Intranasal immunization protects against Acinetobacter baumannii-associated pneumonia in mice

Multidrug-resistant Acinetobacter baumannii has become an important causative agent of healthcare associated infections. Hospital- and community-acquired pneumonia is the most common clinical manifestation of A. baumannii infection worldwide and is often associated with high mortality. Most experimental vaccine studies to date have evaluated vaccines against systemic A. baumannii infections following systemic immunization. We recently demonstrated that a mouse model of respiratory A. baumannii infection using the strain LAC-4 results in disease progression that is similar to that observed in humans. Here we used this model in conjunction with an inactivated whole cell vaccine to evaluate the feasibility of developing protective mucosal vaccines against respiratory A. baumannii infection and to investigate the potential mechanism of protection of such vaccines. Our results showed that intranasal immunization with formalin-killed whole cells of the LAC-4 strain elicited mucosal and systemic antigen-specific immune responses, and protected mice against lethal intranasal or intraperitoneal challenges. Compared to naïve mice, immunized mice had significantly fewer bacteria in their lungs, and the pathogen was barely detectable in blood and spleens at 24 h post challenge, indicating the ability of immunized mice to control extrapulmonary dissemination of the pathogen. Mechanistic studies using gene-deficient mice, neutropenic mice, or passive immunization showed that B cells and neutrophils, but not FcRγ, played crucial roles in the protection against respiratory A. baumannii challenge of intranasally immunized mice whereas passive transfer of hyperimmune sera only prolonged the survival time of challenged mice by 48 h. These results provide immunological insights for the rational design of novel mucosal vaccines to protect against respiratory A. baumannii infection and demonstrate the feasibility to develop such vaccines.     

A lipopolysaccharide-free outer membrane vesicle vaccine protects against Acinetobacter baumannii infection

Outer membrane vesicles (OMVs) were isolated from an Acinetobacter strain deficient in lipopolysaccharide (LPS) due to a mutation in lpxD (IB010). Two immunizations with 10 µg of IB010 OMVs elicited total IgG, IgM, IgG1 and IgG2c titers similar to those observed after immunization with OMVs derived from the parental strain (ATCC 19606), and IB010 OMVs plus purified LPS. Immunization with IB010 OMVs resulted in significantly reduced post-infection spleen bacterial loads and serum IL-1β and IL-6 levels compared to control mice in a disseminated sepsis model. Mice immunized with 10 µg IB010 OMVs demonstrated significant, but partial, protection (75%) against infection, whereas mice immunized with ATCC 19606 OMVs or IB010 OMVs plus purified LPS were completely protected. Immunization of mice with 100 µg of IB010 OMVs completely protected mice from infection. This study demonstrates that LPS deficient A. baumannii produces OMVs, and that immunization with these OMVs elicits protective immunity against infection.     

Vaccination with a live attenuated Acinetobacter baumannii deficient in thioredoxin provides protection against systemic Acinetobacter infection

Multi-drug resistant Acinetobacter baumannii (MDR-Ab), an opportunistic pathogen associated with nosocomial and combat related infections, has a high mortality due to its virulence and limited treatment options. Deletion of the thioredoxin gene (TrxA) from a clinical isolate of MDR-Ab resulted in a 100-fold increase in 50% lethal dose (LD₅₀) in a systemic challenge murine model. Thus, we investigated the potential use of this attenuated strain as a live vaccine against MDR-Ab. Mice were vaccinated by subcutaneous (s.c.) injection of 2 × 10⁵ CFU of the ΔtrxA mutant, boosted 14 days later with an equivalent inoculum, and then challenged 30 days post-vaccination by i.p. injection with 10 LD₅₀ of the wild type (WT) Ci79 strain. Efficacy of vaccination was evaluated by monitoring MDR-Ab specific antibody titers and cytokine production, observing pathology and organ burdens after WT challenge, and measuring levels of serum pentraxin-3, a molecular correlate of A. baumannii infection severity, before and after challenge. Mice vaccinated with ΔtrxA were fully protected against the lethal challenge of WT. However, minimal immunoglobulin class switching was observed with IgM predominating. Spleens harvested from vaccinated mice exhibited negligible levels of IL-4, IFN-γ and IL-17 production when stimulated with UV-inactivated WT Ci79. Importantly, tissues obtained from vaccinated mice displayed reduced pathology and organ burden compared to challenged non-vaccinated mice. Additionally, serum pentraxin-3 concentrations were not increased 24 h after challenge in vaccinated mice, correlating with reduction of WT MDR-Ab infection in ΔtrxA immunized mice. Furthermore, passive immunization with ΔtrxA-immune sera provided protection against lethal systemic Ci79 challenge. Collectively, the defined live attenuated ΔtrxA strain is a vaccine candidate against emerging MDR Acinetobacter infection.     

