Polyfunctional cytomegalovirus-specific CD4+ and pp65 CD8+ T cells protect against high-level replication after liver transplantation

Advances in cytomegalovirus-preventive strategies in solid organ transplantation: defending pre-emptive therapy

Prevention of cytomegalovirus (CMV) infection is an important part of clinical care provided to patients after solid organ transplantation. While the optimal preventive strategy has not been defined, most centers rely on universal prophylaxis or pre-emptive therapy. This article comments on recent studies designed to identify strategies that effectively reduce the incidence of late-onset CMV disease as the main problem associated with prophylaxis, and on recent data regarding the development of CMV-specific immunity depending on the CMV-preventive regimen used. Despite an apparent trend to prefer prophylaxis in clinical practice, this approach does not seem to be based on robust evidence.

Cytomegalovirus replication kinetics in solid organ transplant recipients managed by preemptive therapy

After allotransplantation, cytomegalovirus (CMV) may be transmitted from the donor organ, giving rise to primary infection in a CMV negative recipient or reinfection in one who is CMV positive. In addition, latent CMV may reactivate in a CMV positive recipient. In this study, serial blood samples from 689 kidney or liver transplant recipients were tested for CMV DNA by quantitative PCR. CMV was managed using preemptive antiviral therapy and no patient received antiviral prophylaxis. Dynamic and quantitative measures of viremia and treatment were assessed. Median peak viral load, duration of viremia and duration of treatment were highest during primary infection, followed by reinfection then reactivation. In patients who experienced a second episode of viremia, the viral replication rate was significantly slower than in the first episode. Our data provide a clear demonstration of the immune control of CMV in immunosuppressed patients and emphasize the effectiveness of the preemptive approach for prevention of CMV syndrome and end organ disease. Overall, our findings provide quantitative biomarkers which can be used in pharmacodynamic assessments of the ability of novel CMV vaccines or antiviral drugs to reduce or even interrupt such transmission.

[Immunological monitoring strategies for cytomegalovirus infection. Immune-based therapies]

T-cell response to cytomegalovirus (CMV) is essential in the control of viral replication. Quantification of functional CD4(+) and CD8(+) T lymphocytes against certain CMV-antigen specificities through flow cytometry, ELISPOT or the QuantiFERON-CMV kit allows fairly accurate estimation of the risk of active infection and CMV disease in solid organ transplantation (SOT). Combined virological and immunological monitoring of CMV infection could allow antiviral treatments to be individually tailored and optimized in SOT, although clinical experience is currently lacking. The adoptive transfer of CMV-specific T cells before selection with multimer HLA peptides or after activation and expansion ex vivo could be an effective therapeutic alternative in the management of active infection or organic CMV disease refractory to antiviral therapy. Several CMV vaccines have been developed, which have been shown to be safe and immunogenic in preclinical and Phase I clinical trials. However, to date, none of these vaccines has been evaluated in Phase III clinical trials and consequently none has been approved for clinical use.

Cytomegalovirus: recent progress in understanding pathogenesis and control

Cytomegalovirus continues to be an important pathogen in a variety of patient groups especially the neonate and the transplant recipient, and has implicated in a range of pathologies including inflammatory disease and in contributing to early death in ageing populations. This review will focus on advances in understanding the virus-host interaction and options for the new therapeutic control measures.

Differential decay kinetics of human cytomegalovirus glycoprotein B genotypes following antiviral chemotherapy

Background

The impact of different cytomegalovirus (HCMV) glycoprotein B (gB) genotypes on pathogenesis remains controversial.

Objectives

To investigate the effect of gB genotypes either as single infections or as part of multiple infections on the early kinetics of response to ganciclovir therapy.

Methods

Patients (n = 239) enrolled in a study of intravenous ganciclovir or valganciclovir for the treatment of HCMV disease were analysed by a gB genotype specific PCR to quantify the amount of each gB genotype present at initiation of therapy (baseline, day 0) and at days 3, 7, 14 and 21 post therapy.

