CCL28 induces mucosal homing of HIV-1-specific IgA-secreting plasma cells in mice immunized with HIV-1 virus-like particles

CCL28 Enhances HSV-2 gB-Specific Th1-Polarized Immune Responses against Lethal Vaginal Challenge in Mice

Plasmid DNA (pDNA) represents a promising “genetic vaccine platform” capable of overcoming major histocompatibility complex barriers. We previously demonstrated that low-to-moderate doses of mucosae-associated epithelial chemokine (MEC or CCL28) as an immunomodulatory adjuvant can trigger effective and long-lasting systemic and mucosal HSV-2 gD-specific immune responses, whereas mice immunized with gD in combination with high-dose CCL28 showed toxicity and lost their immunoprotective effects after lethal HSV-2 challenge. The exact causes underlying high-dose, CCL28-induced lesions remain unknown. In an intramuscularly immunized mouse model, we investigated the immune-enhancement mechanisms of low-dose CCL28 as a molecular adjuvant combined with the relatively weak immunogen HSV-2 gB. Compared with the plasmid gB antigen group, we found that a low-dose of plasmid CCL28 (pCCL28) codelivered with pgB induced increased levels of gB-specific serum IgG and vaginal fluid IgA, serum neutralizing antibodies (NAb), Th1-polarized IgG2a, and cytokine IL-2 (>5-fold). Furthermore, low-dose pCCL28 codelivery with pgB enhanced CCL28/CCR10-axis responsive CCR10− plus CCR10+ B-cell (~1.2-fold) and DC pools (~4-fold) in the spleen, CCR10− plus CCR10+ T-cell pools (~2-fold) in mesenteric lymph nodes (MLNs), and the levels of IgA-ASCs in colorectal mucosal tissues, leading to an improved protective effect against a lethal dose of HSV-2 challenge. Findings in this study provide a basis for the development of CCL28-adjuvant vaccines against viral mucosal infections.

A review of mass spectrometry-based analyses to understand COVID-19 convalescent plasma mechanisms of action

The spread of coronavirus disease 2019 (COVID‐19) viral pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has become a worldwide pandemic claiming several thousands of lives worldwide. During this pandemic, several studies reported the use of COVID‐19 convalescent plasma (CCP) from recovered patients to treat severely or critically ill patients. Although this historical and empirical treatment holds immense potential as a first line of response against eventual future unforeseen viral epidemics, there are several concerns regarding the efficacy and safety of this approach. This critical review aims to pinpoint the possible role of mass spectrometry‐based analysis in the identification of unique molecular component proteins, peptides, and metabolites of CCP that explains the therapeutic mechanism of action against COVID‐19. Additionally, the text critically reviews the potential application of mass spectrometry approaches in the search for novel plasma biomarkers that may enable a rapid and accurate assessment of the safety and efficacy of CCP. Considering the relative low‐cost value involved in the CCP therapy, this proposed line of research represents a tangible scientific challenge that will be translated into clinical practice and help save several thousand lives around the world, specifically in low‐ and middle‐income countries.

Interplay of immune and kidney resident cells in the formation of tertiary lymphoid structures in lupus nephritis

Kidney involvement confers significant morbidity and mortality in patients with systemic lupus erythematosus (SLE). The pathogenesis of lupus nephritis (LN) involves diverse mechanisms instigated by elements of the autoimmune response which alter the biology of kidney resident cells. Processes in the glomeruli and in the interstitium may proceed independently albeit crosstalk between the two is inevitable. Podocytes, mesangial cells, tubular epithelial cells, kidney resident macrophages and stromal cells with input from cytokines and autoantibodies present in the circulation alter the expression of enzymes, produce cytokines and chemokines which lead to their injury and damage of the kidney. Several of these molecules can be targeted independently to prevent and reverse kidney failure. Tertiary lymphoid structures with true germinal centers are present in the kidneys of patients with lupus nephritis and have been increasingly recognized to associate with poorer renal outcomes. Stromal cells, tubular epithelial cells, high endothelial vessel and lymphatic venule cells produce chemokines which enable the formation of structures composed of a T-cell-rich zone with mature dendritic cells next to a B-cell follicle with the characteristics of a germinal center surrounded by plasma cells. Following an overview on the interaction of the immune cells with kidney resident cells, we discuss the cellular and molecular events which lead to the formation of tertiary lymphoid structures in the interstitium of the kidneys of mice and patients with lupus nephritis. In parallel, molecules and processes that can be targeted therapeutically are presented.