Sex difference in the immunogenicity of the quadrivalent Human Papilloma Virus vaccine: Systematic review and meta-analysis

BackgroundImmunological differences between males and females in response to viral vaccines are well known. This the first review to examine them for the Human Papilloma Virus.MethodsWe conducted a systematic review and meta-analysis of the immunogenicity of the Quadrivalent Human Papilloma Virus Vaccine qHPVV. We searched Medline, Embase, and CENTRAL for trials published until September 17, 2019. Inclusion criteria were 3-doses and reporting geometric mean titers (GMTs). We performed random-effects meta-analyses and meta-regression separated by age group and sex.ResultsOur search yielded 1809 unique studies. 334 full texts were screened and data from 18 studies were extracted. Females had higher pooled geometric mean titers than males in all age groups. Log transformed GMTs in male children (<16) years were: against HPV6: 6·62 (95% CI 6·29–6·94; I² = 86·0%), against HPV11: 7·07 (95% CI 6·90–7·23; I² = 63.1%), against HPV16: 8·53 (95% CI 8·28–8·78; I² = 73·0%), and against HPV18 7·21 (95% CI 7·08–7·34; I² = 26·4%). In females: against HPV6 7·10 (95% CI 6·79–7·41; I² = 96·6%), HPV11: 7·32 (95% CI 7·15–7·50; I² = 90·6%), HPV16: 8·71 (95% CI 8·52–8·91; I² = 90·2%), and HPV18 7·35 (95% CI 7·11–7·58; I² = 92·7%). In the meta-regression, the sexual difference was significant for HPV6 (p = 0·022) with a similar tendency for HPV11 (p = 0·066) and HPV18 (p = 0·079). Immunogenicity was significantly higher in children (<16) than in adults (p < 0·001).ConclusionFemales have higher antibody titers against HPV after receiving the qHPVV than do males. The difference is bigger in low-risk HPV strains. Adjusting the doses and schedules for each sex should be explored further.     

Novel csuC-DNA nanovaccine based on chitosan candidate vaccine against infection with Acinetobacter baumannii

Background Generating vaccines is a promising and effective method for stopping the spread of Acinetobacter baumannii (A. baumannii) infections that are becoming more and more drug-resistant (MDR). Developing a DNA vaccine and testing its efficacy and protective effects in BALB/c mice were the goals of this research.Methods We examined the genomes of 35 different strains of A. baumannii using the Vaxign online program, and we selected outer membrane and secreted proteins as potential vaccine candidates. Next, the proteins' immunogenicity, antigenic features, physical and chemical characteristics, and B and MHCI/II cell epitope concentrations were assessed. The DNA vaccine was synthesized. Then, to generate CS-DNA nanoparticles, the DNA vaccine was e encapsulated by chitosan (CS) nanoparticles (NPs). BALB/c mice were used to assess the vaccine's immunogenicity and immunoprotective effectiveness.Results CS-DNA NPs were nontoxic, positively charged (4.39 mV), and small (mean size of 285–350 nm) with ostensibly spherical shapes. It was possible to establish a continuously slow release profile and a high entrapment efficiency (78.12 %). CS-DNA vaccinated BALB/c mice elicited greater levels of csuC-specific IgG in plasma and IFN-γ in splenocyte lysate compared with non-encapsulated DNA vaccine. In addition, BALB/c mice immunized with CS-DNA nanovaccine showed decreased lung damage and bacterial loads in the lung and blood, as well as significant immunity (87.5 %) versus acute fatal intratracheal A. baumannii challenge.Conclusion In conclusion, acute fatal intratracheal A. baumannii exposure was prevented by CS-DNA NPs that induced specific IgG antibodies, Th1 cellular immunity, and other protective mechanisms. Our findings show that this nanovaccine is a promising contender for stopping the spread of A. baumannii infection.     

