What is the impact of SARS-CoV-2 on HIV-1 infectivity?

In a recent study posted on research plaza*Preprint Server, Researchers Investigate Effect of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and SARS-CoV Envelope (E) Protein on Human Immunodeficiency Virus Type 1 (HIV-1) Infectivity was evaluated.

Virus-encoded ion channels, called viroporins, are involved in viral assembly and shedding. Both influenza A virus and HIV-1 encode viroporins. SARS-CoV-2 encodes at least two viroporins, an envelope (E) protein and an open reading frame (ORF)-3a. The CoV E protein resembles the viral protein U (Vpu) of HIV-1 in terms of size, intramembrane location, ion channel activity, and role in facilitating virus release. Because of these similarities, the team determined the biological properties of the SARS-CoV-2 E protein with respect to HIV-1 to assess whether it could replace HIV-1 Vpu.

About research

In the current study, researchers evaluated HIV-1 replication in the presence of the betacoronavirus E protein.

The team first assessed the intracellular expression of the SARS-CoV-2 E protein. SARS-CoV-2 E protein was expressed in COS-7 cells using a vector marked at the C-terminus with a hemagglutinin (HA) tag. We then immunostained the E protein using an anti-HA antibody and antibodies to LAMP-1 (late endosomes/lysosomes), endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC53), and Golgin97 (trans-Golgi). did. The team then co-transfected cells with plasmids expressing the E-HA protein and vectors expressing ER-MoxGFP (RER), TGN38-GFP (TGN), or giant GFP (cis/medial Golgi), resulting in E Proteins and ER, TGN, and cis-medial Golgi. These co-transfections included fixation of cells that were permeabilized and immunostained with anti-HA antibody to detect E protein.

Additionally, the team compared the subcellular localization of SARS-CoV-2 E to SARS-CoV, Middle East Respiratory Syndrome (MERS)-CoV, and HCoV-OC43 E proteins.We then tested the amount of infectious HIV-1 or vpuHIV-1 produced to determine whether the SARS-CoV-2 E protein increased or decreased the amount. , an empty pcDNA3.1(+) vector encoding herpes simplex virus type 1 (HSV-1) glycoprotein D (gD), restrictive positive control, or gD[TMCT] It is secreted from cells, does not restrict HIV-1, and pNL4-3 was all co-transfected into HEK293 cells.

result

The study results showed that ER, ERGIC, TGN, trans-Golgi, and cis-medial Golgi markers co-localize with the E protein. However, neither the cell plasma membrane nor the lysosome harbored the E protein. This suggests that the three E proteins are similarly localized in cells as the SARS-CoV-2 E protein. The presence of the SARS-CoV-2 E protein dramatically reduced the amount of infectious HIV-1 released. SARS-CoV-2 E and gD proteins present in cell lysates were fully expressed during co-transfection as evidenced by immunoblots.Furthermore, the team found that in the absence of Vpu protein, bone marrow stromal cell protein antigen 2 (BST-2) reduced the amount of HIV-1.

The team observed that co-transfection of vectors encoding the vpu HIV-1 genome, BST-2, and the SARS-CoV-2 E protein reduced the infectious virus produced, whereas HSV-1 less so than the gD protein. Immunoblots of cell lysates for gD, BST-2, and SARS-CoV-2 E proteins showed that these proteins exhibited significant expression during co-transfection. Overall, the team noted that the SARS-CoV-2 E protein prevented both viruses from growing and could not replace the function of the Vpu protein.

Examination of the intracellular expression of these E proteins revealed that, like the SARS-CoV-2 E proteins, they localized only to the ER and Golgi sections of the cell, showing no cell surface expression. I was. gD was present but did not affect the amount of infectious HIV-1 shedding. Instead, we limited the release. SARS-CoV-2-related and SARS-CoV-related E proteins significantly reduced infectious HIV-1 shedding by 1.3% and 1.4%, respectively. Less restriction was observed for the MERS-CoV and HCoV-OC43 E proteins in nearly 37% and 16% of the pcDNA3.1(+) controls, respectively.

SARS-CoV-2 and MERS-CoV E proteins shared about 37% of their amino acid sequences, while SARS-CoV-2 and HCoV-OC43 E proteins shared about 26%. Expression of gD and E proteins was confirmed by immunoprecipitation from cell lysates obtained from restriction studies. These findings provide more information on the specificity of HIV-1 restriction.

Overall, the study results demonstrated the ability of SARS-CoV-2 and SARS-CoV E proteins to significantly prevent the development of infectious HIV-1 infection. In this study, we found that protein synthesis is most likely inhibited and that expression of the SARS-CoV-2 E protein triggers apoptosis. These findings provided evidence that viroporin of one virus can prevent another virus from infecting cells.

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