Immunoreactivity of Intact Virions of Human Immunodeficiency Virus Type 1 (HIV-1) Reveals the Existence of Fewer HIV-1 Immunotypes than Genotypes

Abstract

In order to protect against organisms that exhibit significant genetic variation, polyvalent vaccines are needed. Given the extreme variability of human immunodeficiency virus type 1 (HIV-1), it is probable that a polyvalent vaccine will also be needed for protection from this virus. However, to understand how to construct a polyvalent vaccine, serotypes or immunotypes of HIV must be identified. In the present study, we have examined the immunologic relatedness of intact, native HIV-1 primary isolates of group M, clades A to H, with human monoclonal antibodies (MAbs) directed at epitopes in the V3, C5, and gp41 cluster I regions of the envelope glycoproteins, since these regions are well exposed on the virion surface. Multivariate analysis of the binding data revealed three immunotypes of HIV-1 and five MAb groups useful for immunotyping of the viruses. The analysis revealed that there are fewer immunotypes than genotypes of HIV and that clustering of the isolates did not correlate with either genotypes, coreceptor usage (CCR5 and CXCR4), or geographic origin of the isolates. Further analysis revealed distinct MAb groups that bound preferentially to HIV-1 isolates belonging to particular immunotypes or that bound to all three immunotypes; this demonstrates that viral immunotypes identified by mathematical analysis are indeed defined by their immunologic characteristics. In summary, these results indicate (i) that HIV-1 immunotypes can be defined, (ii) that constellations of epitopes that are conserved among isolates belonging to each individual HIV-1 immunotype exist and that these distinguish each of the immunotypes, and (iii) that there are also epitopes that are routinely shared by all immunotypes.

Comprehensive Cross-Clade Neutralization Analysis of a Panel of Anti-Human Immunodeficiency Virus Type 1 Monoclonal Antibodies

“…MAb 447-52D has been reported to occasionally neutralize some viruses from non-B clades, including clades A, D, and F (45,48,49,101). However, in our panel, neutralization outside clade B was rare (4 of 61 [ϳ7%]).…”

“…However, practical limitations on the number of samples, the polyclonal nature of sera, the typically low serum neutralizing titers, background noise and limited sampling, and the difficulty of controlling for falsepositive neutralization data have meant that it has been difficult to conduct a definitive analysis. Previous studies describing immunotyping with MAbs were mostly based on binding and not on neutralization (99,101,151). Interestingly, one study of immunotypes based on binding (rather than neutralization) of a panel of MAbs to the V3 loop, C5 region, or gp41 immunodominant loop, all known to be either weakly or nonneutralizing, resulted in three immunotype clusters (99).…”

“…The overall difficulty of determining cladeassociated neutralizing immunotype groups may be because sequence differences that determine genetic clades do not influence neutralization epitopes (71) or that limited sampling and high background noise activity complicate cross-clade neutralization analyses (92,101,152).…”

Biologic and Genetic Characterization of a Panel of 60 Human Immunodeficiency Virus Type 1 Isolates, Representing Clades A, B, C, D, CRF01_AE, and CRF02_AG, for the Development and Assessment of Candidate Vaccines

“…Viral supernatant was harvested from cultures when p24 values exceeded 50 ng/ml and was stored in 0.5-to 1-ml aliquots in a liquid nitrogen freezer. Titers of the viral stocks were then determined to obtain the 50% tissue culture infectious dose (TCID 50 ).…”

“…To characterize the infectivity and replication properties of the viruses in this panel, the TCID 50 per 25 l was determined for each isolate, and the stock p24 antigen concentration (ng/ml) was quantified. Figure 2 lists the biological properties of the isolates in the panel, including p24 antigen concentration, TCID 50 , syncytial phenotype, and coreceptor usage. The infectious titers did not correlate with the extracellular level of p24 at the time of harvest of the virus stocks (Fig.…”