Harnessing natural killer cells to target HIV-1 persistence

PURPOSE OF REVIEW

The purpose of this article is to review recent advances in the role of natural killer (NK) cells in approaches aimed at reducing the latent HIV-1 reservoir.

RECENT FINDINGS

Multiple approaches to eliminate cells harboring latent HIV-1 are being explored, but have been met with limited success so far. Recent studies have highlighted the role of NK cells and their potential in HIV-1 cure efforts. Anti-HIV-1 NK cell function can be optimized by enhancing NK cell activation, antibody dependent cellular cytotoxicity, reversing inhibition of NK cells as well as by employing immunotherapeutic complexes to enable HIV-1 specificity of NK cells. While NK cells alone do not eliminate the HIV-1 reservoir, boosting NK cell function might complement other strategies involving T cell and B cell immunity towards an HIV-1 functional cure.

SUMMARY

Numerous studies focusing on targeting latently HIV-1-infected cells have emphasized a potential role of NK cells in these strategies. Our review highlights recent advances in harnessing NK cells in conjunction with latency reversal agents and other immunomodulatory therapeutics to target HIV-1 persistence.

A VRC13-like bNAb response is associated with complex escape pathways in HIV-1 envelope

The rational design of HIV-1 immunogens to trigger the development of broadly neutralizing antibodies (bNAbs) requires understanding the viral evolutionary pathways influencing this process. An acute HIV-1-infected individual exhibiting >50% plasma neutralization breadth developed neutralizing antibody specificities against the CD4-binding site (CD4bs) and V1V2 regions of Env gp120. Comparison of pseudoviruses derived from early and late autologous env sequences demonstrated the development of >2 log resistance to VRC13 but not to other CD4bs-specific bNAbs. Mapping studies indicated that the V3 and CD4-binding loops of Env gp120 contributed significantly to developing resistance to the autologous neutralizing response and that the CD4-binding loop (CD4BL) specifically was responsible for the developing resistance to VRC13. Tracking viral evolution during the development of this cross-neutralizing CD4bs response identified amino acid substitutions arising at only 4 of 11 known VRC13 contact sites (K282, T283, K421, and V471). However, each of these mutations was external to the V3 and CD4BL regions conferring resistance to VRC13 and was transient in nature. Rather, complete resistance to VRC13 was achieved through the cooperative expression of a cluster of single amino acid changes within and immediately adjacent to the CD4BL, including a T359I substitution, exchange of a potential N-linked glycosylation (PNLG) site to residue S362 from N363, and a P369L substitution. Collectively, our data characterize complex HIV-1 env evolution in an individual developing resistance to a VRC13-like neutralizing antibody response and identify novel VRC13-associated escape mutations that may be important to inducing VRC13-like bNAbs for lineage-based immunogens.IMPORTANCEThe pursuit of eliciting broadly neutralizing antibodies (bNAbs) through vaccination and their use as therapeutics remains a significant focus in the effort to eradicate HIV-1. Key to our understanding of this approach is a more extensive understanding of bNAb contact sites and susceptible escape mutations in HIV-1 envelope (env). We identified a broad neutralizer exhibiting VRC13-like responses, a non-germline restricted class of CD4-binding site antibody distinct from the well-studied VRC01-class. Through longitudinal envelope sequencing and Env-pseudotyped neutralization assays, we characterized a complex escape pathway requiring the cooperative evolution of four amino acid changes to confer complete resistance to VRC13. This suggests that VRC13-class bNAbs may be refractory to rapid escape and attractive for therapeutic applications. Furthermore, the identification of longitudinal viral changes concomitant with the development of neutralization breadth may help identify the viral intermediates needed for the maturation of VRC13-like responses and the design of lineage-based immunogens.

HLA-DP on Epithelial Cells Enables Tissue Damage by NKp44+ Natural Killer Cells in Ulcerative Colitis

BACKGROUND & AIMS

Ulcerative colitis (UC) is characterized by severe inflammation and destruction of the intestinal epithelium, and is associated with specific risk single nucleotide polymorphisms in HLA class II. Given the recently discovered interactions between subsets of HLA-DP molecules and the activating natural killer (NK) cell receptor NKp44, genetic associations of UC and HLA-DP haplotypes and their functional implications were investigated.

METHODS

HLA-DP haplotype and UC risk association analyses were performed (UC: n = 13,927; control: n = 26,764). Expression levels of HLA-DP on intestinal epithelial cells (IECs) in individuals with and without UC were quantified. Human intestinal 3-dimensional (3D) organoid cocultures with human NK cells were used to determine functional consequences of interactions between HLA-DP and NKp44.

