Adaptation to specialized diets often requires modifications at both genomic and microbiome levels. We applied a hologenomic approach to the common vampire bat (Desmodus rotundus), one of the only three obligate blood-feeding (sanguivorous) mammals, to study the evolution of its complex dietary adaptation. Specifically, we assembled its high-quality reference genome (scaffold N50=26.9 Mb, contig N50=36.6 Kb) and gut metagenome, and compared them against those of insectivorous, frugivorous, and carnivorous bats. Our analyses showed i) a particular common vampire bat genomic landscape regarding integrated viral elements, ii) a dietary and phylogenetic influence on gut microbiome taxonomic and functional profiles, and iii) that both genetic elements harbor key traits related to the nutritional (e.g. vitamins and lipids shortage) and non-nutritional challenges (e.g. nitrogen waste and osmotic homeostasis) of sanguivory. These findings highlight the value of a holistic study of both host and microbiota when attempting to decipher adaptations underlying radical dietary lifestyles.

We characterized the nucleic acid-sensing Toll-like receptors (TLR) of a New World bat species, the common vampire bat (Desmodus rotundus), and through a comparative molecular evolutionary approach searched for general adaptation patterns among the nucleic acid-sensing TLRs of eight different bats species belonging to three families (Pteropodidae, Vespertilionidae and Phyllostomidae). We found that the bat TLRs are evolving slowly and mostly under purifying selection and that the divergence pattern of such receptors is overall congruent with the species tree, consistent with the evolution of many other mammalian nuclear genes. However, the chiropteran TLRs exhibited unique mutations fixed in ligand-binding sites, some of which involved nonconservative amino acid changes and/or targets of positive selection. Such changes could potentially modify protein function and ligand-binding properties, as some changes were predicted to alter nucleic acid binding motifs in TLR 9. Moreover, evidence for episodic diversifying selection acting specifically upon the bat lineage and sublineages was detected. Thus, the long-term adaptation of chiropterans to a wide variety of environments and ecological niches with different pathogen profiles is likely to have shaped the evolution of the bat TLRs in an order-specific manner. The observed evolutionary patterns provide evidence for potential functional differences between bat and other mammalian TLRs in terms of resistance to specific pathogens or recognition of nucleic acids in general.

No abstract

Gammaherpesviruses (γHVs) are generally considered host specific and to have codiverged with their hosts over millions of years. This tenet is challenged here by broad-scale phylogenetic analysis of two viral genes using the largest sample of mammalian γHVs to date, integrating for the first time bat γHV sequences available from public repositories and newly generated viral sequences from two vampire bat species (Desmodus rotundus and Diphylla ecaudata). Bat and primate viruses frequently represented deep branches within the supported phylogenies and clustered among viruses from distantly related mammalian taxa. Following evolutionary scenario testing, we determined the number of host-switching and cospeciation events. Cross-species transmissions have occurred much more frequently than previously estimated, and most of the transmissions were attributable to bats and primates. We conclude that the evolution of the Gammaherpesvirinae subfamily has been driven by both cross-species transmissions and subsequent cospeciation within specific viral lineages and that the bat and primate orders may have potentially acted as superspreaders to other mammalian taxa throughout evolutionary history.

The Desmodus rotundus endogenous betaretrovirus (DrERV) is fixed in the vampire bat D. rotundus population and in other phyllostomid bats but is not present in all species from this family. DrERV is not phylogenetically related to Old World bat betaretroviruses but to betaretroviruses from rodents and New World primates, suggesting recent cross-species transmission. A recent integration age estimation of the provirus in some taxa indicates that an exogenous counterpart might have been in recent circulation. The common vampire bat (Desmodus rotundus) is a phyllostomid bat species with a broad geographical distribution and lives in close proximity with humans and domestic animals (1). Recently described retroviruses in chiropterans are diverse, some potentially representing the oldest viral lineages in mammalian taxa (2-5). However, retroviral characterization has been restricted to bat species distributed in Eurasia, Africa, and Australia (2, 4, 5). Little is known about retroviruses in bats from the neotropics, and nothing is known about those in vampire bats. Endogenous retroviruses (ERVs) are present in the genomes of all vertebrates examined (2-13). As different species may share ERV sequences, it is assumed that, in many cases, an exogenous retrovirus infected the common ancestor of multiple species and became fixed in the genome prior to species divergence (14-16). Most ERVs are inactive "genetic fossils," whereas some may still retain the ability to transcribe active elements or can become reactivated, having potential health implications for the host (7,(17)(18)(19)(20). As retroviruses are transmitted primarily via blood-toblood contact, we postulate that vampire bat retroviruses are particularly prone to jumping from one species to another. In this study, we characterized an endogenous betaretrovirus present in D. rotundus and searched for evidence indicating cross-species transmission events within its evolutionary history.DrERV is a type D endogenous betaretrovirus. Genomic Illumina MiSeq shotgun sequencing from a population of free-ranging and captive D. rotundus bats from Mexico and the Berlin Zoological Garden (see Table S1 in the supplemental material) revealed the presence of a novel retrovirus, designated here Desmodus rotundus endogenous retrovirus (DrERV). Read assignment analysis showed that DrERV is homologous to squirrel monkey retrovirus (SMRV), a type D retrovirus found in New World squirrel monkeys (Saimiri genus) (21); they share a global percentage nucleotide similarity of 72% (E value, 0.0) as determined by BLAST analysis. To retrieve the complete DrERV genome and integration sites, reads were assembled against the SMRV genome through a combined mapping and de novo assembly approach using Bowtie version 2 0.2.2, Burrows-Wheeler Aligner (BWA) version 0.7.9, and Velvet 1.2.10 against the SMRV genome to build a consensus sequence (SMRV-H; GenBank accession number M23385) (22-24), and sequence gaps were covered by PCR (see Table S2 in the supplemental material). The full DrERV genome was ...

