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Adapting SHIVs In Vivo Selects for Envelope-Mediated Interferon-α Resistance.

ABSTRACT: Lentiviruses are able to establish persistent infection in their respective hosts despite a potent type-I interferon (IFN-I) response following transmission. A number of IFN-I-induced host factors that are able to inhibit lentiviral replication in vitro have been identified, and these studies suggest a role for IFN-induced factors as barriers to cross-species transmission. However, the ability of these factors to inhibit viral replication in vivo has not been well characterized, nor have the viral determinants that contribute to evasion or antagonism of the host IFN-I response. In this study, we hypothesized that the host IFN-I response serves as a strong selective pressure in the context of SIV/HIV chimeric virus (SHIV) infection of macaques and sought to identify the viral determinants that contribute to IFN-I resistance. We assessed the ability of SHIVs encoding HIV-1 sequences adapted by serial passage in macaques versus SHIVs encoding HIV sequences isolated directly from infected individuals to replicate in the presence of IFNα in macaque lymphocytes. We demonstrate that passage in macaques selects for IFNα resistant viruses that have higher replication kinetics and increased envelope content. SHIVs that encode HIV-1 sequences derived directly from infected humans were sensitive to IFNα -induced inhibition whereas SHIVs obtained after passage in macaques were not. This evolutionary process was directly observed in viruses that were serially passaged during the first few months of infection-a time when the IFNα response is high. Differences in IFNα sensitivity mapped to HIV-1 envelope and were associated with increased envelope levels despite similar mRNA expression, suggesting a post-transcriptional mechanism. These studies highlight critical differences in IFNα sensitivity between HIV-1 sequences in infected people and those used in SHIV models.

SUBMITTER: Boyd DF

PROVIDER: S-EPMC4939950 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Although all 12 subtypes of human interferon alpha (IFN-?) bind the same receptor, recent results have demonstrated that they elicit unique host responses and display distinct efficacies in the control of different viral infections. The IFN-?2 subtype is currently in HIV-1 clinical trials, but it has not consistently reduced viral loads in HIV-1 patients and is not the most effective subtype against HIV-1 in vitro We now demonstrate in humanized mice that, when delivered at the same high clinical dose, the human IFN-?14 subtype has very potent anti-HIV-1 activity whereas IFN-?2 does not. In both postexposure prophylaxis and treatment of acute infections, IFN-?14, but not IFN-?2, significantly suppressed HIV-1 replication and proviral loads. Furthermore, HIV-1-induced immune hyperactivation, which is a prognosticator of disease progression, was reduced by IFN-?14 but not IFN-?2. Whereas ineffective IFN-?2 therapy was associated with CD8(+) T cell activation, successful IFN-?14 therapy was associated with increased intrinsic and innate immunity, including significantly higher induction of tetherin and MX2, increased APOBEC3G signature mutations in HIV-1 proviral DNA, and higher frequencies of TRAIL(+) NK cells. These results identify IFN-?14 as a potent new therapeutic that operates via mechanisms distinct from those of antiretroviral drugs. The ability of IFN-?14 to reduce both viremia and proviral loads in vivo suggests that it has strong potential as a component of a cure strategy for HIV-1 infections. The broad implication of these results is that the antiviral efficacy of each individual IFN-? subtype should be evaluated against the specific virus being treated.The naturally occurring antiviral protein IFN-?2 is used to treat hepatitis viruses but has proven rather ineffective against HIV in comparison to triple therapy with the antiretroviral (ARV) drugs. Although ARVs suppress the replication of HIV, they fail to completely clear infections. Since IFN-? acts by different mechanism than ARVs and has been shown to reduce HIV proviral loads, clinical trials are under way to test whether IFN-?2 combined with ARVs might eradicate HIV-1 infections. IFN-? is actually a family of 12 distinct proteins, and each IFN-? subtype has different efficacies toward different viruses. Here, we use mice that contain a human immune system, so they can be infected with HIV. With this model, we demonstrate that while IFN-?2 is only weakly effective against HIV, IFN-?14 is extremely potent. This discovery identifies IFN-?14 as a more powerful IFN-? subtype for use in combination therapy trials aimed toward an HIV cure.

Project description:Chimeric Simian-Human Immunodeficiency Viruses (SHIVs) are an important tool for evaluating anti-HIV Env interventions in nonhuman primate (NHP) models. However, most unadapted SHIVs do not replicate well in vivo limiting their utility. Furthermore, adaptation in vivo often negatively impacts fundamental properties of the Env, including neutralization profiles. Transmitted/founder (T/F) viruses are particularly important to study since they represent viruses that initiated primary HIV-1 infections and may have unique attributes. Here we combined in vivo competition and rational design to develop novel subtype C SHIVs containing T/F envelopes. We successfully generated 19 new, infectious subtype C SHIVs, which were tested in multiple combinatorial pools in Indian-origin rhesus macaques. Infected animals attained peak viremia within 5 weeks ranging from 103 to 107 vRNA copies/mL. Sequence analysis during primary infection revealed 7 different SHIVs replicating in 8 productively infected animals with certain clones prominent in each animal. We then generated 5 variants each of 6 SHIV clones (3 that predominated and 3 undetectable after pooled in vivo inoculations), converting a serine at Env375 to methionine, tyrosine, histidine, tryptophan or phenylalanine. Overall, most Env375 mutants replicated better in vitro and in vivo than wild type with both higher and earlier peak viremia. In 4 of these SHIV clones (with and without Env375 mutations) we also created mutations at position 281 to include serine, alanine, valine, or threonine. Some Env281 mutations imparted in vitro replication dynamics similar to mutations at 375; however, clones with both mutations did not exhibit incremental benefit. Therefore, we identified unique subtype C T/F SHIVs that replicate in rhesus macaques with improved acute phase replication kinetics without altering phenotype. In vivo competition and rational design can produce functional SHIVs with globally relevant HIV-1 Envs to add to the growing number of SHIV clones for HIV-1 research in NHPs.

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Adapting SHIVs In Vivo Selects for Envelope-Mediated Interferon-α Resistance.

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