Nonpeptidergic neurons suppress mast cells via glutamate to maintain skin homeostasis.

Cutaneous mast cells mediate numerous skin inflammatory processes and have anatomical and functional associations with sensory afferent neurons. We reveal that epidermal nerve endings from a subset of sensory nonpeptidergic neurons expressing MrgprD are reduced by the absence of Langerhans cells. Loss of epidermal innervation or ablation of MrgprD-expressing neurons increased expression of a mast cell gene module, including the activating receptor, Mrgprb2, resulting in increased mast cell degranulation and cutaneous inflammation in multiple disease models. Agonism of MrgprD-expressing neurons reduced expression of module genes and suppressed mast cell responses. MrgprD-expressing neurons released glutamate which was increased by MrgprD agonism. Inhibiting glutamate release or glutamate receptor binding yielded hyperresponsive mast cells with a genomic state similar to that in mice lacking MrgprD-expressing neurons. These data demonstrate that MrgprD-expressing neurons suppress mast cell hyperresponsiveness and skin inflammation via glutamate release, thereby revealing an unexpected neuroimmune mechanism maintaining cutaneous immune homeostasis.

Competition for Active TGFß Cytokine Allows for Selective Retention of Antigen-Specific Tissue- Resident Memory T Cells in the Epidermal Niche.

Following antigen-driven expansion in lymph node, transforming growth factor-ß (TGFß) is required for differentiation of skin-recruited CD8+ T cell effectors into epidermal resident memory T (Trm) cells and their epidermal persistence. We found that the source of TGFß -supporting Trm cells was autocrine. In addition, antigen-specific Trm cells that encountered cognate antigen in the skin, and bystander Trm cells that did not, both displayed long-term persistence in the epidermis under steady-state conditions. However, when the active-TGFß was limited or when new T cell clones were recruited into the epidermis, antigen-specific Trm cells were more efficiently retained than bystander Trm cells. Genetically enforced TGFßR signaling allowed bystander Trm cells to persist in the epidermis as efficiently as antigen-specific Trm cells in both contexts. Thus, competition between T cells for active TGFß represents an unappreciated selective pressure that promotes the accumulation and persistence of antigen-specific Trm cells in the epidermal niche.

Test-retest repeatability and agreement of the quantitative contrast sensitivity function test: towards the validation of a new clinical endpoint.

PURPOSE: The purpose of this study is to investigate test-retest reliability and agreement of the quantitative contrast sensitivity function test (qCSF) in the retina clinic. METHODS: A total of 121 right eyes of 121 patients were tested and consecutively re-tested with qCSF in the retina clinic. Outcomes included area under the logarithm of contrast sensitivity function curve (AULCSF), contrast acuity, and contrast sensitivity thresholds at 1-18 cycles per degree (cpd). Test-retest means were compared with paired t-test, variability was compared with the Brown-Forsythe test, and intraclass correlation coefficient (ICC) and Bland Altman plots evaluated reliability and agreement. RESULTS: Mean test-retest differences for all qCSF metrics ranged from 0.02 to 0.05 log units without statistically significant differences in variability. Standard deviations ranged from 0.08 to 0.14. Coefficients of repeatability ranged from 0.16 to 0.27 log units. ICC > 0.9 for all metrics except 1cpd (ICC = 0.84, all p < 0.001); AULCSF ICC = 0.971. CONCLUSION: qCSF-measured contrast sensitivity shows great test-retest repeatability and agreement in the retina clinic.

Infection of a Nylon Foil Orbital Implant Due to Fusarium brachygibbosum and Lomentospora prolificans After Intranasal Methamphetamine Use.

