Bayesian Coalescent Analysis Research Articles

Mitochondrial genome analysis across different populations reveals the intraspecific variation and phylogeography of the Caucasian soft tick relapsing fever vector, Ornithodoros (Pavlovskyella) verrucosus (Ixodida: Argasidae)

Territories in southern parts of Eastern Europe and in the Caucasus are endemic for tick-borne relapsing fever (TBRF), caused by Borrelia caucasica. This spirochete is transmitted exclusively by the bites of Ornithodoros verrucosus; however, the distribution and genetic diversity of the tick vector have not been explored. To address this, we performed a phylogeographic study of O. verrucosus specimens collected across a large geographic distribution. We sequenced and analyzed complete mitochondrial genomes of 54 individual O. verrucosus ticks representing 23 geographically diverse populations from Ukraine, Georgia, and Azerbaijan. We detected 47 unique haplotypes, with every collection site exhibiting distinct polymorphisms. This, along with other population genetic indices, suggests little evidence of gene flow between populations. The Bayesian coalescent analysis revealed the presence of four lineages that diverged in the Middle Pleistocene (770–126 kya). Two lineages were widespread and present in all study regions, while the other two were restricted to the southern foothills of the Lesser Caucasus mountain range. The sympatry of these ancient lineages suggests that isolation by environment, in addition to geographic distance, may play a role in the intraspecific divergence of tick populations. Using a phylogeographic approach, we provide a snapshot of genetic diversity in O. verrucosus and discuss the evolutionary history of the tick vector.

Pepino mosaic virus: Recombination, spatiotemporal divergence and codon usage

AbstractPepino mosaic virus (PepMV, species Potexvirus pepini) is a potexvirus of economic significance. The pathogen has become a serious threat to tomato (Solanum lycopersicum) worldwide. To gain more insights into the molecular epidemiology and evolution of PepMV, recombination analysis was carried out. Nine chimeric sequences were identified, including one probably involving host‐to‐virus gene flow. Based on the coat protein (CP) gene, PepMV isolates were classified into six genotypes and the phylogeography was reconstructed. Bayesian coalescent analysis applied to the dated genomic sequences suggested that PepMV started to expand in the early 17th century and evolved at a moderate rate. Ancestral state reconstruction supported the South American origin of PepMV. Codon usage bias analysis showed that PepMV genes had influences in addition to compositional constraints. In codon usage, PepMV is fairly similar to S. lycopersicum. Moreover, PepMV recapitulates the host's remarkable suppression of CpG and UpA dinucleotides.

Risk Factors Associated with Hepatitis C Subtypes and the Evolutionary History of Subtype 1a in Mexico.

The Hepatitis C Virus (HCV), with its diverse genotypes and subtypes, has significantly impacted the health of millions of people worldwide. Analyzing the risk factors is essential to understanding the spread of the disease and developing appropriate prevention strategies. This study aimed to identify risk factors associated with HCV subtype transmission and calculate the emergence time of subtype 1a in Mexico. A cross-sectional study was conducted from January 2014 to December 2018, involving 260 HCV-infected adults. HCV infection was confirmed via Enzyme-Linked Immunosorbent Assay, and viral load was measured by real-time PCR. Genotyping/subtyping tools were the Line Probe Assay and Sanger sequencing of the non-structural region 5B (NS5B). The most frequent HCV subtype was 1a (58.5%), followed by subtypes 1b (19.2%), 3a (13.1%), 2b (5.4%), 2a/2c (2.7%), 2a (0.8%), and 4a (0.4%). Intravenous drug use and tattoos were significant risk factors for subtypes 1a and 3a, while hemodialysis and blood transfusion were linked with subtype 1b. For the evolutionary analysis, 73 high-quality DNA sequences of the HCV subtype 1a NS5B region were used, employing a Bayesian coalescent analysis approach. This analysis suggested that subtype 1a was introduced to Mexico in 1976, followed by a diversification event in the mid-1980s. An exponential increase in cases was observed from 1998 to 2006, stabilizing by 2014. In conclusion, this study found that HCV subtypes follow distinct transmission routes, emphasizing the need for targeted prevention strategies. Additionally, the findings provide valuable insights into the origin of HCV subtype 1a. By analyzing the history, risk factors, and dynamics of the HCV epidemic, we have identified these measures: limiting the harm of intravenous drug trafficking, enhancing medical training and infrastructure, and ensuring universal access to antiviral treatments. The successful implementation of these strategies could lead to an HCV-free future in Mexico.

