Serologically confirmed primary HBoV infections detected in 12 symptomatic children with no signs of other respiratory virus infections (by PCR, culture, antigen detection, or serologic analysis) demonstrate that HBoV is a cause of acute wheezing in young children. Moreover, the fact that acute HBoV infection was detected in 27% of hospitalized children who were <2 years of age when they had their first episode of wheezing indicates that HBoV is a causative agent of bronchiolitis with clinical severity comparable with that of RSV. HBoV respiratory infections can be diagnosed with moderate accuracy by qPCR of NPAs. However, the most reliable methods for diagnosis of acute symptomatic HBoV infection are PCR of serum samples and serologic analysis for IgM and IgG. Evidence that Gag facilitates HIV-1 envelope association both in GPI-enriched plasma membrane and detergent resistant membranes and facilitates envelope incorporation onto virions in primary CD4(+ )T cells HIV-1 particle assembly mediated by viral Gag protein occurs predominantly at plasma membrane. While colocalization of HIV-1 envelope with lipid rich microenvironment have been shown in T cells, the significance of viral proteins modulating envelope association in such microdomains in plasma membrane enriched in glycosylphosphatidylinositol-anchored proteins in primary CD4(+ )T cells that are natural targets of HIV-1 is poorly understood. Here we show that in primary CD4(+ )T cells that are natural targets of HIV-1 in vivo, Gag modulates HIV-1 envelope association with GM1 ganglioside and CD59 rich cellular compartments as well as with detergent resistant membranes. Our data strengthen evidence that Gag-Env interaction is important in envelope association with lipid rafts containing GPI-anchored proteins for efficient assembly onto mature virions resulting in productive infection of primary CD4(+ )T cells. glycoprotein while abundant incorporation of raft lipid components such as ganglioside GM1, glycosylphosphatidylinositol (GPI)-anchored proteins Thy-1 and CD59 strongly suggest that HIV-1 specifically buds from rafts [5, 11] . A stable interaction between intracellular Pr55Gag and the gp41 cytoplasmic domain of envelope [12] was shown to be important for envelope association with detergent resistant membranes, incorporation onto virions and infectivity [13, 14] . The precise sequence by which envelope utilizes cellular machinery in migrating towards the site of viral assembly is not clearly understood. Glycoproteins of several enveloped viruses, have been found to contain lipid moieties [15, 16] and has generated notion on the importance of lipid rafts as a docking site for the assembly of enveloped viruses [17] [18] [19] [20] [21] [22] . Association of HIV-1 envelope with polarized lipid raft markers GM1 and CD59 was shown to influence transmission between T cells [10] . Gag has been shown to play an important role in envelope assembly onto virions, notably by interaction of its p17 matrix domain with gp41 cytoplasmic domain of envelope [14, [23] [24] [25] . While HIV Gag intrinsically associates with detergent resistant membranes (DRMs) [5, 26] , influenza virus M1 protein transport to DRMs depends on coexpression of HA and NA glycoproteins [27] . Likewise, the association of Sendai virus M protein in DRM is dependent on expression of F or HN protein [28] , while the Rous sarcoma virus M protein requires expression with the F protein for DRM association [29] . In contrast, the Measles virus M protein has been shown to associate DRMs intrinsically independent of other viral proteins [30] . Motifs in gp41 cytoplasmic domain regulating association of HIV-1 envelope protein with DRM [8] and this phenomenon is Gag dependent in a T cell line [13] was previously reported. However, it was not known whether this phenomenon is cell type-dependent and if it differs between cell lines and those that are natural targets in vivo. Moreover, whether DRM association of envelope corroborates with their ability to traffic to classical lipid rafts was also not known. In the present study we investigated the role of Gag in intracellular transport of HIV-1 envelope into well defined GPI-anchored proteins such as CD59 and GM1 (monosialotetrahexosylganglioside) and its relevance of envelope assembly onto budding virions in primary CD4 + T cells. Precisely, we examined whether a point mutation (L30E) in matrix domain of Gag known for disrupting Env incorporation [23, 31] affects envelope trafficking to CD59+ compartment in primary CD4 + T cells and if this phenomenon has any association with cellfree infectivity in primary CD4 + T cells.