Human infection studies: Key considerations for challenge agent development and production

Human infection (or challenge) studies involve the intentional administration of a pathogen (challenge agent) to volunteers. The selection, isolation, development and production of the challenge agent is one of the first steps in developing a challenge study and critical for minimising the risk to volunteers. Regulatory oversight for this production differs globally. Manufacturing agents within a Good Manufacturing Practice (GMP) facility reduces the risk of the manufacturing process by including processes such as confirming the identity of the challenge agent and ascertaining that it's pure and free from impurities. However, in some cases it's not possible or feasible to manufacture to GMP standards, for example where the challenge agent requires an intermediate vector for growth. There is lack of clear guidance on what the minimum requirements for high-quality safe manufacture outside of GMP facilities should be and here we describe the development of a considerations document for the selection and production of challenge agents to meet this need.

HIV-1 infection and the lack of viral control are associated with greater expression of interleukin-21 receptor on CD8+ T cells

OBJECTIVES

Interleukin-21 (IL-21) has been linked with the generation of virus-specific memory CD8+ T cells following acute infection with HIV-1 and reduced exhaustion of CD8+ T cells. IL-21 has also been implicated in the promotion of CD8+ T-cell effector functions during viral infection. Little is known about the expression of interleukin-21 receptor (IL-21R) during HIV-1 infection or its role in HIV-1-specific CD8+ T-cell maintenance and subsequent viral control.

METHODS

We compared levels of IL-21R expression on total and memory subsets of CD8+ T cells from HIV-1-negative and HIV-1-positive donors. We also measured IL-21R on antigen-specific CD8+ T cells in volunteers who were positive for HIV-1 and had cytomegalovirus-responding T cells. Finally, we quantified plasma IL-21 in treatment-naive HIV-1-positive individuals and compared this with IL-21R expression.

RESULTS

IL-21R expression was significantly higher on CD8+ T cells (P = 0.0256), and on central memory (P = 0.0055) and effector memory (P = 0.0487) CD8+ T-cell subsets from HIV-1-positive individuals relative to HIV-1-negative individuals. For those infected with HIV-1, the levels of IL-21R expression on HIV-1-specific CD8+ T cells correlated significantly with visit viral load (r = 0.6667, P = 0.0152, n = 13) and inversely correlated with plasma IL-21 (r = -0.6273, P = 0.0440, n = 11). Lastly, CD8+ T cells from individuals with lower set point viral load who demonstrated better viral control had the lowest levels of IL-21R expression and highest levels of plasma IL-21.

CONCLUSION

Our data demonstrates significant associations between IL-21R expression on peripheral CD8+ T cells and viral load, as well as disease trajectory. This suggests that the IL-21 receptor could be a novel marker of CD8+ T-cell dysfunction during HIV-1 infection.

Evaluation of mucosal adjuvants and immunization routes for the induction of systemic and mucosal humoral immune responses in macaques

Delivering vaccine antigens to mucosal surfaces is potentially very attractive, especially as protection from mucosal infections may be mediated by local immune responses. However, to date mucosal immunization has had limited successes, with issues of both safety and poor immunogenicity. One approach to improve immunogenicity is to develop adjuvants that are effective and safe at mucosal surfaces. Differences in immune responses between mice and men have overstated the value of some experimental adjuvants which have subsequently performed poorly in the clinic. Due to their closer similarity, non-human primates can provide a more accurate picture of adjuvant performance. In this study we immunised rhesus macaques (Macaca mulatta) using a unique matrix experimental design that maximised the number of adjuvants screened while reducing the animal usage. Macaques were immunised by the intranasal, sublingual and intrarectal routes with the model protein antigens keyhole limpet haemocyanin (KLH), β-galactosidase (β-Gal) and ovalbumin (OVA) in combination with the experimental adjuvants Poly(I:C), Pam3CSK4, chitosan, Thymic Stromal Lymphopoietin (TSLP), MPLA and R848 (Resiquimod). Of the routes used, only intranasal immunization with KLH and R848 induced a detectable antibody response. When compared to intramuscular immunization, intranasal administration gave slightly lower levels of antigen specific antibody in the plasma, but enhanced local responses. Following intranasal delivery of R848, we observed a mildly inflammatory response, but no difference to the control. From this we conclude that R848 is able to boost antibody responses to mucosally delivered antigen, without causing excess local inflammation.

Discrete partitioning of HIV-1 Env forms revealed by viral capture

Background

The structure of HIV-1 envelope glycoprotein (Env) is flexible and heterogeneous on whole virions. Although functional Env complexes are thought to require trimerization of cleaved gp41/gp120 heterodimers, variable processing can result in the potential incorporation of non-functional uncleaved proteins (gp160), non-trimeric arrangements of gp41/gp120 heterodimers, and gp120 depleted gp41 stumps. The potential distribution of functional and non-functional Env forms across replication-competent viral populations may have important implications for neutralizing and non-neutralizing antibody functions. This study applied an immuno-bead viral capture assay (VCA) to interrogate the potential distribution (heterologous vs homologous) of functional and non-functional forms of virion associated Env.