CCL19 and CCL28 Assist Herpes Simplex Virus 2 Glycoprotein D To Induce Protective Systemic Immunity against Genital Viral Challenge

An effective HSV-2 vaccine should induce antigen (Ag)-specific immune responses against viral mucosal infection. This study reveals that chemokine CCL19 or CCL28 enhanced HSV-2 glycoprotein D ectodomain (gD-306aa)-induced immune responses against vaginal virus challenge.

Potent systemic immunity is important for recalled mucosal immune responses, but in the defense against mucosal viral infections, it usually remains low at mucosal sites. Based on our previous findings that enhanced immune responses can be achieved by immunization with an immunogen in combination with a molecular adjuvant, here we designed chemokine-antigen (Ag) fusion constructs (CCL19- or CCL28-herpes simplex virus 2 glycoprotein D [HSV-2 gD]). After intramuscular (i.m.) immunization with different DNA vaccines in a prime and boost strategy, BALB/c mice were challenged with a lethal dose of HSV-2 through the genital tract. Ag-specific immune responses and chemokine receptor-specific lymphocytes were analyzed to determine the effects of CCL19 and CCL28 in strengthening humoral and cellular immunity. Both CCL19 and CCL28 were efficient in inducing long-lasting HSV-2 gD-specific systemic immunity. Compared to CCL19, less CCL28 was required to elicit HSV-2 gD-specific serum IgA responses, Th1- and Th2-like responses of immunoglobulin (Ig) subclasses and cytokines, and CCR3⁺ T cell enrichment (>8.5-fold) in spleens. These findings together demonstrate that CCL28 tends to assist an immunogen to induce more potently protective immunity than CCL19. This work provides information for the application potential of a promising vaccination strategy against mucosal infections caused by HSV-2 and other sexually transmitted viruses.

IMPORTANCE An effective HSV-2 vaccine should induce antigen (Ag)-specific immune responses against viral mucosal infection. This study reveals that chemokine CCL19 or CCL28 enhanced HSV-2 glycoprotein D ectodomain (gD-306aa)-induced immune responses against vaginal virus challenge. In addition to eliciting robust humoral immune responses, the chemokine-Ag fusion construct also induced Th1- and Th2-like immune responses characterized by the secretion of multiple Ig subclasses and cytokines that were able to be recalled after HSV-2 challenge, while CCL28 appeared to be more effective than CCL19 in promoting gD-elicited immune responses as well as the migration of T cells to secondary lymph tissues. Of importance, both CCL19 and CCL28 significantly facilitated gD to induce protective mucosal immune responses in the genital tract. The above-described findings together highlight the potential of CCL19 or CCL28 in combination with gD as a vaccination strategy to control HSV-2 infection.

Parenterally Administered Porcine Epidemic Diarrhea Virus-Like Particle-Based Vaccine Formulated with CCL25/28 Chemokines Induces Systemic and Mucosal Immune Protectivity in Pigs

Generation of a safe, economical, and effective vaccine capable of inducing mucosal immunity is critical for the development of vaccines against enteric viral diseases. In the current study, virus-like particles (VLPs) containing the spike (S), membrane (M), and envelope (E) structural proteins of porcine epidemic diarrhea virus (PEDV) expressed by the novel polycistronic baculovirus expression vector were generated. The immunogenicity and protective efficacy of the PEDV VLPs formulated with or without mucosal adjuvants of CCL25 and CCL28 (CCL25/28) were evaluated in post-weaning pigs. While pigs intramuscularly immunized with VLPs alone were capable of eliciting systemic anti-PEDV S-specific IgG and cellular immunity, co-administration of PEDV VLPs with CCL25/28 could further modulate the immune responses by enhancing systemic anti-PEDV S-specific IgG, mucosal IgA, and cellular immunity. Upon challenge with PEDV, both VLP-immunized groups showed milder clinical signs with reduced fecal viral shedding as compared to the control group. Furthermore, pigs immunized with VLPs adjuvanted with CCL25/28 showed superior immune protection against PEDV. Our results suggest that VLPs formulated with CCL25/28 may serve as a potential PEDV vaccine candidate and the same strategy may serve as a platform for the development of other enteric viral vaccines.

