Evaluation of the Protective Efficacy of Different Doses of a Chlamydia abortus Subcellular Vaccine in a Pregnant Sheep Challenge Model for Ovine Enzootic Abortion.

Chlamydia abortus, the aetiological agent of enzootic abortion of ewes, is a major cause of reproductive loss in small ruminants worldwide, accounting for significant economic losses to the farming industry. Disease can be managed through the use of commercial inactivated or live whole organism-based vaccines, although both have limitations particularly in terms of efficacy, safety and disease-associated outbreaks. Here we report a comparison of two experimental vaccines (chlamydial outer membrane complex (COMC) and octyl glucoside (OG)-COMC) based on detergent extracted outer membrane preparations of C. abortus and delivered as prime-boost immunisations, with the commercial live vaccine Cevac® Chlamydia in a pregnant sheep challenge model. No abortions occurred in either experimental vaccine group, while a single abortion occurred in the commercial vaccine group. Bacterial shedding, as a measure of potential risk of transmission of infection to naïve animals, was lowest in the COMC vaccinated group, with reductions of 87.5%, 86.4% and 74% observed for the COMC, OG-COMC and live commercial vaccine groups, respectively, compared to the unvaccinated challenge control group. The results show that the COMC vaccine performed the best and is a safer efficacious alternative to the commercial vaccines. However, to improve commercial viability, future studies should optimise the antigen dose and number of inoculations required.

Chlamydia abortus, the cause of ovine enzootic abortion, is a zoonotic bacterial pathogen and one of the most infectious causes of foetal death in sheep worldwide. Although the disease can be controlled using commercial inactivated and live whole-organism vaccines, there are issues with both, particularly concerning efficacy and safety. Recently, we have described the development of a new COMC (chlamydial outer membrane complex) vaccine based on a detergent-extracted outer membrane protein preparation of the pathogen, which can be delivered in a single inoculation and is both efficacious and safe. In this study, we have evaluated the COMC vaccine further in a dose-response titration of the chlamydial antigen content of the vaccine (from 20 to 2.5 µg in seven experimental groups) using an established pregnant sheep challenge model. No obvious dose-response relationship was observed across the groups, with a single abortion event occurring in four of the groups and three in the lowest dose group (2.5 µg). No abortions occurred in the 15 and 10 µg groups. The abortion rates (0-14%) were significantly below that of the challenge control group (33%). A similar reduction in bacterial shedding of infectious organisms following parturition was observed in the vaccinated groups compared to the challenge control group, which is important in terms of reducing potential transmission to naive animals. The results show that a dose of 10 µg antigen in the vaccine will be optimal in terms of maximising efficacy, reducing shedding at parturition, and ensuring it is cost-effective to produce for commercial manufacture.

Ovine enzootic abortion (OEA), caused by Chlamydia abortus, is an economically important disease in many countries. Inactivated vaccines have been used for many years as they induce immunity in sheep, although outbreaks of abortions have been described in vaccinated flocks. In addition, there is a commercially available live attenuated vaccine that provides good protective results. Recently however, reports question the attenuation of this vaccine and associate it with the appearance of outbreaks of OEA in vaccinated flocks. In the present study, a recently commercialized inactivated vaccine (INMEVA®; Laboratorios Hipra S.A., Amer, Spain) has been evaluated using mouse and sheep experimental models. In the mouse models (non-pregnant and pregnant models), the efficacy of INMEVA vaccine has been compared to an unvaccinated control group and to an experimental inactivated vaccine considered as a positive protection control (UMU vaccine). In the non- pregnant model, the UMU vaccine was more effective than the INMEVA vaccine regarding the impact on body weight or the presence of C. abortus in the liver, but both vaccinated groups (UMU and INMEVA) had significantly lower C. abortus in the liver compared to the control group. In the pregnant model in terms of reproductive failures, pups per mouse or the presence of C. abortus in the liver or uterus, no significant differences were found between both vaccines, inducing protection compared to the control group. In the ovine pregnant model, where INMEVA vaccine was compared only to an unvaccinated group, the results indicate that this new commercial vaccine is safe and provides a suitable level of protection against an experimental challenge with C. abortus. A 75% reduction in reproductive disorders, 55% reduction in animals with C. abortus shedding on day of parturition/abortion, and a significant reduction of the average amount of chlamydial shedding from parturition/abortion over the next 21 days was observed, in relation to the infected control group. The results suggest that this vaccine is adequate for the control and prevention of OEA; however, future studies are necessary to elucidate the type of protective immune response that it induces.

