Ocular manifestations of HIV infection at Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa

BACKGROUND

The pattern of HIV-associated eye disease has changed with ongoing advancements in highly active antiretroviral therapy (HAART). HIV-infected individuals now live longer, enabling us to observe the long-term effects of HIV and HAART on the eye. There are few recent studies on HIV-related ocular disease in sub-Saharan Africa.

OBJECTIVES

To describe the ocular manifestations of HIV in patients attending the Nthabiseng HIV clinic at Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa.

METHODS

A cross-sectional study was conducted in 2021 and 2022 using convenience sampling of patients at the HIV clinic. The participants' clinical history was taken, their files were reviewed, and they underwent ocular examination. Correlation between eyes was managed by taking disease in one eye as the presence of disease in the participant. Descriptive statistics were used to summarise participant characteristics. Univariate and multivariate logistic regression models were used to assess the odds ratio (OR) of developing HIV-associated ocular diseases, and a p-value of <0.05 was used to define statistical significance.

RESULTS

There were 182 participants (139 females and 43 males), with a mean (standard deviation) age of 48.9 (10.6) years. The most common anterior segment diagnoses were conjunctival microangiopathy (34.6%), pinguecula (31.3%) and cataracts (30.2%), while the most common posterior segment finding was peripheral retinal scarring with features in keeping of previous cytomegalovirus retinitis (24.2%). Notably, only 1.1% of patients had HIV retinopathy. A CD4 count <200 cells/μL showed an increased OR for cataracts (OR 4.24; p=0.003) and any anterior segment diagnoses (OR 10.05; p=0.029), while a CD4 count ≥200 cells/μL showed an increased risk of conjunctival microangiopathy (OR 2.14; p=0.017).

CONCLUSION

With the advent of HAART, ocular manifestations of HIV are changing and the incidence of severe ocular opportunistic infections and HIV retinopathy has decreased precipitously. Although this study has shown that patients with a CD4 count <200 cells/μL are at increased risk of developing anterior ocular manifestations of HIV, including cataracts, these diseases are relatively innocuous or easily treatable. Routine ocular screening of HIV patients seems to be substantially less important now than it was in the pre-HAART era.

Botulinum neurotoxin injections in essential infantile esotropia-a comparative study with surgery in large-angle deviations

PURPOSE

To compare botulinum neurotoxin (BNT) injections to surgery as first-line therapy in large-angle essential infantile esotropia (IE).

PATIENTS AND METHODS

Children between the ages 6 months and 6 years with IE of ≥40 prism dioptres (PD) were randomised to either a maximum of three BNT injections or surgical intervention of bimedial rectus muscle recession for angles ≤60 PD and augmented with BNT injection in angles >60 PD. Time taken for each procedure was documented. Orthophoria or misalignment of ≤10 PD was regarded as a complete response (CR). Follow-up visits were done at 3, 6, 12 and 24 weeks.

RESULTS

Mean (SD) age and baseline angle of esotropia were 26.9 (14.5) months and 61.9 PD (12.8), respectively, for the overall cohort. The proportion of children who achieved CR was significantly higher in the surgery arm compared to the BNT injection arm (OR = 4.01, 95% CI 1.74-9.22) but the time taken was six times longer (p < 0.0001). In the BNT arm, 55.2% of children aged ≤24 months and 16% of children >24 months achieved CR. In children with esotropia ≤60 PD, CR was achieved in 50% while those with esotropia >60 PD CR was achieved in 25%.

CONCLUSION

Surgery remains the gold standard for treatment of esotropia but BNT injection is a safe and effective alternative in children ≤24 m and with smaller angles of esotropia ≤60 PD in resource-limited centres.

Inhibition of vascular endothelial growth factor A expression in mouse granulosa cells by lentivector-mediated RNAi

