Broadly neutralizing antibody epitopes on HIV-1 particles are exposed after virus interaction with host cells

The envelope (Env) glycoproteins on HIV-1 virions are the sole target of broadly neutralizing antibodies (bNAbs) and the focus of vaccines. However, many cross-reactive conserved epitopes are often occluded on virus particles, contributing to the evasion of humoral immunity. This study aimed to identify the Env epitopes that are exposed/occluded on HIV-1 particles and to investigate the mechanisms contributing to their masking. Using a flow cytometry-based assay, three HIV-1 isolates, and a panel of antibodies, we show that only select epitopes, including V2i, the gp120-g41 interface, and gp41-MPER, are accessible on HIV-1 particles, while V3, V2q, and select CD4bs epitopes are masked. These epitopes become accessible after allosteric conformational changes are induced by the pre-binding of select Abs, prompting us to test if similar conformational changes are required for these Abs to exhibit their neutralization capability. We tested HIV-1 neutralization where the virus-mAb mix was pre-incubated/not pre-incubated for 1 hour prior to adding the target cells. Similar levels of neutralization were observed under both assay conditions, suggesting that the interaction between virus and target cells sensitizes the virions for neutralization via bNAbs. We further show that lectin-glycan interactions can also expose these epitopes. However, this effect is dependent on the lectin specificity. Given that, bNAbs are ideal for providing sterilizing immunity and are the goal of current HIV-1 vaccine efforts, these data offer insight on how HIV-1 may occlude these vulnerable epitopes from the host immune response. In addition, the findings can guide the formulation of effective antibody combinations for therapeutic use. IMPORTANCE The human immunodeficiency virus (HIV-1) envelope (Env) glycoprotein mediates viral entry and is the sole target of neutralizing antibodies. Our data suggest that antibody epitopes including V2q (e.g., PG9, PGT145), CD4bs (e.g., VRC01, 3BNC117), and V3 (2219, 2557) are masked on HIV-1 particles. The PG9 and 2219 epitopes became accessible for binding after conformational unmasking was induced by the pre-binding of select mAbs. Attempts to understand the masking mechanism led to the revelation that interaction between virus and host cells is needed to sensitize the virions for neutralization by broadly neutralizing antibodies (bNAbs). These data provide insight on how bNAbs may gain access to these occluded epitopes to exert their neutralization effects and block HIV-1 infection. These findings have important implications for the way we evaluate the neutralizing efficacy of antibodies and can potentially guide vaccine design.

Broadly Neutralizing Antibody Epitopes on HIV-1 Particles are exposed after Virus Interaction with Host Cells

The envelope glycoproteins (Env) on HIV-1 virions are the sole target of broadly neutralizing antibodies (bNAb) and the focus of vaccines. However, many cross-reactive conserved epitopes are often occluded on virus particles, contributing to the evasion of humoral immunity. This study aimed to identify the Env epitopes that are exposed/occluded on HIV-1 particles and to investigate the mechanisms contributing to their masking. Using a flow cytometry-based assay, three HIV-1 isolates, and a panel of antibodies, we show that only select epitopes including V2i, gp120-g41 interface, and gp41-MPER are accessible on HIV-1 particles, while V3, V2q, and select CD4bs epitopes are masked. These epitopes become accessible after allosteric conformational changes are induced by pre-binding of select Abs, prompting us to test if similar conformational changes are required for these Abs to exhibit their neutralization capability. We tested HIV-1 neutralization where virus-mAb mix was pre-incubated/not pre-incubated for one hour prior to adding the target cells. Similar levels of neutralization were observed under both assay conditions, suggesting that the interaction between virus and target cells sensitizes the virions for neutralization via bNAbs. We further show that lectin-glycan interactions can also expose these epitopes. However, this effect is dependent on the lectin specificity. Given that, bNAbs are the ideal for providing sterilizing immunity and are the goal of current HIV-1 vaccine efforts, these data offer insight on how HIV-1 may occlude these vulnerable epitopes from the host immune response. In addition, the findings can guide the formulation of effective antibody combinations for therapeutic use.

Dual Role of HIV-1 Envelope Signal Peptide in Immune Evasion

HIV-1 Env signal peptide (SP) is an important contributor to Env functions. Env is generated from Vpu/Env encoded bicistronic mRNA such that the 5′ end of Env-N-terminus, that encodes for Env-SP overlaps with 3′ end of Vpu. Env SP displays high sequence diversity, which translates into high variability in Vpu sequence. This study aimed to understand the effect of sequence polymorphism in the Vpu-Env overlapping region (VEOR) on the functions of two vital viral proteins: Vpu and Env. We used infectious molecular clone pNL4.3-CMU06 and swapped its SP (or VEOR) with that from other HIV-1 isolates. Swapping VEOR did not affect virus production in the absence of tetherin however, presence of tetherin significantly altered the release of virus progeny. VEOR also altered Vpu’s ability to downregulate CD4 and tetherin. We next tested the effect of these swaps on Env functions. Analyzing the binding of monoclonal antibodies to membrane embedded Env revealed changes in the antigenic landscape of swapped Envs. These swaps affected the oligosaccharide composition of Env-N-glycans as shown by changes in DC-SIGN-mediated virus transmission. Our study suggests that genetic diversity in VEOR plays an important role in the differential pathogenesis and also assist in immune evasion by altering Env epitope exposure.

