[Show abstract][Hide abstract] ABSTRACT: INTRODUCTION: On April 2009, the Mexican Ministry of Health received notification of cases of severe pneumonia mostly affecting young healthy people; this was the beginning of the first influenza pandemic of the 21st century. The nature of the immune response to the influenza A(H1N1)2009 pandemic strain in Mexico at the beginning of the pandemic outbreak has not been completely defined. We describe the serological response to the 2009 pandemic influenza virus in paediatric patients with influenza-like illness, their household contacts (HHCs), and exposed health-care workers (HCWs) at the beginning of the pandemic outbreak in Mexico City.
METHODOLOGY: thirty pre-epidemic and 129 epidemic samples were collected and serum antibodies were measured against A(H1N1)2009 pandemic virus and two non-pandemic swine influenza viruses by an haemagglutination inhibition assay .
RESULTS: 91% (29/32) of the convalescence samples from confirmed patients had an antibody titre ≥ 10 (GMT 25), 63% (41/65) of the HHCs (GMT 12), 41% of HCWs (GMT 6) and 13% (4/30) of pre-epidemic samples (GMT 6) for the pandemic influenza virus. Of the 32 confirmed cases, 60% had an antibody titre ≥ 40 for the pandemic strain, 53% for the A/swine/Iowa(H1N1) virus (GMT 62) and 43% for the A/swine/Texas(H3N2) virus (GMT 66).
CONCLUSION: The antibody response to 2009 pandemic influenza virus was widespread in convalescence samples from patients with confirmed pandemic influenza infection but the GMT was below the protective titre. There was no evidence that antibodies to the swine influenza viruses had cross-protective effect against the 2009 pandemic influenza virus.
The Journal of Infection in Developing Countries 03/2015; 9(3):259-66. DOI:10.3855/jidc.5052. · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: INTRODUCTION:
On April 2009, the Mexican Ministry of Health received notification of cases of severe pneumonia mostly affecting young healthy people; this was the beginning of the first influenza pandemic of the 21st century. The nature of the immune response to the influenza A(H1N1)2009 pandemic strain in Mexico at the beginning of the pandemic outbreak has not been completely defined. We describe the serological response to the 2009 pandemic influenza virus in paediatric patients with influenza-like illness, their household contacts (HHCs), and exposed health-care workers (HCWs) at the beginning of the pandemic outbreak in Mexico City.
thirty pre-epidemic and 129 epidemic samples were collected and serum antibodies were measured against A(H1N1)2009 pandemic virus and two non-pandemic swine influenza viruses by an haemagglutination inhibition assay .
91% (29/32) of the convalescence samples from confirmed patients had an antibody titre ≥ 10 (GMT 25), 63% (41/65) of the HHCs (GMT 12), 41% of HCWs (GMT 6) and 13% (4/30) of pre-epidemic samples (GMT 6) for the pandemic influenza virus. Of the 32 confirmed cases, 60% had an antibody titre ≥ 40 for the pandemic strain, 53% for the A/swine/Iowa(H1N1) virus (GMT 62) and 43% for the A/swine/Texas(H3N2) virus (GMT 66).
The antibody response to 2009 pandemic influenza virus was widespread in convalescence samples from patients with confirmed pandemic influenza infection but the GMT was below the protective titre. There was no evidence that antibodies to the swine influenza viruses had cross-protective effect against the 2009 pandemic influenza virus.
The Journal of Infection in Developing Countries 03/2015; 9(3):259-66. DOI:10.3855/jidc.5052 · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Heat shock protein 70 (Hsp70) is an intracellular chaperone protein with regulatory and cytoprotective functions. Hsp70 can also be found in the extracellular milieu, as a result of active secretion or passive release from damaged cells. The role of extracellular Hsp70 is not fully understood. Some studies report that it activates monocytes, macrophages and dendritic cells through innate immune receptors (such as Toll-like receptors, TLRs), while others report that Hsp70 is a negative regulator of the inflammatory response. In order to address this apparent inconsistency, in this study we evaluated the response of human monocytes to a highly purified recombinant Hsp70.
Human peripheral blood monocytes were stimulated with Hsp70, alone or in combination with TLR agonists. Cytokines were quantified in culture supernatants, their mRNAs were measured by RT-PCR, and the binding of transcription factors was evaluated by electrophoretic mobility shift assay (EMSA). Kruskal-Wallis test or one-way or two-way ANOVA were used to analyze the data.