Vascular endothelial growth factor (VEGF) has been found responsible for the induction of proliferation and differentiation in granulosa cells. We constructed four short hairpin RNA (shRNA) expression plasmids targeting the mouse VEGFA gene, and examined their effect on VEGF expression in mouse granulosa cells (MGC) in vitro. Four different shRNA oligonucleotides targeting the coding sequence of mouse VEGFA mRNA and one negative control (shNC) were designed and cloned into a pGPU6/GFP/Neo siRNA expression vector, and transiently transfected into MGC. At 48 h post-transfection, total RNA was extracted from the cells and subjected to qRT-PCR analysis. The most effective interference vector, shVEGF1487 was chosen for lentiviral construction. The recombinant plasmid was then transfected into 293FT cells via Lipofectamine(TM) 2000-mediated gene transfer, for the production of lentivirus, and then concentrated via ultracentrifugation. This lentiviral vector was then used for the transduction of MGC. VEGFA gene expression, apoptosis genes and VEGFA receptor genes were detected by qRT-PCR, the VEGFA protein level in culture media by ELISA assay and protein levels in MGC by Western blot analysis. The four VEGFA expression plasmids were successfully constructed and the most effective interference vector, shVEGF1487, was chosen for lentiviral production and MGC transduction. There was significant knockdown of the VEGFA gene, receptor genes and apoptosis genes for all the shVEGF constructs, compared with the shNC and Mock controls. The lentiviral vector also gave significant knockdown of the VEGFA gene. Protein levels were lower for most of the shVEGFs based on Western blot analysis with exception of VEGF1359; in this case, it was higher than shNC but lower than for the Mock group. Lentivector-transduced MGC also gave lower levels of protein. We conclude that shVEGF expression plasmids and lentivector carrying RNAi are promising tools for the inhibition of VEGF, the corresponding receptor genes, and apoptosis gene expression in MGC.

Doxycycline-regulated growth hormone gene expression system for swine

Although growth hormone gene transgenic animals are much larger than normal animals, they manifest differences that have adverse effects on survival due to overexpression of growth hormone. We developed a stable pig embryonic fibroblast cell line expressing pig growth hormone (pGH) using the Tet-On system, with which we can conditionally manipulate expression of pGH in vivo. Inducible expression of pGH was achieved by combining reserve Tet-controlled transcriptional activator and tetracycline-responsive element in a single plasmid. The mRNA expression of pGH was significantly increased compared to the non-induced group by about 10-fold. The controlled secretion of pGH induced by doxycycline was further tested in stably transfected cells. We conclude that inducible GH expression can be achieved in pig embryonic fibroblasts.

Demonstration of LanthaScreen™ TR-FRET-based nuclear receptor coactivator recruitment assay using PHERAstar, a multi-detection HTS microplate reader

An attempt was made to demonstrate the possibility of performing LanthaScreen™ TR-FRET based nuclear receptor coactivator recruitment assay using PHERAstar, a multi-detection HTS microplate reader. LanthaScreen™ nuclear receptor coactivator recruitment assay (M/s Invitrogen corporation, USA) was performed using PPAR-gamma receptor preparation in the agonist mode. TR-FRET measurements were done on PHERAstar, a multimode microplate reader (BMG LABTECH, Germany). The Lanthascreen PPAR gamma coactivator recruitment assay was successfully performed in the PHERAstar, multimode microplate reader. This was evidenced by an assay robustness score (Z') of 0.71. The current work demonstrates the suitability of using PHERAstar, a multi-detection HTS microplate reader.for performing LanthaScreen™ TR-FRET based nuclear receptor coactivator recruitment assays.

An immune response directed to proteinase and adhesin functional epitopes protects against Porphyromonas gingivalis-induced periodontal bone loss

Porphyromonas gingivalis, a pathogen associated with periodontitis, bound to fibrinogen, fibronectin, hemoglobin, and collagen type V with a similar profile to that of its major virulence factor, the cell surface RgpA-Kgp proteinase-adhesin complex. Using peptide-specific, purified Abs in competitive inhibition ELISAs and epitope mapping assays, we have identified potential adhesin binding motifs (ABMs) of the RgpA-Kgp complex responsible for binding to host proteins. The RgpA-Kgp complex and synthetic ABM and proteinase active site peptides conjugated to diphtheria toxoid, when used as vaccines, protected against P. gingivalis-induced periodontal bone loss in the murine periodontitis model. The most efficacious peptide and protein vaccines were found to induce a high-titer IgG1 Ab response. Furthermore, mice protected in the lesion and periodontitis models had a predominant P. gingivalis-specific IL-4 response, whereas mice with disease had a predominant IFN-gamma response. The peptide-specific Abs directed to the ABM2 sequence (EGLATATTFEEDGVA) protected against periodontal bone loss and inhibited binding of the RgpA-Kgp complex to fibrinogen, fibronectin, and collagen type V. Furthermore, the peptide-specific Abs directed to the ABM3 sequence (GTPNPNPNPNPNPNPGT) protected against periodontal bone loss and inhibited binding to hemoglobin. However, the most protective Abs were those directed to the active sites of the RgpA and Kgp proteinases. The results suggest that when the RgpA-Kgp complex, or functional binding motif or active site peptides are used as a vaccine, they induce a Th2 response that blocks function of the RgpA-Kgp complex and protects against periodontal bone loss.

