Cellular and humoral immune responses to a tetanus toxoid booster in perinatally HIV-1-infected children and adolescents receiving highly active antiretroviral therapy (HAART)

Prevalence of protective tetanus antibodies and immunological response following tetanus toxoid vaccination among men seeking medical circumcision services in Uganda

Introduction

Tetanus infection associated with men who had male circumcision has been reported in East Africa, suggesting a need for tetanus toxoid-containing vaccines (TTCV).

Objective

To determine the prevalence of tetanus toxoid antibodies following vaccination among men seeking circumcision.

Methods

We enrolled 620 consenting men who completed a questionnaire and received TTCV at enrollment (day 0) prior to circumcision on day 28. Blood samples were obtained at day 0 from all enrollees and on days 14, 28 and 42 from a random sample of 237 participants. Tetanus toxoid (TT) IgG antibody levels were assayed using EUROIMMUN. Analyses included prevalence of TT antibodies at enrollment and used a mixed effects model to determine the immunological response.

Results

Mean age was 21.4 years, 65.2% had knowledge of tetanus, 56.6% knew how tetanus was contracted, 22.8% reported ever receipt of TTCV, and 16.8% had current/recently healed wounds. Insufficient tetanus immunity was 57.1% at enrollment, 7.2% at day 14, 3.8% at day 28, and 0% at day 42. Antibody concentration was 0.44IU/ml (CI 0.35–0.53) on day 0, 3.86IU/ml (CI 3.60–4.11) on day 14, 4.05IU/ml (CI 3.81–4.29) on day 28, and 4.48IU/ml (CI 4.28–4.68) on day 42. TT antibodies increased by 0.24IU/ml (CI 0.23, 0.26) between days 0 and 14 and by 0.023IU/ml (CI 0.015, 0.031) between days 14 and 42 days. Immunological response was poorer in HIV-infected clients and men aged 35+ years.

Conclusion

Insufficient immunity was common prior to TTCV, and a protective immunological response was achieved by day 14. Circumcision may safely be provided 14 days after vaccination in HIV-uninfected men aged less than 35 years.

FOXP3+Helios+ Regulatory T Cells, Immune Activation, and Advancing Disease in HIV-Infected Children

Regulatory T cells (Tregs) are functionally suppressive CD4 T cells, critical for establishing peripheral tolerance and controlling inflammatory responses. Previous reports of Tregs during chronic HIV disease have conflicting results with higher or lower levels compared with controls. Identifying true Tregs with suppressive activity proves challenging during HIV infection, as traditional Treg markers, CD25 and FOXP3, may transiently upregulate expression as a result of immune activation (IA). Helios is an Ikaros family transcription factor that marks natural Tregs with suppressive activity and does not upregulate expression after activation. Coexpression of FOXP3 and Helios has been suggested as a highly specific marker of "bona fide" Tregs. We evaluated Treg subsets by FOXP3 coexpressed with either CD25 or Helios and their association with HIV disease progression in perinatally infected HIV-positive children. Identifying Tregs by FOXP3 coexpression with Helios rather than CD25 revealed markedly higher Treg frequencies, particularly in HIV+ children. Regardless of antiretroviral therapy, HIV-infected children had a selective expansion of memory FOXP3+Helios+ Tregs. The rise in memory Tregs correlated with declining HIV clinical status, indicated by falling CD4 percentages and CD4:CD8 ratios and increasing HIV plasma viremia and IA. In addition, untreated HIV+ children exhibited an imbalance between the levels of Tregs and activated T cells. Finally, memory Tregs expressed IA markers CD38 and Ki67 and exhaustion marker, PD-1, that tightly correlated with a similar phenotype in memory CD4 T cells. Overall, HIV-infected children had significant disruptions of memory Tregs that associated with advancing HIV disease.

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.

Long-term effect of highly active antiretroviral therapy on immunologic features in children

BACKGROUND

Highly active antiretroviral therapy (HAART) has transformed human immunodeficiency virus infection (HIV) into a chronic condition. The effects of long-term HAART on the immune system activity of early infected children are not fully understood. Hence, the aim of this review is to investigate immune system recovery and residual alteration in HIV-infected children receiving HAART in high-income countries.

METHODS

A systematic review was performed by searches of PubMed and references of the relevant articles. Studies published between January 1, 2000 and April 1, 2014 and conducted in high-income countries reporting data on immunological features in HIV-infected children receiving HAART were included in this review.