Host Transcriptional Response to Persistent Infection with a Live-Attenuated Porcine Reproductive and Respiratory Syndrome Virus Strain

Both virulent and live-attenuated porcine reproductive and respiratory syndrome virus (PRRSV) strains can establish persistent infection in lymphoid tissues of pigs. To investigate the mechanisms of PRRSV persistence, we performed a transcriptional analysis of inguinal lymphoid tissue collected from pigs experimentally infected with an attenuated PRRSV strain at 46 days post infection. A total of 6404 differentially expressed genes (DEGs) were detected of which 3960 DEGs were upregulated and 2444 DEGs were downregulated. Specifically, genes involved in innate immune responses and chemokines and receptors associated with T-cell homing to lymphoid tissues were down regulated. As a result, homing of virus-specific T-cells to lymphoid tissues seems to be ineffective, evidenced by the lower frequencies of virus-specific T-cell in lymphoid tissue than in peripheral blood. Genes associated with T-cell exhaustion were upregulated. Likewise, genes involved in the anti-apoptotic pathway were upregulated. Collectively, the data suggested that the live-attenuated PRRSV strain establishes a pro-survival microenvironment in lymphoid tissue by suppressing innate immune responses, T-cell homing, and preventing cell apoptosis.

CCR10 expression is required for the adjuvant activity of the mucosal chemokine CCL28 when delivered in the context of an HIV-1 Env DNA vaccine

An effective prophylactic vaccine targeting HIV must induce a robust humoral response and must direct the bulk of this response to the mucosa-the primary site of HIV transmission. The chemokine, CCL28, is secreted by epithelial cells at mucosal surfaces and recruits' cells expressing its receptor CCR10. CCR10 is predominantly expressed by IgA + ASCs. We hypothesized that co-immunization with plasmid DNA encoding consensus envelope antigens with plasmid-encoded CCL28 would enhance anti-HIV IgA responses at mucosal surfaces. Indeed, animals receiving pCCL28 and pEnvA/C had significantly increased HIV-specific IgA in fecal extract. Surprisingly, CCL28 co-immunization induced a significant increase in anti-HIV IgG in the serum in mice compared to those receiving pEnvA/C alone. These robust antibody responses were not associated with changes in the frequency of germinal center B cells but depended upon the expression of CCR10, as these responses we abolished in CCR10-deficient animals. Finally, immunization with CCL28 led to increased frequencies in HIV-specific CCR10 + and CCR10 + IgA + B cells in the small intestine and Peyer's patches of vaccinated animals as compared to those receiving pEnvA/C alone. These data indicate that CCL28 administration can enhance antigen-specific humoral responses systemically and at mucosal surfaces.

Intramuscular Immunization with Chemokine-Adjuvanted Inactive Porcine Epidemic Diarrhea Virus Induces Substantial Protection in Pigs

Intramuscular (IM) immunization is generally considered incapable of generating a protective mucosal immune response. In the swine industry, attempts to develop a safe and protective vaccine for controlling porcine epidemic diarrhea (PED) via an IM route of administration have been unsuccessful. In the present study, porcine chemokine ligand proteins CCL25, 27, and 28 were constructed and stably expressed in the mammalian expression system. IM co-administration of inactivated PEDV (iPEDV) particles with different CC chemokines and Freund’s adjuvants resulted in recruiting CCR9+ and/or CCR10+ inflammatory cells to the injection site, thereby inducing superior systemic PEDV specific IgG, fecal IgA, and viral neutralizing antibodies in pigs. Moreover, pigs immunized with iPEDV in combination with CCL25 and CCL28 elicited substantial protection against a virulent PEDV challenge. We show that the porcine CC chemokines could be novel adjuvants for developing IM vaccines for modulating mucosal immune responses against mucosal transmissible pathogens in pigs.

Mucosal Vaccine Approaches for Prevention of HIV and SIV Transmission

Optimal protective immunity to HIV will likely require that plasma cells, memory B cells and memory T cells be stationed in mucosal tissues at portals of viral entry. Mucosal vaccine administration is more effective than parenteral vaccine delivery for this purpose. The challenge has been to achieve efficient vaccine uptake at mucosal surfaces, and to identify safe and effective adjuvants, especially for mucosally administered HIV envelope protein immunogens. Here, we discuss strategies used to deliver potential HIV vaccine candidates in the intestine, respiratory tract, and male and female genital tract of humans and nonhuman primates. We also review mucosal adjuvants, including Toll-like receptor agonists, which may adjuvant both mucosal humoral and cellular immune responses to HIV protein immunogens.

