Immunization of Nile tilapia (Oreochromis niloticus) Broodstock With Tilapia Lake Virus (TiLV) Inactivated Vaccines Elicits Protective Antibody and Passive Maternal Antibody Transfer

Tilapia lake virus (TiLV), a major pathogen of farmed tilapia, is known to be vertically transmitted. Here, we hypothesize that Nile tilapia (Oreochromis niloticus) broodstock immunized with a TiLV inactivated vaccine can mount a protective antibody response and passively transfer maternal antibodies to their fertilized eggs and larvae. To test this hypothesis, three groups of tilapia broodstock, each containing 4 males and 8 females, were immunized with either a heat-killed TiLV vaccine (HKV), a formalin-killed TiLV vaccine (FKV) (both administered at 3.6 ×106 TCID50 per fish), or with L15 medium. Booster vaccination with the same vaccines was given 3-weeks later, and mating took place 1 week thereafter. Broodstock blood sera, fertilized eggs and larvae were collected from 6-14 weeks post-primary vaccination for measurement of TiLV-specific antibody (anti-TiLV IgM) levels. In parallel, passive immunization using sera from the immunized female broodstock was administered to naïve tilapia juveniles to assess if antibodies induced in immunized broodstock were protective. The results showed that anti-TiLV IgM was produced in the majority of both male and female broodstock vaccinated with either the HKV or FKV and that and that these antibodies could be detected in the fertilized eggs and larvae from vaccinated broodstock. Higher levels of maternal antibody were observed in fertilized eggs from broodstock vaccinated with HKV than those vaccinated with FKV. Low levels of TiLV-IgM were detected in some of the 1-3-day old larvae but were undetectable in 7-14-day old larvae from the vaccinated broodstock, indicating a short persistence of TiLV-IgM in larvae. Moreover, passive immunization proved that antibodies elicited by TiLV vaccination were able to confer 85% to 90% protection against TiLV challenge in naïve juvenile tilapia. In conclusion, immunization of tilapia broodstock with TiLV vaccines could be a potential strategy for the prevention of TiLV in tilapia fertilized eggs and larvae, with HKV appearing to be more promising than FKV for maternal vaccination.

A prevaccination validated network that drives the breadth of the protective neutralizing antibody response following Dengue Vaccine TV003 immunization

Development of fully protective dengue virus (DV) vaccines has been problematic as infection with DV requires a broad antibody immune response that targets all 4 possible serotypes. Herein, we used an integrated systems vaccinology approach to identify prevaccination features that allow the development of fully protective DV-specific antibody responses. This approach allowed us to identify a transcription network in a subset of monocytes defined by the expression of CD68 and downstream of specific pro- and anti-inflammatory cytokines. Moreover, we identified metabolites as drivers of an immune response that induced neutralizing antibodies to the 4 DV serotypes. Specifically, PC/PE drove the production of TGF-B in CD68 low monocytes, which was a positive correlate of the protective antibody response. In contrast, primary and secondary bile acids triggered a proinflammatory response downstream of TGR5 signaling and inflammasome activation in CD68 high monocytes, which was associated to a non-protective antibody response. These features were validated in vitro in primary myeloid cells. Our results highlight the role of cell and systemic metabolism as regulators of protective immune responses to vaccination, and that systems vaccinology is a key tool to identify such mechanisms.

Germinal center activity and B cell maturation promote protective antibody responses against Plasmodium pre-erythrocytic infection

Blocking Plasmodium, the causative agent of malaria, at the asymptomatic pre-erythrocytic stage would abrogate disease pathology and prevent transmission. Rodent-infectious species of Plasmodium such as P. yoelii (Py) serve as key tools to study vaccine efficacy and disease biology in immune-competent experimental animals. Here we evaluated the differences in vaccine-elicited humoral immunity in two widely used, and vastly diverged, inbred mouse strains, BALB/cJ and C57BL/6J, and identified immunological factors associated with protection. We vaccinated with Py circumsporozoite protein (CSP), the major surface antigen on the sporozoite, and evaluated protective efficacy after mosquito bite challenge. Vaccination achieved 60% sterile protection and otherwise delayed blood stage patency in BALB/cJ mice, whereas; all C57BL/6J mice were infected similar to controls. Interestingly, protection was mediated by antibodies, and could be passively transferred from immunized BALB/cJ mice into naïve C57BL/6J. Dissection of the underlying immunological features of protection revealed early deficits in antibody titers and polyclonal avidity in C57BL/6J mice. Additionally, PyCSP-vaccination in BALB/cJ induced a significantly higher proportion of antigen-specific B-cells and class-switched memory B-cell (MBCs) populations than in C57BL/6J mice. Strikingly, C57BL/6J mice also had markedly fewer germinal center experienced, CSP-specific class-switched MBCs compared to BALB/cJ mice. Analysis of the IgG γ chain repertoires by next generation sequencing in PyCSP-specific memory B-cell repertoires also revealed higher somatic hypermutation rates in BALB/cJ mice than in C57BL/6J mice. These findings indicate that BALB/cJ mice achieved higher levels of B cell maturation in response to vaccination with PyCSP, which likely enabled the development of protective antibody responses. Overall, our study indicates that germinal center activity and B cell maturation are key processes in the development of vaccine-elicited protective antibodies against CSP.