RESULTS

Fifty-three articles were included in this review. Present knowledge on B-cell and T-cell function, immunoglobulin production, response to vaccine and innate immune system activity in HIV-infected children receiving HAART is discussed.

CONCLUSION

Starting therapy as soon as diagnosis is ascertained and monitoring vaccine response in children under HAART are the most important tools to safeguard immunological function in HIV-infected children.

Long-term immune responses to vaccination in HIV-infected patients: a systematic review and meta-analysis

Vaccine-induced antibodies may wane more quickly in persons living with human immunodeficiency virus (HIV) than in healthy individuals. We reviewed the literature on vaccines routinely recommended in HIV-infected patients to estimate how seroprotection decreases over time in those who initially responded to immunization. For each study retrieved from the literature, the decrease of seroprotection was modeled with a log binomial generalized linear model, and data were pooled in a meta-analysis to provide estimates of seroprotection 2 and 5 years after the last vaccine administration. Our analyses confirmed that the duration of seroprotection was shorter in HIV-infected patients and that with current guidelines, a substantial proportion of patients would have lost protective antibodies before a booster was proposed. We therefore discuss the implications for the monitoring of antibody levels and timing of revaccination in these patients.

Impaired cellular immune response to tetanus toxoid but not to cytomegalovirus in effectively HAART-treated HIV-infected children

Despite of highly active antiretroviral therapy, the response to vaccines in HIV-infected children is poor and short-lived, probably due to a defect in cellular immune responses. We compared the cellular immune response (assessed in terms of IFN-γ production) to tetanus toxoid and to cytomegalovirus in a series of 13 HIV-perinatally-infected children and adolescents with optimal immunovirological response to first line antiretroviral therapy, implemented during chronic infection. A stronger cellular response to cytomegalovirus (11 out of 13 patients) was observed, as compared to tetanus toxoid (1 out of 13; p=0.003). These results suggest that the repeated exposition to CMV, as opposed to the past exposition to TT, is able to maintain an effective antigen-specific immune response in stable HIV-infected pediatric patients and strengthen current recommendations on immunization practices in these children.

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

Current evidence on routine immunization of HIV-1 infected children point out the need for a special vaccine schedule in this population. However, optimal strategies for identifying individuals susceptible to infections, and then offering them sustained protection through appropriate immunization schedule, both in terms of timing and number of vaccine doses, still remain to be elucidated. Understanding the degree of immune recovery after HAART initiation is important in guiding administration of routine vaccination in HIV-1 infected children. Although quantitative measures (e.g., CD4+ T-cell counts and immunoglobulin levels) are frequently performed to evaluate immune parameters, these measures do not fully mirror functional immune recovery. Here, we will review the status of single mandatory and recommended vaccines for HIV-1 infected children in relation to immune recovery after HAART initiation with the aim of identifying new means to help design personalized vaccine schedules for this population.

Immunization in special populations

In summary, immunizations in special populations require understanding the underlying disease and how it might affect the immune system's ability to mount an antibody response to vaccines or predispose certain patient populations to developing certain serious infections. There is still a great need for research on the optimal timing of vaccines after transplants, how to assess protection and development of a protective antibody response after immunization, and whether certain groups (eg, HIV) need to be revaccinated after a certain amount of time if their antibody levels decline. In addition, there are limited data on efficacy of the newer vaccines in these special patient populations, which also requires further investigation.

Vaccination in HIV-infected individuals

Vaccinations are key to limiting the increased risk of severe infectious diseases in HIV-infected patients for whom the risk–benefit ratio has been re-evaluated. Vaccine safety and immunogenicity depend on both vaccine type and immune deficiency, while vaccine-induced immune activation promotes a transient increase in viral load. Vaccine immunogenicity is reduced and wanes more rapidly, strengthening the need for revaccination. While inactivated vaccines are safe, attenuated vaccines are theoretically contraindicated, but the risk of infectious diseases outweighs the risks of severe adverse events in endemic areas, where the majority of HIV-infected individuals live, thus allowing their use when immune deficiency is moderate. Immune reconstitution with HAART has improved vaccine immune response, highlighting the importance of global access to and early initiation of therapy.

Immune responses to measles and tetanus vaccines among Kenyan human immunodeficiency virus type 1 (HIV-1)-infected children pre- and post-highly active antiretroviral therapy and revaccination

BACKGROUND

: HIV-1-infected children have lower response rates after measles and tetanus immunization than uninfected children. We determined the extent to which highly active antiretroviral therapy (HAART) augments vaccine immunity and promotes responses to revaccination.