Influenza virus-like particles composed of conserved influenza proteins and GPI-anchored CCL28/GM-CSF fusion proteins enhance protective immunity against homologous and heterologous viruses

Influenza viruses cause significant morbidity and mortality and pose a substantial threat to public health. Vaccination represents the principle means of preventing influenza virus infection. Current vaccine approaches are hindered by the need to routinely reformulate vaccine compositions in an effort to account for the progressive antigenic changes that occur as influenza viruses circulate in the human population. In this study, we evaluated chimeric virus-like particle (cVLP) vaccines containing conserved elements of influenza proteins (HL5M2e (HA stem gene with 5M2e gene inserted) and NP), with or without glycosylphosphatidylinositol-anchored CCL28 (GPI-CCL28) and/or GM-CSF (GPI-GM-CSF) fusion proteins as molecular adjuvants. cVLPs elicited strong humoral and cellular immune responses against homologous and heterologous viruses, and improved survival following lethal challenge with both homologous and heterologous viruses. Inclusion of GPI-anchored adjuvants in cVLP vaccines augmented the generation of influenza-specific humoral and cellular immune responses in mice in comparison to the non-adjuvanted cVLP vaccines. VLPs containing GPI-anchored adjuvants reduced morbidity and improved survival to lethal challenge with homologous and heterologous influenza viruses. This work suggests that VLP vaccines incorporating conserved influenza virus proteins and GPI-anchored molecular adjuvants may serve as a platform for a broadly protective "universal" influenza vaccine.

Chemokines and receptors in intestinal B lymphocytes

Recent studies indicate that chemoattractant cytokines (chemokines) and their receptors modulate intestinal B lymphocytes in different ways, including regulating their maturity and differentiation in the bone marrow and homing to intestinal target tissues. Here, we review several important chemokine/chemokine receptor axes that guide intestinal B cells, focusing on the homing and migration of IgA antibody-secreting cells (IgA-ASCs) to intestinal-associated lymphoid tissues. We describe the selective regulation of these chemokine axes in coordinating the IgA-ASC trafficking in intestinal diseases. Finally, we discuss the role of B cells as chemokine producers serving dual roles in regulating the mucosal immune microenvironment.

Applications of chemokines as adjuvants for vaccine immunotherapy

Vaccinations are expected to aid in building immunity against pathogens. This objective often requires the addition of an adjuvant with certain vaccine formulations containing weakly immunogenic antigens. Adjuvants can improve antigen processing, presentation, and recognition, thereby improving the immunogenicity of a vaccine by simulating and eliciting an immune response. Chemokines are a group of small chemoattractant proteins that are essential regulators of the immune system. They are involved in almost every aspect of tumorigenesis, antitumor immunity, and antimicrobial activity and also play a critical role in regulating innate and adaptive immune responses. More recently, chemokines have been used as vaccine adjuvants due to their ability to modulate lymphocyte development, priming and effector functions, and enhance protective immunity. Chemokines that are produced naturally by the body's own immune system could serve as potentially safer and more reliable adjuvant options versus synthetic adjuvants. This review will primarily focus on chemokines and their immunomodulatory activities against various infectious diseases and cancers.

CCL28 chemokine: An anchoring point bridging innate and adaptive immunity

Chemokines are an extensive family of small proteins which, in conjunction with their receptors, guide the chemotactic activity of various immune cells throughout the body. CCL28, β- or CC chemokine, is involved in the host immunity at various epithelial and mucosal linings. The unique roles of CCL28 in several facets of immune responses have attracted considerable attention and may represent a promising approach to combat various infections. CCL28 displays a broad spectrum of antimicrobial activity against gram-negative and gram-positive bacteria, as well as fungi. Here, we will summarize various research findings regarding the antimicrobial activity of CCL28 and the relevant mechanisms behind it. We will explore how the structure of CCL28 is involved with this activity and how this function may have evolved. CCL28 displays strong homing capabilities for B and T cells at several mucosal and epithelial sites, and orchestrates the trafficking and functioning of lymphocytes. The chemotactic and immunomodulatory features of CCL28 through the interactions with its chemokine receptors, CCR10 and CCR3, will also be discussed in detail. Thus, in this review, we emphasize the dual properties of CCL28 and suggest its role as an anchoring point bridging the innate and adaptive immunity.