The effect of missing data on evolutionary analysis of sequence capture bycatch, with application to an agricultural pest

Sequence capture is a genomic technique that selectively enriches target sequences before high throughput next-generation sequencing, to generate specific sequences of interest. Off-target or ‘bycatch’ data are often discarded from capture experiments, but can be leveraged to address evolutionary questions under some circumstances. Here, we investigated the effects of missing data on a variety of evolutionary analyses using bycatch from an exon capture experiment on the global pest moth, Helicoverpa armigera. We added > 200 new samples from across Australia in the form of mitogenomes obtained as bycatch from targeted sequence capture, and combined these into an additional larger dataset to total > 1000 mitochondrial cytochrome c oxidase subunit I (COI) sequences across the species’ global distribution. Using discriminant analysis of principal components and Bayesian coalescent analyses, we showed that mitogenomes assembled from bycatch with up to 75% missing data were able to return evolutionary inferences consistent with higher coverage datasets and the broader literature surrounding H. armigera. For example, low-coverage sequences broadly supported the delineation of two H. armigera subspecies and also provided new insights into the potential for geographic turnover among these subspecies. However, we also identified key effects of dataset coverage and composition on our results. Thus, low-coverage bycatch data can offer valuable information for population genetic and phylodynamic analyses, but caution is required to ensure the reduced information does not introduce confounding factors, such as sampling biases, that drive inference. We encourage more researchers to consider maximizing the potential of the targeted sequence approach by examining evolutionary questions with their off-target bycatch where possible—especially in cases where no previous mitochondrial data exists—but recommend stratifying data at different genome coverage thresholds to separate sampling effects from genuine genomic signals, and to understand their implications for evolutionary research.

Evolution of rat hepatitis E virus: recombination, divergence and codon usage bias

Rat hepatitis E virus (RHEV/HEV-C1, species Rocahepevirus ratti) is an emerging zoonotic pathogen, posing an increasing threat to public health worldwide. This study was conducted for better understanding the epidemiology and evolution of RHEV. The isolates sampled so far can be divided into two major genotypes designated a and b. According to the phylogeography, while type a has been detected in four continents, type b is restricted to East and Southeast Asia. Recombination analysis identified three chimeric isolates. Bayesian coalescent analysis suggested that RHEV began to expand around 1956 and was evolving at a high rate. Codon usage bias analysis revealed that RHEV genes are rich in G/C and have additional bias independent of compositional constraints. In codon usage, RHEV is both similar to and different from the major host Norway rat (Rattus norvegicus). Furthermore, unlike many other mammalian RNA viruses, RHEV does not mirror hosts’ marked suppression of “CG” and “TA”.

Insights into the molecular evolution of enterovirus D68.

Enterovirus D68 (EV-D68) is a respiratory virus that primarily affects children and has been associated with sporadic outbreaks of respiratory illness worldwide. In the present study, temporal spreading and molecular evolution of EV-D68 clades (A1, A2, B, B1, B2, B3, and C) were evaluated. Bayesian coalescent analysis was performed to study viral evolution. Data from 976 whole-genome sequences (WGSs) collected between 1977 and 2022 were evaluated. For A1, the most recent common ancestor was dated to 2005-04-17 in the USA; for A2 it was 2003-12-23 in China; for B, it was 2003-07-06 in China; for B1, it was 2010-03-21 in Vietnam; for B2, it was 2006-11-25 in Vietnam; for B3, it was 2011-01-15 in China; and for C, it was 2000-06-27 in the USA. The molecular origin of EV-D68 was in Canada in 1995, and later it was disseminated in France in 1997, the USA in 1999, Asia in 2008, the Netherlands in 2009, New Zealand in 2010, Mexico in 2014, Kenya in 2015, Sweden in 2016, Switzerland in 2018, Spain in 2018, Belgium in 2018, Australia in 2018, and Denmark in 2019. In 2022, this virus circulated in the USA. In conclusion, EV-D68 originated in Canada in the 1990s and spread to Europe, Asia, Oceania, Latin America, and Africa.

Geographic Transmission and Epidemic History of HIV-1 CRF01_AE, CRF07_BC, and HCV Subtype-6w among Taiwanese Persons Who Inject Drugs.

