Lack of differences in nef alleles among HIV-infected asymptomatic long-term survivors and those who progressed to disease

An integrative genomic analysis of transcriptional profiles identifies characteristic genes and patterns in HIV-infected long-term non-progressors and elite controllers

Background

Despite that most HIV-infected individuals experience progressive CD4+ T cell loss and develop AIDS, a minority of HIV-infected individuals remain asymptomatic and maintain high level CD4+ T cell counts several years after seroconversion. Efforts have been made to understand the determinants of the nonprogressive status, exemplified by the clinical course of elite controllers (ECs) who maintain an undetectable viremia and viremic nonprogressors (VNPs) who have a normal CD4+ count in spite of circulating viral load. However, the intrinsic mechanism underlying nonprogression remained elusive. In this study, we performed an integrative analysis of transcriptional profiles to pinpoint the underlying mechanism for a naturally occurring viral control.

Methods

Three microarray datasets, reporting mRNA expression of the LTNPs or ECs in HIV-infected patients, were retrieved from Gene Expression Ominbus (GEO) or Arrayexpress databases. These datasets, profiled on the same type of microarray chip, were selected and merged by a bioinformatic approach to build a meta-analysis derived transcriptome (MADNT). In addition, we investigated the different transcriptional pathways and potential biomarkers in CD4+ and CD8+ cells in ECs and whole blood in VNPs compared to HIV progressors. The combined transcriptome and each subgroup was subject to gene set enrichment analysis and weighted co-expression network analysis to search potential transcription patterns related to the non-progressive status.

Results

30 up-regulated genes and 83 down-regulated genes were identified in lymphocytes from integrative meta-analysis of expression data. The interferon response and innate immune activation was reduced in both CD4+ and CD8+ T cells from ECs. Several characteristic genes including CMPK1, CBX7, EIF3L, EIF4A and ZNF395 were indicated to be highly correlated with viremic control. Besides that, we indicated that the reduction of ribosome components and blockade of translation facilitated AIDS disease progression. Most interestingly, among VNPs who have a relatively high viral load, we detected a two gene-interaction networks which showed a strong correlation to immune control even with a rigorous statistical threshold (p value = 2−e4 and p value = 0.004, respectively) by WGCNA.

Conclusions

We have identified differentially expressed genes and transcriptional patterns in ECs and VNPs compared to normal chronic HIV-infected individuals. Our study provides new insights into the pathogenesis of HIV and AIDS and clues for the therapeutic strategies for anti-retroviral administration.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1777-7) contains supplementary material, which is available to authorized users.

Comparison of transcriptional profiles between CD4+ and CD8+ T cells in HIV type 1-infected patients

The CD4+/CD8+ T cell ratio is altered when HIV-1 infects the human immune system. However, the exact mechanisms of how CD4+ and CD8+T cells participate in HIV infection are still unknown. This study used bioinformatics methods to compare the transcriptional profiles between CD4+ and CD8+ T cells in HIV-1-infected patients in order to explore the potential molecular mechanisms of CD4+ and CD8+ T cells in HIV-1 infection. We found that expression patterns of differentially expressed genes (DEG) in CD4+T cells were dramatically different from those in CD8+ T cells. We also constructed protein-protein interaction (PPI) networks to extract functional modules at each stage, and found that some of the important genes such as BRCA1 were central hubs of the modules. Finally, we applied functional annotation to the modules and found that CD4+/CD8+ T cells played critical roles in regulating the cell cycle and other cellular pathways. Thus, this study would greatly further our understanding of the roles of T cells in HIV infection, and provide potential clues for developing AIDS vaccines in the future.

Meta-analysis to test the association of HIV-1 nef amino acid differences and deletions with disease progression

Previous relatively small studies have associated particular amino acid replacements and deletions in the HIV-1 nef gene with differences in the rate of HIV disease progression. We tested more rigorously whether particular nef amino acid differences and deletions are associated with HIV disease progression. Amino acid replacements and deletions in patients' consensus sequences were investigated for 153 progressor (P), 615 long-term nonprogressor (LTNP), and 2,311 unknown progressor sequences from 582 subtype B HIV-infected patients. LTNPs had more defective nefs (interrupted by frameshifts or stop codons), but on a per-patient basis there was no excess of LTNP patients with one or more defective nef sequences compared to the Ps (P = 0.47). The high frequency of amino acid replacement at residues S(8), V(10), I(11), A(15), V(85), V(133), N(157), S(163), V(168), D(174), R(178), E(182), and R(188) in LTNPs was also seen in permuted datasets, implying that these are simply rapidly evolving residues. Permutation testing revealed that residues showing the greatest excess over expectation (A(15), V(85), N(157), S(163), V(168), D(174), R(178), and R(188)) were not significant (P = 0.77). Exploratory analysis suggested a hypothetical excess of frameshifting in the regions (9)SVIG and (118)QGYF among LTNPs. The regions V(10) and (152)KVEEA of nef were commonly deleted in LTNPs. However, permutation testing indicated that none of the regions displayed significantly excessive deletion in LTNPs. In conclusion, meta-analysis of HIV-1 nef sequences provides no clear evidence of whether defective nef sequences or particular regions of the protein play a significant role in disease progression.

