Immunologic basis for revaccination of HIV-infected children receiving HAART

Measles immunity gaps among children and adolescents with HIV in Zambia despite high measles vaccination and antiretroviral therapy coverage

OBJECTIVE

The study objective was to identify measles and rubella immunity gaps among people with HIV (PWH) in Zambia despite high measles vaccine coverage and widespread access to antiretroviral therapy.

DESIGN

Nationally representative cross-sectional serosurvey using biorepository specimens.

METHODS

Blood specimens collected in the Zambia Population HIV Impact Assessment survey (ZAMPHIA) of 2016 were tested for measles and rubella immunoglobulin G (IgG) antibodies by enzyme immunoassay. Hierarchical generalized additive models were fit to characterize age-specific measles and rubella seroprevalence profiles by HIV infection status. Log-binomial regression was performed to identify factors associated with seronegativity.

RESULTS

Of the 25 383 specimens, a subsample of 11 500 were selected and 9852 (85%) were successfully tested. Measles seroprevalence was lower among PWH compared with HIV-uninfected individuals until approximately 30 years of age. Among children younger than the age of 10 years, measles seroprevalence was 47.2% [95% confidence interval (CI): 32.7, 61.7] in PWH and 76.4% (95% CI: 74.9, 78.0) in HIV-uninfected children in same age category. In contrast, rubella seroprevalence was higher among PWH than HIV-uninfected individuals, particularly for children younger than 10 years (68.6% vs. 44.3%, P  < 0.001). Having a detectable viral load was associated with being measles seronegative (adjusted prevalence ratio 0.15, 95% CI: 0.06, 0.38).

CONCLUSIONS

These results from a nationally representative serosurvey demonstrate persistence of measles immunity gaps among PWH younger than 30 years of age. There is need to implement the World Health Organization's recommendation to revaccinate children living with HIV against measles following immune reconstitution with antiretroviral therapy to protect these children and prevent measles outbreaks.

Measles Seroprevalence and Vaccine Responses in Human Immunodeficiency Virus-infected Adolescents and Adults: A Systematic Review

BACKGROUND

The World Health Organization (WHO) recommends an additional dose of measles-containing vaccine (MCV) for human immunodeficiency virus (HIV)-infected children receiving highly active antiretroviral therapy following immune reconstitution. We conducted a systematic review to synthesize available evidence regarding measles seroprevalence and measles vaccine immunogenicity, efficacy, and safety in HIV-infected adolescents and adults to provide the evidence base for recommendations on the need for measles vaccination.

METHODS

We conducted searches of 8 databases through 26 September 2017. Identified studies were screened independently by 2 reviewers.

RESULTS

The search identified 30 studies meeting inclusion criteria. Across studies, measles seroprevalence among HIV-infected adolescents and adults was high (median, 92%; 27 studies), with no significant difference compared to HIV-uninfected participants (10 studies). In 6 studies that evaluated the immunogenicity of MCVs among seronegative HIV-infected adults, measles seropositivity at end of follow-up ranged from 0% to 56% (median, 39%). No severe adverse events were reported following measles vaccination in HIV-infected patients.

CONCLUSIONS

Based on similar measles seroprevalence between HIV-infected and HIV-uninfected adolescents and adults, and the low response to vaccination, these studies do not support the need for an additional dose of MCV in HIV-infected adolescents and adults. These findings support WHO guidelines that measles vaccine be administered to potentially susceptible, asymptomatic HIV-infected adults, and may be considered for those with symptomatic HIV infection if not severely immunosuppressed. Measles-susceptible adolescents and adults, regardless of HIV status, may require targeted vaccination efforts to reach critical vaccination thresholds and achieve regional elimination goals.

Immunogenicity and Safety of the Measles Vaccine in HIV-Infected Children: An Updated Systematic Review

Children infected with human immunodeficiency virus (HIV) are at increased risk of measles morbidity and mortality. We searched abstracts from the PubMed, Embase, and Latin American and Caribbean Center on Health Sciences Information databases for articles published from the earliest date available through September 26, 2017. The primary outcome of interest was serological responses to measles vaccine, stratified by HIV infection status. A total of 2,858 potentially eligible articles were identified, and the final review included 12 studies published between 1992 and 2013, 9 of which reported data on vaccine safety. The studies we included represented 3,573 children, of whom at least 335 were infected with HIV, 788 were HIV-exposed but not infected, and 1,478 were unexposed to HIV. Four of the 12 studies found statistically significant reductions in seropositivity among HIV-infected children compared with HIV-uninfected children within 4 months of vaccination (prevalence ratio range, 0.44-0.70), and forest plots provided visual trends of decreasing immunity over time among HIV-infected children in 2 additional studies. No vaccine-related deaths or serious adverse events were reported. This updated review demonstrated limitations of the existing published literature but supported evidence of reduced immunogenicity of measles vaccine among HIV-infected children, supporting the World Health Organization recommendation to revaccinate HIV-infected children against measles following immune reconstitution with combination antiretroviral therapy.