The authors describe a case of nylon foil implant infection caused by Fusarium brachygibbosum , and Lomentospora prolificans following medial orbital wall fracture repair in the setting of postoperative nasal methamphetamine use. A 61-year-old male presented with OS pain and swelling after a physical assault on his face. A CT of maxillofacial bones without contrast showed a moderately comminuted fracture of the medial wall of the left orbit with depression of fracture fragments into the left ethmoid air cells. Six days after repair of the medial wall fracture, the patient returned with a new onset headache, OS pain, and swelling to the left medial canthal area. He reported snorting methamphetamine approximately 48 hours before his current presentation. CT imaging showed fat stranding and soft tissue density in the extraconal space adjacent to the left medial rectus muscle and chronic fracture deformity of lamina papyracea with approximately 4 mm of medial displacement of the fracture fragments. The patient showed little clinical improvement after 48 hours of intravenous antibiotics, which led to the removal of the nylon foil implant by a left orbitotomy. Intraoperative tissue cultures grew coagulase-negative Staphylococcus , F. brachygibbosum , and Lomentospora (Scedosporium) prolificans . The patient was subsequently transitioned to oral clindamycin 600 mg three times daily and voriconazole 200 mg two times daily. To the authors' knowledge, this is the first case report to document an association between snorted methamphetamine and a fungal infection of an orbital implant.

Granular Cell Tumor of the Orbit: Review of the Literature and a Proposed Treatment Modality.

PURPOSE: To document a unique case of granular cell tumor of the orbit, located lateral to and abutting the optic nerve, that benefited from treatment with proton beam irradiation, with a comprehensive review of the literature on granular cell tumor of the orbit. METHODS: Clinicopathologic case report with detailed imaging features and histopathologic and immunohistochemical evaluation for cytoplasmic tumor biomarkers differentiating granular cell tumor (GCT) from it mimicking lesions with relevant literature citations. The authors reviewed 20 cases of orbital GCT from 2011 to 2020 in addition to 40 cases from 1948 to 2011 and included a summary of imaging and clinical features, outcomes, and recommended treatment modalities. RESULTS: A 32-year-old man with 1-year history of left retrobulbar pain and diplopia on lateral gaze, intermittent left eyelid swelling, and a tonic left pupil was found to have a fusiform intraconal mass extending toward the orbital apex and abutting the optic nerve. Histopathologic and immunohistochemical investigations collectively supplied data diagnostic of a GCT with an initial low proliferation rate. GCT is a soft tissue neoplasm that originates in the nervous system and can occur anywhere in the body. This enhancing tumor is isointense to gray matter on T1-weighted MRI, hypointense on T2. After an incisional biopsy, the patient's symptoms persisted, and follow-up imaging several months later revealed further growth of the mass. The impossibility of complete surgical removal prompted the decision to treat with proton beam radiation therapy, which resulted in substantial regression in the size of the residual tumor. Most frequently involving the inferior rectus muscle (42%), orbital GCT is usually benign with only 4 reported cases of malignant orbital GCT (7%). Wide surgical resection with complete removal is usually curative for benign orbital GCT, and proton beam radiation therapy can aid in tumor shrinkage. CONCLUSIONS: GCT should be considered in the differential diagnosis when encountering patients with mass lesions involving the extraocular muscles, peripheral nerves, or less frequently, the optic nerve or orbital apex. Immunohistochemical analysis of biopsied tissue is required for the definitive diagnosis of GCT. Consideration of adjuvant therapies such as proton beam radiation therapy may be appropriate in cases of incomplete surgical resection of benign GCT. Proton beam radiation therapy can be an excellent therapeutic option for symptomatic relief and residual tumor size reduction with an acceptable toxicity profile.

Structural and functional definition of a vulnerable site on the hemagglutinin of highly pathogenic avian influenza A virus H5N1.

Most neutralizing antibodies against highly pathogenic avian influenza A virus H5N1 recognize the receptor-binding site (RBS) on the globular head domain and the stem of H5N1 hemagglutinin (HA). Through comprehensive analysis of multiple human protective antibodies, we previously identified four vulnerable sites (VS1-VS4) on the globular head domain. Among them, the VS1, occupying the opposite side of the RBS on the same HA, was defined by the epitope of antibody 65C6. In this study, we report the crystal structures of two additional human H5N1 antibodies isolated from H5N1-infected individuals, 3C11 and AVFluIgG01, bound to the head at 2.33- and 2.30-Å resolution, respectively. These two new antibody epitopes have large overlap with and extend beyond the original VS1. Site-directed mutagenesis experiments identified eight pivotal residues (Ser-126b, Lys-165, Arg-166, Ser-167, Tyr-168, Asn-169, Thr-171, and Asn-172) critical for 65C6-, 3C11-, and AVFluIgG01-binding and neutralization activities. These residues formed a unique "Y"-shaped surface on H5N1 globular head and are highly conserved among H5N1 viruses. Our results further support the existence of a vulnerable site distinct from the RBS and the stem region of H5N1 HA, and future design of immunogens should take this particular site into consideration.

