The Neutralizing Linear Epitope of Human Herpesvirus 6A Glycoprotein B Does Not Affect Virus Infectivity

Wakata, Aika; Kanemoto, Satoshi; Tang, Huiping; Kawabata, Akiko; Nishimura, Mitsuhiro; Jasirwan, Chyntia Olivia Maurine; Mahmoud, Nora F.; Mori, Yasuko

doi:10.1128/jvi.02074-17

Cited by 3 publications

(3 citation statements)

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“…The entry of herpesvirus into host cells is usually described as a cascade (13). For HHV-6B, according to our results, the binding of the gH/gL/gQ1/gQ2 complex to its cell receptor, CD134, may activate glycoprotein B (gB) function (15,17). The conserved fusogens of herpesvirus, gB and gH, collaborate in mediating the fusion between the viral envelope and the cell membrane in the entry process (17).…”

Section: Discussionmentioning

confidence: 58%

“…For HHV-6B, according to our results, the binding of the gH/gL/gQ1/gQ2 complex to its cell receptor, CD134, may activate glycoprotein B (gB) function (15,17). The conserved fusogens of herpesvirus, gB and gH, collaborate in mediating the fusion between the viral envelope and the cell membrane in the entry process (17). The different binding domains of each MAb may exert different effects at each step of viral entry.…”

Section: Discussionmentioning

confidence: 84%

“…Although the detailed function of gH/gL/gQ1/gQ2 is still unclear, it is suggested that gH/gL/gQ1/gQ2 has at least two functions: recognizing the receptor and activating gB fusion activity. gQ1 is the crucial component for receptor recognition, and gQ2 might assist in its function as a chaperone (16,17). On the other hand, gH and gL are suggested to be responsible for gB activation.…”

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confidence: 99%

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Humanization of Murine Neutralizing Antibodies against Human Herpesvirus 6B

Wang

Nishimura

Maekawa

et al. 2019

J Virol

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Exanthem subitum is a common childhood illness caused by primary infection with human herpesvirus 6B (HHV-6B). It is occasionally complicated by febrile seizures and even encephalitis. HHV-6B reactivation also causes encephalitis, especially after allogeneic hematopoietic stem cell transplantation. However, no adequate antiviral treatment for HHV-6B has yet been established. Mouse-derived monoclonal antibodies (MAbs) against the HHV-6B envelope glycoprotein complex gH/gL/gQ1/gQ2 have been shown to neutralize the viral infection. These antibodies have the potential to become antiviral agents against HHV-6B despite their inherent immunogenicity to the human immune system. Humanization of MAbs derived from other species is one of the proven solutions to such a dilemma. In this study, we constructed chimeric forms of two neutralizing MAbs against HHV-6B to make humanized antibodies. Both showed neutralizing activities equivalent to those of their original forms. This is the first report of humanized antibodies against HHV-6B and provides a basis for the further development of HHV-6B-specific antivirals. IMPORTANCE Human herpesvirus 6B (HHV-6B) establishes lifelong latent infection in most individuals after the primary infection. Encephalitis is the most severe complication caused by both the primary infection and the reactivation of HHV-6B and is the cause of considerable mortality in patients, without any established treatments to date. The humanization of the murine neutralizing antibodies described in this research provided a feasible way to reduce the inherent immunogenicity of the antibodies without changing their neutralizing activities. These newly designed chimeric antibodies against HHV-6B have the potential to be candidates for antivirals for future use. a IC 50 , half-maximal inhibitory concentration. FIG 7 Model of the possible mechanisms of neutralization by MAbs KH-1 and OHV-3. For HHV-6B entry, the gH/gL/gQ1/gQ2 glycoprotein complex, especially gQ1, binds directly to the cell receptor CD134. (A) KH-1, which interacts with gQ1, could directly inhibit receptor binding. (B) The interaction of gH with OHV-3 could affect gH function (fusion or association with gB) and thus inhibit viral entry. Humanization of Neutralizing MAbs against HHV-6B Journal of Virology May 2019 Volume 93 Issue 10 e02270-18 jvi.asm.org 7proteins by MAbs may affect their functions for entry. Further studies are required to answer these questions. MATERIALS AND METHODS Cells and viruses.Human embryonic kidney (HEK) 293T cells were cultured at 37°C under 5% CO 2 in Dulbecco's modified Eagle medium (DMEM) containing 8% fetal bovine serum, 4 mM L-glutamine, and 20 g/ml gentamicin. Serum-free CD 293 medium (Thermo Fisher Scientific) supplemented with 4 mM L-glutamine and 20 g/ml gentamicin was used after transfections. The human T-cell line MT4 was cultured in RPMI 1640 medium with 8% fetal bovine serum containing 20 g/ml gentamicin. HHV-6B strain HST was prepared as described previously (15). For virus propagation, umbilical cord blood m...