Safety and Immunogenicity of Measles Vaccination in HIV-Infected and HIV-Exposed Uninfected Children: A Systematic Review and Meta-Analysis

BACKGROUND

HIV-infected and HIV-exposed uninfected (HEU) children have an increased risk of measles that may be due to altered immune responses or suboptimal timing of measles vaccination. We aimed to evaluate the safety and immunogenicity of measles vaccination in HIV-infected and HEU children.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Embase, Cochrane Library, CINAHL, Global Health Library and IndMED on May 9, 2018. Studies were included if they reported on safety or seroresponse (either seroprotection/seropositivity/seroconversion) after measles vaccination in HIV-infected or HEU children. We calculated pooled estimates to compare immunogenicity outcomes between HIV-infected, HEU and HIV-unexposed children, using risk ratios [RRs] (with 95%CIs). PROSPERO registration number: CRD42017057411.

FINDINGS

Seventy-one studies met the inclusion criteria (15,363 children). Twenty-eight studies reported on safety; vaccine-associated adverse events and deaths were uncommon. Sixty-two studies reported on immunogenicity, 27 were included in the meta-analysis. HIV-infected children had lower seroresponse rates after primary vaccination compared with HIV-unexposed (RR 0.74; 95%CI: 0.61-0.90, I 2  = 85.9%) and HEU children (0.78; 0.69-0.88, I 2  = 77.1%), which was mitigated by antiretroviral therapy and time interval between vaccination and serology. HEU and HIV-unexposed children had similar seroresponses. Vaccination at 6-months resulted in similar proportions of HIV-infected children having seroresponse compared with HIV-unexposed (0.96; 0.77-1.19) and HEU children (1.00; 0.73-1.37, I 2  = 63.7%).

INTERPRETATION

Primary measles vaccination at 6-months of age may provide protection against measles during early infancy in settings with high prevalence of maternal HIV-infection, however, further studies are needed to evaluate this strategy in HEU children and HIV-infected children receiving antiretroviral therapy.

FUNDING

South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation in Vaccine Preventable Diseases; Medical Research Council: Respiratory and Meningeal Pathogens Research Unit.

Impact of HIV infection and highly active antiretroviral therapy (HAART) on B cell subpopulations in children

B-cells play an important role in defending children against various infections. In view of scare data, we undertook this prospective cohort study to describe B cell compartment in HIV infected children (<5 years of age) and the effect of HAART on B cell subpopulations. HIV infected children (<5 years) from Pediatric HIV services of the Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, were recruited (April 2012-December 2015). The enrolled HIV-1 infected children (n = 59) were followed up regularly for 12 months; healthy controls (n = 51) included HIV uninfected children with no major illness. Flow cytometry was performed on fresh EDTA-treated blood samples to characterize B cell subpopulations. In HIV-infected children, marked depletion of naive (P = 0.003), non-switched memory (P = 0.02), mature (P = 0.0005), resting memory (P < 0.0001) B cells, and expansion of double negative memory (P < 0.0001), activated memory (P < 0.0001) and tissue like memory (P < 0.0001) B cells were observed as compared to healthy controls. In children started on HAART, at the end of 12 months of therapy, frequencies of non-switched memory (P = 0.04), switched memory (P = 0.01), and resting memory (P = 0.003) B cells were lower; activated memory (P = 0.04), and tissue-like memory (P = 0.0001) B cells were still higher than healthy controls. HIV infection resulted in reduced memory B cells in HIV infected children. Following HAART, there was normalization of some B cell subpopulations. The study emphasizes the need of re-vaccination in HIV infected children to maintain the memory B cell pool and adequate humoral immune response against infections.

Sustained Responses to Measles Revaccination at 24 Months in HIV-infected Children on Antiretroviral Therapy in Kenya

BACKGROUND

There are limited data on whether HIV-infected children in resource-limited countries who are receiving antiretroviral therapy (ART) are able to produce sustained, protective levels of measles antibody after multiple measles vaccinations.

METHODS

We administered an additional measles vaccine to HIV-infected children 15 months to 12 years of age receiving ART in Nairobi, Kenya. Measles antibody concentrations were determined by enzyme-linked immunosorbent assay at enrollment, 1 month, 12 months and 24 months post revaccination.

RESULTS

At enrollment, 125 (54%) of 232 study participants had protective concentrations of measles antibody. Measles seropositivity increased to 98% of all children at 1 month post revaccination but decreased to 71% at 12 months and 60% at 24 months post revaccination. Measles seroconversion and sustained measles seropositivity among those who were measles seronegative at enrollment was 25% at 24 months post revaccination. In this group, 39% of children with <50 copies/mL plasma HIV RNA measles seroconverted compared to 4% of children with plasma HIV RNA ≥1000 copies/mL (P = 0.018).

CONCLUSIONS

Measles revaccination can result in a sustained antibody response in a subset of HIV-infected children receiving ART, especially among those with HIV suppression.

Susceptibility to Measles Among Perinatally HIV-Infected Adolescents and Young Adults

Among our cohort of adolescents and young adults with perinatally acquired human immunodeficiency virus, few (17.6%) had measles protective antibodies by plaque reduction neutralization (PRN). Agreement was demonstrated between the commercial enzyme immunoassay and the PRN assay (K = 0.59 [95% confidence interval: 0.23-0.95]). Further studies are needed to understand the determinants of immunity in this population.