Persons who inject drugs (PWID) and their risk-related behaviors (e.g., unprotected sex and sharing needles/syringes/other injection equipment) have caused severe public health problems, especially in the rapid spread of HIV-1 and HCV. Here, we reconstructed the epidemic history of HIV-1 circulating recombinant form (CRF) 01_AE, CRF07_BC, and HCV subtype-6w among Taiwanese PWID. The timescales were estimated using phylogenetic and Bayesian coalescent analyses. The results revealed that CRF01_AE started to circulate in the Taiwanese PWID population in central Taiwan at 1992.5 (95% credible region: 1988.8–1995.9) and spread to other regions of Taiwan, while CRF07_BC was first identified in southern Taiwan at 2000.0 (95% CR: 1997.8–2002.2) and then spread northward to central-northern Taiwan. All HCV-6 strains were from Asia (that is, China, Myanmar, Taiwan, and Vietnam) and originated in 1928.1 (95% CR: 1890.2–1966.0). Furthermore, subtype-6w isolates from different regions of Taiwan appeared to share a common source that existed in the mid-1990s (95% CR: 1985.0–2001.8) or thereabouts. The routes of drug trafficking and the resulting high prevalence of HIV-1/HCV co-infections among PWID might have contributed to the virus transmission and promoted its spread worldwide. Long-term monitoring and policy implementation in at-risk populations would be useful for disease control.

Phylogenetic relationships of Xerochrysum, Coronidium and Helichrysum leucopsideum reveal a new genus, Leucozoma (Asteraceae: Gnaphalieae)

AbstractWe gathered morphological data and genome‐wide single nucleotide polymorphisms to infer the evolutionary relationships of Xerochrysum, Coronidium, and Helichrysum leucopsideum, and to test the circumscription of the genera. SVDquartets species tree topology resolved relationships between the genera and within subsets of the Xerochrysum data. Results corroborated previous conclusions that Coronidium is non‐monophyletic as presently circumscribed and forms, in addition to the more distantly related Coronidium scorpioides group, three morphologically distinct clades. SVDquartets returned two clades in Xerochrysum, though species‐level relationships were unclear. Bayesian coalescent analysis using SNAPP produced tree topologies for the three clades of Coronidium with most species‐level relationships well resolved. The new genus Leucozoma is described for seven taxa previously included in Coronidium. A revised description of Coronidium and images of phyllary and fruit diagnostic morphological characters are provided.

Molecular phylogenetic assessment of the canine parvovirus 2 worldwide and analysis of the genetic diversity and temporal spreading in Brazil.

Canine parvovirus type 2 (CPV-2) is a relevant pathogen for dogs and causes a severe disease in carnivore species. CPV-2 reached pandemic proportions after the 1970s with the worldwide dissemination, generating antigenic and genetic variants (CPV-2a, CPV-2b, and CPV-2c) with different pathobiology in comparison with the original type CPV-2. The present study aimed to assess the current global CPV-2molecular phylogeny and to analyze genetic diversity and temporal spreading of variants from Brazil. A total of 284 CPV-2 whole-genome sequences (WGS) and 684 VP2 complete genes (including 23 obtained in the present study) were compared to analyze phylogenetic relationships. Bayesian coalescent analysis estimated the time to the most recent common ancestor (tMRCA) and the population dynamics of the different CPV-2 lineages in the last decades. The WGS phylogenetic tree demonstrated two main clades disseminated worldwide today. The VP2 gene tree showed a total of four well-defined clades distributed in different geographic regions, including one with CPV-2 sequences exclusive from Brazil. These clades do not have a relationship with the previous classification into CPV-2a, CPV-2b, and CPV-2c, despite some having a predominance of one or more antigenic types. Temporal analysis demonstrated that the main CPV-2 clades evolved within a few years (from the 1980s to 1990s) in North America and they spread worldwide afterwards. Population dynamics analysis demonstrated that CPV-2 presented a major dissemination increase at the end of the 1980s / beginning of the 1990s followed by a period of stability and a second minor increase from 2000 to 2004.

Recent molecular evolution of hepatitis B virus genotype F in Latin America.