Complementary recognition of the receptor-binding site of highly pathogenic H5N1 influenza viruses by two human neutralizing antibodies.

The highly pathogenic avian influenza virus H5N1 is a major threat to global public health and therefore a high-priority target of current vaccine development. The receptor-binding site (RBS) on the globular head of hemagglutinin (HA) in the viral envelope is one of the major target sites for antibody recognition against H5N1 and other influenza viruses. Here, we report the identification and characterization of a pair of human RBS-specific antibodies, designated FLD21.140 and AVFluIgG03, that are mutually complementary in their neutralizing activities against a diverse panel of H5N1 viruses. Crystallographic analysis and site-directed mutagenesis revealed that the two antibodies share a similar RBS-binding mode, and their individual specificities are governed by residues at positions 133a, 144, and 145. Specifically, FLD21.140 preferred Leu-133a/Lys-144/Ser-145, whereas AVFluIgG03 favored Ser-133a/Thr-144/Pro-145 residue triplets, both of which perfectly matched the most prevalent residues in viruses from epidemic-originating regions. Of note, according to an analysis of 3758 H5 HA sequences available in the Influenza Virus Database at the National Center for Biotechnology Information, the residues Leu-133a/Ser-133a and Ser-145/Pro-145 constituted more than 87.6 and 99.3% of all residues at these two positions, respectively. Taken together, our results provide a structural understanding for the neutralizing complementarity of these two antibodies and improve our understanding of the RBS-specific antibody response against H5N1 infection in humans.

P209L mutation in Bag3 does not cause cardiomyopathy in mice.

Bcl-2-associated athanogene 3 (BAG3) is a cochaperone protein and a central player of the cellular protein quality control system. BAG3 is prominently expressed in the heart and plays an essential role in cardiac protein homeostasis by interacting with chaperone heat shock proteins (HSPs) in large, functionally distinct multichaperone complexes. The BAG3 mutation of proline 209 to leucine (P209L), which resides in a critical region that mediates the direct interaction between BAG3 and small HSPs (sHSPs), is associated with cardiomyopathy in humans. However, the mechanism by which the BAG3 P209L missense mutation leads to cardiomyopathy remains unknown. To determine the molecular basis underlying the cardiomyopathy caused by the BAG3 P209L mutation, we generated a knockin (KI) mouse model in which the endogenous Bag3 gene was replaced with mutant Bag3 containing the P215L mutation, which is equivalent to the human P209L mutation. We performed physiological, histological, and biochemical analyses of Bag3 P209L KI mice to determine the functional, morphological, and molecular consequences of the P209L mutation. We found that Bag3 P209L KI mice exhibited normal cardiac function and morphology up to 16 mo of age. Western blot analysis further revealed that levels of sHSPs, stress-inducible HSPs, ubiquitinated proteins, and autophagy were unaffected in P209L mutant mouse hearts. In conclusion, the P209L mutation in Bag3 does not cause cardiomyopathy in mice up to 16 mo of age under baseline conditions. NEW & NOTEWORTHY Bcl-2-associated athanogene 3 (BAG3) P209L mutation is associated with human cardiomyopathy. A recent study reported that transgenic mice overexpressing human BAG3 P209L in cardiomyocytes have cardiac dysfunction. In contrast, our P209L mice that express mutant BAG3 at the same level as that of wild-type mice displayed no overt phenotype. Our results suggest that human cardiomyopathy may result from species-specific requirements for the conserved motif that is disrupted by P209L mutation or from genetic background-dependent effects.

Glycosyl-Phosphatidylinositol-Anchored Anti-HIV Env Single-Chain Variable Fragments Interfere with HIV-1 Env Processing and Viral Infectivity.

