Evidence of reduced vertical transmission of Neospora caninum associated with higher IgG1 than IgG2 serum levels and presence of IFN-γ in non-aborting chronically infected cattle under natural condition

Vertical transmission of Neospora caninum from three generations of naturally infected dairy cattle from Brazil

Neospora caninum is a major cause of abortion in dairy cattle, and vertical transmission is considered the most relevant route. The present study aimed to evaluate the vertical transmission of N. caninum from three generations of naturally infected dairy cows. The indirect immunofluorescence assay (IFA) for IgG anti-N. caninum was used for the serodiagnosis, considering titles ≥100 as positive for cows and calves. A total of 152 pregnant dams were selected from farms in the State of São Paulo, and 37 (24.3 %), which gave birth to heifers were selected. These animals (first generation, F1) were divided into 18 (48.7 %) seropositive (1G+), and 19 (51.3 %) seronegative (1G-) animals. In the second generation (2G), sixteen calves (89 %) that were born from 1G+ were seropositive; however, no calves (0 %) were born positive from 1G-. The risk for vertical neosporosis transmission was approximately 34.6 times higher in 1G+ than in 1G- (OD = 34.6, IC 2.2-537, p < 0.00001). Finally, only four animals from 2G were followed up, and 3G (third generation) calves were born; three calves were sera positive from three positive cows (3/3, 100 %), and one negative cow did not transmit N. caninum to offspring. Herein, a higher risk of vertical transmission was observed in N. caninum sera-positive than in sera-negative cows.

[Report of a field control experience of bovine viral diarrhea virus in 2 dairy farms of Argentina applying management, diagnostic, and vaccination tools]

Bovine viral diarrhea virus (BVDV) causes significant economic losses in the international livestock industry and in Argentina, where it circulates at high prevalence. Under high prevalence conditions, BVDV infections are controlled through vaccination once persistently infected animals are identified and segregated. This study evaluated the feasibility of controlling BVDV circulation under field conditions by combining diagnosis, management measures, and vaccination in 2 dairy farms in the province of Santa Fe. Commercial ELISAs were used for the detection of the NS3 (P80) protein or antibodies against this protein as well as an RT-nested PCR for the detection of the viral genome, and viral seroneutralization to assess vaccine efficacy. The average seroprevalence of the farms was 58.4%, with a persistently infected animal rate of 2.4%. After segregating the persistently infected animals and vaccinating them with a commercial combined vaccine containing inactivated BVDV, abortion rates significantly decreased (p<0.05) in farm 1 (from 20.5 to 11.6%) and in farm 2 (from 34 to 23.4%) during the second year of the control strategy. Conception rates increased from 29 to 33% in farm 1 during the first year, while in farm 2, the increase was 7 points during the second year. This methodology achieved conditions in which BVDV ceased to circulate, constituting the first controlled report on BVDV management in dairy farms using tools available to producers in Argentina.

Immunogenicity, safety and dual DIVA-like character of a recombinant candidate vaccine against neosporosis in cattle

Neosporosis is the major infectious cause of abortion and reproductive losses in cattle worldwide; however, there are no available vaccines or drugs to control this disease. Recently, a dual (positive and negative) DIVA-like (Differentiation of Infected from Vaccinated Animals) vaccine was evaluated in a pregnant mouse model of neosporosis, showing promising immunogenic and protective results. The current report aimed to study the safety, the dose-dependent immunogenicity and the dual DIVA-like character of a recombinant subunit vaccine composed of the major surface antigen from Neospora caninum (rNcSAG1) and the carrier/adjuvant Heat shock protein 81.2 from Arabidopsis thaliana (rAtHsp81.2) in cattle. Healthy heifers were separated and assigned to experimental groups A-F and subcutaneously immunized with 2 doses of vaccine formulations 30 days apart as follows: A (n = 4): 50 μg rNcSAG1 + 150 μg rAtHsp81.2; B (n = 4): 200 μg rNcSAG1 + 600 μg rAtHsp81.2; C (n = 4): 500 μg rNcSAG1 + 1,500 μg rAtHsp81.2; D (n = 3): 150 μg rAtHsp81.2; E (n = 3):1,500 μg rAtHsp81.2, and F (n = 3) 2 ml of sterile PBS. The immunization of heifers with the different vaccine or adjuvant doses (groups A-E) was demonstrated to be safe and did not modify the mean value of the evaluated serum biomarkers of metabolic function (GOT/ASP, GPT/ALT, UREA, Glucose and total proteins). The kinetics and magnitude of the immune responses were dose-dependent. The higher dose of the vaccine formulation (group C) stimulated a broad and potent humoral and cellular immune response, characterized by an IgG1/IgG2 isotype profile and IFN-γ secretion. In addition, this was the first time that dual DIVA-like character of a vaccine against neosporosis was demonstrated, allowing us to differentiate vaccinated from infected heifers by two different DIVA compliant test approaches. These results encourage us to evaluate its protective efficacy in infected pregnant cattle in the future.