Characterization of the Specificity of Arginine-Specific Gingipains fromPorphyromonas gingivalisReveals Active Site Differences between Different Forms of the Enzymes†

Porphyromonas gingivalis is a pathogen associated with periodontal disease, and arginine-specific proteases (gingipains-R) from the bacterium are important virulence factors. The specificity of two forms of gingipain-R, HRgpA and RgpB, for substrate positions C-terminal to the cleavage site was analyzed, and notable differences were observed between the enzymes. Molecular modeling of the HRgpA catalytic domain, based on the structure of RgpB, revealed that there are four amino acid substitutions around the active site of HRgpA relative to RgpB that may explain their different specificity. Previously, differences in the ability of these two gingipain-R forms to cleave a number of proteins were attributed to additional adhesins on HRgpA mediating increased interaction with the substrates. Here, purified RgpA(cat), the catalytic domain of HRgpA, which like RgpB also lacks adhesin subunits, was used to show that the differences between HRgpA and RgpB are probably due to the amino acid substitutions at the active site. The kinetics of cleavage of fibrinogen, a typical protein substrate for the gingipain-R enzymes, which is bound by HRgpA but not RgpA(cat) or RgpB, were evaluated, and it was shown that there was no difference in the cleavage of the fibrinogen Aalpha-chain between the different enzyme forms. HRgpA degraded the fibrinogen Bbeta-chain more efficiently, generating distinct cleavage products. This indicates that while the adhesin domain(s) play(s) a minor role in the cleavage of protein substrates, the major effect is still provided by the amino acid substitutions at the active site of rgpA gene products versus those of the rgpB gene.

A naturally occurring NAR variable domain binds the Kgp protease from Porphyromonas gingivalis

The new antigen receptor (NAR) from sharks consists of a single immunoglobulin variable domain attached to five constant domains, and is hypothesised to function as an antibody. Two closely related NARs with affinity for the Kgp (lysine-specific) gingipain protease from Porphyromonas gingivalis were selected by panning an NAR variable domain library. When produced in Escherichia coli, these recombinant NARs were stable, correctly folded, and specifically bound Kgp (K(d)=1.31+/-0.26x10(-7) M). Binding localised to the Kgp adhesin domains, however without inhibiting adhesin activity. These naturally occurring proteins indicate an immune response to pathogenic bacteria and suggest that the NAR is a true antibody-like molecule.

Expression of protease-activated receptor-2 by osteoblasts

Osteoblasts express protease-activated receptor-1 (PAR-1), which is activated by thrombin or by synthetic peptides corresponding to the new "tethered ligand" N-terminus of PAR-1 created by receptor cleavage. Both thrombin and human PAR-1-activating peptide stimulate an elevation of [Ca2+]i in the human SaOS-2 osteoblast-like cell line, but the peptide stimulates receptor-mediated Ca+ entry, whereas thrombin does not. Stimulation of proliferation in rat primary osteoblast-like cells is greater in response to rat PAR-1-activating peptide than to thrombin. Because the PAR-1-activating peptides are now known to activate PAR-2, the current study was undertaken to investigate whether osteoblasts express this receptor and, if so, whether this could account for the observed discrepancies between responses of osteoblasts to thrombin and to PAR-1-activating peptides. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemical studies demonstrated expression of PAR-2 by primary cultures of rat calvarial osteoblast-like cells. In immunohistochemical studies of embryonic mouse bones, osteoblasts showed positive staining for the presence of PAR-2. Activators of PAR-2 include trypsin, mast cell tryptase, gingipain-R, and synthetic peptides corresponding to the PAR-2 tethered ligand sequence. Treatment of primary rat osteoblast-like cells with rat PAR-2-activating peptide (SLIGRL), or SaOS-2 cells with human PAR-2-activating peptide (SLIGKV), caused a dose-dependent increase in [Ca2+]i. Trypsin or gingipain-R also induced an increase in intracellular calcium concentration, and caused reciprocal cross desensitization. Activators of PAR-2 caused a sharp peak in [Ca2+]i followed by a sustained plateau; [Ca2+]i returned to baseline levels upon treatment with ethylene-glycol tetraacetic acid (EGTA). Treatment of rat osteoblast-like cells in vitro with SLIGRL did not affect thymidine incorporation or endogenous alkaline phosphatase activity. The results presented here demonstrate that osteoblasts express PAR-2, and that such expression is able to account for the observed discrepancies between thrombin and PAR-1-activating peptides in their ability to evoke calcium entry, but not proliferative responses.