In previous studies, we demonstrated that single-chain variable fragments (scFvs) from anti-human immunodeficiency virus (HIV) Env monoclonal antibodies act as entry inhibitors when tethered to the surface of target cells by a glycosyl-phosphatidylinositol (GPI) anchor. Interestingly, even if a virus escapes inhibition at entry, its replication is ultimately controlled. We hypothesized that in addition to functioning as entry inhibitors, anti-HIV GPI-scFvs may also interact with Env in an infected cell, thereby interfering with the infectivity of newly produced virions. Here, we show that expression of the anti-HIV Env GPI-scFvs in virus-producing cells reduced the release of HIV from cells 5- to 22-fold, and infectivity of the virions that were released was inhibited by 74% to 99%. Additionally, anti-HIV Env GPI-scFv X5 inhibited virion production and infectivity after latency reactivation and blocked transmitter/founder virus production and infectivity in primary CD4+ T cells. In contrast, simian immunodeficiency virus (SIV) production and infectivity were not affected by the anti-HIV Env GPI-scFvs. Loss of infectivity of HIV was associated with a reduction in the amount of virion-associated Env gp120. Interestingly, an analysis of Env expression in cell lysates demonstrated that the anti-Env GPI-scFvs interfered with processing of Env gp160 precursors in cells. These data indicate that GPI-scFvs can inhibit Env processing and function, thereby restricting production and infectivity of newly synthesized HIV. Anti-Env GPI-scFvs therefore appear to be unique anti-HIV molecules as they derive their potent inhibitory activity by interfering with both early (receptor binding/entry) and late (Env processing and incorporation into virions) stages of the HIV life cycle.IMPORTANCE The restoration of immune function and persistence of CD4+ T cells in HIV-1-infected individuals without antiretroviral therapy requires a way to increase resistance of CD4+ T cells to infection by both R5- and X4-tropic HIV-1. Previously, we reported that anchoring anti-HIV-1 single-chain variable fragments (scFvs) via glycosyl-phosphatidylinositol (GPI) to the surface of permissive cells conferred a high level of resistance to HIV-1 variants at the level of entry. Here, we report that anti-HIV GPI-scFvs also derive their potent antiviral activity in part by blocking HIV production and Env processing, which consequently inhibits viral infectivity even in primary infection models. Thus, we conclude that GPI-anchored anti-HIV scFvs derive their potent blocking activity of HIV replication by interfering with successive stages of the viral life cycle. They may be effectively used in genetic intervention of HIV-1 infection.

Divergent Requirement of Fc-Fcγ Receptor Interactions for In Vivo Protection against Influenza Viruses by Two Pan-H5 Hemagglutinin Antibodies.

Recent studies have shown that Fc-Fcγ receptor (FcγR) interactions are required for in vivo protection against influenza viruses by broadly reactive anti-hemagglutinin (HA) stem, but not virus strain-specific, anti-receptor binding site (RBS), antibodies (Abs). Since only a few Abs recognizing epitopes in the head region but outside the RBS have been tested against single-challenge virus strains, it remains unknown whether Fc-FcγR interactions are required for in vivo protection by Abs recognizing epitopes outside the RBS and whether the requirement is virus strain specific or epitope specific. In the present study, we therefore investigated the requirements for in vivo protection using two pan-H5 Abs, 65C6 and 100F4. We generated chimeric Abs, 65C6/IgG2a and 100F4/IgG2a, which preferentially engage activating FcγRs, and isogenic forms, 65C6/D265A and 100F4/D265A, which do not bind FcγR. Virus neutralizing activity, binding, antibody-dependent cellular cytotoxicity (ADCC), and in vivo protection of these Abs were compared using three H5 strains, A/Shenzhen/406H/2006 (SZ06), A/chicken/Shanxi/2/2006 (SX06), and A/chicken/Netherlands/14015526/2014 (NE14). We found that all four chimeric Abs bound and neutralized the SZ06 and NE14 strains but poorly inhibited the SX06 strain. 65C6/IgG2a and 100F4/IgG2a, but not 65C6/D265A and 100F4/D265A, mediated ADCC against target cells expressing HA derived from all three virus strains. Interestingly, both 65C6/IgG2a and 65C6/D265A demonstrated comparable protection against all three virus strains in vivo; however, 100F4/IgG2a, but not 100F4/D265A, showed in vivo protection. Thus, we conclude that Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6, and therefore, protection is not virus strain specific but epitope specific.IMPORTANCE Abs play an important role in immune protection against influenza virus infection. Fc-FcγR interactions are required for in vivo protection by broadly neutralizing antistem, but not by virus strain-specific, anti-receptor binding site (RBS), Abs. Whether such interactions are necessary for protection by Abs that recognize epitopes outside RBS is not fully understood. In the present study, we investigated in vivo protection mechanisms against three H5 strains by two pan-H5 Abs, 65C6 and 100F4. We show that although these two Abs have similar neutralizing, binding, and ADCC activities against all three H5 strains in vitro, they have divergent requirements for Fc-FcγR interactions to protect against the three H5 strains in vivo The Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6. Thus, we conclude that Fc-FcγR interactions for in vivo protection by pan-H5 Abs is not strain specific, but epitope specific.