BackgroundThe live, temperature-attenuated vaccine strain 1B of Chlamydia abortus, the aetiological agent of ovine enzootic abortion (OEA), has been implicated in cases of vaccine breakdown. The aim of this study was to understand the nature of this attenuation through sequencing of the vaccine parent strain (AB7) and the derived mutant strains 1B and 1H, as well as to clarify the role of the vaccine strain in causing disease through comparative whole genome analysis. MethodsWhole genome sequencing was performed on: vaccine parent strain AB7; N-methyl-N′-nitro-N-nitrosoguanidine (NTG)-induced temperature attenuated mutant strain 1B grown from the commercial live vaccines Cevac Chlamydia and Enzovax; strain 1H a reverted NTG mutant; and 5 strains isolated from cases of OEA originating from animals from the original vaccine safety trial (2 strains) or from vaccinated ewes or ewes exposed to vaccinated animals (3 strains). ResultsWe confirmed that AB7 is in a different lineage from the reference strain S26/3. The genome of vaccine strain 1B contains ten single nucleotide polymorphisms (SNPs) created by the NTG treatment, which are identical to those found in strain 1H. The strains from OEA cases also cluster phylogenetically very tightly with these vaccine strains. ConclusionsThe results show that C. abortus vaccine strain 1B has an identical genome sequence to the non-attenuated “reverted mutant” strain 1H. Thus, the protection of the 1B vaccine is unlikely to be due to the NTG induced SNPs and is more likely caused by the administration of high doses of C. abortus elementary bodies that stimulate protective immunity. Vaccine-identical strains were also isolated from cases of disease, as well as strains which had acquired 1–3 SNPs, including an animal that had not been vaccinated with either of the commercial live OEA vaccines, indicating that the 1B vaccine strain may be circulating and causing disease.

Efficacy of different commercial and new inactivated vaccines against ovine enzootic abortion

Abortion storm induced by the live C. abortus vaccine 1B strain in a vaccinated sheep flock, mimicking a natural wild-type infection

Background/Objective: Recently, we published three studies describing the development and optimization of a new, safe, and efficacious vaccine to protect sheep from ovine enzootic abortion, which is caused by the zoonotic pathogen Chlamydia abortus. The vaccine, which can be delivered through a single inoculation, is based on a detergent-extracted outer membrane protein (chlamydial outer membrane complex or COMC) preparation of the pathogen. This study aimed to optimize the vaccine further by comparing the effects of different adjuvants on protective efficacy. Methods: We evaluated the effectiveness of three different vaccines (2.5 µg COMC) formulated with one of three adjuvants (Montanide ISA 70VG, Montanide ISA 61VG, and QuilA) to reduce the rate of abortion, placental load and pathology, and post-partum vaginal shedding of organisms in comparison to our benchmark 20 µg COMC/Montanide ISA 70 VG vaccine and a challenge control group of animals. The humoral and cellular immunological responses to vaccination and to challenge were also assessed. Results: The two low-dose Montanide formulated vaccines resulted in low abortion rates of 3.2 and 8.1% for ISA 70 VG and ISA 61 VG, respectively, which were comparable to the benchmark vaccine group (2.7%) and considerably lower than the QuilA (23.7%) and challenge control (36.8%) groups. Similarly, the Montanide-adjuvanted groups had much lower bacterial loads (range: 136–431 genome copies) on vaginal swabs post-parturition than the QuilA (8.9 × 104 copies) and challenge control (2.4 × 105 copies) groups. Conclusions: The results showed that both Montanide adjuvants are more effective for maximizing COMC vaccine efficacy than the QuilA adjuvant and result in much lower bacterial shedding of the pathogen post-parturition, which is important for minimizing potential transmission to naïve animals.

