autologous T cells. Whether this or similar strategies will lead to the generation of effective antitumor immunity is unknown. The lessons gained from efforts to rebuild immune system function in the setting of autotransplantation may also be applicable to the problem of restoring immunity in other immunodeficient groups such as patients with cancer or HIV disease and the elderly.

Restoration of immunity in lymphopenic individuals with cancer by vaccination and adoptive T-cell transfer

Immunodeficiency is a barrier to successful vaccination in individuals with cancer and chronic infection. We performed a randomized phase 1/2 study in lymphopenic individuals after high-dose chemotherapy and autologous hematopoietic stem cell transplantation for myeloma. Combination immunotherapy consisting of a single early post-transplant infusion of in vivo vaccine-primed and ex vivo costimulated autologous T cells followed by post-transplant booster immunizations improved the severe immunodeficiency associated with high-dose chemotherapy and led to the induction of clinically relevant immunity in adults within a month after transplantation. Immune assays showed accelerated restoration of CD4 T-cell numbers and function. Early T-cell infusions also resulted in significantly improved T-cell proliferation in response to antigens that were not contained in the vaccine, as assessed by responses to staphylococcal enterotoxin B and cytomegalovirus antigens (P < 0.05). In the setting of lymphopenia, combined vaccine therapy and adoptive T-cell transfer fosters the development of enhanced memory T-cell responses.

Protective antibody responses to pneumococcal conjugate vaccine after autologous hematopoietic stem cell transplantation

Patients undergoing autologous hematopoietic stem cell transplantation (autoHCT) are at increased risk for infection with Streptococcus pneumoniae and have impaired antibody responses to pneumococcal polysaccharide vaccines. We performed this study to examine the ability of autoHCT patients to respond to a heptavalent pneumococcal conjugate vaccine (PCV7) given after transplantation and to determine whether there was a potential benefit of immunizing these patients before stem cell collection. Sixty-one patients scheduled for autoHCT were randomized to receive either PCV7 or no vaccine before stem cell collection. After stem cell reinfusion, all study patients were immunized with PCV7 at 3, 6, and 12 months. Pneumococcal immunoglobulin G antibody concentrations were measured at the time of each immunization and 1 month after the 12-month dose. Serotype-specific pneumococcal antibody concentrations were significantly higher in patients immunized with PCV7 before stem cell collection compared with patients not immunized before their stem cells were collected for 6 of 7 serotypes at 3 months, 6 of 7 serotypes at 6 months, 4 of 7 serotypes at 12 months, and 3 of 7 serotypes at 13 months. After the 3-dose series of PCV7 after autoHCT, >60% of study patients had protective concentrations of antibody to all 7 vaccine serotypes regardless of immunization before stem cell collection. Pneumococcal conjugate vaccine is immunogenic in autoHCT patients and may be an effective strategy to prevent invasive disease after transplantation.

Diminished neo-antigen response to keyhole limpet hemocyanin (KLH) vaccines in patients after treatment with chemotherapy or hematopoietic cell transplantation

Relapse is the most common cause of treatment failure for advanced cancer, even those treated with autologous hematopoietic cell transplantation (HCT). Effective tumor-specific immunotherapy may decrease relapse, however, this will fail if the immune system is unable to respond. We developed a strategy to test immune responses with a single injection of the bona fide neo-antigen KLH. The model was first tested in 37 normal volunteers using three KLH vaccines: Intracel KLH, Biosyn KLH, and Biosyn KLH + adjuvant. Despite finding the immunogenic epitope conserved in both products, intact Intracel KLH induced a better response compared to a purified 350/390 kDA subunit of KLH contained in the Biosyn KLH product. Addition of a synthetic oil adjuvant (Montanide ISA51) restored the response to a single injection of Biosyn KLH. A quantitative readout measured by a KLH-specific cellular and humoral response with isotype switching 1 month after KLH vaccination was established. To test the integrity of the adaptive immune response in cancer patients, we vaccinated 14 patients post-HCT and 19 patients with advanced cancer with KLH vaccines that elicited a 100% response rate in normal volunteers. In marked contrast to normal subjects, both responses were significantly impaired up to 16 months after autologous HCT with an intermediate response in advanced cancer patients. KLH vaccines are safe and require only a single injection to test neo-antigen responses providing an optimal platform for definitive testing of strategies to improve diminished immune recovery after chemotherapy or post-HCT.