A Bivalent Heterologous DNA Virus-Like-Particle Prime-Boost Vaccine Elicits Broad Protection against both Group 1 and 2 Influenza A Viruses.

Current seasonal influenza vaccines are efficacious when vaccine strains are matched with circulating strains. However, they do not protect antigenic variants and newly emerging pandemic and outbreak strains. Thus, there is a critical need for developing so-called "universal" vaccines that protect against all influenza viruses. In the present study, we developed a bivalent heterologous DNA virus-like particle prime-boost vaccine strategy. We show that mice immunized with this vaccine were broadly protected against lethal challenge from group 1 (H1, H5, and H9) and group 2 (H3 and H7) viruses, with 94% aggregate survival. To determine the immune correlates of protection, we performed passive immunizations and in vitro assays. We show that this vaccine elicited antibody responses that bound HA from group 1 (H1, H2, H5, H6, H8, H9, H11, and H12) and group 2 (H3, H4, H7, H10, H14, and H15) and neutralized homologous and intrasubtypic H5 and H7 and heterosubtypic H1 viruses and hemagglutinin-specific CD4 and CD8 T cell responses. As a result, passive immunization with immune sera fully protected mice against H5, H7, and H1 challenge, whereas with both immune sera and T cells the mice survived heterosubtypic H3 and H9 challenge. Thus, it appears that (i) neutralizing antibodies alone fully protect against homologous and intrasubtypic H5 and H7 and (ii) neutralizing and binding antibodies are sufficient to protect against heterosubtypic H1, (iii) but against heterosubtypic H3 and H9, binding antibodies and T cells are required for complete survival. We believe that this vaccine regimen could potentially be a candidate for a "universal" influenza vaccine.IMPORTANCE Influenza virus infection is global health problem. Current seasonal influenza vaccines are efficacious only when vaccine strains are matched with circulating strains. However, these vaccines do not protect antigenic variants and newly emerging pandemic and outbreak strains. Because of this, there is an urgent need to develop so-called "universal" influenza vaccines that can protect against both current and future influenza strains. In the present study, we developed a bivalent heterologous prime-boost vaccine strategy. We show that a bivalent vaccine regimen elicited broad binding and neutralizing antibody and T cell responses that conferred broad protection against diverse challenge viruses in mice, suggesting that this bivalent prime-boost strategy could practically be a candidate for a "universal" influenza vaccine.

Glycosylphosphatidylinositol-Anchored Anti-HIV scFv Efficiently Protects CD4 T Cells from HIV-1 Infection and Deletion in hu-PBL Mice.

