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.

Non-diphtheriae Corynebacterium species are associated with decreased risk of pneumococcal colonization during infancy

Streptococcus pneumoniae (pneumococcus) is a leading cause of severe infections among children and adults. Interactions between commensal microbes in the upper respiratory tract and S. pneumoniae are poorly described. In this study, we sought to identify interspecies interactions that modify the risk of S. pneumoniae colonization during infancy and to describe development of the upper respiratory microbiome during infancy in a sub-Saharan African setting. We collected nasopharyngeal swabs monthly (0-6 months of age) or bimonthly (6-12 months of age) from 179 mother-infant dyads in Botswana. We used 16S ribosomal RNA gene sequencing to characterize the nasopharyngeal microbiome and identified S. pneumoniae colonization using a species-specific PCR assay. We detect S. pneumoniae colonization in 144 (80%) infants at a median age of 71 days and identify a strong negative association between the relative abundance of the bacterial genera Corynebacterium within the infant nasopharyngeal microbiome and the risk of S. pneumoniae colonization. Using in vitro cultivation experiments, we demonstrate growth inhibition of S. pneumoniae by secreted factors from strains of several Corynebacterium species isolated from these infants. Finally, we demonstrate that antibiotic exposures and the winter season are associated with a decline in the relative abundance of Corynebacterium within the nasopharyngeal microbiome, while breastfeeding is associated with an increase in the Corynebacterium relative abundance. Our findings provide novel insights into the interspecies interactions that contribute to colonization resistance to S. pneumoniae and suggest that the nasopharyngeal microbiome may be a previously unrecognized mechanism by which environmental factors influence the risk of pneumococcal infections during childhood. Moreover, this work lays the foundation for future studies seeking to use targeted manipulation of the nasopharyngeal microbiome to prevent infections caused by S. pneumoniae.

Evolution of pneumococcal serotype epidemiology in Botswana following introduction of 13-valent pneumococcal conjugate vaccine

Pneumococcal conjugate vaccines reduce the burden of invasive pneumococcal disease, but the sustained effect of these vaccines can be diminished by an increase in disease caused by non-vaccine serotypes. To describe pneumococcal serotype epidemiology in Botswana following introduction of 13-valent pneumococcal conjugate vaccine (PCV-13) in July 2012, we performed molecular serotyping of 268 pneumococcal strains isolated from 221 children between 2012 and 2017. The median (interquartile range) age of the children included in this analysis was 6 (3,12) months. Fifty-nine percent of the children had received at least one dose of PCV-13 and 35% were fully vaccinated with PCV-13. While colonization by vaccine serotypes steadily declined following PCV-13 introduction, 25% of strains isolated more than 3 years after vaccine introduction were PCV-13 serotypes. We also observed an increase in colonization by non-vaccine serotypes 21 and 23B, which have been associated with invasive pneumococcal disease and antibiotic resistance in other settings.

Effect of Haemophilus influenzae Type b and 13-Valent Pneumococcal Conjugate Vaccines on Childhood Pneumonia Hospitalizations and Deaths in Botswana

BACKGROUND

Globally, pneumonia is the leading cause of death among children. Few data exist regarding the effect of Haemophilus influenzae type b (Hib) vaccine and 13-valent pneumococcal conjugate vaccine (PCV-13) on the burden of childhood pneumonia in African settings.

METHODS

We collected data on children aged 1 to 59 months at 3 hospitals in Botswana. Hib vaccine and PCV-13 were introduced in Botswana in November 2010 and July 2012, respectively. We compared pneumonia hospitalizations and deaths prevaccine (January 2009 to October 2010) with postvaccine (January 2013 to December 2017) using seasonally adjusted, interrupted time-series analyses.

