Paediatric non-progression following grandmother-to-child HIV transmission

Higher HIV-1 evolutionary rate is associated with cytotoxic T lymphocyte escape mutations in infants

Escape from cytotoxic T lymphocyte (CTL) responses toward HIV-1 Gag and Nef has been associated with reduced control of HIV-1 replication in adults. However, less is known about CTL-driven immune selection in infants as longitudinal studies of infants are limited. Here, 1,210 gag and 1,264 nef sequences longitudinally collected within 15 months after birth from 14 HIV-1 perinatally infected infants and their mothers were analyzed. The number of transmitted founder (T/F) viruses and associations between virus evolution, selection, CTL escape, and disease progression were determined. The analyses indicated that a paraphyletic-monophyletic relationship between the mother-infant sequences was common (80%), and that the HIV-1 infection was established by a single T/F virus in 10 of the 12 analyzed infants (83%). Furthermore, most HIV-1 CTL escape mutations among infants were transmitted from the mothers and did not revert during the first year of infection. Still, immune-driven selection was observed at approximately 3 months after HIV-1 infection in infants. Moreover, virus populations with CTL escape mutations in gag evolved faster than those without, independently of disease progression rate. These findings expand the current knowledge of HIV-1 transmission, evolution, and CTL escape in infant HIV-1 infection and are relevant for the development of immune-directed interventions in infants.IMPORTANCEDespite increased coverage in antiretroviral therapy for the prevention of perinatal transmission, paediatric HIV-1 infection remains a significant public health concern, especially in areas of high HIV-1 prevalence. Understanding HIV-1 transmission and the subsequent virus adaptation from the mother to the infant's host environment, as well as the viral factors that affect disease outcome, is important for the development of early immune-directed interventions for infants. This study advances our understanding of vertical HIV-1 transmission, and how infant immune selection pressure is shaping the intra-host evolutionary dynamics of HIV-1.

Impact of early antiretroviral therapy, early life immunity and immune sex differences on HIV disease and posttreatment control in children

PURPOSE OF REVIEW

To review recent insights into the factors affecting HIV disease progression in children living with HIV, contrasting outcomes: following early ART initiation with those in natural, antiretroviral therapy (ART)-naive infection; in children versus adults; and in female individuals versus male individuals.

RECENT FINDINGS

Early life immune polarization and several factors associated with mother-to-child transmission of HIV result in an ineffective HIV-specific CD8+ T-cell response and rapid disease progression in most children living with HIV. However, the same factors result in low immune activation and antiviral efficacy mediated mainly through natural killer cell responses in children and are central features of posttreatment control. By contrast, rapid activation of the immune system and generation of a broad HIV-specific CD8+ T-cell response in adults, especially in the context of 'protective' HLA class I molecules, are associated with superior disease outcomes in ART-naive infection but not with posttreatment control. The higher levels of immune activation in female individuals versus male individuals from intrauterine life onwards increase HIV infection susceptibility in females in utero and may favour ART-naive disease outcomes rather than posttreatment control.

SUMMARY

Early-life immunity and factors associated with mother-to-child transmission typically result in rapid HIV disease progression in ART-naive infection but favour posttreatment control in children following early ART initiation.

TRIM22 genotype is not associated with markers of disease progression in children with HIV-1 infection

OBJECTIVE

Untreated perinatal HIV-1 infection is often associated with rapid disease progression in children with HIV (CWH), characterized by high viral loads and early mortality. TRIM22 is a host restriction factor, which directly inhibits HIV-1 transcription, and its genotype variation is associated with disease progression in adults. We tested the hypothesis that TRIM22 genotype is associated with disease progression in CWH.

DESIGN

ART-naive CWH, aged 6-16 years, were recruited from primary care clinics in Harare, Zimbabwe. We performed a candidate gene association study of TRIM22 genotype and haplotypes with markers of disease progression and indicators of advanced disease.

METHODS

TRIM22 exons three and four were sequenced by Sanger sequencing and single nucleotide polymorphisms were associated with markers of disease progression (CD4+ T-cell count and HIV viral load) and clinical indicators of advanced HIV disease (presence of stunting and chronic diarrhoea). Associations were tested using multivariate linear and logistic regression models.

RESULTS

A total of 241 children, median age 11.4 years, 50% female, were included. Stunting was present in 16% of participants. Five SNPs were analyzed including rs7935564, rs2291842, rs78484876, rs1063303 and rs61735273. The median CD4+ count was 342 (IQR: 195-533) cells/μl and median HIV-1 viral load 34 199 (IQR: 8211-90 662) IU/ml. TRIM22 genotype and haplotypes were not associated with CD4+ T-cell count, HIV-1 viral load, stunting or chronic diarrhoea.

CONCLUSION

TRIM22 genotype was not associated with markers of HIV disease progression markers or advanced disease in CWH.

