Immunogenicity of a recombinant hemagglutinin neuraminidase-Porcine rubulavirus produced by Escherichia coli of Porcine rubulavirus gives protective immunity of litter after challenge.

Porcine rubulavirus (PRV) is a contagious virus that affects the Mexican swine industry. This work aimed to evaluate the immunogenicity of an recombinant hemagglutinin neuraminidase-Porcine rubulavirus (rHN-PorPV) candidate vaccine on pregnant sows, and the protective efficacy afforded to their 7-day-old suckling piglets against PRV lethal challenge. Three sows were immunized with rHN-PorPV formulated with immune-stimulating complex (ISCOMs) and two sows with rHN-PorPV protein alone as well as a mock-immunized pregnant sow (negative control). Quantitative ELISA detected a high concentration of anti-rHN-PorPV Immunoglobulin G (IgG) antibodies in sow sera after the second dose of vaccine administered on day 14 until farrowing, showing viral-neutralizing and cross-neutralization activity against different variants of PRV. Sera samples from piglets of immunized sows (with or without adjuvant), showed high concentrations of IgG antibodies. As expected, piglets from the negative control sow (n=5), exhibited severe signs of disease and 100% of mortality after PRV challenge study. Conversely, 75% and 87.5% of the piglets born from the rHN-PorPV and the rHN-PorPV-ISCOMs-immunized sows (n=8), survived, respectively, showing milder PRV clinical signs. Our data indicate that rHN-PorPV candidate vaccine produced in Escherichia coli induces efficient humoral response in pregnant sows and that the maternally derived immunity provides high protection to suckling piglets against PRV lethal challenge.

Combined Subcutaneous-Intranasal Immunization With Epitope-Based Antigens Elicits Binding and Neutralizing Antibody Responses in Serum and Mucosae Against PRRSV-2 and SARS-CoV-2.

New vaccine design approaches, platforms, and immunization strategies might foster antiviral mucosal effector and memory responses to reduce asymptomatic infection and transmission in vaccinated individuals. Here, we investigated a combined parenteral and mucosal immunization scheme to induce local and serum antibody responses, employing the epitope-based antigens 3BT and NG19m. These antigens target the important emerging and re-emerging viruses PRRSV-2 and SARS-CoV-2, respectively. We assessed two versions of the 3BT protein, which contains conserved epitopes from the GP5 envelope protein of PRRSV-2: soluble and expressed by the recombinant baculovirus BacDual-3BT. On the other hand, NG19m, comprising the receptor-binding motif of the S protein of SARS-CoV-2, was evaluated as a soluble recombinant protein only. Vietnamese mini-pigs were immunized employing different inoculation routes: subcutaneous, intranasal, or a combination of both (s.c.-i.n.). Animals produced antigen-binding and neut1ralizing antibodies in serum and mucosal fluids, with varying patterns of concentration and activity, depending on the antigen and the immunization schedule. Soluble 3BT was a potent immunogen to elicit binding and neutralizing antibodies in serum, nasal mucus, and vaginal swabs. The vectored immunogen BacDual-3BT induced binding antibodies in serum and mucosae, but PRRSV-2 neutralizing activity was found in nasal mucus exclusively when administered intranasally. NG19m promoted serum and mucosal binding antibodies, which showed differing neutralizing activity. Only serum samples from subcutaneously immunized animals inhibited RBD-ACE2 interaction, while mini-pigs inoculated intranasally or via the combined s.c.-i.n. scheme produced subtle neutralizing humoral responses in the upper and lower respiratory mucosae. Our results show that intranasal immunization, alone or combined with subcutaneous delivery of epitope-based antigens, generates local and systemic binding and neutralizing antibodies. Further investigation is needed to evaluate the capability of the induced responses to prevent infection and reduce transmission.

CD71+ Erythroid Cells in Human Neonates Exhibit Immunosuppressive Properties and Compromise Immune Response Against Systemic Infection in Neonatal Mice.