The evolution of hepatitis B virus genotype F (HBV-F) in Latin America is not completely understood. The aim of this study was to evaluate the molecular evolution of HBV-F in Latin America by comparing 224 whole-genome sequences. Bayesian coalescent analysis was performed to estimate the time to the most recent common ancestor. Four main clades were found, dating from between 1245 and 1730. In addition, four subclades were identified, dating to between 1705 and 1801. The overall effective population size of HBV-F grew in the 18th century and showed an initial expansion outward from Venezuela to other countries from Latin America. Although HBV-F originated thousands of years ago, circulating strains of HBV-F appear to have spread in recent centuries, particularly in the 18th and 19th centuries. The new molecular data provide valuable information for characterizing the evolution of Native American HBV-F in recent centuries.

Genome-Scale Data Reveal Deep Lineage Divergence and a Complex Demographic History in the Texas Horned Lizard (Phrynosoma cornutum) throughout the Southwestern and Central United States.

The southwestern and central United States serve as an ideal region to test alternative hypotheses regarding biotic diversification. Genomic data can now be combined with sophisticated computational models to quantify the impacts of paleoclimate change, geographic features, and habitat heterogeneity on spatial patterns of genetic diversity. In this study, we combine thousands of genotyping-by-sequencing (GBS) loci with mtDNA sequences (ND1) from the Texas horned lizard (Phrynosoma cornutum) to quantify relative support for different catalysts of diversification. Phylogenetic and clustering analyses of the GBS data indicate support for at least three primary populations. The spatial distribution of populations appears concordant with habitat type, with desert populations in AZ and NM showing the largest genetic divergence from the remaining populations. The mtDNA data also support a divergent desert population, but other relationships differ and suggest mtDNA introgression. Genotype–environment association with bioclimatic variables supports divergence along precipitation gradients more than along temperature gradients. Demographic analyses support a complex history, with introgression and gene flow playing an important role during diversification. Bayesian multispecies coalescent analyses with introgression (MSci) analyses also suggest that gene flow occurred between populations. Paleo-species distribution models support two southern refugia that geographically correspond to contemporary lineages. We find that divergence times are underestimated and population sizes are overestimated when introgression occurred and is ignored in coalescent analyses, and furthermore, inference of ancient introgression events and demographic history is sensitive to inclusion of a single recently admixed sample. Our analyses cannot refute the riverine barrier or glacial refugia hypotheses. Results also suggest that populations are continuing to diverge along habitat gradients. Finally, the strong evidence of admixture, gene flow, and mtDNA introgression among populations suggests that P. cornutum should be considered a single widespread species under the General Lineage Species Concept.

Identification of CRF66_BF, a New HIV-1 Circulating Recombinant Form of South American Origin

Circulating recombinant forms (CRFs) are important components of the HIV-1 pandemic. Among 110 reported in the literature, 17 are BF1 intersubtype recombinant, most of which are of South American origin. Among these, all 5 identified in the Southern Cone and neighboring countries, except Brazil, derive from a common recombinant ancestor related to CRF12_BF, which circulates widely in Argentina, as deduced from coincident breakpoints and clustering in phylogenetic trees. In a HIV-1 molecular epidemiological study in Spain, we identified a phylogenetic cluster of 20 samples from 3 separate regions which were of F1 subsubtype, related to the Brazilian strain, in protease-reverse transcriptase (Pr-RT) and of subtype B in integrase. Remarkably, 14 individuals from this cluster (designated BF9) were Paraguayans and only 4 were native Spaniards. HIV-1 transmission was predominantly heterosexual, except for a subcluster of 6 individuals, 5 of which were men who have sex with men. Ten additional database sequences, from Argentina (n = 4), Spain (n = 3), Paraguay (n = 1), Brazil (n = 1), and Italy (n = 1), branched within the BF9 cluster. To determine whether it represents a new CRF, near full-length genome (NFLG) sequences were obtained for 6 viruses from 3 Spanish regions. Bootscan analyses showed a coincident BF1 recombinant structure, with 5 breakpoints, located in p17gag, integrase, gp120, gp41-rev overlap, and nef, which was identical to that of two BF1 recombinant viruses from Paraguay previously sequenced in NFLGs. Interestingly, none of the breakpoints coincided with those of CRF12_BF. In a maximum likelihood phylogenetic tree, all 8 NFLG sequences grouped in a strongly supported clade segregating from previously identified CRFs and from the CRF12_BF “family” clade. These results allow us to identify a new HIV-1 CRF, designated CRF66_BF. Through a Bayesian coalescent analysis, the most recent common ancestor of CRF66_BF was estimated around 1984 in South America, either in Paraguay or Argentina. Among Pr-RT sequences obtained by us from HIV-1-infected Paraguayans living in Spain, 14 (20.9%) of 67 were of CRF66_BF, suggesting that CRF66_BF may be one of the major HIV-1 genetic forms circulating in Paraguay. CRF66_BF is the first reported non-Brazilian South American HIV-1 CRF_BF unrelated to CRF12_BF.

