Role of Defective Proviruses in HIV Persistence (R01 Clinical Trial Not Allowed) | PAR 25 330

Opportunity Information: Apply for PAR 25 330

The NIH funding opportunity PAR-25-330, titled "Role of Defective Proviruses in HIV Persistence (R01 Clinical Trial Not Allowed)," supports basic and translational research focused on a specific and increasingly important problem in HIV cure science: the large pool of HIV proviruses that are "defective" (genetically damaged or incomplete) yet may still influence long-term HIV persistence, disease processes during antiretroviral therapy (ART), and the performance of HIV measurement tools. While these proviruses are often considered replication-incompetent, they can still produce viral RNA or proteins in some cases, interact with host immune responses, and complicate how scientists interpret molecular signals that look like ongoing infection. This NOFO is aimed at clarifying what defective proviruses actually do in people on suppressive ART and how they may help maintain HIV-related inflammation, immune activation, or other pathogenic effects even when standard clinical viral load tests remain undetectable.

A central theme of the opportunity is to define how defective HIV proviruses contribute to the mechanisms that allow HIV to persist for years despite effective treatment. In cure research, persistence is usually discussed in terms of the latent reservoir of intact, replication-competent proviruses that can reignite infection if ART stops. However, most integrated HIV DNA in treated individuals is defective, and this NOFO highlights the possibility that this majority population is not simply "biological noise." Proposed research under this announcement could explore how defective proviruses are generated and maintained over time, how they are distributed across tissues and cell subsets, whether they expand through clonal proliferation of infected cells, and which cellular environments favor their transcription or translation. Projects may also investigate downstream consequences such as immune recognition of defective-provirus-derived antigens, chronic immune stimulation, or selective pressures shaping the reservoir during long-term ART.

Another major emphasis is the impact of defective proviruses on HIV pathogenesis during ART, meaning the ways HIV continues to affect health even when therapy is working. Persistent inflammation and immune dysfunction remain common in treated HIV infection and are linked to comorbidities; one rationale for this NOFO is that defective proviruses might contribute to these processes by intermittently expressing viral RNA or proteins that trigger innate or adaptive immune pathways. Research could focus on the molecular and immunologic pathways activated by defective proviral transcription, how these signals differ from those generated by intact proviruses, and whether particular classes of defects (for example, large deletions, hypermutation, or packaging defects) are more likely to produce biologically active products. The overall goal is to sort out what portion of persistent HIV-related immune activation is driven by defective proviruses versus other sources, and what that means for long-term health and cure strategies.

The NOFO also calls attention to how defective proviruses may interfere with HIV cure strategies. Many cure approaches try to reduce, silence, or eliminate HIV-infected cells, or to force latent virus expression so infected cells can be cleared. If defective proviruses generate transcripts or proteins that mimic the signals of reactivated intact virus, they could create false positives or misleading readouts in cure trials and preclinical studies. They might also divert immune responses toward non-productive targets, potentially reducing the effectiveness of therapeutic vaccines, immune-based clearance strategies, or latency reversal approaches. In addition, if interventions change the relative abundance or expression patterns of defective proviruses, that could complicate interpretation of whether a strategy truly reduced the replication-competent reservoir. This opportunity is therefore suited to projects that connect detailed virologic characterization with implications for cure-directed interventions, without actually conducting a clinical trial under this particular mechanism.

A practical and highly relevant focus is the interference of defective proviruses with HIV-specific molecular assays. Many commonly used reservoir measurements (for example, total HIV DNA, certain PCR-based RNA measures, or assays that do not distinguish intact from defective genomes) can be heavily influenced by defective sequences, potentially overstating reservoir size or mischaracterizing treatment effects. This NOFO supports research that clarifies how and why specific assays are confounded, and that may lead to improved measurement strategies, better interpretation frameworks, or new assay designs that more accurately quantify biologically meaningful endpoints. Work might include comparing assay outputs with sequencing-based proviral characterization, mapping which defects drive false signals, or developing methods to separate transcriptionally active defective proviruses from intact latent genomes. The underlying message is that understanding defective proviruses is not only a biological question but also an urgent measurement and evaluation problem for the entire cure field.

Mechanistically, the award uses the R01 grant mechanism and explicitly states "Clinical Trial Not Allowed," meaning applicants should propose studies that are not clinical trials as defined by NIH policy. Human samples, observational analyses, and laboratory studies using specimens from cohorts or repositories may be appropriate, but interventional studies assigning participants to prospective interventions with health-related outcomes would not fit under this announcement. The NOFO is categorized as a discretionary grant opportunity and spans NIH program areas associated with CFDA numbers 93.242, 93.847, 93.855, and 93.865, reflecting the broader NIH infrastructure supporting HIV and related biomedical research.

In terms of who can apply, eligibility is broad and includes many types of domestic U.S. entities such as state, county, and local governments; public and state-controlled and private institutions of higher education; independent school districts; special district governments; and public housing authorities/Indian housing authorities. It also includes federally recognized tribal governments and tribal organizations, nonprofits with or without 501(c)(3) status, for-profit organizations (other than small businesses), and small businesses. Beyond these standard categories, the NOFO explicitly highlights additional eligible applicants such as Alaska Native and Native Hawaiian Serving Institutions, Asian American Native American Pacific Islander Serving Institutions (AANAPISIs), Hispanic-serving Institutions, Historically Black Colleges and Universities (HBCUs), Tribally Controlled Colleges and Universities (TCCUs), faith-based or community-based organizations, eligible federal agencies, U.S. territories or possessions, regional organizations, and non-domestic (non-U.S.) entities (foreign organizations). This breadth suggests NIH is open to a wide range of institutional capacities and encourages participation from diverse and geographically varied organizations, including those serving historically underrepresented communities.

Key administrative details provided include the funding opportunity number PAR-25-330, the NIH as the sponsoring agency, and an original closing date of January 7, 2028. The listed award ceiling is $500,000, indicating an upper limit NIH expects for direct costs or total costs depending on the specific policy context of the announcement (applicants typically confirm the exact interpretation in the full NOFO and related NIH budget guidance). The opportunity was created on December 9, 2024. Overall, the program is designed to push the field past a simplistic intact-versus-defective framing by funding research that explains how defective proviruses shape persistence biology, ongoing pathogenesis under ART, the real-world performance of cure strategies, and the accuracy of the molecular tools used to measure progress toward an HIV cure.

• The National Institutes of Health in the food and nutrition, health, income security and social services sector is offering a public funding opportunity titled "Role of Defective Proviruses in HIV Persistence (R01 Clinical Trial Not Allowed)" and is now available to receive applicants.
• Interested and eligible applicants and submit their applications by referencing the CFDA number(s): 93.242, 93.847, 93.855, 93.865.
• This funding opportunity was created on 2024-12-09.
• Applicants must submit their applications by 2028-01-07.
• Each selected applicant is eligible to receive up to $500,000.00 in funding.
• Eligible applicants include: State governments, County governments, City or township governments, Special district governments, Independent school districts, Public and State controlled institutions of higher education, Native American tribal governments (Federally recognized), Public housing authorities/Indian housing authorities, Native American tribal organizations (other than Federally recognized tribal governments), Nonprofits having a 501 (c) (3) status with the IRS, other than institutions of higher education, Nonprofits that do not have a 501 (c) (3) status with the IRS, other than institutions of higher education, Private institutions of higher education, For-profit organizations other than small businesses, Small businesses, Others.

Apply for PAR 25 330

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