Results and conclusions

In all gB groups (individual gB genotype infections and mixed genotype infections) there was a biphasic decline in viral load after therapy. The first phase half life (days 0–3) was ≤1 day and was followed over the next 18 days by a slower second phase decline with half lives ranging from 3.4 to 4.4 days. The 1st phase rapid decline in viral load was dependent upon gB genotype whereas the ultimate viral load reduction at day 21 was relatively insensitive to gB genotype. A strong correlation between 1st phase decline and extent of viral load reduction at day 21 was observed (r = 0.37; p = 0.002). These data imply that early reductions in HCMV load after therapy may be useful in predicting the duration of drug therapy needed to control HCMV replication.

Performance of the QuantiFERON-cytomegalovirus (CMV) assay for detection and estimation of the magnitude and functionality of the CMV-specific gamma interferon-producing CD8(+) T-cell response in allogeneic stem cell transplant recipients

The performance of the QuantiFERON-cytomegalovirus (CMV) assay was compared to that of a flow cytometry intracellular cytokine staining (ICS) method for the detection of CMV-specific gamma interferon (IFN-γ)-producing CD8(+) T-cell responses in allogeneic stem cell transplant (allo-SCT) recipients and for estimations of their magnitude and functionality. A total of 90 whole-blood specimens from 23 allo-SCT recipients was analyzed by both methods. Overall, the percentage of specimens that yielded concordant results by both methods was 68.8% (κ = 0.691; 95% confidence interval [CI], 0.548 to 0.835), and the sensitivity of the QuantiFERON-CMV assay for the detection of positive IFN-γ T-cell responses (>0.2 IU/ml), taking the ICS method as the reference, was 76.3%. The magnitude of IFN-γ-producing CD8(+) T-cell responses to CMV-specific peptides measured with the QuantiFERON-CMV assay correlated significantly (σ = 0.695; P = <0.001) with that of the total IFN-γ-producing CD8(+) T cells and dual-functional (IFN-γ/tumor necrosis factor alpha [TNF-α] [σ = 0.652; P = <0.001] and IFN-γ/CD107a [σ = 0.690; P = <0.001]) and trifunctional (IFN-γ/TNF-α/CD107a [σ = 0.679; P = >0.001]) CMV-specific CD8(+) T-cell responses, as quantitated by ICS. In summary, the data indicated that the QuantiFERON-CMV assay is less sensitive than the ICS method for the detection of CMV-specific IFN-γ-producing CD8(+) T-cell responses in the allo-SCT setting. Nevertheless, it allowed the estimation of the total and polyfunctional CMV-specific IFN-γ-producing CD8(+) T-cell responses in specimens that tested positive by both methods.

The development of Chinese specific human cytomegalovirus polyepitope recombinant vaccine

Human cytomegalovirus (HCMV) infection is a major cause of morbidity in the recipients of organ transplants and in the congenitally infected infants. HCMV vaccine has emerged as an effective approach to prevent HCMV infection particularly for the development of multiple viral antigens vaccination and human leukocyte antigen (HLA)-restricted polyepitope technology. As the Chinese population makes up more than one fifth of the population worldwide, it is important to develop HCMV vaccines more specific for the Chinese population by targeting Chinese-restricted HLA alleles and antigens. In the present study, we designed a novel chimeric polyepitope vaccine based on the replication-deficient adenovirus Ad5F35, which encodes 83 HCMV T cell epitopes from 15 different HCMV antigens, restricted to 14 HLA I and 7 HLA II alleles that cover 92% of the Chinese population. Our results show that the recombinant adenovirus vaccine Ad5F35-CTL·Th can be efficiently transfected and expressed in peripheral blood mononuclear cells (PBMCs) with little cytopathic activity. Ad5F35-CTL·Th can also be endogenously processed and presented by PBMCs. Ad5F35-CTL·Th-stimulated HCMV-specific cytotoxic T lymphocytes (CTLs) showed strong cytolytic activity against HCMV polyepitope-sensitized target cells. The CTL activity was accompanied by high levels of IFN-γ production after Ad5F35-CTL·Th stimulation. The specificity and vigorous response to the recombinant adenovirus vaccine in vitro makes it a potential candidate to be used for transplantation recipients or congenitally infected infants.

