Passive immunity to control Bovine coronavirus diarrhea in a dairy herd in Argentina.

Bovine coronavirus (BCoV) is a viral enteric pathogen associated with calf diarrhea worldwide being, in Argentina, mostly detected in dairy husbandry systems. The aim of the present work was to study if maternal IgG1 antibodies (Abs) to BCoV acquired by colostrum intake modulate the development of BCoV infection in calves reared in a dairy farm in Argentina. Thirty Holstein calves were monitored during their first 60 days of age. Animals were classified into two groups depending on their initial BCoV IgG1 Ab titers. The "failure of passive transfer" (FPT) group had significantly lower IgG1 Abs to BCoV than the "acceptable passive transfer" (APT) group of calves (log10 1.98 vs. 3.38 respectively) (p<0.0001). These differences were also observed when the total protein levels in both groups were compared (p=0.0081). Moreover, 71% (5/7) of calves from the FPT group showed IgG1 seroconversion to BCoV compared to 29.4% (5/17) of animals from the APT group. Regarding viral circulation, BCoV was detected in 10% (3/30) of all calves and BCoV IgG1 Ab seroconversion was detected in 42% of the total animals showing that almost half of the calves were infected with BCoV. In conclusion, calves with high titers of specific BCoV IgG1 (≥1024) were mostly protected against viral infection, while animals with low titers of IgG1 (<1024) were mostly infected with BCoV. IgG1 Abs from colostrum origin are critical for prevention of BCoV infection.

Recombinant monovalent llama-derived antibody fragments (VHH) to rotavirus VP6 protect neonatal gnotobiotic piglets against human rotavirus-induced diarrhea.

Group A Rotavirus (RVA) is the leading cause of severe diarrhea in children. The aims of the present study were to determine the neutralizing activity of VP6-specific llama-derived single domain nanoantibodies (VHH nanoAbs) against different RVA strains in vitro and to evaluate the ability of G6P[1] VP6-specific llama-derived single domain nanoantibodies (VHH) to protect against human rotavirus in gnotobiotic (Gn) piglets experimentally inoculated with virulent Wa G1P[8] rotavirus. Supplementation of the daily milk diet with 3B2 VHH clone produced using a baculovirus vector expression system (final ELISA antibody -Ab- titer of 4096; virus neutralization -VN- titer of 256) for 9 days conferred full protection against rotavirus associated diarrhea and significantly reduced virus shedding. The administration of comparable levels of porcine IgG Abs only protected 4 out of 6 of the animals from human RVA diarrhea but significantly reduced virus shedding. In contrast, G6P[1]-VP6 rotavirus-specific IgY Abs purified from eggs of hyperimmunized hens failed to protect piglets against human RVA-induced diarrhea or virus shedding when administering similar quantities of Abs. The oral administration of VHH nanoAb neither interfered with the host's isotype profiles of the Ab secreting cell responses to rotavirus, nor induced detectable host Ab responses to the treatment in serum or intestinal contents. This study shows that the oral administration of rotavirus VP6-VHH nanoAb is a broadly reactive and effective treatment against rotavirus-induced diarrhea in neonatal pigs. Our findings highlight the potential value of a broad neutralizing VP6-specific VHH nanoAb as a treatment that can complement or be used as an alternative to the current strain-specific RVA vaccines. Nanobodies could also be scaled-up to develop pediatric medication or functional food like infant milk formulas that might help treat RVA diarrhea.

Controlling Rotavirus-associated diarrhea: Could single-domain antibody fragments make the difference?

Group A Rotavirus (RVA) remains a leading cause of severe diarrhea and child mortality. The variable domain of camelid heavy chain antibodies (VHH) display potent antigen-binding capacity, have low production costs and are suitable for oral therapies. Two sets of anti-RVA VHHs have been developed: ARP1-ARP3; 2KD1-3B2. Here, we explore the potential of both sets as a prevention strategy complementary to vaccination and a treatment option against RVA-associated diarrhea in endangered populations. Both sets have been expressed in multiple production systems, showing extensive neutralizing capacity against strains of RVA in vitro. They were also tested in the neonatal mouse model with various degrees of success in preventing or treating RVA-induced diarrhea. Interestingly, mitigation of the symptoms was also achieved with freeze-dried ARP1, so that it could be applied in areas where cold chains are difficult to maintain. 3B2 was tested in a pre-clinical trial involving gnotobiotic piglets where it conferred complete protection against RVA-induced diarrhea. ARP1 was used in the first clinical trial for anti-RVA VHHs, successfully reducing stool output in infants with RVA diarrhea, with no detected side effects.

Development of an IgY-Based Treatment to Control Bovine Coronavirus Diarrhea in Dairy Calves.