The addition of Hsp70 to TLR-activated monocytes down-regulated TNF-α as well as IL-6 levels. This effect was independent of a physical interaction between Hsp70 and TLR agonists; instead it resulted of changes at the TNF-α gene expression level. The decrease in TNF-α expression correlated with the binding of HSF-1 (heat shock transcription factor 1, a transcription factor activated in response to Hsp70) and CHBF (constitutive HSE-binding factor) to the TNF-α gene promoter.
Extracellular Hsp70 negatively regulates the production of pro-inflammatory cytokines of monocytes exposed to TLR agonists and contributes to dampen the inflammatory response.
Journal of Inflammation 07/2014; 11:19. DOI:10.1186/1476-9255-11-19 · 2.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electrical vagus nerve (VN) stimulation during sepsis attenuates tumor necrosis factor (TNF) production through the cholinergic anti-inflammatory pathway, which depends on the integrity of the VN and catecholamine production. To characterize the effect of electroacupuncture at ST36 (EA-ST36) on serum TNF, IL-6, nitrite, and HMGB1 levels and survival rates, based on VN integrity and catecholamine production, a sepsis model was induced in rats using cecal ligation and puncture (CLP). The septic rats were subsequently treated with EA-ST36 (CLP+ST36), and serum samples were collected and analyzed for cytokines levels. The serum TNF, IL-6, nitrite, and HMGB1 levels in the CLP+ST36 group were significantly lower compared with the group without treatment, the survival rates were significantly higher (
), and the acute organ injury induced by CLP was mitigated by EA-ST36; however, when subdiaphragmatic vagotomy was performed, the serum levels of TNF in the CLP+ST36 group did not show a significant difference compared with the group without electrostimulation, and, similarly, no significant difference in serum TNF levels was found under the pharmacological blockade of catecholamines. These results suggest that in rats with CLP sepsis models EA-ST36 reduces serum TNF levels through VN- and atecholamine-dependent mechanisms.
Evidence-based Complementary and Alternative Medicine 06/2014; 2014(5):451674. DOI:10.1155/2014/451674 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In trying to contribute to our knowledge on the biology of hematopoietic stem cells (HSC) and hematopoietic progenitor cells (HPC) from pediatric acute myeloid leukemia (AML), in the present study we analyzed the expression of four cell surface antigens relevant to human hematopoiesis-CD90, CD96, CD117, and CD123-in bone marrow from pediatric AML patients and normal control subjects.
CD34(+) CD38(-) cells (enriched for HSC) and CD34(+) CD38(+) cells (enriched for HPC) were resolved on the basis of CD34 and CD38 expression. Concomitantly, expression of CD90 and CD96 or CD117 and CD123 was assessed by multicolor flow cytometry in each cell population.
CD90 and CD117 were expressed in a low proportion of CD34(+) CD38(-) and CD34(+) CD38(+) cells and no significant differences were observed between normal marrow and AML at diagnosis. In contrast, CD96(+) cells and CD123(+) cells were found at significantly higher levels in both cell populations from AML at diagnosis, as compared to normal marrow. Levels of both cell surface markers after treatment remained higher than in normal marrow.
These results show an increased frequency of CD96(+) and CD123(+) cells within the CD34(+) cell population from pediatric AML; this is consistent with the findings reported previously for adult AML. Our study supports the notion that expression of such antigens should be explored for their use as markers for diagnosis and prognosis.
Archives of medical research 04/2014; 45. DOI:10.1016/j.arcmed.2014.04.001 · 2.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Remarkable progress has been made in characterizing factors controlling lineage fate decisions of primitive progenitors that initiate the lymphoid program in bone marrow. However, the understanding of neonatal/adult differences in environmental signals that influence differentiation pathway stability is still incomplete. Our recent findings suggest that Toll-like receptors (TLR) provide a mechanism for producing cells of the innate immune system from early stages of lymphoid development in mice. We now show that both, human early multi-lymphoid progenitors (MLP) and more differentiated lymphoid progenitors from normal adult bone marrow express TLR9. Furthermore, they respond to its ligation by up-regulating the expression of IL15Rβ (CD122) and accelerating the production of functional natural killer (NK)-like cells. Proliferation of the presumed equivalent progenitor cells from umbilical cord blood was stimulated by CpG-ODN or HSV, but the already robust NK cell formation was unchanged. This new information adds to other known differences between neonatal and adult lymphoid progenitors and suggests only the latter replenish innate NK-like cells in response to TLR agonists.
