West Nile virus (WNV) is a neurotropic flavivirus within the Japanese encephalitis antigenic complex that is responsible for causing West Nile encephalitis in humans. The surface of WNV virions is covered by a highly ordered icosahedral array of envelope proteins that is responsible for mediating attachment and fusion with target cells. These envelope proteins are also primary targets for the generation of neutralizing antibodies in vivo. In this study, we describe a novel approach for measuring antibody-mediated neutralization of WNV infection using virus-like particles that measure infection as a function of reporter gene expression. These reporter virus particles (RVPs) are produced by complementation of a sub-genomic replicon with WNV structural proteins provided in trans using conventional DNA expression vectors. The precision and accuracy of this approach stem from an ability to measure the outcome of the interaction between antibody and viral antigens under conditions that satisfy the assumptions of the law of mass action as applied to virus neutralization. In addition to its quantitative strengths, this approach allows the production of WNV RVPs bearing the prM-E proteins of different WNV strains and mutants, offering considerable flexibility for the study of the humoral immune response to WNV in vitro. WNV RVPs are capable of only a single round of infection, can be used under BSL-2 conditions, and offer a rapid and quantitative approach for detecting virus entry and its inhibition by neutralizing antibody.

"Elite controllers" are individuals that durably control human immunodeficiency virus or simian immunodeficiency virus replication without therapeutic intervention. The study of these rare individuals may facilitate the definition of a successful immune response to immunodeficiency viruses. Here we describe six Indian-origin rhesus macaques that have controlled replication of the pathogenic virus SIVmac239 for 1 to 5 years. To determine which lymphocyte populations were responsible for this control, we transiently depleted the animals' CD8 ؉ cells in vivo. This treatment resulted in 100-to 10,000-fold increases in viremia. When the CD8 ؉ cells returned, control was reestablished and the levels of small subsets of previously subdominant CD8 ؉ T cells expanded up to 2,500-fold above predepletion levels. This wave of CD8 ؉ T cells was accompanied by robust Gag-specific CD4 responses. In contrast, CD8؉ NK cell frequencies changed no more than threefold. Together, our data suggest that CD8؉ T cells targeting a small number of epitopes, along with broad CD4 ؉ T-cell responses, can successfully control the replication of the AIDS virus. It is likely that subdominant CD8 ؉ T-cell populations play a key role in maintaining this control.

We produced nine monoclonal antibodies (MAbs) directed against the West Nile virus E glycoprotein using three different immunization strategies: inactivated virus, naked DNA, and recombinant protein. Most of the MAbs bound to conformation dependent epitopes in domain III of the E protein. Four of the MAbs neutralized WNV infection and bound to the same region of domain III with high affinity. The neutralizing MAbs were obtained from mice immunized with inactivated virus alone or in combination with a DNA plasmid. In contrast, MAbs obtained by immunization with a soluble version of the E glycoprotein did not exhibit neutralizing activity. These non-neutralizing antibodies were cross-reactive with several other flaviviruses, including Saint Louis encephalitis, Japanese encephalitis, Yellow Fever and Powassan viruses. Interestingly, some non-neutralizing MAbs bound with high affinity to domains I or III, indicating that both affinity and the precise epitope recognized by an antibody are important determinants of WNV neutralization.

West Nile virus is a mosquito-borne, neurotropic flavivirus that causes encephalitis in humans and animals. Since being introduced into the Western hemisphere in 1999, WNV has spread rapidly across North America, identifying this virus as an important emerging pathogen. In this study, we developed a DNA-launched infectious molecular clone of WNV that encodes a GFP reporter gene. Transfection of cells with the plasmid encoding this recombinant virus (pWNII-GFP) resulted in the production of infectious WNV capable of expressing GFP at high levels shortly after infection of a variety of cell types, including primary neurons and dendritic cells. Infection of cells with WNII-GFP virus was productive, and could be inhibited with both monoclonal antibodies and interferon-beta, highlighting the potential of this system in the development and characterization of novel inhibitors and therapeutics for WNV infection. As expected, insertion of the reporter gene into the viral genome was associated with a reduced rate of viral replication, providing the selective pressure for the development of variants that no longer encoded the full-length reporter gene cassette. We anticipate this DNA-based, infectious WNV reporter virus will allow novel approaches for the study of WNV infection and its inhibition both in vitro and in vivo.

؉ animals controlled viral replication to <20,000 viral RNA (vRNA) copy equivalents (eq)/ml plasma, while 10 of 15 wild-type-infected Mamu-B*08 ؉ animals had viral loads of <20,000 vRNA copy eq/ml (P ‫؍‬ 0.04). Our results suggest that these epitope-specific CD8؉ T-cell responses may play a role in establishing the control of viral replication in Mamu-B*08 ؉ macaques.

Cryptic major histocompatibility complex class I epitopes have been detected in several pathogens, but their importance in the immune response to AIDS viruses remains unknown. Here, we show that Mamu-B*17 + simian immunodeficiency virus (SIV)mac239-infected rhesus macaques that spontaneously controlled viral replication consistently made strong CD8+ T lymphocyte (CD8-TL) responses against a cryptic epitope, RHLAFKCLW (cRW9). Importantly, cRW9-specific CD8-TL selected for viral variation in vivo and effectively suppressed SIV replication in vitro, suggesting that they might play a key role in the SIV-specific response. The discovery of an immunodominant CD8-TL response in elite controller macaques against a cryptic epitope suggests that the AIDS virus–specific cellular immune response is likely far more complex than is generally assumed.

Human immunodeficiency virus (HIV)'

Wasting is a sign of various underlying disorders and is a common feature of cancer, sepsis, and AIDS. We have developed an in vivo model to study the various stages of wasting following infection of mice with lymphocytic choriomeningitis virus cl-13. Using this model we have identified four distinct stages of wasting and have discovered that all stages occur in the different groups of mice regardless of whether the virus is cleared or persists. However, the degree and extent of wasting varies between groups of mice, depending upon the dose of virus administered. Blocking IFNγ or TNFα, which are believed to take part in the wasting process, did not affect the wasting state. Finally, we found that CD4+ T cells control the maintenance stage of wasting. We believe this model will be useful in studying the regulation of wasting during a persistent viral infection, hopefully leading to improved therapies to ameliorate the disorder.