Two distinct mechanisms leading to loss of virological control in the rare group of antiretroviral therapy-naïve, transiently aviraemic children living with HIV

HIV-specific CD8+ T-cells play a central role in immune control of adult HIV, but their contribution in paediatric infection is less well-characterised. Previously, we identified a group of ART-naïve children with persistently undetectable plasma viraemia, termed 'elite controllers', and a second group who achieved aviraemia only transiently. To investigate the mechanisms of failure to maintain aviraemia, we characterized in three transient aviraemics (TAs), each of whom expressed the disease-protective HLA-B*81:01, longitudinal HIV-specific T-cell activity and viral sequences. In two TAs, a CD8+ T-cell response targeting the immunodominant epitope TPQDLNTML ('Gag-TL9') was associated with viral control, followed by viral rebound and the emergence of escape variants with lower replicative capacity. Both TAs mounted variant-specific responses, but only at low functional avidity, resulting in immunological progression. By contrast, in TA-3, intermittent viraemic episodes followed aviraemia without virus escape or a diminished CD4+ T-cell count. High quality and magnitude of the CD8+ T-cell response was associated with aviraemia. We therefore identify two distinct mechanisms of loss of viral control. In one scenario, CD8+ T-cell responses initially cornered low replicative capacity escape variants, but with insufficient avidity to prevent viraemia and disease progression. In the other, loss of viral control was associated neither with virus escape nor progression, but with a decrease in the quality of the CD8+ T-cell response, followed by recovery of viral control in association with improved antiviral response. These data suggest the potential for a consistently strong and polyfunctional antiviral response to achieve long-term viral control without escape. IMPORTANCE Very early initiation of antiretroviral therapy (ART) in paediatric HIV infection offers a unique opportunity to limit the size and diversity of the viral reservoir. However, only exceptionally is ART alone sufficient to achieve remission. Additional interventions are therefore required that likely include contributions from host immunity. The HIV-specific T-cell response plays a central role in immune control of adult HIV, often mediated through protective alleles such as HLA-B*57/58:01/81:01. However, due to the tolerogenic and type 2 biased immune response in early life, HLA-I-mediated immune suppression of viraemia is seldom observed in children. We describe a rare group of HLA-B*81:01-positive, ART-naïve children who achieved aviraemia, albeit only transiently, and investigate the role of the CD8+ T-cell response in the establishment and loss of viral control. We identify a mechanism by which the HIV-specific response can achieve viraemic control without viral escape, that can be explored in strategies to achieve remission.

Viral and Cellular factors leading to the Loss of CD4 Homeostasis in HIV-1 Viremic Nonprogressors

Human immunodeficiency virus type 1 (HIV-1) viremic nonprogressors (VNPs) represent a very rare HIV-1 extreme phenotype. VNPs are characterized by persistent high plasma viremia and maintenance of CD4⁺ T-cell counts in the absence of treatment. However, the causes of nonpathogenic HIV-1 infection in VNPs remain elusive. Here, we identified for the first time two VNPs who experienced the loss of CD4⁺ homeostasis (LoH) after more than 13 years. We characterized in deep detail viral and host factors associated with the LoH and compared with standard VNPs and healthy controls. The viral factors determined included HIV-1 coreceptor usage and replicative capacity. Changes in CD4⁺ and CD8⁺ T-cell activation, maturational phenotype, and expression of CCR5 and CXCR6 in CD4⁺ T-cells were also evaluated as host-related factors. Consistently, we determined a switch in HIV-1 coreceptor use to CXCR4 concomitant with an increase in replicative capacity at the LoH for the two VNPs. Moreover, we delineated an increase in the frequency of HLA-DR+CD38⁺ CD4⁺ and CD8⁺ T cells and traced the augment of naive T-cells upon polyclonal activation with LoH. Remarkably, very low and stable levels of CCR5 and CXCR6 expression in CD4⁺ T-cells were measured over time. Overall, our results demonstrated HIV-1 evolution toward highly pathogenic CXCR4 strains in the context of very limited and stable expression of CCR5 and CXCR6 in CD4⁺ T cells as potential drivers of LoH in VNPs. These data bring novel insights into the correlates of nonpathogenic HIV-1 infection.

IMPORTANCE The mechanism behind nonpathogenic human immunodeficiency virus type 1 (HIV-1) infection remains poorly understood, mainly because of the very low frequency of viremic nonprogressors (VNPs). Here, we report two cases of VNPs who experienced the loss of CD4⁺ T-cell homeostasis (LoH) after more than 13 years of HIV-1 infection. The deep characterization of viral and host factors supports the contribution of viral and host factors to the LoH in VNPs. Thus, HIV-1 evolution toward highly replicative CXCR4 strains together with changes in T-cell activation and maturational phenotypes were found. Moreover, we measured very low and stable levels of CCR5 and CXCR6 in CD4⁺ T-cells over time. These findings support viral evolution toward X4 strains limited by coreceptor expression to control HIV-1 pathogenesis and demonstrate the potential of host-dependent factors, yet to be fully elucidated in VNPs, to control HIV-1 pathogenesis.

