Despite teleost fish being the first animal group in which all elements of adaptive immunity are present, the lack of follicular structures, as well as the fact that systemic Ab responses rely exclusively on unswitched low-affinity IgM responses, strongly suggests that fish B cell responses resemble mammalian B1 cell responses rather than those of B2 cells. In line with this hypothesis, in the current study, we have identified a homolog of CD5 in teleost fish. This pan-T marker belonging to the scavenger receptor cysteine-rich family of receptors is commonly used in mammals to distinguish a subset of B1 cells. Subsequently, we have demonstrated that a very high percentage of teleost IgM⁺ B cells express this marker, in contrast to the limited population of CD5-expressing B1 cells found in most mammals. Furthermore, we demonstrate that fish IgM⁺ B cells share classical phenotypic features of mammalian B1 cells such as large size, high complexity, high surface IgM, and low surface IgD expression, regardless of CD5 expression. Additionally, fish IgM⁺ B cells, unlike murine B2 cells, also displayed extended survival in cell culture and did not proliferate after BCR engagement. Altogether, our results demonstrate that although fish are evolutionarily the first group in which all the elements of acquired immunity are present, in the absence of follicular structures, most teleost IgM⁺ B cells have retained phenotypical and functional characteristics of mammalian B1 cells.

In recent years, the unique properties of nanoparticles have fostered novel applications in various fields such as biology, pharmaceuticals, agriculture, and others. Unfortunately, their rapid integration into daily life has also led to environmental concerns due to uncontrolled release of nanoparticles into the aquatic environment. Despite increasing awareness of nanoparticle bioaccumulation in the aquatic environment, much remains to be learned about their impact on aquatic organisms and how to best monitor these effects. Herein, we provide the first review of innate immunity as an emerging tool to assess the health of fish following nanoparticle exposure. Fish are widely used as sentinels for aquatic ecosystem pollution and innate immune parameters offer sensitive and reliable tools that can be harnessed for evaluation of contamination events. The most frequent biomarkers highlighted in literature to date include, but are not limited to, parameters associated with leukocyte dynamics, oxidative stress, and cytokine production. Taken together, innate immunity offers finite and sensitive biomarkers for assessment of the impact of nanoparticles on fish health.

Highly pathogenic avian Influenza virus (HPAIV) has spread in an unprecedented extent globally in recent years. Despite the large reports of cases in Asia, Europe, and North America, little is known about its circulation in South America. Here, we describe the isolation, and whole genome characterization of HPAIV obtained from sampling 26 wild bird species in Peru, representing one of the largest studies in our region following the latest HPAIV introduction in South America. Out of 147 samples analyzed, 22 were positive for detection of avian influenza virus using a qRT-PCR-based assay. Following inoculation into embryonated chicken eggs, fourteen viral isolates were obtained from which nine isolates were selected for genome characterization, based on their host relevance. Our results identified the presence of HPAIV H5N1 subtype in a highly diverse wild bird species. Phylogenetic analysis revealed that these isolates correspond to the clade 2.3.4.4b, sharing a common ancestor with North American isolates and forming a monophyletic group along with isolates from Chile. Altogether, changes at the amino acid levels compared to their closest relatives indicates the virus is evolving locally, highlighting the need for constant genomic surveillance. This data evidence the chances for spillover events increases as the virus spreads into large populations of immunologically naïve avian species and adding conditions for cross species transmission.

Porcine Deltacoronavirus is a newly emergent enteric pathogen affecting swine farms worldwide. It has been detected in several countries in Europe, Asia and North America; yet, it has not been reported in South America. In November 2019, an enteric disease outbreak in a pig farm located in San Martin, Peru, was reported along with submission of three intestinal samples from pigs who succumbed to the disease. Samples were processed for molecular detection by qRT-PCR, viral isolation and further sequencing analysis. A taqman-based RT-PCR was performed to differentiate among the most relevant swine enteric coronaviruses described to date. All samples were positive to Porcine Deltacoronavirus with a cycle threshold (Ct) value between 9–14, revealing a high viral load, while testing negative to Porcine Epidemic diarrhea and Transmissible Gastroenteritis viruses. Following detection, viral isolation was performed using PK-15 and Vero cell lines. After 5 days of inoculation, no cytopathic effect was observed. A second blind passage allowed the observation of cytopathic effect on PK-15 cells, while it remained absent in Vero cells. A fluorescence test using an anti-N monoclonal antibody confirmed viral replication. One sample was processed for whole genome sequencing (WGS). In short, raw reads were imported into CLC genomics and assembled de novo. Out of 479k reads generated from the sample, 436k assembled into a 25501 bp contig which was 99.5% identical to a reference Porcine Deltacoronavirus strain from the United States within the North American phylogroup. Yet, there are relevant differences at the nucleotide and amino acid levels compared to previously described Porcine Deltacoronavirus strains. Altogether, our findings represent the first report of Porcine Deltacoronavirus in South America, which provides information of its evolutionary origin. Thus, this study offers new insights into the molecular epidemiology of Porcine Deltacoronavirus infections in the swine industry. This article is protected by copyright. All rights reserved

Infectious bronchitis is a highly contagious viral disease that represents an economic threat for poultry despite the wide use of vaccination. To characterize the virus circulating in Peru, we analyzed 200 samples, including nasopharyngeal swabs and multiple tissues collected from animals suspected of being infected with infectious bronchitis virus (IBV) between January and August in 2015. All animals had at least one positive sample for IBV by RT-PCR. Out of these positive samples, eighteen (18) were selected for viral isolation and a partial S1 sequencing. Phylogenetic analysis showed that sixteen isolates clustered with members of GI-16 lineage, also known as Q1, with nucleotide homology ranging from 93% to 98%. The two remaining isolates grouped with members of the GI-1 lineage. Our study reveals circulation of GI-16 lineage during this period in poultry systems in Peru, along with GI-1 lineage (vaccine-derived). Moreover, those IBV GI-16 isolates showed unique nucleotide and amino acid changes compared to their closest relatives. Altogether, these findings reveal the circulation of GI-16 lineage while describing changes at key regions of the S protein that might be of relevance for vaccine evasion. These results highlight the importance of genetic surveillance for improving vaccination strategies against infectious bronchitis.