Immune reconstitution and vaccination outcome in HIV-1 infected children: present knowledge and future directions

B-cell immunity and vaccine induced antibody protection reveal the inefficacy of current vaccination schedule in infants with perinatal HIV-infection in Mozambique, Africa

BACKGROUND

Despite antiretroviral treatment (ART), immune dysfunction persists in children with perinatal HIV infection (HEI). Here we investigated the impact of HIV status on maternal antibody (Ab) passage, long-term vaccine induced immunity and B-cell maturation.

METHODS

46 HIV Exposed Uninfected (HEU), 43 HEI, and 15 HIV unexposed uninfected (HUU) infants were vaccinated with 3 doses of DTaP-HepB-Hib-PCV10-OP at 2, 3, and 4 months at Matola Provincial Hospital, Maputo, Mozambique. Tetanus toxoid specific (TT) IgG, HIV Ab and B-cell phenotype characteristics were evaluated at entry, pre-ART, 5, 10, and 18 months in this longitudinal cohort study.

FINDINGS

Baseline (maternal) plasma TT Ab levels were significantly lower in HEI compared to both HEU and HUU and a faster decay of TT Ab was observed in HEI compared to HEU with significantly lower TT Ab levels at 10 and 18 months of age. TT unprotected (UP) (≤0.1 IU/mL) HEI showed higher HIV-RNA at entry and higher longitudinal HIV viremia (Area Under the Curve) compared to TT protected (P) HEI. A distinct HIV-Ab profile was found at entry in HEI compared to HEU. B-cell phenotype showed a B-cell perturbation in HEI vs HEU infants at entry (mean age 40.8 days) with lower transitional CD10+CD19+ B-cells and IgD+CD27- naive B-cells and an overall higher frequency of IgD-CD27- double negative B-cell subsets in HEI.

INTERPRETATION

B-cell perturbation, presenting with higher double negative IgD-CD27- B-cells was observed in neonatal age and may play a major role in the B-cell exhaustion in HEI. The ability to maintain TT protective Ab titers over time is impaired in HEI with uncontrolled viral replication and the current vaccination schedule is insufficient to provide long-term protection against tetanus.

FUNDING

This work was supported by: NIH grant to SP (5R01AI127347-05); Children's Hospital Bambino Gesú (Ricerca corrente 2019) to NC, and Associazione Volontari Bambino Gesù to PP.

Persons with HIV Develop Spike-Specific Lymph Node Germinal Center Responses following SARS-CoV-2 Vaccination

COVID-19 disproportionately affects persons with HIV (PWH) in worldwide locations with limited access to SARS-CoV-2 vaccines. PWH exhibit impaired immune responses to some, but not all, vaccines. Lymph node (LN) biopsies from PWH demonstrate abnormal LN structure, including dysregulated germinal center (GC) architecture. It is not clear whether LN dysregulation prevents PWH from mounting Ag-specific GC responses in the draining LN following vaccination. To address this issue, we longitudinally collected blood and draining LN fine needle aspiration samples before and after SARS-CoV-2 vaccination from a prospective, observational cohort of 11 PWH on antiretroviral therapy: 2 who received a two-dose mRNA vaccine series and 9 who received a single dose of the Ad26.COV2.S vaccine. Following vaccination, we observed spike-specific Abs, spike-specific B and T cells in the blood, and spike-specific GC B cell and T follicular helper cell responses in the LN of both mRNA vaccine recipients. We detected spike-specific Abs in the blood of all Ad26.COV2.S recipients, and one of six sampled Ad26.COV2.S recipients developed a detectable spike-specific GC B and T follicular helper cell response in the draining LN. Our data show that PWH can mount Ag-specific GC immune responses in the draining LN following SARS-CoV-2 vaccination. Due to the small and diverse nature of this cohort and the limited number of available controls, we are unable to elucidate all potential factors contributing to the infrequent vaccine-induced GC response observed in the Ad26.COV2.S recipients. Our preliminary findings suggest this is a necessary area of future research.

Rubella antibodies in vertically and horizontally HIV-infected young adults vaccinated early in life and response to a booster dose in those with seronegative results

BACKGROUND

Very limited data are available on the persistence of rubella antibodies in vertically HIV-infected individuals who were vaccinated early in life.

METHODS

Prospective, cohort study on 4 groups of patients: 96 vertically HIV-1-infected individuals (v-HIV), 69 horizontally HIV-1-infected individuals (h-HIV), 93 healthy controls previously vaccinated for rubella (vac-CON) and 20 healthy controls with history of rubella disease (dis-CON). A blood sample was collected and rubella antibodies were analyzed by ELISA. Rubella antibodies above 10 IU/mL were considered protective. Individuals with seronegative results were offered an extra MMR vaccine dose and were tested at least 30 days afterwards.

RESULTS

Time since previous rubella vaccination was similar in v-HIV, h-HIV and vac-CON (16, 11 and 11 years; p = 0.428). v-HIV and h-HIV were also comparable regarding median CD4 T cells (613 and 614 cells/mm³; p = 0.599) and percentage on ART (93.8% and 98.6%; p = 0.135) at study entry. v-HIV had less individuals on virological suppression (63.5%) compared to 85.5% in h-HIV (p < 0.001). Rubella seropositivity and antibodies were significantly lower in v-HIV compared to h-HIV (32.3% vs 65.5%, 4.3 IU/mL vs 21.1 IU/mL; p < 0.001). Time interval between the last rubella vaccine dose and study entry was associated with an increase of rubella seronegativity, with a 7% higher chance of seronegativity for each one-year increase. After an extra MMR dose, 40 out of 48 (83.3%) seronegative individuals responded, with no significant difference among groups considering rubella seropositivity and antibody levels.