Polyfunctional T cells accumulate in large human cytomegalovirus-specific T cell responses

Large cytomegalovirus (CMV)-specific CD8 T-cell responses are observed in both young and, somewhat more often, old people. Frequent CMV reactivation is thought to exhaust these cells and render them dysfunctional so that larger numbers of them are needed to control CMV. Expansions of CMV-specific CD4 T cells are also seen but are less well studied. In this study, we examined the T-cell response to the dominant CMV pp65 and IE-1 antigens in healthy CMV-infected people across a wide age range (20 to 84 years) by using multicolor flow cytometry. CMV-specific T cells were characterized by the activation markers CD40 ligand (CD40L), interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) and the memory markers CD27 and CD45RA. The proportions of effector memory T cells increased in large responses, as did the proportions of polyfunctional CD8 (IFN-γ(+) IL-2(+/-) TNF-α(+)) and CD4 (CD40L(+/-) IFN-γ(+) IL-2(+) TNF-α(+)) T-cell subsets, while the proportion of naïve T cells decreased. The bigger the CD4 or CD8 T-cell response to pp65, the larger was the proportion of T cells with an advanced memory phenotype in the entire (including non-CMV-specific) T-cell compartment. In addition, the number of activation markers per cell correlated with the degree of T-cell receptor downregulation, suggesting increased antigen sensitivity in polyfunctional cells. In summary, our findings show that polyfunctional CMV-specific T cells were not superseded by dysfunctional cells, even in very large responses. At the same time, however, the memory subset composition of the entire T-cell compartment correlated with the size of the T-cell response to CMV pp65, confirming a strong effect of CMV infection on the immune systems of some, but not all, infected people.

Association of human cytomegalovirus viremia with human leukocyte antigens in liver transplantation recipients

Human cytomegalovirus (HCMV) reactivation is a common complication after liver transplantation (LT). Here, we investigated whether human leukocyte antigen (HLA)-matching was related to HCMV infection and subsequent graft failure after LT for hepatitis B virus  cirrhosis. This retrospective study reviewed 91 LT recipients. All the patients were grouped according to HLA-A, HLA-B, and HLA-DR locus matching. Clinical data were collected, including complete HLA-typing, HCMV viremia, graft failure, and the time of HCMV viremia. HLA typing was performed using a sequence-specific primer-polymerase chain reaction  kit. HCMV was detected by pp65 antigenemia using a commercial kit. The incidence of HCMV infection post-LT was 81.32%. Graft failure was observed in 16 of 91 (17.6%) patients during the 4-year study. The incidence of HCMV viremia was 100% (5/5), 91.4% (32/35), and 72.5% (37/51) in HLA-A two locus, one locus, and zero locus compatibility, respectively. Nevertheless, the degree of the HLA-A, HLA-B, or HLA-DR match did not influence the time of HCMV viremia, graft failure, or the time of graft failure after a diagnosis of HCMV viremia (all P > 0.05). An interesting discovery was that the risk of HCMV viremia tended to be higher in patients with better HLA-A compatibility. Graft failure, time of HCMV viremia, and graft failure after a diagnosis of HCMV viremia appear to be independent of HLA allele compatibility.

Viral factors influencing the outcome of human cytomegalovirus infection in liver transplant recipients

BACKGROUND

Cytomegalovirus (CMV) remains the leading viral cause of disease following orthotopic liver transplantation (OLT) despite the availability of antiviral agents for prophylaxis and therapy.

OBJECTIVE

Examine the viral factors that influence the outcome of CMV infection following valganciclovir prophylaxis or laboratory-guided preemptive therapy in OLT recipients.

STUDY DESIGN

The value of valganciclovir prophylaxis and laboratory-guided preemptive therapy for the prevention of CMV infection and disease was observed in 64 OLT recipients. Prophylaxis was given to all CMV seronegative recipients receiving a liver from a seropositive donor (D+R-; n=15), and all other recipients were randomised to receive either prophylaxis (n=24) or laboratory-guided preemptive therapy (n=25). Recipients were monitored for CMV DNAemia, viral load, emergence of antiviral resistant strains and co-infections.

