Detection of Circulating SARS-CoV-2 Variants of Concern (VOCs) Using a Multiallelic Spectral Genotyping Assay.

Throughout the coronavirus disease 2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has continuously evolved, resulting in new variants, some of which possess increased infectivity, immune evasion, and virulence. Such variants have been denoted by the World Health Organization as variants of concern (VOC) because they have resulted in an increased number of cases, posing a strong risk to public health. Thus far, five VOCs have been designated, Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529), including their sublineages. Next-generation sequencing (NGS) can produce a significant amount of information facilitating the study of variants; however, NGS is time-consuming and costly and not efficient during outbreaks, when rapid identification of VOCs is urgently needed. In such periods, there is a need for fast and accurate methods, such as real-time reverse transcription PCR in combination with probes, which can be used for monitoring and screening of the population for these variants. Thus, we developed a molecular beacon-based real-time RT-PCR assay according to the principles of spectral genotyping. This assay employs five molecular beacons that target ORF1a:ΔS3675/G3676/F3677, S:ΔH69/V70, S:ΔE156/F157, S:ΔΝ211, S:ins214EPE, and S:ΔL242/A243/L244, deletions and an insertion found in SARS-CoV-2 VOCs. This assay targets deletions/insertions because they inherently provide higher discrimination capacity. Here, the design process of the molecular beacon-based real-time RT-PCR assay for detection and discrimination of SARS-CoV-2 is presented, and experimental testing using SARS-CoV-2 VOC samples from reference strains (cultured virus) and clinical patient samples (nasopharyngeal samples), which have been previously classified using NGS, were evaluated. Based on the results, it was shown that all molecular beacons can be used under the same real-time RT-PCR conditions, consequently improving the time and cost efficiency of the assay. Furthermore, this assay was able to confirm the genotype of each of the tested samples from various VOCs, thereby constituting an accurate and reliable method for VOC detection and discrimination. Overall, this assay is a valuable tool that can be used for screening and monitoring the population for VOCs or other emerging variants, contributing to limiting their spread and protecting public health.

Comprehensive Genetic Characterization of Four Novel HIV-1 Circulating Recombinant Forms (CRF129_56G, CRF130_A1B, CRF131_A1B, and CRF138_cpx): Insights from Molecular Epidemiology in Cyprus.

Molecular investigations of the HIV-1 pol region (2253-5250 in the HXB2 genome) were conducted on sequences obtained from 331 individuals infected with HIV-1 in Cyprus between 2017 and 2021. This study unveiled four distinct HIV-1 putative transmission clusters, encompassing 19 previously unidentified HIV-1 recombinants. These recombinants, each comprising eight, three, four, and four sequences, respectively, did not align with previously established Circulating Recombinant Forms (CRFs). To characterize these novel HIV-1 recombinants, near-full-length genome sequences were successfully obtained for 16 of the 19 recombinants (790-8795 in the HXB2 genome) using an in-house-developed RT-PCR assay. Phylogenetic analyses, employing MEGAX and Cluster-Picker, along with confirmatory neighbor-joining tree analyses of subregions, were conducted to identify distinct clusters and determine subtypes. The uniqueness of the HIV-1 recombinants was evident in their exclusive clustering within generated maximum likelihood trees. Recombination analyses highlighted the distinct chimeric nature of these recombinants, with consistent mosaic patterns observed across all sequences within each of the four putative transmission clusters. Conclusive genetic characterization identified four novel HIV-1 CRFs: CRF129_56G, CRF130_A1B, CRF131_A1B, and CRF138_cpx. CRF129_56G exhibited two recombination breakpoints and three fragments of subtypes CRF56_cpx and G. Both CRF130_A1B and CRF131_A1B featured seven recombination breakpoints and eight fragments of subtypes A1 and B. CRF138_cpx displayed five recombination breakpoints and six fragments of subtypes CRF22_01A1 and F2, along with an unclassified fragment. Additional BLAST analyses identified a Unique Recombinant Form (URF) of CRF138_cpx with three additional recombination sites, involving subtype F2, a fragment of unknown subtype origin, and CRF138_cpx. Post-identification, all putative transmission clusters remained active, with CRF130_A1B, CRF131_A1B, and CRF138_cpx clusters exhibiting further growth. Furthermore, international connections were identified through BLAST analyses, linking one sequence from the USA to the CRF130_A1B strain, and three sequences from Belgium and Cameroon to the CRF138_cpx strain. This study contributes valuable insights into the dynamic landscape of HIV-1 diversity and transmission patterns, emphasizing the need for ongoing molecular surveillance and global collaboration in tracking emerging viral variants.

Comparative HIV-1 Phylogenies Characterized by PR/RT, Pol and Near-Full-Length Genome Sequences.