CONCLUSION

As vertically HIV-infected individuals reach adolescence and adulthood, assessment of vaccine antibodies can identify those who might benefit from an extra vaccine dose.

Characterization of Serum and Mucosal SARS-CoV-2-Antibodies in HIV-1-Infected Subjects after BNT162b2 mRNA Vaccination or SARS-CoV-2 Infection

Only limited data are available regarding the immunogenicity of the BNT162b2 mRNA vaccine in HIV-1+ patients. Therefore, we investigated the humoral immune response after BNT162b2-mRNA vaccination or SARS-CoV-2 infection in HIV-1+ patients on antiretroviral therapy compared to HIV-1-uninfected subjects. Serum and saliva samples were analysed by SARS-CoV-2 spike-specific IgG and IgA ELISAs and a surrogate neutralization assay. While all subjects developed anti-spike IgG and IgA and neutralizing antibodies in serum after two doses of BNT162b2 mRNA vaccine, the HIV-1+ subjects displayed significantly lower neutralizing capacity and anti-spike IgA in serum compared to HIV-1-uninfected subjects. Serum levels of anti-spike IgG and neutralizing activity were significantly higher in vaccinees compared to SARS-CoV-2 convalescents irrespective of HIV-1 status. Among SARS-CoV-2 convalescents, there was no significant difference in spike-specific antibody response between HIV-1+ and uninfected subjects. In saliva, anti-spike IgG and IgA antibodies were detected both in vaccinees and convalescents, albeit at lower frequencies compared to the serum and only rarely with detectable neutralizing activity. In summary, our study demonstrates that the BNT162b2 mRNA vaccine induces SARS-CoV-2-specific antibodies in HIV-1-infected patients on antiretroviral therapy, however, lower vaccine induced neutralization activity indicates a lower functionality of the humoral vaccine response in HIV-1+ patients.

Nutritional Supplementation to Increase Influenza Vaccine Response in Children Living With HIV: A Pilot Clinical Trial

AIMS

Vaccine response is poor among children living with HIV. The gut microbiota has been identified as a potential target to improve vaccine immunogenicity, but data are scarce in the context of HIV infection.

METHODS

Pilot, double-blind, randomized placebo-controlled trial in which 24 HIV-infected children were randomized to receive a mixture of symbiotics, omega-3/6 fatty acids, and amino acids or placebo for 4 weeks, each in combination with ART, and were then immunized against influenza. Vaccine response and safety of the nutritional supplementation were the primary outcomes.

RESULTS

Eighteen HIV-infected children completed the follow-up period (mean age 11.5 ± 4.14 years, 61% female). The nutritional supplement was safe but did not enhance the response to the influenza vaccine. A 4-fold rise in antibody titers was obtained in only 37.5% of participants in the intervention arm vs. 40% in the placebo. No immunological or inflammatory predictors of vaccine response were identified.

CONCLUSIONS

In this exploratory study, a 4-week course of symbiotics did not increase influenza vaccine immunogenicity in HIV-infected children. Larger studies are warranted to address the potential of modulating the microbiome in children living with HIV.

Artificial Intelligence Applied to in vitro Gene Expression Testing (IVIGET) to Predict Trivalent Inactivated Influenza Vaccine Immunogenicity in HIV Infected Children

The number of patients affected by chronic diseases with special vaccination needs is burgeoning. In this scenario, predictive markers of immunogenicity, as well as signatures of immune responses are typically missing even though it would especially improve the identification of personalized immunization practices in these populations. We aimed to develop a predictive score of immunogenicity to Influenza Trivalent Inactivated Vaccination (TIV) by applying deep machine learning algorithms using transcriptional data from sort-purified lymphocyte subsets after in vitro stimulation. Peripheral blood mononuclear cells (PBMCs) collected before TIV from 23 vertically HIV infected children under ART and virally controlled were stimulated in vitro with p09/H1N1 peptides (stim) or left unstimulated (med). A multiplexed-qPCR for 96 genes was made on fixed numbers of 3 B cell subsets, 3 T cell subsets and total PBMCs. The ability to respond to TIV was assessed through hemagglutination Inhibition Assay (HIV) and ELIspot and patients were classified as Responders (R) and Non Responders (NR). A predictive modeling framework was applied to the data set in order to define genes and conditions with the higher predicted probability able to inform the final score. Twelve NR and 11 R were analyzed for gene expression differences in all subsets and 3 conditions [med, stim or Δ (stim-med)]. Differentially expressed genes between R and NR were selected and tested with the Adaptive Boosting Model to build a prediction score. The score obtained from subsets revealed the best prediction score from 46 genes from 5 different subsets and conditions. Calculating a combined score based on these 5 categories, we achieved a model accuracy of 95.6% and only one misclassified patient. These data show how a predictive bioinformatic model applied to transcriptional analysis deriving from in-vitro stimulated lymphocytes subsets may predict poor or protective vaccination immune response in vulnerable populations, such as HIV-infected individuals. Future studies on larger cohorts are needed to validate such strategy in the context of vaccination trials.

Innate Lymphoid Cell Activation and Sustained Depletion in Blood and Tissue of Children Infected with HIV from Birth Despite Antiretroviral Therapy

Innate lymphoid cells (ILCs) are important for response to infection and for immune development in early life. HIV infection in adults depletes circulating ILCs, but the impact on children infected from birth remains unknown. We study vertically HIV-infected children from birth to adulthood and find severe and persistent depletion of all circulating ILCs that, unlike CD4+ T cells, are not restored by long-term antiretroviral therapy unless initiated at birth. Remaining ILCs upregulate genes associated with cellular activation and metabolic perturbation. Unlike HIV-infected adults, ILCs are also profoundly depleted in tonsils of vertically infected children. Transcriptional profiling of remaining ILCs reveals ongoing cell-type-specific activity despite antiretroviral therapy. Collectively, these data suggest an important and ongoing role for ILCs in lymphoid tissue of HIV-infected children from birth, where persistent depletion and sustained transcriptional activity are likely to have long-term immune consequences that merit further investigation.