Genome-wide ultraconserved elements resolve phylogenetic relationships and biogeographic history among Neotropical leaf-nosed bats in the genus Anoura (Phyllostomidae)

AnouraGray, 1838 are Neotropical nectarivorous bats and the most speciose genus within the phyllostomid subfamily Glossophaginae. However, Anoura species limits remain debated, and phylogenetic relationships remain poorly known, because previous studies used limited Anoura taxon sampling or focused primarily on higher-level relationships. Here, we conduct the first phylogenomic study of Anoura by analyzing 2039 genome-wide ultraconserved elements (UCEs) sequenced for 42 individuals from 8 Anoura species/lineages plus two outgroups. Overall, our results based on UCEs resolved relationships in the genus and supported (1) the monophyly of small-bodied Anoura species (previously genus Lonchoglossa); (2) monotypic status of A. caudifer; and (3) nested positions of “A. carishina”, A. caudifer aequatoris, and A. geoffroyi peruana specimens within A. latidens, A. caudifer and A. geoffroyi, respectively (suggesting that these taxa are not distinct species). Additionally, (4) phylogenetic networks allowing reticulate edges did not explain gene tree discordance better than the species tree (without introgression), indicating that a coalescent model accounting for discordance solely through incomplete lineage sorting fit our data well. Sensitivity analyses indicated that our species tree results were not adversely affected by varying taxon sampling across loci. Tree calibration and Bayesian coalescent analyses dated the onset of diversification within Anoura to around ∼ 6–9 million years ago in the Miocene, with extant species diverging mainly within the past ∼ 4 million years. We inferred a historical biogeographical scenario for Anoura of parapatric speciation fragmenting the range of a wide-ranging ancestral lineage centered in the Central to Northern Andes, along with Pliocene–Pleistocene dispersal or founder event speciation in Amazonia and the Brazilian Atlantic forest during the last ∼ 2.5 million years.

Regulated Emergence of the African swine fever virus: B646L (p72) Gene Based Bayesian Coalescent Analysis

African swine fever virus (ASFV) belongs to the genus of virus of the Asfaviridae family. ASFV infection causes hemorrhage and high death rate hence increased loss to the swine community. It is a complex infectious disease of swine, which constitutes devastating impacts on animal health and the economy of the pig farmers. It has been confirmed that virus infections has been spreading in swine population for many years. In this study, the evolutionary epidemiology analysis of ASF virus from the geographical regions Africa, Europe, and Asia, respectively were retrieved from GenBank for the analysis. The nucleotide gene sequences of the viral protein p72 encoded by B646L gene published during 1960-2020 was taken in to study. The Bayesian skyline model with uncorrelated randomized clock model was employed to reconstruct the evolutionary history of the virus, to identify virus population demographics. Results of the analysis suggested that ASFV exhibited a high evolutionary rate, as the divergence caused reduction in the population in the recent years. The B646L gene of ASFV had an evolutionary rate of 4.13 X 10-6 substitution/site/year and the tMRCA as 3.15 x 105 with 95 percent HPD range in years (2.4 x 104 to 1.23 x 106) was obtained. In conclusion, the evolutionary study of ASFV with p72 protein from the ASFV of the B646L genes indicated that they evolved at a faster rate and plays a major role in the evolutionary process. Further, this study may help in designing or developing vaccines to control the spread of the disease.

Temporal and geographic spreading of hepatitis B virus genotype A (HBV-A) in Brazil and the Americas.