Despite success in viral inhibition and CD4 T cell recovery by highly active antiretroviral treatment (HAART), HIV-1 is still not curable due to the persistence of the HIV-1 reservoir during treatment. One patient with acute myeloid leukemia who received allogeneic hematopoietic stem cell transplantation from a homozygous CCR5 Δ32 donor has had no detectable viremia for 9 years after HAART cessation. This case has inspired a field of HIV-1 cure research focusing on engineering HIV-1 resistance in permissive cells. Here, we employed a glycosylphosphatidylinositol (GPI)-scFv X5 approach to confer resistance of human primary CD4 T cells to HIV-1. We showed that primary CD4 T cells expressing GPI-scFv X5 were resistant to CCR5 (R5)-, CXCR4 (X4)-, and dual-tropic HIV-1 and had a survival advantage compared to control cells ex vivo In a hu-PBL mouse study, GPI-scFv X5-transduced CD4 T cells were selected in peripheral blood and lymphoid tissues upon HIV-1 infection. Finally, GPI-scFv X5-transduced CD4 T cells, after being cotransfused with HIV-infected cells, showed significantly reduced viral loads and viral RNA copy numbers relative to CD4 cells in hu-PBL mice compared to mice with GPI-scFv AB65-transduced CD4 T cells. We conclude that GPI-scFv X5-modified CD4 T cells could potentially be used as a genetic intervention against both R5- and X4-tropic HIV-1 infections. IMPORTANCE: Blocking of HIV-1 entry is one of most promising approaches for therapy. Genetic disruption of the HIV-1 coreceptor CCR5 by nucleases in T cells is under 2 clinical trials and leads to reduced viremia in patients. However, the emergence of viruses using the CXCR4 coreceptor is a concern for therapies applying single-coreceptor disruption. Here, we report that HIV-1-permissive CD4 T cells engineered with GPI-scFv X5 are resistant to R5-, X4-, or dual-tropic virus infection ex vivo In a preclinical study using hu-PBL mice, we show that CD4 T cells were protected and that GPI-scFv X5-transduced cells were selected in HIV-1-infected animals. Moreover, we show that GPI-scFv X5-transduced CD4 T cells exerted a negative effect on virus replication in vivo We conclude that GPI-scFv X5-modified CD4 T cells could potentially be used as a genetic intervention against both R5- and X4-tropic HIV-1 infections.

T Cell-Macrophage Fusion Triggers Multinucleated Giant Cell Formation for HIV-1 Spreading.

HIV-1-infected macrophages participate in virus dissemination and establishment of virus reservoirs in host tissues, but the mechanisms for virus cell-to-cell transfer to macrophages remain unknown. Here, we reveal the mechanisms for cell-to-cell transfer from infected T cells to macrophages and virus spreading between macrophages. We show that contacts between infected T lymphocytes and macrophages lead to cell fusion for the fast and massive transfer of CCR5-tropic viruses to macrophages. Through the merge of viral material between T cells and macrophages, these newly formed lymphocyte-macrophage fused cells acquire the ability to fuse with neighboring noninfected macrophages. Together, these two-step envelope-dependent cell fusion processes lead to the formation of highly virus-productive multinucleated giant cells reminiscent of the infected multinucleated giant macrophages detected in HIV-1-infected patients and simian immunodeficiency virus-infected macaques. These mechanisms represent an original mode of virus transmission for viral spreading and a new model for the formation of macrophage virus reservoirs during infection.IMPORTANCE We reveal a very efficient mechanism involved in cell-to-cell transfer from infected T cells to macrophages and subsequent virus spreading between macrophages by a two-step cell fusion process. Infected T cells first establish contacts and fuse with macrophage targets. The newly formed lymphocyte-macrophage fused cells then acquire the ability to fuse with surrounding uninfected macrophages, leading to the formation of infected multinucleated giant cells that can survive for a long time, as evidenced in vivo in lymphoid organs and the central nervous system. This route of infection may be a major determinant for virus dissemination and the formation of macrophage virus reservoirs in host tissues during HIV-1 infection.

A case series detailing the successful reversal of the effects of mifepristone using progesterone.