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Chemokines play a vital role in cell migration in response to a chemical gradient by a process known as chemotaxis.

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CCL28 is a β- or CC chemokine that is involved in host immunity through the interactions with its chemokine receptors, CCR10 and CCR3.

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CCL28 is constitutively expressed in a wide variety of tissues including exocrine glands and is inducible through inflammation and infections.

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CCL28 has been shown to exhibit broad spectrum antimicrobial activity against gram-positive bacteria, gram-negative bacteria, and some fungi.

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CCL28 displays strong homing capabilities for B and T cells and orchestrates the trafficking and functioning of lymphocytes.

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In this review, we emphasize the antimicrobial and immunomodulatory feature of CCL28 and its role as bridge between innate and adaptive immunity.

Membrane-anchored CCL20 augments HIV Env-specific mucosal immune responses

Background

Induction of broad immune responses at mucosal site remains a primary goal for most vaccines against mucosal pathogens. Abundance of evidence indicates that the co-delivery of mucosal adjuvants, including cytokines, is necessary to induce effective mucosal immunity. In the present study, we set out to evaluate the role of a chemokine, CCL20, as an effective mucosal adjuvant for HIV vaccine.

Methods

To evaluate the role of CCL20 as a potent adjuvant for HIV vaccine, we examined its effects on antigen-specific antibody responses, level of antibody-secreting cells, cytokine production and intestinal homing of plasma cells in vaccine immunized mice.

Results

CCL20-incorporated VLP administered by mucosal route (intranasal (n = 10, p = 0.0085) or intravaginal (n = 10, p = 0.0091)) showed much higher potency in inducing Env-specific IgA antibody response than those administered by intramuscular route (n = 10). For intranasal administration, the HIV Env-specific IFN-γ(751 pg/ml), IL-4 (566 pg/ml), IL-5 (811 pg/ml) production and IgA-secreting plasma cells (62 IgA-secreting plasma cells/10⁶ cells) in mucosal lamina propria were significantly augmented in CCL20-incorporated VLP immunized mice as compared to those immunized with Env only VLPs (p = 0.0332, 0.0398, 0.033, 0.0302 for IFN-γ, IL-4, IL-5, and IgA-secreting plasma cells, respectively).

Further, anti-CCL20 mAb partially suppressed homing of Env-specific IgA ASCs into small intestine in mice immunized with CCL20-incorporated VLP by intranasal (62 decreased to 16 IgA- secreting plasma cells/10⁶ cells, p = 0.0341) or intravaginal (52 decreased to 13 IgA- secreting plasma cells/10⁶ cells, p = 0.0332) routes.

Conclusion

Our data indicated that the VLP-incorporated CCL20 can enhance HIV Env-specific immune responses in mice, especially those occurring in the mucosal sites. We also found that i.m. prime followed by mucosal boost is critical and required for CCL20 to exert its full function as an effective mucosal adjuvant. Therefore, co-incorporation of CCL20 into Env VLPs when combined with mucosal administration could represent a novel and promising HIV vaccine candidate.

Chimeric virus-like particles containing influenza HA antigen and GPI-CCL28 induce long-lasting mucosal immunity against H3N2 viruses

Influenza virus is a significant cause of morbidity and mortality, with worldwide seasonal epidemics. The duration and quality of humoral immunity and generation of immunological memory to vaccines is critical for protective immunity. In the current study, we examined the long-lasting protective efficacy of chimeric VLPs (cVLPs) containing influenza HA and GPI-anchored CCL28 as antigen and mucosal adjuvant, respectively, when immunized intranasally in mice. We report that the cVLPs induced significantly higher and sustainable levels of virus-specific antibody responses, especially IgA levels and hemagglutination inhibition (HAI) titers, more than 8-month post-vaccination compared to influenza VLPs without CCL28 or influenza VLPs physically mixed with sCCL28 (soluble) in mice. After challenging the vaccinated animals at month 8 with H3N2 viruses, the cVLP group also demonstrated strong recall responses. On day 4 post-challenge, we measured increased antibody levels, ASCs and HAI titers with reduced viral load and inflammatory responses in the cVLP group. The animals vaccinated with the cVLP showed 20% cross-protection against drifted (Philippines) and 60% protection against homologous (Aichi) H3N2 viruses. Thus, the results suggest that the GPI-anchored CCL28 induces significantly higher mucosal antibody responses, involved in providing long-term cross-protection against H3N2 influenza virus when compared to other vaccination groups.