RESULTS

We identified 6943 pneumonia hospitalizations and 201 pneumonia deaths. In the prevaccine period, pneumonia hospitalizations and deaths increased by 24% (rate, 1.24; 95% CI, .94-1.64) and 59% (rate, 1.59; 95% CI, .87-2.90) per year, respectively. Vaccine introduction was associated with a 48% (95% CI, 29-62%) decrease in the number of pneumonia hospitalizations and a 50% (95% CI, 1-75%) decrease in the number of pneumonia deaths between the end of the prevaccine period (October 2010) and the beginning of the postvaccine period (January 2013). During the postvaccine period, pneumonia hospitalizations and deaths declined by 6% (rate, .94; 95% CI, .89-.99) and 22% (rate, .78; 95% CI, .67-.92) per year, respectively.

CONCLUSIONS

Pneumonia hospitalizations and deaths among children declined sharply following introduction of Hib vaccine and PCV-13 in Botswana. This effect was sustained for more than 5 years after vaccine introduction, supporting the long-term effectiveness of these vaccines in preventing childhood pneumonia in Botswana.

Placental Transfer of Respiratory Syncytial Virus Antibody Among HIV-Exposed, Uninfected Infants

BACKGROUND

Maternal human immunodeficiency virus (HIV) infection is associated with lower placental transfer of antibodies specific to several childhood pathogens. Our objective for this study was to evaluate the effect of maternal HIV infection on the placental transfer of respiratory syncytial virus (RSV)-neutralizing antibodies.

METHODS

We conducted a cross-sectional study of mothers and their newborn infants at a tertiary hospital in Gaborone, Botswana, between March 2015 and December 2015. We measured serum RSV antibody levels by using a microneutralization assay. We used multivariable linear regression to evaluate the effect of maternal HIV infection on maternal RSV antibody levels, placental transfer of RSV antibodies, and newborn RSV antibody levels.

RESULTS

Of 316 mothers, 154 (49%) were infected with HIV. The placental transfer ratios for RSV antibodies to HIV-exposed, uninfected (HEU) and HIV-unexposed, uninfected infants were 1.02 and 1.15, respectively. The geometric mean titer (95% confidence interval) of RSV-neutralizing antibodies was 2657 (2251-3136) among HEU newborns and 2911 (2543-3331) among HIV-unexposed, uninfected newborns. In multivariable analyses, maternal HIV infection was associated with lower placental transfer of RSV antibodies (P = .02) and a lower level of RSV antibodies among newborns (P = .002). Among HEU newborns, higher birth weight (P = .004) and an undetectable maternal antenatal viral load (P = .01) were associated with more effective placental transfer of RSV antibodies.

CONCLUSIONS

Maternal human immunodeficiency virus (HIV) infection is associated with lower mother-to-fetus transfer of serum RSV-neutralizing antibodies. HEU infants should be prioritized for preventive interventions for RSV. Maternal viral suppression through combination antiretroviral therapy has the potential to improve immunity to RSV among HIV-exposed infants.

Investigating Mediators of the Poor Pneumonia Outcomes of Human Immunodeficiency Virus-Exposed but Uninfected Children

BACKGROUND

Human immunodeficiency virus-exposed but uninfected (HIV-EU) children have a higher mortality rate than the children of HIV-negative mothers (HIV-unexposed). Causal mediators of the poor health outcomes of HIV-EU children remain poorly defined.

METHODS

We conducted a hospital-based prospective cohort study of children aged 1 to 23 months with clinically defined pneumonia. The children were recruited at a referral hospital in Gaborone, Botswana, between April 2012 and June 2016. The primary outcome, treatment failure at 48 hours, was assessed by an investigator blinded to the children's HIV-exposure status. We examined associations between HIV exposure and pneumonia outcomes in HIV-uninfected children. We next determined whether the effect of HIV exposure on outcomes was mediated by low-birth-weight status, nonbreastfeeding, malnutrition, in utero exposure to combination antiretroviral therapy, or pneumonia severity.

RESULTS

A total of 352 HIV-uninfected children were included in these analyses, including 245 (70%) HIV-unexposed and 107 (30%) HIV-EU children. Their median age was 7.4 months, and 57% were male. Treatment failure occurred in 111 (32%) children, and 19 (5.4%) children died. HIV-EU children were more likely to fail treatment (risk ratio [RR], 1.57 [95% confidence interval (CI), 1.19-2.07]; P = .002) and had a higher in-hospital mortality rate (RR, 4.50 [95% CI, 1.86-10.85]; P = .001) than HIV-unexposed children. Nonbreastfeeding mediated 47% of the effect of HIV exposure on the risk of in-hospital death.