Decay of anti-Bordetella pertussis antibodies in women of childbearing age following COVID-19 non-pharmaceutical measures

BackgroundImmunization against Bordetella pertussis during pregnancy reduces morbidity from severe pertussis in young infants via trans-placental transfer of anti-B. pertussis Immunoglobulin G (IgG). Studies have reported a near disappearance of respiratory pathogens including B. pertussis following implementation of mitigation strategies to control Coronavirus disease 2019 (COVID-19). We explored how immunity against B. pertussis changed in women of childbearing-age through the COVID-19 pandemic.MethodsPaired blood samples from females of childbearing-age collected at the beginning (May-June 2020) and nearly one year into the COVID-19 pandemic (February-May 2021) in British Columbia (BC), Canada were tested for anti-B. pertussis IgG levels. To ascertain whether early-pandemic IgG levels in 2020 reflected levels in pregnant women early in gestation, 1st trimester sera collected from age-matched healthy pregnant women in 2018 and 2019 were tested for anti-B. pertussis IgG. Levels were compared by t tests. P-value of 0.05 was assigned and statistical significance was set as p < 0.016 using Bonferroni correction.ResultsAnnual provincial B. pertussis incidences per 100,000 in BC in 2020 (3/100,000) and 2021 (<1/100,000) approximated the lowest levels since 1990. In 2021 vs. 2020, anti-pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) IgG levels declined in women of childbearing-age: 6.8 IU/ml (95 %CI, 4.2–10.9) vs. 8.4 IU/ml (5.1–13.9; p = 0.004); 18.8 IU/ml (10.9–32.2) vs. 23.6 IU/ml (13.2–42.1; p < 0.001); and 37.1 IU/ml (18.1–75.9) vs. 47.2 IU/ml (24.8–89.9; p = 0.092), respectively. Although all values were slightly higher, anti-PT, FHA and PRN IgG levels in women of childbearing age did not significantly differ in 2020 compared with early-gestation pregnant women in 2018–2019, 8.4 IU/ml (95% CI, 5.1–13.9) vs. 5.4 IU/ml (95% CI, 3.8–7.7; p = 0.166), 23.6 IU/ml (95% CI, 13.2–42.1) vs. 20.1 IU/ml (95% CI, 13.4–30.2; p = 0.656), and 47.2 IU/ml (24.8–89.9) vs. 17.3 IU/ml (95% CI, 10.5–28.7; p = 0.021), respectively.DiscussionB. pertussis infections should be closely monitored during the relaxing of mitigation measures for COVID-19.     

Evaluation of the impact of HIV-1 infection and density of common nasopharyngeal bacterial colonizers in South African children immunized with 7-valent pneumococcal conjugate vaccine

BackgroundDue to limitations in standard culture methods, the impact of pneumococcal conjugate vaccine (PCV) immunization on nasopharyngeal bacterial carriage density is unclear, including among HIV-infected children.MethodsThe prevalence and density of serotype/serogroup-specific pneumococcal and other nasopharyngeal colonizing bacteria were investigated in archived swabs of HIV-infected and HIV-uninfected, PCV-7 immunized (at 6, 10 and 14 weeks of age) South African children collected at 9 and 16 months of age. During the course of the study, PCV-immunization of children in Soweto was limited to study-participants, as the vaccine had not been introduced into the public immunization program.ResultsAt 9 months of age, the prevalence of overall pneumococcal colonization was lower in HIV-infected (58.6%) than HIV-uninfected children (69.9%, p = 0.02), mainly due to lower prevalence of non-vaccine-serotype colonization (27.8% vs. 40%, respectively; p = 0.047). The mean-log₁₀ density of pneumococcal colonization was, however, higher in HIV-infected (4.81 CFU/ml) than HIV-uninfected pneumococcal colonized children (4.44 CFU/ml; p = 0.014); mainly due to higher mean-log₁₀ density of PCV7-serotype colonization (4.21 vs. 3.72 CFU/ml; p = 0.014). No difference in the prevalence or density of overall pneumococci was found at 16 months of age. The prevalence of non-vaccine serotype colonization remained 1.7 fold higher in HIV-uninfected (60.4%) than HIV-infected children (50.9%, p = 0.049). Other differences included a lower prevalence of H. influenzae colonization in HIV-infected (42.3% and 56%) than HIV-uninfected children (64.2% and 73.4%) at both 9 and 16 months of age respectively; however, the density of colonization was similar.ConclusionIncreased carriage density of residual PCV7-serotypes might cause HIV-infected children to have a higher risk of pneumococcal disease. The higher carriage density observed in HIV-infected children could be attributed to a combination of factors, including HIV treatment and impaired host immunity. Additional studies are needed.     

