Exciting biomedical advances – keep your eyes on the longer-term opportunities for HIV prevention and treatment

Editor’s notes: An important advance on the road to effective immune therapies may have been published in the journal Science [1]. We have now entered the era of antibodies for the prevention, and possibly the treatment of HIV.  The AMP study [2] is the first large scale study of antibodies being used to try to prevent HIV infection.  However, most researchers agree that just like antiretroviral therapy, a cocktail of different antibodies is likely to be needed to prevent HIV escaping from immune control, just as it does from individual medicines.  Xu and colleagues at Sanofi have managed to engineer a molecule that is an antibody except that instead of having a single specific target antigen, had three different targets.  In other words, it might function as a cocktail despite being a single agent.  This is important because it might speed up the critical pathway for research.  With multiple antibodies, the regulators naturally want to be certain that each of them is safe and effective before approving trials that combine them.  This can take many years, despite the researchers predicting that the single antibody studies are proofs of concept on the longer pathway to a combination that might make a real difference to treatment or prevention programmes. In studies in macaques, the novel tri-specific antibody molecule provided complete immunity to infection with a range of simian-human immunodeficiency viruses (SHIVs), whereas single antibodies only protected against some of the SHIVs.  This approach to immunotherapy is also an example of HIV science leading to discoveries that might have a much wider field of application in other diseases such as cancer and autoimmune disease.

In addition to making the best antibodies (or T-cell responses), a vaccine also must deliver the antigen or DNA in such a way that the antibodies are made effectively and in high concentrations by the host’s cells.  This is done by means of the vaccine vector.  Previous HIV vaccine candidates have had to be withdrawn from the research pipeline because their vectors appear to have caused harm, possibly by stimulating the immune system in such a way that HIV replication was actually enhanced.  So, the study by Capucci and colleagues is a useful example to show how different vectors work in animal models.  In this study, two vectors that are usually utilized to stimulate T-cell responses were used.  A non-replicating chimpanzee adenovirus or a non-replicating modified vaccinia virus Ankara both produced good antibody responses using an HIV glycoprotein trimer that is known to produce neutralizing antibodies.  The implication might be that these vectors could carry antigens that could provoke useful antibody responses in addition to useful T-cell responses, thus mimicking the most likely way that HIV is controlled in the human host.

Many studies of new biomedical approaches to HIV prevention are tested first in animal models.  Many of us know little of the details of these models.  In order to compare different prevention technologies, it is important that the same or comparable models are used.  Many studies now use simian-human immunodeficiency virus (SHIV).  This is a virus that is genetically modified so that it expresses many aspects of HIV, but still has enough of the SIV components to infect monkeys.  SHIV is often inserted into the vagina of rhesus macaques that have been treated with a new prevention technology or a control to determine whether the technology prevents the establishment of infection.  In the past most macaques used for this research were from India.  However, there is now a shortage of such laboratory monkeys, so Veazey and Ling have done a simple comparison of Indian macaques with Chinese macaques.  With this particular common laboratory strain of SHIV, the authors found no important differences between the two sub-species.

Delving further into the comparative immunology of macaques and humans, Fu and colleagues have performed a comprehensive profiling of lymphocyte receptors from a Chinese macaque.  These sorts of studies allow vaccine scientists to understand how immune responses in macaques can generate antibody and T-cell responses.  They are a building block for future development of vaccines and immune based therapies.  And they remind us how advanced the technology is becoming for ever more detailed understanding of the interactions between primates’ immune systems and the environment to which these systems are exposed.

 

Trispecific broadly neutralizing HIV antibodies mediate potent SHIV protection in macaques

Xu L, Pegu A, Rao E, Doria-Rose N, Beninga J, McKee K, Lord DM, Wei RR, Deng G, Louder M, Schmidt SD, Mankoff Z, Wu L, Asokan M, Beil C, Lange C, Leuschner WD, Kruip J, Sendak R, Do Kwon Y, Zhou T, Chen X, Bailer RT, Wang K, Choe M, Tartaglia LJ, Barouch DH, O'Dell S, Todd JP, Burton DR, Roederer M, Connors M, Koup RA, Kwong PD, Yang ZY, Mascola JR, Nabel GJ. Science. 2017 Oct 6;358(6359):85-90. doi: 10.1126/science.aan8630. Epub 2017 Sep 20.

The development of an effective AIDS vaccine has been challenging because of viral genetic diversity and the difficulty of generating broadly neutralizing antibodies (bnAbs). We engineered trispecific antibodies (Abs) that allow a single molecule to interact with three independent HIV-1 envelope determinants: the CD4 binding site, the membrane-proximal external region (MPER), and the V1V2 glycan site. Trispecific Abs exhibited higher potency and breadth than any previously described single bnAb, showed pharmacokinetics similar to those of human bnAbs, and conferred complete immunity against a mixture of simian-human immunodeficiency viruses (SHIVs) in nonhuman primates, in contrast to single bnAbs. Trispecific Abs thus constitute a platform to engage multiple therapeutic targets through a single protein, and they may be applicable for treatment of diverse diseases, including infections, cancer, and autoimmunity.