RESULTS

CMV end-organ disease and antiviral resistant strains only occurred in D+R- recipients despite the use of prophylaxis in these patients. The D+R- recipients commencing prophylaxis immediately following transplantation had better outcomes compared to those for whom prophylaxis was delayed due to renal impairment. Prophylaxis reduced the incidence of CMV DNAemia, persistent infection, and high viral loads for CMV seropositive (D-R+and D+R+) recipients, but laboratory-guided preemptive therapy effectively controlled CMV infection and prevented disease in these OLT recipients.

CONCLUSION

Delaying the commencement of valganciclovir prophylaxis may be associated with worse outcomes for high-risk OLT recipients. Laboratory-guided pre-emptive therapy remains an alternative approach for seropositive recipients at lower risk of CMV disease.

Inflammation in common variable immunodeficiency is associated with a distinct CD8(+) response to cytomegalovirus

BACKGROUND

Common variable immunodeficiency is the most common primary immunodeficiency. A subset of patients has debilitating inflammatory complications.

OBJECTIVES

We investigated the role of cytomegalovirus (CMV), and the T-cell response targeted at this virus, in this inflammatory disease.

METHODS

Phenotypic and functional assays were used to profile CMV-specific T cells in patients with common variable immunodeficiency with and without inflammatory complications. Highly sensitive immunohistochemistry was used to detect CMV antigens at sites of inflammation.

RESULTS

Cytomegalovirus was significantly associated with inflammatory disease, which occurred in 31 of 43 (72%) virus-exposed patients and 8 of 31 (26%) naive patients (P = .0001). CMV pp65-NLVPMVATV epitope-specific CD8(+) T-cell frequencies were significantly elevated in inflammatory patients, but these cells did not show evidence of exhaustion, with low levels of programmed death-1 and high T-cell receptor avidity. Rather, they showed features consistent with high in vivo functionality and proliferative activity including reduced levels of the anti-inflammatory marker CD73 (1.67% of NLV(+) cells were CD73(+) vs 42.01% in noninflammatory patients; P = .004) and increased Ki-67 expression (37% vs 2% in noninflammatory patients; P < .0001). In vitro, the CMV-specific T cells showed high antigen-specific proliferative potential compared with cells from noninflammatory patients. By using sensitive immunohistochemistry, we detected for the first time viral antigen at the sites of inflammation, indicative of active viral replication.

CONCLUSION

Our data strongly support a direct role for CMV and a hyperreactive CMV-specific immune response in the debilitating chronic inflammatory complications of common variable immunodeficiency.

Bronchoalveolar CD4+ T cell responses to respiratory antigens are impaired in HIV-infected adults

Rationale

HIV-infected adults are at an increased risk of lower respiratory tract infections. HIV infection impairs systemic acquired immunity, but there is limited information in humans on HIV-related cell-mediated immune defects in the lung.

Objective

To investigate antigen-specific CD4⁺ T cell responses to influenza virus, Streptococcus pneumoniae and Mycobacterium tuberculosis antigens in bronchoalveolar lavage (BAL) and peripheral blood between HIV-infected individuals and HIV-uninfected Malawian adults.

Methods

We obtained BAL fluid and blood from HIV-infected individuals (n=21) and HIV-uninfected adults (n=24). We determined the proportion of T cell subsets including naive, memory and regulatory T cells using flow cytometry, and used intracellular cytokine staining to identify CD4⁺ T cells recognising influenza virus-, S pneumoniae- and M tuberculosis-antigens.

Main results

CD4⁺ T cells in BAL were predominantly of effector memory phenotype compared to blood, irrespective of HIV status (p<0.001). There was immune compartmentalisation with a higher frequency of antigen-specific CD4⁺ T cells against influenza virus, S pneumoniae and M tuberculosis retained in BAL compared to blood in HIV-uninfected adults (p<0.001 in each case). Influenza virus- and M tuberculosis-specific CD4⁺ T cell responses in BAL were impaired in HIV-infected individuals: proportions of total antigen-specific CD4⁺ T cells and of polyfunctional IFN-γ and TNF-α-secreting cells were lower in HIV-infected individuals than in HIV-uninfected adults (p<0.05 in each case).

