Immunity to human immunodeficiency virus (HIV) in children with chronic HIV infection receiving highly active antiretroviral therapy

Cytomegalovirus and paediatric HIV infection

Cytomegalovirus (CMV) was among the most common AIDS-defining illnesses prior to the advent of combination antiretroviral therapy (ART). In the ART era, CMV disease remains a significant public health threat among HIV-infected adults and children with delayed HIV diagnosis. CMV co-infection may additionally contribute to accelerated HIV progression, development of inflammation-related comorbidities, immune senescence and developmental deficits. Elimination of CMV would have tremendous public health significance and is an important priority; however, current vaccine strategies are not targeted at HIV-infected individuals. Antivirals active against CMV may be a novel strategy to prevent acquisition and improve outcomes, but haematological side effects are common and necessitate cautious use in pregnant women and infants. Studies in HIV-infected children on ART lag behind adults, and the clinical significance of CMV in this population is not well understood. Furthermore, the effects of CMV in HIV-exposed uninfected (HEU) children need to be clarified to understand whether CMV interventions should also be a priority for this growing population. This review discusses our current understanding of CMV transmission and pathogenesis in HIV-exposed children and highlights unanswered questions for future research.

Gag-Specific CD4 and CD8 T-Cell Proliferation in Adolescents and Young Adults with Perinatally Acquired HIV-1 Infection Is Associated with Ethnicity - The ANRS-EP38-IMMIP Study

The ANRS-EP38-IMMIP study aimed to provide a detailed assessment of the immune status of perinatally infected youths living in France. We studied Gag-specific CD4 and CD8 T-cell proliferation and the association between the proliferation of these cells, demographic factors and HIV disease history. We included 93 youths aged between 15 and 24 years who had been perinatally infected with HIV. Sixty-nine had undergone valid CFSE-based T-cell proliferation assays. Gag-specific proliferation of CD4 and CD8 T cells was detected in 12 (16%) and 30 (38%) patients, respectively. The Gag-specific proliferation of CD4 and CD8 T cells was more frequently observed in black patients than in patients from other ethnic groups (CD4: 32% vs. 4%, P = 0.001; CD8: 55% vs. 26%, P = 0.02). Among aviremic patients, the duration of viral suppression was shorter in CD8 responders than in CD8 nonresponders (medians: 54 vs. 20 months, P = 0.04). Among viremic patients, CD8 responders had significantly lower plasma HIV RNA levels than CD8 nonresponders (2.7 vs. 3.7 log₁₀ HIV-RNA copies/ml, P = 0.02). In multivariate analyses including sex and HIV-1 subtype as covariables, Gag-specific CD4 T-cell proliferation was associated only with ethnicity, whereas Gag-specific CD8 T-cell proliferation was associated with both ethnicity and the duration of viral suppression. Both CD4 and CD8 responders reached their nadir CD4 T-cell percentages at younger ages than their nonresponder counterparts (6 vs. 8 years, P = 0.04 for both CD4 and CD8 T-cell proliferation). However, these associations were not significant in multivariate analysis. In conclusion, after at least 15 years of HIV infection, Gag-specific T-cell proliferation was found to be more frequent in black youths than in patients of other ethnic groups, despite all the patients being born in the same country, with similar access to care.

Humoral, mucosal, and cell-mediated immunity against vaccine and nonvaccine genotypes after administration of quadrivalent human papillomavirus vaccine to HIV-infected children

OBJECTIVES

To characterize the immunogenicity of a quadrivalent human papillomavirus vaccine (QHPV) in human immunodeficiency virus (HIV)-infected children, we studied their immune responses to 3 or 4 doses.

METHODS

HIV-infected children aged 7-12 years with a CD4 cell percentage of ≥15% of lymphocytes, received 3 doses of QHPV with or without a fourth dose after 72 weeks. Type-specific and cross-reactive antibodies and cell-mediated immunity were measured.

RESULTS

Type-specific antibodies to HPV6, 11, and 16 were detected in 100% and ≥94% of children at 4 and 72 weeks, respectively, after the third QHPV dose. Corresponding numbers for HPV18 were 97% and 76%, respectively. A fourth QHPV dose increased seropositivity to ≥96% for all vaccine genotypes. Four weeks after the third QHPV dose, 67% of vaccinees seroconverted to HPV31, an HPV16-related genotype not in the vaccine; 69% and 39% of vaccinees developed mucosal HPV16 and 18 immunoglobulin G antibodies, respectively; and 60% and 52% of vaccinees developed cytotoxic T lymphocytes (CTLs) for HPV16 and 31, respectively.

CONCLUSIONS

Three QHPV doses generated robust and persistent antibodies to HPV6, 11, and 16 but comparatively weaker responses to HPV18. A fourth dose increased antibodies against all vaccine genotypes in an anamnestic fashion. CTLs and mucosal antibodies against vaccine genotypes, as well as cross-reactive antibodies and CTL against nonvaccine genotypes, were detected.