[Show abstract][Hide abstract] ABSTRACT: Previous anti-inflammatory strategies against sepsis, a leading cause of death in hospitals, had limited efficacy in clinical trials, in part because they targeted single cytokines and the experimental models failed to mimic clinical settings. Neuronal networks represent physiological mechanisms, selected by evolution to control inflammation, that can be exploited for the treatment of inflammatory and infectious disorders. Here, we report that sciatic nerve activation with electroacupuncture controls systemic inflammation and rescues mice from polymicrobial peritonitis. Electroacupuncture at the sciatic nerve controls systemic inflammation by inducing vagal activation of aromatic L-amino acid decarboxylase, leading to the production of dopamine in the adrenal medulla. Experimental models with adrenolectomized mice mimic clinical adrenal insufficiency, increase the susceptibility to sepsis and prevent the anti-inflammatory effects of electroacupuncture. Dopamine inhibits cytokine production via dopamine type 1 (D1) receptors. D1 receptor agonists suppress systemic inflammation and rescue mice with adrenal insufficiency from polymicrobial peritonitis. Our results suggest a new anti-inflammatory mechanism mediated by the sciatic and vagus nerves that modulates the production of catecholamines in the adrenal glands. From a pharmacological perspective, the effects of selective dopamine agonists mimic the anti-inflammatory effects of electroacupuncture and can provide therapeutic advantages to control inflammation in infectious and inflammatory disorders.
Nature medicine 02/2014; 20(3). DOI:10.1038/nm.3479 · 28.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Uncontrolled and intricate production of inflammatory factors is the characteristic feature of dengue infection. The triggering receptor expressed in myeloid cells-1 (TREM-1), expressed on the surface of monocytes and neutrophils, is capable of enhancing and regulating the inflammatory response via the production of different mediators in bacterial and viral infections. Here, both the expression of TREM-1 on human monocytes and neutrophils from peripheral blood of dengue infected individuals, as well as the levels of the soluble form of TREM-1 (sTREM-1) in the sera of these patients were compared against healthy controls. A significant reduction of TREM-1 expression was observed in neutrophils during the first days of infection, followed by a gradual recovery throughout the course of infection. Also, sera from DENV-infected patients exhibited significantly higher sTREM-1 levels than healthy individuals. The difference was more pronounced during the first 5 days after the onset of symptoms. These findings highlight the dynamic process of TREM-1 expression during DENV infection. We hypothesized that increment of free sTREM-1 could be a compensatory mechanism aiming to counteract the inflammatory process elicited during DENV infection.
[Show abstract][Hide abstract] ABSTRACT: Prolactin (PRL) plays an important role in modulating the immune response. In B cells, PRL enhances antibody production, including antibodies with self-specificity. In this study, our aims were to determine the level of PRL receptor expression during bone-marrow B-cell development and to assess whether the presence of high PRL serum concentrations influences absolute numbers of developing populations and disease outcome in lupus-prone murine models. We observed that the PRL-receptor is expressed in early bone-marrow B-cell; the expression in lupus-prone mice, which had the highest level of expression in pro-B cells and immature cells, differed from that in wild-type mice. These expression levels did not significantly change in response to hyperprolactinemia; however, populations of pro-B and immature cells from lupus-prone strains showed a decrease in the absolute numbers of cells with high PRL-receptor expression in response to PRL. Because immature self-reactive B cells are constantly being eliminated, we assessed the expression of survival factor BIRC5, which is more highly expressed in both pro-B and immature B-cells in response to PRL and correlates with the onset of disease. These results identify an important role of PRL in the early stages of the B-cell maturation process: PRL may promote the survival of self-reactive clones.