Changes in cellular immune activation and memory T-cell subsets in HIV-infected Zambian children receiving HAART

BACKGROUND

Increased exposure to a broad array of pathogens in children residing in sub-Saharan Africa may lead to heightened immune activation and increased proportions of memory T cells. Changes in the size of these cellular subsets have implications for restoration of normal immune function after treatment with highly active antiretroviral therapy (HAART) and are not well characterized in young sub-Saharan African children.

METHODS

CD4⁺ and CD8⁺ T-cell subsets were measured by flow cytometry in 157 HIV-infected Zambian children before and at 3-month intervals during HAART for up to 30 months and in 34 control children at a single study visit.

RESULTS

Before HAART, HIV-infected children had higher levels of activated and effector memory (EM) CD4⁺ and CD8⁺ T cells, and lower levels of naive T cells and CD8⁺ T cells expressing IL-7Rα, compared with control children. The median duration of follow-up was 14.9 months (interquartile range, 6.4-23.2) among 120 HIV-infected children with at least 1 study follow-up visit. Levels of immune activation and EM CD4⁺ T cells declined within 6 months of HAART, but the percentages of EM CD4 T cells and effector CD8⁺ T cells remained elevated through 30 months of HAART. IL-7Rα-expressing CD8⁺ T cells increased with HAART, suggesting expansion of memory capacity.

CONCLUSIONS

HAART significantly reduced levels of immune activation and EM CD4⁺ T cells, and promoted reconstitution of naive T cells and IL-7Rα-expressing CD8⁺ T cells. However, persistently high levels of EM CD4⁺ T cells in HIV-infected children may reflect chronic perturbations in T-cell subset composition.

Risk factors for incomplete immunization in children with HIV infection

OBJECTIVE

To document the immunization rates, factors associated with incomplete immunization, and missed opportunities for immunizations in children affected by HIV presenting for routine outpatient follow-up.

METHODS

A cross-sectional study of immunization status of children affected by HIV presenting for routine outpatient care was conducted.

RESULTS

Two hundred and six HIV affected children were enrolled. The median age of children in this cohort was 6 y. One hundred ninety seven of 206 children were HIV infected, nine were HIV exposed, but indeterminate. Fifty (25 %) children had incomplete immunizations per the Universal Immunization Program (UIP) of India. Hundred percent of children had received OPV. Ninety three percent of children got their UIP vaccines from a government clinic. Children with incomplete immunization were older, median age of 8 compared to 5 (p = 0.003). Each year of maternal education increased the odds of having a child with complete UIP immunizations by 1.18 (p = 0.008)-children of mothers with 6 y of education compared to those with no education were seven times more likely to have complete UIP vaccine status. The average number of visits to the clinic by an individual child in a year was 4. This represents 200 missed opportunities for immunizations.

CONCLUSIONS

HIV infected children are at risk for incomplete immunization coverage though they regularly access medical care. Including routine immunizations, particularly catch-up immunizations in programs for HIV infected children maybe an effective way of protecting these children from vaccine preventable disease.

Changes in measles serostatus among HIV-infected Zambian children initiating antiretroviral therapy before and after the 2010 measles outbreak and supplemental immunization activities

BACKGROUND

In 2010, Zambia had a large measles outbreak, providing an opportunity to measure changes in measles serostatus following highly active antiretroviral therapy (HAART), exposure to measles virus, and revaccination among children infected with human immunodeficiency virus (HIV).

METHODS

A prospective cohort study of 169 HIV-infected Zambian children aged 9-60 months with a history of measles vaccination was conducted to characterize the effects of HAART and revaccination on measles immunoglobulin G (IgG) serostatus by enzyme immunoassay.

RESULTS

Prior to the measles outbreak, only 23% of HIV-infected children were measles IgG seropositive at HAART initiation. After adjusting for 6-month changes in baseline age and 5% changes in nadir CD4(+) T-cell percentage, HAART was not associated with measles IgG seroconversion. However, 18 of 19 children seroconverted after revaccination. Eight children seroconverted during the outbreak without revaccination and were likely exposed to wild-type measles virus, but none were reported to have had clinical measles.

CONCLUSIONS

Immune reconstitution after HAART initiation did not restore protective levels of measles IgG antibodies, but almost all children developed protective antibody levels after revaccination. Some previously vaccinated HIV-infected children had serological evidence of exposure to wild-type measles virus without a reported history of measles.

Suboptimal immune reconstitution in vertically HIV infected children: a view on how HIV replication and timing of HAART initiation can impact on T and B-cell compartment

Today, HIV-infected children who have access to treatment face a chronic rather than a progressive and fatal disease. As a result, new challenges are emerging in the field. Recent lines of evidence outline several factors that can differently affect the ability of the immune system to fully reconstitute and to mount specific immune responses in children receiving HAART. In this paper, we review the underlying mechanisms of immune reconstitution after HAART initiation among vertically HIV-infected children analyzing the possible causes of suboptimal responses.