Conclusions

BAL antigen-specific CD4⁺ T cell responses against important viral and bacterial respiratory pathogens are impaired in HIV-infected adults. This might contribute to the susceptibility of HIV-infected adults to lower respiratory tract infections such as pneumonia and tuberculosis.

Immunotherapy and vaccination after transplant: the present, the future

Vaccination and adoptive immunotherapy for herpes virus infections has become an attractive option for the control of a virus family that negatively affects transplantation. In the future, enhanced ability to select antigen-specific T cells without significant in vitro manipulation should provide new opportunities for refining and enhancing adoptive immunotherapeutic approaches. This article focuses on advances in the area of vaccinology for some of these infections and in the use of adoptive immunotherapy. At present, many of these approaches in transplant recipients have focused on infections such as human cytomegalovirus, but the opportunity to use these examples as proof of concept for other infections is discussed.

Signature profiles of CMV-specific T-cells in patients with CMV reactivation after hematopoietic SCT

Depletion of cellular immunity as a consequence of conditioning before allogeneic hematopoietic SCT (HSCT) frequently results in CMV reactivation, which may in turn lead to life-threatening infections and require timely antiviral treatment. We have investigated the functional signatures of CMV-specific CD4+ and CD8+ T-cells in 191 samples from 118 individuals. We compared healthy donors with both patients with high and undetectable viral loads, and those who controlled and did not control their CMV reactivations. Polychromatic flow-cytometric measurements of CD154 (CD40L), intracellular cytokines (IFNγ, IL2) and a degranulation marker (CD107a) allowed us to assess the functional status of various T-cells simultaneously. We found that dual IFNγ/IL2-producing CD8+ T-cells were present in patients controlling their CMV reactivations but absent from non-controllers. CD8+ T-cells that produce only IFNγ were the most abundant subtype, but they most likely represent non-protective memory cells. Distinct functional signatures were examined by hierarchical clustering, and this revealed that, unlike polyfunctional CD8+ T-cells, CD8+ T-cells that produce IFNγ alone were not functioning in concert with other subsets. In conclusion, our study revealed functional signatures that may be useful for immune monitoring, and it could change the interpretation of previous studies that assessed only IFNγ.

Human cytomegalovirus immunity and immune evasion

Human cytomegalovirus (HCMV) infection induces both innate immune responses including Natural Killer cells as well as adaptive humoral and cell mediated (CD4+ helper, CD8+ cytotoxic and γδ T cell) responses which lead to the resolution of acute primary infection. Despite such a robust primary immune response, HCMV is still able to establish latency. Long term memory T cell responses are maintained at high frequency and are thought to prevent clinical disease following periodic reactivation of the virus. As such, a balance is established between the immune response and viral reactivation. Loss of this balance in the immunocompromised host can lead to unchecked viral replication following reactivation of latent virus, with consequent disease and mortality. HCMV encodes multiple immune evasion mechanisms that target both the innate and acquired immune system. This article describes the current understanding of Natural killer cell, antibody and T cell mediated immune responses and the mechanisms that the virus utilizes to subvert these responses.

Immunotherapy and vaccination after transplant: the present, the future

Vaccination and adoptive immunotherapy for herpes virus infections has become an attractive option for the control of a virus family that negatively affects transplantation. In the future, enhanced ability to select antigen-specific T cells without significant in vitro manipulation should provide new opportunities for refining and enhancing adoptive immunotherapeutic approaches. This article focuses on advances in the area of vaccinology for some of these infections and in the use of adoptive immunotherapy. At present, many of these approaches in transplant recipients have focused on infections such as human cytomegalovirus, but the opportunity to use these examples as proof of concept for other infections is discussed.