Antibody to Hepatitis B Surface Antigen in Vaccinated Healthcare Workers in a Tertiary Care Centre – A Descriptive Study from South Kerala

BACKGROUND Hepatitis B virus (HBV) has long been recognized as a work-related hazard for health-care personnel (HCP). HCPs are all paid and unpaid persons giving health care or working or training in health-care settings, who have reasonably expected risks for exposure to infectious materials. Post-vaccination serological testing is suggested 4 to 8 weeks after completion of the primary course in all health care workers. If the anti - HBs levels are less than 10 mIU / ml 4 - 8 weeks after the third dose of vaccine, the person's serum has to be tested for markers of HBV. The objective of the study was to evaluate the immune response after hepatitis B vaccination in health care workers. METHODS This study was a cross-sectional study that was conducted for a period of one year (January 2016 – December 2016). In this study, blood samples of 211 HCP were collected and sera were tested for quantitative anti - HBs level using anti - HBs EIA kit (Diapro, Italy). RESULTS 75. 83 % of HCP were completely vaccinated and 24.17 % did not complete the three-dose regimen. 91.87 % of completely vaccinated HCP had an anti- HBs titre of more than 10mIU/ml while 80.39 % of incompletely vaccinated HCP had protective antibody levels. 71.42 % of males and 90.35 % of females had protective antibody titre. The housekeeping staff were the most protected (100 %) while doctors were the least protected (54.54 %). Among the different vaccine, compliant subgroups 85.96 % of HCP who were completely vaccinated and had not taken booster dose had protective antibody titre even after five years where as 90.47 % of HCP who were completely vaccinated and had taken a booster dose and had protective antibody titre even after 5 years. It was also noted that 95.23 % of HCP who were vaccinated before the age of 20 had a protective antibody titre while only 70.58 % of those who got vaccinated after the age of forty had a protective antibody titre. CONCLUSIONS The records, if possible retrievable electronic records, should be maintained in health care centers as a reference in case of occupational exposure or for other purposes. KEYWORDS Hepatitis B, Anti HBs, Health Care Personnel

Prototype Pentavalent Bovine Leptospira Vaccines Blended with Oil Adjuvant Provides Protection and Prevents Renal Colonization in Guinea Pig Model

Background: Leptospirosis significantly impacts the economy of livestock farmers by causing reproductive failure and production losses in bovines. The control of bovine leptospirosis requires a combination of vaccination programme, biosecurity measures and chemotherapeutic regimens. Vaccination protect the clinical diseases and reduces/prevents renal colonisation of Leptospires and in turn reduces excretion of leptospires in urine which is a major source of environmental contamination. Some serovars of leptospires require cell mediated immunity apart from humoral immunity. This study was undertaken to develop prototype vaccine with prevalent serogroups to induce humoral and cell mediated immunity. Immunogenicity of the prototype vaccines and their safety were assessed experimentally in Guinea pigs.Methods: An inactivated oil adjuvant prototype pentavalent bovine leptospira vaccines with serogroups Australis, Hebdomadis, Hardjo, Javanica and Pomona which were prevalent in Tamil Nadu were developed and compared with the aluminium hydroxide gel adjuvant vaccine. The humoral immune response was assessed measuring antibodies by Microscopic Agglutination Test and Cell Mediated Immune response was assessed by lymphocyte proliferation assay. The ability of these vaccines to protect Guinea pigs against virulent Leptospires challenge was also demonstrated.Result: The prototype vaccine blended with oil adjuvants resulted in higher protective antibody titres of more than 6.64 log2 (≥1:100) than the aluminium hydroxide adjuvant blended vaccine. The protective antibody titres lasted upto 180 days, except for serogroup Javanica (150 days). The Montanide adjuvants were able to produce cell mediated immune response for protection against serovar Hardjo. Challenge study in guinea pigs showed complete protection following vaccination using pentavalent vaccine blended with Montanide adjuvants, while the aluminium hydroxide adjuvant was able to confer only partial protection. The Montanide blended prototype vaccines were also able to prevent renal colonisation of all five serogroups. This study shows the potential of the oil adjuvant blended multivalent vaccine for use in vaccination programmes against bovine leptospirosis.