Protective effect of Inonotus obliquus polysaccharide on mice infected with Neospora caninum

The study aimed to explore the protective effects of Inonotus obliquus polysaccharide (IOP) on Neospora caninum (N. caninum) infection. Our data showed that the survival rate of the mice was the highest and the survival time was the longest when the IOP was 2 mg/10 g. In agreement with these observations, IOP alleviated the pathological damage in the various organs and tissues of the mice. Compared with that in the Neosporidium infection model group, the content of N. caninum in the heart, liver, spleen, lung, kidney and brain, determined through HE staining, was significantly lower. In addition, IOP inhibited the levels of immunoglobulin G1 (IgG1) and immunoglobulin G2 (IgG2a) from the 21st to 42nd day of the administration group, whereas the levels of interleukin-12 (IL-12) and serum tumor necrosis factor alpha (TNF-α) were down-regulated at 7 d - 42 d. The production of CD4+ T lymphocytes was promoted, the number of CD8+ T lymphocytes were significantly lower and the CD4+/CD8+ ratio was significantly elevated. Furthermore, IOP effectively balanced the levels of hormones including gonadotropin-releasing hormone (GnRH), luteotropic hormone (LH) and testosterone (T) in male mice, and progesterone (PROG), estradiol (E2) and prolactin (PRL) in female mice. These findings demonstrate that IOP exerts protective effects against pathological damage caused by N. caninum infection in mice, and improve the immune function of the organism and regulate the secretion balance of sex hormones.

Protective Effect against Neosporosis Induced by Intranasal Immunization with Neospora caninum Membrane Antigens Plus Carbomer-Based Adjuvant

Neospora caninum is an obligate intracellular protozoan responsible for abortion and stillbirths in cattle. We previously developed a mucosal vaccination approach using N. caninum membrane proteins and CpG adjuvant that conferred long-term protection against neosporosis in mice. Here, we have extended this approach by alternatively using the carbomer-based adjuvant Carbigen™ in the immunizing preparation. Immunized mice presented higher proportions and numbers of memory CD4⁺ and CD8⁺ T cells. Stimulation of spleen, lungs and liver leukocytes with parasite antigens induced a marked production of IFN-γ and IL-17A and, less markedly, IL-4. This balanced response was also evident in that both parasite-specific IgG1 and IgG2c were raised by immunization, together with specific intestinal IgA. Upon intraperitoneal infection with N. caninum, immunized mice presented lower parasitic burdens than sham-immunized controls. In the infected immunized mice, memory CD4⁺ T cells predominantly expressed T-bet and RORγt, and CD8⁺ T cells expressing T-bet were found increased. While spleen, lungs and liver leukocytes of both immunized and sham-immunized infected animals produced high amounts of IFN-γ, only the cells from immunized mice responded with high IL-17A production. Since in cattle both IFN-γ and IL-17A have been associated with protective mechanisms against N. caninum infection, the elicited cytokine profile obtained using Carbigen^TM as adjuvant indicates that it could be worth exploring for bovine neosporosis vaccination.

Protective Immunity Against Neospora caninum Infection Induced by 14-3-3 Protein in Mice