[Show abstract][Hide abstract] ABSTRACT: Acute lymphoblastic leukemia (ALL) is the most frequent malignancy of childhood. Substantial progress on understanding the cell hierarchy within ALL bone marrow (BM) has been recorded in the last few years, suggesting that both primitive cell fractions and committed lymphoid blasts with immature stem cell-like properties contain leukemia-initiating cells. Nevertheless, the biology of the early progenitors that initiate the lymphoid program remains elusive. The aim of the present study was to investigate the ability of lymphoid progenitors from B-cell precursor ALL BM to proliferate and undergo multilineage differentiation. By phenotype analyses, in vitro proliferation assays, and controlled culture systems, the lymphoid differentiation potentials were evaluated in BM primitive populations from B-cell precursor ALL pediatric patients. When compared to their normal counterparts, functional stem and progenitor cell contents were substantially reduced in ALL BM. Moreover, neither B nor NK or dendritic lymphoid-cell populations developed recurrently from highly purified ALL-lymphoid progenitors, and their proliferation and cell cycle status revealed limited proliferative capacity. Interestingly, a number of quiescence-associated transcription factors were elevated, including the transcriptional repressor Gfi-1, which was highly expressed in primitive CD34(+) cells. Together, our findings reveal major functional defects in the primitive hematopoietic component of ALL BM. A possible contribution of high levels of Gfi-1 expression in the regulation of the stem/progenitor cell biology is suggested.
[Show abstract][Hide abstract] ABSTRACT: PD-L1 expression plays a critical role in the impairment of T cell responses during chronic infections; however, the expression of PD-L1 on T cells during acute viral infections, particularly during the pandemic influenza virus (A(H1N1)pdm09), and its effects on the T cell response have not been widely explored. We found that A(H1N1)pdm09 virus induced PD-L1 expression on human dendritic cells (DCs) and T cells, as well as PD-1 expression on T cells. PD-L1 expression impaired the T cell response against A(H1N1)pdm09 by promoting CD8(+) T cell death and reducing cytokine production. Furthermore, we found increased PD-L1 expression on DCs and T cells from influenza-infected patients from the first and second 2009 pandemic waves in Mexico City. PD-L1 expression on CD8(+) T cells correlated inversely with T cell proportions in patients infected with A(H1N1)pdm09. Therefore, PD-L1 expression on DCs and T cells could be associated with an impaired T cell response during acute infection with A(H1N1)pdm09 virus.
[Show abstract][Hide abstract] ABSTRACT: Acute leukemias are the most frequent childhood malignancies worldwide and remain a leading cause of morbidity and mortality of relapsed patients. While remarkable progress has been made in characterizing genetic aberrations that may control these hematological disorders, it has also become clear that abnormalities in the bone marrow microenvironment might hit precursor cells and contribute to disease. However, responses of leukemic precursor cells to inflammatory conditions or microbial components upon infection are yet unexplored. Our previous work and increasing evidence indicate that Toll-like receptors (TLRs) in the earliest stages of lymphoid development in mice and humans provide an important mechanism for producing cells of the innate immune system. Using highly controlled co-culture systems, we now show that lymphoid precursors from leukemic bone marrow express TLRs and respond to their ligation by changing cell differentiation patterns. While no apparent contribution of TLR signals to tumor progression was recorded for any of the investigated diseases, the replenishment of innate cells was consistently promoted upon in vitro TLR exposure, suggesting that early recognition of pathogen-associated molecules might be implicated in the regulation of hematopoietic cell fate decisions in childhood acute leukemia.
[Show abstract][Hide abstract] ABSTRACT: Background
Entamoeba histolytica is a protozoan parasite that infects humans and causes amebiasis affecting developing countries. Phagocytosis of epithelial cells, erythrocytes, leucocytes, and commensal microbiota bacteria is a major pathogenic mechanism used by this parasite. A Toll/IL-1R/Resistance (TIR) domain-containing protein is required in phagocytosis in the social ameba Dictyostelium discoideum, an ameba closely related to Entamoeba histolytica in phylogeny. In insects and vertebrates, TIR domain-containing proteins regulate phagocytic and cell activation. Therefore, we investigated whether E. histolytica expresses TIR domain-containing molecules that may be involved in the phagocytosis of erythrocytes and bacteria.
Using in silico analysis we explored in Entamoeba histolytica databases for TIR domain containing sequences. After silencing TIR domain containing sequences in trophozoites by siRNA we evaluated phagocytosis of erythrocytes and bacteria.
We identified an E. histolytica thioredoxin containing a TIR-like domain. The secondary and tertiary structure of this sequence exhibited structural similarity to TIR domain family. Thioredoxin transcripts silenced in E. histolytica trophozoites decreased erythrocytes and E. coli phagocytosis.