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Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 84%

mentioning

confidence: 99%

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Humanization of Murine Neutralizing Antibodies against Human Herpesvirus 6B

Wang

Nishimura

Maekawa

et al. 2019

J Virol

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Entry of betaherpesviruses

Nishimura

Mori

2019

Virus Entry

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The Combination of gQ1 and gQ2 in Human Herpesvirus 6A and 6B Regulates the Viral Tetramer Function for Their Receptor Recognition

Wakata

Tjan

Nishimura

et al. 2021

J Virol

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Human herpesvirus 6A (HHV-6A) and HHV-6B use different cellular receptors, human CD46 and CD134, respectively and have different cell tropisms although they have 90% similarity at the nucleotide level. An important feature that characterizes HHV-6A/6B is the glycoprotein H (gH)/gL/gQ1/gQ2 complex (a tetramer) that each virus has specifically on its envelope. Here, to determine which molecules in the tetramer contribute to the specificity for each receptor, we developed a cell-cell fusion assay system for HHV-6A and HHV-6B that uses the cells expressing CD46 or CD134. With this system, when we replaced the gQ1 or gQ2 of HHV-6A with that of HHV-6B in the tetramer, the cell fusion activity mediated by glycoproteins via CD46 was lower than that done with the original-type tetramer. When we replaced the gQ1 or the gQ2 of HHV-6A with that of HHV-6B in the tetramer, the cell fusion mediated by glycoproteins via CD134 was not seen. In addition, we generated two types of C-terminal truncation mutants of HHV-6A gQ2 (AgQ2) to examine the interaction domains of HHV-6A gQ1 (AgQ1) and AgQ2. We found that amino acid residues 163 to 185 in AgQ2 are important for interaction of AgQ1 and AgQ2. Finally, to investigate whether HHV-6B gQ2 (BgQ2) can complement AgQ2, an HHV-6A genome harboring BgQ2 was constructed. The mutant could not produce an infectious virus, indicating that BgQ2 cannot work for the propagation of HHV-6A. These results suggest that gQ2 supports the tetramer's function, and the combination of gQ1 and gQ2 is critical for virus propagation. IMPORTANCE Glycoprotein Q2 (gQ2), an essential gene for virus propagation, forms a heterodimer with gQ1. The gQ1/gQ2 complex has a critical role in receptor recognition in the gH/gL/gQ1/gQ2 complex (a tetramer). We investigated whether gQ2 regulates the specific interaction between the HHV-6A or -6B tetramer and CD46 or CD134. We established a cell-cell fusion assay system for HHV-6A/6B and switched the gQ1 or gQ2 of HHV-6A with that of HHV-6B in the tetramer. Although cell fusion was induced via CD46 when gQ1 or gQ2 was switched between HHV-6A and -6B, the activity was lower than that of the original combination. When gQ1 or gQ2 was switched in HHV-6A and -6B, no cell fusion was observed via CD134. HHV-6B gQ2 could not complement the function of HHV-6A's gQ2 in HHV-6A propagation, suggesting that the combination of gQ1 and gQ2 is critical to regulate the specificity of the tetramer's function for virus entry.

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The Neutralizing Linear Epitope of Human Herpesvirus 6A Glycoprotein B Does Not Affect Virus Infectivity

Cited by 3 publications

References 57 publications

Humanization of Murine Neutralizing Antibodies against Human Herpesvirus 6B

Humanization of Murine Neutralizing Antibodies against Human Herpesvirus 6B

Entry of betaherpesviruses

The Combination of gQ1 and gQ2 in Human Herpesvirus 6A and 6B Regulates the Viral Tetramer Function for Their Receptor Recognition

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