How to dissect the plasticity of antigen-specific immune response: a tissue perspective

Generation of antigen-specific humoral responses following vaccination or infection requires the maturation and function of highly specialized immune cells in secondary lymphoid organs (SLO), such as lymph nodes or tonsils. Factors that orchestrate the dynamics of these cells are still poorly understood. Currently, experimental approaches that enable a detailed description of the function of the immune system in SLO have been mainly developed and optimized in animal models. Conversely, methodological approaches in humans are mainly based on the use of blood-associated material because of the challenging access to tissues. Indeed, only few studies in humans were able to provide a discrete description of the complex network of cytokines, chemokines and lymphocytes acting in tissues after antigenic challenge. Furthermore, even fewer data are currently available on the interaction occurring within the complex micro-architecture of the SLO. This information is crucial in order to design particular vaccination strategies, especially for patients affected by chronic and immune compromising medical conditions who are under-vaccinated or who respond poorly to immunizations. Analysis of immune cells in different human tissues by high-throughput technologies, able to obtain data ranging from gene signature to protein expression and cell phenotypes, is needed to dissect the peculiarity of each immune cell in a definite human tissue. The main aim of this review is to provide an in-depth description of the current available methodologies, proven evidence and future perspectives in the analysis of immune mechanisms following immunization or infections in SLO.

Lymphocyte homeostasis is maintained in perinatally HIV-infected patients after three decades of life

Background

While immunosenescence, defined as reduced production of new lymphocytes, restriction of T-cell receptor repertoire and telomeres shortening, has been extensively evaluated in HIV-infected children and adults, no data about these parameters are available in perinatally-infected patients with very long-lasting HIV infection.

Methods

We compared thymic and bone marrow output, telomere length (measured by Real-Time PCR) and T-cell receptor repertoire (determined by spectratyping) of 21 perinatally HIV-infected subjects (with a median of 27 years of infection) with those of 19 age-matched non-perinatally HIV-infected patients and 40 healthy controls. All patients received a combined antiretroviral therapy.

Results

While thymic and bone marrow output were not different among the analyzed groups, telomere length in peripheral blood cells and T-cell receptor diversity were significantly lower in HIV-perinatally and non-perinatally infected individuals compared to healthy controls.

Conclusions

In HIV-infected subjects, a normal thymic output together with a reduced telomere length and a restricted T-cell receptor repertoire could be explained by the shift of newly produced cells into memory subsets. This phenomenon may allow to control viral infection and maintain peripheral homeostasis.

Prolonged Impairment of Immunological Memory After Anti-CD20 Treatment in Pediatric Idiopathic Nephrotic Syndrome

Anti-CD20 therapy is effective in idiopathic nephrotic syndrome (INS). However, transient or sustained hypogammaglobulinemia predisposing to an increased risk of infectious diseases can follow treatment in some patients. We analyzed the long-term effects of anti-CD20 therapy on immunological memory in 27 frequently-relapsing/steroid-dependent INS pediatric patients after more than 4 years from the first and at least 2 years from the last anti-CD20 infusion. Twenty-one INS children, never treated with anti-CD20 and under an intense oral immunosuppression with prednisone, mycophenolate mofetil, and calcineurin inhibitors were also included as control group. Levels of circulating B-cell subpopulations, total serum immunoglobulins and IgG and memory B cells directed against hepatitis B virus (HBV) and tetanus were determined and correlated with clinical characteristics. Nine patients never relapsed after more than 2 years from the last anti-CD20 administration (5 after the first, 3 after the second, and 1 after the fifth infusion). At last follow-up, most patients showed a complete recovery and normalization of total (27/27), transitional (27/27), and mature-naïve B cells (25/27). However, a sustained and significant reduction of total memory (20/27) and switched memory (21/27) B cells was found in most patients. 11/27 patients showed hypogammaglobulinemia at last follow-up and, among these, four presented with a severe hypogammaglobulinemia (IgG < 160 mg/dl). In contrast, no patient in the control group developed a severe hypogammaglobulinemia. Age at the time of first anti-CD20 administration was positively associated with IgG levels at last follow-up (p = 0.008); accordingly, younger patients had an increased risk of hypogammaglobulinemia (p = 0.006). Furthermore, severe hypogammaglobulinemia and delayed switched memory B-cell reconstitution were more frequent in non-relapsing patients. Reduced IgG levels against HBV and tetanus were observed at baseline and further declined at last follow-up. Antigen-specific memory B-cells were induced by re-immunization, but specific IgG titers remained low. In conclusion, anti-CD20 therapy can be disease-modifying in some INS patients. However, a prolonged impairment of immunological memory occurs frequently, independently from the number of anti-CD20 infusions, particularly in younger patients. Re-immunization may be necessary in these patients.

OMIC Technologies and Vaccine Development: From the Identification of Vulnerable Individuals to the Formulation of Invulnerable Vaccines

Routine vaccination is among the most effective clinical interventions to prevent diseases as it is estimated to save over 3 million lives every year. However, the full potential of global immunization programs is not realised because population coverage is still suboptimal. This is also due to the inadequate immune response and paucity of informative correlates of protection upon immunization of vulnerable individuals such as newborns, preterm infants, pregnant women, and elderly individuals as well as those patients affected by chronic and immune compromising medical conditions. In addition, these groups are undervaccinated for a number of reasons, including lack of awareness of vaccine-preventable diseases and uncertainty or misconceptions about the safety and efficacy of vaccination by parents and healthcare providers. The presence of these nonresponders/undervaccinated individuals represents a major health and economic burden to society, which will become particularly difficult to address in settings with limited public resources. This review describes innovative and experimental approaches that can help identify specific genomic profiles defining nonresponder individuals for whom specific interventions might be needed. We will provide examples that show how such information can be useful to identify novel biomarkers of safety and immunogenicity for future vaccine trials. Finally, we will discuss how system biology “OMICs” data can be used to design bioinformatic tools to predict the vaccination outcome providing genetic and molecular “signatures” of protective immune response. This strategy may soon enable identification of signatures highly predictive of vaccine safety, immunogenicity, and efficacy/protection thereby informing personalized vaccine interventions in vulnerable populations.

Effect of HIV-exposure and timing of anti-retroviral treatment on immunogenicity of trivalent live-attenuated polio vaccine in infants

Introduction

The prevalence of HIV infection in South African pregnant women has been approximately 30% over the past decade; however, there has been a steady decline in mother-to-child transmission of HIV from 8% in 2008 to <2% in 2015. We evaluated the immunogenicity of live-attenuated trivalent oral polio vaccine (OPV) following the primary vaccination series (doses at birth, 6, 10 and 14 weeks of age) in HIV-exposed uninfected (HEU), HIV-infected infants initiated on early anti-retroviral treatment (HIV+/ART+), HIV-infected infants on deferred ART (HIV+/ART-) and HIV-unexposed infants (HU) as the referent group.

Methods

Serum polio neutralization antibody titres were evaluated to serotype-1, serotype-2 and serotype-3 at 6, 10 and 18 weeks of age. Antibody titres ≥8 were considered seropositive and sero-protective.

Results

At 18 weeks of age, following the complete primary series of four OPV doses, no differences in GMTs, percentage of infants with sero-protective titres and median fold change in antibody titre (18 weeks vs 6 weeks) were observed in HEU infants (n = 114) and HIV+/ART+ infants (n = 162) compared to HU infants (n = 104) for the three polio serotypes. However, comparing HIV+/ART- infants (n = 70) to HU infants at 18 weeks of age, we observed significantly lower GMTs for serotype-1 (p = 0.022), serotype-2 (p<0.001) and serotype-3 (p<0.001), significantly lower percentages of infants with sero-protective titres for the three serotypes (p<0.001), and significantly lower median fold change in antibody titre for serotype-1 (p = 0.048), serotype-2 (p = 0.003) and serotype-3 (p = 0.008).

Conclusion

Delaying initiation of ART in HIV-infected infants was associated with an attenuated immune response to OPV following a four-dose primary series of vaccines, whereas immune responses to OPV in HIV-infected children initiated on ART early in infancy and HEU children were similar to HU infants.

Seroprevalence of measles vaccine antibody response in vertically HIV-infected children, in Morocco

BACKGROUND

The widespread use of an effective and safe vaccine to measles has substantially decreased morbidity and mortality from this epidemic. Nevertheless, HIV-infected children vaccinated against measles may develop an impaired vaccine response and remain susceptible to this disease. In Morocco, infants are routinely vaccinated against measles, regardless of their HIV serostatus. An evaluation of the immunization of these children may be of paramount importance to implement timely measures aimed at preventing measles transmission.

METHODS

In this study, we have enrolled 114 children vaccinated against measles, 50 children prenatally infected with HIV and 64 HIV-uninfected children. For all children, blood samples were taken to measure anti-measles IgG by EIA and CD4 count by flow cytometry. Additionally, HIV viral load was determined by automated real time PCR, for HIV-infected children.

RESULTS

The seroprotective rate of IgG anti-measles antibodies was significantly lower among HIV-infected children (26%) compared with HIV-uninfected children (73%) (p < 0.001). Within HIV-infected children group, the comparison of variables between children without seroprotective seroconversion to measles and those with seroprotective immunity, displayed that sex and age were not statistically different, p > 0.999 and p = 0.730, respectively. However, CD4 count was lower among children with negative serostatus to measles (23% versus 32%, p < 0.001). Furthermore, viral load was higher, with 2.91 log10 ± 2.24 versus 1.7 log10 ± 1.5 (p = 0.042). Finally, 62% of children with a negative vaccine response to measles were under HAART therapy, versus 92% (p = 0.008).

CONCLUSION

The majority of HIV-infected children vaccinated against measles develop a suboptimal seroprotective titer, and therefore remain at risk for this highly infectious disease. These data in combination with international recommendations, including recent WHO guidance on vaccination of HIV-infected children, suggest there is a need for national measures to prevent these children from measles.

Effect of HIV exposure and timing of antiretroviral therapy initiation on immune memory responses to diphtheria, tetanus, whole cell pertussis and hepatitis B vaccines

OBJECTIVES

We evaluated memory responses and antibody persistence to diphtheria-toxoid, tetanus-toxoid, whole-cell-pertussis (DTwP), and Hepatitis-B vaccines in HIV-unexposed, HIV-exposed-uninfected and HIV-infected children previously randomized to initiate time-limited ART at 6-10 weeks (ART-Immed) or when clinically/immunologically indicated (ART-Def).

METHODS

All children received DTwP booster at 15-18 months. Antibodies were measured for pertussis-toxoid, filamentous haemagglutinin (FHA), diphtheria-toxoid, tetanus-toxoid, and hepatitis-B prior to booster, 1-2 weeks post-booster and at 24 months of age.

RESULTS

Pre-booster antibody GMC were lower in HIV-infected groups than HIV-unexposed children for all epitopes. Post-booster and at 24 months of age, the ART-Def group had lower GMCs and antibody proportion ≥0.1 IU/ml for tetanus-toxoid and diphtheria-toxoid compared to HIV-unexposed children. At 24 months of age, the ART-Immed group had higher GMCs, and more likely to maintain antibody titres ≥1.0 IU/ml to tetanus-toxoid and diphtheria-toxoid compared to HIV-unexposed children. Compared to HIV-unexposed children, at 15 and 24 months of age, persistence of antibody to HBsAg of ≥10 mIU/ml was similar in the ART-Immed group but lower among the ART-Def group. Antibody kinetics indicated more robust memory responses in HIV-exposed-uninfected than HIV-unexposed children to diphtheria-toxoid and wP.

CONCLUSION

HIV-infected children not on ART at primary vaccination had poorer memory responses, whereas HIV-exposed-uninfected children mounted robust memory responses.

Active prophylaxis for respiratory syncytial virus: current knowledge and future perspectives

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children but represents also an important cause of morbidity in adults, particularly in the elderly and immunocompromised persons. Despite its global impact on human health, no effective treatment is available except for supportive care and no safe vaccine has been licensed yet. Vaccine development has been hindered by several factors including vaccine enhanced disease associated with formalin-inactivated RSV vaccine, ethical concerns and lack of consensus concerning the most appropriate target antigen. In this review, we analyze history of RSV vaccine and current approaches for preventing RSV including live-attenuated, vector-based, subunit, nucleic acid-based, particle-based vaccines and we debate about concerns on target population, correlates of protection and obstacles that are slowing the progress toward a successful RSV vaccination strategy.

Impaired Development and Expansion of Germinal Center Follicular Th Cells in Simian Immunodeficiency Virus-Infected Neonatal Macaques

Germinal center (GC) CD4⁺ follicular Th (Tfh) cells are critical for cognate B cell help in humoral immune responses to pathogenic infections. Although Tfh cells are expanded or depleted in HIV/SIV-infected adults, the effects of pediatric HIV/SIV infection on Tfh cells remain unclear. In this study, we examined changes in lymphoid follicle formation in lymph nodes focusing on GC Tfh cells, B cell development, and differentiation in SIV-infected neonatal rhesus macaques (Macaca mulatta) compared with age-matched cohorts. Our data showed that follicles and GCs of normal infants rapidly formed in the first few weeks of age, in parallel with increasing GC Tfh cells in various lymphoid tissues. In contrast, GC development and GC Tfh cells were markedly impaired in SIV-infected infants. There was a very low frequency of GC Tfh cells throughout SIV infection in neonates and subsequent infants, accompanied by high viremia, reduction of B cell proliferation/resting memory B cells, and displayed proinflammatory unresponsiveness. These findings indicate neonatal HIV/SIV infection compromises the development of GC Tfh cells, likely contributing to ineffective Ab responses, high viremia, and eventually rapid disease progression to AIDS.

Immune response to a Tdap booster in vertically HIV-infected adolescents

BACKGROUND

Pertussis cases have increased worldwide and knowledge on immune response and cytokine profile after Tdap vaccine in immunodeficient adolescents is scarce.

OBJECTIVE

To evaluate the immune response after Tdap in HIV-infected (HIV) and in healthy adolescents (CONTROL).

METHODOLOGY

Thirty HIV adolescents with CD4 cell counts >200 and 30 CONTROLs were immunized with Tdap, after a prior whole-cell DTP vaccine primary scheme. Blood samples were collected immediately before and after vaccine. Lymphocyte immunophenotyping was performed by flow cytometry; tetanus, diphtheria and pertussis toxin antibodies were assessed by ELISA; whole blood was stimulated with tetanus toxoid and Bordetella pertussis and supernatants were assessed for cytokines by xMAP.

RESULTS

Mean age of HIV and CONTROL groups were 17.9 e 17.1 years, respectively. Pain at injection site was more intense in CONTROL group. HIV group had similar increase in tetanus antibodies at 28 days (geometric mean concentration, GMC, 15.6; 95% CI, 7.52-32.4) than CONTROL group (GMC, 23.1; 95% CI, 15.0-35.5), but lower diphtheria antibodies at 28 days (GMC, 2.3; 95% CI, 0.88-6.19) than CONTROL group (GMC, 16.4; 95% CI, 10.3-26.2); for pertussis, the percentage of individuals who seroconverted was lower in HIV than CONTROL group (HIV, 62.1% versus CONTROL, 100%; p = .002). Both groups built a cellular immune response to tetanus, with a Th2 (IL-4, IL-5 and IL-13) and Th1 (IFN-γ) response, with lower cytokine levels in HIV than in CONTROL group. Especially for pertussis, cellular and humoral responses were less intense in HIV adolescents, with a lower Th1 and Th17 profile and higher IL-10 levels. HIV-infected adolescents on viral suppression showed an enhanced immune response to all the three vaccine antigens, although still at lower levels if compared to CONTROL group.

CONCLUSIONS

Both groups tolerated well and built an immune response after Tdap. However, HIV-infected adolescents would probably benefit from more frequent booster doses.

Perturbation of B Cell Gene Expression Persists in HIV-Infected Children Despite Effective Antiretroviral Therapy and Predicts H1N1 Response