TIR domain-containing thioredoxin of E. histolytica could be an important element in erythrocytes and bacteria phagocytosis.
[Show abstract][Hide abstract] ABSTRACT: The immune response to influenza vaccination in children with cancer is controversial. The objective of this study was to characterize the cellular and humoral immune responses to an influenza vaccine in children with cancer who were receiving chemotherapy. In this study, children with cancer, who were not previously immunized, received an influenza vaccine via intramuscular injection. Blood samples were obtained prior to and at 4 weeks after immunization. Antibodies were measured using a hemagglutination inhibition (HI) assay. Cell-mediated immunity was measured by specific lymphoproliferation with (3)H-thymidine incorporation and by measuring cell frequencies following staining with monoclonal antibodies (CD8, CD4, CD19, CD45RA and CD27) using flow cytometry following incubation with the influenza antigen for 5 days. Geometric mean titers (GMT), mean counts per minute (cpm), cell frequencies prior to and following vaccination and percentage patient responses were compared using the Mann-Whitney non-parametric U and Chi-square tests; where p<0.05 was considered to indicate a statistically significant result. A total of 56 children were included. Their mean age was 6.64±3.61 years. Acute lymphoblastic leukemia (ALL) was diagnosed in 75, solid tumors in 23 and lymphoma in 2% of the children. Subjects with titers ≥40 hemagglutination units (HU) increased from 43% prior to vaccination to 73% following vaccination (p=0.01), whereas the GMT increased from 31.35 [95% confidence interval (CI), 29-111] to 143.45 HU (95% CI, 284-640) following vaccination (p<0.001). An increase in CD45RA expression in CD8(+) T cells was observed following vaccination (p=0.01). An increase in CD27 expression was observed in the CD4/8-negative cell population stimulated with the influenza antigen following vaccination (p<0.05). No serious adverse effects were observed. An increase in the seropositivity rate and GMT values following influenza vaccination were also observed. Influenza immunization was well tolerated among these children with cancer and increased the humoral and cellular immune responses with the activation of probable lymphoid precursors.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Ex vivo expansion of hematopoietic stem and progenitor cells has become a priority in the experimental hematology arena. In this study we have obtained different hematopoietic cell populations from umbilical cord blood and simultaneously assessed their proliferation and expansion kinetics. Our main goal was to determine which one of these cell populations would be more suitable for clinical-grade ex vivo expansion. STUDY DESIGN AND METHODS: By using immunomagnetic-negative selection and cell sorting, five cell populations were obtained: unseparated mononuclear cells (MNCs; I); two lineage-negative cell populations, one enriched for CD34+ CD38+ cells (II) and the other enriched for CD34+ CD38- cells (III); and two CD34+ cell fractions purified by fluorescence-activated cell sorting, one containing CD34+ CD38+ cells (IV) and the other containing CD34+ CD38- cells (V). The kinetics of such populations were analyzed in both relative and absolute terms. RESULTS: No expansion was observed in Population I; in contrast, significant increments in the numbers of both progenitor and stem cells were observed in cultures of Populations II to V. Population V (reaching 12,800-fold increase in total cells; 1280-fold increase in CD34+ cells; 490-fold increase in colony-forming cells; and 12-fold increase in long-term culture-initiating cells) showed the highest proliferation and expansion potentials. CONCLUSION: Our study suggests that the cell fraction containing greater than 98% CD34+ CD38- cells would be the ideal one for large-scale ex vivo expansion; however, based on our data, it seems that, except for MNCs, all other cell populations could also be used as input cell fractions.
[Show abstract][Hide abstract] ABSTRACT: Prolactin is secreted from the pituitary gland and other organs, as well as by cells such as lymphocytes. Prolactin has an immunostimulatory effect and is associated with autoimmune diseases that are characterised by abnormal B cell activation, such as systemic lupus erythematosus (SLE). Our aim was to determine if different splenic B cell subsets express the prolactin receptor and if the presence of prolactin influences these B cell subsets and correlates with development of lupus.