NK cells as effectors of acquired immune responses: effector CD4+ T cell-dependent activation of NK cells following vaccination

We characterized vaccine-induced cellular responses to rabies virus in naive adult volunteers. Contrary to current paradigms, we observed potent and prolonged in vitro NK cell cytokine production and degranulation responses after restimulation of PBMCs with inactivated rabies virus in vaccinated, but not in unvaccinated, individuals. This "recall" NK cell response was absolutely dependent on Ag-specific IL-2 from CD45RO(+) CD4(+) T cells as well as IL-12 and IL-18 from accessory cells. Importantly, NK cells represented over 70% of all IFN-gamma-secreting and degranulating cells in the first 12-18 h after virus rechallenge indicating they may be required for rapid control of infection after vaccination. Activation of NK cells may be a critical function of IL-2-secreting effector memory T cells. Although IL-2-dependent postvaccination NK cell activation has been reported previously, this is the first time the magnitude of this effect and its contribution to the overall vaccine-induced response has been appreciated and the mechanisms of NK activation postvaccination have been elucidated. Our data will allow standard protocols for evaluating vaccine-induced immunity to be adapted to assess NK cell effector responses.

Human peripheral blood and bone marrow Epstein-Barr virus-specific T-cell repertoire in latent infection reveals distinct memory T-cell subsets

EBV infection leads to life-long viral persistence. Although EBV infection can result in chronic disease and malignant transformation, most carriers remain disease-free as a result of effective control by T cells. EBV-specific IFN-gamma-producing T cells could be demonstrated in acute and chronic infection as well as during latency. Recent studies, however, provide evidence that assessing IFN-gamma alone is insufficient to assess the quantity and quality of a T-cell response. Using overlapping peptide pools of latent EBV nuclear antigen 1 and lytic BZLF-1 protein and multicolor flow cytometry, we demonstrate that the majority of ex vivo EBV-reactive T cells in healthy virus carriers are indeed IL-2- and/or TNF-producing memory cells, the latter being significantly more frequent in BM. After in vitro expansion, a substantial number of EBV-specific CD4(+) and CD8(+) T cells retained a CC-chemokine receptor 7 (CCR7)-positive memory phenotype. Based on their cytokine profiles, six different EBV-specific T-cell subsets could be distinguished with TNF-single or TNF/IL-2-double producing cells expressing the highest CCR7 levels resembling early-differentiated memory T cells. Our study delineates the memory T-cell profile of a protective immune response and provides a basis for analyzing T-cell responses in EBV-associated diseases.

Neonatal innate TLR-mediated responses are distinct from those of adults

The human neonate and infant are unduly susceptible to infection with a wide variety of microbes. This susceptibility is thought to reflect differences from adults in innate and adaptive immunity, but the nature of these differences is incompletely characterized. The innate immune response directs the subsequent adaptive immune response after integrating information from TLRs and other environmental sensors. We set out to provide a comprehensive analysis defining differences in response to TLR ligation between human neonates and adults. In response to most TLR ligands, neonatal innate immune cells, including monocytes and conventional and plasmacytoid dendritic cells produced less IL-12p70 and IFN-alpha (and consequently induced less IFN-gamma), moderately less TNF-alpha, but as much or even more IL-1beta, IL-6, IL-23, and IL-10 than adult cells. At the single-cell level, neonatal innate cells generally were less capable of producing multiple cytokines simultaneously, i.e., were less polyfunctional. Overall, our data suggest a robust if not enhanced capacity of the neonate vs the adult white-blood cell TLR-mediated response to support Th17- and Th2-type immunity, which promotes defense against extracellular pathogens, but a reduced capacity to support Th1-type responses, which promote defense against intracellular pathogens.

Polyfunctional T lymphocytes are in the peripheral blood of donors naturally immune to coccidioidomycosis and are not induced by dendritic cells

Coccidioidomycosis is a fungal infection endemic in the southwestern United States that is increasing in incidence. While cellular immunity correlates with protection from clinical illness, the precise elements of that response are undefined. Using the coccidioidal antigen preparation T27K and multiparametric flow cytometry, the in vitro frequency of polyfunctional T lymphocytes in the peripheral blood of naturally immune healthy donors and those who were nonimmune was determined. Polyfunctional CD4 lymphocytes, defined as producing intracellular interleukin 2 (IL-2), gamma interferon (IFN-gamma), and tumor necrosis factor alpha simultaneously, had a frequency of 137 per 400,000 events among peripheral blood mononuclear cells (PBMC) of immune donors compared to 11 per 400,000 PBMC from nonimmune donors (P = 0.03). When monocyte-derived mature dendritic cells pulsed with T27K (mDC(T27K)) were used for antigen presentation, the frequency of polyfunctional CD4 T lymphocytes did not significantly increase for either group, although mDC(T27K) did significantly increase the concentrations of IL-2 and IFN-gamma released by PBMC from nonimmune donors (P = 0.02). After in vitro stimulation with T27K, polyfunctional CD4 and CD8 lymphocytes of PBMC from immune donors had a mixture of low- and high-expression CCR7 cells, suggesting both effector and central memory, compared with predominantly high-expression CCR7 cells when PBMC were incubated with the mitogen phytohemagglutinin (P = 0.03). These data demonstrate the presence of polyfunctional T lymphocytes in the peripheral blood of individuals with coccidioidal immunity and suggest a model for the in vitro testing of vaccine candidates for coccidioidomycosis.