METHODS

: Previously immunized, antiretroviral-naive HIV-1-infected children were evaluated for immunity against measles and tetanus. After 6 months on HAART, children meeting CD4% criteria (>15%) who were persistently antibody negative were revaccinated and immunity was reassessed.

RESULTS

: At enrollment, among 90 children with mean age of 4.9 years, 67% had negative measles IgG and 22% negative tetanus IgG. Among 62 children completing 6 months on HAART, 17 (40%) of 43 without protective measles IgG converted and 10 (53%) of 19 positive children lost measles responses (P = 0.3). Children who lost responses had significantly lower measles antibody concentrations than those who remained measles IgG positive during follow-up (7.1 vs. 20.3 mg/mL; P = 0.003). Three (23%) of 13 children negative for tetanus IgG spontaneously seroconverted on HAART, while 15 (31%) of 49 children lost tetanus antibody (P = 0.008). There was a nonsignificant trend for an association between spontaneous measles seroconversion and lower baseline HIV-1 viral load (P = 0.06). Tetanus seroconversion was associated with older age (P = 0.03). After revaccination, positive responses were observed in 78% and 75% of children reimmunized against measles and tetanus, respectively.

CONCLUSIONS

: After 6 months of HAART, more than half of previously immunized children still lacked positive measles antibody. With increased use of HAART in pediatric populations, revaccination against measles and tetanus should be considered to boost response rates and immunization coverage.

Impaired immunity to recall antigens and neoantigens in severely immunocompromised children and adolescents during the first year of effective highly active antiretroviral therapy

BACKGROUND

We studied whether severely immunocompromised, human immunodeficiency virus (HIV)-infected children who were beginning highly active antiretroviral therapy (HAART) or changing HAART regimens could spontaneously respond to a recall antigen (tetanus toxoid [TT] vaccine) or respond to a recall antigen and neoantigen (hepatitis A virus [HAV] vaccine) after 3 vaccinations.

METHODS

A total of 46 children who had CD4 cell percentages <15% and who demonstrated a >0.75-log reduction in plasma HIV RNA levels within 4 weeks of starting HAART were randomized to receive vaccinations with either TT or HAV vaccines during the first 6 months of HAART. Study subjects then received the alternate vaccine during the next 6 months of HAART.

RESULTS

Despite the early decline in viremia and the later increase in the percentage of CD4 T cells, spontaneous recovery of cell-mediated immunity (CMI) was not seen for TT. Serologic responses to TT required 3 vaccinations and were comparable in both groups. Serologic responses to HAV were infrequent and of low titer, although the group that received HAV vaccine after receiving TT vaccine performed somewhat better. CMI to HAV was virtually absent.

CONCLUSIONS

Severely immunocompromised children who are receiving HAART develop CMI and antibody to a recall antigen independent of the timing of vaccination, but they require a primary series of vaccinations. Antibodies to a neoantigen, HAV, developed when vaccination was delayed after initiation of HAART. CMI to a neoantigen was difficult to establish.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00004735/PACTG P1006 .

Human papillomavirus vaccines in HIV-positive men and women

PURPOSE OF REVIEW

Individuals with HIV are at greater risk of human papillomavirus-related cancers. This report will assess the potential and limitations of vaccines against human papillomavirus in HIV-positive individuals.

RECENT FINDINGS

A worldwide meta-analysis of published data established the under-representation of HPV16, and increased prevalence of multiple-type human papillomavirus infections in HIV-positive women. Associations between HIV-related immunodepression, the progression of human papillomavirus infection to cervical lesions, and an increased risk of cervical cancer in women with HIV have also been shown. An increased incidence of human papillomavirus infection in anal and vulvar/vaginal neoplasia has been reported in individuals with HIV. A prophylactic vaccine against HPV6, 11, 16 and 18 has been licensed, and one against HPV16 and 18 is under evaluation. Both have shown efficacy against persistent infection, as well as related human papillomavirus cervical lesions for up to 5 years. Preliminary results have also been reported on therapeutic vaccines, notably for the treatment of cervical intraepithelial neoplasia grades 2 and 3.

SUMMARY

The safety and efficacy of human papillomavirus vaccines in individuals with HIV need to be assessed to prevent cervical cancer in current and future generations. Screening for human papillomavirus-related cancer among HIV patients should be undertaken.