OmpW is a potential target for eliciting protective immunity against Acinetobacter baumannii infections

Acinetobacter baumannii (A. baumannii) is an important conditioned pathogen that causes nosocomial and community-associated infections. In this study, we sought to investigate whether outer membrane protein W (OmpW) is a potential target for eliciting protective immunity against A. baumannii infections. Mice immunized with the fusion protein thioredoxin-OmpW generated strong OmpW-specific IgG responses. In a sepsis model, both active and passive immunizations against OmpW effectively protected mice from A. baumannii infections. This protection was demonstrated by a significantly improved survival rate, reduced bacterial burdens within organs, and the suppressed accumulation of inflammatory cytokines and chemokines in sera. Opsonophagocytic assays with murine macrophage RAW264.7 cells indicated that the bactericidal effects of the antisera derived from the immunized mice are mediated synergistically by specific antibodies and complement components. The antisera presented significant opsonophagocytic activities against homologous strains and clonally distinct clinical isolates in vitro. Protein data analysis showed that the sequence of OmpW, which has a molecule length of 183 amino acids, is more than 91% conserved in reported A. baumannii strains. In conclusion, we identified OmpW as a highly immunogenic and conserved protein as a valuable antigen candidate for the development of an effective vaccine or the preparation of antisera to control A. baumannii infections.     

Recombinant CP40 from Corynebacterium pseudotuberculosis confers protection in mice after challenge with a virulent strain

BackgroundCaseous Lymphadenitis (CLA) is a contagious, infectious, chronic disease caused by Corynebacterium pseudotuberculosis, which affects mainly sheep and goats. The clinical prevalence of CLA in Brazil is 30%, resulting in decreased milk production, weight loss, and unusable meat and leather. Prophylaxis is based on vaccination; however, current vaccinations do not offer effective protection against the infection, which makes the development of a new vaccine essential to control this disease.Experimental approachHere, we developed a recombinant vaccine based on CP40 protein (rCP40) combined with an adjuvant (Freund's complete adjuvant or saponin) and evaluated its efficacy in a murine model of CLA. Female BALB/c mice were used in an immunization assay.Key resultsrCP40 induced high levels of IgG2a and IgG2b antibodies. After challenge with a virulent strain of C. pseudotuberculosis C57 (10⁴ CFU/mL), the levels of IgG2a and IgG2b were sustained, indicating a Th1 response. The groups immunized with rCP40 protein (GES and GEF groups) showed 100% protection and was statistically significant in the GES and GEF groups (p < 0.037 and p < 0.0952, respectively).ConclusionsThe results indicated the recombinant protein CP40 induced an specific immune response in mice that was able to afford protection after challenge, regardless the adjuvant used in the formulation.     

Seroprotection against tetanus in southern Vietnam

BackgroundOngoing tetanus cases and sporadic outbreaks of vaccine-preventable diseases associated with routine vaccination programmes remain problems in many low and middle-income countries, including Vietnam. With no human-to-human transmission or natural immunity, tetanus antibody levels indicate both individual risk of tetanus and gaps in vaccination programmes.MethodsTo investigate gaps in immunity to tetanus in Vietnam, a country with a historically high level of tetanus vaccination coverage, tetanus antibodies were measure by ELISA from samples selected from a long-term serum bank, established for the purposes of general-population seroepidemiological investigations in southern Vietnam. Samples were selected from 10 provinces, focussing on age-groups targeted by national vaccination programmes for infants and pregnant women (Expanded Programme on Immunization, EPI, and Maternal and Neonatal Tetanus, MNT).ResultsAntibodies were measured from a total of 3864 samples. Highest tetanus antibody concentrations occurred in children under 4 years old, over 90 % of whom had protective levels. Approximately 70 % of children aged 7–12 years had protective antibody concentrations although there was variation among provinces. For infants and children, there were no significant differences in tetanus protection between males and females, but for adults aged 20–35 years, in five of the ten provinces surveyed, protection against tetanus was higher in females (p < 0.05) who are eligible for booster doses under the MNT programme. In seven of ten provinces, antibody concentrations were inversely related to age (p < 0.01) and protection of older individuals was generally low.ConclusionWidespread immunity to tetanus toxoid is seen in infants and young children consistent with the high coverage rates reported for diptheria tetanus toxoid and pertussis (DTP) in Vietnam. However, the lower antibody concentrations seen in older children and men suggest reduced immunity to tetanus in populations not targeted by EPI and MNT programmes.     

