Association between HIV Type 1-specific T cell responses and CD4+ T cell counts or CD4+:CD8+ T cell ratios in HIV Type 1 subtype B infection in China

Dynamic correlation between CTL response and viral load in primary human immunodeficiency virus-1 infected Koreans

Background

HIV-1 specific cytotoxic T lymphocytes (CTLs) have an important role as antiviral effector cells for controlling HIV-1 infection.

Methods

To investigate CTL response during the early stage of HIV infection, we measured immunity-related factors including CD4⁺ T cell counts, CD8⁺ T cell counts, HIV-1 RNA viral loads and IFN-γ secretion according to CTL response in 78 selected primary HIV-1-infected Koreans.

Results

The CTL response was strongly induced by HIV-1 specific Gag and Nef peptides (p = 0.016) compared with induction by Tat or Env peptides. These results suggest that the major antiviral factors inducing strong HIV-specific CTL responses are associated with the Gag and Nef viral regions in primary HIV-1 infected Koreans. The relationship between viral load and CTL response showed varying correlations with time following HIV infection. CTL response was inversely correlated with viral loads at preseroconversion stage I (r = -0.224 to -0.33) and changed to a positive correlation at the preseroconversion stage II (r = 0.132 to 0.854). Finally, it changed to an inverse correlation again after seroconversion until a viral set point was established on serological profiling (r = -0.195 to -0.407).

Conclusions

These findings demonstrate a dynamic correlation between viral load and subsequent CTL responses during early HIV infection.

Efficient inhibition of SIV replication in rhesus CD4+ T-cell clones by autologous immortalized SIV-specific CD8+ T-cell clones

CD8(+) cytotoxic T lymphocyte (CTL) responses play an important role in controlling the replication of primate lentiviruses. Induction of these responses is a key objective for most current AIDS vaccine approaches. Despite a variety of approaches for measuring properties and activities of CTL, the functions responsible for controlling viral replication in vivo have not been clearly identified. Assays measuring CTL-mediated suppression of viral replication in vitro are beginning to be used as possible correlates of in vivo virus suppressive activity, but the utility and interpretive value of these assays are typically limited by properties of the cells that have been used. We investigated the capacity of SIV-specific CTL clones (effectors), immortalized by transduction with human telomerase reverse transcriptase (hTERT), to suppress SIV replication in autologous hTERT immortalized CD4(+) T-cell clones (targets). Immortalized and non-immortalized SIV-specific effector cells showed IFN-gamma production and degranulation in response to viral antigen specific stimulation and significantly inhibited SIV(mac)239 replication (2 to 4 log decrease in viral RNA or cell-associated proviral DNA) (p<0.0005). Our in vitro assays of inhibition of viral replication, using T-cell clones as effectors and targets, provide a well-defined approach for evaluating possible mechanisms of CTL-mediated control of viral production which may involve direct killing of infected target cells and/or release of proinflammatory cytokines such as IFN-gamma and TNF-alpha. The use of hTERT immortalized effector and target cells for such assays preserves relevant functional properties while providing a convenient, reproducible means of conducting studies over time.

Human immunodeficiency virus type 1 specific cytotoxic T lymphocyte responses in Chinese infected with HIV-1 B'/C Recombinant (CRF07_BC)

BACKGROUND

The characterization of HIV-1-specific T cell responses in people infected with locally circulating HIV-1 strain will facilitate the development of HIV-1 vaccine. Sixty intravenous drug users infected with HIV-1 circulating recombinant form 07_BC (CRF07_BC), which has been spreading rapidly in western China from north to south, were recruited from Xinjiang, China to assess the HIV-1-specific T cell responses at single peptide level with overlapping peptides (OLP) covering the whole concensus clades B and C proteome.

RESULTS

The median of the total magnitude and total number of OLPs recognized by CTL responses were 10925 SFC/million PBMC and 25 OLPs, respectively, when tested by clade C peptides, which was significantly higher than when tested by clade B peptides. The immunodominant regions, which cover 14% (58/413) of the HIV-1 proteome, are widely distributed throughout the HIV-1 proteome except in Tat, Vpu and Pol-PR, with Gag, Pol-RT, Pol-Int and Nef being most frequently targeted. The subdominant epitopes are mostly located in p24, Nef, integrase, Vpr and Vif. Of the responses directed to clade C OLPs, 61.75% (972/1574) can be observed when tested with corresponding clade B OLPs. However, Pol-PR and Vpu tend to be targeted in the clade B sequence rather than the clade C sequence, which is in line with the recombinant pattern of CRF07_BC. Stronger and broader CTL responses in subjects with CD4 cell counts ranging from 200 to 400/mm3 were observed when compared to those with less than 200/mm3 or more than 400/mm3, though there have been no significant correlations identified between the accumulative CTL responses or overall breadth and CD4 cell count or plasma viral load.

CONCLUSION

This is the first study conducted to comprehensively address T cell responses in Chinese subjects infected with HIV-1 CRF07_BC in which subtle differences in cross-reactivity were observed, though similar patterns of overall immune responses were demonstrated with clade B infected populations. The immunodominant regions identified in this population can facilitate future HIV-1 vaccine development in China.