Since 1970, aquaculture production has grown. In 2010, it had an annual average rate of 6.3% with 59.9 million tons of product and soon could exceed capture fisheries as a source of fishery products. However, the occurrence of viral diseases continues to be a significant limiting factor and its control is important for the development of this sector. In aquaculture farms, fish are reared under intensive culture conditions, and the use of viral vaccines has enabled an increase in production. Several types of vaccines and strategies of vaccination have been developed; however, this approach has not reached the expected goals in the most susceptible stage (fingerlings). Currently, there are inactivated and recombinant commercial vaccines, mainly for salmonids and cyprinids. In addition, updated genomic and proteomic technology has expedited the research and expansion of new vaccine models, such as those comprised of subunits or DNA. The objective of this review is to cover the various types of viral vaccines that have been developed and are available for bony fishes, as well as the advantages and challenges that DNA vaccines present for massive administration in a growing aquaculture, possible risks for the environment, the controversy regarding genetically modified organisms and possible acceptance by consumers.

Infectious pancreatic necrosis virus (IPNV) is one of the most important viruses in the Pacific salmon Oncorhynchus spp., Atlantic Salmon Salmo salar, and Rainbow Trout O. mykiss industry. This virus has been shown to produce high mortality among salmonid fry and juveniles, and survivors might become carriers. Since 2000, IPNV has affected Mexican Rainbow Trout culture, resulting in considerable economic losses. In the current study, molecular characterization of the VP2 gene of a number of Mexican IPNV isolates was done and the virus's phylogenetic relationships to IPNV reference strains were investigated. The phylogenetic analysis indicated that Mexican IPNV isolates are closely related to strains from the United States and Canada and that all Mexican IPNV isolates belong to genogroup 1. Furthermore, low genetic diversity was found between the Mexican isolates (identity, 95.8-99.8% nucleotides and 95.8-99.6% amino acids). The result of the analysis of the amino acid residues found at positions 217, 221, and 247 (alanine, threonine, and glutamic acid, respectively) could be associated with virulence, although the expression of virulence factors is more complex and may be influenced by the agent and host factors. The high percentage of identity among the VP2 genes from geographically distant IPNV isolates and the evidence of wide distribution in the country might have been facilitated by carrier trout. This hypothesis is supported by the identification of the amino acid threonine at position 221 in all Mexican isolates, a factor related to the carrier state for IPNV, as reported by other studies.

Transgenic plants have been employed successfully as a low-cost system for the production of therapeutically valuable proteins including antibodies, antigens and hormones. Here, we report expression of a full-length nucleoprotein gene of rabies virus in transgenic tomato plants. The nucleoprotein was also transiently expressed in Nicotiana benthamiana plants by agroinfiltration. In both cases, the nucleoprotein was expressed at high levels, 1-5% of total soluble protein in tomato and 45% in N. benthamiana. Previously, only epitopes of the nucleoprotein had been expressed in plants. The presence and expression of the transgene was verified by PCR, Southern, northern and western blots. Mice were immunized both intraperitoneally (i.p.) and orally with tomato protein extracts containing the N protein induced the production of antibodies. The antibody titer of mice immunized i.p., was at least four times higher than that of mice immunized orally. These results were reflected in the challenge experiments where i.p.-immunized mice were partially protected against a peripheral virus challenge whereas orally immunized mice were not. This protection was comparable to that obtained in previous experiments employing different expression systems. Work is in progress to express both G and N proteins in transgenic plants and evaluate protection in mice.