Comparison of the nine polymorphic membrane proteins of Chlamydia trachomatis for their ability to induce protective immune responses in mice against a C. muridarum challenge

ObjectivesTo test vaccines, formulated with novel antigens, to protect mice against Chlamydia infections.MethodsTo determine the ability of polymorphic membrane proteins (Pmps) to induce cross-species protective immune responses, recombinant fragments from all nine C. trachomatis serovar E Pmps were used to vaccinate BALB/c mice utilizing CpG-1826 and Montanide ISA 720 as adjuvants. C. muridarum recombinant MOMP and PBS, formulated with the same adjuvants, were used as positive and negative controls, respectively. Mice were challenged intranasally with 10⁴ inclusion-forming units (IFU) of C. muridarum. Animals were weighed daily and at 10 days post-challenge, they were euthanized, their lungs harvested, weighed and the number of chlamydial IFU counted.ResultsFollowing vaccination the nine Pmps elicited immune responses. Based on body weight changes, or number of IFU recovered from lungs, mice vaccinated with Pmp C, G or H were the best protected. For example, over the 10-day period, the negative control group vaccinated with PBS lost significantly more body weight than mice immunized with PmpC or G (P < 0.05). C. muridarum MOMP vaccinated mice were better protected against body weight losses than any group immunized with Pmps. Also, the median number of IFU recovered from the lungs of mice vaccinated with PmpC (72 × 10⁶) or PmpH (61 × 10⁶) was significantly less than from mice immunized with PBS (620 × 10⁶; P < 0.05). As determined by the number of IFU, all Pmps elicited less protection than C. muridarum MOMP (0.078 × 10⁶ IFU; P < 0.05).ConclusionsThis is the first time PmpC has been shown to elicit cross-species protection against a respiratory challenge. Additional work with Pmps C, G and H is recommended to determine their ability to protect animal models against genital and ocular challenges.     

High-protein diet promotes a moderate postpartum weight loss in a prospective cohort of Brazilian women

ObjectiveWhether a high-protein (HP) diet promotes body weight loss (BWL) when compared with a low-protein (LP) diet is still unclear. Therefore, we evaluated the effects of an HP diet on BWL during postpartum.MethodsA food-frequency questionnaire with 81 items was applied at 6 mo after delivery to evaluate the diet of 430 postpartum women aged 18–45 y. Body weight was measured approximately at 0.5, 2, 6, and 9 mo after delivery. Body weight loss was modeled by comparing an HP diet (≥1.2 g · kg^?1 · d^?1) with an LP diet (<1.2 g · kg^?1 · d^?1) using mixed-effects linear regression models adjusted for energy intake, percentage of body fat at baseline, stature, age, race, smoking, and schooling.ResultsUsual energy intake was higher in the HP than in the LP diet group (2623 versus 1791 kcal, P < 0.0001). Daily mean protein intakes were 1.54 ± 0.32 g · kg^?1 · d^?1 for the HP group and 0.83 ± 0.20 g · kg^?1 · d^?1 for the LP group. A multivariate model showed that women in the HP group lost 316 ± 0.062 g of body weight more per month (P < 0.01) when compared with the LP group.ConclusionA reported higher protein intake may improve moderate postpartum body weight loss. Further studies should evaluate the long-term consequences of an HP diet postpartum.     

Age at HPV vaccine initiation and completion among US adolescent girls: Trend from 2008 to 2012

ObjectiveTo examine the trend of provider-verified HPV vaccine initiation (≥1 dose) and completion (≥3 doses) among adolescent girls at the Advisory Committee on Immunization Practices (ACIP) recommended age (11–12 years).MethodsWe analyzed National Immunization Survey of Teens 2008–2012 data and examined the trend of provider-verified HPV vaccine initiation and completion among <13 year old girls.ResultsData on age at HPV vaccine initiation and completion were available for 24,466 and 15,972 girls, respectively. The weighted proportion of girls who initiated the vaccine at <13 years of age was 14.1%, 24.1%, 35.9%, 47.7% and 55.9% in 2008, 2009, 2010, 2011 and 2012, respectively (p for trend <.001). The similar trend was also observed for mean age at HPV vaccine initiation and completion (p < .001).ConclusionsAdditional efforts are needed to increase HPV vaccine uptake among adolescent girls as only half of them receive this vaccine at ACIP recommended age.     

