Viruses. 2018 May 16;10(5). pii: E262. doi: 10.3390/v10050262.

Gp120 V5 Is Targeted by the First Wave of Sequential Neutralizing Antibodies in SHIVSF162P3N-Infected Rhesus Macaques.

Jia M1, Lu H2, Kong XP3, Cheng-Mayer C4, Wu X5.

1 Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, NY 10016, USA. mjia@adarc.org.
2 Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, NY 10016, USA. lhong@adarc.org.
3 School of Medicine, New York University, New York, NY 10016, USA. xiangpeng.kong@med.nyu.edu.
4 Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, NY 10016, USA. cmayer@adarc.org.
5 Aaron Diamond AIDS Research Center, Affiliate of The Rockefeller University, New York, NY 10016, USA. xwu@adarc.org.

 

Abstract

Simian-human immunodeficiency virus (SHIV) infection provides a relevant animal model to study HIV-1 neutralization breadth. With previously identified SHIVSF162P3N infected rhesus macaques that did or did not develop neutralization breadth, we characterized the transmitted/founder viruses and initial autologous/homologous neutralizing antibodies in these animals. The plasma viral load and blood CD4 count did not distinguish macaques with and without breadth, and only one tested homologous envelope clone revealed a trend for macaques with breadth to favor an early homologous response. In two macaques with breadth, GB40 and FF69, infected with uncloned SHIVSF162P3N, multiple viral variants were transmitted, and the transmitted variants were not equal in neutralization sensitivity. The targets of initial autologous neutralizing antibodies, arising between 10 and 20 weeks post infection, were mapped to N462 glycan and G460a in gp120 V5 in GB40 and FF69, respectively. Although it is unclear whether these targets are related to later neutralization breadth development, the G460a target but not N462 glycan appeared more common in macaques with breadth than those without. Longitudinal plasmas revealed 2⁻3 sequential waves of neutralizing antibodies in macaques with breadth, implicating that 3 sequential envelope variants, if not more, may be required for the broadening of HIV-1 neutralizing antibodies.

KEYWORDS: HIV vaccine; SHIV; neutralizing antibody; rhesus macaque

PMID: 29772652

 

Supplement:

The SHIV infection of rhesus macaques provides a valid animal model to investigate the immunogenicity of the viral envelope (Env) for the generation of neutralizing antibodies (nAbs) to HIV-1. Using four autologous/homologous Env clones 4, 8, 10, and 11 (tier 2) derived from the SHIV inoculum, we screened 13 SHIVSF162P3N-infected rhesus macaques with sustained viral load for at least a year and found 11 developed tier 2 nAbs [1]. Two animals, EJ58 and EE29, however, exhibited no evidence of tier 2 nAb development (Figure 1). In EJ58, the lack of nAbs was likely caused by an unusually high level of viral replication (plasma viral load set-point close to 106 copies/mL as compared to an average of 105 copies/mL in other infected animals) and consequently diminished CD4+ T cell count in peripheral blood by 40 weeks post infection. In EE29, an increase in viral replication (plasma viral load) and a corresponding loss of blood CD4+ T cell count was observed after 40 weeks post infection, and the animal only developed nAbs against the parental easy-to-neutralize tier 1A HIV-1 clade B Env strain SF162 but not against any of the four tier 2 autologous/homologous SHIV Env clones.

Among the 11 SHIVSF162P3N-infected rhesus macaques with autologous/homologous tier 2 nAbs, five were of particular interest as they demonstrated cross-reactivity against tier 2 heterologous HIV-1 strains [1]. We thus compared the plasma viral load and blood CD4 count between the two groups of macaques with and without neutralization breadth but found no significant difference [2]. We next compared longitudinal nAb titers between the two groups and found that nAb titers against the Env clone 10 supported a trend for the group of macaques with breadth to favor an early nAb response [2].

 

 

Figure 1. SHIVSF162P3N-infected macaques EJ58 and EE29. Longitudinal plasma neutralization ID50 titer, viral load, and blood CD4 count in SHIVSF162P3N-infected macaques EJ58 and EE29.

 

 

Figure 2. Neutralization assessment of the Env clone GB40_w2_1. Neutralization comparisons between the Env wild-type and its mutant with N462S to CD4-Ig and the indicated bnAbs with known epitopes.

 

We then examined in details two infected macaques – GB40 and FF69, with neutralization breadth. The initial nAbs (1st wave) in FF69 arose at 10 weeks post infection, and the 1st wave nAbs in GB40 arose at 19 weeks post infection. We examined the transmitted/founder (T/F) viruses and found that both animals were infected with multiple T/F variants, and that the dominant T/F variants were sensitive to the 1st wave nAb responses, as expected. We examined the differences in sequence between sensitive and resistant Env clones and mapped the target of 1st wave nAbs to gp120 V5 – specifically, to N462 glycan in GB40 and to G460a in FF69 [2]. To examine whether the point mutation N462S introduced to Env clone GB40_w2_1, or G460aE introduced to Env clone FF69_w8_41, caused any global antigenic disruption of the Env trimer, we compared the neutralization sensitivity between the wild-type and mutant Envs and found no or minimal change to neutralization by CD4-Ig and 7 broadly neutralizing antibodies (bnAbs) with known epitopes [3-4] (Figures 2 and 3). This data indicated that the tested mutations did not cause global antigenic disruption of the Env trimer, thus validating the targets revealed by neutralization differences detected in the tested animal plasmas between the wild-type and mutant Envs.

Because all 11 macaques examined in our study [2] were infected with the same SHIVSF162P3N isolate or its derivative molecular clones, it was not surprising to observe some cross-reactivity in nAbs among these animals. For example, as we showed in the study [2], early plasmas from GB40, FF69, GL26 and DD80 were cross-reactive, capable of neutralizing the Env clones GB40_w2_1, FF69_w8_41, or both; however, the early plasma from FD83 did not neutralize either Env clone (Figure 4), indicating a lack of nAb cross-reactivity between GB40/FF69 and FD83. This notion was supported by the facts that FD83 was infected with the molecular clone 8, and clone 8 was resistant to the 1st wave nAbs in both GB40 and FF69. As clone 8 has a different gp120 V5 sequence from those targeted by the 1st wave nAbs in GB40 and FF69, it would be interesting to determine the target of the 1st wave nAbs in FD83. Although it is unclear whether the target of the 1st wave nAbs is relevant to later development of neutralization breadth, G460a but not N462 glycan appeared more commonly targeted in macaques with breadth than those without [2].

Finally, longitudinal plasma analysis of all five infected macaques with neutralization breadth revealed 2-3 sequential waves of nAbs, implicating that 3 sequential Env variants, if not more, may be required for the broadening of nAbs to cover a wide range of heterologous HIV-1 strains. In this regard, it is of utmost importance for the follow-up research to isolate and determine the sequential Env clones that correspond to the elicitation of the 2nd and 3rd waves of nAbs in these animals.

 

 

Figure 3. Neutralization assessment of the Env clone FF69_w8_41. Neutralization comparisons between the Env wild-type and its mutant with G460aE to CD4-Ig and the indicated bnAbs with known epitopes.

 

 

Figure 4. SHIVSF162P3N clone 8-infected macaque FD83. Neutralization profiles of the FD83 early plasma (1st wave) against the indicated Env clones and their mutants from GB40 and FF69.

 

 

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