In an effort to evaluate the accuracy of HIV-1 phylogenies based on genomes of increasing length, we developed a comprehensive near-full-length HIV-1 genome RT-PCR assay and performed a comparative evaluation via phylogenetic analyses. To this end, we conducted comparative analyses of HIV-1 phylogenies derived based on HIV-1 PR/RT (2253-3359 in the HXB2 genome) and pol region (2253-5250 in the HXB2 genome) sequences isolated from 134 HIV-1-infected patients in Cyprus (2017-2019). The HIV-1 genotypic subtypes determined using six subtyping tools (REGA 3.0, COMET 2.3, jpHMM, SCUEAL, Stanford, and Geno2pheno) were compared to investigate the discrepancies generated among different tools. To evaluate the accuracy of defined HIV-1 phylogenies, the samples exhibiting at least one discrepant subtyping result among different subtyping tools in both PR/RT and pol regions or only in the pol region (n = 38) were selected for near-full-length HIV-1 genome (790-8795 in HXB2 genome) sequencing using a newly developed RT-PCR/sequencing assay. The obtained sequences were employed for HIV-1 genotypic subtype determination and subjected to comparative phylogenetic-based analyses. It was observed that 39.6% of the 134 samples presented discrepancies in the PR/RT region, while 28.4% presented discrepancies in the pol region. REGA 3.0 produced the fewest discrepancies collectively in both regions and was selected for subsequent subtyping and comparative phylogenetic analyses of near-full-length HIV-1 genome sequences. The analyses of near-full-length HIV-1 genome sequences identified 68.4% of the 38 'discrepant samples' (n = 26) as belonging to uncharacterized recombinant HIV-1 strains, while 21.1% were circulating recombinant forms (CRFs) (n = 8) and 10.5% belonged to pure group M subtypes (n = 4). The findings demonstrated a significant reduction of 11.2% in discrepancies when pol region sequences were used compared to PR/RT region sequences, indicating that increased nucleotide sequence lengths are directly correlated with more consistent subtype classification. The results also revealed that if the discrepancy in pol region subtyping results persists, then there is a high likelihood (89.5%) that the query sequence is a recombinant HIV-1 strain, 68.4% of which belong to uncharacterized recombinant HIV-1 strains. The results of this study showed that REGA 3.0 presented the best performance in subtyping recombinant HIV-1 strains, while Stanford performed better in defining phylogenies of pure group M subtypes. The study highlights that, especially in populations with polyphyletic HIV-1 epidemics resulting in a high prevalence of recombinant HIV-1 strains, neither PR/RT nor pol region sequences are reliable for the determination of HIV-1 genotypic subtypes in samples showing discrepancies among different subtyping tools, and only near-full-length or full-length HIV-1 genome sequences are sufficiently accurate.

Characterization of a novel HIV-1 circulating recombinant form, CRF91_cpx, comprising CRF02_AG, G, J, and U, mostly among men who have sex with men.

Prospective molecular studies of HIV-1 pol region (2253-5250 in HXB2 genome) sequences from sequenced samples of 269 HIV-1-infected patients in Cyprus (2017-2021) revealed a transmission cluster of 14 unknown HIV-1 recombinants that were not classified as previously established CRFs. The earliest recombinant was collected in September 2017, and the transmission cluster continued to grow until November 2020. Near full-length HIV-1 genome sequences of the 11 of the 14 recombinants were successfully obtained (790-8795 in HXB2 genome) and aligned against a reference dataset of HIV-1 subtypes and CRFs. We employed MEGAX for maximum-likelihood tree construction (GTR model, 1000 bootstrap replicates), Cluster-Picker for phylogenetic clustering analysis (genetic distance ≤0.045, bootstrap support value ≥70%), and REGA-3.0 for subtype determination. Bootscan and similarity plot analyses (sliding window of 400 nucleotides overlapped by 40 nucleotides) were conducted using SimPlot-v3.5.1, and subregion confirmatory neighbour-joining tree analyses were conducted using MEGAX (Kimura two-parameter model, 1000 bootstrap replicates, ≥70% bootstrap-support value). Exclusive clustering of the HIV-1 recombinants revealed their uniqueness. The recombination analyses illustrated the same unique mosaic pattern with six putative intersubtype recombination breakpoints, seven fragments of subtypes CRF02_AG, G, J and an unclassified fragment. We conclusively characterized the mosaic structure of the novel HIV-1 CRF, named CRF91_cpx, by the Los Alamos HIV Sequence Database. Additionally, we identified a URF of CRF91_cpx with two additional recombination sites, generated by a recombination event between subtype B and CRF91_cpx. Since the identification of CRF91_cpx, two additional patient samples have been entered into the CRF91_cpx transmission cluster, demonstrating active growth.