title: Functional stability of unliganded envelope glycoprotein spikes among isolates of human immunodeficiency virus type 1 (HIV-1).
abstract: The HIV-1 envelope glycoprotein (Env) spike is challenging to study at the molecular level, due in part to its genetic variability, structural heterogeneity and lability. However, the extent of lability in Env function, particularly for primary isolates across clades, has not been explored. Here, we probe stability of function for variant Envs of a range of isolates from chronic and acute infection, and from clades A, B and C, all on a constant virus backbone. Stability is elucidated in terms of the sensitivity of isolate infectivity to destabilizing conditions. A heat-gradient assay was used to determine T(90) values, the temperature at which HIV-1 infectivity is decreased by 90% in 1 h, which ranged between ∼40 to 49°C (n = 34). For select Envs (n = 10), the half-lives of infectivity decay at 37°C were also determined and these correlated significantly with the T(90) (p = 0.029), though two 'outliers' were identified. Specificity in functional Env stability was also evident. For example, Env variant HIV-1(ADA) was found to be labile to heat, 37°C decay, and guanidinium hydrochloride but not to urea or extremes of pH, when compared to its thermostable counterpart, HIV-1(JR-CSF). Blue native PAGE analyses revealed that Env-dependent viral inactivation preceded complete dissociation of Env trimers. The viral membrane and membrane-proximal external region (MPER) of gp41 were also shown to be important for maintaining trimer stability at physiological temperature. Overall, our results indicate that primary HIV-1 Envs can have diverse sensitivities to functional inactivation in vitro, including at physiological temperature, and suggest that parameters of functional Env stability may be helpful in the study and optimization of native Env mimetics and vaccines.
authors: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America.
authors: Nitish
authors: N
authors: Agrawal
authors: Daniel P
authors: DP
authors: Leaman
authors: Eric
authors: E
authors: Rowcliffe
authors: Heather
authors: H
authors: Kinkead
authors: Raman
authors: R
authors: Nohria
authors: Junya
authors: J
authors: Akagi
authors: Katherine
authors: K
authors: Bauer
authors: Sean X
authors: SX
authors: Du
authors: Robert G
authors: RG
authors: Whalen
authors: Dennis R
authors: DR
authors: Burton
authors: Michael B
authors: MB
authors: Zwick
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D057809:HEK293 Cells; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000235:genetics / Q000378:metabolism; D054303:HIV Reverse Transcriptase / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D013696:Temperature; D054299:env Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D054299:env Gene Products, Human Immunodeficiency Virus; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase