Immunogenicity following the first and second doses of 7-valent pneumococcal conjugate vaccine in HIV-infected and -uninfected infants

Impaired functionality of antigen presenting cells in HIV- exposed uninfected infants in the first six months of life

HIV-exposed uninfected infants (HEU) have increased morbidity and mortality due to infections in the first 6 months of life that tapers down to 2 years of life. The underlying immunologic defects remain undefined. We investigated antigen-presenting cells (APC) by comparing the phenotype of unstimulated APC, responses to toll-like receptor (TLR) stimulation, and ability to activate natural killer (NK) cells in 24 HEU and 64 HIV-unexposed infants (HUU) at 1-2 days of life (birth) and 28 HEU and 45 HUU at 6 months of life. At birth, unstimulated APC showed higher levels of activation and cytokine production in HEU than HUU and stimulation with TLR agonists revealed lower expression of inflammatory cytokines and activation markers, but similar expression of IL10 regulatory cytokine, in APC from HEU compared to HUU. Differences were still present at 6 months of life. From birth to 6 months, APC underwent extensive phenotypic and functional changes in HUU and minimal changes in HEU. TLR stimulation also generated lower NK cell expression of CD69 and/or IFNγ in HEU compared with HUU at birth and 6 months. In vitro experiments showed that NK IFNγ expression depended on APC cytokine secretion in response to TLR stimulation. Ex vivo IL10 supplementation decreased APC-mediated NK cell activation measured by IFNγ expression. We conclude that APC maturation was stunted or delayed in the first 6 months of life in HEU compared with HUU. Deficient inflammatory APC responses and/or the imbalance between inflammatory and regulatory responses in HEU may play an important role in their increased susceptibility to severe infections.

Kinetics of pneumococcal antibodies among HIV-exposed, uninfected infants in Botswana

BACKGROUND

Streptococcus pneumoniae is a leading cause of severe infections among children. Despite vaccination, HIV-exposed, uninfected (HEU) children have a higher incidence of invasive pneumococcal disease than HIV-unexposed, uninfected (HUU) children. We sought to compare the immunogenicity of 13-valent pneumococcal conjugate vaccine (PCV-13) in HEU and HUU infants.

METHODS

We conducted a prospective cohort study of 134 mother-infant dyads in Botswana. Infants received PCV-13 doses at 2, 3, and 4 months through routine clinical care. We measured IgG antibodies specific to vaccine serotypes in sera collected from infants at 0, 5, and 12 months of age. We calculated the proportion of infants with protective IgG levels (≥0.35 µg/mL) to specific pneumococcal serotypes.

RESULTS

At birth, fewer than half of infants had protective IgG levels to serotypes 1 (38%), 3 (46%), 4 (33%), 5 (23%), 6B (40%), 7F (44%), 9 V (44%), and 23F (46%). Compared to HUU infants (n = 97), HEU infants (n = 37) had lower antibody concentrations at birth to serotypes 5 (p = 0.046) and 19A (p = 0.008) after adjustment for maternal age and infant birth weight. More than 80% of HEU and HUU infants developed protective antibody levels to each of the 13 vaccine serotypes following PCV-13 vaccination. Median concentrations of antibodies to pneumococcal serotypes declined by 55-93% between 5 and 12 months of age, with fewer than half of infants having protective antibody levels to serotypes 1 (47%), 3 (28%), 9 V (44%), 18C (24%), and 23F (49%) at 12 months of age.

CONCLUSIONS

Both HEU and HUU infants developed protective antibody responses to PCV-13 administered in a 3 + 0 schedule. However, antibody concentrations to many pneumococcal serotypes waned substantially by 12 months of age, suggesting that a PCV-13 booster dose in the second year of life may be needed to maintain protective pneumococcal antibody levels in older infants and young children.

Immunization for Children Living With HIV: A Scoping Review

BACKGROUND

Immunosuppression secondary to human immunodeficiency virus (HIV) increases the risk of vaccine-preventable diseases in children living with HIV (CLHIV). Although vaccines are cost-effective interventions, their efficacy, immunogenicity, safety, and persistence of post-vaccination immunity in CLHIV receiving antiretroviral therapy (ART) is unclear. We aimed at identifying existing scientific evidence on immunization of CLHIV generated in the last 10 years to identify the need for a systematic review.

METHODS

Studies were identified using a broad search strategy applied in multiple databases. Included studies involved CLHIV aged 0-10 years and presented outcomes on safety, efficacy, effectiveness, immunogenicity, and use of booster vaccines.

RESULTS

Nineteen publications were identified. There was variable immunogenicity to and efficacy of vaccines by HIV and ART status. All vaccines were safe.

CONCLUSION

The heterogeneity of available studies makes it complex to do a systematic review and meta-analysis. A more uniform approach to sampling and follow-up in future studies would make comparison and interpretation of results more robust.

Immunologic and Virologic Factors Associated With Hospitalization in Human Immunodeficiency Virus-Exposed, Uninfected Infants in the United States

BACKGROUND

Human immunodeficiency virus (HIV)-exposed, uninfected (HEU) infants experience higher rates of morbidity and mortality than HIV-unexposed, uninfected (HUU) infants. Few studies have examined whether particular infections and/or immune responses are associated with hospitalization among HEU infants born in the United States.

METHODS

We evaluated a subset of HEU infants enrolled in the International Maternal Pediatric Adolescent AIDS Clinical Trials Group P1025 and/or Pediatric HIV/AIDS Cohort Study Surveillance Monitoring for ART Toxicities studies. We determined seroconversion to 6 respiratory viruses and measured antibody concentrations to 9 vaccine antigens using quantitative ELISA or electrochemiluminescence. Multivariable modified Poisson regression models were fit to evaluate associations of seroconversion to each respiratory virus/family and antibody concentrations to vaccine antigens with risk of hospitalization in the first year of life. Antibody concentrations to vaccine antigens were compared between HEU infants and HUU infants from a single site using multivariable linear regression models.

RESULTS

Among 556 HEU infants, seroconversion to respiratory syncytial virus (RSV) and parainfluenza was associated with hospitalization (adjusted risk ratio, 1.95 [95% CI, 1.21-3.15] and 2.30 [1.42-3.73], respectively). Antibody concentrations to tetanus toxoid, pertussis, and pneumococcal vaccine antigens were higher among 525 HEU compared with 100 HUU infants. No associations were observed between antibody concentrations with any vaccine and hospitalization among HEU infants.

CONCLUSIONS

RSV and parainfluenza contribute to hospitalization among HEU infants in the first year of life. HEU infants demonstrate robust antibody responses to vaccine antigens; therefore, humoral immune defects likely do not explain the increased susceptibility to infection observed in this population.

The Etiology of Pneumonia in HIV-uninfected South African Children: Findings From the Pneumonia Etiology Research for Child Health (PERCH) Study

BACKGROUND

Pneumonia is the major contributor to under 5 childhood mortality globally. We evaluated the etiology of pneumonia amongst HIV-uninfected South African children enrolled into the Pneumonia Etiology Research for Child Health case-control study.

METHODS

Cases, 1-59 months of age hospitalized with World Health Organization clinically defined severe/very severe pneumonia, were frequency-matched by age and season to community controls. Nasopharyngeal-oropharyngeal swabs were analyzed using polymerase chain reaction for 33 respiratory pathogens, and whole blood was tested for pneumococcal autolysin. Cases were also tested for Mycobacterium tuberculosis. Population etiologic fractions (EF) of pneumonia with radiologic evidence of consolidation/infiltrate were derived for each pathogen through Bayesian analysis.

RESULTS

Of the 805 HIV-uninfected cases enrolled based on clinical criteria, radiologically confirmed pneumonia was evident in 165 HIV-exposed, -uninfected, and 246 HIV-unexposed children. In HIV-exposed and HIV-unexposed children, respiratory syncytial virus was the most important pathogen with EFs of 31.6% [95% credible interval (CrI), 24.8%-38.8%] and 36.4% (95% CrI, 30.5%-43.1%), respectively. M. tuberculosis contributed EFs of 11.6% (95% CrI, 6.1%-18.8%) in HIV-exposed and 8.3% (95% CrI, 4.5%-13.8%) in HIV-unexposed children, including an EF of 16.3% (95% CrI, 6.1%-33.3%) in HIV-exposed children ≥12 months of age. Bacteremia (3.0% vs. 1.6%) and case fatality risk (3.6% vs. 3.7%) were similar in HIV-exposed and HIV-unexposed children.

CONCLUSIONS

Vaccination strategies targeting respiratory syncytial virus should be prioritized for prevention of pneumonia in children. Furthermore, interventions are required to address the high burden of tuberculosis in the pathogenesis of acute community-acquired pneumonia in settings such as ours.

Factors That Influence Infant Immunity and Vaccine Responses

The neonatal period and early infancy are times of increased vulnerability to infection. The immune system of infants undergoes rapid changes and a number of factors can influence the maturation and function of the early infant immune system, amongst these factors are maternal infections and immunity. Infants who are HIV-exposed, but uninfected show important immune alterations, which are likely to be associated with the increased morbidity and mortality observed in these infants. Maternally derived antibodies are crucial in early life to protect infants from infection during the time when their own immune system is becoming more experienced and fully mature. However, maternal antibodies can also interfere with the infant's own antibody responses to primary vaccination. Preterm infants are particularly vulnerable to infection, having not had the opportunity to benefit from the transplacental transfer of maternal antibodies in late pregnancy. In addition, further differences have been observed in the innate and adaptive immune system between preterm and term infants. Here, we focus on maternal influences on the infant immune system, using HIV and maternal vaccination as examples and finish by considering how prematurity impacts infant immune responses to vaccination.

Immunogenicity and safety of a hexavalent pediatric vaccine in HIV-exposed infected and uninfected infants in Republic of South Africa

Human immunodeficiency virus (HIV)-exposed infants may be at increased risk of vaccine-preventable disease. This study was conducted as a post-licensure commitment in this population to evaluate the primary series, antibody persistence, and booster response to a licensed fully liquid hexavalent vaccine containing diphtheria (D), tetanus (T), acellular pertussis (aP), inactivated poliovirus (IPV), hepatitis B (HB), and Haemophilus influenzae type b antigens (PRP~T). This was a Phase III, open-label, randomized study conducted at a single center in the Republic of South Africa. The DTaP-IPV-HB-PRP~T vaccine was administered to HIV-exposed infected (Group A: N = 14) and HIV-exposed uninfected (Group B: N = 50) infants as a 6, 10, 14 week primary series with a toddler booster at 15–18 months of age. Immunogenicity of each antigen was measured using validated assays and vaccine reactogenicity was recorded using diary cards. The low number of HIV-exposed infected participants, due to widespread pre- and peri-natal retroviral treatment, meant that between-group comparisons should be treated with caution. In each group, primary series and booster immune seroprotection rates were strong, and pre-booster antibody persistence was good, although anti-HBs ≥10 mIU/mL in Group A was 78.6% post-primary series, 58.3% pre-booster, and 75.0% post-booster. There were no safety concerns. In conclusion, primary series and booster vaccination of the DTaP-IPV-HB-PRP~T vaccine were immunogenic and safe in HIV-exposed infected and uninfected infants. These results were comparable to historical data in healthy infants and toddlers.

Exposure to lead and vaccine-specific IgG titers in South African children participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE): A longitudinal study

BACKGROUND

While successes have been achieved in reducing global exposure to lead, few studies have investigated the potential health effects of low-level exposure (e.g. blood lead levels [BLLs] below the CDC reference level of 5 μg/dL), particularly among children from low- and middle-income countries. In addition, lead is immunotoxic in animals but human data on immune response to vaccines is limited. Our aim was to determine whether low-level exposure to lead is associated with humoral response to vaccines among rural South African children.

METHODS

We used data from the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE), a birth cohort study conducted in Limpopo, South Africa. BLLs were measured in whole blood collected at age 1 year and IgG titers for measles, tetanus and Haemophilus influenzae type B (Hib) were determined at age 3.5 years among 425 fully-vaccinated children.

RESULTS

BLLs were low (median = 1.90 μg/dL) and 94% of children had a BLL below 5 μg/dL. Overall, BLLs were associated with higher risks of having IgG titers below the protective limit for tetanus (RR = 1.88 per 10-fold increase; 95%CI = 1.08, 3.24) but not measles (RR = 1.02; 95%CI = 0.26, 3.95) or Hib (RR = 0.96; 95%CI = 0.54, 1.71). BLLs were also associated with low Hib IgG titers among children exposed to HIV in utero and with low measles IgG titers among females. In contrast, the association with measles IgG titers was positive among males.

CONCLUSION

Low-level exposure to lead may compromise the humoral response to vaccines. Children exposed to HIV in utero and females may be particularly susceptible.

Evaluation of the impact of HIV-1 infection and density of common nasopharyngeal bacterial colonizers in South African children immunized with 7-valent pneumococcal conjugate vaccine

BACKGROUND

Due to limitations in standard culture methods, the impact of pneumococcal conjugate vaccine (PCV) immunization on nasopharyngeal bacterial carriage density is unclear, including among HIV-infected children.

METHODS

The prevalence and density of serotype/serogroup-specific pneumococcal and other nasopharyngeal colonizing bacteria were investigated in archived swabs of HIV-infected and HIV-uninfected, PCV-7 immunized (at 6, 10 and 14 weeks of age) South African children collected at 9 and 16 months of age. During the course of the study, PCV-immunization of children in Soweto was limited to study-participants, as the vaccine had not been introduced into the public immunization program.

RESULTS

At 9 months of age, the prevalence of overall pneumococcal colonization was lower in HIV-infected (58.6%) than HIV-uninfected children (69.9%, p = 0.02), mainly due to lower prevalence of non-vaccine-serotype colonization (27.8% vs. 40%, respectively; p = 0.047). The mean-log₁₀ density of pneumococcal colonization was, however, higher in HIV-infected (4.81 CFU/ml) than HIV-uninfected pneumococcal colonized children (4.44 CFU/ml; p = 0.014); mainly due to higher mean-log₁₀ density of PCV7-serotype colonization (4.21 vs. 3.72 CFU/ml; p = 0.014). No difference in the prevalence or density of overall pneumococci was found at 16 months of age. The prevalence of non-vaccine serotype colonization remained 1.7 fold higher in HIV-uninfected (60.4%) than HIV-infected children (50.9%, p = 0.049). Other differences included a lower prevalence of H. influenzae colonization in HIV-infected (42.3% and 56%) than HIV-uninfected children (64.2% and 73.4%) at both 9 and 16 months of age respectively; however, the density of colonization was similar.

CONCLUSION

Increased carriage density of residual PCV7-serotypes might cause HIV-infected children to have a higher risk of pneumococcal disease. The higher carriage density observed in HIV-infected children could be attributed to a combination of factors, including HIV treatment and impaired host immunity. Additional studies are needed.

Extended Prophylaxis With Nevirapine Does Not Affect Growth in HIV-Exposed Infants

BACKGROUND

Effects of prolonged nevirapine prophylaxis exposure on growth among HIV-exposed uninfected (HEU) infants are unknown. This study examines the impact of extended nevirapine prophylaxis from 6 weeks to 6 months on the growth of HEU infants followed for 18 months and also identifies correlates of incident wasting, stunting, underweight, and low head circumference in the HPTN 046 trial.

METHODS

Intention-to-treat analysis examined the effect of extended nevirapine exposure on: weight-for-age Z-score, length-for-age Z-score, weight-for-length Z-score, and head circumference-for-age Z-score. Multivariable linear mixed-effects and Cox proportional hazard models were used to compare growth outcomes between the study arms and identify correlates of incident adverse growth outcomes, respectively.

RESULTS

Compared to placebo, extended prophylactic nevirapine given daily from 6 weeks to 6 months did not affect growth in HEU breastfeeding (BF) infants over time (treatment × time: P > 0.05). However, overall growth declined over time (time effect: P < 0.01) when compared with WHO general population norms. Male sex was associated with higher risk of all adverse growth outcomes (P < 0.05), whereas short BF duration was associated with wasting (P = 0.03). Maternal antiretroviral therapy exposure was protective against underweight (P = 0.02). Zimbabwe tended to have worse growth outcomes especially stunting, compared to South Africa, Uganda and Tanzania (P < 0.05).

CONCLUSIONS

It is reassuring that prolonged exposure to nevirapine for prevention-of-mother-to-child HIV transmission does not restrict growth. However, targeted interventions are needed to improve growth outcomes among at-risk HEU infants (i.e., male sex, short BF duration, lack of maternal antiretroviral therapy exposure, and resident in Zimbabwe).

Performance of the Biomark HD real-time qPCR System (Fluidigm) for the detection of nasopharyngeal bacterial pathogens and Streptococcus pneumoniae typing

Traditional qPCR assays for pneumococcal detection and serotype characterization require large sample volume, is expensive and labor intensive. We aimed to develop a quantitative nanofluidic Fluidigm assay to overcome some of these shortcomings. A quantitative Fluidigm assay was established to detect 11 bacterial pathogens, 55 pneumococcal serotypes and 6 serotypes of H. influenzae. The Fluidigm assay results were compared to conventional qPCR and culture. All reactions in the Fluidigm assay effectively amplified their respective targets with high sensitivity and specificity compared to qPCR. There was excellent concordance between qPCR and Fluidigm for detection of carriage prevalence (kappa > 0.75) and density (Rho > 0.95). Fluidigm identified an additional 7 (4.2%) serotypes over those detected by qPCR. There was a modest concordance between culture and Fluidigm for the majority of reactions detecting S. pneumoniae serotypes/serogroups (kappa > 0.6), with Fluidigm identifying an additional 113 (39.1%) serotypes. Discordant results between the three methods were associated with a low carriage density. The Fluidigm assay was able to detect common pneumococcal serotypes, H. influenzae serotypes, and other common nasopharyngeal bacterial organisms simultaneously. Deployment of this assay in epidemiological studies could provide better insight into the effect of PCV immunization on the nasopharyngeal microbiota in the community.

HIV, Cytomegalovirus, and Malaria Infections during Pregnancy Lead to Inflammation and Shifts in Memory B Cell Subsets in Kenyan Neonates

Infections during pregnancy can expose the fetus to microbial Ags, leading to inflammation that affects B cell development. Prenatal fetal immune priming may have an important role in infant acquisition of pathogen-specific immunity. We examined plasma proinflammatory biomarkers, the proportions of various B cell subsets, and fetal priming to tetanus vaccination in cord blood from human United States and Kenyan neonates. United States neonates had no identified prenatal infectious exposures, whereas Kenyan neonates examined had congenital CMV or mothers with prenatal HIV or Plasmodium falciparum or no identified infectious exposures. Kenyan neonates had higher levels of IP-10, TNF-α, CRP, sCD14, and BAFF than United States neonates. Among the Kenyan groups, neonates with prenatal infections/infectious exposures had higher levels of cord blood IFN-γ, IL-7, sTNFR1, and sTNFR2 compared with neonates with no infectious exposures. Kenyan neonates had greater proportions of activated memory B cells (MBC) compared with United States neonates. Among the Kenyan groups, HIV-exposed neonates had greater proportions of atypical MBC compared with the other groups. Although HIV-exposed neonates had altered MBC subset distributions, detection of tetanus-specific MBC from cord blood, indicative of fetal priming with tetanus vaccine given to pregnant women, was comparable in HIV-exposed and non-HIV-exposed neonates. These results indicate that the presence of infections during pregnancy induces fetal immune activation with inflammation and increased activated MBC frequencies in neonates. The immunologic significance and long-term health consequences of these differences warrant further investigation.

Outpacing the pneumococcus: Antibody dynamics in the first few days following pneumococcal capsular antigen stimulation

Children in developing countries are frequently exposed to the pneumococcus, but few develop invasive pneumococcal disease (IPD). We test the hypothesis that natural variation exists in the rapidity of IgG responses following exposure to pneumococcal polysaccharides, and that these differences are sufficiently great to affect susceptibility to and outcome of IPD. We recruited children aged 24–36 months, who had recovered from IPD, and age-matched healthy controls and vaccinated them with 1 dose of the 23-valent PPV to mimic natural exposure. We collected serum samples after vaccination and analysed the dynamics of anti-polysaccharide antibody responses to several capsular antigens. Mean IgG response times to different serotypes were 6.4–7.3 days, with standard deviations of 0.9–1.85 days, suggesting a natural range in response times of up to 7 days. Serotype 1 elicited the largest fold-rise, serotype 23F the smallest. The proportion of responses achieved by day 7 was similar in children with a history of IPD and healthy children. There was considerable natural variation in the rapidity of anti-capsular IgG responses extending over 4–7 days. There was no evidence to suggest that children who have experienced IPD respond more slowly to heterologous pneumococcal capsular antigens than do healthy children.

The Effect of Human Immunodeficiency Virus and Cytomegalovirus Infection on Infant Responses to Vaccines: A Review

The success of prevention of mother to child transmission programs over the last two decades has led to an increasing number of infants who are exposed to human immunodeficiency virus (HIV), but who are not themselves infected (HIV-exposed, uninfected infants). Although the morbidity and mortality among HIV-exposed, uninfected infants is considerably lower than that among HIV-infected infants, they may remain at increased risk of infections in the first 2 years of life compared with their HIV-unexposed peers, especially in the absence of breastfeeding. There is some evidence of immunological differences in HIV-exposed, uninfected infants, which could play a role in susceptibility to infection. Cytomegalovirus (CMV) may contribute to the increased immune activation observed in HIV-exposed, uninfected infants. Infants born to HIV-infected women are at increased risk of congenital CMV infection, as well as early acquisition of postnatal CMV infection. In infants with HIV infection, CMV co-infection in early life is associated with higher morbidity and mortality. This review considers how HIV infection, HIV exposure, and CMV infection affect infant responses to vaccination, and explores possible immunological and other explanations for these findings. HIV-infected infants have lower vaccine-induced antibody concentrations following tetanus, diphtheria, pertussis, hepatitis B, and pneumococcal vaccination, although the clinical relevance of this difference is not known. Despite lower concentrations of maternal-specific antibody at birth, HIV-exposed, uninfected infants respond to vaccination at least as well as their HIV-unexposed uninfected peers. CMV infection leads to an increase in activation and differentiation of the whole T-cell population, but there is limited data on the effects of CMV infection on infant vaccine responses. In light of growing evidence of poor clinical outcomes associated with CMV infection in HIV-exposed, uninfected infants, further studies are particularly important in this group. A clearer understanding of the mechanisms by which maternal viral infections influence the developing infant immune system is critical to the success of maternal and infant vaccination strategies.

Immune responses to oral poliovirus vaccine in HIV-exposed uninfected Zimbabwean infants

It remains uncertain whether HIV-exposed uninfected (HEU) infants have impaired responses to oral vaccines. We performed a cross-sectional study of 6-month-old infants recruited at birth to the ZVITAMBO trial in Zimbabwe between 1997–2001, before introduction of prevention of mother-to-child transmission interventions. We measured poliovirus-specific IgA to type 1–3 polio strains by semi-quantitative capture ELISA in cryopreserved serum samples collected from 85 HEU and 101 HIV-unexposed infants at 6 months of age, one month after their last immunisation with trivalent OPV. Almost all infants were breastfed, with the majority in both groups mixed breastfed (70.6% HEU versus 71.3% HIV-unexposed). Median (IQR) vaccine titers for HEU and HIV-unexposed infants were 1592 (618–4896) vs. 1774 (711–5431) for Sabin 1 (P = 0.46); 1895 (810–4398) vs. 2308 (1081–4283) for Sabin 2 (P = 0.52); and 1798 (774–4192) vs. 2260 (996–5723) for Sabin 3 (P = 0.18). There were no significant differences in vaccine titers between HEU and HIV-unexposed infants, suggesting that vertical HIV exposure does not impact oral poliovirus vaccine immunogenicity.

Pneumococcal conjugate vaccine in HIV-infected and HIV-exposed, uninfected children

INTRODUCTION

Incidence of invasive pneumococcal disease (IPD) among HIV-infected children is 20-40 fold greater compared to HIV-uninfected children, including among HIV-infected children on antiretroviral therapy (ART). Also, HIV-exposed, uninfected children have 2.7-fold greater risk of IPD compared to HIV-unexposed children. Areas covered: We reviewed studies identified on Pubmed database with the terms 'PCV' and 'HIV'; studies involving adults only were excluded. Expert commentary: While ART and pneumococcal conjugate vaccines (PCV) have reduced IPD morbidity and mortality in HIV-infected children, ART-naïve and immunosuppressed children have inferior immunogenicity to most PCV serotypes; highlighting the need for concomitant use of ART with PCV. Furthermore, studies to determine optimal PCV dosing schedules, timing and number of doses, are urgently required to ensure sustained vaccine efficacy in HIV-infected children.

Vaccination with 10-valent pneumococcal conjugate vaccine in infants according to HIV status

BACKGROUND

Phase III, open-label, single-center, controlled study in South Africa (ClinicalTrials.gov: NCT00829010) to evaluate immunogenicity, reactogenicity, and safety of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in human immunodeficiency virus (HIV)-infected (HIV+), HIV-exposed-uninfected (HEU), and HIV-unexposed-uninfected (HUU) children.

METHODS

Children stratified by HIV status received PHiD-CV primary vaccination (age 6/10/14 weeks; coadministered with routine childhood vaccines) and booster dose (age 9-10 months). Immune responses, assessed using enzyme-linked immunosorbent and functional assays, and safety were evaluated up to 14 months post-booster.

RESULTS

Of 83, 101, and 100 children enrolled in HIV+, HEU, and HUU groups, 70, 91, and 93 were included in according-to-protocol immunogenicity cohort. For each vaccine-serotype, percentages of children with antibody concentrations ≥0.2 μg/mL were ≥97% 1 month post-primary vaccination and ≥98.5% 1 month post-booster (except for 6B and 23F at both timepoints). Post-primary vaccination, functional antibody responses were lower in HIV+ children: for each vaccine-serotype, percentages of children with opsonophagocytic activity (OPA) titres ≥8 were ≥72%, ≥81%, and ≥79% for HIV+, HEU, and HUU children. Post-booster, ≥87% of children in each group had OPA titres ≥8. Reactogenicity was similar across groups. Thirty one (37%) HIV+, 25 (25%) HEU, and 20 (20%) HUU children reported ≥1 serious adverse event. Five HIV+ and 4 HEU children died. One death (sudden infant death syndrome; HEU group; 3 days post-dose 1) was considered potentially vaccine-related.

CONCLUSION

PHiD-CV was immunogenic and well-tolerated in HIV+, HEU, and HUU children, and has the potential to provide substantial benefit irrespective of HIV infection status.

The potential impact of pneumococcal conjugate vaccine in Africa: Considerations and early lessons learned from the South African experience

The introduction of pneumococcal conjugate vaccine (PCV) into the South African public immunization program since 2009 adopted a novel vaccination schedule of 3 doses at 6, 14 and 40 weeks of age. Over the past 5 y it has been shown that infant PCV immunization in South Africa is effective in reducing the burden of invasive pneumococcal disease (IPD) among HIV-infected and HIV-uninfected children. Furthermore, indirect protection of unvaccinated age-groups (including high risk groups such as HIV-infected adults) against IPD was demonstrated despite the absence of any substantial catch-up campaign of older children. This indirect effect against IPD is corroborated by the temporal reduction in vaccine-serotype colonization among age-groups targeted for PCV immunization as well as unvaccinated HIV-infected and HIV-uninfected adults, which was evident within 2 y of PCV introduction into the immunization program. Vaccine effectiveness has also been demonstrated in children against presumed bacterial pneumonia. The evaluation of the impact of PCV in South Africa, however, remains incomplete. The knowledge gaps remaining include the evaluation of PCV on the incidence of all-cause pneumonia hospitalization among vaccinated and unvaccinated age-groups. Furthermore, ongoing surveillance is required to determine whether there is ongoing replacement disease by non-vaccine serotypes, which could offset the early gains associated with the immunization program in the country.

Increased Risk of Group B Streptococcus Invasive Infection in HIV-Exposed but Uninfected Infants: A Review of the Evidence and Possible Mechanisms

Group B Streptococcus (GBS) is a major cause of neonatal sepsis and mortality worldwide. Studies from both developed and developing countries have shown that HIV-exposed but uninfected (HEU) infants are at increased risk of infectious morbidity, as compared to HIV-unexposed uninfected infants (HUU). A higher susceptibility to GBS infections has been reported in HEU infants, particularly late-onset diseases and more severe manifestations of GBS diseases. We review here the possible explanations for increased susceptibility to GBS infection. Maternal GBS colonization during pregnancy is a major risk factor for early-onset GBS invasive disease, but colonization rates are not higher in HIV-infected compared to HIV-uninfected pregnant women, while selective colonization with more virulent strains in HIV-infected women is suggested in some studies. Lower serotype-specific GBS maternal antibody transfer and quantitative and qualitative defects of innate immune responses in HEU infants may play a role in the increased risk of GBS invasive disease. The impact of maternal antiretroviral treatment and its consequences on immune activation in HEU newborns are important to study. Maternal immunization presents a promising intervention to reduce GBS burden in the growing HEU population.

The Immune System of HIV-Exposed Uninfected Infants

Infants born to human immunodeficiency virus (HIV) infected women are HIV-exposed but the majority remains uninfected [i.e., HIV-exposed uninfected (HEU)]. HEU infants suffer greater morbidity and mortality from infections compared to HIV-unexposed (HU) peers. The reason(s) for these worse outcomes are uncertain, but could be related to an altered immune system state. This review comprehensively summarizes the current literature investigating the adaptive and innate immune system of HEU infants. HEU infants have altered cell-mediated immunity, including impaired T-cell maturation with documented hypo- as well as hyper-responsiveness to T-cell activation. And although prevaccination vaccine-specific antibody levels are often lower in HEU than HU, most HEU infants mount adequate humoral immune response following primary vaccination with diphtheria toxoid, haemophilus influenzae type b, whole cell pertussis, measles, hepatitis B, tetanus toxoid, and pneumococcal conjugate vaccines. However, HEU infants are often found to have lower absolute neutrophil counts as compared to HU infants. On the other hand, an increase of innate immune cytokine production and expression of co-stimulatory markers has been noted in HEU infants, but this increase appears to be restricted to the first few weeks of life. The immune system of HEU children beyond infancy remains largely unexplored.

HIV-Exposed Uninfected Infants in Zimbabwe: Insights into Health Outcomes in the Pre-Antiretroviral Therapy Era

The ZVITAMBO trial recruited 14,110 mother-infant pairs to a randomized controlled trial of vitamin A between 1997 and 2000, before the availability of antiretroviral therapy for HIV prophylaxis or treatment in Zimbabwe. The HIV status of mothers and infants was well characterized through 1-2 years of follow-up, leading to the largest cohort to date of HIV-exposed uninfected (HEU) infants (n = 3135), with a suitable comparison group of HIV-unexposed infants (n = 9510). Here, we draw on 10 years of published findings from the ZVITAMBO trial. HEU infants had increased morbidity compared to HIV-unexposed infants, with 50% more hospitalizations in the neonatal period and 30% more sick clinic visits during infancy, particularly for skin infections, lower respiratory tract infections, and oral thrush. HEU children had 3.9-fold and 2.0-fold higher mortality than HIV-unexposed children during the first and second years of life, respectively, most commonly due to acute respiratory infections, diarrhea/dysentery, malnutrition, sepsis, and meningitis. Infant morbidity and mortality were strongly related to maternal HIV disease severity, and increased morbidity remained until maternal CD4 counts were >800 cells/μL. HEU infants were more likely to be premature and small-for-gestational age than HIV-unexposed infants, and had more postnatal growth failure. Here, we propose a conceptual framework to explain the increased risk of infectious morbidity, mortality, and growth failure among HEU infants, hypothesizing that immune activation and inflammation are key drivers of both infection susceptibility and growth failure. Future studies should further dissect the causes of infection susceptibility and growth failure and determine the impact of ART and cotrimoxazole on outcomes of this vulnerable group of infants in the current era.

HIV-exposed, uninfected infants: new global challenges in the era of paediatric HIV elimination

The number of infants infected with HIV is declining with the rise in interventions for the elimination of paediatric HIV infection, but the number of uninfected infants exposed to HIV through their HIV-infected mothers is increasing. Interest in the health outcomes of HIV-exposed, uninfected infants has grown in the past decade, with several studies suggesting that these infants have increased mortality rates, increased infectious morbidity, and impaired growth compared with HIV-unexposed infants. However, heterogeneous results might reflect the inherent challenges in studies of HIV-exposed, uninfected infants, which need large populations with appropriate, contemporaneous comparison groups and repeated HIV testing throughout the period of breastfeeding. We review the effects of HIV exposure on mortality, morbidity, and growth, discuss the immunological abnormalities identified so far, and provide an overview of interventions that could be effective in this susceptible population. As the number of infants infected with HIV declines, the health needs of HIV-exposed, uninfected infants should be prioritised further, to ensure that post-2015 Sustainable Development Goals are achieved.

The PneuCarriage Project: A Multi-Centre Comparative Study to Identify the Best Serotyping Methods for Examining Pneumococcal Carriage in Vaccine Evaluation Studies

BACKGROUND

The pneumococcus is a diverse pathogen whose primary niche is the nasopharynx. Over 90 different serotypes exist, and nasopharyngeal carriage of multiple serotypes is common. Understanding pneumococcal carriage is essential for evaluating the impact of pneumococcal vaccines. Traditional serotyping methods are cumbersome and insufficient for detecting multiple serotype carriage, and there are few data comparing the new methods that have been developed over the past decade. We established the PneuCarriage project, a large, international multi-centre study dedicated to the identification of the best pneumococcal serotyping methods for carriage studies.

METHODS AND FINDINGS

Reference sample sets were distributed to 15 research groups for blinded testing. Twenty pneumococcal serotyping methods were used to test 81 laboratory-prepared (spiked) samples. The five top-performing methods were used to test 260 nasopharyngeal (field) samples collected from children in six high-burden countries. Sensitivity and positive predictive value (PPV) were determined for the test methods and the reference method (traditional serotyping of >100 colonies from each sample). For the alternate serotyping methods, the overall sensitivity ranged from 1% to 99% (reference method 98%), and PPV from 8% to 100% (reference method 100%), when testing the spiked samples. Fifteen methods had ≥70% sensitivity to detect the dominant (major) serotype, whilst only eight methods had ≥70% sensitivity to detect minor serotypes. For the field samples, the overall sensitivity ranged from 74.2% to 95.8% (reference method 93.8%), and PPV from 82.2% to 96.4% (reference method 99.6%). The microarray had the highest sensitivity (95.8%) and high PPV (93.7%). The major limitation of this study is that not all of the available alternative serotyping methods were included.

CONCLUSIONS

Most methods were able to detect the dominant serotype in a sample, but many performed poorly in detecting the minor serotype populations. Microarray with a culture amplification step was the top-performing method. Results from this comprehensive evaluation will inform future vaccine evaluation and impact studies, particularly in low-income settings, where pneumococcal disease burden remains high.

Longitudinal study on Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus nasopharyngeal colonization in HIV-infected and -uninfected infants vaccinated with pneumococcal conjugate vaccine

BACKGROUND

Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus are all potentially pathogenic, which frequently colonize the nasopharynx (NP) prior to causing disease. We studied bacterial NP-colonization in 321 HIV-infected and 243 HIV-uninfected children vaccinated with 7-valent pneumococcal conjugate vaccine (PCV7) at 6, 10 and 14 weeks of age.

METHODS

HIV-uninfected infants included those born to HIV-uninfected (HUU) and HIV-infected women (HEU); HIV-infected children with CD4+ lymphocyte ≥25% were randomized to initiate antiretroviral therapy immediately (ART-Immed) or when clinically indicated (ART-Def). Nasopharyngeal swabs for bacterial culture were taken prior to each PCV7 dose (Visits 1-3) and at 20, 39, 47 and 67 weeks of age (Visits 4-7). Swabs were cultured by standard methods and pneumococcal serotyping done by the Quellung method.

RESULTS

Colonization patterns for pneumococcus, H. influenzae and S. aureus did not differ between HUU and HEU children; and were also generally similar between ART-Def and ART-Immed children. Prevalence of PCV7-serotype colonization was similar between HIV-infected and HIV-uninfected children, however, overall pneumococcal and specifically non-vaccine serotype colonization tended to be lower in HIV-infected children. HIV-infected children also had a 44% lower prevalence of S. aureus colonization at Visit-1 (p=0.010); and H. influenzae colonization was also lower among HIV-infected than HIV-uninfected children at Visit-2, Visit-3, Visit-6 and Visit-7.

CONCLUSION

Vaccine-serotype colonization is similar in PCV-immunized HIV-infected and HIV-uninfected children. We, however, identified a lower prevalence of overall-pneumococcal and H. influenzae colonization in HIV-infected children post-PCV vaccination, the clinical-relevance of which warrants further study.

Increased risk for and mortality from invasive pneumococcal disease in HIV-exposed but uninfected infants aged <1 year in South Africa, 2009-2013

BACKGROUND

High antenatal human immunodeficiency virus (HIV) seroprevalence rates (∼ 30%) with low perinatal HIV transmission rates (2.5%), due to HIV prevention of mother-to-child transmission program improvements in South Africa, has resulted in increasing numbers of HIV-exposed but uninfected (HEU) children. We aimed to describe the epidemiology of invasive pneumococcal disease (IPD) in HEU infants.

METHODS

We conducted a cross-sectional study of infants aged <1 year with IPD enrolled in a national, laboratory-based surveillance program for incidence estimations. Incidence was reported for 2 time points, 2009 and 2013. At enhanced sites we collected additional data including HIV status and in-hospital outcome.

RESULTS

We identified 2099 IPD cases in infants from 2009 to 2013 from all sites. In infants from enhanced sites (n = 1015), 92% had known HIV exposure status and 86% had known outcomes. IPD incidence was highest in HIV-infected infants, ranging from 272 to 654 per 100,000 population between time points (2013 and 2009), followed by HEU (33-88 per 100,000) and HIV-unexposed and uninfected (HUU) infants (18-28 per 100,000). The case-fatality rate in HEU infants (29% [74/253]) was intermediate between HUU (25% [94/377]) and HIV-infected infants (34% [81/242]). When restricted to infants <6 months of age, HEU infants (37% [59/175]) were at significantly higher risk of dying than HUU infants (32% [51/228]; adjusted relative risk ratio, 1.76 [95% confidence interval, 1.09-2.85]).

DISCUSSION

HEU infants are at increased risk of IPD and mortality from IPD compared with HUU children, especially as young infants. HEU infants, whose numbers will likely continue to increase, should be prioritized for interventions such as pneumococcal vaccination along with HIV-infected infants and children.

Effectiveness of 7-valent pneumococcal conjugate vaccine against invasive pneumococcal disease in HIV-infected and -uninfected children in south africa: a matched case-control study

A 2 + 1 seven-valent pneumococcal conjugate vaccine schedule is effective against vaccine-serotype invasive pneumococcal disease (IPD) in HIV-uninfected children and HIV-exposed but -uninfected children and against all-serotype multidrug-resistant IPD in HIV-uninfected children.

Background. South Africa introduced 7-valent pneumococcal conjugate vaccine (PCV7) in April 2009 using a 2 + 1 schedule (6 and 14 weeks and 9 months). We estimated the effectiveness of ≥2 PCV7 doses against invasive pneumococcal disease (IPD) in human immunodeficiency virus (HIV)–infected and -uninfected children.

Methods. IPD (pneumococcus identified from a normally sterile site) cases were identified through national laboratory-based surveillance. Specimens were serotyped by Quellung or polymerase chain reaction. Four controls, matched for age, HIV status, and hospital were sought for each case. Using conditional logistic regression, we calculated vaccine effectiveness (VE) as 1 minus the adjusted odds ratio for vaccination.

Results. From March 2010 through November 2012, we enrolled 187 HIV-uninfected (48 [26%] vaccine serotype) and 109 HIV-infected (43 [39%] vaccine serotype) cases and 752 HIV-uninfected and 347 HIV-infected controls aged ≥16 weeks. Effectiveness of ≥2 PCV7 doses against vaccine-serotype IPD was 74% (95% confidence interval [CI], 25%–91%) among HIV-uninfected and −12% (95% CI, −449% to 77%) among HIV-infected children. Effectiveness of ≥3 doses against vaccine-serotype IPD was 90% (95% CI, 14%–99%) among HIV-uninfected and 57% (95% CI, −371% to 96%) among HIV-infected children. Among HIV-exposed but -uninfected children, effectiveness of ≥2 doses was 92% (95% CI, 47%–99%) against vaccine-serotype IPD. Effectiveness of ≥2 doses against all-serotype multidrug-resistant IPD was 96% (95% CI, 62%–100%) among HIV-uninfected children.

Conclusions. A 2 + 1 PCV7 schedule was effective in preventing vaccine-serotype IPD in HIV-uninfected and HIV-exposed, uninfected children. This finding supports the World Health Organization recommendation for this schedule as an alternative to a 3-dose primary series among HIV-uninfected individuals.

Immunogenicity of seven-valent pneumococcal conjugate vaccine administered at 6, 14 and 40 weeks of age in South African infants

Background

The high cost of pneumococcal conjugate vaccine (PCV) and local epidemiological factors contributed to evaluating different PCV dosing-schedules. This study evaluated the immunogenicity of seven-valent PCV (PCV7) administered at 6-weeks; 14-weeks and 9-months of age.

Methods

250 healthy, HIV-unexposed infants were immunized with PCV7 concurrently with other childhood vaccines. Serotype-specific anti-capsular IgG concentrations were measured one-month following the 1^st and 2^nd PCV-doses, prior to and two-weeks following the 3^rd dose. Opsonophagocytic killing assay (OPA) was measured for three serotypes following the 2^nd and 3^rd PCV7-doses. Immunogenicity of the current schedule was compared to a historical cohort of infants who received PCV7 at 6, 10 and 14 weeks of age.

Results

The proportion of infants with serotype-specific antibody ≥0.35 µg/ml following the 2^nd PCV7-dose ranged from 84% for 6B to ≥89% for other serotypes. Robust antibody responses were observed following the 3^rd dose. The proportion of children with OPA ≥8 for serotypes 9V, 19F and 23F increased significantly following the 3^rd PCV7-dose to 93.6%; 86.0% and 89.7% respectively. The quantitative antibody concentrations following the 2^nd PCV7-dose were comparable to that after the 3^rd -dose in the 6-10-14 week schedule. Geometric mean concentrations (GMCs) following the 3^rd PCV7-dose were higher for all serotypes in this study compared to the historical cohort.

Conclusions

The studied PCV7 dosing schedule induced good immune responses, including higher GMCs following the 3^rd-dose at 9-months compared to when given at 14-weeks of age. This may confer longer persistence of antibodies and duration of protection against pneumococcal disease.