Using real-time PCR and flow cytometry, we found that different subsets of immature (transitional) and mature (follicular, marginal zone) B cells express different levels of the prolactin receptor and are differentially affected by hyperprolactinaemia. We found that transitional B cells express the prolactin receptor at higher levels compared to mature B cells in C57BL/6 mice and the lupus-prone MRL/lpr and MRL mouse strains. Transitional-1 (T1) B cells showed a higher level of prolactin receptor expression in both MRL/lpr and MRL mice compared to C57BL/6 mice. Hyperprolactinaemia was induced using metoclopramide, which resulted in the development of early symptoms of SLE. We found that T1 B cells are the main targets of prolactin and that prolactin augments the absolute number of T1 B cells, which reflects the finding that this B cell subpopulation expresses the highest level of the prolactin receptor.
We found that all B cell subsets express the prolactin receptor but that transitional B cells showed the highest prolactin receptor expression levels. Hyperprolactinaemia in mice susceptible to lupus accelerated the disease and increased the absolute numbers of T1 and T3 B cells but not of mature B cells, suggesting a primary effect of prolactin on the early stages of B cell maturation in the spleen and a role of prolactin in B cell differentiation, contributing to SLE onset.
[Show abstract][Hide abstract] ABSTRACT: Among its many functions, prolactin (PRL) participates in immune responses and promotes the activation, differentiation and proliferation of T cells. However, the mechanisms by which PRL regulates regulatory T (T(reg)) cells are still unknown. Our goal was to determine whether PRL plays a role in T(reg) function. We measured the expression of PRL and its receptor in T(reg) and effector T (T(eff)) cells from 15 healthy individuals. We also evaluated the functional activity of T(reg) cells by examining proliferation and cytokine secretion in cells activated with anti-CD3/CD28 in the presence or absence of PRL. We report that T(reg) cells constitutively expressed PRL receptor, whereas T(eff) cells required stimulation with anti-CD3/CD28 to induce PRL receptor expression. Expression of PRL was constitutive in both populations. We found that the addition of PRL inhibited the suppressor effect (proliferation) mediated by T(reg) cells in vitro, reducing suppression from 37.4 to 13% when PRL was added to co-cultures of T(reg) and T(eff) cells (P<0.05). Cultures treated with PRL favoured a Th1 cytokine profile, with increased production of TNF and IFNγ. We report for the first time that PRL receptor expression was constitutive in T(reg) cells but not in T(eff) cells, which require stimulation to induce PRL receptor expression. PRL inhibited the suppressive function of T(reg) cells, apparently through the induced secretion of Th1 cytokines.
[Show abstract][Hide abstract] ABSTRACT: Virus-like particles (VLPs) can be rapidly developed from influenza virus genetic sequences in order to supply vaccine after the onset of a pandemic. The safety and immunogenicity of one or two doses of a recombinant A (H1N1) 2009 influenza VLP vaccine was evaluated in a two-stage, Phase 2, randomized, double-blind, placebo-controlled study conducted in 4563 healthy adults, 18-64 years of age, during the H1N1 2009 pandemic in Mexico. In Part A, 1013 subjects were randomized into four treatment groups (5 μg, 15 μg, or 45 μg hemagglutinin [HA] VLP vaccine or placebo) and vaccinated 21 days apart, with sera collected on Days 1, 14 and 36 for hemagglutination inhibition (HAI) testing. After review of safety and immunogenicity data from Part A, additional subjects were immunized with a single dose of 15 μg VLP vaccine (N=2537) or placebo (N=1011) and assessed for safety in Part B. Results showed the H1N1 2009 VLP vaccine was safe and well-tolerated. Systemic solicited events were similar between placebo and VLP vaccinated groups with no vaccine-related serious adverse events. Dose response trends for solicited local adverse events were observed, with higher incidences of local pain, swelling, tenderness, and redness reported in the higher VLP dose groups (15 μg and 45 μg) compared to the placebo and 5 μg VLP groups following both vaccinations. Although the majority of local AEs were mild in severity, a dose trend in events of moderate or greater severity was also noted for these solicited events. The VLP vaccine groups demonstrated robust HAI immune responses after a single vaccination, with high rates of seroprotection (≥ 40 HAI titer) in 82-92% of all subjects and in 64-85% of subjects who were seronegative at the time of immunization. HAI geometric mean titers (GMTs), geometric mean ratios (GMRs) and seroconversion rates were also all statistically higher in the VLP groups compared to placebo for both post-baseline time points. Based on these data, additional clinical trials are in development to evaluate influenza vaccine candidate antigens manufactured using Spodoptera frugiperda (Sf9)/baculovirus-based VLP technology.