Effect of nucleoside and nucleotide analog reverse transcriptase inhibitors on cell-mediated immune functions

Nucleoside analog reverse transcriptase inhibitors (NRTIs) constitute the most commonly used drugs in antiretroviral therapy. NRTIs differ with respect to their host cell toxicity. We compared the in vitro effect of zidovudine (AZT; 2 μg/ml), lamivudine (3TC; 5 μg/ml), stavudine (d4T; 1 μg/ml), and tenofovir (TFV; 1 μg/ml) on Candida cell-mediated immunity (CMI) of peripheral blood mononuclear cells (PBMCs). The concentrations of the active derivative AZT-triphosphate were 4-fold higher in Candida-stimulated compared with unstimulated PBMCs (p = 0.01), but those of 3TC-triphosphate and TFV-diphosphate did not differ significantly. AZT treatment decreased proliferation of unstimulated and Candida-stimulated PBMCs and IFN-γ ELISPOT responses; 3TC decreased proliferation of unstimulated PBMCs only; d4T and TFV decreased proliferation of Candida-stimulated PBMCs only. AZT, but not the other NRTIs, increased unstimulated PBMC apoptosis measured by caspase 3 activity. All NRTIs increased annexin-V-measured apoptosis of Candida-stimulated PBMCs. The effect of d4T on apoptosis of Candida-stimulated PBMCs strongly correlated with its inhibitory effect on mitochondrial DNA synthesis (r² = 0.94; p = 0.007). The other NRTIs did not significantly decrease the mitochondrial:nuclear DNA ratios in Candida-stimulated or unstimulated cultures, suggesting that other mechanisms mediated their effect on apoptosis and CMI. In conclusion, AZT had the most pronounced inhibitory effect on CMI. Further studies are warranted to determine the clinical significance of this observation.

Optimization of storage and shipment of cryopreserved peripheral blood mononuclear cells from HIV-infected and uninfected individuals for ELISPOT assays

Functional immunologic assays using cryopreserved peripheral blood mononuclear cells (PBMC) are influenced by blood processing, storage and shipment. The objective of this study was to compare the viability, recovery and ELISPOT results of PBMC stored and shipped in liquid nitrogen (LN/LN) or stored in LN and shipped on dry ice (LN/DI) or stored at -70°C for 3 to 12 weeks and shipped on DI (70/DI 3 to 12); and to assess the effect of donor HIV infection status on the interaction between storage/shipment and the outcome measures. PBMC from 12 HIV-infected and 12 uninfected donors showed that LN/LN conferred higher viability and recovery than LN/DI or 70/DI 3, 6, 9 or 12. LN/DI PBMC had higher viability than any 70/DI PBMC. The PBMC viability and recovery linearly decreased with the duration of storage at -70°C from 3 to 12 weeks. This effect was more pronounced in samples from HIV-infected than uninfected donors. Results of ELISPOT assays using CMV pp65, CEF and Candida albicans antigens were qualitatively and quantitatively similar across LN/LN, LN/DI and 70/DI 3. However, ELISPOT values significantly decreased with the duration of storage at -70°C both in HIV-infected and uninfected donors. ELISPOT results also decreased with PBMC viability <70%.

Continuous improvement in the immune system of HIV-infected children on prolonged antiretroviral therapy

BACKGROUND

The goal of HAART is to promote reconstitution of CD4+ T cells and other immune responses. We evaluated the extent and the kinetics of immune reconstitution in HIV-infected children over 144 weeks of successful HAART.

METHODS

Thirty-seven children receiving their first HAART regimen had plasma HIV RNA; T cells and subpopulations; T-cell rearrangement excision circles (TREC) DNA; candida, HIVCD4 and HIVCD8 enzyme-linked immunospot measured at regular intervals.

RESULTS

Plasma HIV RNA became undetectable in 81% of patients at 24 weeks and remained undetectable in 77% at 144 weeks. In contrast, CD4+% continuously increased. Distribution of T-cell subpopulations changed rapidly during the first 48 weeks of HAART and more slowly thereafter. At 144 weeks, total, naive and activated CD4+% and naive CD8+% of HIV-infected children were not significantly different from those of healthy age-matched controls, whereas total and activated CD8+% remained elevated. CD4 and CD8 TREC content increased only during the first 48 weeks of HAART. They positively correlated with each other and with total CD4+%, naive CD4+% and naive CD8+%. Candida and HIVCD4 enzyme-linked immunospot increased over time reaching peak values at 48 weeks and 144 weeks, respectively. HIVCD8 enzyme-linked immunospot decreased in magnitude over 144 weeks of HAART but retained its breadth. Baseline CD4+% positively correlated with CD4+% and with functional immune reconstitution at week 144, whereas baseline TREC correlated with TREC at week 144.

CONCLUSION

HIV-infected children acquired normal distribution of CD4 T cells and other subpopulations and recovered CD4-mediated HIV immunity after 144 weeks of HAART.