BACKGROUND: Some women who take mifepristone, a progesterone receptor antagonist, in order to terminate their pregnancies, change their minds and desire to stop the medical abortion process. There are only two articles in the medical literature documenting the reversal of the effects of mifepristone. OBJECTIVE: We present and analyze a series of women who attempted to reverse the effects of mifepristone by taking supplemental progesterone to determine if the reversal of the effects mifepristone with progesterone is possible and safe. Additionally, we compare different progesterone regimens to determine relative efficacies. METHODS: This is an observational case series of 754 patients who decided to attempt to reverse the medical abortion process after taking mifepristone but before taking the second drug in the protocol, misoprostol. We followed the patients, who were given progesterone in an effort to reverse the effects of mifepristone, and conducted statistical analyses to determine the efficacies of different protocols compared to a control mifepristone embryo survival rate, derived from the literature. RESULTS: Intramuscular progesterone and high dose oral progesterone were the most effective with reversal rates of 64% (P < 0.001) and 68% (P < 0.001), respectively. There was no apparent increased risk of birth defects. Conclusions: The reversal of the effects of mifepristone using progesterone is safe and effective.

The Glycosylphosphatidylinositol-Anchored Variable Region of Llama Heavy Chain-Only Antibody JM4 Efficiently Blocks both Cell-Free and T Cell-T Cell Transmission of Human Immunodeficiency Virus Type 1.

The variable regions (VHHs) of two heavy chain-only antibodies, JM2 and JM4, from llamas that have been immunized with a trimeric gp140 bound to a CD4 mimic have been recently isolated (here referred to as VHH JM2 and VHH JM4, respectively). JM2 binds the CD4-binding site of gp120 and neutralizes HIV-1 strains from subtypes B, C, and G. JM4 binds gp120 and neutralizes HIV-1 strains from subtypes A, B, C, A/E, and G in a CD4-dependent manner. In the present study, we constructed glycosylphosphatidylinositol (GPI)-anchored VHH JM2 and JM4 along with an E4 control and transduced them into human CD4+ cell lines and primary CD4 T cells. We report that by genetically linking the VHHs with a GPI attachment signal, VHHs are targeted to the lipid rafts of the plasma membranes. Expression of GPI-VHH JM4, but not GPI-VHH E4 and JM2, on the surface of transduced TZM.bl cells potently neutralizes multiple subtypes of HIV-1 isolates, including tier 2 or 3 strains, transmitted founders, quasispecies, and soluble single domain antibody (sdAb) JM4-resistant viruses. Moreover, transduction of CEMss-CCR5 cells with GPI-VHH JM4, but not with GPI-VHH E4, confers resistance to both cell-free and T cell-T cell transmission of HIV-1 and HIV-1 envelope-mediated fusion. Finally, GPI-VHH JM4-transduced human primary CD4 T cells efficiently resist both cell-free and T cell-T cell transmission of HIV-1. Thus, we conclude that VHH JM4, when targeted to the lipid rafts of the plasma membrane, efficiently neutralizes HIV-1 infection via both cell-free and T cell-T cell transmission. Our findings should have important implications for GPI-anchored antibody-based therapy against HIV-1. IMPORTANCE: Lipid rafts are specialized dynamic microdomains of the plasma membrane and have been shown to be gateways for HIV-1 budding as well as entry into T cells and macrophages. In nature, many glycosylphosphatidylinositol (GPI)-anchored proteins localize in the lipid rafts. In the present study, we developed GPI-anchored variable regions (VHHs) of two heavy chain-only antibodies, JM2 and JM4, from immunized llamas. We show that by genetically linking the VHHs with a GPI attachment signal, VHHs are targeted to the lipid rafts of the plasma membranes. GPI-VHH JM4, but not GPI-VHH JM2, in transduced CD4+ cell lines and human primary CD4 T cells not only efficiently blocks diverse HIV-1 strains, including tier 2 or 3 strains, transmitted founders, quasispecies, and soluble sdAb JM4-resistant strains, but also efficiently interferes T cell-T cell transmissions of HIV-1 and HIV-1 envelope-mediated fusion. Our findings should have important implications in GPI-anchored antibody-based therapy against HIV-1.

DNA prime and virus-like particle boost from a single H5N1 strain elicits broadly neutralizing antibody responses against head region of H5 hemagglutinin.