Intradermal immunisation using the TLR3-ligand Poly (I:C) as adjuvant induces mucosal antibody responses and protects against genital HSV-2 infection

Development of vaccines able to induce mucosal immunity in the genital and gastrointestinal tracts is a major challenge to counter sexually transmitted pathogens such as HIV-1 and HSV-2. Herein, we showed that intradermal (ID) immunisation with sub-unit vaccine antigens (i.e., HIV-1 gp140 and HSV-2 gD) delivered with Poly(I:C) or CpG1668 as adjuvant induces long-lasting virus-specific immunoglobulin (Ig)-G and IgA antibodies in the vagina and feces. Poly(I:C)-supplemented sub-unit viral vaccines caused minimal skin reactogenicity at variance to those containing CpG1668, promoted a delayed-type hypersensitivity (DTH) to the vaccine and protected mice from genital and neurological symptoms after a lethal vaginal HSV-2 challenge. Interestingly, Poly(I:C_12U) (Ampligen), a Poly(I:C) structural analogue that binds to TLR3 but not MDA-5, promoted robust mucosal and systemic IgG antibodies, a weak skin DTH to the vaccine but not IgA responses and failed to confer protection against HSV-2 infection. Moreover, Poly(I:C) was far superior to Poly(I:C_12U) at inducing prompt and robust upregulation of IFNß transcripts in lymph nodes draining the injection site. These data illustrate that ID vaccination with glycoproteins and Poly(I:C) as adjuvant promotes long-lasting mucosal immunity and protection from genital HSV-2 infection, with an acceptable skin reactogenicity profile. The ID route thus appears to be an unexpected inductive site for mucosal immunity and anti-viral protection suitable for sub-unit vaccines. This works further highlights that TLR3/MDA5 agonists such as Poly(I:C) may be valuable adjuvants for ID vaccination against sexually transmitted diseases.

CCL4 as an adjuvant for DNA vaccination in a Her2/neu mouse tumor model

Chemokines are key regulators of both innate and adaptive immune responses. CCL4 (macrophage inflammatory protein-1β, MIP-1β) is a CC chemokine that has a broad spectrum of target cells including immature dendritic cells, which express the cognate receptor CCR5. We asked whether a plasmid encoding CCL4 is able to improve tumor protection and immune responses in a Her2/neu+ mouse tumor model. Balb/c mice were immunized twice intramuscularly with plasmid DNA on days 1 and 15. On day 25, a tumor challenge was performed with 2 × 10(5) syngeneic Her2/neu+ D2F2/E2 tumor cells. Different groups of mice were vaccinated with pDNA(Her2/neu) plus pDNA(CCL4), pDNA(Her2/neu), pDNA(CCL4) or mock vector alone. Our results show that CCL4 is able to (i) improve tumor protection and (ii) augment a TH1-polarized immune response against Her2/neu. Although Her2/neu-specific humoral and T-cell immune responses were comparable with that induced in previous studies using CCL19 or CCL21 as adjuvants, tumor protection conferred by CCL4 was inferior. Whether this is due to a different spectrum of (innate) immune cells, remains to be clarified. However, combination of CCL19/21 with CCL4 might be a reasonable approach in the future, particularly for DNA vaccination in Her2/neu+ breast cancer in the situation of minimal residual disease.

How can we design better vaccines to prevent HIV infection in women?

The human immunodeficiency virus (HIV) burden in women continues to increase, and heterosexual contact is now the most common route of infection worldwide. Effective protection of women against HIV-1 infection may require a vaccine specifically targeting mucosal immune responses in the female genital tract (FGT). To achieve this goal, a much better understanding of the immunology of the FGT is needed. Here we review the architecture of the immune system of the FGT, recent studies of potential methods to achieve the goal of mucosal protection in women, including systemic-prime, mucosal-boost, FGT-tropic vectors and immune response altering adjuvants. Advances in other fields that enhance our understanding of female genital immune correlates and the interplay between hormonal and immunological systems may also help to achieve protection of women from HIV infection.

