The human immunoglobulin repertoire is vast, producing billions of unique antibodies from a limited number of germline immunoglobulin genes. The immunoglobulin heavy chain variable region (IGHV) is central to antigen binding and is comprised of 48 functional genes. Here we analyzed whether HIV-1 infected individuals who develop broadly neutralizing antibodies show a distinctive germline IGHV profile. Using both 454 and Illumina technologies we sequenced the IGHV repertoire of 28 HIV-infected South African women from the Center for the AIDS Programme of Research in South African (CAPRISA) 002 and 004 cohorts, 13 of whom developed broadly neutralizing antibodies. Of the 259 IGHV alleles identified in this study, approximately half were not found in the International Immunogenetics Database (IMGT). This included 85 entirely novel alleles and 38 alleles that matched rearranged sequences in non-IMGT databases. Analysis of the rearranged H chain V region genes of monoclonal antibodies isolated from 7 of the CAPRISA women and previously isolated broadly neutralizing antibodies from other donors provided evidence that at least 8 novel or non-IMGT alleles contributed to functional antibodies. Importantly, we found that despite a wide range in the number of IGHV alleles in each individual, including alleles used by known broadly neutralizing antibodies, there were no significant differences in germline IGHV repertoires between individuals who do and do not develop broadly neutralizing antibodies. This study reports novel IGHV repertoires and highlights the importance of a fully comprehensive immunoglobulin database for germline gene usage prediction. Furthermore, these data suggest a lack of genetic bias in broadly neutralizing antibody development in HIV-1 infection, with implications for HIV vaccine design.

In adults starting antiretroviral therapy (ART) during acute infection, 2% of proviruses that persist on ART are genetically intact by sequence analysis. In contrast, a recent report in children treated early failed to detect sequence-intact proviruses. In another cohort of children treated early, we sought to detect and characterize proviral sequences after 6 to 9 years on suppressive ART. Peripheral blood mononuclear cells (PBMC) from perinatally infected children from the Children with HIV Early antiRetroviral (CHER) study were analyzed. Nearly full-length proviral amplification and sequencing (NFL-PAS) were performed at one time point after 6 to 9 years on ART. Amplicons with large internal deletions were excluded (<9 kb). All amplicons of ≥9 kb were sequenced and analyzed through a bioinformatic pipeline to detect indels, frameshifts, or hypermutations that would render them defective. In eight children who started ART at a median age of 5.4 months (range, 2.0 to 11.1 months), 733 single NFL-PAS amplicons were generated. Of these, 534 (72.9%) had large internal deletions, 174 (23.7%) had hypermutations, 15 (1.4%) had small internal deletions, 3 (1.0%) had deletions in the packaging signal/major splice donor site, and 7 (1.0%) were sequence intact. These 7 intact sequences were from three children who initiated ART after 2.3 months of age, one of whom had two identical intact sequences, suggestive of a cell clone harboring a replication-competent provirus. No intact proviruses were detected in four children who initiated ART before 2.3 months of age. Rare, intact proviruses can be detected in children who initiate ART after 2.3 months of age and are probably, as in adults, maintained by clonal expansion of cells infected before ART initiation. IMPORTANCE There are limited data about the proviral landscape in children exhibiting long-term suppression after early treatment, particularly in Sub-Saharan Africa where HIV-1 subtype C predominates. Investigating the sequence-intact reservoir could provide insight on the mechanisms by which intact proviruses persist and inform ongoing cure efforts. Through nearly full-length proviral amplification and sequencing (NFL-PAS), we generated 733 NFL-PAS amplicons from eight children. We showed that rare, genetically intact proviruses could be detected in children who initiated ART after 2.3 months of age. The frequency of intact proviruses was lower (P < 0.05) than that reported for HIV subtype B-infected adults treated during early HIV infection. We show that cells harboring genetically intact HIV proviruses are rare in children exhibiting long-term suppression after early treatment and may require the processing of a large number of cells to assess reservoir size. This points to the need for efficient methods to accurately quantify latent reservoirs, particularly in pediatric studies where sample availability is limited.

HIV-1 proviral single-genome sequencing by limiting-dilution polymerase chain reaction (PCR) amplification is important for differentiating the sequence-intact from defective proviruses that persist during antiretroviral therapy (ART). Intact proviruses may rebound if ART is interrupted and are the barrier to an HIV cure. Oxford Nanopore Technologies (ONT) sequencing offers a promising, cost-effective approach to the sequencing of long amplicons such as near full-length HIV-1 proviruses, but the high diversity of HIV-1 and the ONT sequencing error render analysis of the generated data difficult. NanoHIV is a new tool that uses an iterative consensus generation approach to construct accurate, near full-length HIV-1 proviral single-genome sequences from ONT data. To validate the approach, single-genome sequences generated using NanoHIV consensus building were compared to Illumina® consensus building of the same nine single-genome near full-length amplicons and an average agreement of 99.4% was found between the two sequencing approaches.

The challenge presented by high-throughput sequencing necessitates the development of novel tools for accurate alignment of reads to reference sequences. Current approaches focus on using heuristics to map reads quickly to large genomes, rather than generating highly accurate alignments in coding regions. Such approaches are, thus, unsuited for applications such as amplicon-based analysis and the realignment phase of exome sequencing and RNA-seq, where accurate and biologically relevant alignment of coding regions is critical. To facilitate such analyses, we have developed a novel tool, RAMICS, that is tailored to mapping large numbers of sequence reads to short lengths (<10 000 bp) of coding DNA. RAMICS utilizes profile hidden Markov models to discover the open reading frame of each sequence and aligns to the reference sequence in a biologically relevant manner, distinguishing between genuine codon-sized indels and frameshift mutations. This approach facilitates the generation of highly accurate alignments, accounting for the error biases of the sequencing machine used to generate reads, particularly at homopolymer regions. Performance improvements are gained through the use of graphics processing units, which increase the speed of mapping through parallelization. RAMICS substantially outperforms all other mapping approaches tested in terms of alignment quality while maintaining highly competitive speed performance.

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The characterisation of the HIV-1 reservoir, which consists of replication-competent integrated proviruses that persist on antiretroviral therapy (ART), is made difficult by the rarity of intact proviruses relative to those that are defective. While the only conclusive test for the replication-competence of HIV-1 proviruses is carried out in cell culture, genetic characterization of genomes by near full-length (NFL) PCR and sequencing can be used to determine whether particular proviruses have insertions, deletions, or substitutions that render them defective. Proviruses that are not excluded by having such defects can be classified as genetically intact and, possibly, replication competent. Identifying and quantifying proviruses that are potentially replication-competent is important for the development of strategies towards a functional cure. However, to date, there are no programs that can be incorporated into deep-sequencing pipelines for the automated characterization and annotation of HIV genomes. Existing programs that perform this work require manual intervention, cannot be widely installed, and do not have easily adjustable settings. Here, we present HIVIntact, a python-based software tool that characterises genomic defects in NFL HIV-1 sequences, allowing putative intact genomes to be identified in-silico. Unlike other applications that assess the genetic intactness of HIV genomes, this tool can be incorporated into existing sequence-analysis pipelines and applied to large next-generation sequencing datasets.