CONCLUSIONS

HIV-EU children have worse pneumonia outcomes than HIV-unexposed children. Nonbreastfeeding mediates nearly half of the effect of HIV exposure on pneumonia mortality. Our findings provide additional evidence for a mortality benefit of breastfeeding by HIV-EU children.

The effect of exposure to wood smoke on outcomes of childhood pneumonia in Botswana

SETTING

Tertiary hospital in Gaborone, Botswana.

OBJECTIVE

To examine whether exposure to wood smoke worsens outcomes of childhood pneumonia.

DESIGN

Prospective cohort study of children aged 1-23 months meeting clinical criteria for pneumonia. Household use of wood as a cooking fuel was assessed during a face-to-face questionnaire with care givers. We estimated crude and adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for treatment failure at 48 h by household use of wood as a cooking fuel. We assessed for effect modification by age (1-5 vs. 6-23 months) and malnutrition (none vs. moderate vs. severe).

RESULTS

The median age of the 284 enrolled children was 5.9 months; 17% had moderate or severe malnutrition. Ninety-nine (35%) children failed treatment at 48 h and 17 (6%) died. In multivariable analyses, household use of wood as a cooking fuel increased the risk of treatment failure at 48 h (RR 1.44, 95%CI 1.09-1.92, P = 0.01). This association differed by child nutritional status (P = 0.02), with a detrimental effect observed only among children with no or moderate malnutrition.

CONCLUSIONS

Exposure to wood smoke worsens outcomes for childhood pneumonia. Efforts to prevent exposure to smoke from unprocessed fuels may improve pneumonia outcomes among children.

Association between efavirenz-based compared with nevirapine-based antiretroviral regimens and virological failure in HIV-infected children

IMPORTANCE

Worldwide, the nonnucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz and nevirapine are commonly used in first-line antiretroviral regimens in both adults and children with human immunodeficiency virus (HIV) infection. Data on the comparative effectiveness of these medications in children are limited.

OBJECTIVE

To investigate whether virological failure is more likely among children who initiated 1 or the other NNRTI-based HIV treatment.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of children (aged 3-16 years) who initiated efavirenz-based (n = 421) or nevirapine-based (n = 383) treatment between April 2002 and January 2011 at a large pediatric HIV care setting in Botswana.

MAIN OUTCOMES AND MEASURES

The primary outcome was time from initiation of therapy to virological failure. Virological failure was defined as lack of plasma HIV RNA suppression to less than 400 copies/mL by 6 months or confirmed HIV RNA of 400 copies/mL or greater after suppression. Cox proportional hazards regression analysis compared time to virological failure by regimen. Multivariable Cox regression controlled for age, sex, baseline immunologic category, baseline clinical category, baseline viral load, nutritional status, NRTIs used, receipt of single-dose nevirapine, and treatment for tuberculosis.

RESULTS

With a median follow-up time of 69 months (range, 6-112 months; interquartile range, 23-87 months), 57 children (13.5%; 95% CI, 10.4%-17.2%) initiating treatment with efavirenz and 101 children (26.4%; 95% CI, 22.0%-31.1%) initiating treatment with nevirapine had virological failure. There were 11 children (2.6%; 95% CI, 1.3%-4.6%) receiving efavirenz and 20 children (5.2%; 95% CI, 3.2%-7.9%) receiving nevirapine who never achieved virological suppression. The Cox proportional hazard ratio for the combined virological failure end point was 2.0 (95% CI, 1.4-2.7; log rank P < .001, favoring efavirenz). None of the measured covariates affected the estimated hazard ratio in the multivariable analyses.

CONCLUSIONS AND RELEVANCE

Among children aged 3 to 16 years infected with HIV and treated at a clinic in Botswana, the use of efavirenz compared with nevirapine as initial antiretroviral treatment was associated with less virological failure. These findings may warrant additional research evaluating the use of efavirenz and nevirapine for pediatric patients.