Despite effective antiretroviral therapy (ART), HIV-infected individuals with apparently similar clinical and immunological characteristics can vary in responsiveness to vaccinations. However, molecular mechanisms responsible for such impairment, as well as biomarkers able to predict vaccine responsiveness in HIV-infected children, remain unknown. Following the hypothesis that a B cell qualitative impairment persists in HIV-infected children (HIV) despite effective ART and phenotypic B cell immune reconstitution, the aim of the current study was to investigate B cell gene expression of HIV compared to age-matched healthy controls (HCs) and to determine whether distinct gene expression patterns could predict the ability to respond to influenza vaccine. To do so, we analyzed prevaccination transcriptional levels of a 96-gene panel in equal numbers of sort-purified B cell subsets (SPBS) isolated from peripheral blood mononuclear cells using multiplexed RT-PCR. Immune responses to H1N1 antigen were determined by hemaglutination inhibition and memory B cell ELISpot assays following trivalent-inactivated influenza vaccination (TIV) for all study participants. Although there were no differences in terms of cell frequencies of SPBS between HIV and HC, the groups were distinguishable based upon gene expression analyses. Indeed, a 28-gene signature, characterized by higher expression of genes involved in the inflammatory response and immune activation was observed in activated memory B cells (CD27⁺CD21⁻) from HIV when compared to HC despite long-term viral control (>24 months). Further analysis, taking into account H1N1 responses after TIV in HIV participants, revealed that a 25-gene signature in resting memory (RM) B cells (CD27⁺CD21⁺) was able to distinguish vaccine responders from non-responders (NR). In fact, prevaccination RM B cells of responders showed a higher expression of gene sets involved in B cell adaptive immune responses (APRIL, BTK, BLIMP1) and BCR signaling (MTOR, FYN, CD86) when compared to NR. Overall, these data suggest that a perturbation at a transcriptional level in the B cell compartment persists despite stable virus control achieved through ART in HIV-infected children. Additionally, the present study demonstrates the potential utility of transcriptional evaluation of RM B cells before vaccination for identifying predictive correlates of vaccine responses in this population.

Induction of IL21 in Peripheral T Follicular Helper Cells Is an Indicator of Influenza Vaccine Response in a Previously Vaccinated HIV-Infected Pediatric Cohort

HIV-infected patients of all ages frequently underperform in response to seasonal influenza vaccination, despite virologic control of HIV. The molecular mechanisms governing this impairment, as well as predictive biomarkers for responsiveness, remain unknown. This study was performed in samples obtained prevaccination (T0) from HIV-infected children who received the 2012-2013 seasonal influenza vaccine. Response status was determined based on established criterion for hemagglutination inhibition titer; participants with a hemagglutination titer ≥1:40 plus a ≥4-fold increase over T0 at 3 wk postvaccination were designated as responders. All children had a history of prior influenza vaccinations. At T0, the frequencies of CD4 T cell subsets, including peripheral T follicular helper (pTfh) cells, which provide help to B cells for developing into Ab-secreting cells, were similar between responders and nonresponders. However, in response to in vitro stimulation with influenza A/California/7/2009 (H1N1) Ag, differential gene expression related to pTfh cell function was observed by Fluidigm high-density RT-PCR between responders and nonresponders. In responders, H1N1 stimulation at T0 also resulted in CXCR5 induction (mRNA and protein) in CD4 T cells and IL21 gene induction in pTfh cells that were strongly associated with H1N1-specific B cell responses postvaccination. In contrast, CD4 T cells of nonresponders exhibited increased expression of IL2 and STAT5 genes, which are known to antagonize peripheral Tfh cell function. These results suggest that the quality of pTfh cells at the time of immunization is important for influenza vaccine responses and provide a rationale for targeted, ex vivo Ag-driven molecular profiling of purified immune cells to detect predictive biomarkers of the vaccine response.

Immunisation practices in centres caring for children with perinatally acquired HIV: A call for harmonisation

BACKGROUND

Current national immunisation schedules differ between countries in terms of vaccine formulation, timing of vaccinations and immunisation programme funding and co-ordination. As a result, some HIV infected paediatric population may be left susceptible to vaccine preventable infections. Vaccines used in healthy population should be subjected to high quality ethical research and be explicitly validated for use in children with special vaccination needs such as those infected with HIV. This survey was completed to assess current vaccination practices and attitudes toward vaccination among pediatricians who care for vertically HIV infected children.

METHODS

An online questionnaire was completed by 46 experts in paediatric HIV-infection from the Paediatric European Network for Treatment of AIDS (PENTA). Data were collected between November 2013 and March 2014.

RESULTS

46units looking after 2465 patients completed the questionnaire. The majority of units (67%) reported that common childhood immunisation were administered by the family doctor or local health services rather than in the HIV specialist centre. Vaccination histories were mostly incomplete and difficult to obtain for 40% of the studied population. Concerns were reported regarding the use of live attenuated vaccines, such as varicella and rotavirus, and these were less frequently recommended (61% and 28% of the units respectively). Monitoring of vaccine responses was employed in a minority of centres (41%). A range of different assays were used resulting in diverse units of measurement and proposed correlates of protection.

CONCLUSION

Vaccination practices for perinatally HIV-infected children vary a great deal between countries. Efforts should be made to improve communication and documentation of vaccinations in healthcare settings and to harmonise recommendations relating to additional vaccines for HIV infected children and the use of laboratory assays to guide immunisation. This will ultimately improve coverage and vaccine induced immunity in this vulnerable patient group.

Waning of vaccine-induced immunity to measles in kidney transplanted children

Vaccine-preventable diseases are a significant cause of morbidity and mortality in solid organ transplant recipients who undergo immunosuppression after transplantation. Data on immune responses and long-term maintenance after vaccinations in such population are still limited.We cross-sectionally evaluated the maintenance of immune response to measles vaccine in kidney transplanted children on immunosuppressive therapy. Measles-specific enzyme-linked immunosorbent assay and B-cell enzyme-linked immunosorbent spot were performed in 74 kidney transplant patients (Tps) and in 23 healthy controls (HCs) previously vaccinated and tested for humoral protection against measles. The quality of measles antibody response was measured by avidity test. B-cell phenotype, investigated via flow cytometry, was further correlated to the ability of Tps to maintain protective humoral responses to measles over time.We observed the loss of vaccine-induced immunity against measles in 19% of Tps. Nonseroprotected children showed signs of impaired B-cell distribution as well as immune senescence and lower antibody avidity. We further reported as time elapsed between vaccination and transplantation, as well as the vaccine administration during dialysis are clinical factors affecting the maintenance of the immune memory response against measles.Tps present both quantitative and qualitative alterations in the maintenance of protective immunity to measles vaccine. Prospective studies are needed to optimize the vaccination schedules in kidney transplant recipients in order to increase the immunization coverage over time in this population.