RESULTS

These studies identified HLA-DPA1∗01:03-DPB1∗04:01 (HLA-DP401) as a risk haplotype and HLA-DPA1∗01:03-DPB1∗03:01 (HLA-DP301) as a protective haplotype for UC in European populations. HLA-DP expression was significantly higher on IECs of individuals with UC compared with controls. IECs in human intestinal 3D organoids derived from HLA-DP401pos individuals showed significantly stronger binding of NKp44 compared with HLA-DP301pos IECs. HLA-DP401pos IECs in organoids triggered increased degranulation and tumor necrosis factor production by NKp44+ NK cells in cocultures, resulting in enhanced epithelial cell death compared with HLA-DP301pos organoids. Blocking of HLA-DP401-NKp44 interactions (anti-NKp44) abrogated NK cell activity in cocultures.

CONCLUSIONS

We identified an UC risk HLA-DP haplotype that engages NKp44 and activates NKp44+ NK cells, mediating damage to intestinal epithelial cells in an HLA-DP haplotype-dependent manner. The molecular interaction between NKp44 and HLA-DP401 in UC can be targeted by therapeutic interventions to reduce NKp44+ NK cell-mediated destruction of the intestinal epithelium in UC.

Gp41-targeted antibodies restore infectivity of a fusion-deficient HIV-1 envelope glycoprotein

The HIV-1 envelope glycoprotein (Env) mediates viral entry via conformational changes associated with binding the cell surface receptor (CD4) and coreceptor (CCR5/CXCR4), resulting in subsequent fusion of the viral and cellular membranes. While the gp120 Env surface subunit has been extensively studied for its role in viral entry and evasion of the host immune response, the gp41 transmembrane glycoprotein and its role in natural infection are less well characterized. Here, we identified a primary HIV-1 Env variant that consistently supports >300% increased viral infectivity in the presence of autologous or heterologous HIV-positive plasma. However, in the absence of HIV-positive plasma, viruses with this Env exhibited reduced infectivity that was not due to decreased CD4 binding. Using Env chimeras and sequence analysis, we mapped this phenotype to a change Q563R, in the gp41 heptad repeat 1 (HR1) region. We demonstrate that Q563R reduces viral infection by disrupting formation of the gp41 six-helix bundle required for virus-cell membrane fusion. Intriguingly, antibodies that bind cluster I epitopes on gp41 overcome this inhibitory effect, restoring infectivity to wild-type levels. We further demonstrate that the Q563R change increases HIV-1 sensitivity to broadly neutralizing antibodies (bNAbs) targeting the gp41 membrane-proximal external region (MPER). In summary, we identify an HIV-1 Env variant with impaired infectivity whose Env functionality is restored through the binding of host antibodies. These data contribute to our understanding of gp41 residues involved in membrane fusion and identify a mechanism by which host factors can alleviate a viral defect.

Recent Advances in Psoriatic Arthritis from Obscurity to Prominence

Psoriatic arthritis is a fascinating inflammatory arthritis. Till recently it did not generate interest for lack of understanding of its immunopathology, and lack of effective treatment. This has changed. PsA is now one of the hot topics - all due to elucidation of genetic susceptibility associations, immunopathogenesis and availability of effective therapy. In this communication we provide an overview of these aspects of psoriatic arthritis.

AAV-expressed eCD4-Ig provides durable protection from multiple SHIV challenges

Long-term in vivo expression of a broad and potent entry inhibitor could circumvent the need for a conventional vaccine for HIV-1. Adeno-associated virus (AAV) vectors can stably express HIV-1 broadly neutralizing antibodies (bNAbs). However, even the best bNAbs neutralize 10-50% of HIV-1 isolates inefficiently (80% inhibitory concentration (IC80) > 5 μg ml(-1)), suggesting that high concentrations of these antibodies would be necessary to achieve general protection. Here we show that eCD4-Ig, a fusion of CD4-Ig with a small CCR5-mimetic sulfopeptide, binds avidly and cooperatively to the HIV-1 envelope glycoprotein (Env) and is more potent than the best bNAbs (geometric mean half-maximum inhibitory concentration (IC50) < 0.05 μg ml(-1)). Because eCD4-Ig binds only conserved regions of Env, it is also much broader than any bNAb. For example, eCD4-Ig efficiently neutralized 100% of a diverse panel of neutralization-resistant HIV-1, HIV-2 and simian immunodeficiency virus isolates, including a comprehensive set of isolates resistant to the CD4-binding site bNAbs VRC01, NIH45-46 and 3BNC117. Rhesus macaques inoculated with an AAV vector stably expressed 17-77 μg ml(-1) of fully functional rhesus eCD4-Ig for more than 40 weeks, and these macaques were protected from several infectious challenges with SHIV-AD8. Rhesus eCD4-Ig was also markedly less immunogenic than rhesus forms of four well-characterized bNAbs. Our data suggest that AAV-delivered eCD4-Ig can function like an effective HIV-1 vaccine.