Abstract [3]  Full-text [free] access [4]

HIV-1-neutralizing antibody induced by simian adenovirus- and poxvirus MVA-vectored BG505 native-like envelope trimers

Capucci S, Wee EG, Schiffner T, LaBranche CC, Borthwick N, Cupo A, Dodd J, Dean H, Sattentau Q, Montefiori D, Klasse PJ, Sanders RW, Moore JP, Hanke T. PLoS One. 2017 Aug 9;12(8):e0181886. doi: 10.1371/journal.pone.0181886. eCollection 2017.

Rabbits and monkeys immunized with HIV type 1 (HIV-1) native-like BG505 SOSIP.664 (BG505s) glycoprotein trimers are known to induce antibodies that can neutralize the autologous tier-2 virus. Here, we assessed the induction of HIV-1 trimer binding and neutralizing antibody (nAb) titres when BG505s trimers were also delivered by non-replicating simian (chimpanzee) adenovirus and non-replicating poxvirus modified vaccinia virus Ankara (MVA) vaccine vectors. First, we showed that approximately two-thirds and one-third of the trimers secreted from the ChAdOx1.BG505s (C) and MVA.BG505s (M) vaccine-infected cells, respectively, were cleaved and in a native-like conformation. Rabbits were immunized intramuscularly with these vaccine vectors and in some cases boosted with ISCOMATRIX™-adjuvanted BG505s protein trimer (P), using CCC, MMM, PPP, CPP, MPP and CMP vaccine regimens. We found that the peak trimer-binding antibody and tier-1A and autologous tier-2 nAb responses induced by the CC, CM, PPP, CPP, MPP and CMP regimens were comparable, although only PPP induced autologous tier-2 nAbs in all the immunized animals. Three animals developed weak heterologous tier-2 nAbs. These results demonstrate that ChAdOx1 and MVA vectors are useful delivery modalities for not only T-cell, but also antibody vaccine development.

Abstract [5]  Full-text [free] access [6]

Comparative susceptibility of rhesus macaques of Indian and Chinese origin to vaginal SHIV transmission as models for HIV prevention research

Veazey R, Ling B. AIDS Res Hum Retroviruses. 2017 Aug 10. doi: 10.1089/AID.2017.0173. [Epub ahead of print]

Historically, Indian origin rhesus macaques (iRM) have been preferred for SIV/HIV prevention, pathogenesis, and treatment studies, yet their supply is limited. Chinese origin rhesus macaques (cRM) are currently more available yet little is known regarding the relative susceptibility of this subspecies to vaginal transmission of SIV or SHIV. Here we compared the susceptibility of 40 cRM and 21 iRM to a single vaginal challenge with SHIVsf162P. Our results showed cRM have comparable primary SHIV infection as iRM, underscoring their equal importance in studies of HIV transmission and prevention.

Abstract access [7]

A comprehensive profiling of T- and B-lymphocyte receptor repertoires from a Chinese-origin rhesus macaque by high-throughput sequencing

Fu L, Li X, Zhang W, Wang C, Wu J, Yang H, Wang J, Liu X. PLoS One. 2017 Aug 16;12(8): e0182733. doi: 10.1371/journal.pone.0182733. eCollection 2017.

Due to the close genetic background, high similarity of physiology, and susceptibility to infectious and metabolic diseases with humans, rhesus macaques have been widely used as an important animal model in biomedical research, especially in the study of vaccine development and human immune-related diseases. In recent years, high-throughput sequencing based immune repertoire sequencing (IR-SEQ) has become a powerful tool to study the dynamic adaptive immune responses. Several previous studies had analyzed the responses of B cells to HIV-1 trimer vaccine or T cell repertoire of rhesus macaques using this technique, however, there are little studies that had performed a comprehensive analysis of immune repertoire of rhesus macaques, including T and B lymphocytes. Here, we did a comprehensive analysis of the T and B cells receptor repertoires of a Chinese rhesus macaque based on the 5'-RACE and IR-SEQ. The detailed analysis includes the distribution of CDR3 length, the composition of amino acids and nucleotides of CDR3, V, J and V-J combination usage, the insertion and deletion length distribution and somatic hypermutation rates of the framework region 3 (FR3). In addition, we found that several positions of FR3 region have high mutation frequencies, which may indicate the existence of new genes/alleles that have not been discovered and/or collected into IMGT reference database. We believe that a comprehensive profiling of immune repertoire of rhesus macaque will facilitate the human immune-related diseases studies.

Abstract [8]  Full-text [free] access [9]

Basic science [11]
Asia [12], Northern America [13]
China [14], United States of America [15]
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