To evaluate, under field conditions, the effects of a commercial porcine circovirus type 2 (PCV2) vaccine on mortality rate and growth performance in a herd infected with PCV2 that had a history of porcine circovirus disease. Randomized controlled clinical trial. 485 commercial, cross-bred, growing pigs. Prior to weaning, pigs were randomly assigned within litter to a vaccination or unvaccinated control group. Pigs in the vaccination group were given a commercial PCV2 vaccine at weaning and 3 weeks later. Mortality rate was recorded, and pigs were weighed prior to vaccination, when moved from the nursery, and prior to marketing. Infection status was assessed by serologic testing and detection of viral DNA in serum. Compared with control pigs, pigs vaccinated against PCV2 had a significantly lower mortality rate during the finishing phase, significantly higher average daily gain during the finishing phase, and significantly lower likelihood of being lightweight at the time of marketing. For vaccinated pigs, overall mortality rate was reduced by 50% and average daily gain during the finishing period was increased by 9.3%. At the time of marketing, vaccinated pigs weighed an average of 8.8 kg (19.4 lb) more than control pigs, without any difference in days to marketing. Serum PCV2 antibody titers increased in control pigs, and PCV2 DNA was detected, indicating active PCV2 infection. Results suggested that vaccination against PCV2 was effective at reducing mortality rate and improving growth performance among pigs in a herd infected with PCV2.

Protection of ewes vaccinated with A22 strain Chlamydia psittaci (ovis) against challenge in pregnancy with homologous and heterologous strains of the organism

Background: The COVID-19 pandemic, driven by SARS-CoV-2, necessitated the rapid development and global deployment of vaccines. Despite the high efficacy of vaccines like AstraZeneca and Pfizer-BioNTech in preventing severe COVID-19, concerns about potential side effects, particularly on male fertility, have arisen. Objective: This study aims to evaluate the impact of COVID-19 vaccination on key sperm parameters (motility, concentration, count, and morphology) and serum interleukin-6 (IL-6) levels in men. Materials and methods: A cross-sectional study was conducted over six months (March to August 2022) at the High Institute for Infertility Diagnosis and Assisted Reproductive Technologies in Baghdad, Iraq. The study included 63 participants divided into three groups: AstraZeneca vaccine group (N=24), Pfizer vaccine group (N=19), and an unvaccinated control group (N=20). Participants’ sperm parameters were analyzed following the WHO guidelines, and serum IL-6 levels were measured using ELISA. Results: No statistically significant differences were found in sperm motility, concentration, total sperm count, or morphology between vaccinated and unvaccinated groups. Specifically, sperm motility was 57.3±8.9% in the vaccinated group versus 56.8±9.2% in the control group (p=0.782). Sperm concentration was 62.5±14.7 M/mL in the vaccinated group compared to 61.9±15.1 M/mL in the control group (p=0.845). Total sperm count was 185.6±43.8 M in the vaccinated group versus 183.2±44.5 M in the control group (p=0.802). Morphologically normal sperm were 4.2±1.1% in the vaccinated group versus 4.1±1.0% in the control group (p=0.659). Serum IL-6 levels showed no significant differences between the groups. Conclusion: COVID-19 vaccination with either AstraZeneca or Pfizer-BioNTech does not adversely affect sperm parameters or induce significant changes in serum IL-6 levels. These findings support the safety of COVID-19 vaccines concerning male reproductive health, alleviating concerns about potential adverse effects on fertility.

New real-time PCR tests for species-specific detection of Chlamydophila psittaci and Chlamydophila abortus from tissue samples