Newborns are highly susceptible to infectious diseases. The underlying mechanism of neonatal infection susceptibility has generally been related to their under-developed immune system. Nevertheless, this notion has recently been challenged by the discovery of the physiological abundance of immunosuppressive erythroid precursors CD71+erythroid cells (CECs) in newborn mice and human cord blood. Here, as proof of concept, we show that these cells are also abundant in the peripheral blood of human newborns. Although their frequency appears to be more variable compared to their counterparts in mice, they rapidly decline by 4 weeks of age. However, their proportion remains significantly higher in infants up to six months of age compared to older infants. We found CD45 expressing CECs, as erythroid progenitors, were the prominent source of reactive oxygen species (ROS) production in both humans and mice. Interestingly, a higher proportion of CD45+CECs was observed in the spleen versus bone marrow of neonatal mice, which was associated with a higher ROS production by splenic CECs compared to their siblings in the bone marrow. CECs from human newborns suppressed cytokine production by CD14 monocytes and T cells, which was partially abrogated by apocynin in vitro. Moreover, the depletion of CECs in neonatal mice increased the number of activated effector immune cells in their spleen and liver, which rendered them more resistant to Listeria monocytogenes infection. This was evident by a significant reduction in the bacteria load in the spleen, liver and brain of treated-mice compared to the control group, which enhanced their survival rate. Our finding highlights the immunoregulatory processes mediated by CECs in newborns. Thus, such tightly regulated immune system in newborns/infants may explain one potential mechanism for the asymptomatic or mild COVID-19 infection in this population.

Postnatal development of lung T lymphocytes in a porcine model.

PURPOSE: Despite the high prevalence of respiratory diseases in the world and the extensive information available on the mucosal immune system, research on the development of the lung immune system in humans is limited by technical and ethical considerations; therefore, we studied the postnatal development of T lymphocytes in lung lobes in a porcine model. METHODS: Using less than 36-hour-old (NB), 1-week-weaned (5-week-old -AW-), 3-month-old (3M), and 4-year-old (4YR) healthy, nonvaccinated, specific pathogen free (SPF) Vietnamese miniature pigs, we studied the CD3+, CD4+, CD8+, TCR1 (gamma-delta T cells), and CD25+ (IL-2R-alpha) cell subpopulations in lung lobes parenchyma, bronchoalveolar lavage (BAL), peripheral blood mononuclear cells (PBMC), and cervical lymph nodes (LN) by flow cytometry. RESULTS: No differences among lung lobes were detected in any of the cell subpopulations tested. A low proportion of T cell subsets was detected in NB and 4YR groups in lung and BAL. Besides, the AW and 3M groups showed important changes in T cell subpopulations. CONCLUSIONS: These results suggest that in healthy animals the lung lobes behave as a homogeneous immune organ. T cells were detected in very low percentages at birth and in adult life, which may explain the high susceptibility to respiratory infections both early and later in life. Postweaning antigenic challenges and endocrine and sexual maturity at 3M had important effects on the development of the mucosal immune system. It was also evident that changes at mucosal sites were poorly correlated with PBMC and LN.

Effect of age and maternal antibodies on the systemic and mucosal immune response after neonatal immunization in a porcine model.

Newborn mammals are highly susceptible to respiratory infections. Although maternal antibodies (MatAb) offer them some protection, they may also interfere with their systemic immune response to vaccination. However, the impact of MatAb on the neonatal mucosal immune response remains incompletely described. This study was performed to determine the effect of ovalbumin (OVA) -specific MatAb on the anti- OVA antibody response in sera, nasal secretions and saliva from specific pathogen-free Vietnamese miniature piglets immunized at 7 or 14 days of age. Our results demonstrated that MatAb increased antigen-specific IgA and IgG responses in sera, and transiently enhanced an early secretory IgA response in nasal secretions of piglets immunized at 7 days of age. In contrast, we detected a lower mucosal (nasal secretion and saliva) anti- OVA IgG response in piglets with MatAb immunized at 14 days of age, compared with piglets with no MatAb, suggesting a modulatory effect of antigen-specific maternal factors on the isotype transfer to the mucosal immune exclusion system. In our porcine model, we demonstrated that passive maternal immunity positively modulated the systemic and nasal immune responses of animals immunized early in life. Our results, therefore, open the possibility of inducing systemic and respiratory mucosal immunity in the presence of MatAb through early vaccination.

Preparation and characterization of a monoclonal antibody specific to histone acetyltransferase from Plasmodium falciparum.

We have obtained a specific monoclonal antibody (MAb) against the Plasmodium falciparum histone acetyl transferase (PfGcn5), a transcriptional factor that possesses HAT activity directed to the amino terminal of histone H3. To prepare this antibody, a 968-base pair (bp) DNA fragment of PfGcn5 gene corresponding to C-terminal domain was obtained by RT-PCR and cloned into prokaryotic expression vector pGEX-4T3. MAb against PfGcn5 was obtained with hybridoma technique and ELISA screening using either purified GSTPfGcn5 protein or purified GST protein alone as a control. One MAb, named Pf.r2, was able to identify the PfGcn5 protein in nuclear extract from P. falciparum and immunofluorescence assays. This MAb will be a helpful tool to perform a variety of assays to identify the other components of PfGcn5 complexes.