Results

The VCA revealed a significant association between depletion of infectious virions and virion Env incorporation, but not between infectivity and p24-gag. Three distinct subpopulations of virions were identified within pools of genetically homogenous viral particles. Critically, a significant subpopulation of infectious virions were exclusively captured by neutralizing antibodies (nAbs) indicative of a homologous distribution of functional trimeric Env forms. A second infectious subpopulation bound both neutralizing and non-neutralizing antibodies (nnAbs) representative of a heterologous distribution of Env forms, while a third non-infectious subpopulation was predominantly bound by nnAbs recognizing gp41 stumps.

Conclusions

The observation that a distinct and significant subpopulation of infectious virions is exclusively captured by neutralizing antibodies has important implications for understanding antibody binding and neutralization, as well as other antibody effector functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-015-0207-z) contains supplementary material, which is available to authorized users.

Aggregate complexes of HIV-1 induced by multimeric antibodies

Background

Antibody mediated viral aggregation may impede viral transfer across mucosal surfaces by hindering viral movement in mucus, preventing transcytosis, or reducing inter-cellular penetration of epithelia thereby limiting access to susceptible mucosal CD4 T cells and dendritic cells. These functions may work together to provide effective immune exclusion of virus from mucosal tissue; however little is known about the antibody characteristics required to induce HIV aggregation. Such knowledge may be critical to the design of successful immunization strategies to facilitate viral immune exclusion at the mucosal portals of entry.

Results

The potential of neutralizing and non-neutralizing IgG and IgA monoclonals (mAbs) to induce HIV-1 aggregation was assessed by Dynamic light scattering (DLS). Although neutralizing and non-neutralizing IgG mAbs and polyclonal HIV-Ig efficiently aggregated soluble Env trimers, they were not capable of forming viral aggregates. In contrast, dimeric (but not monomeric) IgA mAbs induced stable viral aggregate populations that could be separated from uncomplexed virions. Epitope specificity influenced both the degree of aggregation and formation of higher order complexes by dIgA. IgA purified from serum of uninfected RV144 vaccine trial responders were able to efficiently opsonize viral particles in the absence of significant aggregation, reflective of monomeric IgA.

Conclusions

These results collectively demonstrate that dIgA is capable of forming stable viral aggregates providing a plausible basis for testing the effectiveness of aggregation as a potential protection mechanism at the mucosal portals of viral entry.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-014-0078-8) contains supplementary material, which is available to authorized users.

Dynamic electrophoretic fingerprinting of the HIV-1 envelope glycoprotein

BACKGROUND

Interactions between the HIV-1 envelope glycoprotein (Env) and its primary receptor CD4 are influenced by the physiological setting in which these events take place. In this study, we explored the surface chemistry of HIV-1 Env constructs at a range of pH and salinities relevant to mucosal and systemic compartments through electrophoretic mobility (EM) measurements. Sexual transmission events provide a more acidic environment for HIV-1 compared to dissemination and spread of infection occurring in blood or lymph node. We hypothesize functional, trimeric Env behaves differently than monomeric forms.

RESULTS

The dynamic electrophoretic fingerprint of trimeric gp140 revealed a change in EM from strongly negative to strongly positive as pH increased from that of the lower female genital tract (pHx) to that of the blood (pHy). Similar findings were observed using a trimeric influenza Haemagglutinin (HA) glycoprotein, indicating that this may be a general attribute of trimeric viral envelope glycoproteins. These findings were supported by computationally modeling the surface charge of various gp120 and HA crystal structures. To identify the behavior of the infectious agent and its target cells, EM measurements were made on purified whole HIV-1 virions and primary T-lymphocytes. Viral particles had a largely negative surface charge, and lacked the regions of positivity near neutral pH that were observed with trimeric Env. T cells changed their surface chemistry as a function of activation state, becoming more negative over a wider range of pH after activation. Soluble recombinant CD4 (sCD4) was found to be positively charged under a wide range of conditions. Binding studies between sCD4 and gp140 show that the affinity of CD4-gp140 interactions depends on pH.

CONCLUSIONS

Taken together, these findings allow a more complete model of the electrochemical forces involved in HIV-1 Env functionality. These results indicate that the influence of the localized environment on the interactions of HIV with target cells are more pronounced than previously appreciated. There is differential chemistry of trimeric, but not monomeric, Env under conditions which mimic the mucosa compared to those found systemically. This should be taken into consideration during design of immunogens which targets virus at mucosal portals of entry.