A 12 week longitudinal study of microbial translocation and systemic inflammation in undernourished HIV-infected Zambians initiating antiretroviral therapy

Background

Undernourished, HIV-infected adults in sub-Saharan Africa have high levels of systemic inflammation, which is a risk factor for mortality and other adverse health outcomes. We hypothesized that microbial translocation, due to the deleterious effects of HIV and poor nutrition on intestinal defenses and mucosal integrity, contributes to heightened systemic inflammation in this population, and reductions in inflammation on antiretroviral therapy (ART) accompany reductions in translocation.

Methods

HIV-infected, Zambian adults with a body mass index <18.5 kg/m² were recruited for a pilot study to assess the relationships between microbial translocation and systemic inflammation over the first 12 weeks of ART. To assess microbial translocation we measured serum lipopolysaccharide binding protein (LBP), endotoxin core IgG and IgM, and soluble CD14, and to assess intestinal permeability we measured the urinary excretion of an oral lactulose dose normalized to urinary creatinine (Lac/Cr ratio). Linear mixed models were used to assess within-patient changes in these markers relative to serum C-reactive protein (CRP), tumor necrosis factor-α receptor 1 (TNF-α R1), and soluble CD163 over 12 weeks, in addition to relationships between variables independent of time point and adjusted for age, sex, and CD4+ count.

Results

Thirty-three participants had data from recruitment and at 12 weeks: 55% were male, median age was 36 years, and median baseline CD4+ count was 224 cells/μl. Over the first 12 weeks of ART, there were significant decreases in serum levels of LBP (median change -8.7 μg/ml, p = 0.01), TNF-α receptor 1 (-0.31 ng/ml, p < 0.01), and CRP (-3.5 mg/l, p = 0.02). The change in soluble CD14 level over 12 weeks was positively associated with the change in CRP (p < 0.01) and soluble CD163 (p < 0.01). Pooling data at baseline and 12 weeks, serum LBP was positively associated with CRP (p = 0.01), while endotoxin core IgM was inversely associated with CRP (p = 0.01) and TNF-α receptor 1 (p = 0.04). The Lac/Cr ratio was not associated with any serum biomarkers.

Conclusions

In undernourished HIV-infected adults in Zambia, biomarkers of increased microbial translocation are associated with high levels of systemic inflammation before and after initiation of ART, suggesting that impaired gut immune defenses contribute to innate immune activation in this population.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-521) contains supplementary material, which is available to authorized users.

Divergence of primary cognate B- and T-cell proliferative responses to subcutaneous and intravenous immunization with virus-like particles

A major advantage of virus-like particle (VLP) vaccines against HIV is their structural identity to wild-type viruses, ensuring that antigen-specific B-cells encounter the envelope protein in its natural conformation. For the induction of affinity-matured antibodies, the B-cells must also obtain help from T-cells that are restricted by linear epitopes. Using B- and T-cell transgenic mouse models, we compared the efficacy of modified HIV-VLPs delivered by subcutaneous and intravenous immunization to stimulate primary B- and T-cell proliferative responses in different lymphoid organs. VLPs containing an influenza virus hemagglutinin epitope within the HIV-Gag protein induced comparable primary cognate T-cell proliferative responses in the draining lymph node and the spleen, irrespective of the delivery route. In contrast, after subcutaneous immunization with HIV-Gag VLPs containing hen egg lysozyme (HEL) on their surface, the proliferative response of transgenic HEL-specific B-cells was restricted to the draining lymph nodes, while intravenous VLP immunization primarily induced a B-cell proliferative response in the spleen. In vitro co-culture experiments further revealed that the presentation of VLP-associated surface antigens by dendritic cells to cognate B-cells is inefficient. This is consistent with a direct triggering of the B-cell proliferative response by the VLPs and suggests that HIV VLPs may indeed be suitable to directly promote the expansion of B-cells specific for conformational epitopes that are unique to functionally-active Env spikes on the virion. Further investigations are warranted to explore potential differences in the quality and protective potency of HIV-specific antibody responses induced by the two routes.