Velogenic Newcastle Disease Virus was isolated from broiler chickens in Northern Iraq. An inactivated vaccine was manufactured locally using as seed virus ELD50/ml109 and then compared with commercial inactivated vaccine in an experimental study which included 120 broiler chicks divided into three groups (G1 unvaccinated control, G2 for commercial vaccine and G3 for local vaccine). The chicks were injected subcutaneously at 3 days old followed by booster Lasota live vaccine eye drop. Indirect ELISA technique was used to estimate the antibody titer from the collected sera of chicks at age 7, 17 and 27 days (pre-challenge) and challenged at 31 days old with the same virus. The results indicated that there were significant differences (P<0.05) between vaccinated group G2 and G3 at 27th day old and showed a high antibody level with high protection percentage compared with the control. G1 which shown no survival, 100% mortality and severe histopathological lesions, while in G2 and G3 was 43% and 87% respectively. Post-challenge antibody titers of survival chicks showed in G3 significantly over the G2 with less severe histopathological lesions. This study concluded that vaccine failure could occur due to factors of the immune status of the host, improper storage of vaccine, improper vaccination and variant pathogenic virus strain. More epidemiological surveillances are required to decide the actual impact of the disease in poultry farms and matching the vaccines.

<p><strong>Background.</strong> Ovine Enzootic Abortion is a contagious infectious disease caused by a Gram negative and obligate intracellular bacterium, <em>Chlamydia abortus</em>. For field diagnosis, commercial serological tests are used; however, some of these tests show low sensitivity and specificity rates, due to the cross-reactions that the antigens used have against other pathogens. For the most accurate diagnosis, it is necessary to develop tests with more specific antigens such as polymorphic membrane proteins (Pmp's), that allow to determine the presence of specific epitopes using new technologies. <strong>Objective.</strong> To determine <em>in silico</em> the presence of epitopes with specific immunogenic potential against <em>Chlamydia abortus</em> of two fragments of the PMP17G protein. <strong>Methodology.</strong> The cloning and sequencing of the fragments was carried out from a field isolate of <em>Chlamydia abortus</em>, and from the analysis of these sequences, with the help of two bioinformatics software’s. <strong>Results.</strong> Several epitopes from <em>Chlamydia abortus</em> were found, rPOMP90-3 (eight epitopes) and rPOMP90-4 (one epitope). <strong>Implications.</strong> Bioinformatics analysis indicated that both fragments of the protein have the capacity to activate the immune system, which would be useful for the development of diagnostic kits and immunogens. <strong>Conclusions.</strong> The <em>in silico</em> analysis allowed to efficiently predict and identify specific epitopes against <em>Chlamydia abortus</em> in both fragments of the protein. </p>

Comparative evaluation of ELPylated virus-like particle vaccine with two commercial PCV2 vaccines by experimental challenge

Background/Objectives: Swine influenza A virus (swIAV), a prevalent respiratory pathogen in porcine populations, poses substantial economic losses to global livestock industries and represents a potential threat to public health security. Neuraminidase (NA) has been proposed as an important component for universal influenza vaccine development. NA has potential advantages as a vaccine antigen in providing cross-protection, with specific antibodies that have a broad binding capacity for heterologous viruses. In this study, we evaluated the immunogenicity and protective efficacy of a tetrameric recombinant NA subunit vaccine in a swine model. Methods: We constructed and expressed structurally stable soluble tetrameric recombinant NA (rNA) and prepared subunit vaccines by mixing with ISA 201 VG adjuvant. The protective efficacy of rNA-ISA 201 VG was compared to that of a commercial whole inactivated virus vaccine. Pigs received a prime-boost immunization (14-day interval) followed by homologous viral challenge 14 days post-boost. Results: Both rNA-ISA 201 VG and commercial vaccine stimulated robust humoral responses. Notably, the commercial vaccine group exhibited high viral-binding antibody titers but very weak NA-specific antibodies, whereas rNA-ISA 201 VG immunization elicited high NA-specific antibody titers alongside substantial viral-binding antibodies. Post-challenge, both immunization with rNA-ISA 201 VG and the commercial vaccine were effective in inhibiting viral replication, reducing viral load in porcine respiratory tissues, and effectively mitigating virus-induced histopathological damage, as compared to the PBS negative control. Conclusions: These findings found that the anti-NA immune response generated by rNA-ISA 201 VG vaccination provided protection comparable to that of a commercial inactivated vaccine that primarily induces an anti-HA response. Given that the data are derived from one pig per group, there is a requisite to increase the sample size for more in-depth validation. This work establishes a novel strategy for developing next-generation SIV subunit vaccines leveraging NA as a key immunogen.