Trivalent pneumococcal protein vaccine protects against experimental acute otitis media caused by Streptococcus pneumoniae in an infant murine model

BackgroundCurrently licensed serotype-based pneumococcal vaccines are effective in preventing invasive pneumococcal diseases, but less effective in preventing non-bacteremic pneumonia and acute otitis media (AOM). We previously reported that a trivalent pneumococcal protein recombinant vaccine (PPrV) protected against pneumonia in a murine model. Here we evaluated PPrV protection against AOM in an infant murine model.MethodsC57BL/6J mice were intramuscularly vaccinated at 1–3 weeks of age with monovalent pneumococcal histidine triad protein D (PhtD), or pneumococcal choline binding protein A (PcpA), or detoxified pneumolysin (PlyD1), or trivalent vaccine, and transtympanically challenged at 7–8 weeks of age with 1 × 10² CFU of pneumococcal strain BG7322 (6A) or 1 × 10⁴ CFU of pneumococcal nontypeable strain 0702064 MEF. Serum IgG titers were determined by ELISA. At 24 and 48 h post infection (hpi), animals were sacrificed and middle ear fluid (MEF) samples were collected to determine pneumococcal CFUs.ResultsWe found that vaccination of infant mice with monovalent and trivalent pneumococcal proteins elicited significant serum IgG antibody responses to corresponding component proteins. Vaccination with PhtD reduced BG7322 bacterial burdens in MEF at both 24 (p = 0.05) and 48 hpi (p = 0.16). Vaccination with PcpA significantly reduced the bacterial burdens in MEF at both 24 (p = 0.02) and 48 hpi (p = 0.004), and PlyD1 significantly reduced bacterial burden in MEF at 48 hpi (p = 0.02). Vaccination with trivalent PPrV (PhtD, PcpA and PlyD1) significantly reduced Spn burdens in MEF at both 24 (p = 0.001) and 48 hpi (p < 0.0001). Similar reductions of bacterial burdens were found when the vaccinated animals were challenged with a non-typeable Spn strain. Vaccinated mice had significantly milder inflammatory cytokine levels (IL-1β, IL-6, TNF-α, MIP-2 and KC) in middle ears at 24 hpi (all p values < 0.05).ConclusionTrivalent PPrV confers protection against pneumococcal AOM in an infant murine model.     

Characterization of the protective immune response to Yersinia pseudotuberculosis infection in mice vaccinated with an LcrV-secreting strain of Lactococcus lactis

BackgroundPseudotuberculosis is an infection caused by the bacterial enteropathogen Yersinia pseudotuberculosis and is considered to be a significant problem in veterinary medicine. We previously found that intranasal administration of a recombinant Lactococcus lactis strain that secretes the low-calcium response V (LcrV) antigen from Y. pseudotuberculosis (Ll-LcrV) confers protection against a lethal Y. pseudotuberculosis infection. Here, we aimed at characterizing the immunological basis of this LcrV-elicited protective response and at determining the duration of vaccine-induced immunity.MethodsSplenocytes from BALB/c mice intranasally immunized with Ll-LcrV or Ll as control were immunostained then analyzed by flow cytometry. Protection against a lethal intravenous injection of Y. pseudotuberculosis was also determined (i) in immunized BALB/c mice depleted or not of CD4⁺, CD8⁺ or CD25⁺ cells and (ii) in naïve BALB/c mice receiving serum from immunized mice by counting the number of bacteria in liver and spleen. Lastly, survival rate of immunized BALB/c mice following a lethal intravenous injection of Y. pseudotuberculosis was followed up to 9-months.ResultsWe found that T and B lymphocytes but not non-conventional lymphoid cells were affected by Ll-LcrV immunization. We also observed that depletion of CD4⁺ and CD25⁺ but not CD8⁺ cells in immunized mice eradicated protection against a lethal systemic Y. pseudotuberculosis infection, suggesting that activated CD4⁺ T lymphocytes are required for vaccine-induced protection. Adoptive transfer of LcrV-specific antibodies from Ll-LcrV-immunized animals significantly reduced the bacterial counts in the liver compared to non-vaccinated mice. Lastly, the protective immunity conferred by Ll-LcrV decreased slightly over time; nevertheless almost 60% of the mice survived a lethal bacterial challenge at 9 months post-vaccination.ConclusionMucosal vaccination of mice with Ll-LcrV induced cell- and antibody-mediated protective immunity against Y. pseudotuberculosis infection in the mouse and the protection is long-lasting.     