Anatomy of undiagnosed fever--a physician's perspective

Undiagnosed fever is a vexing problem. The reasons why fever remains undiagnosed can be inherent to the underlying pathology, our shortcoming(s) or both. This article describes "our" causes based on cases seen over the years. It is apparent that with proper attention to details mystery of at least some undiagnosed fevers can be solved.

Direct expression and validation of phage-selected peptide variants in mammalian cells

Phage display is a key technology for the identification and maturation of high affinity peptides, antibodies, and other proteins. However, limitations of bacterial expression restrict the range and sensitivity of assays that can be used to evaluate phage-selected variants. To address this problem, selected genes are typically transferred to mammalian expression vectors, a major rate-limiting step in the iterative improvement of peptides and proteins. Here we describe a system that combines phage display and efficient mammalian expression in a single vector, pDQ1. This system permits immediate expression of phage-selected genes as IgG1-Fc fusions in mammalian cells, facilitating the rapid, sensitive characterization of a large number of library outputs for their biochemical and functional properties. We demonstrate the utility of this system by improving the ability of a CD4-mimetic peptide to bind the HIV-1 envelope glycoprotein and neutralize HIV-1 entry. We further improved the potency of the resulting peptide, CD4mim6, by limiting its ability to induce the CD4-bound conformation of the envelope glycoprotein. Thus, CD4mim6 and its variants can be used to investigate the properties of the HIV-1 envelope glycoprotein, and pDQ1 can accelerate the discovery of new peptides and proteins through phage display.

Giant cell arteritis in Mumbai

OBJECTIVE

To study the clinical profile of patients with giant cell arteritis in Mumbai.

METHODS

From our database, patients with a diagnosis of giant cell arteritis (GCA) over a fifteen year period (January 1990 to December 2005) were included. Clinical manifestations, temporal artery biopsy, treatment, and follow-up data of these patients were analyzed.

RESULTS

Twenty one patients with GCA were identified. However, data were available only for 16 patients. The median age was 66.5 years (58-78 yrs) with male to female ratio of 1:1. The mean time from symptom onset to diagnosis was 5.18 months (0.5-24 months). Clinical manifestations included new onset headache (15), fever (9), weight loss (9), jaw claudication (9), polymyalgia rheumatica (5), visual disturbances (3), scalp nodule (1), temporal artery tenderness (11), tortuosity (9), and scalp tenderness (6). ESR was elevated in 15 patients with a median of 106.5 mm at 1 hr (25-135 mm/hr). Temporal artery biopsy was done in 11 patients and confirmed the diagnosis in 10 patients. Color doppler study of the temporal arteries (9 patients) revealed halo sign (indicating arterial wall edema) in 6 patients. Biopsy as per site by color doppler study was performed in 6 of these patients and was positive in 5. All patients had a good initial response to steroids, however, on follow up, 3 patients required addition of methotrexate. At a median follow up (n = 14) of 6 months (range 6-156), steroids were successfully stopped in 7 patients at 1 to 3 years interval. The disease relapsed in 1 patient. Of the remaining 7 patients, 2 were steroid dependent and 5 patients were doing well on low dose prednisolone.

CONCLUSION

GCA, though uncommon in India, should be suspected in all elderly patients with a new onset headache, fever, jaw claudication, or high ESR. Color doppler sonography is a useful noninvasive method for the diagnosis of GCA and also helps to identify the site to biopsy. Most respond to steroid therapy while some need addition of steroid sparing agents.

Infective endocarditis--a tale of two cases and the lessons (re)learned

Infective endocarditis due to uncommon organisms or at uncommon sites presents a diagnostic challenge. Because signs and symptoms can be nonspecific and vary greatly, a high index of suspicion is necessary. We have recently treated two such cases, one due to HACEK organism (Eikenella corrodens) in a patient with established valvular heart disease and other of right sided endocarditis due to Pseudomonas aeruginosa. This report describes the diagnostic difficulties faced.

Adult onset Still's disease: a study of 14 cases

We studied the clinical profile, laboratory parameters, disease course, and outcomes of patients with adult onset Still's disease (AOSD). A retrospective analysis of adult patients with Still's disease diagnosed from 2000 to 2004 was carried out. Their clinical features and laboratory findings at presentation, disease course, and outcomes were analyzed. Data of 14 patients with Still's disease were analyzed. The age at disease onset ranged from 16 to 59 years with a mean of 29.85, the male to female ratio being 9:5. The mean duration of illness from onset of symptoms to presentation was 14.5 months (range). The most common clinical manifestations were fever (n = 14), articular symptoms (n = 14), rash (n = 8), weight loss (n = 12), and sore throat (n = 5). Elevated ESR was present in all patients with a mean of 98.3 mm at 1 h. Hepatic enzymes were elevated in seven patients at disease onset. The mean duration of follow up was 19.14 months (range). Three patients progressed to chronic arthropathy. Cyclosporine led to dramatic recovery in five patients. Macrophage activation syndrome (MAS) was present in two patients, one after sulfasalazine therapy. One patient with MAS died. Still's disease, although uncommon, has characteristic constellation of clinical and laboratory features and should be considered in the differential diagnosis of fever of unknown origin. Nonsteroidal anti-inflammatory drugs, steroids, and methotrexate may not be always effective, and cyclosporine is an effective drug in resistant cases. Sulfasalazine should be avoided in cases of AOSD.