Hepatitis B virus genotype A (HBV-A) is disseminated in different countries around the world. It presents a high genetic diversity and is classified into seven subgenotypes (A1-A7). HBV-A1 and HBV-A2 are the most frequent and spread in almost all American countries. This study aimed to evaluate the molecular epidemiology of these two subgenotypes, with a special focus on the temporal and geographic spreading in the Americas and Brazil. Bayesian coalescent analyses with HBV-A1 and HBV-A2 whole-genome sequences were performed to study viral phylodynamic and phylogeography. HBV-A1 evolutionary history demonstrated that it was initially disseminated from Africa to other continents probably after the 1400s and mainly in the 17th-18th centuries. The whole viral population grew between the 1700s-1900s and then reached a stationary phase. In Brazil, HBV-A1 common ancestors dated back to the 1600s with successive introductions between the 17th-18th centuries. In contrast, HBV-A2 spread from Europe to other continents after the 1800s, with an increase in the viral population over decades. It was introduced in the 20th century in America and between the 1950s-1970s in Brazil, presenting a high increase in the viral population from the 1970s to the 1980s. The circulation continents for HBV-A1 are Africa and America, while for HBV-A2 are Europe and America. HBV-A is one of the predominant genotypes in America (including Brazil) because of the early introduction by human migration processes of the subgenotypes A1 and A2 between the 16th and 20th centuries and the continuous spreading inside the continent over time.

Cryptic host-driven speciation of mobilid ciliates epibiotic on freshwater planarians

Mobilids are among the most taxonomically diverse but morphologically uniform groups of epibiotic ciliates. They attach to their hosts by means of an adhesive disc as harmless commensals such as Urceolaria, or as parasites causing significant economic loss such as some Trichodina species. We investigated the diversity, species boundaries, and phylogenetic relationships of mobilids associated with freshwater planarians, using 114 new sequences of two mitochondrial (16S rRNA gene and cytochrome c oxidase gene) and five nuclear (18S rRNA gene, ITS1-5.8S-ITS2 region, D1/D2 domains of 28S rRNA gene) markers. Although the morphological disparity of the isolated trichodinids and urceolariids was low, Bayesian coalescent analyses revealed the existence of five distinct evolutionary lineages/species given the seven molecular markers. The occurrence of mobilids perfectly correlated with their planarian hosts: Trichodina steinii and two Urceolaria mitra-like taxa were associated exclusively with the planarian Dugesia gonocephala, Trichodina polycelis sp. n. with the planarian Polycelis felina, and Trichodina schmidtea sp. n. with the planarian Schmidtea polychroa. Host organisms thus very likely constitute sharply isolated niches that might permit speciation of their epibiotic ciliates, even though no distinct morphological features appear to be recognizable among ciliates originating from different hosts.

Phylogeny and time scale of diversification in the fossil-rich sunfishes and black basses (Teleostei: Percomorpha: Centrarchidae)

Species of the North American freshwater fish lineage Centrarchidae are apex predators in their habitats and are among the world’s most popular sport fishes. Centrarchids boast a rich fossil record that extends from the latest Eocene to the Pleistocene. To investigate the phylogeny and timing of diversification of Centrarchidae, we deploy a dataset of DNA sequences of 16 nuclear genes sampled from nearly all of the recognized and undescribed species. We also utilize previously published morphological datasets to assess the phylogenetic placement of one of the oldest known centrarchid fossils, †Plioplarchus whitei. A Bayesian multispecies coalescent species tree analysis provides insight on relationships that evaded resolution in earlier studies, such as the relationships of Acantharchus pomotis, the resolution of a clade consisting of species previously synonymized under the Spotted Bass, Micropterus punctulatus, and a clade of recently described species previously considered populations of the Redeye Bass, Micropterus coosae. This new molecular phylogeny and the inclusion of †P. whitei and other centrarchid fossils in the tip-dated fossilized birth–death analysis results in a new hypothesis of the timing of diversification in Centrarchidae that contextualizes the ages of centrarchid fossils to the timing of speciation among the extant species. In addition to providing new temporal perspectives on the diversification of freshwater fishes in North America, this study may close of the chapter of centrarchid phylogeny inferred using Sanger-sequenced genes, as the use of genomic-scale datasets becomes mainstream in the phylogenetics of fishes.

Evolutionary analysis of rabies virus using the partial Nucleoprotein and Glycoprotein gene in Mumbai region of India.