Since 1996, highly pathogenic avian influenza (HPAI) H5N1 virus has presented a persistent threat to public health. Its high degree of genetic diversity also poses enormous challenges in developing effective vaccines. To search for vaccine regimens that could elicit broadly neutralizing antibody responses against diverse HPAI H5N1 strains, in the present study we tested H5 hemagglutinin (HA) from an A/Thailand/1(KAN)-1/2004 strain in a heterologous prime-boost vaccination. We demonstrated that priming mice with DNA and boosting with virus-like particle induced antibody responses that cross-neutralize all reported clades and subclades of HPAI H5N1 viruses and protect mice from high lethal dose HPAI H5N1 challenge in both active and passive immunizations. Unexpectedly, cross-divergent H5 neutralizing antibodies are directed to the HA head and block both attachment and postattachment of virus entry. Thus, we conclude that as a promising pan-H5 vaccine candidate this prime-boost regimen could be further developed in ferrets and in humans.

Unraveling of a neutralization mechanism by two human antibodies against conserved epitopes in the globular head of H5 hemagglutinin.

The rapid spread of highly pathogenic avian influenza (HPAI) H5N1 virus underscores the importance of effective antiviral treatment. Previously, we developed human monoclonal antibodies 65C6 and 100F4 that neutralize almost all (sub)clades of HPAI H5N1. The conserved 65C6 epitope was mapped to the globular head of HA. However, neither the 100F4 epitope nor the neutralization mechanism by these antibodies was known. In this study, we determined the 100F4 epitope and unraveled a neutralization mechanism by antibodies 65C6 and 100F4.

Trimeric glycosylphosphatidylinositol-anchored HCDR3 of broadly neutralizing antibody PG16 is a potent HIV-1 entry inhibitor.

PG9 and PG16 are two quaternary-structure-specific broadly neutralizing antibodies with unique HCDR3 subdomains. Previously, we showed that glycosylphosphatidylinositol (GPI)-anchored HCDR3 subdomains (GPI-HCDR3) can be targeted to lipid rafts of the plasma membrane, bind to the epitope recognized by HCDR3 of PG16, and neutralize diverse HIV-1 isolates. In this study, we further developed trimeric GPI-HCDR3s and demonstrated that trimeric GPI-HCDR3 (PG16) dramatically improves anti-HIV-1 neutralization, suggesting that a stoichiometry of recognition of 3 or 2 HCDR3 molecules (PG16) to 1 viral spike is possible.

A variant macaque-tropic human immunodeficiency virus type 1 is resistant to alpha interferon-induced restriction in pig-tailed macaque CD4+ T cells.

Human immunodeficiency virus type 1 (HIV-1) antagonizes innate restriction factors in order to infect and persistently replicate in a host. In a previous study, we demonstrated that HIV-1 NL4-3 with a simian immunodeficiency virus mne (SIVmne) vif gene substitution (HSIV-vif-NL4-3) could infect and replicate in pig-tailed macaques (PTM), indicating that APOBEC3 proteins are primary barriers to transmission. Because viral replication was persistent but low, we hypothesized that HSIV-vif-NL4-3 may be suppressed by type I interferons (IFN-I), which are known to upregulate the expression of innate restriction factors. Here, we demonstrate that IFN-α more potently suppresses HSIV-vif-NL4-3 in PTM CD4(+) T cells than it does pathogenic SIVmne027. Importantly, we identify a variant (HSIV-vif-Yu2) that is resistant to IFN-α, indicating that the IFN-α-induced barrier can be overcome by HSIV-vif chimeras in PTM CD4(+) T cells. Interestingly, HSIV-vif-Yu2 and HSIV-vif-NL4-3 are similarly restricted by PTM BST2/Tetherin, and neither virus downregulates it from the surface of infected PTM CD4(+) T cells. Resistance to IFN-α-induced restriction appears to be conferred by a determinant in HSIV-vif-Yu2 that includes env su. Finally, we show that the Yu-2 env su allele may overcome an IFN-α-induced barrier to entry. Together, our data demonstrate that the prototype macaque-tropic HIV-1 clones based on NL4-3 may not sufficiently antagonize innate restriction in PTM cells. However, variants with resistance to IFN-α-induced restriction factors in PTM CD4(+) T cells may enhance viral replication by overcoming a barrier early in the viral replication cycle.