Paget's disease of the bone: a report of three cases

Paget's disease is uncommon in Asians. We present 3 patients with varying manifestations. A 50 years old lady was detected to have raised alkaline phosphatase at a routine health check-up. Isoenzyme studies confirmed its bony origin. Bone scan revealed polyostotic disease. A 65 years old male patient with known Paget's disease of 6 years duration presented with pelvic girdle pain, progressive increase in alkaline phosphatase levels and worsening bone scan. A 45 years old male was admitted with chest pain. Cardiac evaluation was normal. Bone scan picked up a cough fracture in the left 7th rib and an incidental Paget's disease of the skull. All three had elevated markers of bone metabolism in the serum and urine. With monthly intravenous pamidronate there was significant improvement in the bone markers and follow-up bone scans.

Efficacy of alendronate, a bisphosphonate, in the treatment of AVN of the hip. A prospective open-label study

OBJECTIVE

To study the efficacy of alendronate, in the treatment of avascular necrosis (AVN) of the hip.

METHODS

Sixty patients with AVN of the hip (100 hips with AVN) were studied. The follow-up period ranged from 3 months to 5 yr. The most common cause of AVN was steroids. Parameters studied were walking time, standing time, pain and disability on a visual analogue scale (VAS), range of motion of the hip, X-ray and MRI of the hip. All patients were treated with alendronate 10 mg/day (or 70 mg/week) along with 500-1000 mg of daily calcium and vitamin D supplements, and were advised to avoid weight-bearing. NSAIDs and analgesics were permitted as needed and were recorded.

RESULTS

Forty-one patients (71 AVN hips) with AVN have been followed up for a minimum of 1 yr, 24 patients (42 AVN hips) for 2 yr and 21 patients (37 AVN hips) for more than 2 yr (average 37 month). Fourteen patients have been followed up for less than 1 yr (3-9 months). Significant reduction in pain and disability scores (P < 0.001) and significant increase in standing and walking time (P < 0.001) were observed. All hip movements improved at 1 yr (P value 0.000-0.009) with an insignificant decline after that (P > 0.001). Radiologically, the hips either stabilized in the same grade or progressed by one grade. MRI showed a decrease in marrow oedema in most cases at the 1-yr follow-up. Six patients (10 hips) required surgery and there were two (three hips) dropouts. The drug was well tolerated and there was a reduction in NSAID requirement.

CONCLUSION

Alendronate reduces pain, improves function and retards AVN progression. Early surgical intervention can be avoided in most patients.

NSAIDs and kidney

NSAIDs are commonly used drugs. Even with the advent of selective COX-2 inhibitors, nephrotoxicity still remains a concern. The adverse effects of NSAIDs are mediated via inhibition of prostaglandin synthesis from arachidonic acid by non-specific blocking of the enzyme cyclooxygenase leading to vasoconstriction and reversible mild renal impairment in volume contracted states. When unopposed, this may lead to acute tubular necrosis and acute renal failure. NSAIDs also produce interstitial nephritis with or without nephrotic syndrome secondary to minimal change disease. Although this presents as acute renal failure, it can progress in some cases to chronic renal failure. Papillary necrosis has been incriminated in the development of chronic renal failure secondary to NSAIDs. In patients on long term NSAIDs without acute or chronic renal failure, subclinical renal dysfunction such as reduced creatinine clearance and impaired urine concentrating ability has been shown to be present. Although this sub-clinical dysfunction is reversible on withdrawal of NSAIDs, some reports have suggested a persistent residual dysfunction. Even with a wide range of NSAIDs at our disposal, a renal safe NSAID is yet to be discovered.

Rheumatoid arthritis and the kidney

It is clear that kidney is involved in rheumatoid arthritis (RA) with both glomerular and tubular damage. Renal disease in RA however is usually asymptomatic and is detected only on laboratory investigations. It is often difficult to differentiate between damage due to disease activity and that due to drugs used to treat RA. Although there are a number of parameters to study renal function, these cannot be applied to day to day practice and still remain research tools. In such a scenario, it is important to periodically monitor serum creatinine and carry out urine examination so as to pick up the earliest signs of renal dysfunction.