Evolution of nef variants in gut associated lymphoid tissue of rhesus macaques during primary simian immunodeficiency virus infection

We utilized the simian immunodeficiency virus model of AIDS to examine evolution of nef gene in gut-associated lymphoid tissue (GALT) during primary and early asymptomatic stages of infection. Macaques were infected with a cloned virus, SIVmac239/nef-stop harboring a premature stop codon in the nef gene. Restoration of the nef open reading frame occurred in GALT early at 3 days post-infection. Analysis of nef sequences by phylogenetic tools showed that evolution of nef was neutral thereafter, as evidenced by the ratio of synonymous to nonsynonymous substitutions, a star pattern in unrooted trees and distribution of amino acid replacements fitting a simple Poisson process. Two regions encoding for a nuclear localization signal and a CTL epitope were conserved. Thus, GALT was a site for strong positive selection of functional nef during initial stages of infection. However, evolution of the nef gene thereafter was neutral during early asymptomatic stage of infection.

Natural variation of the nef gene in human immunodeficiency virus type 2 infections in Portugal

Human immunodeficiency virus type 2 (HIV-2) infections cause severe immunodeficiency in humans, although HIV-2 is associated frequently with reduced virulence and pathogenicity compared to HIV-1. Genetic determinants that play a role in HIV pathogenesis are relatively poorly understood but nef has been implicated in inducing a more pathogenic phenotype in vivo. However, relatively little is known about the role of nef in HIV-2 pathogenesis. To address this, the genetic composition of 44 nef alleles from 37 HIV-2-infected individuals in Portugal, encompassing a wide spectrum of disease associations, CD4 counts and virus load, has been assessed. All nef alleles were subtype A, with no evidence of gross deletions, truncations or disruptions in the nef-encoding sequence; all were full-length and intact. HIV-2 long terminal repeat sequences were conserved and also indicated subtype A infections. Detailed analysis of motifs that mediate nef function in HIV-1 and simian immunodeficiency virus, such as CD4 downregulation and putative SH2/SH3 interactions, revealed significant natural variation. In particular, the central P(104)xxPLR motif exhibited wide interpatient variation, ranging from an HIV-1-like tetra-proline structure (PxxP)(3) to a disrupted minimal core motif (P(104)xxQLR). The P(107)-->Q substitution was associated with an asymptomatic phenotype (Fisher's exact test, P=0.026) and low virus loads. These data indicate that discrete differences in the nef gene sequence rather than gross structural changes are more likely to play a role in HIV-2 pathogenesis mediated via specific functional interactions.

No association of HIV-1 envelope (C2-V3-C3) sequence pattern with long-term nonprogression

We previously identified a group of 10 long-term nonprogressors (LTNP) with HIV-1 infection. In this study, we have sequenced the envelope gene (C2-V3-C3) from the 10 LTNPs and from a control group of 9 people with rapidly progressing infection (RPI). The 19 individuals' CCR5 genotype and virus phenotype (i.e., syncytium-inducing/non-syncytium-inducing [SI/NSI]) were obtained from a previous study. A phylogenetic tree was constructed containing the 19 envelope sequences together with 42 local control env sequences obtained from other studies. Analysis of the phylogenetic tree did not reveal any relation between the envelope gene (C2-V3-C3) from LTNPs versus RPIs. When data from the CCR5 genotype and the virus phenotype were assembled in the phylogenetic tree, no significant clustering was observed. From alignment of the protein sequences, we found a possible N-glycan in position aa294 in env that was conserved in only 1 of 10 LTNPs; however, it was conserved in 6 of 9 RPIs. Our study could not demonstrate any association between LTNPs and the sequenced envelope gene segment (C2-V3-C3). This lack of association could be due to the relatively small sample size of the data set. Nor did we find any relation between the CCR5 genotype or the SI/NSI phenotype with the sequenced envelope genes from the 19 participants. The possible N-glycan position we have described is an interesting observation that may require further investigation.