Ex vivo effect of estrogen and progesterone compared with dexamethasone on cell-mediated immunity of HIV-infected and uninfected subjects

To define the effect of estrogen and progesterone concentrations achieved during hormonal contraceptive therapy (HCT) on cell-mediated immunity (CMI) of HIV-infected and uninfected subjects, peripheral blood mononuclear cells (PBMCs) from varicella-zoster virus (VZV)-seropositive individuals were treated with 0.1 ng/mL of estradiol, 33 ng/mL of norgestrel, and 13 ng/mL of dexamethasone and tested for VZV CMI. Estrogen and progesterone decreased VZV lymphocyte proliferation and T helper (Th) 1/inflammatory cytokine secretion, albeit less than dexamethasone. Progesterone decreased the expression of CD69 activation marker on CD8 and CD14 cells and increased the expression of Fas ligand (CD178) on CD14 monocytes, suggesting that induction of apoptosis may contribute to the inhibitory effect of this hormone. Cytokine production of separated CD4, CD8, and CD14 cells confirmed the effect of progesterone on all 3 cellular types, whereas the effect of estrogen was restricted to CD14 monocytes. The estrogen- and progesterone-mediated inhibition of Th1/inflammatory cytokines was greater in HIV-infected subjects (35% decrease for both hormones) compared with uninfected subjects (12% and 19% for estrogen and progesterone, respectively), whereas the effect on proliferation and PBMC phenotype did not differ by HIV status. Overall, HCT concentrations of estrogen and progesterone downregulated ex vivo VZV CMI of HIV-infected and uninfected subjects.

Regulatory T cells generated during cytomegalovirus in vitro stimulation of mononuclear cells from HIV-infected individuals on HAART correlate with decreased lymphocyte proliferation

HIV-infected patients fail to fully recover cell-mediated immunity despite HAART. To identify regulatory factors, we studied the phenotype and function of in vitro cytomegalovirus (CMV)-stimulated T cells from HAART recipients. CFSE-measured proliferation showed CD4+ and CD8+ cells dividing in CMV-stimulated cultures. Compared with healthy controls, CMV-stimulated lymphocytes from HAART recipients had lower 3H-thymidine incorporation; lower IFNgamma and TNFalpha production; higher CD4+ CD27- CD28- and CD8+ CD27- CD28- frequencies; lower CD4+ CD25hi; and higher FoxP3 expression in CD8+ CD25hi cells. CMV-specific proliferation correlated with higher IFNgamma, TNFalpha and IL10 levels and higher CD4+ perforin+ and CD8+ perforin+ frequencies. Decreased proliferation correlated with higher CD4+ CD27- CD28- frequencies and TGFbeta1 production, which also correlated with each other. Anti-TGFbeta1 neutralizing antibodies restored CMV-specific proliferation in a dose-dependent fashion. In HIV-infected subjects, decreased proliferation correlated with higher CMV-stimulated CD8+ CD25hi frequencies and their FoxP3 expression. These data indicate that FoxP3- and TGFbeta1-expressing regulatory T cells contribute to decreased immunity in HAART recipients.

Cytomegalovirus-specific cell-mediated immunity in HIV-infected children on HAART

The objectives of this study were to define the magnitude, time course, and virologic and immunologic correlates of HAART-associated reconstitution of cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) in pediatric HAART recipients. Thirty-five HIV-infected CMV-seropositive subjects < or = 22 years on or about to receive HAART had CMV-CMI measured by responder cell frequency (RCF) and interferon-gamma (IFN-gamma) secretion over 3 years. RCF was detected in 33, 52, 38, and 28% before HAART and at years 1, 2, and > or = 3, respectively. Corresponding percentages for IFN-gamma were 100, 85, 100, and 38%. Neither RCF nor IFN-gamma was significantly associated with CD4% before or after HAART initiation. Lower HIV replication was associated with a higher proportion of subjects with positive RCF, but not IFN-gamma. There were no clinical CMV manifestations during the study. HIV-infected children did not demonstrate a significant increase in CMV-CMI with longer HAART duration, which suggests that CMV immunereconstitution involves more complex immunologic and virologic interactions than previously anticipated.

Cytomegalovirus infection in the era of HAART: fewer reactivations and more immunity

The incidence of cytomegalovirus (CMV) disease, once the most common and highly feared viral complication of AIDS, has dramatically decreased with the advent of highly active antiretroviral therapy (HAART). HAART-associated changes in the epidemiology of CMV disease resulted from the increase in CMV-specific immune responses coupled with the decrease in CMV reactivation. However, CMV disease continues to afflict HIV-infected patients on HAART when CD4+ cell counts fail to rise above 100 cells/mm(3) and when reconstitution of normal CMV-specific immune responses does not occur. The latter scenario may lead to recurrent or de novo CMV end-organ disease, or to the recently described CMV immune recovery vitritis. HAART-associated immune reconstitution offers unique opportunities to investigate the virological and immunological correlates of protection against CMV disease. Although the full extent of CMV-specific immune reconstitution has not been defined thus far, CMV-specific interferon-gamma production has been shown to be significantly associated with protection against CMV reactivation and recurrent disease.