Neospora caninum is an apicomplexan parasite that infects many mammals and remains a threatening disease worldwide because of the lack of effective drugs and vaccines. Our previous studies demonstrated that N. caninum 14-3-3 protein (Nc14-3-3), which is included in N. caninum extracellular vesicles (NEVs), can induce effective immune responses and stimulate cytokine expression in mouse peritoneal macrophages. However, whether Nc14-3-3 has a protective effect and its mechanisms are poorly understood. Here, we evaluated the immune responses and protective effects of Nc14-3-3 against exposure to 2 × 10⁷ Nc-1 tachyzoites. Antibody (IgG, IgGl, and IgG2a) levels and Th1-type (IFN-γ and IL-12) and Th2-type (IL-4 and IL-10) cytokines in mouse serum, survival rates, survival times, and parasite burdens were detected. In the present study, the immunostimulatory effect of Nc14-3-3 was confirmed, as it triggered Th1-type cytokine (IFN-γ and IL-12) production in mouse serum 2 weeks after the final immunization. Moreover, the immunization of C57BL/6 mice with Nc14-3-3 induced high IgG antibody levels and significant increases in CD8⁺ T lymphocytes in the spleens of mice, indicating that the cellular immune response was significantly stimulated. Mouse survival rates and times were significantly prolonged after immunization; the survival rates were 40% for Nc14-3-3 immunization and 60% for NEV immunization, while mice that received GST, PBS, or blank control all died at 13, 9, or 8 days, respectively, after intraperitoneal N. caninum challenge. In addition, qPCR analysis indicated that there was a reduced parasite burden and diminished pathological changes in the mice immunized with Nc14-3-3. Our data demonstrate that vaccination of mice with Nc14-3-3 elicits both cellular and humoral immune responses and provides partial protection against acute neosporosis. Thus, Nc14-3-3 could be an effective antigen candidate for vaccine development for neosporosis.

[Seroprevalence and risk factors associated with Neospora caninum in dairy farms from the Province of Salta, Argentina]

The objective of this work was to determine the seroprevalence of Neospora caninum in cattle in Valle de Lerma, province of Salta, Argentina, and the risk factors associated with the disease. Serum samples were taken from 40 cows in each dairy herd, which were analyzed by indirect ELISA to detect antibodies against N. caninum. Chronic and acute infections were discriminated by measuring the avidity of these antibodies. All the herds exhibited at least one seropositive animal, the mean being 35.3 ± 14.9% of positive animals. Specific antibodies were also detected in dogs present in 9of the herds, which showed a seropositivity value of 71.7% ± 19.9%. Among the seropositive animals, 56.3% showed acute infections. A negative association was found between seroprevalence and the avidity index of specific antibodies, indicating that the presence of animals with acute infections is associated with higher seroprevalence. Fields with grazing showed more recent infections. These results show for the first time the importance of this parasite in this particular region and the need to promote the development of control programs considering the different risk factors that affect the epidemiological situation of the disease.

Interplay Between Reactive Oxygen Species and the Inflammasome Are Crucial for Restriction of Neospora caninum Replication

Neospora caninum poses as a considerable threat to animal health and generates significant economic impact in livestock production worldwide. Here, we have investigated the mechanism that underlies the participation of the inflammasome complex and Reactive Oxygen Species (ROS) in the regulation of immune responses during N. caninum infection. For that purpose, we used in vitro (bone marrow derived macrophages) and in vivo mouse models of infection. Our results show that NLRP3 and NLRC4 receptors, alongside with ASC and Caspase-1, are required for proper activation of the inflammasome during N. caninum infection. As expected, the engagement of these pathways is crucial for IL-1α, IL-1β, and IL-18 production, as well as the induction of pyroptosis. Our results also show that N. caninum induces ROS production dependent of the inflammasome assembly, which in its turn also depends on MyD88/NF-κB-induced ROS to maintain its activation and, ultimately, lead to restriction of parasite replication.

From Signaling Pathways to Distinct Immune Responses: Key Factors for Establishing or Combating Neospora caninum Infection in Different Susceptible Hosts

: Neospora caninum is an intracellular protozoan parasite affecting numerous animal species. It induces significant economic losses because of abortion and neonatal abnormalities in cattle. In case of infection, the parasite secretes numerous arsenals to establish a successful infection in the host cell. In the same context but for a different purpose, the host resorts to different strategies to eliminate the invading parasite. During this battle, numerous key factors from both parasite and host sides are produced and interact for the maintaining and vanishing of the infection, respectively. Although several reviews have highlighted the role of different compartments of the immune system against N. caninum infection, each one of them has mostly targeted specific points related to the immune component and animal host. Thus, in the current review, we will focus on effector molecules derived from the host cell or the parasite using a comprehensive survey method from previous reports. According to our knowledge, this is the first review that highlights and discusses immune response at the host cell-parasite molecular interface against N. caninum infection in different susceptible hosts.