Bovine Coronavirus (BCoV) is a major pathogen associated with neonatal calf diarrhea. Standard practice dictates that to prevent BCoV diarrhea, dams should be immunized in the last stage of pregnancy to increase BCoV-specific antibody (Ab) titers in serum and colostrum. For the prevention to be effective, calves need to suck maternal colostrum within the first six to twelve hours of life before gut closure to ensure a good level of passive immunity. The high rate of maternal Ab transfer failure resulting from this process posed the need to develop alternative local passive immunity strategies to strengthen the prevention and treatment of BCoV diarrhea. Immunoglobulin Y technology represents a promising tool to address this gap. In this study, 200 laying hens were immunized with BCoV to obtain spray-dried egg powder enriched in specific IgY Abs to BCoV on a large production scale. To ensure batch-to-batch product consistency, a potency assay was statistically validated. With a sample size of 241, the BCoV-specific IgY ELISA showed a sensitivity and specificity of 97.7% and 98.2%, respectively. ELISA IgY Abs to BCoV correlated with virus-neutralizing Ab titers (Pearson correlation, R2 = 0.92, p < 0.001). Most importantly, a pilot efficacy study in newborn calves showed a significant delay and shorter duration of BCoV-associated diarrhea and shedding in IgY-treated colostrum-deprived calves. Calves were treated with milk supplemented with egg powder (final IgY Ab titer to BCoV ELISA = 512; VN = 32) for 14 days as a passive treatment before a challenge with BCoV and were compared to calves fed milk with no supplementation. This is the first study with proof of efficacy of a product based on egg powder manufactured at a scale that successfully prevents BCoV-associated neonatal calf diarrhea.

Anti-VP6 VHH: An Experimental Treatment for Rotavirus A-Associated Disease.

Species A Rotaviruses (RVA) remain a leading cause of mortality in children under 5 years of age. Current treatment options are limited. We assessed the efficacy of two VP6-specific llama-derived heavy chain antibody fragments (VHH) -2KD1 and 3B2- as an oral prophylactic and therapeutic treatment against RVA-induced diarrhea in a neonatal mouse model inoculated with virulent murine RVA (ECw, G16P[16]I7). Joint therapeutic administration of 2KD1+3B2 (200 µg/dose) successfully reduced diarrhea duration, RVA infection severity and virus shedding in feces. While the same dose of 2KD1 or 3B2 (200 µg) significantly reduced duration of RVA-induced diarrhea, 2KD1 was more effective in diminishing the severity of intestinal infection and RVA shedding in feces, perhaps because 2KD1 presented higher binding affinity for RVA particles than 3B2. Neither prophylactic nor therapeutic administration of the VHH interfered with the host's humoral immune response against RVA. When 2KD1 (200 µg) was administered after diarrhea development, it also significantly reduced RVA intestinal infection and fecal shedding. Host antibody responses against the oral VHH treatment were not detected, nor did viral escape mutants. Our findings show that oral administration of anti-VP6 VHH constitute, not only an effective prophylactic treatment against RVA-associated diarrhea, but also a safe therapeutic tool against RVA infection, even once diarrhea is present. Anti-VP6 VHH could be used complementary to ongoing vaccination, especially in populations that have shown lower immunization efficacy. These VHH could also be scaled-up to develop pediatric medication or functional food like infant milk formulas that might help treat RVA diarrhea.

Molecular detection of bovine Noroviruses in Argentinean dairy calves: Circulation of a tentative new genotype.

Bovine noroviruses are enteric pathogens detected in fecal samples of both diarrheic and non-diarrheic calves from several countries worldwide. However, epidemiological information regarding bovine noroviruses is still lacking for many important cattle producing countries from South America. In this study, three bovine norovirus genogroup III sequences were determined by conventional RT-PCR and Sanger sequencing in feces from diarrheic dairy calves from Argentina (B4836, B4848, and B4881, all collected in 2012). Phylogenetic studies based on a partial coding region for the RNA-dependent RNA polymerase (RdRp, 503 nucleotides) of these three samples suggested that two of them (B4836 and B4881) belong to genotype 2 (GIII.2) while the third one (B4848) was more closely related to genotype 1 (GIII.1) strains. By deep sequencing, the capsid region from two of these strains could be determined. This confirmed the circulation of genotype 1 (B4848) together with the presence of another sequence (B4881) sharing its highest genetic relatedness with genotype 1, but sufficiently distant to constitute a new genotype. This latter strain was shown in silico to be a recombinant: phylogenetic divergence was detected between its RNA-dependent RNA polymerase coding sequence (genotype GIII.2) and its capsid protein coding sequence (genotype GIII.1 or a potential norovirus genotype). According to this data, this strain could be the second genotype GIII.2_GIII.1 bovine norovirus recombinant described in literature worldwide. Further analysis suggested that this strain could even be a potential norovirus GIII genotype, tentatively named GIII.4. The data provides important epidemiological and evolutionary information on bovine noroviruses circulating in South America.