Downfall of the current antibody correlates of influenza vaccine response in yearly vaccinated subjects: Toward qualitative rather than quantitative assays

Response to seasonal influenza vaccination is currently evaluated by antibody correlates that estimate vaccine seroconversion as well as immune protection. These correlates rely on the general dogmas surrounding seasonal influenza vaccination; that is, that vaccine-induced antibodies would exclusively generate immunity to influenza vaccine strains and that protective immunity would wane before the next season. Here, we summarize recently reported data on immunity to seasonal influenza in healthy individuals and rediscuss results on yearly vaccinated pediatric immunocompromised patients that together highlight the need for revision of the current correlates of vaccine response to shift from quantitative to qualitative measurements.

Key differences in B cell activation patterns and immune correlates among treated HIV-infected patients versus healthy controls following influenza vaccination

BACKGROUND

There is increasing recognition of the role of B cell dysfunction in HIV pathogenesis, but little is known about how these perturbations may influence responses to vaccinations.

METHODS

Healthy controls (n=16) and antiretroviral therapy (ART)-treated aviremic HIV-infected subjects (n=26) receiving standard-of-care annual influenza vaccinations were enrolled in the present study. Total bacterial 16S rDNA levels were assessed by quantitative polymerase chain reactions in plasma. Serologic responses were characterized by ELISA, hemagglutination inhibition assay (HI), and microneutralization, and cell-mediated responses were assessed by ELISPOT (antigen-specific IgG+ antibody-secreting cells (ASCs)) and flow cytometry at pre-vaccination (D0), day 7-10 (D7) and day 14-21 (D14) post-vaccination.

RESULTS

Decreased peripheral CD4+ T cell absolute counts and increased frequencies of cycling and apoptotic B cells were found at baseline in HIV-infected subjects relative to healthy controls. In healthy controls, post-vaccination neutralizing activities were related to the frequencies of vaccine-mediated apoptosis and cycling of B cells, but not to CD4+ T cell counts. In patients, both baseline and post-vaccination neutralizing activities were directly correlated with plasma level of bacterial 16S rDNA. However, overall vaccine responses including antibody titers and fold changes were comparable or greater in HIV-infected subjects relative to healthy controls.

CONCLUSION

B cell function correlates with measures of recall humoral immunity in response to seasonal influenza vaccination in healthy controls but not in ART-treated patients.

Immunization of children with secondary immunodeficiency

The main causes of secondary immunodeficiency at a pediatric age include infectious diseases (mainly HIV infection), malignancies, haematopoietic stem cell or solid organ transplantation and autoimmune diseases. Children with secondary immunodeficiency have an increased risk of severe infectious diseases that could be prevented by adequate vaccination coverage, but vaccines administration can be associated with reduced immune response and an increased risk of adverse reactions. The immunogenicity of inactivated and recombinant vaccines is comparable to that of healthy children at the moment of vaccination, but it undergoes a progressive decline over time, and in the absence of a booster, the patients remain at risk of developing vaccine-preventable infections. However, the administration of live attenuated viral vaccines is controversial because of the risk of the activation of vaccine viruses. A specific immunization program should be administered according to the clinical and immunological status of each of these conditions to ensure a sustained immune response without any risks to the patients' health.

The EPIICAL project: an emerging global collaboration to investigate immunotherapeutic strategies in HIV-infected children

The EPIICAL (Early-treated Perinatally HIV-infected Individuals: Improving Children's Actual Life with Novel Immunotherapeutic Strategies) project arises from the firm belief that perinatally infected children treated with suppressive antiretroviral therapy (ART) from early infancy represent the optimal population model in which to study novel immunotherapeutic strategies aimed at achieving ART-free remission. This is because HIV-infected infants treated within 2-3 months of life have a much reduced viral reservoir size, and rarely show HIV-specific immunity but preserve normal immune development. The goal of EPIICAL is the establishment of an international collaboration to develop a predictive platform using this model to select promising HIV therapeutic vaccine candidates, leading to prioritisation or deprioritisation of novel immunotherapeutic strategies. To establish this platform, the EPIICAL Consortium aims to: develop predictive models of virological and immunological dynamics associated with response to early ART and to treatment interruption using available data from existing cohorts/studies of early-treated perinatally HIV-infected children; optimise methodologies to better characterise immunological, virological and genomic correlates/profiles associated with viral control; test novel immunotherapeutic strategies using in vivo proof-of-concept (PoC) studies with the aim of inducing virological, immunological and transcriptomic correlates/profiles equivalent to those defined by the predictive model. This approach will strengthen the capacity for discovery, development and initial testing of new therapeutic vaccine strategies through the integrated efforts of leading international scientific groups, with the aim of improving the health of HIV-infected individuals.

Starting treatment in pediatric HIV infection: try to clarify a gray area

The introduction of combination antiretroviral therapy (ART) in HIV-infected children led to a dramatic reduction in HIV-related morbidity and mortality. The decision about which ART regimen to use on children and when to start the treatment needs to focus on assuring normal growth and neuropsychological development. According to the available treatment guidelines, all infants under 1 year of age with HIV should be started on an ART at diagnosis. It is difficult to balance between the benefits of providing treatment to asymptomatic children >1 year and the concerns about long-term resistance and antiretroviral drug side effects if the treatment is started too early. Current guidelines agree that the need for antiretroviral treatment among asymptomatic children >12 months depends on age-specific CD4+ T-cell count thresholds and viral loads. Recent studies showed that the introduction of combination ART during the first year of life preserves a good function of B-cell and T-cell compartments. Starting treatment earlier might have fundamental roles both in preserving the not yet depleted immune function and in preventing the progressive HIV encephalopathy. The comparison of the international guidelines available for starting HIV treatment in children in developed countries highlights a gray area. New randomized controlled studies are needed to clarify the appropriate approach in asymptomatic children between 2 and 5 years of age.