HPV genotyping in biopsies of HSIL and invasive cervical cancers in women living with HIV: A cohort- and a nested -case control study

ObjectiveTo characterize HPV genotype distribution in HSIL and ICC- biopsies, of WLWH, in Europe, as compared to HIV-negative women.DesignCohort- and nested -case control study.MethodWe characterized HPV genotype distribution by performing PCR on HSIL and ICC biopsies from WLWH (n = 170); 85 cases were compared to 85 HIV-negative matched controls. The proportion of patients that might be protected by HPV vaccines was estimated.ResultsAmong WLWH (median age 36 years-old, median duration of HIV infection 70,5 months, 79% under cART): the most frequently detected HPV were HPV16 (30%), HPV35 (16%), HPV58 (14,7%), HPV31 (13,5%), and HPV52 (11,7%). HPV16 was less frequently found in WLWH, originating from Central Africa (20,5%) compared to other African regions (35,5%) (p = 0,05) or world regions (38,8%) (p = 0,007). Multiple versus single high-risk HPV infections were associated with younger age (≤35 years)(odds ratio (OR) 2,65 (95%IC: 1,3–5,2,p = 0,002), lymphocyte CD4 count < 350 cells / µL (OR 2,7 (95%IC: 2–8,5; p = 0,005), use of cART for < 18 month OR 2,2 (95%IC: 1,1–4,5),p = 0,04) or a cumulative time with undetectable HIV viral load of less than 12 months (OR 4,2 (95%IC: 2–8.5,p = 0,001). HPV 31, 33 and 35 were more frequently detected in samples from WLWH than in HIV-negative controls (p < 0,05). The 9-valent vaccine would increase HPV protection, in HIV-positive and negative women (p < 0,001).ConclusionWLWH are more frequently infected with high-risk HPV other than 16 and 18 than HIV-negative ones. The use of 9-valent vaccine may prevent HSIL or ICC in up to 85% of the women. Adding HPV 35 to the HPV vaccine panel, might improve vaccine effectiveness in WLWH.     

B cell and antibody responses in mice induced by a putative cell surface peptidase of Pneumocystis murina protect against experimental infection

RationalePneumocystis pneumonia is a major cause of morbidity and mortality in HIV-infected subjects, cancer patients undergoing chemotherapy and solid organ transplant recipients. No vaccine is currently available. By chemical labeling coupled with proteomic approach, we have identified a putative surface protein (SPD1, Broad Institute gene accession number PNEG_01848) derived from single suspended P. murina cysts. SPD1 was expressed in an insect cell line and tested for vaccine development.MethodsMice were immunized with SPD1 plus adjuvant MF-59 by subcutaneous injection. Three weeks after the last immunization, CD4+ cells were depleted with anti-CD4 antibody GK1.5. The mice were then challenged with 2 × 10⁵ Pneumocystis organisms. Mice were sacrificed at 4 and 6 weeks after PC challenge. Spleen/lung cells and serum were harvested. B cells and memory B cells were assessed via flow cytometry. Specific Pneumocystis IgG antibody was measured by ELISA before and after challenge. Infection burden was measured as real-time PCR for P. murina rRNA.ResultsNormal mice infected with Pneumocystis mounted a serum IgG antibody response to SPD1. Serum from rhesus macaques exposed to Pneumocystis showed a similar serum IgG response to purified SPD1. SPD1 immunization increased B cell and memory B cell absolute cell counts in CD4-depleted Balb/c mice post Pneumocystis challenge in spleen and lung. Immunization with SPD1 significantly increased specific Pneumocystis IgG antibody production before and after challenge. Mice immunized with SPD1 showed significantly decreased P. murina copy number compared with mice that did not receive SPD1 at 6 weeks after challenge.ConclusionImmunization with SPD1 provides protective efficacy against P. murina infection. SPD1 protection against Pneumocystis challenge is associated with enhanced memory B cell production and higher anti–Pneumocystis IgG antibody production. SPD1 is a potential vaccine candidate to prevent or treat pulmonary infection with Pneumocystis.     