IgY antibodies protect against human Rotavirus induced diarrhea in the neonatal gnotobiotic piglet disease model.

Group A Rotaviruses are the most common cause of severe, dehydrating diarrhea in children worldwide. The aim of the present work was to evaluate protection against rotavirus (RV) diarrhea conferred by the prophylactic administration of specific IgY antibodies (Ab) to gnotobiotic piglets experimentally inoculated with virulent Wa G1P[8] human rotavirus (HRV). Chicken egg yolk IgY Ab generated from Wa HRV hyperimmunized hens specifically recognized (ELISA) and neutralized Wa HRV in vitro. Supplementation of the RV Ab free cow milk diet with Wa HRV-specific egg yolk IgY Ab at a final ELISA Ab titer of 4096 (virus neutralization -VN- titer = 256) for 9 days conferred full protection against Wa HRV associated diarrhea and significantly reduced virus shedding. This protection was dose-dependent. The oral administration of semi-purified passive IgY Abs from chickens did not affect the isotype profile of the pig Ab secreting cell (ASC) responses to Wa HRV infection, but it was associated with significantly fewer numbers of HRV-specific IgA ASC in the duodenum. We further analyzed the pigs immune responses to the passive IgY treatment. The oral administration of IgY Abs induced IgG Ab responses to chicken IgY in serum and local IgA and IgG Ab responses to IgY in the intestinal contents of neonatal piglets in a dose dependent manner. To our knowledge, this is the first study to show that IgY Abs administered orally as a milk supplement passively protect neonatal pigs against an enteric viral pathogen (HRV). Piglets are an animal model with a gastrointestinal physiology and an immune system that closely mimic human infants. This strategy can be scaled-up to inexpensively produce large amounts of polyclonal IgY Abs from egg yolks to be applied as a preventive and therapeutic passive Ab treatment to control RV diarrhea.

Hacia el control de la diarrea por rotavirus A: ¿podrían los nanoanticuerpos VHH marcar la diferencia? / Controlling rotavirus-associated diarrhea: could single-domain antibody fragments make the difference?

Los rotavirus del grupo A (RVA) constituyen la principal causa de diarrea grave y mortalidad infantil. La porción variable de los anticuerpos de cadena pesada derivados de camélidos presentan una amplia capacidad de unión antigénica (reconocen sitios antigénicos no accesibles a los anticuerpos tradicionales, con elevada afinidad) tienen bajos costos de producción y resultan ideales para las terapias orales. A la fecha, se desarrollaron 2 pares de nanoanticuerpos VHH contra RVA: ARP1-ARP3 y 2KD1-3B2. En este trabajo, exploramos el potencial de ambos grupos de nanoanticuerpos como estrategias de prevención complementarias a la vacunación y como una opción de tratamiento frente a la diarrea asociada a RVA en poblaciones de riesgo. Ambos pares de nanoanticuerpos fueron expresados en diferentes sistemas de producción y mostraron amplia capacidad neutralizante contra diversas cepas de RVA in vitro. También fueron usados en el modelo de ratón lactante, en el que evidenciaron distintos grados de éxito en la prevención o el tratamiento de la diarrea inducida por RVA. Es interesante destacar que la mitigación de los síntomas también se logró con ARP1 liofilizado y conservado, por lo que podría ser utilizado en áreas donde es difícil mantener la cadena de frío. Asimismo, 3B2 fue testeado en una prueba preclínica utilizando como modelo al cerdo gnotobiótico, al cual confirió completa protección contra la diarrea inducida por RVA. ARP1 fue usado en la primera prueba clínica de nanoanticuerpos VHH contra RVA, donde redujo significativamente las deposiciones en pacientes pediátricos con diarrea positivos para RVA, sin evidenciar ninguna reacción adversa

Group A Rotavirus (RVA) remains a leading cause of severe diarrhea and child mortality. The variable domain of camelid heavy chain antibodies (VHH) display potent antigen-binding capacity, have low production costs and are suitable for oral therapies. Two sets of anti-RVA VHHs have been developed: ARP1-ARP3; 2KD1-3B2. Here, we explore the potential of both sets as a prevention strategy complementary to vaccination and a treatment option against RVA-associated diarrhea in endangered populations. Both sets have been expressed in multiple production systems, showing extensive neutralizing capacity against strains of RVA in vitro. They were also tested in the neonatal mouse model with various degrees of success in preventing or treating RVA-induced diarrhea. Interestingly, mitigation of the symptoms was also achieved with freeze-dried ARP1, so that it could be applied in areas where cold chains are difficult to maintain. 3B2 was tested in a pre-clinical trial involving gnotobiotic piglets where it conferred complete protection against RVA-induced diarrhea. ARP1 was used in the first clinical trial for anti-RVA VHHs, successfully reducing stool output in infants with RVA diarrhea, with no detected side effects