Impact of HLA-B*52:01-Driven Escape Mutations on Viral Replicative Capacity

HLA-B*52:01 is strongly associated with protection against HIV disease progression. However, the mechanisms of HLA-B*52:01-mediated immune control have not been well studied. We here describe a cohort with a majority of HIV C-clade-infected individuals from Delhi, India, where HLA-B*52:01 is highly prevalent (phenotypic frequency, 22.5%). Consistent with studies of other cohorts, expression of HLA-B*52:01 was associated with high absolute CD4 counts and therefore a lack of HIV disease progression. We here examined the impact of HLA-B*52:01-associated viral polymorphisms within the immunodominant C clade Gag epitope RMTSPVSI (here, RI8; Gag residues 275 to 282) on viral replicative capacity (VRC) since HLA-mediated reduction in VRC is a central mechanism implicated in HLA-associated control of HIV. We observed in HLA-B*52:01-positive individuals a higher frequency of V280T, V280S, and V280A variants within RI8 (P = 0.0001). Each of these variants reduced viral replicative capacity in C clade viruses, particularly the V280A variant (P < 0.0001 in both the C clade consensus and in the Indian study cohort consensus p24 Gag backbone), which was also associated with significantly higher absolute CD4 counts in the donors (median, 941.5 cells/mm³; P = 0.004). A second HLA-B*52:01-associated mutation, K286R, flanking HLA-B*52:01-RI8, was also analyzed. Although selected in HLA-B*52:01-positive subjects often in combination with the V280X variants, this mutation did not act as a compensatory mutant but, indeed, further reduced VRC. These data are therefore consistent with previous work showing that HLA-B molecules that are associated with immune control of HIV principally target conserved epitopes within the capsid protein, escape from which results in a significant reduction in VRC.IMPORTANCE Few studies have addressed the mechanisms of immune control in HIV-infected subjects in India, where an estimated 2.7 million people are living with HIV. We focus here on a study cohort in Delhi on one of the most prevalent HLA-B alleles, HLA-B*52:01, present in 22.5% of infected individuals. HLA-B*52:01 has consistently been shown in other cohorts to be associated with protection against HIV disease progression, but studies have been limited by the low prevalence of this allele in North America and Europe. Among the C-clade-infected individuals, we show that HLA-B*52:01 is the most protective of all the HLA-B alleles expressed in the Indian cohort and is associated with the highest absolute CD4 counts. Further, we show that the mechanism by which HLA-B*52:01 mediates immune protection is, at least in part, related to the inability of HIV to evade the HLA-B*52:01-restricted p24 Gag-specific CD8⁺ T-cell response without incurring a significant loss to viral replicative capacity.

Rapid HIV disease progression following superinfection in an HLA-B*27:05/B*57:01-positive transmission recipient

Background

The factors determining differential HIV disease outcome among individuals expressing protective HLA alleles such as HLA-B*27:05 and HLA-B*57:01 remain unknown. We here analyse two HIV-infected subjects expressing both HLA-B*27:05 and HLA-B*57:01. One subject maintained low-to-undetectable viral loads for more than a decade of follow up. The other progressed to AIDS in < 3 years.

Results

The rapid progressor was the recipient within a known transmission pair, enabling virus sequences to be tracked from transmission. Progression was associated with a 12% Gag sequence change and 26% Nef sequence change at the amino acid level within 2 years. Although next generation sequencing from early timepoints indicated that multiple CD8+ cytotoxic T lymphocyte (CTL) escape mutants were being selected prior to superinfection, < 4% of the amino acid changes arising from superinfection could be ascribed to CTL escape. Analysis of an HLA-B*27:05/B*57:01 non-progressor, in contrast, demonstrated minimal virus sequence diversification (1.1% Gag amino acid sequence change over 10 years), and dominant HIV-specific CTL responses previously shown to be effective in control of viraemia were maintained. Clonal sequencing demonstrated that escape variants were generated within the non-progressor, but in many cases were not selected. In the rapid progressor, progression occurred despite substantial reductions in viral replicative capacity (VRC), and non-progression in the elite controller despite relatively high VRC.

Conclusions

These data are consistent with previous studies demonstrating rapid progression in association with superinfection and that rapid disease progression can occur despite the relatively the low VRC that is typically observed in the setting of multiple CTL escape mutants.

Electronic supplementary material

The online version of this article (10.1186/s12977-018-0390-9) contains supplementary material, which is available to authorized users.

Role of HIV-specific CD8+ T cells in pediatric HIV cure strategies after widespread early viral escape

Recent studies have suggested greater HIV cure potential among infected children than adults. A major obstacle to HIV eradication in adults is that the viral reservoir is largely comprised of HIV-specific cytotoxic T lymphocyte (CTL) escape variants. We here evaluate the potential for CTL in HIV-infected slow-progressor children to play an effective role in "shock-and-kill" cure strategies. Two distinct subgroups of children were identified on the basis of viral load. Unexpectedly, in both groups, as in adults, HIV-specific CTL drove the selection of escape variants across a range of epitopes within the first weeks of infection. However, in HIV-infected children, but not adults, de novo autologous variant-specific CTL responses were generated, enabling the pediatric immune system to "corner" the virus. Thus, even when escape variants are selected in early infection, the capacity in children to generate variant-specific anti-HIV CTL responses maintains the potential for CTL to contribute to effective shock-and-kill cure strategies in pediatric HIV infection.