Seroprevalence and vaccination coverage of vaccine-preventable diseases in perinatally HIV-1-infected patients

BACKGROUND

Even in the era of highly active antiretroviral therapy (HAART), HIV-infected subjects are at higher risk of complications from vaccine-preventable diseases than those uninfected. The current international guidelines strongly recommend that these patients should receive all the routine childhood vaccinations. Although these children represent an appropriate target for immunization, the available data indicate suboptimal coverage rates.

METHODS

To evaluate seroprotection/seropositivity rates and vaccination coverage against the common vaccine-preventable diseases, all patients with vertically transmitted HIV-1 infection who attended San Martino Hospital were enrolled. Blood samples were collected for testing antibodies against diphtheria, tetanus, hepatitis A and B viruses by Enzyme-Linked ImmunoSorbent Assay and polioviruses by microneutralization test. In order to assess immunization coverage, retrospectively was recorded the vaccination history collecting data from Regional Immunization Database.

RESULTS

A total of 39 perinatally HIV-1 infected patients were included in the study. At the time of serum was obtained, the mean age was 18,1 years (range: 6-28). The median CD4+ T-lymphocyte count was 702 cells/mm(3) (2-1476 cells/mm(3)). Twenty-nine (74.4%) patients were found with HIV RNA load < 50 copies/mL. The proportion of subjects with protective anti-tetanus and anti-HBs were 43.6% and 30.8%, respectively. Seroprotection rates about 20% against rubella and measles were found, less than 20% against all the other antigens investigated. In particular, all patients resulted susceptible to mumps. High immunization rates were observed for polio and HBV (100% and 92.3%, respectively) and suboptimal for diphtheria-tetanus (84.6%). For the other recommended vaccines the rates were generally low. None of the patients received varicella vaccine doses.

CONCLUSIONS

As in the HAART era the vertically acquired HIV infection has become a chronic treatable disease, the vaccine-induced long-term protection plays an increasingly significant role; despite good initial response to primary vaccination, subsequent decline and loss of detectable antibodies may be prevented by additional strategies for booster doses of vaccines in adolescents and young adults.

Early highly active antiretroviral therapy enhances B-cell longevity: a 5 year follow up

BACKGROUND

We have previously reported that an early initiation of highly active antiretroviral therapy (HAART) in HIV-1 vertically infected children enhanced the function of memory B-cells gained during childhood routine vaccinations. On the other hand, a significant waning of immunity was observed for patients with a late treatment. In this follow-up study, we report data from a sample of patients in our cohort including late-treated patients being revaccinated with routine childhood vaccines.

METHODS

The levels of serum antibodies and cellular immunity were measured by antigen-specific enzyme-linked immunosorbent assay and B-cell ELISpot. Moreover, flow cytometry on the frequencies of mature-activated (CD10-CD21-) and double-negative (CD27-IgD-) B-cells as hallmarks of immune activation and immune senescence, respectively, was performed for all patients.

RESULTS

Reduced protective humoral immunity and cellular immunity to routine childhood vaccines was observed in late-treated patients. Moreover, we found that timing of HAART related with the frequencies of mature activated and double negative.

CONCLUSIONS

Altogether the data presented in this follow-up study reenforce the importance for an early start of HAART in HIV-1 vertically infected individuals and suggest that timing of HAART is a fundamental factor to take into account for vaccination design in this population.

Premature B-cell senescence as a consequence of chronic immune activation

Similar features between the immune system of healthy elderly people and of younger individuals subjected to conditions of chronic immune activation are progressively being observed. This is raising the hypothesis that chronic immune activation may cause the premature aging of the immune system. Here we dissect this theory by comparing changes occurring to B-cells during healthy aging to the ones occurring during chronic immune activation in younger individuals. Moreover, we discuss how these changes may affect or predict response to vaccination in immune compromised individuals.

Premature ageing of the immune system relates to increased anti-lymphocyte antibodies (ALA) after an immunization in HIV-1-infected and kidney-transplanted patients

Low-affinity immunoglobulin (Ig)G with potential autoreactivity to lymphocytes and hypergammaglobulinaemia have been described previously in HIV-1-infected patients. Whether such antibodies increase after challenging the immune system, for example with an immunization, is not known. In the present study, the modulation of antibodies with low affinity and potential autoreactivity was evaluated after 2012-13 seasonal flu vaccination with a simple empirical laboratory test measuring the titres of anti-lymphocyte antibodies (ALA) in two different models of secondary immunodeficiency: HIV-1 vertically infected patients (HIV) and patients treated with immunosuppressive therapies after kidney transplantation (KT) compared to healthy individuals (HC). In parallel, the activation status of B cells and their degree of immune senescence was evaluated by measuring the B cell interleukin (IL)-21R expression/plasma IL-21 levels and the frequencies of mature-activated (MA) and double-negative (DN) B cells. A significant increase of ALA titres was observed after vaccination in HIV and KT but not in HC, and this correlated directly with the frequencies of both MA and DN and inversely with the B cell IL-21R expression. This suggests that the quality of an immune response triggered by flu vaccination in HIV and KT may depend upon the activation status of B cells and on their degree of immune senescence. Further investigations are needed to verify whether high frequencies of MA and DN may also relate to increase autoimmunity after immunization in high-risk populations.