Neonatal immunization with Listeria monocytogenes induces T cells with an adult-like avidity, sensitivity, and TCR-Vbeta repertoire, and does not adversely impact the response to boosting

Listeria monocytogenes (Lm) holds promise as a neonatal vaccine vehicle. Here we show that Lm immunized neonatal mice reached maximal Ag-specific CD8(+) T cell expansion after only a single immunization, while adults required two doses. Ag-specific CD4(+) T cell expansion in both age groups required a boost to reach its peak. Neither functional avidity, sensitivity, nor the TCR-Vbeta repertoire of the Ag-specific T cells differed between mice immunized as neonates or adults. Lastly, neonatal immunization did not decrease protection or preclude a booster response. Overall, our data provide further evidence in support of immunization at birth as a feasible public health strategy to combat early life infections.

Impact of donor CMV status on viral infection and reconstitution of multifunction CMV-specific T cells in CMV-positive transplant recipients

Reconstitution of cytomegalovirus (CMV)-specific CD8(+) T cells is essential to the control of CMV infection in CMV-positive recipients (R(+)) after allogeneic hematopoietic stem cell transplantation (HCT). Six-color flow cytometry was used to assess the functional profile of CMV-specific CD8(+) T cells in 62 of 178 R(+) HCT recipients followed virologically for CMV reactivation. R(+) recipients receiving grafts from CMV-negative donors (D(-); D(-)/R(+)) reconstituted fewer multifunctional CD8(+) T cells expressing tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1beta (MIP-1beta), and CD107 in addition to interferon-gamma (IFN-gamma), compared with D(+)/R(+) recipients. Unlike monofunctional CD8(+) T cells secreting IFN-gamma, which were abundantly generated during CMV reactivation in D(-)/R(+) recipients, the relative lack of multifunctional CD8(+) T cells persisted until at least 1 year post-HCT. D(-)/R(+) recipients were more likely to require recurrent and prolonged use of antivirals. These findings were robust to statistical adjustment for pretransplant factors, as well as for posttransplant factors including graft-versus-host disease (GVHD) and its treatment by steroids. These analyses suggest that D(+)/R(+) transplants, on average, generate higher levels of multifunctional CMV-specific T cells and require less antiviral therapy compared with D(-)/R(+) HCT recipients. These results highlight the benefit of D(+) donors in improving outcomes of R(+) HCT recipients by reducing the duration and recurrent need of antiviral treatment, aided by increased levels of multifunctional CMV-specific T cells.

A CMV DNA vaccine primes for memory immune responses to live-attenuated CMV (Towne strain)

CMV-seronegative subjects vaccinated intramuscularly or intradermally with a DNA vaccine encoding pp65, IE1, and gB were administered live-attenuated CMV (Towne) to characterize immune priming by the DNA vaccine. CMV-specific memory T-cells (detected by standard ELISPOT assay in only 20% of subjects) were detected by IFN-gamma cultured ELISPOT assay in 60% of subjects primed intramuscularly and correlated with immune responses after Towne. The median time to first pp65 T-cell and gB antibody response after Towne was 14 days for DNA-primed subjects vs. 28 days for controls administered Towne only (p=0.02 and 0.03, respectively). Furthermore, there was a trend toward more DNA-vaccinated subjects than controls developing a gB-specific IFN-gamma T-cell response after Towne administration (47% vs. 0%, p=0.06).