Factors preventing African Americans from seeking early intervention in the treatment of ischemic strokes

The most widely advocated drug that has been developed to decrease and possibly reverse the crippling effect of stroke is recombinant tissue plasminogen activator (rt-PA). In the treatment of ischemic stroke, rt-PA must be administered within the first 3 hr after the onset of symptoms for optimal efficacy and avoidance of life-threatening cerebral hemorrhage. This study sought to determine whether African-American stroke victims presented for treatment within the first 3 hr. In the study, we identified some of the more common reasons for the lack of prompt presentation. A prospective survey of 103 randomly selected acute stroke patients was performed. We found that less than half of this population sought assistance in the emergency department in time to take advantage of rt-PA therapy. When confronted with symptoms that were consistent with acute stroke, many patients either chose to ignore them or thought that they were experiencing transient phenomena. Three factors were identified as possible reasons for the lack of prompt response: (a) a lack of information about available treatment options; (b) the inability to recognize the early warning signs of an impending stroke; and (c) denial of illness. This study may help to evolve strategies that must be instituted to better educate the community about the early recognition of stroke and available treatment alternatives.

Non-polarizable collagen in dermatofibrosarcoma protuberans: a useful diagnostic aid

The stroma in dermatofibrosarcoma protuberans (DFSP) stains with trichrome, but is not polarizable (birefringent, doubly refractile). The usefulness of polarizing neoplastic stroma as a diagnostic aid in distinguishing DFSP from dermatofibroma and fibromatosis was evaluated. Forty cases of dermatofibroma of all types, 12 cases of dermal fibromatosis, and 15 cases of DFSP were examined. None of DFSPs contained polarizable collagen, whereas 11 of the 12 (92%) fibromatoses and 35 of the 40 (88%) dermatofibromas did. Of the 5 dermatofibromas that did not polarize, all were composed primarily of round to polyhedral histiocytic cells, including foam cells, frequently surrounding small obliterated capillaries. Although not pathognomonic, the presence of nonpolarizable collagen appears to be an additional histological marker useful in differentiating DFSP from dermatofibroma and fibromatosis.

Increased androgen binding in keloids: a preliminary communication

Sex hormone binding protein analyses were performed on six keloids, the adjacent skin, and on six simple scars. A high level of androgen binding (510 to 1149 Fm/mg of cytosol protein) was found in the keloids. The estrogen and progesterone binding activities were low. Para-keloid tissues were found to have androgen binding of 177 to 476 Fm/mg of cytosol protein. Once again, estrogen and progesterone binding activities were low. In six simple scars, androgen binding was less than 1/10 of that found in the keloids (37 to 60 Fm/mg of cytosol protein); estrogen and progesterone binding was so low that it was almost undetectable. We believe this data suggests that localized hyperandrogen metabolism may play a causal or at least contributory role in the pathogenesis of keloids.

Cutaneous histiocytoid hemangioma

Three cases of Kimura's disease or angiolymphoid hyperplasia with eosinophilia without the characteristic inflammatory infiltrate are reported. These unusual variants support the contention that the common denominator of these vascular lesions, whether they occur in the skin or (more rarely) in extracutaneous sites, is a histiocytoid endothelial cell. Since the composition of the associated inflammatory cell infiltrate is highly variable, a more appropriate term for these lesions is "histiocytoid hemangioma."

Immunoperoxidase staining of cytoplasmic immunoglobulins. A diagnostic aid in distinguishing cutaneous reactive lymphoid hyperplasia from malignant lymphoma

A method for staining cytoplasmic immunoglobulins utilizing an immunoperoxidase technic on paraffin-embedded tissue was used to examine two cutaneous lesions. On routine hematoxylin-eosin staining, one lesion exhibited what appeared to be a mixed population of mature cell types and was therefore interpreted as reactive lymphoid hyperplasia, whereas the other lesion showed a uniform population of immature cells and was interpreted as a malignant lymphoma. Immunoperoxidase staining supported these interpretations since the reactive lesion showed polyclonal IgG lambda and kappa staining, and the malignant lymphoma monoclonal staining with IgG lambda. In selected material, immunoperoxidase staining can distinguish a truly mixed population of cell types (probably benign) from a monoclonal population of cells exhibiting either uniform or mixed morphologic configurations associated with B lymphocyte transformation (probably malignant).

Intraepithelial elastic fibers and intracytoplasmic glycogen: diagnostic aids in differentiating keratoacanthoma from squamous cell carcinoma

A significant statistical difference was found between the incidence of intraepithelial elastic fibers in keratoacanthoma and squamous cell carcinoma arising in actinic keratosis (P < 0.001). There was no significant difference when keratoacanthoma was compared to adenoid squamous cell carcinoma (P = 0.13) and de novo squamous cell carcinoma (P = 0.73). However, in keratoacanthoma intraepithelial elastic fibers were found in areas of pseudoepitheliomatous hyperplasia and in the central keratin plug, as well as in areas of infiltrating, peripheral keratinocytes. In adenoid squamous cell carcinoma and de novo squamous cell carcinoma, the intraepithelial elastic fibers were found only in areas of atypical epithelial cells at the margin of the neoplasm. Intracytoplasmic glycogen was found to be statistically more abundant in keratoacanthoma than in squamous cell carcinoma arising in actinic keratosis (P < 0.001), adenoid squamous cell carcinoma (P < 0.001), and in de novo squamous cell carcinoma (P < 0.001)