Nearly 1.7 million cases of dog bites are reported every year in India and many cases of animal rabies are left unattended and undiagnosed. Therefore, a mere diagnosis of rabies is not sufficient to understand the epidemiology and the spread of the rabies virus (RV) in animals. There is a paucity of information about the evolutionary dynamics of RV in dogs and its biodiversity patterns in India. In total, 50 dog-brain samples suspected of rabies were screened by the nucleoprotein- (N) and glycoprotein- (G) gene PCR. The N and G genes were subsequently sequenced to understand the molecular evolution in these genes. The phylogenetic analysis of the N gene revealed that six isolates in the Mumbai region belonged to a single Arctic lineage. Time-scaled phylogeny by Bayesian coalescent analysis of the partial N gene revealed that the time to the most recent common ancestor (TMRCA) for the sequences belonged to the cluster from 2006.68 with a highest posterior density of 95 % betweeen 2005-2008, which is assigned to Indian lineage I. Migration pattern revealed a strong Bayes factor between Mumbai to Delhi, Panji to Hyderabad, Delhi to Chennai, and Chennai to Chandigarh. Phylogenetic analysis of the G gene revealed that the RVs circulating in the Mumbai region are divided into three lineages. Time-scaled phylogeny by the Bayesian coalescent analysis method estimated that the TMRCA for sequences under study was from 1993 and Indian clusters was from 1962. In conclusion, the phylogenetic analysis of the N gene revealed that six isolates belonged to single Arctic lineages along with other Indian isolates and they were clustered into a single lineage but divided into three clades based on the G-gene sequences. The present study highlights and enhances the current molecular epidemiology and evolution of RV and revealed strong location bias and geographical clustering within Indian isolates on the basis of N and G genes.

Genomic evolution, transmission dynamics, and pathogenicity of avian influenza A (H5N8) viruses emerging in China, 2020.

Multiple recent outbreaks of highly pathogenic H5N8 viruses originating in aquatic birds frequently occurred in most European countries, Russia, South Korea, and Japan during the winter of 2020–21, and one zoonotic event of poultry workers infected with novel H5N8 viruses were reported in Russia. Strikingly, these novel H5N8 viruses had emerged and been co-circulating in wild birds and poultry in multiple provinces of China during 2020–21. In China, the population of aquatic birds has risen significantly in the past twenty years, and China is regarded as the largest reservoir for influenza viruses carried in aquatic birds across the globe. Hence, the co-circulation of these novel H5N8 viruses poses an alarming threat to not only poultry industry but also human health. In this study, we sequenced full-length genomes of these H5N8 viruses circulating in China. Phylogenetic analysis demonstrated that poultry-origin H5N8 viruses in China fell within wild birds-origin clade 2.3.4.4b H5N8 viruses from Europe during 2020–21, and notably, were genetically closely related to human-infecting H5N8 viruses in Russia. Moreover, they possessed several molecular markers associated with mammalian adaption. Bayesian coalescent analysis showed that these H5N8 viruses might have introduced into China during June–September 2020, suggesting that these H5N8 viruses might have introduced via wild bird migration or poultry trade. Besides, we also found that the effective population size of clade 2.3.4.4b H5N8 viruses dramatically increased during the winter season of 2020/21, as is consistent with previous increase of genetic diversity during the winter seasons of 2013/14 and 2016/17, which indicated that the wild bird migration accelerates the genetic diversity of these H5N8 viruses during the winter season of 2020/21. Notably, these novel H5N8 viruses were lethal to chickens and mice, highly transmissible to ducks, and were antigenically distinct from 2.3.4.4h H5 viruses circulating in China, posing considerable threats to public health. Our findings offer novel insights into the evolution and risk assessment of H5N8 viruses during the winter season of 2020–21.

Phylodynamic Analysis and Implication of HCV Genotype 4 Variability on Antiviral Drug Response and T-Cell Recognition.

Therapies for HCV care could change the prevalence and the geographic distribution of genotypes due to differences in Sustained Virologic Response (SVR). In this scenario, uncommon genotypes/subtypes, such as genotype 4, could spread from high-risk groups, replacing genotypes eradicated by antiviral drugs. Genotype eradication is also strongly influenced by the CD8+ T cell response. In this study, the genetic variability in HCV genotype 4 strains obtained from a cohort of 67 patients naïve to DAA therapy was evaluated. We found that the presence of resistance-associated substitutions (RAS) was able to affect drug responses. Next, using a prediction tool, viral mutations were identified by their ability, or lack thereof, to reduce the binding affinity with HLA, which affects T cell recognition. The Bayesian coalescent analysis suggested two different circulation clusters, one in risk groups (IDUs and MSM) and the other due to migration flows, dated to 1940 and 1915, respectively. Most of the RAS overlapped with HLA and a lack of binding mutations was observed in 96% of strains. This study describes the introduction of HCV genotype 4 in a region of the Mediterranean basin and evaluates how HCV genotype 4’s genetic variability could affect the response of antiviral drugs and CD8+ T cell recognition.