Immunogenicity of Vibrio cholerae outer membrane vesicles secreted at various environmental conditions

Cholera is caused by toxigenic Vibrio cholerae. It is a significant health problem and an important cause of mortality of children in developing countries. Annually, about 5–7 million people are being infected worldwide, leading to death of 100,000 to 120,000. Immunization using the currently available cholera vaccines has been recommended by World Health Organization (WHO) in areas where cholera is endemic or at risk of outbreaks. Gram-negative bacteria secrete outer membrane vesicles (OMVs) that play important roles in virulence and host-pathogen interaction. The content of protein and lipid in OMVs are affected by purification methods and bacterial growth condition. OMVs released from V. cholerae are an appropriate candidate for vaccine development. The protection conferred by a new vaccine candidate prepared using different methods and in two different growth conditions with nanoparticles in an experimental model of cholera in mice was investigated. OMVs were encapsulated in chitosan-tripolyphosphate (TPP) nanoparticles prepared by an ionic gelation method and coated with Eudragit as an enteric polymer. OMVs loaded into nanoparticles (NP-OMVs) were homogeneous and spherical in shape, with a size of 417 nm. BALB/c mice (male, 20–24 g) were immunized via intraperitoneal (10 µg) or oral route (50 µg) with free or encapsulated OMVs. Seventy-eight days after first administration, serum of mice was infected with infection dose of V. cholerae (≥10⁷ CFU). The new vaccine was able to protect fully against infection when it was administered via mucosa. By intraperitoneal route, the unpolymerized OMVs increased the protection against these bacteria.     

Safety surveillance of varicella vaccine using tree-temporal scan analysis

ImportancePassive surveillance systems are susceptible to the under-reporting of adverse events (AE) and a lack of information pertaining to vaccinated populations. Conventional active surveillance focuses on predefined AEs. Advanced data mining tools could be used to identify unusual clusters of potential AEs after vaccination.ObjectiveTo assess the feasibility of a novel tree-based statistical approach to the identification of AE clustering following the implementation of a varicella vaccination program among one-year-olds.Setting and participantsThis nationwide safety surveillance was based on data from the Taiwan National Health Insurance database and National Immunization Information System for the period 2004 through 2014. The study population was children aged 12–35 months who received the varicella vaccine.ExposureFirst-dose varicella vaccine.Outcomes and measuresAll incident ICD-9-CM diagnoses (emergency or inpatient departments) occurring 1–56 days after the varicella vaccination were classified within a hierarchical system of diagnosis categories using Multi-Level Clinical Classifications Software. A self-controlled tree-temporal data mining tool was then used to explore the incidence of AE clustering with a variety of potential risk intervals. The comparison interval consisted of days in the 56-day follow-up period that fell outside the risk interval.ResultsAmong 1,194,189 varicella vaccinees with no other same-day vaccinations, nine diagnoses with clustering features were categorized into four safety signals: fever on days 1–6 (attributable risk [AR] 38.5 per 100,000, p < 0.001), gastritis and duodenitis on days 1–2 (AR 5.9 per 100,000, p < 0.001), acute upper respiratory infection on days 1–5 (AR 11.0 per 100,000, p = 0.006), and varicella infection on days 1–9 (AR 2.7 per 100,000, p < 0.001). These safety profiles and their corresponding risk intervals have been identified in previous safety surveillance studies.ConclusionsUnexpected clusters of AEs were not detected after the mass administration of childhood varicella vaccines in Taiwan. The tree-temporal statistical method is a feasible approach to the safety surveillance of vaccines in populations of young children.     

Outer membrane vesicles as an acellular vaccine against Acinetobacter baumannii

Acinetobacter baumannii produces different types of infections including pneumonia, meningitis, and bloodstream infections. The optimal treatment of these infections has been complicated by the global emergence of multidrug resistant strains, requiring the development of novel approaches for treatment and prevention. Outer membrane vesicles are outpouchings of the bacterial outer membrane that are secreted from numerous pathogenic Gram-negative bacteria. In the present study, we describe the isolation of outer membrane vesicles from A. baumannii and their use as a vaccine in a mouse model of disseminated sepsis. Immunization produced a robust antibody response against multiple bacterial antigens which consisted of antigen-specific IgG and IgM. In addition, both IgG1 and IgG2c subtypes were produced by immunization. Immunized mice had lower tissue bacterial loads and lower serum levels of the pro-inflammatory cytokines IL-6 and IL-1β post-infection compared to control mice. Importantly, vaccination protected mice from challenge with the ATCC 19606 strain and provided protection against two clinical isolates, including a pan-resistant strain. These results indicate that vaccination with outer membrane vesicles may be a viable strategy for preventing A. baumannii infection.