A "prime-pull" vaccine strategy has a modest effect on local and systemic antibody responses to HIV gp140 in mice

One potential strategy for the prevention of HIV infection is to induce virus specific mucosal antibody that can act as an immune barrier to prevent transmission. The mucosal application of chemokines after immunisation, termed “prime-pull”, has been shown to recruit T cells to mucosal sites. We wished to determine whether this strategy could be used to increase B cells and antibody in the vaginal mucosa following immunisation with an HIV antigen. BALB/c mice were immunised intranasally with trimeric gp140 prior to vaginal application of the chemokine CCL28 or the synthetic TLR4 ligand MPLA, without antigen six days later. There was no increase in vaginal IgA, IgG or B cells following the application of CCL28, however vaginal application of MPLA led to a significant boost in antigen specific vaginal IgA. Follow up studies to investigate the effect of the timing of the “pull” stimulation demonstrated that when given 14 days after the initial immunisation MPLA significantly increased systemic antibody responses. We speculate that this may be due to residual inflammation prior to re-immunisation. Overall we conclude that in contrast to the previously observed effect on T cells, the use of “prime-pull” has only a modest effect on B cells and antibody.

Microbial translocation, immune activation, and HIV disease

The advent of combination antiretroviral therapy (cART) has significantly improved the prognosis of human immunodeficiency virus (HIV)-infected individuals. However, individuals treated long-term with cART still manifest increased mortality compared to HIV-uninfected individuals. This increased mortality is closely associated with inflammation, which persists in cART-treated HIV-infected individuals despite levels of plasma viremia below detection limits. Chronic, pathological immune activation is a key factor in progression to acquired immunodeficiency syndrome (AIDS) in untreated HIV-infected individuals. One contributor to immune activation is microbial translocation, which occurs when microbial products traverse the tight epithelial barrier of the gastrointestinal tract. Here we review the mechanisms underlying microbial translocation and its role in contributing to immune activation and disease progression in HIV infection.

Generation of antigen-specific immunity following systemic immunization with DNA vaccine encoding CCL25 chemokine immunoadjuvant

A significant hurdle in vaccine development for many infectious pathogens is the ability to generate appropriate immune responses at the portal of entry, namely mucosal sites. The development of vaccine approaches resulting in secretory IgA and mucosal cellular immune responses against target pathogens is of great interest and in general, requires live viral infection at mucosal sites. Using HIV-1 and influenza A antigens as models, we report here that a novel systemically administered DNA vaccination strategy utilizing co-delivery of the specific chemokine molecular adjuvant CCL25 (TECK) can produce antigen-specific immune responses at distal sites including the lung and mesenteric lymph nodes in mice. The targeted vaccines induced infiltration of cognate chemokine receptor, CCR9+/CD11c+ immune cells to the site of immunization. Furthermore, data shows enhanced IFN-λ secretion by antigen-specific CD3+/CD8+ and CD3+/CD4+ T cells, as well as elevated HIV-1-specific IgG and IgA responses in secondary lymphoid organs, peripheral blood, and importantly, at mucosal sites. These studies have significance for the development of vaccines and therapeutic strategies requiring mucosal immune responses and represent the first report of the use of plasmid co-delivery of CCL25 as part of the DNA vaccine strategy to boost systemic and mucosal immune responses following intramuscular injection.

CCR10 and its ligands in regulation of epithelial immunity and diseases

Epithelial tissues covering the external and internal surface of a body are constantly under physical, chemical or biological assaults. To protect the epithelial tissues and maintain their homeostasis, multiple layers of immune defense mechanisms are required. Besides the epithelial tissue-resident immune cells that provide the first line of defense, circulating immune cells are also recruited into the local tissues in response to challenges. Chemokines and chemokine receptors regulate tissue-specific migration, maintenance and functions of immune cells. Among them, chemokine receptor CCR10 and its ligands chemokines CCL27 and CCL28 are uniquely involved in the epithelial immunity. CCL27 is expressed predominantly in the skin by keratinocytes while CCL28 is expressed by epithelial cells of various mucosal tissues. CCR10 is expressed by various subsets of innate-like T cells that are programmed to localize to the skin during their developmental processes in the thymus. Circulating T cells might be imprinted by skin-associated antigen- presenting cells to express CCR10 for their recruitment to the skin during the local immune response. On the other hand, IgA antibody-producing B cells generated in mucosa-associated lymphoid tissues express CCR10 for their migration and maintenance at mucosal sites. Increasing evidence also found that CCR10/ligands are involved in regulation of other immune cells in epithelial immunity and are frequently exploited by epithelium-localizing or -originated cancer cells for their survival, proliferation and evasion from immune surveillance. Herein, we review current knowledge on roles of CCR10/ligands in regulation of epithelial immunity and diseases and speculate on related important questions worth further investigation.