Studies on the influence of power ultrasound on dye penetration in leather dyeing using photomicrographic analysis

The use of power ultrasound in enhancing diffusion rate in various chemical as well as physical processes is gaining in importance. The influence of power ultrasound in the leather dyeing process on enhancing the penetration of dye through the leather matrix was studied. The penetration of dye through a leather cross-section for a given time in the presence and absence of an ultrasonic field (33 kHz, 150 W) was studied by photomicrographic analysis using a stereomicroscope. Different types of black dyes, such as Acid black 1, Metal complex black 194 and Direct black 155, were used for dyeing leather in the present study. Photomicrographic analysis of a cross-section of dyed leather indicated better penetration of dyes through the leather matrix with the use of ultrasound than without it. Therefore, the results indicate that ultrasound helps to improve the diffusion of dye and to reduce diffusional resistance in the leather dyeing process.

New approach to curb the transmission of leprosy

The effect of local treatment of nose of lepromatous type of patients with different formulations of rifampicin nasal drops/sprays was investigated in a large number of patients. The preparations were either sprayed or instilled into the nostrils after flushing the nostrils with normal saline at 37 degrees C. It was observed that 10 mg/ml of rifampicin was effective in reducing the BI and MI to zero in nose in seven days in majority of the patients. No untoward effect was seen in any of the patients. It is suggested that nasal sprays/drops may be able to prevent the transmission of hanseniasis, as nose is recognised to be an important portal of exit of M. leprae. Further when rifampicin drops/sprays are used as soon as the diagnosis is made, the nasal deformity may be prevented. It is believed that local treatment along with systemic therapy would go a long way in controlling the transmission of hanseniasis.

Life events in obsessive compulsive neurosis

Twenty four patients diagnosed to be suffering from Obsessive Compulsive Neurosis for the first time and individually matched controls were rated on a Life Events Scale. Leyton Obsessional Inventory was also administered to the patients and controls. It was seen that patients had significantly higher scores on life events for a time span of one year prior to the onset of illness as compared to controls. The patient group also scored highly on obsessional trait scores. The study points to a strong association between excess of life events and the onset of obsessional illness.

Non-narcotic orally effective, centrally acting analgesic from an Ayurvedic drug

Embelin, a p-quinone, is derived from Embelia ribes Burm. The analgesic effect of potassium embelate has been studied in rats and mice. The test drug was found to be effective by oral, i.m. and i.c.v. routes and the results compared well with morphine. Although potassium embelate acts centrally to produce analgesia, its effect is not antagonized by naloxone indicating a different central site of action. There is no precipitation of abstinence syndrome as observed with morphine. Peripheral site of action of the drug is ruled out as it lacks any demonstrable anti-inflammatory action. It can be concluded that high oral efficacy and non-narcotic properties of the test drug make it more acceptable than morphine. In addition, lack of any adverse effects, high therapeutic index and absence of abstinence syndrome confers a long term safety on potassium embelate for use as an analgesic.

Thiol-dependent and non-thiol-dependent stimulations of insulin release

The effects of reduced glutathione (GSH) and diamide (an oxidant of GSH) on insulin release induced by glucose, glyceraldehyde, leucine, tolbutamide, glibenclamide, Ca-ionophore A-23187, isoprenaline, and dbcAMP were studied using isolated rat pancreatic islets. In the absence or presence of low glucose (5.6 mM) neither GSH (0.1 mM) nor diamide (0.1 mM) affected insulin release. Insulinotropic action of glucose (11.1 mM) and glyceraldehyde (11.1 mM), and that of tolbutamide (0.1 mg/ml) and leucine (10 mM) both in the presence of 11.1 mM glucose was further augmented by GSH and inhibited by diamide. GSH (0.05-1 mM) and diamide (0.1 mM) failed to affect the insulin secretion evoked by glibenclamide (5 micrograms/ml) + glucose (11.1 mM), Ca-ionophore A-23187 (50 micrograms/ml) + glucose (5.6 mM), isoprenaline (1 microM) + glucose (5.6 mM), and db-cAMP (1 mM) + glucose (5.6 mM). The data suggest that the insulin-releasing capacity of glucose, glyceraldehyde, tolbutamide, and leucine depends on the redox state of islet thiols, whereas the insulin-releasing effect of glibenclamide, Ca-ionophore, isoprenaline, and db-cAMP does not. The possibility that thiol dependency is associated with those compounds increasing Ca uptake but not with compounds acting as Ca-ionophores or only by increasing intracellular cAMP is discussed.

Scientific evidence on the role of Ayurvedic herbals on bioavailability of drugs

Experiments were conducted to evaluate the scientific basis of the use of the trikatu group of acrids (long pepper, black pepper and ginger) in the large number of prescriptions in Ayurveda. [3H] vasicine and [3H] sparteine were taken as test drugs. Piper longum (long pepper) increased the blood levels of vasicine by nearly 233%. Under the influence of piperine, the active principle of Piper species, sparteine blood levels increased more than 100%. The results suggest that these acrids have the capacity to increase the bioavailability of certain drugs. It appears that the trikatu group of drugs increase bioavailability either by promoting rapid absorption from the gastrointestinal tract, or by protecting the drug from being metabolised/oxidised in its first passage through the liver after being absorbed, or by a combination of these two mechanisms.

Stricture-plasty for tubercular strictures of the gastro-intestinal tract

Twenty stricture-plasties have been performed for multiple tubercular strictures of the gastro-intestinal tract in 9 patients, who in total had 35 strictures. The procedure has been found to be safe, simple and effective in relieving obstructive symptoms. It does not appear to carry the disadvantages of entero-anastomosis or multiple and/or massive resections in cases of multiple tubercular strictures of the small bowel.

Catheter duodenostomy for perforated duodenal ulcer

A new technique of catheter duodenostomy is described as treatment for a large perforated duodenal ulcer in a patient who came to the hospital seven days after the perforation. The problem of gastric stasis due to pyloric obstruction was tackled by gastrostomy. Nutritional needs of the patient were met by feeding through the duodenostomy catheter.